Review

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

RARA fusion genes in acute promyelocytic leukemia: a review Expert Rev. Hematol. 7(3), 347–357 (2014)

Etienne De Braekeleer1,2, Nathalie Douet-Guilbert1,3,4 and Marc De Braekeleer*1,3–5 1

Laboratoire d’Histologie, Embryologie et Cytoge´ne´tique, Faculte´ de Me´decine et des Sciences de la Sante´, Universite´ de Brest, Brest, France 2 Division of Stem Cells and Cancer, German Cancer Research Center (DKFZ) and Heidelberg Institute for Stem Cell Technology and Experimental Medicine GmbH (HI-STEM), Heidelberg, Germany 3 Institut National de la Sante´ et de la Recherche Me´dicale (INSERM), U1078, Brest, France 4 Service de Cytoge´ne´tique, Cytologie et Biologie de la Reproduction, Hoˆpital Morvan, CHRU Brest, Brest, France 5 Laboratoire de Cytoge´ne´tique, Hoˆpital Morvan, CHRU Brest, baˆtiment 5bis, 2, avenue Foch, F-29609 Brest cedex France *Author for correspondence: Tel.: +33 029 822 3694 Fax: +33 029 822 3961 [email protected]

informahealthcare.com

The t(15;17)(q24;q21), generating a PML-RARA fusion gene, is the hallmark of acute promyelocytic leukemia (APL). At present, eight other genes fusing with RARA have been identified. The resulting fusion proteins retain domains of the RARA protein allowing binding to retinoic acid response elements (RARE) and dimerization with the retinoid X receptor protein (RXRA). They participate in protein-protein interactions, associating with RXRA to form hetero-oligomeric complexes that can bind to RARE. They have a dominant-negative effect on wild-type RARA/RXRA transcriptional activity. Moreover, RARA fusion proteins can homodimerize, conferring the ability to regulate an expanded repertoire of genes normally not affected by RARA. RARA fusion proteins behave as potent transcriptional repressors of retinoic acid signalling, inducing a differentiation blockage at the promyelocyte stage which can be overcome with therapeutic doses of ATRA or arsenic trioxide. However, resistance to these two drugs is a major problem, which necessitates development of new therapies. KEYWORDS: acute promyelocytic leukemia • chromosomal aberrations • fusion genes • RARA • treatment

Acute promyelocytic leukemia (APL) accounts for 10–15% of acute myeloid leukemia cases. It results in the accumulation of abnormal, heavily granulated promyelocytes, with Auer rods and bundles. The prognosis is impaired by bleeding caused by disseminated intravascular coagulation present in most of the cases. In most of the patients, APL is sensitive to alltrans retinoic acid (ATRA) that allows DNA transcription and differentiation of the immature leukemic promyelocytes into mature granulocytes. In the late 1970s, several groups identified a translocation, t(15;17)(q22;q21), which was consistently found in APL (AML-M3 according to the FAB classification) [1,2]. Several years later, it was shown that this translocation resulted in a chimeric gene involving retinoic acid receptor a (RARA) and promyelocytic leukemia (PML) [3–6]. Therefore, this translocation is now referred as t(15;17)(q24;q21) because the PML gene is located in band 15q24. Although most of the APL cases involve a fusion between RARA and PML, other genes fusing with RARA have now been identified [7–10]. They are the subject of this review.

10.1586/17474086.2014.903794

RARA gene & protein structure

The RARA gene, spanning a 7.5 kb region at band 17q21, contains nine exons, with the start codon in exon 2 and the stop codon in exon 9 (FIGURE 1) [11]. The RARA protein has six evolutionarily conserved domains (FIGURE 2) [7]. The A and B domains contain AF-1, a ligand-independent transcriptional activation domain [12]. The C domain contains two zing finger motifs, allowing RARA to bind to retinoic acid response elements (RAREs) present in the promoters of many genes [13]. The D domain contains a cellular localization signal (hinge region). While the function of the F domain remains unknown, the E domain appears to be one of the most important domains of the protein. This domain contains a dimerization interface for the retinoid X receptor protein (RXRA) and an AF-2 ligand-dependent transcriptional activation domain [12]. RARA is a nuclear hormone receptor that heterodimerizes with RXRA to form an RA-inducible transcription activator that binds RARE. This RARA–RXRA complex is required for the promyelocyte differentiation

 2014 Informa UK Ltd

ISSN 1747-4086

347

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

Review

De Braekeleer, Douet-Guilbert & De Braekeleer

other chromosomal rearrangements such as complex translocations or insertions, RARA detectable by conventional and/or molec1 2 3 4 5 6 7 8 9 ular cytogenetics and/or RT-PCR [7,8]. Bone marrow is invaded by heavily PML granulated promyelocytes, with Auer rods 1 2 3 4 5 6 7 8 9 and bundles. The most striking clinical bcr1 bcr3 feature is hemorrhage caused by dissemibcr2 nated intravascular coagulation, which is ZBTB16 life threatening. Most of the patients 5 6 1 2 3 4 7 with t(15;17) are sensitive to ATRA at presentation but they can develop relapses NPM1 resistant to ATRA that can be treated 1 2 3 4 5 6 7 8 9 10 11 12 with arsenic trioxyde. The t(15;17) is often the only chromoSTAT5B somal anomaly seen in the neoplastic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 metaphases (70–90%). In the remaining cases, additional karyotypic changes, among which trisomy 8 is the most comBCOR mon, are present. However, since ATRA 4 5 7 6 9 8 1 2 3 10 11 12 13 14 15 was introduced as the treatment of choice, these additional chromosomal changes do not appear to influence the rate of complete remission. PRKAR1A In 1991, it was shown that t(15;17) 1A 1B 2 6 3 4A 4B 5 10 7 8 9 fused RARA to the PML gene, resulting in a 5’ PML–3’ RARA chimeric transcript [4,6]. The breakpoint occurs almost excluFIP1L1 sively in intron 2 of the RARA gene 1 15 16 (FIGURE 1) . Therefore, the RARA B–F domains are retained in the fusion protein (FIGURE 2) [17]. NABP1 The PML gene locus spans 35 kb and 5 6 1 2 3 4 7 contains nine exons coding for mRNAs of 4.6, 3.0 and 2.1 kb. However, alternaFigure 1. Schematic representation of the RARA gene and its partner genes. tive splicing generates some 20 isoforms Rectangles represent exons and arrows the breakpoint sites. of mRNAs, varying in the region coding BCOR: BCL6 corepressor; FIP1L1: Factor interacting with PAPOLA and CPSF1; NABP1: Nucleic acid-binding protein 1; NPM: Nucleophosmin; PML: Promyelocytic for the C-terminal part of the proleukemia; PRKAR: Protein kinase, cAMP-dependent, regulatory, type Ia; tein [18,19]. The protein has three imporRARA: Retinoic acid receptor a; ZBTB16: Zinc finger and BTB domain containing 16. tant functional domains. The first domain, at the C-terminal part, contains process. On the one hand, in the absence of RA (ligand), the three zinc finger like structures and is responsible for nuclear heterodimer recruits corepressors N-CoR and SMRT that com- body localization and transformation and growth suppresplex with histone deacetylases (HDACs), thus facilitating the sion [20,21]. The second domain is a coiled-coil region responsiassembly of nucleosomes and silencing several promoters, induc- ble for homodimerization of the PML protein; it is required ing transcriptional repression through changes in chromatin for transformation suppression and plays a role in nuclear body configuration [14]. On the other hand, in the presence of RA, localization [20,22]. The third domain contains a nuclear localizaAF-2 binds to coactivators, such as TIF-1 and CBP, thus disso- tion signal that is required for the activity of the protein [20,23]. ciating corepressors and HDACs and leading to disassembly of Breakpoints occur in three distinct clusters, called bcr, of the nucleosomes and gene transcriptional activation [15,16]. PML gene, leading to mRNA of different length (FIGURE 1) [17]. The long (L-) isoform mRNA is due to a break in intron RARA fusion genes 6 (bcr1) of PML and results in a PML exon 6-RARA exon PML–RARA fusion gene 3 mRNA; it accounts for up to 70% of the cases. The short The t(15;17)(q24;q21) is the hallmark of APL, being present (S-) isoform mRNA is due to a break in intron 3 (bcr3) of in about 98% of cases. In some 5% of them, patients have PML and results in a PML exon 3–RARA exon 3 mRNA; it 348

Expert Rev. Hematol. 7(3), (2014)

RARA fusion genes in APL

RARA

NH2

COOH A

B

C

D

E

F

CC

PML-RARA

POZ

ZBTB16-RARA Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

Review

O

NPM1-RARA NUMA1-RARA

CC

STAT5B-RARA

CC

BCOR-RARA

PRKAR1A-RARA

D

?

FIP1LA-RARA

NABP1-RARA

?

OB fold

?

Figure 2. Schematic representation of the RARA protein and the fusion proteins identified thus far. BCOR: BCL6 corepressor; cc: Coiled-coil domain; D: Dimerization domain; FIP1L1: Factor interacting with PAPOLA and CPSF1; NABP1: Nucleic acid-binding protein 1; NPM: Nucleophosmin; NUMA1: Nuclear mitotic apparatus protein 1; O: Oligomerization domain; OB-fold: OB-fold–nucleic acid binding domain; PML: Promyelocytic leukemia; POZ: BTB/POZ domain; PRKAR1A: Protein kinase, cAMP-dependent, regulatory, type Ia; RARA: Retinoic acid receptor a; ZBTB16: Zinc finger and BTB domain containing 16.

accounts for some 20% of the cases. The variable (V-) isoform mRNA is created by a PML breakpoint within exon 6 (bcr2), which is fused to RARA exon 3; it accounts for 10% of the cases [24–26]. However, geographical and/or ethnic variations in the frequency of the three isoforms are described, the long isoform being more prevalent among Latinos and the short isoform less frequent in China [27–31]. It has been suggested that the different domains of PML retained in the PML–RARA isoforms could correlate with hematological parameters and affect the therapeutic responsiveness, therefore influencing prognosis [26,32]. Although the results are controversial, the bcr3 type would be associated with an excess of secondary chromosomal changes and bcr3 patients would have a worse prognosis [26,33]. Also, bcr2 patients exhibit a reduced sensitivity to ATRA and have a lower 3-year diseasefree survival [32,34,35]. However, the existence of different breakpoint regions in the PML gene and the presence of alternative splicing of PML transcripts are responsible for the great heterogeneity of PML– informahealthcare.com

RARA junctions, giving rise to functionally PML–RARA proteins or out-of-frame transcripts [17,36–43]. Although these variant breakpoints and fusions have rarely been described, several isoforms skipping exon 5 have been identified [36,44,45]. Among the rare variants, those including insertion of exon 7a of the PML gene are of particular importance, as these patients are resistant to ATRA therapy [38,40,46]. ZBTB16–RARA fusion gene

In 1989, Najfeld et al. reported a male patient with APL associated with t(11;17)(q13;q12) [47]. This translocation is now referred as t(11;17)(q23;q21) because the partner gene is located in band 11q23, not in band 11q13. This translocation has now been recognized as being recurrent, but representing less than 1% of morphologic AML-M3 [9,48]. In contrast to the patients carrying a t(15;17)(q24;q21), the patients with t(11;17)(q23;q21) display an unusual morphologic spectrum between acute myelogenous with maturation (M2 in the FAB classification) and APL. Blasts have no 349

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

Review

De Braekeleer, Douet-Guilbert & De Braekeleer

intracytoplasmic Auer rods or bundles. Patients respond poorly to ATRA at induction therapy [48–50]. In 1993, it was shown that t(11;17) fused the RARA gene to the PML zinc finger (PLZF) gene [51,52]. This latter gene, also known as zinc finger protein 145, is now referred as zinc finger and BTB domain containing 16 (ZBTB16) and is located in band 11q23. The breakpoint occurs in intron 2 of the RARA gene (FIGURE 1). Therefore, the RARA B–F domains are retained in the fusion protein (FIGURE 2) [51,52]. The genomic structure of the ZBTB16 gene is still a matter of debate. ZBTB16 is a large gene spanning a 201-kb genomic sequence, with the first exon untranslated. Zhang et al. reported that the gene had six exons and five introns and at least four alternative splicing within exon 1 [53]. According to van Schothorst et al., the gene contained seven exons [54]. The gene codes a 673 amino acid protein. The N-terminal BTB/ POZ domain (encoded by a large and single exon) is responsible for transcription and growth repression and binds to N-Cor/SMRT/HDAC complex. The C-terminal part of the protein has nine zinc finger domains encoded by a series of exons of small size [51,55]. The protein is located in the nucleus, on nuclear bodies whose formation is dependent on the integrity of the BTB/POZ domain [56]. Expression of PLZF has a dramatic growth-suppressive effect accompanied by accumulation of cells in the G0/G1 compartment of the cell cycle and an increased incidence of apoptosis. Therefore, it is an important regulator of cell growth, death and differentiation [57]. All translocation breakpoints disrupt the zinc fingers in the middle of the ZBTB16 gene (FIGURE 1). Most t(11;17) APL patients have ZBTB16 breakpoints mapped to intron 3 (providing two zinc fingers to the ZBTB16–RARA protein) and rare cases to intron 4 (providing three zinc fingers to the ZBTB16– RARA protein). All the ZBTB16–RARA fusion proteins also retain the BTB/POZ domain (FIGURE 2) [50,58,59]. NPM1–RARA fusion gene

The t(5;17)(q35;q21) was first described in a girl with APL by Corey et al. [60]. Few cases have been identified as only seven cases are registered in the Mitelman database of chromosome aberrations and gene fusions in cancer [61]. Patients present with atypical morphological features (absence of Auer rods), but they respond to ATRA therapy [60,62,63]. The t(5;17) fuses the RARA gene to the nucleophosmin (NPM1) gene, resulting in a 5´NPM1–3´RARA chimeric transcript [64]. The breakpoint occurs in intron 2 of the RARA gene. The breakpoint in the NPM1 gene is located within intron 4 (FIGURE 1) [64,65]. Therefore, the RARA B–F domains are retained in the fusion protein (FIGURE 2) [64]. The NPM1 gene spans 25 kb and consists of 12 exons. Alternative splicing generates two RNA isoforms, differing in their C-terminal region [65]. The protein localizes mainly in the nucleolus and is presumed to play a role in ribosomal RNA processing or transport. It contains several functional domains, among which an oligomerization domain, two acidic domains and two nuclear localization signals [66]. 350

Given the small number of patients with t(5;17), the fusion protein has not been studied in detail. The fusion protein comprises the N-terminus of NPM1, including the oligomerization domain, and the C-terminal elements of RARA [62,63]. As for PML–RARA and PLZF–RARA, the NPM1–RARA protein has a dominant-negative activity on transcriptional activation by wild-type RARA [64]. Nuclear mitotic apparatus protein 1–RARA fusion gene

In 1996, Wells et al. reported a 6-month-old boy with APL associated with t(11;17)(q13;q21) that did not involve PML or ZBTB16 and was successfully treated with ATRA [67]. Later, they showed that this translocation generated a fusion gene involving nuclear mitotic apparatus protein 1 (NUMA1) and RARA [68]. As for the previously described fusion genes and proteins, the breakpoint occurred in intron 2 of the RARA gene, and the RARA B–F domains are retained in the protein (FIGURES 1 & 2) [68]. The NUMA1 gene spans 78 kb and consists of 27 exons. The protein has 2115 amino acids. It contains a very large coiled-coil domain responsible for oligomerization and two globular domains, one at the C-terminal region that is required for nuclear localization and mitotic spindle binding and the other at the N-terminal region whose exact function remains elusive but is required for postmitotic reassembly of nuclei [69–71]. The NUMA1–RARA fusion protein comprises the N-terminal globular and the coiled-coil domains of NUMA1 and the C-terminal elements of RARA (FIGURE 2). It forms aggregates in the nucleus where the normal NUMA partly colocalizes and does not disrupt the intracellular distribution of PML [68]. STAT5B–RARA fusion gene

In 1996, Jonveaux et al. reported a 67-year-old man with APL associated with a derivative chromosome 17 and a rearrangement of the RARA gene [72]. Later, they showed that this patient carried a fusion gene involving STAT5B and RARA [73]. At present, eight patients with APL associated with a STAT5B– RARA fusion gene have been reported [59,73–79]. The disease is unresponsive to both ATRA and arsenic trioxide (As2O3). Relapses are frequent and refractory to chemotherapy, suggesting that this subgroup of APL patients might benefit from bone marrow transplantation [79]. The STAT5B gene is located in band 17q21.2. Generation of the fusion gene can result from a translocation, t(17;17) (q21.2;q21.2), or a cryptic deletion, del(17)(q21.2q21.2). In fact, no recurrent chromosomal abnormality has been associated yet with this fusion [79]. The STAT5B gene contains 19 exons; it has two alternate first exons, 1a and 1b, separated by about 1.3 kb. The ATG start codon is in exon 2 [80]. The STAT5B protein is a member of the STAT family of transcription factors. It contains several conserved domains: the coiled-coil domain, the DNA binding domain, the SH2 domain and the carboxy-terminal transactivation domain [81]. Upon phosphorylation by receptor or nonreceptor tyrosine Expert Rev. Hematol. 7(3), (2014)

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

RARA fusion genes in APL

kinases, STAT5b forms homodimers or heterodimers that translocate from the cytoplasm to the nucleus where they act as transcription activators [82]. In all cases, thus far described, STAT5B exon 15 is fused to RARA exon 3 (FIGURE 1). Therefore, the STAT5B–RARA protein retains the N-terminal oligomerization domain, the coiled-coil domain, the DNA-binding domain and a truncated SH2 domain of STAT5b as well as the RARA B–F domains (FIGURE 2) [79]. STAT5B–RARA binds RARE as a homodimer and RXRA as a heterodimer. It has a dominant-negative activity on transcriptional activation by wild-type RARA [83]. BCL6 corepressor–RARA fusion gene

A t(X;17)(p11.2;q21) generating an in-frame fusion between exon 12 of the BCL6 corepressor (BCOR) gene and exon 3 of RARA was identified in a 45-year-old man diagnosed with variant APL (FIGURE 1) [84]. Although the patient responded to ATRA therapy, the patient relapsed twice within 41 months after diagnosis before allogeneic transplantation was performed. The blasts showed no typical Auer bodies and faggot cells but round inclusions and rectangular cytoplasmic bodies. They were more granular than those of AML M2, but less granular than the classical t(15;17) APL. The BCOR gene contains 15 exons and is subjected to mutations in about 4% of acute myeloid leukemia associated with a normal karyotype [85]. The protein encoded by this gene is a corepressor of BCL6, interacting with its POZ domain and several HDAC to increase BCL6 transcriptional repression [86]. The BCOR protein contains a BCL6 and a AF9-binding domain and three ankyrin repeats, but no coiled coil or oligomerization domains have been identified yet. The BCOR–RARA protein retains both binding domains and ankyrin repeats of BCOR and the RARA B–F domains (FIGURE 2). Although the domain accounting for self-association (homodimerization and/or homo-oligomerization domains) in BCOR–RARA fusion protein remains unknown, BCOR and BCOR–RARA self-associate as in the other fusion proteins. Furthermore, BCOR–RARA acts in a dominant-negative manner on RARA transcriptional activation [84]. Protein kinase, cAMP-dependent, regulatory, type Ia-RARA fusion gene

A fusion between the protein kinase, cAMP-dependent, regulatory, type Ia (PRKAR1A) gene and RARA was identified by RT-PCR in a 66-year-old man diagnosed with variant APL. Cytogenetic analysis had revealed a normal 46, XY karyotype but FISH with a RARA break-apart probe had shown a split signal. The hypercellular marrow contained 88% hypergranular promyelocytes without Auer bodies; faggot cells were absent. The patient responded to ATRA therapy and was in complete remission 2 years after diagnosis. Two transcripts were identified: a short out-of-frame transcript and a longer in-frame transcript joining PRKAR1A exon 3 to RARA exon 3 (FIGURE 1) [87]. The PRKAR1A gene, located in band 17q24.2, contains 12 exons, of which 10 are coding and 2 (exons 1A and 1B) are informahealthcare.com

Review

noncoding, leading to 2 transcripts by alternative splicing. The PRKAR1A protein, which is localized exclusively to the cytoplasm, contains a dimerization domain at the N-terminus, a hinge region and two c-AMP-binding domains at the C-terminus [88]. PRKAR1A is a critical component of type I PKA, the main mediator of cAMP signaling [89]. Phosphorylation mediated by the cAMP/PKA signaling pathway is involved in the regulation of metabolism, cell proliferation, differentiation and apoptosis [89]. The PRKAR1A–RARA fusion protein consists of the dimerization domain at the N-terminus of PRKAR1A along with the RARA B–F domains, as in the other fusion proteins (FIGURE 2) [87]. PRKAR1A–RARA binds RARE as either a homodimer or as a heterodimer with RXRA and localizes within the nucleus in a pattern that resembles wild-type RARA [90]. Factor interacting with PAPOLA & cleavage and polyadenylation specificity factor 1–RARA fusion gene

Two patients carrying a t(4;17)(q12;q21) have now been reported in the literature. Interestingly, one patient, a 20-month-old boy, was diagnosed with juvenile myelomonocytic leukemia, whereas the second patient, a 90-year-old woman, had APL [91,92]. In this latter patient, oral administration of ATRA led to a complete remission [92]. In both cases, the t(4;17)(q12;q21) generated an in-frame fusion between exon 15 of the (factor interacting with PAPOLA and cleavage and polyadenylation specificity factor 1 [FIP1L1]) gene and exon 3 of RARA (FIGURE 1) [91,92]. The FIP1L1 gene was first described in idiopathic hypereosinophilic syndrome in which it is fused to the PDGF receptora (PDGFRA) gene [93,94]. The gene would contain 20 exons, several of them being alternative exons. It encodes a subunit of the cleavage and polyadenylation specificity factor complex that polyadenylates the 3’-end of mRNA precursors [95]. The FIP1L1–RARA chimeric protein contains the 428 Nterminus amino acids of FIP1L1 (representing about threefourth of the protein, depending upon the mRNA isoform) and the RARA B–F domains (FIGURE 2). Although its function has not been analyzed yet, the FIP1L1–RARA protein forms homodimers and represses retinoic acid-dependent transcriptional activity [92]. It remains to be understood why FIP1L1–RARA can cause two different phenotypes (juvenile myelomonocytic leukemia and APL). It should be noted that NPM1 is also involved in 3´-end mRNA processing and that, in the transgenic mice, leukemic cells induced by NPM1–RARA resembled monoblasts [96,97]. This could establish the link between both fusion proteins. Nucleic acid-binding protein 1–RARA (oligonucleotide/ oligosaccharide-binding fold-containing protein 2A–RARA) fusion gene

This 59-year-old man was diagnosed with variant APL. Bone marrow was invaded by abnormal promyelocytes with bi-lobed or sharply indented nucleus and microgranulated cytoplasm, 351

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

Review

De Braekeleer, Douet-Guilbert & De Braekeleer

some having Auer rods. Oral administration of ATRA led to a complete remission [98]. Cytogenetic analysis showed a der(2)t (2;17)(q32;q21) with a split signal of the RARA break-apart probe. RT-PCR revealed an in-frame fusion between exon 5 of the nucleic acid-binding protein 1 (NABP1) gene (identified in the original paper as oligonucleotide/oligosaccharide-binding fold-containing protein 2A) and exon 3 of RARA (FIGURE 1) [98]. The NABP1 gene, located in band 2q32.3, consists of seven exons spanning 10.4 kb. It encodes a protein that contains an OB-fold–nucleic acid-binding domain at the N-terminus and is a component of the heterotrimeric complex sensor of singlestranded DNA [99]. The NABP1 protein plays an important role in the cellular response to DNA damage, including cellcycle checkpoint activation, recombinational repair and is involved in the maintenance of genome stability [100,101]. The NABP1–RARA fusion protein contains the N-terminus part of NABP1, including the OB-fold–nucleic acid-binding domain, and the RARA B–F domains (FIGURE 2). Retention of the OB-fold provides the possibility of dimerization of the NABP1–RARA fusion protein, therefore repressing retinoic acid-dependent transcriptional activity [98]. RARA fusion involving an unknown gene on 5q

In 1995, Brunel et al. reported a 76-year-old female with APL showing unusual dysgranulopoiesis and some AML-M2 features associated with der(5)t(5;17)(q?;q12–21). The patient received ATRA but quickly developed an ATRA syndrome; she died 14 days after diagnosis [62]. Molecular analysis showed a rearrangement of the RARA gene, with a breakpoint in the second intron and no involvement of either PML or PLZF [62,102]. Further in vitro studies showed an atypical response to ATRA that was not considered positive by the authors [102]. Treatment: how effective?

RARA fusion proteins behave as potent transcriptional repressors of retinoic acid signaling, inducing a differentiation blockage at the promyelocyte stage. This repression is the consequence of an enhanced binding of fusion proteins to corepressors that cannot be reversed by physiological doses of ATRA. However, therapeutic doses of ATRA associated with chemotherapeutic drug regimen (such as anthracycline-Ara-C) can trigger granulocytic differentiation in most of the APL patients [103,104]. Two classes of patients can be recognized: those responsive to ATRA who represent more than 99% of the cases and those carrying a ZBTB16–RARA or STAT5B– RARA fusion gene who are nonresponsive to ATRA [50,79]. PML–RARA and ZBTB16–RARA repress a number of common target genes involved in the regulation of granulocytic differentiation and cell survival and death. Park et al. tried to identify those genes that determine ATRA sensitivity or resistance. They found that several genes essential for cell survival and apoptosis (e.g., HOXA1, TNFR2), known to be downregulated in PML–RARA and ZBTB16–RARA cells, were upregulated following ATRA therapy in PML–RARA cells solely. Other genes, such as BCL2, were downregulated following 352

ATRA therapy in PML–RARA cells, but not in ZBTB16– RARA cells [105]. Although ATRA is very effective as first-line therapy, secondary, acquired ATRA resistance occurs in many patients. ATRA resistance is heterogeneous and multifactorial. Two major mechanisms have been identified, that is, hypercatabolic response or cellular events limiting ATRA uptake or increasing its catabolism and mutations in the RARA ligand-binding domain of the fusion protein [106–108]. As2O3 has also proven efficacy in APL treatment even for patients who relapsed after ATRA-induced clinical remission [103,109,110]. In contrast to ATRA, which induces differentiation, As2O3 has a dose-dependent effect. Lower concentrations (0.1–0.5 mmol/l) induce partial differentiation of APL cells, whereas higher concentrations (0.5–2.0 m mol/l) induce apoptosis without differentiation [111–113]. However, as for ATRA, patients carrying a ZBTB16–RARA or STAT5B–RARA fusion gene are naturally resistant to As2O3 [79,114]. Expert commentary

The RARA fusion partner genes belong to different classes and lack a functional commonality. Although the N-terminus part of the partner proteins can influence the cytomorphological features of the leukemic cells and the characteristics of the disease [97], all the fusion proteins can participate in protein– protein interactions, associating with RXRA to form higher molecular weight hetero-oligomeric complexes that can bind to RARE [7,115,116]. They have a dominant-negative effect on wildtype RARA/RXRA transcriptional activity [7]. Moreover, RARA fusion proteins can homodimerize, conferring the ability to regulate an expanded repertoire of genes normally not affected by RARA [117–119]. The contribution of the partner proteins is not limited to their ability to dimerize. These proteins have important functions whose activities could be potentially blocked by the RARA fusion proteins [120]. Indeed, PML has tumor growth suppressor properties, NPM1 and NABP1 have key roles in genomic stability and NUMA1 is an essential component of the nuclear matrix. Other partners have important roles in cell proliferation control (ZBTB16, STAT5B, BCOR and PRKAR1A). RARA fusion proteins have a dual action, activating transcription of a number of genes and repressing transcription of others. PML–RARA and ZBTB16–RARA repress several myeloid transcriptional regulators and DNA repair genes and activate the Wnt signaling and Jagged1/Notch pathways, leading to increased stem cell renewal [121,122]. However, although no comparative gene expression profiling has been performed between PML–RARA and ZBTB16–RARA samples, available data appear to show differences in their expression signature [123–127]. Many of the genes targeted by retinoid acid are known to play key roles in regulating myeloid cell proliferation and differentiation. Therefore, it is likely that inhibition of their expression by RARA fusion proteins will lead to differentiation Expert Rev. Hematol. 7(3), (2014)

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

RARA fusion genes in APL

blockage. This could be achieved by interfering with RAdependent and -independent myeloid differentiation pathways through a variety of target genes [128,129]. However, data collected from transgenic mice showed that RARA fusion proteins caused leukemia only after a long latent period. Indeed, on the one hand, the expression profile of nontransformed murine cells expressing PML–RARA is similar to that of wild-type promyelocytes. On the other hand, the expression profiles of transformed cells are different from that of nontransformed cells expressing PML–RARA, suggesting that secondary genetic changes are necessary for progression to leukemia [118,130]. Five-year view

Elucidation of the molecular mechanisms underlying the differentiation block in APL associated with PML–RARA gene and its release by ATRA is still an important challenge. Indeed, differences in ATRA responsiveness exist between the several isoforms of the fusion gene. Patients with an isoform including insertion of exon 7a of the PML gene are resistant to ATRA therapy [38,40,46]. More recently, it was shown that the short isoform lacking exons 5 and 6 of the long (L)-type PML–RARA gene conferred ATRA resistance [131]. Furthermore, several miRNAs, such as miR-15b, miR-223 and miR-342, which are repressed by the PML–RARA gene, are upregulated after ATRA therapy. On the contrary, other miRNAs, as miR-181a and miR-181b, which are upregulated by PML–RARA, are downregulated following ATRA treatment [132,133]. In fact, ATRA treatment modulates a small

Review

number of miRNAs, most of which having confirmed targets involved in hematopoietic growth, differentiation and apoptosis including HOX genes [134]. Because, on the one hand, RARA fusion proteins can transcriptionally repress several miRNAs and, on the other hand, ATRA and As2O3 restore their expression, miRNAs could provide new therapeutic targets in APL [114,132,135,136]. Because a high rate of patients relapse and become resistant to ATRA and As2O3, new therapeutic strategies need to be explored. As RXRA recruitment appears to be the cornerstone of the transforming potential of RARA fusion proteins and required for full execution of the transcriptional and transformation programs of the fusion proteins, targeting RXRA with agonists could be a promising treatment perspective. Furthermore, as recruitment of HDACs by RARA fusion proteins plays a key role in mediating the differentiation block, HDAC inhibitors could also be of therapeutic value. Drugs that decrease expression and/or activity of DNA methyltransferases could constitute another approach by inducing specific changes on the chromatin state at loci of genes targeted by retinoid acid. Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.

Key issues • Acute promyelocytic leukemia accounts for 10–15% of acute myeloid leukemia. • The promyelocytic leukemia–retinoic acid receptor a (RARA) chimeric gene, resulting from the t(15;17)(q24;q21), is identified in about 98% of the patients. • Eight other RARA partner genes have been identified in acute promyelocytic leukemia. • In all chimeric genes, the breakpoint occurs in intron 2 of the RARA gene. • All chimeric genes have a dominant-negative effect on wild-type RARA transcriptional activity. • All-trans retinoic acid and arsenic trioxide are very effective drugs but patients may be resistant or develop resistance. • Development of new therapies is much needed.

References

3.

Papers of special note have been highlighted as: • of interest •• of considerable interest 1.

2.

Rowley JD, Golomb HM, Vardiman J, et al. Further evidence for a non-random chromosomal abnormality in acute promyelocytic leukemia. Int J Cancer 1977;20:869-72 Van den Berghe H, Louwagie A, Broeckaert-Van Orshoven A, et al. Chromosome abnormalities in acute promyelocytic leukemia (APL). Cancer 1979;43:558-62

informahealthcare.com

4.

5.

Borrow J, Goddard AD, Sheer D, Solomon E. Molecular analysis of acute promyelocytic leukemia breakpoint cluster region on chromosome 17. Science 1990;249:1577-80 de The´ H, Chomienne C, Lanotte M, et al. The t(15;17) translocation of acute promyelocytic leukaemia fuses the retinoic acid receptor alpha gene to a novel transcribed locus. Nature 1990;347:558-61 Alcalay M, Zangrilli D, Pandolfi PP, et al. Translocation breakpoint of acute promyelocytic leukemia lies within the

retinoic acid receptor alpha locus. Proc Natl Acad Sci USA 1991;88:1977-81 6.

Kakizuka A, Miller WH Jr, Umesono K, et al. Chromosomal translocation t(15;17) in human acute promyelocytic leukemia fuses RAR alpha with a novel putative transcription factor, PML. Cell 1991;66: 663-74

7.

Melnick A, Licht JD. Deconstructing a disease: RARalpha, its fusion partners, and their roles in the pathogenesis of acute

353

Review

De Braekeleer, Douet-Guilbert & De Braekeleer

promyelocytic leukemia. Blood 1999;93: 3167-215 ••

A key study on the molecular aspects of acute promyelocytic leukemia (APL).

8.

Zelent A, Guidez F, Melnick A, et al. Translocations of the RARalpha gene in acute promyelocytic leukemia. Oncogene 2001;20:7186-203

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

9.

Chen Z, Tong JH, Dong S, et al. Retinoic acid regulatory pathways, chromosomal translocations, and acute promyelocytic leukemia. Genes Chromosomes Cancer 1996;15:147-56

10.

Grimwade D. The pathogenesis of acute promyelocytic leukaemia: evaluation of the role of molecular diagnosis and monitoring in the management of the disease. Br J Haematol 1999;106:591-613

11.

Hjalt TA, Murray JC. Genomic structure of the human retinoic acid receptor-alpha1 gene. Mamm Genome 1999;10:528-9

12.

Nagpal S, Friant S, Nakshatri H, Chambon P. RARs and RXRs: evidence for two autonomous transactivation functions (AF-1 and AF-2) and heterodimerization in vivo. EMBO J 1993;12:2349-60

13.

Gudas LJ. Retinoids and vertebrate development. J Biol Chem 1994;269: 15399-402

14.

Pazin MJ, Kadonaga JT. What’s up and down with histone deacetylation and transcription? Cell 1997;89:325-8

15.

vom Baur E, Zechel C, Heery D, et al. Differential ligand-dependent interactions between the AF-2 activating domain of nuclear receptors and the putative transcriptional intermediary factors mSUG1 and TIF1. EMBO J 1996;15: 110-24

16.

17.

Kamei Y, Xu L, Heinzel T, et al. A CBP integrator complex mediates transcriptional activation and AP-1 inhibition by nuclear receptors. Cell 1996;85:403-14 Pandolfi PP, Alcalay M, Fagioli M, et al. Genomic variability and alternative splicing generate multiple PML/RAR alpha transcripts that encode aberrant PML proteins and PML/RAR alpha isoforms in acute promyelocytic leukaemia. EMBO J 1992;11:1397-407

18.

Grignani F, Fagioli M, Alcalay M, et al. Acute promyelocytic leukemia: from genetics to treatment. Blood 1994;83:10-25

19.

Fagioli M, Alcalay M, Pandolfi PP, et al. Alternative splicing of PML transcripts predicts coexpression of several

354

by combined all-trans retinoic acid and idarubicin (AIDA) therapy. Gruppo Italiano-Malattie Ematologiche Maligne dell’Adulto and Associazione Italiana di Ematologia ed Oncologia Pediatrica Cooperative Groups. Blood 1997;90: 1014-21

carboxy-terminally different protein isoforms. Oncogene 1992;7:1083-91 20.

Le XF, Yang P, Chang KS. Analysis of the growth and transformation suppressor domains of promyelocytic leukemia gene, PML. J Biol Chem 1996;271:130-5

21.

Borden KL, CampbellDwyer EJ, Salvato MS. The promyelocytic leukemia protein PML has a pro-apoptotic activity mediated through its RING domain. FEBS Lett 1997;418:30-4

22.

23.

24.

25.

26.

27.

28.

29.

30.

Grignani F, Testa U, Rogaia D, et al. Effects on differentiation by the promyelocytic leukemia PML/RARalpha protein depend on the fusion of the PML protein dimerization and RARalpha DNA binding domains. EMBO J 1996;15: 4949-58

Dong S, Geng JP, Tong JH, et al. Breakpoint clusters of the PML gene in acute promyelocytic leukemia: primary structure of the reciprocal products of the PML-RARA gene in a patient with t (15;17). Genes Chromosomes Cancer 1993;6:133-9

31.

Kastner P, Perez A, Lutz Y, et al. Structure, localization and transcriptional properties of two classes of retinoic acid receptor alpha fusion proteins in acute promyelocytic leukemia (APL): structural similarities with a new family of oncoproteins. EMBO J 1992;11:629-42

Burnett AK, Grimwade D, Solomon E, et al. Presenting white blood cell count and kinetics of molecular remission predict prognosis in acute promyelocytic leukemia treated with all-trans retinoic acid: result of the Randomized MRC Trial. Blood 1999;93:4131-43

32.

Gonzalez M, Barragan E, Bolufer P, et al. Pretreatment characteristics and clinical outcome of acute promyelocytic leukaemia patients according to the PML-RAR alpha isoforms: a study of the PETHEMA group. Br J Haematol 2001;114:99-103

•

An interesting study on how different promyelocytic leukemia–retinoic acid receptor a isoforms could affect biological and clinical aspects of APL.

33.

Huang W, Sun GL, Li XS, et al. Acute promyelocytic leukemia: clinical relevance of two major PML-RAR alpha isoforms and detection of minimal residual disease by retrotranscriptase/polymerase chain reaction to predict relapse. Blood 1993;82:1264-9

34.

Gallagher RE, Li YP, Rao S, et al. Characterization of acute promyelocytic leukemia cases with PML-RAR alpha break/ fusion sites in PML exon 6: identification of a subgroup with decreased in vitro responsiveness to all-trans retinoic acid. Blood 1995;86:1540-7

35.

Grimwade D, Howe K, Langabeer S, et al. Establishing the presence of the t(15;17) in suspected acute promyelocytic leukaemia: cytogenetic, molecular and PML immunofluorescence assessment of patients entered into the M.R.C. ATRA trial. M.R. C. Adult Leukaemia Working Party. Br J Haematol 1996;94:557-73

36.

Ismail S, Ababneh N, Awidi A. Identification of atypical PML-RARA breakpoint in a patient with acute promyelocytic leukemia. Acta Haematol 2007;118:183-7

37.

Park TS, Lee ST, Kim JS, et al. Acute promyelocytic leukemia in early pregnancy

Fenaux P, Chomienne C. Biology and treatment of acute promyelocytic leukemia. Curr Opin Oncol 1996;8:3-12 Slack JL, Arthur DC, Lawrence D, et al. Secondary cytogenetic changes in acute promyelocytic leukemia–prognostic importance in patients treated with chemotherapy alone and association with the intron 3 breakpoint of the PML gene: a Cancer and Leukemia Group B study. J Clin Oncol 1997;15:1786-95 Gallagher RE, Willman CL, Slack JL, et al. Association of PML-RAR alpha fusion mRNA type with pretreatment hematologic characteristics but not treatment outcome in acute promyelocytic leukemia: an intergroup molecular study. Blood 1997;90:1656-63 Douer D, Santillana S, Ramezani L, et al. Acute promyelocytic leukaemia in patients originating in Latin America is associated with an increased frequency of the bcr1 subtype of the PML/RARalpha fusion gene. Br J Haematol 2003;122:563-70 Ruiz-Arguelles GJ, Garces-Eisele J, Reyes-Nunez V, et al. More on geographic hematology: the breakpoint cluster regions of the PML/RARalpha fusion gene in Mexican Mestizo patients with promyelocytic leukemia are different from those in Caucasians. Leuk Lymphoma 2004;45:1365-8 Mandelli F, Diverio D, Avvisati G, et al. Molecular remission in PML/RAR alpha-positive acute promyelocytic leukemia

Expert Rev. Hematol. 7(3), (2014)

RARA fusion genes in APL

with translocation t(15;17) and variant PML/RARA fusion transcripts. Cancer Genet Cytogenet 2009;188:48-51

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

38.

39.

40.

41.

42.

43.

44.

45.

Park TS, Kim JS, Song J, et al. Acute promyelocytic leukemia with insertion of PML exon 7a and partial deletion of exon 3 of RARA: a novel variant transcript related to aggressive course and not detected with real-time polymerase chain reaction analysis. Cancer Genet Cytogenet 2009;188: 103-7 Kim MJ, Cho SY, Kim MH, et al. FISH-negative cryptic PML-RARA rearrangement detected by long-distance polymerase chain reaction and sequencing analyses: a case study and review of the literature. Cancer Genet Cytogenet 2010;203:278-83 Chillon MC, Gonzalez M, Garcia-Sanz R, et al. Two new 3’ PML breakpoints in t (15;17)(q22;q21)-positive acute promyelocytic leukemia. Genes Chromosomes Cancer 2000;27:35-43 Reiter A, Saussele S, Grimwade D, et al. Genomic anatomy of the specific reciprocal translocation t(15;17) in acute promyelocytic leukemia. Genes Chromosomes Cancer 2003;36:175-88 Ashur-Fabian O, Trakhtenbrot L, Dominissini D, et al. The presence of a single PML-RARA isoform lacking exon 5 in FISH-negative APL samples. Leukemia 2008;22:200-3

acute promyelocytic leukemia distinguishes cases with underlying PLZF/RARA gene rearrangements. Blood 2000;96:1287-96 49.

50.

51.

52.

53.

Jeziskova I, Razga F, Gazdova J, et al. A case of a novel PML/RARA short fusion transcript with truncated transcription variant 2 of the RARA gene. Mol Diagn Ther 2010;14:113-17 de The´ H, Lavau C, Marchio A, et al. The PML-RAR alpha fusion mRNA generated by the t(15;17) translocation in acute promyelocytic leukemia encodes a functionally altered RAR. Cell 1991;66: 675-84 Jensen K, Shiels C, Freemont PS. PML protein isoforms and the RBCC/TRIM motif. Oncogene 2001;20:7223-33

Grimwade D, Biondi A, Mozziconacci MJ, et al. Characterization of acute promyelocytic leukemia cases lacking the classic t(15;17): results of the European Working Party. Groupe Francais de Cytogenetique Hematologique, Groupe de Francais d’Hematologie Cellulaire, UK Cancer Cytogenetics Group and BIOMED 1 European Community-Concerted Action "Molecular Cytogenetic Diagnosis in Haematological Malignancies". Blood 2000;96:1297-308 Licht JD, Chomienne C, Goy A, et al. Clinical and molecular characterization of a rare syndrome of acute promyelocytic leukemia associated with translocation (11;17). Blood 1995;85:1083-94 Chen SJ, Zelent A, Tong JH, et al. Rearrangements of the retinoic acid receptor alpha and promyelocytic leukemia zinc finger genes resulting from t(11;17)(q23; q21) in a patient with acute promyelocytic leukemia. J Clin Invest 1993;91:2260-7 Chen Z, Brand NJ, Chen A, et al. Fusion between a novel Kruppel-like zinc finger gene and the retinoic acid receptor-alpha locus due to a variant t(11;17) translocation associated with acute promyelocytic leukaemia. EMBO J 1993;12:1161-7 Zhang T, Xiong H, Kan LX, et al. Genomic sequence, structural organization, molecular evolution, and aberrant rearrangement of promyelocytic leukemia zinc finger gene. Proc Natl Acad Sci USA 1999;96:11422-7

54.

van Schothorst EM, Prins DE, Baysal BE, et al. Genomic structure of the human PLZF gene. Gene 1999;236:21-4

55.

Baysal BE, van Schothorst EM, Farr JE, et al. A high-resolution STS, EST, and gene-based physical map of the hereditary paraganglioma region on chromosome 11q23. Genomics 1997;44:214-21

56.

Koken MH, Reid A, Quignon F, et al. Leukemia-associated retinoic acid receptor alpha fusion partners, PML and PLZF, heterodimerize and colocalize to nuclear bodies. Proc Natl Acad Sci USA 1997;94: 10255-60

46.

Barragan E, Bolufer P, Martin G, et al. Identification of two atypical PML-RAR (alpha) transcripts in two patients with acute promyelocytic leukemia. Leuk Res 2002;26:439-42

47.

Najfeld V, Scalise A, Troy K. A new variant translocation 11;17 in a patient with acute promyelocytic leukemia together with t (7;12). Cancer Genet Cytogenet 1989;43: 103-8

57.

Shaknovich R, Yeyati PL, Ivins S, et al. The promyelocytic leukemia zinc finger protein affects myeloid cell growth, differentiation, and apoptosis. Mol Cell Biol 1998;18: 5533-45

48.

Sainty D, Liso V, Cantu-Rajnoldi A, et al. A new morphologic classification system for

58.

Reid A, Gould A, Brand N, et al. Leukemia translocation gene, PLZF, is expressed with

informahealthcare.com

Review

a speckled nuclear pattern in early hematopoietic progenitors. Blood 1995;86: 4544-52 59.

Jovanovic JV, Rennie K, Culligan D, et al. Development of real-time quantitative polymerase chain reaction assays to track treatment response in retinoid resistant acute promyelocytic leukemia. Front Oncol 2011;1:35

60.

Corey SJ, Locker J, Oliveri DR, et al. A non-classical translocation involving 17q12 (retinoic acid receptor alpha) in acute promyelocytic leukemia (APML) with atypical features. Leukemia 1994;8:1350-3

61.

Mitelman database of chromosome aberrations and gene fusions in cancer. Available from: http://cgap.nci.nih.gov/ Chromosomes/Mitelman

62.

Brunel V, Sainty D, Carbuccia N, et al. Unbalanced translocation t(5;17) in an typical acute promyelocytic leukemia. Genes Chromosomes Cancer 1995;14:307-12

63.

Redner RL, Corey SJ, Rush EA. Differentiation of t(5;17) variant acute promyelocytic leukemic blasts by all-trans retinoic acid. Leukemia 1997;11:1014-16

64.

Redner RL, Rush EA, Faas S, et al. The t (5;17) variant of acute promyelocytic leukemia expresses a nucleophosmin-retinoic acid receptor fusion. Blood 1996;87:882-6

65.

Chan PK, Chan FY, Morris SW, Xie Z. Isolation and characterization of the human nucleophosmin/B23 (NPM) gene: identification of the YY1 binding site at the 5’ enhancer region. Nucleic Acids Res 1997;25:1225-32

66.

Chang JH, Dumbar TS, Olson MO. cDNA and deduced primary structure of rat protein B23, a nucleolar protein containing highly conserved sequences. J Biol Chem 1988;263:12824-7

67.

Wells RA, Hummel JL, De Koven A, et al. A new variant translocation in acute promyelocytic leukaemia: molecular characterization and clinical correlation. Leukemia 1996;10:735-40

68.

Wells RA, Catzavelos C, Kamel-Reid S. Fusion of retinoic acid receptor alpha to NuMA, the nuclear mitotic apparatus protein, by a variant translocation in acute promyelocytic leukaemia. Nat Genet 1997;17:109-13

69.

Yang CH, Lambie EJ, Snyder M. NuMA: an unusually long coiled-coil related protein in the mammalian nucleus. J Cell Biol 1992;116:1303-17

70.

Compton DA, Szilak I, Cleveland DW. Primary structure of NuMA, an intranuclear protein that defines a novel pathway for

355

Review

De Braekeleer, Douet-Guilbert & De Braekeleer

segregation of proteins at mitosis. J Cell Biol 1992;116:1395-408 71.

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

72.

73.

74.

75.

76.

77.

78.

79.

80.

Cleveland DW. NuMA: a protein involved in nuclear structure, spindle assembly, and nuclear re-formation. Trends Cell Biol 1995;5:60-4 Jonveaux P, Le Coniat M, Derre J, et al. Chromosome microdissection in leukemia: a powerful tool for the analysis of complex chromosomal rearrangements. Genes Chromosomes Cancer 1996;15:26-33 Arnould C, Philippe C, Bourdon V, et al. The signal transducer and activator of transcription STAT5b gene is a new partner of retinoic acid receptor alpha in acute promyelocytic-like leukaemia. Hum Mol Genet 1999;8:1741-9 Gallagher RE, Mak S, Paietta E, et al. Identification of a second acute promyelocytic leukemia (APL) patient with the STAT5b-RARa fusion gene among PML-RARa-negative Eastern Cooperative Oncology Group (ECOG) APL protocol registrants. Blood 2004;104:821A Kusakabe M, Suzukawa K, Nanmoku T, et al. Detection of the STAT5B-RARA fusion transcript in acute promyelocytic leukemia with the normal chromosome 17 on G-banding. Eur J Haematol 2008;80:444-7 Iwanaga E, Nakamura M, Nanri T, et al. Acute promyelocytic leukemia harboring a STAT5B-RARA fusion gene and a G596V missense mutation in the STAT5B SH2 domain of the STAT5B-RARA. Eur J Haematol 2009;83:499-501 Qiao C, Zhang SJ, Chen LJ, et al. Identification of the STAT5B-RARalpha fusion transcript in an acute promyelocytic leukemia patient without FLT3, NPM1, c-Kit and C/EBPalpha mutation. Eur J Haematol 2011;86:442-6 Chen H, Pan J, Yao L, et al. Acute promyelocytic leukemia with a STAT5b-RARalpha fusion transcript defined by array-CGH, FISH, and RT-PCR. Cancer Genet 2012;205:327-31 Strehl S, Konig M, Boztug H, et al. All-trans retinoic acid and arsenic trioxide resistance of acute promyelocytic leukemia with the variant STAT5B-RARA fusion gene. Leukemia 2013;27:1606-10 Ambrosio R, Fimiani G, Monfregola J, et al. The structure of human STAT5A and B genes reveals two regions of nearly identical sequence and an alternative tissue specific STAT5B promoter. Gene 2002;285: 311-18

356

81.

Bowman T, Garcia R, Turkson J, Jove R. STATs in oncogenesis. Oncogene 2000;19: 2474-88

82.

Levy DE, Darnell JE Jr. Stats: transcriptional control and biological impact. Nat Rev Mol Cell Biol 2002;3: 651-62

83.

Dong S, Tweardy DJ. Interactions of STAT5b-RARa, a novel acute promyelocytic leukemia fusion protein, with retinoic acid receptor and STAT3 signaling pathways. Blood 2002;99:2637-46

84.

85.

86.

87.

88.

89.

90.

Yamamoto Y, Tsuzuki S, Tsuzuki M, et al. BCOR as a novel fusion partner of retinoic acid receptor alpha in a t(X;17)(p11;q12) variant of acute promyelocytic leukemia. Blood 2010;116:4274-83 Grossmann V, Tiacci E, Holmes AB, et al. Whole-exome sequencing identifies somatic mutations of BCOR in acute myeloid leukemia with normal karyotype. Blood 2011;118:6153-63 Huynh KD, Fischle W, Verdin E, Bardwell VJ. BCoR, a novel corepressor involved in BCL-6 repression. Genes Dev 2000;14:1810-23 Catalano A, Dawson MA, Somana K, et al. The PRKAR1A gene is fused to RARA in a new variant acute promyelocytic leukemia. Blood 2007;110:4073-6 Solberg R, Sandberg M, Natarajan V, et al. The human gene for the regulatory subunit RI alpha of cyclic adenosine 3’, 5’-monophosphate-dependent protein kinase: two distinct promoters provide differential regulation of alternately spliced messenger ribonucleic acids. Endocrinology 1997;138:169-81 Boshart M, Weih F, Nichols M, Schutz G. The tissue-specific extinguisher locus TSE1 encodes a regulatory subunit of cAMP-dependent protein kinase. Cell 1991;66:849-59 Qiu JJ, Lu X, Zeisig BB, et al. Leukemic transformation by the APL fusion protein PRKAR1A-RAR{alpha} critically depends on recruitment of RXR{alpha}. Blood 2010;115:643-52

91.

Buijs A, Bruin M. Fusion of FIP1L1 and RARA as a result of a novel t(4;17)(q12; q21) in a case of juvenile myelomonocytic leukemia. Leukemia 2007;21:1104-8

92.

Kondo T, Mori A, Darmanin S, et al. The seventh pathogenic fusion gene FIP1L1-RARA was isolated from a t(4;17)positive acute promyelocytic leukemia. Haematologica 2008;93:1414-16

93.

Griffin JH, Leung J, Bruner RJ, et al. Discovery of a fusion kinase in EOL-1 cells

and idiopathic hypereosinophilic syndrome. Proc Natl Acad Sci USA 2003;100:7830-5 94.

Cools J, DeAngelo DJ, Gotlib J, et al. A tyrosine kinase created by fusion of the PDGFRA and FIP1L1 genes as a therapeutic target of imatinib in idiopathic hypereosinophilic syndrome. N Engl J Med 2003;348:1201-14

95.

Kaufmann I, Martin G, Friedlein A, et al. Human Fip1 is a subunit of CPSF that binds to U-rich RNA elements and stimulates poly(A) polymerase. EMBO J 2004;23:616-26

96.

Palaniswamy V, Moraes KC, Wilusz CJ, Wilusz J. Nucleophosmin is selectively deposited on mRNA during polyadenylation. Nat Struct Mol Biol 2006;13:429-35

97.

Rego EM, Ruggero D, Tribioli C, et al. Leukemia with distinct phenotypes in transgenic mice expressing PML/RAR alpha, PLZF/RAR alpha or NPM/RAR alpha. Oncogene 2006;25:1974-9

98.

Won D, Shin SY, Park CJ, et al. OBFC2A/ RARA: a novel fusion gene in variant acute promyelocytic leukemia. Blood 2013;121: 1432-5

99.

Huang J, Gong Z, Ghosal G, Chen J. SOSS complexes participate in the maintenance of genomic stability. Mol Cell 2009;35:384-93

100.

Richard DJ, Bolderson E, Cubeddu L, et al. Single-stranded DNA-binding protein hSSB1 is critical for genomic stability. Nature 2008;453:677-81

101.

Li Y, Bolderson E, Kumar R, et al. HSSB1 and hSSB2 form similar multiprotein complexes that participate in DNA damage response. J Biol Chem 2009;284:23525-31

102.

Mozziconacci MJ, Liberatore C, Grignani F, et al. Atypical response to all-trans retinoic acid in a der(5)t(5;17) acute promyelocytic leukemia. Leukemia 1999;13:862-8

103.

Fenaux P, Chomienne C, Degos L. Treatment of acute promyelocytic leukaemia. Best Pract Res Clin Haematol 2001;14:153-74

•

A good review on the treatment of APL with all-trans retinoic acid and arsenic trioxide.

104.

Tallman MS, Rowe JM. Long-term follow-up and potential for cure in acute promyelocytic leukaemia. Best Pract Res Clin Haematol 2003;16:535-43

105.

Park DJ, Vuong PT, de Vos S, et al. Comparative analysis of genes regulated by PML/RARa and PLZF/RARa in response to

Expert Rev. Hematol. 7(3), (2014)

RARA fusion genes in APL

Expert Review of Hematology Downloaded from informahealthcare.com by Washington University Library on 01/01/15 For personal use only.

retinoic acid using oligonucleotide arrays. Blood 2003;102:3727-36

116.

Sukhai MA, Thomas M, Xuan Y, et al. Evidence of functional interaction between NuMA-RARalpha and RXRalpha in an in vivo model of acute promyelocytic leukemia. Oncogene 2008;27:4666-77 Kamashev D, Vitoux D, De The´ H. PML-RARA-RXR oligomers mediate retinoid and rexinoid/cAMP cross-talk in acute promyelocytic leukemia cell differentiation. J Exp Med 2004;199: 1163-74

106.

Gallagher RE. Retinoic acid resistance in acute promyelocytic leukemia. Leukemia 2002;16:1940-58

107.

Imaizumi M, Suzuki H, Yoshinari M, et al. Mutations in the E-domain of RAR portion of the PML/RAR chimeric gene may confer clinical resistance to all-trans retinoic acid in acute promyelocytic leukemia. Blood 1998;92:374-82

117.

Zhou DC, Kim SH, Ding W, et al. Frequent mutations in the ligand-binding domain of PML-RARalpha after multiple relapses of acute promyelocytic leukemia: analysis for functional relationship to response to all-trans retinoic acid and histone deacetylase inhibitors in vitro and in vivo. Blood 2002;99:1356-63

118.

108.

109.

Marasca R, Zucchini P, Galimberti S, et al. Missense mutations in the PML/RARalpha ligand binding domain in ATRA-resistant As(2)O(3) sensitive relapsed acute promyelocytic leukemia. Haematologica 1999;84:963-8

110.

Lengfelder E, Hofmann WK, Nowak D. Impact of arsenic trioxide in the treatment of acute promyelocytic leukemia. Leukemia 2012;26:433-42

111.

Shao W, Fanelli M, Ferrara FF, et al. Arsenic trioxide as an inducer of apoptosis and loss of PML/RAR alpha protein in acute promyelocytic leukemia cells. J Natl Cancer Inst 1998;90:124-33

112.

Look AT. Arsenic and apoptosis in the treatment of acute promyelocytic leukemia. J Natl Cancer Inst 1998;90:86-8

113.

Zhang TD, Chen GQ, Wang ZG, et al. Arsenic trioxide, a therapeutic agent for APL. Oncogene 2001;20:7146-53

114.

Mistry AR, Pedersen EW, Solomon E, Grimwade D. The molecular pathogenesis of acute promyelocytic leukaemia: implications for the clinical management of the disease. Blood Rev 2003;17:71-97

••

115.

••

A comprehensive study on the implications of molecular abnormalities in the management of APL. Zeisig BB, Kwok C, Zelent A, et al. Recruitment of RXR by homotetrameric RARalpha fusion proteins is essential for transformation. Cancer Cell 2007;12:36-51 A key study on the action of RARA fusion proteins in transforming cells.

informahealthcare.com

119.

120.

121.

122.

123.

124.

125.

126.

Sternsdorf T, Phan VT, Maunakea ML, et al. Forced retinoic acid receptor alpha homodimers prime mice for APL-like leukemia. Cancer Cell 2006;9:81-94 Kwok C, Zeisig BB, Dong S, So CW. Forced homo-oligomerization of RARalpha leads to transformation of primary hematopoietic cells. Cancer Cell 2006;9: 95-108 Licht JD. Reconstructing a disease: what essential features of the retinoic acid receptor fusion oncoproteins generate acute promyelocytic leukemia? Cancer Cell 2006;9:73-4 Alcalay M, Meani N, Gelmetti V, et al. Acute myeloid leukemia fusion proteins deregulate genes involved in stem cell maintenance and DNA repair. J Clin Invest 2003;112:1751-61 Muller-Tidow C, Steffen B, Cauvet T, et al. Translocation products in acute myeloid leukemia activate the Wnt signaling pathway in hematopoietic cells. Mol Cell Biol 2004;24:2890-904 Haferlach T, Kohlmann A, Schnittger S, et al. AML M3 and AML M3 variant each have a distinct gene expression signature but also share patterns different from other genetically defined AML subtypes. Genes Chromosomes Cancer 2005;43:113-27 Valk PJ, Verhaak RG, Beijen MA, et al. Prognostically useful gene-expression profiles in acute myeloid leukemia. N Engl J Med 2004;350:1617-28 Rice KL, Hormaeche I, Doulatov S, et al. Comprehensive genomic screens identify a role for PLZF-RARalpha as a positive regulator of cell proliferation via direct regulation of c-MYC. Blood 2009;114: 5499-511 Thompson A, Quinn MF, Grimwade D, et al. Global down-regulation of HOX gene expression in PML-RARalpha+ acute promyelocytic leukemia identified by small-array real-time PCR. Blood 2003;101: 1558-65

Review

127.

Spicuglia S, Vincent-Fabert C, Benoukraf T, et al. Characterisation of genome-wide PLZF/RARA target genes. PLoS One 2011;6:e24176

•

One of the rare studies on gene expression profiling in APL not associated with promyelocytic leukemia– retinoic acid receptor a.

128.

Lin RJ, Sternsdorf T, Tini M, Evans RM. Transcriptional regulation in acute promyelocytic leukemia. Oncogene 2001;20: 7204-15

129.

Ruthardt M, Testa U, Nervi C, et al. Opposite effects of the acute promyelocytic leukemia PML-retinoic acid receptor alpha (RAR alpha) and PLZF-RAR alpha fusion proteins on retinoic acid signalling. Mol Cell Biol 1997;17:4859-69

130.

Walter MJ, Park JS, Lau SK, et al. Expression profiling of murine acute promyelocytic leukemia cells reveals multiple model-dependent progression signatures. Mol Cell Biol 2004;24:10882-93

131.

Tan Y, Bian S, Xu Z, et al. The short isoform of the long-type PML-RARA fusion gene in acute promyelocytic leukaemia lacks sensitivity to all-trans-retinoic acid. Br J Haematol 2013;162:93-7

132.

Garzon R, Pichiorri F, Palumbo T, et al. MicroRNA gene expression during retinoic acid-induced differentiation of human acute promyelocytic leukemia. Oncogene 2007;26: 4148-57

133.

Saumet A, Vetter G, Bouttier M, et al. Transcriptional repression of microRNA genes by PML-RARA increases expression of key cancer proteins in acute promyelocytic leukemia. Blood 2009;113: 412-21

•

An interesting study on the relations between miRNA genes and fusion genes in APL.

134.

De Braekeleer E, Douet-Guilbert N, Basinko A, et al. HOX gene dysregulation in acute myeloid leukemia. Future Oncol 2014;10(3):475-95

135.

Vitoux D, Nasr R, de The H. Acute promyelocytic leukemia: new issues on pathogenesis and treatment response. Int J Biochem Cell Biol 2007;39:1063-70

136.

de Lera AR, Bourguet W, Altucci L, Gronemeyer H. Design of selective nuclear receptor modulators: RAR and RXR as a case study. Nat Rev Drug Discov 2007;6: 811-20

357