From www.bloodjournal.org by guest on September 11, 2016. For personal use only.
heavy to light polysomes, g-globin mRNA was determined to be translated approximately twice as efficiently as b-globin mRNA. They also demonstrated directly an increase in g-globin protein synthesis in salubrinal-treated K562 cells by measuring puromycin-released nascent polypeptides that were reactive to anti-HbF antibody. Weinberg et al have shown earlier that butyrate treatment of SCA patient blood samples increased efficiency of translation of g-globin mRNA.9 The current study by Hahn and Lowrey demonstrated that increased translational of g-globin mRNA is mediated by eIF2aP signaling. What might be the mechanism by which salubrinal and eIF2aP increase the translational efficiency of g-globin mRNA? The one well-established cardinal feature for the selective upregulation of translation by eIF2aP is the presence of upstream open reading frames (uORFs) in the 59 untranslated region (UTR) of unique classes of mRNAs such as ATF4 mRNA. Translation of ATF4 mRNA is selectively enhanced by activation of HRI-eIF2aP signaling in normal and b-thalassemic erythroid precursors.8,10 Under nonstressed conditions, these uORFs restrict the translation at the downstream-initiating AUG codon encoding ATF4 protein. Upon stress, phosphorylation of eIF2a reduces the pool of functional eIF2 and slows down the initiation to permit the translation start site at the coding sequence of ATF4 mRNA (see figure, panel B). It will be of great interest to determine whether uORFs are involved in the increased translational efficiency of g-globin mRNA upon salubrinal treatment. Although there is no cognate AUG codon in the 59UTR of annotated g-globin mRNA, there are non-AUG initiation codons, which can generate uORFs. Alternatively, the downstream targets of eIF2aP signaling may participate in this event. It is also possible that a yet-to-be-discovered novel mechanism may regulate g-globin mRNA translation. By identifying eIF2aP and translation initiation as a mechanism for induction of HbF, the study of Hahn and Lowrey provides the impetus for more effective combinational therapy targeting both transcription and translation in treating b-hemoglobinopathies.
Conflict-of-interest disclosure: The author declares no competing financial interests. n REFERENCES
6. Suzuki M, Yamamoto M, Engel JD. Fetal globin gene repressors as drug targets for molecular therapies to treat the b-globinopathies. Mol Cell Biol. 2014;34(19): 3560-3569.
1. Hahn CK, Lowrey CH. Induction of fetal hemoglobin through enhanced translation efficiency of g-globin mRNA. Blood. 2014;124(17):2730-2734.
7. Hahn CK, Lowrey CH. Eukaryotic initiation factor 2a phosphorylation mediates fetal hemoglobin induction through a post-transcriptional mechanism. Blood. 2013; 122(4):477-485.
2. Kraus AP, Koch B, Burckett L. Two families showing interaction of haemoglobin C or thalassaemia with high foetal haemoglobin in adults. BMJ. 1961;1(5237):1434-1436.
8. Chen JJ. Translational control by heme-regulated eIF2a kinase during erythropoiesis. Curr Opin Hematol. 2014;21(3):172-178.
3. Conley CL, Weatherall DJ, Richardson SN, Shepard MK, Charache S. Hereditary persistence of fetal hemoglobin: a study of 79 affected persons in 15 Negro families in Baltimore. Blood. 1963;21:261-281.
9. Weinberg RS, Ji X, Sutton M, et al. Butyrate increases the efficiency of translation of gamma-globin mRNA. Blood. 2005;105(4):1807-1809.
4. Musallam KM, Taher AT, Cappellini MD, Sankaran VG. Clinical experience with fetal hemoglobin induction therapy in patients with b-thalassemia. Blood. 2013; 121(12):2199-2212, quiz 2372.
10. Suragani RN, Zachariah RS, Velazquez JG, et al. Heme-regulated eIF2a kinase activated Atf4 signaling pathway in oxidative stress and erythropoiesis. Blood. 2012; 119(22):5276-5284.
5. Sankaran VG, Orkin SH. The switch from fetal to adult hemoglobin. Cold Spring Harb Perspect Med. 2013;3(1):a011643.
© 2014 by The American Society of Hematology
l l l TRANSPLANTATION
Comment on Oevermann et al, page 2744
KIR B or not to be?...that is the question for ALL ----------------------------------------------------------------------------------------------------Michael R. Verneris and Jeffrey S. Miller
UNIVERSITY OF MINNESOTA
In this issue of Blood, Oevermann et al report on a cohort of 85 children (median age, 10 years) undergoing T-cell–depleted haploidentical hematopoietic cell transplantation (HCT) for acute lymphoblastic leukemia (ALL), where variations in the killer-cell immunoglobulin-like receptor (KIR) gene “content” of the donor were associated with significantly less relapse and improved disease-free survival.1
A
lthough antihost alloreactivity varies among HCT donors, differences are most pronounced in the human leukocyte antigen (HLA) mismatched setting, where mismatch between donor KIR and recipient KIR ligands (ie, HLA) are more frequent. It was initially assumed that natural killer (NK) cells kill targets without restriction by the HLA complex. This paradigm changed in 1990, when K¨arre and Ljunggren demonstrated that NK cell killing is directed to transformed targets “missing self” HLA.2 The loss of HLA results in a lack of inhibitory signaling and an increase in cytotoxicity. Conversely, the ligation of self HLA to inhibitory KIR prevents NK cell activation (including lysis and cytokine production) and promotes NK cell tolerance.3 These mechanisms are mediated by activating and inhibitory KIR encoded by 15 separate polymorphic genes.4 Individuals differ in the
BLOOD, 23 OCTOBER 2014 x VOLUME 124, NUMBER 17
number of genes contained within each KIR haplotype, where KIR A haplotypes have a fixed gene content and KIR B haplotypes have variable content including 1 or more of 7 KIR B-specific genes: KIR2DS2, KIR2DL2, KIR2DS1, KIR3DS1, KIR2DS3, KIR2DS35, and KIR2DL55 (www.ebi.ac.uk/ ipd/kir/). Inhibitory KIR2DL2, KIR2DL3, and KIR3DL1 recognize shared motifs in HLA C1, HLA C2, and HLA Bw4. Although KIR2DS1 can recognize HLA C2 and KIR2DS2 has been reported to recognize HLA A11, the ligands for most activating KIR remain unknown. Inhibitory KIR contributes to the acquisition of NK cell function via a process called licensing, or education, in which NK cells expressing KIR that recognize self HLA acquire maximum functional capacity.6 Signaling through activating KIR may stimulate
2623
From www.bloodjournal.org by guest on September 11, 2016. For personal use only.
NK cells directly or indirectly by modification of NK cell education.7 In a large cohort of recipients of T-cell–replete unrelated adult donor HCT, Cooley et al demonstrated that donor, but not recipient, KIR B/x genotype was associated with protection from acute myeloid leukemia (AML) relapse.8 This protection was not observed in ALL, raising the possibility that myeloid leukemia is more susceptible to NK killing. This finding is consistent with the differential effect of KIR–ligand mismatch on outcome after haploidentical HCT for AML vs ALL, reported by the Perugia group,9 and may be explained by the higher density of HLA (inhibitory KIR ligand) expressed on ALL blasts and by the lower density of adhesion receptors and other NK cell-activating ligands on ALL compared with AML targets. In the cohort described by Oevermann, the KIR B/x genotype was present in 74% of the donors and was associated with 51% disease-free survival compared with 30% in the transplants from KIR A/A donors. Moreover, donors with a higher number of KIR B genes (ie, KIR B content score8) conferred the best outcomes. The authors recommend that related donors with KIR B/x genotypes be used for transplantation for pediatric patients with ALL. These findings must be reconciled with previous reports suggesting adult ALL is less susceptible to NK cell-mediated killing. There are 3 possible explanations. First, adult patients are more likely to have high-risk features at
2624
diagnosis, defined by high-risk cytogenic changes (Philadelphia chromosome, mixedlineage leukemia gene rearrangements, and so on). These differential genetic events could affect the sensitivity of ALL to NK cell killing, as has been recently demonstrated for AML.10 Second, the conclusions from Oevermann et al are limited to the specific setting of haploidentical HCT. Because of variations in the degree of T-cell depletion and the use of total-body irradiation, it is difficult to dissect out components of the transplant platform that may also influence outcome. Last, it is possible that the results are a result of the relatively small sample size, and therefore, these data should compel other single-center or registry studies to validate these findings. In summary, Oevermann et al present important and provocative data demonstrating a benefit in relapse protection and survival for pediatric patients with ALL transplanted with haploidentical donors with KIR B/x genotypes. Donor selection based on KIR B content is feasible because of the high frequency of KIR B genes in this population and the lack of data suggesting any down side to avoiding KIR A/A donors. Studies in different cohorts using other transplant platforms and donor cell sources are warranted to determine the extent of the benefit associated with KIR B/x donors. These findings should motivate mechanistic analyses to determine why the response of pediatric ALL to KIR B/x donors is similar to that of adult AML, and not adult ALL.
Conflict-of-interest disclosure: The authors declare no competing financial interests. n REFERENCES 1. Oevermann L, Michaelis SU, Mezger M, et al. KIR B haplotype donors confer a reduced risk of relapse after haploidentical transplantation in children with ALL. Blood. 2014;124(17):2744–2747. 2. Ljunggren HG, K¨arre K. In search of the ‘missing self ’: MHC molecules and NK cell recognition. Immunol Today. 1990;11(7):237-244. 3. Raulet DH. Missing self recognition and self tolerance of natural killer (NK) cells. Semin Immunol. 2006;18(3): 145-150. 4. Uhrberg M, Valiante NM, Shum BP, et al. Human diversity in killer cell inhibitory receptor genes. Immunity. 1997;7(6):753-763. 5. Cooley S, Weisdorf DJ, Guethlein LA, et al. Donor killer cell Ig-like receptor B haplotypes, recipient HLA-C1, and HLA-C mismatch enhance the clinical benefit of unrelated transplantation for acute myelogenous leukemia. J Immunol. 2014;192(10):4592-4600. 6. Kim S, Poursine-Laurent J, Truscott SM, et al. Licensing of natural killer cells by host major histocompatibility complex class I molecules. Nature. 2005;436(7051):709-713. 7. Fauriat C, Ivarsson MA, Ljunggren HG, Malmberg KJ, Micha¨elsson J. Education of human natural killer cells by activating killer cell immunoglobulin-like receptors. Blood. 2010;115(6):1166-1174. 8. Cooley S, Weisdorf DJ, Guethlein LA, et al. Donor selection for natural killer cell receptor genes leads to superior survival after unrelated transplantation for acute myelogenous leukemia. Blood. 2010;116(14):2411-2419. 9. Ruggeri L, Capanni M, Urbani E, et al. Effectiveness of donor natural killer cell alloreactivity in mismatched hematopoietic transplants. Science. 2002;295(5562): 2097-2100. 10. Elias S, Yamin R, Golomb L, et al. Immune evasion by oncogenic proteins of acute myeloid leukemia. Blood. 2014;123(10):1535-1543. © 2014 by The American Society of Hematology
BLOOD, 23 OCTOBER 2014 x VOLUME 124, NUMBER 17
From www.bloodjournal.org by guest on September 11, 2016. For personal use only.
2014 124: 2623-2624 doi:10.1182/blood-2014-09-596395
KIR B or not to be?...that is the question for ALL Michael R. Verneris and Jeffrey S. Miller
Updated information and services can be found at: http://www.bloodjournal.org/content/124/17/2623.full.html Articles on similar topics can be found in the following Blood collections Free Research Articles (4041 articles) Information about reproducing this article in parts or in its entirety may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#repub_requests Information about ordering reprints may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#reprints Information about subscriptions and ASH membership may be found online at: http://www.bloodjournal.org/site/subscriptions/index.xhtml
Blood (print ISSN 0006-4971, online ISSN 1528-0020), is published weekly by the American Society of Hematology, 2021 L St, NW, Suite 900, Washington DC 20036. Copyright 2011 by The American Society of Hematology; all rights reserved.
heavy to light polysomes, g-globin mRNA was determined to be translated approximately twice as efficiently as b-globin mRNA. They also demonstrated directly an increase in g-globin protein synthesis in salubrinal-treated K562 cells by measuring puromycin-released nascent polypeptides that were reactive to anti-HbF antibody. Weinberg et al have shown earlier that butyrate treatment of SCA patient blood samples increased efficiency of translation of g-globin mRNA.9 The current study by Hahn and Lowrey demonstrated that increased translational of g-globin mRNA is mediated by eIF2aP signaling. What might be the mechanism by which salubrinal and eIF2aP increase the translational efficiency of g-globin mRNA? The one well-established cardinal feature for the selective upregulation of translation by eIF2aP is the presence of upstream open reading frames (uORFs) in the 59 untranslated region (UTR) of unique classes of mRNAs such as ATF4 mRNA. Translation of ATF4 mRNA is selectively enhanced by activation of HRI-eIF2aP signaling in normal and b-thalassemic erythroid precursors.8,10 Under nonstressed conditions, these uORFs restrict the translation at the downstream-initiating AUG codon encoding ATF4 protein. Upon stress, phosphorylation of eIF2a reduces the pool of functional eIF2 and slows down the initiation to permit the translation start site at the coding sequence of ATF4 mRNA (see figure, panel B). It will be of great interest to determine whether uORFs are involved in the increased translational efficiency of g-globin mRNA upon salubrinal treatment. Although there is no cognate AUG codon in the 59UTR of annotated g-globin mRNA, there are non-AUG initiation codons, which can generate uORFs. Alternatively, the downstream targets of eIF2aP signaling may participate in this event. It is also possible that a yet-to-be-discovered novel mechanism may regulate g-globin mRNA translation. By identifying eIF2aP and translation initiation as a mechanism for induction of HbF, the study of Hahn and Lowrey provides the impetus for more effective combinational therapy targeting both transcription and translation in treating b-hemoglobinopathies.
Conflict-of-interest disclosure: The author declares no competing financial interests. n REFERENCES
6. Suzuki M, Yamamoto M, Engel JD. Fetal globin gene repressors as drug targets for molecular therapies to treat the b-globinopathies. Mol Cell Biol. 2014;34(19): 3560-3569.
1. Hahn CK, Lowrey CH. Induction of fetal hemoglobin through enhanced translation efficiency of g-globin mRNA. Blood. 2014;124(17):2730-2734.
7. Hahn CK, Lowrey CH. Eukaryotic initiation factor 2a phosphorylation mediates fetal hemoglobin induction through a post-transcriptional mechanism. Blood. 2013; 122(4):477-485.
2. Kraus AP, Koch B, Burckett L. Two families showing interaction of haemoglobin C or thalassaemia with high foetal haemoglobin in adults. BMJ. 1961;1(5237):1434-1436.
8. Chen JJ. Translational control by heme-regulated eIF2a kinase during erythropoiesis. Curr Opin Hematol. 2014;21(3):172-178.
3. Conley CL, Weatherall DJ, Richardson SN, Shepard MK, Charache S. Hereditary persistence of fetal hemoglobin: a study of 79 affected persons in 15 Negro families in Baltimore. Blood. 1963;21:261-281.
9. Weinberg RS, Ji X, Sutton M, et al. Butyrate increases the efficiency of translation of gamma-globin mRNA. Blood. 2005;105(4):1807-1809.
4. Musallam KM, Taher AT, Cappellini MD, Sankaran VG. Clinical experience with fetal hemoglobin induction therapy in patients with b-thalassemia. Blood. 2013; 121(12):2199-2212, quiz 2372.
10. Suragani RN, Zachariah RS, Velazquez JG, et al. Heme-regulated eIF2a kinase activated Atf4 signaling pathway in oxidative stress and erythropoiesis. Blood. 2012; 119(22):5276-5284.
5. Sankaran VG, Orkin SH. The switch from fetal to adult hemoglobin. Cold Spring Harb Perspect Med. 2013;3(1):a011643.
© 2014 by The American Society of Hematology
l l l TRANSPLANTATION
Comment on Oevermann et al, page 2744
KIR B or not to be?...that is the question for ALL ----------------------------------------------------------------------------------------------------Michael R. Verneris and Jeffrey S. Miller
UNIVERSITY OF MINNESOTA
In this issue of Blood, Oevermann et al report on a cohort of 85 children (median age, 10 years) undergoing T-cell–depleted haploidentical hematopoietic cell transplantation (HCT) for acute lymphoblastic leukemia (ALL), where variations in the killer-cell immunoglobulin-like receptor (KIR) gene “content” of the donor were associated with significantly less relapse and improved disease-free survival.1
A
lthough antihost alloreactivity varies among HCT donors, differences are most pronounced in the human leukocyte antigen (HLA) mismatched setting, where mismatch between donor KIR and recipient KIR ligands (ie, HLA) are more frequent. It was initially assumed that natural killer (NK) cells kill targets without restriction by the HLA complex. This paradigm changed in 1990, when K¨arre and Ljunggren demonstrated that NK cell killing is directed to transformed targets “missing self” HLA.2 The loss of HLA results in a lack of inhibitory signaling and an increase in cytotoxicity. Conversely, the ligation of self HLA to inhibitory KIR prevents NK cell activation (including lysis and cytokine production) and promotes NK cell tolerance.3 These mechanisms are mediated by activating and inhibitory KIR encoded by 15 separate polymorphic genes.4 Individuals differ in the
BLOOD, 23 OCTOBER 2014 x VOLUME 124, NUMBER 17
number of genes contained within each KIR haplotype, where KIR A haplotypes have a fixed gene content and KIR B haplotypes have variable content including 1 or more of 7 KIR B-specific genes: KIR2DS2, KIR2DL2, KIR2DS1, KIR3DS1, KIR2DS3, KIR2DS35, and KIR2DL55 (www.ebi.ac.uk/ ipd/kir/). Inhibitory KIR2DL2, KIR2DL3, and KIR3DL1 recognize shared motifs in HLA C1, HLA C2, and HLA Bw4. Although KIR2DS1 can recognize HLA C2 and KIR2DS2 has been reported to recognize HLA A11, the ligands for most activating KIR remain unknown. Inhibitory KIR contributes to the acquisition of NK cell function via a process called licensing, or education, in which NK cells expressing KIR that recognize self HLA acquire maximum functional capacity.6 Signaling through activating KIR may stimulate
2623
From www.bloodjournal.org by guest on September 11, 2016. For personal use only.
NK cells directly or indirectly by modification of NK cell education.7 In a large cohort of recipients of T-cell–replete unrelated adult donor HCT, Cooley et al demonstrated that donor, but not recipient, KIR B/x genotype was associated with protection from acute myeloid leukemia (AML) relapse.8 This protection was not observed in ALL, raising the possibility that myeloid leukemia is more susceptible to NK killing. This finding is consistent with the differential effect of KIR–ligand mismatch on outcome after haploidentical HCT for AML vs ALL, reported by the Perugia group,9 and may be explained by the higher density of HLA (inhibitory KIR ligand) expressed on ALL blasts and by the lower density of adhesion receptors and other NK cell-activating ligands on ALL compared with AML targets. In the cohort described by Oevermann, the KIR B/x genotype was present in 74% of the donors and was associated with 51% disease-free survival compared with 30% in the transplants from KIR A/A donors. Moreover, donors with a higher number of KIR B genes (ie, KIR B content score8) conferred the best outcomes. The authors recommend that related donors with KIR B/x genotypes be used for transplantation for pediatric patients with ALL. These findings must be reconciled with previous reports suggesting adult ALL is less susceptible to NK cell-mediated killing. There are 3 possible explanations. First, adult patients are more likely to have high-risk features at
2624
diagnosis, defined by high-risk cytogenic changes (Philadelphia chromosome, mixedlineage leukemia gene rearrangements, and so on). These differential genetic events could affect the sensitivity of ALL to NK cell killing, as has been recently demonstrated for AML.10 Second, the conclusions from Oevermann et al are limited to the specific setting of haploidentical HCT. Because of variations in the degree of T-cell depletion and the use of total-body irradiation, it is difficult to dissect out components of the transplant platform that may also influence outcome. Last, it is possible that the results are a result of the relatively small sample size, and therefore, these data should compel other single-center or registry studies to validate these findings. In summary, Oevermann et al present important and provocative data demonstrating a benefit in relapse protection and survival for pediatric patients with ALL transplanted with haploidentical donors with KIR B/x genotypes. Donor selection based on KIR B content is feasible because of the high frequency of KIR B genes in this population and the lack of data suggesting any down side to avoiding KIR A/A donors. Studies in different cohorts using other transplant platforms and donor cell sources are warranted to determine the extent of the benefit associated with KIR B/x donors. These findings should motivate mechanistic analyses to determine why the response of pediatric ALL to KIR B/x donors is similar to that of adult AML, and not adult ALL.
Conflict-of-interest disclosure: The authors declare no competing financial interests. n REFERENCES 1. Oevermann L, Michaelis SU, Mezger M, et al. KIR B haplotype donors confer a reduced risk of relapse after haploidentical transplantation in children with ALL. Blood. 2014;124(17):2744–2747. 2. Ljunggren HG, K¨arre K. In search of the ‘missing self ’: MHC molecules and NK cell recognition. Immunol Today. 1990;11(7):237-244. 3. Raulet DH. Missing self recognition and self tolerance of natural killer (NK) cells. Semin Immunol. 2006;18(3): 145-150. 4. Uhrberg M, Valiante NM, Shum BP, et al. Human diversity in killer cell inhibitory receptor genes. Immunity. 1997;7(6):753-763. 5. Cooley S, Weisdorf DJ, Guethlein LA, et al. Donor killer cell Ig-like receptor B haplotypes, recipient HLA-C1, and HLA-C mismatch enhance the clinical benefit of unrelated transplantation for acute myelogenous leukemia. J Immunol. 2014;192(10):4592-4600. 6. Kim S, Poursine-Laurent J, Truscott SM, et al. Licensing of natural killer cells by host major histocompatibility complex class I molecules. Nature. 2005;436(7051):709-713. 7. Fauriat C, Ivarsson MA, Ljunggren HG, Malmberg KJ, Micha¨elsson J. Education of human natural killer cells by activating killer cell immunoglobulin-like receptors. Blood. 2010;115(6):1166-1174. 8. Cooley S, Weisdorf DJ, Guethlein LA, et al. Donor selection for natural killer cell receptor genes leads to superior survival after unrelated transplantation for acute myelogenous leukemia. Blood. 2010;116(14):2411-2419. 9. Ruggeri L, Capanni M, Urbani E, et al. Effectiveness of donor natural killer cell alloreactivity in mismatched hematopoietic transplants. Science. 2002;295(5562): 2097-2100. 10. Elias S, Yamin R, Golomb L, et al. Immune evasion by oncogenic proteins of acute myeloid leukemia. Blood. 2014;123(10):1535-1543. © 2014 by The American Society of Hematology
BLOOD, 23 OCTOBER 2014 x VOLUME 124, NUMBER 17
From www.bloodjournal.org by guest on September 11, 2016. For personal use only.
2014 124: 2623-2624 doi:10.1182/blood-2014-09-596395
KIR B or not to be?...that is the question for ALL Michael R. Verneris and Jeffrey S. Miller
Updated information and services can be found at: http://www.bloodjournal.org/content/124/17/2623.full.html Articles on similar topics can be found in the following Blood collections Free Research Articles (4041 articles) Information about reproducing this article in parts or in its entirety may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#repub_requests Information about ordering reprints may be found online at: http://www.bloodjournal.org/site/misc/rights.xhtml#reprints Information about subscriptions and ASH membership may be found online at: http://www.bloodjournal.org/site/subscriptions/index.xhtml
Blood (print ISSN 0006-4971, online ISSN 1528-0020), is published weekly by the American Society of Hematology, 2021 L St, NW, Suite 900, Washington DC 20036. Copyright 2011 by The American Society of Hematology; all rights reserved.
