EDITORIALS Metastatic Models and Molecular Genetics of Prostate Cancer W. Marston Linehan* John P. Long, Patricia S. Steeg, James R. Gnarra
914
Received May 15, 1992; accepted May 18, 1992. W. M. Linehan, J. P. Long, J. R. Gnarra (Surgery Branch, Division of Can cer Treatment), P- S. Steeg (Laboratory of Pathology, Division of Cancer Biol ogy. Diagnosis, and Centers), National Cancer Institute, Bethesda, Md. Correspondence to: W. Marston Linehan, M.D., Bldg. 10, Rm. 2B47 National Institutes of Health. Bethesda, MD 20892.
Journal of the National Cancer Institute
Downloaded from http://jnci.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
Cancer of the prostate is now recognized as the most common cancer in men. The estimated prevalence of prostate carcinoma in the United States is striking: Autopsies performed on men 50 years of age or older who died from other causes have revealed that 30%-50% of the individuals harbored microscopic foci of prostate carcinoma (/). It is projected that more than 130000 new cases of prostate cancer will be diagnosed in the United States this year and that 32000 men will die of the disease. For reasons that are not yet well understood, Black American men are nearly twice as likely to develop this form of cancer as White American men (2). Continued improvements in diagnostic and surgical techniques have led to more effective management of patients with localized prostate carcinoma. However, for patients with advanced-stage disease, the situation is more grave. Approximately 80% of patients with advanced prostate carcinoma will develop skeletal metastases and, for these individuals, there are currently only minimally effective forms of therapy. The molecular mechanisms underlying the etiology and progression of prostate cancer remain to be elucidated. Although abnormalities in growth factor-mediated regulation of prostate cancer are the subject of intense investigation, the autocrine, paracrine, and endocrine effects of prostate carcinomaproduced factors have not yet been fully characterized. Recent studies suggest a role for genetic factors in the development of prostate cancer. Several groups have demonstrated that First-degree relatives of men with prostate cancer are two to three times more likely to develop this disease than the general population. Steinberg et al. (3) showed that men with two or three First-degree relatives affected with prostate cancer had a Fivefold or 11-fold increased risk, respectively, of developing prostate cancer themselves. In addition, Carter et al. (4) recently showed that this familial clustering follows a pattern of mendelian inheritance. These and other studies suggest the existence of a heritable prostate cancer susceptibility gene(s) that may play a role in initiation and/or progression of the disease. IdentiFication of such a gene(s) will require extensive molecular analyses, including cytogenetic characterization of human prostate tumors to identify and map any consistent chromosomal abnormalities; linkage studies using restriction fragment length polymorphism (RFLP) analyses to identify speciFic alleles involved
in prostate cancer; chromosomal transfer studies to reconstituti lost alleles and suppress tumorigenesis; and characterization o expression in prostate carcinoma of known oncogenes an< tumor suppressor genes. Although some progress along these lines has been made research has been hampered by the limited availability o human prostate carcinoma tissue. It is hoped that the recen support from the National Institutes of Health for establishing ; human tumor bank will alleviate this problem. In addition, i has proven difficult to establish suitable cell lines because eel cultures from primary human prostate carcinoma tissue oftei become overgrown with normal, diploid (typically stromal cells. As a result, there are currently only four prostate car cinoma cell lines available for study. Using a different in vim approach, Peehl and co-workers (5) have demonstrated th( value of short-term explant cultures for cytogenetic and othe analyses of prostate cancer; however, this promising technique has not yet achieved widespread use. Despite these practical difficulties, early investigations of tht molecular genetics of prostate cancer have yielded encouraging results. In independent analyses of human prostate carcinorm tissue, Bergerheim and co-workers (6) have described allelic deletions on chromosomes 8, 10, and 16, and Carter et al. (7 have demonstrated loss of heterozygosity on chromosomes 1C and 16. In addition, recent work (8) suggests that the reintroduction of a normal chromosome 11 into a prostate carcinoma cell line can suppress tumorigenicity. Studies in animal models have demonstrated a potentially signiFicant role of oncogenes such as ras and myc in the progression of prostate cancer (9). The p53 tumor suppressor gene has been shown to be defective or missing in two prostate carcinoma cell lines, and transfection of the wild-type p53 gene into those cells generated clones displaying diminished growth in colony-forming assays ir vitro. Further, aberrant expression of the retinoblastoma susceptibility gene (RB) was seen in DU145 cells, one of three prostate carcinoma lines evaluated. Retroviral transduction ol the wild-type RB gene into this cell line diminished, but did not fully abrogate, tumorigenicity of the cells in nude mice. Finally, preliminary studies have demonstrated abnormalities in the expression of p53 and RB proteins in human prostate carcinomas (10,11). Like the molecular genetic studies, study of the metastatic phenotype in prostate cancer has been limited by the lack of a well-characterized tumor bank and of suitable in vitro and in vivo models. Because of the slow doubling time of this malignancy, molecular characterization of metastases will require tissue from patients with years of follow-up. Little is known about the metastatic properties in vivo of the four available prostate carcinoma cell lines. In particular, no good model exists which reproduces the propensity of prostate cancer to metastasize to bony structures. PC-3 cells have been reported to induce vertebral metastases in nude mice when they are
Racial Variation in Cancer Incidence: Fact or Artifact? Laurence N. Kolonel, * Marc T. Goodman Accuracy in determining cancer incidence rates for ethnic minorities is of fundamental importance to researchers, health service providers, and policy-makers responsible for the allocation of limited health care resources. Thus, the report by Frost et al. (/) in this issue of the Journal raises serious issues for discussion. In their report, the authors show that a very high percentage of Native Americans in the population-based Surveillance, Epidemiology, and End Results (SEER) registry in the Seattle-Puget Sound area are misclassified, largely as White. Vol. 84, No. 12, June 17, 1992
is of paramount importance. Continued intensive efforts in this area will lead to more efficient diagnosis and to more effective forms of therapy for patients with this disease.
References (/) CHODAK GW: Early detection and screening for prostatic cancer. Urology 34 (suppl 4): 10. 1989 (2) MEIKLE AW. SMITH JA: Epidemiology of prostate cancer. In Early Detection and Treatment of Localized Carcinoma of the Prostate (Smith JA. ed). Philadelphia: Saunders. 1990, pp 709-718 (3) STEINBERG GD, CARTER BS. BEATY TH, ET AL: Family history and the
risk of prostate cancer. Prostate 17:337-347. 1990 (4) CARTER BS, BEATY TH, STEINBERG GD. ET AL: Mendelian inheritance of
familial prostate cancer. Proc Natl Acad Sci USA 89:3367-3371. 1992 (5) PEEHL DM, WONG ST. STAMEY TA: Cytostatic effects of suramin on
prostate cancer cells cultured from primary tumors. J Urol 145:624-630. 1991 (6) BERGERHEIM US. KUNIMI K, COLLINS VP. ET AL: Deletion mapping of
chromosomes 8, 10. and 16 in human prostatic carcinoma. Genes Chromosom Cancer 3:215-220, 1991 (7) CARTER BS, EWING CM, WARD WS, ET AL: Allelic loss of chromosomes
16q and lOq in human prostate cancer. Proc Natl Acad Sci USA 87:8751-8755, 1990 (8) BOVA GS, ICHIKAWA T, ISAACS JT. ET AL. Insertion of human chromo-
somes 8 and 11 into human prostate cancer cell lines using microcell transfer technique. J Urol 147 (suppl):2l5A. 1992 (9) THOMPSON TC, SOUTHGATE J, KITCHNER G, ET AL: Multistage car-
cinogenesis induced by ras and myc oncogenes in a reconstituted organ. Cell 56.917-930. 1989 (10) EFFERT PJ. NEUBAUER A. WALTHER PJ. ET AL: Alterations of the p53 gene
are associated with the progression of a human prostate carcinoma. J Urol 147:789-793, 1992 (//) BOOKSTEIN R. Rio P, MADREPERLA SA, ET AL: Promoter deletion and loss of retinoblastoma gene expression in human prostate carcinoma. Proc Natl Acad Sci USA 81:1162-1166, 1990 (12) SHEVRIN DH, KUKREJA SC, GHOSH L. ET AL: Development of skeletal
metastasis by human prostate cancer in athymic nude mice. Clin Exp Metastasis 6:401^*09, 1988 (13) STEPHENSON RA, DINNEY CPN, GOHJI K. ET AL: Metastatic model for
human prostate cancer using orthotopic implantation in nude mice. J Natl Cancer Inst 84:951-957, 1992 (14) Xu H-J. SUMEGI J. Hu S-X. ET AL: Intraocular tumor formation of RB reconstituted retinoblastoma cells. Cancer Res 51:4481^4485. 1991 (15) MUNCASTER MM, COHEN BL, PHILLIPS RA, ET AL: Failure of RBI to
reverse the malignant phenotype of human tumor cells lines. Cancer Res 52:654-661, 1992
Proper designation of race or ethnicity in medical records requires diligent recording by hospital personnel. Increasingly, medical records do not contain such information, which makes the determination of racial differences in rates progressively more difficult. When race is noted in the medical record, one might assume that the information was self-declared by the patient or a family member. As Frost et al. (/) point out, their data suggest that much of the racial information in these records is based on observation of physical appearance by medical personnel. Appearance alone, however, may lead to substantial misclassification, especially among persons of mixed parentage. In one study (2), 32.3% of self-reported Asians/Pacific Islanders and 70% of self-reported Native Americans/Alaska
Received May 14, 1992; accepted May 15, 1992. Cancer Research Center of Hawaii. Epidemiology Program. University of Hawaii at Manoa. Honolulu. 'Correspondence to: Laurence N. Kolonel, M.D, Ph.D. Cancer Research Center of Hawaii, University of Hawaii at Manoa, Rm. 407. 1236 Lauhala St.. Honolulu, HI 96813.
EDITORIALS 915
Downloaded from http://jnci.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
injected into the tail vein during clamping of the inferior vena :ava (12); however, further studies will be required to determine how representative this model will be for study of the metastatic phenotype of prostate cancer. A report by Stephenson et al. (13) in this issue of the Journal describes a new metastatic model for human prostate cancer using orthotopic implantation in nude mice. This innovative approach has been used successfully by other laboratories to establish cell lines from human tumors of other histologies. Of particular relevance to the studies of Stephenson et al., Drthotopic implantation has been shown to result in increased rates of metastasis when compared with ectopic (usually sub:utaneous) implantation. The prostate cancer orthotopic transplantation model may provide a much needed tool not only for studying metastasis but also for evaluating the molecular genetic events associated with initiation and progression of prostate cancer. For example, a number of investigators have shown that introduction of the wild-type RB gene into RB-defective cells resulted in a loss of tumorigenicity when the clones were implanted subcutaneously in nude mice. This result was seen in cell lines derived from several different histologies. However, when retinoblastoma cells were transfected with the wild-type RB gene and then implanted into nude mice either ectopically (subcutaneously) or orthotopically (i.e., intraocularly), the ectopic sites were found to have no tumor, while tumor growth was noted in the implanted eye (14,15). These observations suggest that the specific microenvironment at the injection site may play as important a role as the tumorigenicity of the implanted cells in determining whether an implanted tumor will take. The orthotopic transplantation model may thus be extremely valuable for establishing the role of candidate prostate carcinoma susceptibility genes in tumorigenicity, as well as the role of other tumor suppressor genes in the progression of this malignancy. Increasing our understanding of the molecular mechanisms underlying the diverse clinical behavior of prostate carcinoma
914
Received May 15, 1992; accepted May 18, 1992. W. M. Linehan, J. P. Long, J. R. Gnarra (Surgery Branch, Division of Can cer Treatment), P- S. Steeg (Laboratory of Pathology, Division of Cancer Biol ogy. Diagnosis, and Centers), National Cancer Institute, Bethesda, Md. Correspondence to: W. Marston Linehan, M.D., Bldg. 10, Rm. 2B47 National Institutes of Health. Bethesda, MD 20892.
Journal of the National Cancer Institute
Downloaded from http://jnci.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
Cancer of the prostate is now recognized as the most common cancer in men. The estimated prevalence of prostate carcinoma in the United States is striking: Autopsies performed on men 50 years of age or older who died from other causes have revealed that 30%-50% of the individuals harbored microscopic foci of prostate carcinoma (/). It is projected that more than 130000 new cases of prostate cancer will be diagnosed in the United States this year and that 32000 men will die of the disease. For reasons that are not yet well understood, Black American men are nearly twice as likely to develop this form of cancer as White American men (2). Continued improvements in diagnostic and surgical techniques have led to more effective management of patients with localized prostate carcinoma. However, for patients with advanced-stage disease, the situation is more grave. Approximately 80% of patients with advanced prostate carcinoma will develop skeletal metastases and, for these individuals, there are currently only minimally effective forms of therapy. The molecular mechanisms underlying the etiology and progression of prostate cancer remain to be elucidated. Although abnormalities in growth factor-mediated regulation of prostate cancer are the subject of intense investigation, the autocrine, paracrine, and endocrine effects of prostate carcinomaproduced factors have not yet been fully characterized. Recent studies suggest a role for genetic factors in the development of prostate cancer. Several groups have demonstrated that First-degree relatives of men with prostate cancer are two to three times more likely to develop this disease than the general population. Steinberg et al. (3) showed that men with two or three First-degree relatives affected with prostate cancer had a Fivefold or 11-fold increased risk, respectively, of developing prostate cancer themselves. In addition, Carter et al. (4) recently showed that this familial clustering follows a pattern of mendelian inheritance. These and other studies suggest the existence of a heritable prostate cancer susceptibility gene(s) that may play a role in initiation and/or progression of the disease. IdentiFication of such a gene(s) will require extensive molecular analyses, including cytogenetic characterization of human prostate tumors to identify and map any consistent chromosomal abnormalities; linkage studies using restriction fragment length polymorphism (RFLP) analyses to identify speciFic alleles involved
in prostate cancer; chromosomal transfer studies to reconstituti lost alleles and suppress tumorigenesis; and characterization o expression in prostate carcinoma of known oncogenes an< tumor suppressor genes. Although some progress along these lines has been made research has been hampered by the limited availability o human prostate carcinoma tissue. It is hoped that the recen support from the National Institutes of Health for establishing ; human tumor bank will alleviate this problem. In addition, i has proven difficult to establish suitable cell lines because eel cultures from primary human prostate carcinoma tissue oftei become overgrown with normal, diploid (typically stromal cells. As a result, there are currently only four prostate car cinoma cell lines available for study. Using a different in vim approach, Peehl and co-workers (5) have demonstrated th( value of short-term explant cultures for cytogenetic and othe analyses of prostate cancer; however, this promising technique has not yet achieved widespread use. Despite these practical difficulties, early investigations of tht molecular genetics of prostate cancer have yielded encouraging results. In independent analyses of human prostate carcinorm tissue, Bergerheim and co-workers (6) have described allelic deletions on chromosomes 8, 10, and 16, and Carter et al. (7 have demonstrated loss of heterozygosity on chromosomes 1C and 16. In addition, recent work (8) suggests that the reintroduction of a normal chromosome 11 into a prostate carcinoma cell line can suppress tumorigenicity. Studies in animal models have demonstrated a potentially signiFicant role of oncogenes such as ras and myc in the progression of prostate cancer (9). The p53 tumor suppressor gene has been shown to be defective or missing in two prostate carcinoma cell lines, and transfection of the wild-type p53 gene into those cells generated clones displaying diminished growth in colony-forming assays ir vitro. Further, aberrant expression of the retinoblastoma susceptibility gene (RB) was seen in DU145 cells, one of three prostate carcinoma lines evaluated. Retroviral transduction ol the wild-type RB gene into this cell line diminished, but did not fully abrogate, tumorigenicity of the cells in nude mice. Finally, preliminary studies have demonstrated abnormalities in the expression of p53 and RB proteins in human prostate carcinomas (10,11). Like the molecular genetic studies, study of the metastatic phenotype in prostate cancer has been limited by the lack of a well-characterized tumor bank and of suitable in vitro and in vivo models. Because of the slow doubling time of this malignancy, molecular characterization of metastases will require tissue from patients with years of follow-up. Little is known about the metastatic properties in vivo of the four available prostate carcinoma cell lines. In particular, no good model exists which reproduces the propensity of prostate cancer to metastasize to bony structures. PC-3 cells have been reported to induce vertebral metastases in nude mice when they are
Racial Variation in Cancer Incidence: Fact or Artifact? Laurence N. Kolonel, * Marc T. Goodman Accuracy in determining cancer incidence rates for ethnic minorities is of fundamental importance to researchers, health service providers, and policy-makers responsible for the allocation of limited health care resources. Thus, the report by Frost et al. (/) in this issue of the Journal raises serious issues for discussion. In their report, the authors show that a very high percentage of Native Americans in the population-based Surveillance, Epidemiology, and End Results (SEER) registry in the Seattle-Puget Sound area are misclassified, largely as White. Vol. 84, No. 12, June 17, 1992
is of paramount importance. Continued intensive efforts in this area will lead to more efficient diagnosis and to more effective forms of therapy for patients with this disease.
References (/) CHODAK GW: Early detection and screening for prostatic cancer. Urology 34 (suppl 4): 10. 1989 (2) MEIKLE AW. SMITH JA: Epidemiology of prostate cancer. In Early Detection and Treatment of Localized Carcinoma of the Prostate (Smith JA. ed). Philadelphia: Saunders. 1990, pp 709-718 (3) STEINBERG GD, CARTER BS. BEATY TH, ET AL: Family history and the
risk of prostate cancer. Prostate 17:337-347. 1990 (4) CARTER BS, BEATY TH, STEINBERG GD. ET AL: Mendelian inheritance of
familial prostate cancer. Proc Natl Acad Sci USA 89:3367-3371. 1992 (5) PEEHL DM, WONG ST. STAMEY TA: Cytostatic effects of suramin on
prostate cancer cells cultured from primary tumors. J Urol 145:624-630. 1991 (6) BERGERHEIM US. KUNIMI K, COLLINS VP. ET AL: Deletion mapping of
chromosomes 8, 10. and 16 in human prostatic carcinoma. Genes Chromosom Cancer 3:215-220, 1991 (7) CARTER BS, EWING CM, WARD WS, ET AL: Allelic loss of chromosomes
16q and lOq in human prostate cancer. Proc Natl Acad Sci USA 87:8751-8755, 1990 (8) BOVA GS, ICHIKAWA T, ISAACS JT. ET AL. Insertion of human chromo-
somes 8 and 11 into human prostate cancer cell lines using microcell transfer technique. J Urol 147 (suppl):2l5A. 1992 (9) THOMPSON TC, SOUTHGATE J, KITCHNER G, ET AL: Multistage car-
cinogenesis induced by ras and myc oncogenes in a reconstituted organ. Cell 56.917-930. 1989 (10) EFFERT PJ. NEUBAUER A. WALTHER PJ. ET AL: Alterations of the p53 gene
are associated with the progression of a human prostate carcinoma. J Urol 147:789-793, 1992 (//) BOOKSTEIN R. Rio P, MADREPERLA SA, ET AL: Promoter deletion and loss of retinoblastoma gene expression in human prostate carcinoma. Proc Natl Acad Sci USA 81:1162-1166, 1990 (12) SHEVRIN DH, KUKREJA SC, GHOSH L. ET AL: Development of skeletal
metastasis by human prostate cancer in athymic nude mice. Clin Exp Metastasis 6:401^*09, 1988 (13) STEPHENSON RA, DINNEY CPN, GOHJI K. ET AL: Metastatic model for
human prostate cancer using orthotopic implantation in nude mice. J Natl Cancer Inst 84:951-957, 1992 (14) Xu H-J. SUMEGI J. Hu S-X. ET AL: Intraocular tumor formation of RB reconstituted retinoblastoma cells. Cancer Res 51:4481^4485. 1991 (15) MUNCASTER MM, COHEN BL, PHILLIPS RA, ET AL: Failure of RBI to
reverse the malignant phenotype of human tumor cells lines. Cancer Res 52:654-661, 1992
Proper designation of race or ethnicity in medical records requires diligent recording by hospital personnel. Increasingly, medical records do not contain such information, which makes the determination of racial differences in rates progressively more difficult. When race is noted in the medical record, one might assume that the information was self-declared by the patient or a family member. As Frost et al. (/) point out, their data suggest that much of the racial information in these records is based on observation of physical appearance by medical personnel. Appearance alone, however, may lead to substantial misclassification, especially among persons of mixed parentage. In one study (2), 32.3% of self-reported Asians/Pacific Islanders and 70% of self-reported Native Americans/Alaska
Received May 14, 1992; accepted May 15, 1992. Cancer Research Center of Hawaii. Epidemiology Program. University of Hawaii at Manoa. Honolulu. 'Correspondence to: Laurence N. Kolonel, M.D, Ph.D. Cancer Research Center of Hawaii, University of Hawaii at Manoa, Rm. 407. 1236 Lauhala St.. Honolulu, HI 96813.
EDITORIALS 915
Downloaded from http://jnci.oxfordjournals.org/ at Northern Arizona University on May 28, 2015
injected into the tail vein during clamping of the inferior vena :ava (12); however, further studies will be required to determine how representative this model will be for study of the metastatic phenotype of prostate cancer. A report by Stephenson et al. (13) in this issue of the Journal describes a new metastatic model for human prostate cancer using orthotopic implantation in nude mice. This innovative approach has been used successfully by other laboratories to establish cell lines from human tumors of other histologies. Of particular relevance to the studies of Stephenson et al., Drthotopic implantation has been shown to result in increased rates of metastasis when compared with ectopic (usually sub:utaneous) implantation. The prostate cancer orthotopic transplantation model may provide a much needed tool not only for studying metastasis but also for evaluating the molecular genetic events associated with initiation and progression of prostate cancer. For example, a number of investigators have shown that introduction of the wild-type RB gene into RB-defective cells resulted in a loss of tumorigenicity when the clones were implanted subcutaneously in nude mice. This result was seen in cell lines derived from several different histologies. However, when retinoblastoma cells were transfected with the wild-type RB gene and then implanted into nude mice either ectopically (subcutaneously) or orthotopically (i.e., intraocularly), the ectopic sites were found to have no tumor, while tumor growth was noted in the implanted eye (14,15). These observations suggest that the specific microenvironment at the injection site may play as important a role as the tumorigenicity of the implanted cells in determining whether an implanted tumor will take. The orthotopic transplantation model may thus be extremely valuable for establishing the role of candidate prostate carcinoma susceptibility genes in tumorigenicity, as well as the role of other tumor suppressor genes in the progression of this malignancy. Increasing our understanding of the molecular mechanisms underlying the diverse clinical behavior of prostate carcinoma
