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Genetic analysis of familial and multiple malignancies of endometrial cancer
International Journal of Gynecology & Obstetrics 66 Ž1999. 149]153
Article
Genetic analysis of familial and multiple malignancies of endometrial cancer K. Kobayashi 1, S. Sagae1,U , T. Takeda, M. Sugimura, Y. Nishioka, R. Kudo Department of Obstetrics and Gynecology, Sapporo Medical Uni¨ ersity, School of Medicine, Sapporo, Hokkaido, Japan Received 23 July 1998; received in revised form 2 April 1999; accepted 8 April 1999
Abstract The presence of the positive replication errors ŽRER. phenotype in familial and multiple primary malignancies of endometrial cancer, and its association with a poor prognosis was examined. We analyzed 40 endometrial cancers for RER. Eight endometrial cancers with the RERŽq. phenotype at multiple microsatellite loci were detected. The presence of the RERŽq. phenotype was higher than in non-familial malignancies. None of the eight cases with the RERŽq. phenotype involved multiple primary malignancies; however these patients had shorter survival times. In this study, we suggest that RER examination in endometrial cancer may be useful for establishing a diagnosis of a familial malignancy, and for predicting a poor prognosis. Q 1999 International Federation of Gynecology and Obstetrics. Keywords: Multiple primary malignancies; Familial malignancies; Replication error; Gynecologic cancers
1. Introduction We established that both endometrial and ovarian cancers frequently have multiple primary and familial malignancies w1x. Hereditary non-polypo-
U
Corresponding author. Tel.: q81-11-611-2111; fax: q8111-614-0860. 1 These authors contributed equally to this study.
sis colorectal cancer ŽHNPCC. is a familial predisposition to colorectal cancer and extracolonic cancers of the stomach, pancreas, ovary and endometrium w2]5x. Endometrial cancer frequently occurs in younger woman of HNPCC families w5x. Recent studies report that tumors in patients with HNPCC w6]10x showed frequent somatic mutations in simply repeated sequences, including microsatellite instability at dinucleotide repeats. The microsatellite instability is called the positive
0020-7292r99r$20.00 Q 1999 International Federation of Gynecology and Obstetrics. PII: S 0 0 2 0 - 7 2 9 2 Ž 9 9 . 0 0 0 6 6 - 1
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153
150
replication error ŽRER. phenotype. Furthermore, we have reported on the frequency of RERŽq. in endometrial cancer w11x. In the present study, we examine the presence of the positive error replication phenotype in familial and multiple primary malignancies of endometrial cancer.
2. Patients and methods Forty endometrial cancers from patients who received surgery at Sapporo Medical University were studied. Histological typing of individual tumors was performed according to the WHO classification w12x, and surgical stage was determined by the International Federation of Gynecology and Obstetrics ŽFIGO. staging w13x, respectively. For familial malignancies, Narod’s criteria were employed to patients with ovarian cancer w14x. Criteria of Warren and Gates were applied to multiple primary malignancies w15x. Fisher’s test and the Cox]Mantel test were applied to the significant differences of the frequency with which alterations occurred in different categories. Differences of P- 0.05 were considered significant.
phenotype was more often seen, to a significant degree, in familial malignancies Ž5r8. compared with non-familial malignancies Ž3r32; P- 0.05, Table 1.. To clarify the value of RERŽq. phenotype, we subdivided endometrial cancers into three groups, according to onset age. In the younger group Žage - 50., we found the RERŽq. phenotype in familial malignancies only Ž2r3, Table 2.. In the middle group Ž50 - age - 60., we found the phenotype in both familial Ž2r4. and non-familial Ž2r14. malignancies. In the older group Ž60 age., we found the phenotype in both familial Ž1r1. and non-familial malignancies Ž1r14.. We observed that the rate of death due to endometrial cancer tended to be high Ž4r8. in patients with the RERŽq. phenotype ŽTable 1.. Mortality was high in both the early and advanced stages ŽTable 3.. Furthermore, we found that the endometrial cancer patients with the RERŽq. phenotype had poor survival times ŽFig. 1.; their median survival time Ž44.1 months. was shorter compared with the patients that did not have the phenotype Ž51.7 months..
4. Discussion Genetic andror hereditary findings of tumors have been reported in hereditary non-polyposis
3. Results We found that the RERŽq. phenotype at multiple microsatellite loci was found in eight Ž20%. of 40 cases of endometrial cancer, and that the Table 1 Replication errors in endometrial cancers among different groups with clinical parameters a
Familial history Positive Negative Sur¨ i¨ al data DOD Alive a U
RER Žq.
RER Žy.
5 3
3 U 29
4 4
4 28
DOD, Died of disease. Diffferences of significance P- 0.05.
U
Table 2 Association with replication errors for familial malignancies among different age groups RER Žq. Younger Ž- 50. Familial history Positive Negative Middle age Ž50 F age - 60. Familial history Positive Negative Older ŽF 60. Familial history Positive Negative
RER Žy.
2 0
1 4
2 2
2 12
1 1
0 13
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153 Table 3 Association with replication errors for survival data among early and advanced endometrial cancers
Early stage ŽI]II. Survival data DOD Alive Advanced stage ŽIII]IV. Survival data DOD Alive
RER Žq.
RER Žy.
2 2
2 15
2 2
2 13
colorectal cancer ŽHNPCC. and breastrovarian cancer w6,7,16x. During the last decade, developments of cancer have been identified genetically. HNPCC is a familial predisposition to colorectal cancer, and to extracolonic cancers of the stomach, pancreas, ovary and endometrium w2]5x, involving some disorder of the gene mismatch repair system. Recent studies reported that tumors in patients with HNPCC showed frequent somatic mutations in simply repeated sequences w6]10x, including microsatellite instability at dinucleotide repeats. The microsatellite instability is called the replication error ŽRER. positive phenotype. Previously, we detected RERŽq. phenotype in
151
eight of 40 endometrial cancers. In the present study, we observed that the occurrence of RERŽq. phenotype in familial malignancies was higher than that in non-familial malignancies. Further, we found that the tendency was observed in all age groups. We found a significant presence of the RERŽq. phenotype in patients that died of endometrial cancer, as other data have shown w17x. This mortality rate was seen in both early and advanced stages. Due to the small number of patients, however, we could not determine if presence of the phenotype was a useful screening of familial malignancies, and independent prognostic factor. More definitive examinations are needed using larger numbers of patients with endometrial cancer. In gastric and colorectal cancers, there are no significant differences between RERŽq. phenotype and familial history of cancers, exclusive of HNPCC families w8]10,18x, and in these cancers, patients with RERŽq. phenotype showed longer survival times w18,19x. Horii et al. reported that the RERŽq. phenotype was found in nearly 90% of multiple primary cancers w20x. In this paper by Horii et al., the multiple primary malignancies with RERŽq. were mainly found in cancers of digestive organs: the stomach, colon, and esophagus, but they did not
Fig. 1. Cause-specific survival for 40 patients in relation to RER. RERŽy.: n s 32; median survival, 51.7 months; RERŽq.: n s 8; median survival, 44.1 months Ždeath from endometrial cancer; Kaplan]Meier plot..
152
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153
include any of the gynecologic cancers. We did not find the RERŽq. phenotype in multiple primary malignancies of endometrial cancer. Another risk factor of clinical and genetic backgrounds in familial and multiple primary malignancies has been reported. The BRCA1 gene is related to susceptibility to breastrovarian cancer w16x, and the gene shows ovarian carcinogenesis, which results in a hereditary or sporadic form of ovarian cancer. BRCA1 gene mutations are found in approximately 5% of patients with ovarian cancer diagnosed before the age of 70 w21x. We previously reported on the germline mutation of the BRCA1 gene in ovarian cancer w22x. Additionally, we have encountered four patients with a hereditary form of ovarian cancer, including a patient with site-specific ovarian cancer; these patients had respective germline mutations of BRCA1 gene. However, Japanese patients with BRCA1-gene mutations often have no evident familial history of breastrovarian cancer w22,23x. Further studies of germline mutation of the BRCA1 gene in hereditary gynecologic cancers must be conducted. In the present study, our results imply that RERŽq. phenotype examination in endometrial cancer may be an efficient method for screening familial malignancies, and this testing may be able to predict a poor prognosis. However, we suggest that findings of high risk confirmation in familial malignancies cannot be applied to multiple primary malignancies, in contrast to the case of digestive organs.
Acknowledgments This work was supported by a grant-in-aid from the Ministry of Education, Science, and Culture of Japan. References w1x Takeda T, Sagae S, Koizumi M et al. Multiple primary malignancies in patients with gynecologic cancer. Int J Gynecol Cancer 1995;5:34]39. w2x Lynch HT, Shaw MW, Magnuson CW, Larsen AL, Krush AJ. Hereditary factors in two large Midwestern kindreds. Arch Int Med 1996;117:206]212.
w3x Lynch HT, Smyrk T, Watson P et al. Hereditary colorectal cancer. Semin Oncol 1991;18:337]366. w4x Lynch HT, Smyrk TC, Watson P et al. Genetics, natural history, tumor spectrum, and pathology of hereditary non-polyposis colorectal cancer: an undated review. Gastroenterology 1993;104:1535]1549. w5x Watson P, Lynch HT. Extracolonic cancer in hereditary non-polyposis colorectal cancer. Cancer 1993;71: 677]685. w6x Aalton LA, Peltomaki P, Leach FS et al. Clues to the pathogenesis of familial colorectal cancer. Science 1993;260:812]816. w7x Innove Y, Peinado MA, Malkhosyan S, Shibata D, Perucho M. Ubiquitous somatic mutation in simple repeated sequences reveal a new mechanism for colonic carcinogenesis. Nature ŽLondon. 1993;363:558]561. w8x Brassett C, Joyce JA, Froggatt NJ et al. Microsatellite instability in early onset and familial colorectal cancer. J Med Genet 1996;33:981]985. w9x Jass JR, Cottier DS, Jeevaratham P et al. Diagnostic use of microsatellite instability in hereditary non-polyposis colorectal cancer. Lancet 1995;346:1200]1201. w10x Kim H, Jen J, Vogelstein B, Hamilton SR. Clinical and pathological characteristics of sporadic colorectal carcinomas with DNA replication errors in microsatellite sequences. Am J Pathol 1994;145:148]156. w11x Kobayashi K, Sagae S, Kudo R, Saito H, Koi S, Nakamura Y. Microsatellite instability in endometrial carcinomas. Genes Chromosomes Cancer 1995;14:128]132. w12x Scully RE, Bonfiglo TA, Kurman RJ, Silverberg SG, Wilkinson EJ. Histological typing of female genital tract tumors. 2nd ed. International histological classification of tumors. World Health Organization. Springer-Verlag, 1996. w13x FIGO Stages-1988 Revision. Gynecol Oncol. w14x Narod SA, Feuteun J, Lynch HT. Familial breast] ovarian cancer locus on chromosome 17q12]23. Lancet 1991;338:82]83. w15x Warren S, Gates O. Multiple primary malignant tumors: survey of literature and statistical study. Am J Cancer 1932;16:1358]1414. w16x Miki Y, Swensen J, Shattuck-Eidens D et al. A strong candidate for the breast and ovarian cancer susceptibility gene BRCA1. Science 1994;266:66]71. w17x Caduff RF, Johnston CM, Svoboda-Newman SM, Poy EL, Frank TS. Clinical and pathological significance of microsatellite instability in sporadic endometrial carcinoma. Am J Pathol 1996;148:1671]1678. w18x Lothe RA, Peltomaki P, Meling GI et al. Genomic instability in colorectal cancer: relationship to clinicopatological variables and family history. Cancer Res 1993;53:5849]5852. w19x dos Santos NR, Seruca R, Constancia M, Seixas M, Sobrinho-Simones M. Microsatellite instability at multiple loci in gastric carcinoma: clinicopathologic implications and prognosis. Gastroenterology 1996;110:38]44.
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153 w20x Horii A, Han H-J, Shimada M et al. Frequent replication errors at microsatellite loci in tumors of patients with multiple primary cancers. Cancer Res 1994;54: 3373]3375. w21x Stratton JF, Gayther SA, Russel P et al. Contribution of BRCA1 mutations to ovarian cancer. N Engl J Med 1997;336:1125]1130.
153
w22x Matsushima M, Kobayashi K, Emi M et al. Mutation analysis of BRCA1 gene in 76 Japanese ovarian cancer patients. Hum Mol Genet 1995;4:1953]1956. w23x Katagiri T, Emi M, Ito I et al. Mutations in the BRCA1 gene in Japanese breast cancer patients. Human Mut 1996;7:334]339.
Article
Genetic analysis of familial and multiple malignancies of endometrial cancer K. Kobayashi 1, S. Sagae1,U , T. Takeda, M. Sugimura, Y. Nishioka, R. Kudo Department of Obstetrics and Gynecology, Sapporo Medical Uni¨ ersity, School of Medicine, Sapporo, Hokkaido, Japan Received 23 July 1998; received in revised form 2 April 1999; accepted 8 April 1999
Abstract The presence of the positive replication errors ŽRER. phenotype in familial and multiple primary malignancies of endometrial cancer, and its association with a poor prognosis was examined. We analyzed 40 endometrial cancers for RER. Eight endometrial cancers with the RERŽq. phenotype at multiple microsatellite loci were detected. The presence of the RERŽq. phenotype was higher than in non-familial malignancies. None of the eight cases with the RERŽq. phenotype involved multiple primary malignancies; however these patients had shorter survival times. In this study, we suggest that RER examination in endometrial cancer may be useful for establishing a diagnosis of a familial malignancy, and for predicting a poor prognosis. Q 1999 International Federation of Gynecology and Obstetrics. Keywords: Multiple primary malignancies; Familial malignancies; Replication error; Gynecologic cancers
1. Introduction We established that both endometrial and ovarian cancers frequently have multiple primary and familial malignancies w1x. Hereditary non-polypo-
U
Corresponding author. Tel.: q81-11-611-2111; fax: q8111-614-0860. 1 These authors contributed equally to this study.
sis colorectal cancer ŽHNPCC. is a familial predisposition to colorectal cancer and extracolonic cancers of the stomach, pancreas, ovary and endometrium w2]5x. Endometrial cancer frequently occurs in younger woman of HNPCC families w5x. Recent studies report that tumors in patients with HNPCC w6]10x showed frequent somatic mutations in simply repeated sequences, including microsatellite instability at dinucleotide repeats. The microsatellite instability is called the positive
0020-7292r99r$20.00 Q 1999 International Federation of Gynecology and Obstetrics. PII: S 0 0 2 0 - 7 2 9 2 Ž 9 9 . 0 0 0 6 6 - 1
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153
150
replication error ŽRER. phenotype. Furthermore, we have reported on the frequency of RERŽq. in endometrial cancer w11x. In the present study, we examine the presence of the positive error replication phenotype in familial and multiple primary malignancies of endometrial cancer.
2. Patients and methods Forty endometrial cancers from patients who received surgery at Sapporo Medical University were studied. Histological typing of individual tumors was performed according to the WHO classification w12x, and surgical stage was determined by the International Federation of Gynecology and Obstetrics ŽFIGO. staging w13x, respectively. For familial malignancies, Narod’s criteria were employed to patients with ovarian cancer w14x. Criteria of Warren and Gates were applied to multiple primary malignancies w15x. Fisher’s test and the Cox]Mantel test were applied to the significant differences of the frequency with which alterations occurred in different categories. Differences of P- 0.05 were considered significant.
phenotype was more often seen, to a significant degree, in familial malignancies Ž5r8. compared with non-familial malignancies Ž3r32; P- 0.05, Table 1.. To clarify the value of RERŽq. phenotype, we subdivided endometrial cancers into three groups, according to onset age. In the younger group Žage - 50., we found the RERŽq. phenotype in familial malignancies only Ž2r3, Table 2.. In the middle group Ž50 - age - 60., we found the phenotype in both familial Ž2r4. and non-familial Ž2r14. malignancies. In the older group Ž60 age., we found the phenotype in both familial Ž1r1. and non-familial malignancies Ž1r14.. We observed that the rate of death due to endometrial cancer tended to be high Ž4r8. in patients with the RERŽq. phenotype ŽTable 1.. Mortality was high in both the early and advanced stages ŽTable 3.. Furthermore, we found that the endometrial cancer patients with the RERŽq. phenotype had poor survival times ŽFig. 1.; their median survival time Ž44.1 months. was shorter compared with the patients that did not have the phenotype Ž51.7 months..
4. Discussion Genetic andror hereditary findings of tumors have been reported in hereditary non-polyposis
3. Results We found that the RERŽq. phenotype at multiple microsatellite loci was found in eight Ž20%. of 40 cases of endometrial cancer, and that the Table 1 Replication errors in endometrial cancers among different groups with clinical parameters a
Familial history Positive Negative Sur¨ i¨ al data DOD Alive a U
RER Žq.
RER Žy.
5 3
3 U 29
4 4
4 28
DOD, Died of disease. Diffferences of significance P- 0.05.
U
Table 2 Association with replication errors for familial malignancies among different age groups RER Žq. Younger Ž- 50. Familial history Positive Negative Middle age Ž50 F age - 60. Familial history Positive Negative Older ŽF 60. Familial history Positive Negative
RER Žy.
2 0
1 4
2 2
2 12
1 1
0 13
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153 Table 3 Association with replication errors for survival data among early and advanced endometrial cancers
Early stage ŽI]II. Survival data DOD Alive Advanced stage ŽIII]IV. Survival data DOD Alive
RER Žq.
RER Žy.
2 2
2 15
2 2
2 13
colorectal cancer ŽHNPCC. and breastrovarian cancer w6,7,16x. During the last decade, developments of cancer have been identified genetically. HNPCC is a familial predisposition to colorectal cancer, and to extracolonic cancers of the stomach, pancreas, ovary and endometrium w2]5x, involving some disorder of the gene mismatch repair system. Recent studies reported that tumors in patients with HNPCC showed frequent somatic mutations in simply repeated sequences w6]10x, including microsatellite instability at dinucleotide repeats. The microsatellite instability is called the replication error ŽRER. positive phenotype. Previously, we detected RERŽq. phenotype in
151
eight of 40 endometrial cancers. In the present study, we observed that the occurrence of RERŽq. phenotype in familial malignancies was higher than that in non-familial malignancies. Further, we found that the tendency was observed in all age groups. We found a significant presence of the RERŽq. phenotype in patients that died of endometrial cancer, as other data have shown w17x. This mortality rate was seen in both early and advanced stages. Due to the small number of patients, however, we could not determine if presence of the phenotype was a useful screening of familial malignancies, and independent prognostic factor. More definitive examinations are needed using larger numbers of patients with endometrial cancer. In gastric and colorectal cancers, there are no significant differences between RERŽq. phenotype and familial history of cancers, exclusive of HNPCC families w8]10,18x, and in these cancers, patients with RERŽq. phenotype showed longer survival times w18,19x. Horii et al. reported that the RERŽq. phenotype was found in nearly 90% of multiple primary cancers w20x. In this paper by Horii et al., the multiple primary malignancies with RERŽq. were mainly found in cancers of digestive organs: the stomach, colon, and esophagus, but they did not
Fig. 1. Cause-specific survival for 40 patients in relation to RER. RERŽy.: n s 32; median survival, 51.7 months; RERŽq.: n s 8; median survival, 44.1 months Ždeath from endometrial cancer; Kaplan]Meier plot..
152
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153
include any of the gynecologic cancers. We did not find the RERŽq. phenotype in multiple primary malignancies of endometrial cancer. Another risk factor of clinical and genetic backgrounds in familial and multiple primary malignancies has been reported. The BRCA1 gene is related to susceptibility to breastrovarian cancer w16x, and the gene shows ovarian carcinogenesis, which results in a hereditary or sporadic form of ovarian cancer. BRCA1 gene mutations are found in approximately 5% of patients with ovarian cancer diagnosed before the age of 70 w21x. We previously reported on the germline mutation of the BRCA1 gene in ovarian cancer w22x. Additionally, we have encountered four patients with a hereditary form of ovarian cancer, including a patient with site-specific ovarian cancer; these patients had respective germline mutations of BRCA1 gene. However, Japanese patients with BRCA1-gene mutations often have no evident familial history of breastrovarian cancer w22,23x. Further studies of germline mutation of the BRCA1 gene in hereditary gynecologic cancers must be conducted. In the present study, our results imply that RERŽq. phenotype examination in endometrial cancer may be an efficient method for screening familial malignancies, and this testing may be able to predict a poor prognosis. However, we suggest that findings of high risk confirmation in familial malignancies cannot be applied to multiple primary malignancies, in contrast to the case of digestive organs.
Acknowledgments This work was supported by a grant-in-aid from the Ministry of Education, Science, and Culture of Japan. References w1x Takeda T, Sagae S, Koizumi M et al. Multiple primary malignancies in patients with gynecologic cancer. Int J Gynecol Cancer 1995;5:34]39. w2x Lynch HT, Shaw MW, Magnuson CW, Larsen AL, Krush AJ. Hereditary factors in two large Midwestern kindreds. Arch Int Med 1996;117:206]212.
w3x Lynch HT, Smyrk T, Watson P et al. Hereditary colorectal cancer. Semin Oncol 1991;18:337]366. w4x Lynch HT, Smyrk TC, Watson P et al. Genetics, natural history, tumor spectrum, and pathology of hereditary non-polyposis colorectal cancer: an undated review. Gastroenterology 1993;104:1535]1549. w5x Watson P, Lynch HT. Extracolonic cancer in hereditary non-polyposis colorectal cancer. Cancer 1993;71: 677]685. w6x Aalton LA, Peltomaki P, Leach FS et al. Clues to the pathogenesis of familial colorectal cancer. Science 1993;260:812]816. w7x Innove Y, Peinado MA, Malkhosyan S, Shibata D, Perucho M. Ubiquitous somatic mutation in simple repeated sequences reveal a new mechanism for colonic carcinogenesis. Nature ŽLondon. 1993;363:558]561. w8x Brassett C, Joyce JA, Froggatt NJ et al. Microsatellite instability in early onset and familial colorectal cancer. J Med Genet 1996;33:981]985. w9x Jass JR, Cottier DS, Jeevaratham P et al. Diagnostic use of microsatellite instability in hereditary non-polyposis colorectal cancer. Lancet 1995;346:1200]1201. w10x Kim H, Jen J, Vogelstein B, Hamilton SR. Clinical and pathological characteristics of sporadic colorectal carcinomas with DNA replication errors in microsatellite sequences. Am J Pathol 1994;145:148]156. w11x Kobayashi K, Sagae S, Kudo R, Saito H, Koi S, Nakamura Y. Microsatellite instability in endometrial carcinomas. Genes Chromosomes Cancer 1995;14:128]132. w12x Scully RE, Bonfiglo TA, Kurman RJ, Silverberg SG, Wilkinson EJ. Histological typing of female genital tract tumors. 2nd ed. International histological classification of tumors. World Health Organization. Springer-Verlag, 1996. w13x FIGO Stages-1988 Revision. Gynecol Oncol. w14x Narod SA, Feuteun J, Lynch HT. Familial breast] ovarian cancer locus on chromosome 17q12]23. Lancet 1991;338:82]83. w15x Warren S, Gates O. Multiple primary malignant tumors: survey of literature and statistical study. Am J Cancer 1932;16:1358]1414. w16x Miki Y, Swensen J, Shattuck-Eidens D et al. A strong candidate for the breast and ovarian cancer susceptibility gene BRCA1. Science 1994;266:66]71. w17x Caduff RF, Johnston CM, Svoboda-Newman SM, Poy EL, Frank TS. Clinical and pathological significance of microsatellite instability in sporadic endometrial carcinoma. Am J Pathol 1996;148:1671]1678. w18x Lothe RA, Peltomaki P, Meling GI et al. Genomic instability in colorectal cancer: relationship to clinicopatological variables and family history. Cancer Res 1993;53:5849]5852. w19x dos Santos NR, Seruca R, Constancia M, Seixas M, Sobrinho-Simones M. Microsatellite instability at multiple loci in gastric carcinoma: clinicopathologic implications and prognosis. Gastroenterology 1996;110:38]44.
K. Kobayashi et al. r International Journal of Gynecology & Obstetrics 66 (1999) 149]153 w20x Horii A, Han H-J, Shimada M et al. Frequent replication errors at microsatellite loci in tumors of patients with multiple primary cancers. Cancer Res 1994;54: 3373]3375. w21x Stratton JF, Gayther SA, Russel P et al. Contribution of BRCA1 mutations to ovarian cancer. N Engl J Med 1997;336:1125]1130.
153
w22x Matsushima M, Kobayashi K, Emi M et al. Mutation analysis of BRCA1 gene in 76 Japanese ovarian cancer patients. Hum Mol Genet 1995;4:1953]1956. w23x Katagiri T, Emi M, Ito I et al. Mutations in the BRCA1 gene in Japanese breast cancer patients. Human Mut 1996;7:334]339.