Association Between BRCA1 Mutations and Ratio of Female to Male Births in Offspring of Families with Breast Cancer, Ovarian Cancer, Or Both

BRIEF REPORT

Association Between BRCA1 Mutations and Ratio of Female to Male Births in Offspring of Families With Breast Cancer, Ovarian Cancer, or Both

Miguel de la Hoya, PhD Context Defects in X-chromosome inactivation distort sex ratio in mice. The BRCA1 Juan M. Fernańdez, BS gene is also involved in X-chromosome inactivation, suggesting the possibility that Alicia Tosar, PhD some sex-ratio distortion may be associated with BRCA1-related human cancer syndromes. Javier Godino, BS Objective To determine whether BRCA1 mutations are associated with distortion Ana Sańchez de Abajo, BS of the sex ratio of births in families with breast cancer, ovarian cancer, or both. Jose A. Vidart, MD, PhD Design and Setting Analysis of germline mutations in participants from Spain who had been screened for BRCA between 1998 and 2002. Pedro Pe´rez-Segura, MD, PhD Participants Sixty-eight families with at least 3 breast cancer cases or ovarian can- Eduardo Dıáz-Rubio, MD, PhD cer cases, or both types of cancer in 2 generations (germline mutations: BRCA1, n=17; Trinidad Calde´s, PhD BRCA2, n=15; and BRCA unrelated, n=36). An average of 4 relatives per family were tested for the corresponding BRCA mutation. HE BIOLOGY OF THE BREAST AND Main Outcome Measure Male and female births registered in breast and/or ovar- ovarian cancer susceptibility ian pedigrees tested for the presence of BRCA1 and BRCA2 germline mutations. genes BRCA1 and BRCA2 is not Results Of BRCA1-related breast and/or ovarian cancer pedigrees, there was a 2-fold well understood. These genes excess of female births (218 female vs 109 male births). Of BRCA2-related or BRCA- Tencode proteins likely involved in DNA unrelated breast and/or ovarian cancer pedigrees, there was not an excess of female repair, transcription regulation, and cell births (175 female/150 male and 344 female/315 male, respectively). Of 327 BRCA1 cycle and checkpoint control.1 Except births, 218 (67%) were female births compared with 54% among BRCA2 pedigrees for cancer susceptibility, no other phe- (175/327; PϽ.001) and 52% among BRCA-unrelated pedigrees (344/659; PϽ.001). notype associated with BRCA1 muta- Female births increased in the offspring of BRCA1 carriers compared with BRCA2 car- tions has been reported in humans. In riers (67% vs 52%; P=.004). this study, we analyzed the sex ratio in Conclusion In these families with breast and/or ovarian cancer, mutations in BRCA1 the offspring of families with BRCA1 but not BRCA2 were associated with a sex ratio skewed against male births. and BRCA2 mutation carriers. JAMA. 2003;290:929-931 www.jama.com

METHODS tained from the local ethics commit- BRCA1-orBRCA2-positive family). Mu- We analyzed the sex ratio in 68 breast tee. Of the 68 pedigrees, our cohort in- tation screening methods have been de- and/or ovarian cancer pedigrees be- cluded 17 BRCA1-related, 15 BRCA2- scribed elsewhere.1 For the overall sex tween 1998 and 2002 who were previ- related, and 36 BRCA-unrelated ratio of births, we considered all male ously screened for germline muta- families. All mutations are considered and female births reported in each pedi- tions in both BRCA1 and BRCA2. These as pathogenic on the Breast Cancer In- Spanish families were selected for ge- formative Core Web site (http://www Author Affiliation: Molecular Oncology Unit (Drs de la Hoya, Tosar, and Calde´ s, Messrs Ferna´ ndez and netic testing because they have at least .nhgri.gov/Intramural_research Godino, and Ms Sa´ nchez de Abajo) and Depart- 3 breast and/or ovarian cancer cases re- /Lab_transfer/Bic/; mutation ments of Gynecology (Dr Vidart) and Clinical Oncol- ogy (Drs Pe´ rez-Segura and Dıáz-Rubio), Hospital ported in 2 generations. Participants descriptions appear in TABLE 1 and Clıńico San Carlos, Madrid, Spain. signed an informed consent to have TABLE 2). A total of 121 relatives have Corresponding Author and Reprints: Trinidad Cal- de´ s, PhD, Laboratory of Molecular Oncology, Hos- their blood tested for BRCA1 and/or been tested for the corresponding mu- pital Clıńico San Carlos, Martin Lagos s/n, Madrid BRCA2. Approval for the study was ob- tation (on average, 4 relatives per 28040, Spain (e-mail: [email protected]).

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Table 1. Sex Ratio in BRCA1 Pedigrees Figure. Sex Ratio of Births Observed in 68 Total Births* Carrier Offspring† Breast and/or Ovarian Cancer Pedigrees

Family Mutation Male Female Male Female 80 Female Births 2 IVS20 + 1G/A 3 13 3 10 70 Male Births 3 157delCT 2 13 2 5 60 4 IVS18-1G/C 4 11 3 8 5 1370insATCT 0 8 0 7 50 7 A1708E 3 12 1 4 40

42 157delCT 4 8 2 2 Percentage 30 61 A1708E 7 15 1 0 20 121 A1708E 9 16 10 19 10 152 IVS18 + 3ϾC 514211 0 156 IVS6-1C/T 11 30 8 15 BRCA1 BRCA2 Negative 158 1567del11 20 12 11 11 Mutation Status 160 IVS18+3AϾC7 7 5 4 No. of Total 163 1181delGT 4 4 2 1 Births (Pedigrees) 327 (17) 325 (15) 659 (36) 184 185delAG 12 18 6 13 185 A1708E 6 10 4 6 Error bars indicate 95% confidence intervals. 195 185delAG 8 14 2 10 223 185delAG 4 13 3 7 female vs 150 male births), and Total 109 218 65 133 BRCA-unrelated pedigrees (344 *All births indicated in the pedigree (only BRCA1-related lineage). †Carriers confirmed by genetic testing or nontested obligated carriers. female vs 315 male births) were close to the expected 50% sex ratio (Table 2). The excess of female births Table 2. Sex Ratio in BRCA2 Pedigrees observed in BRCA1 pedigrees is sig- Total Births* Carrier Offspring† nificant when compared with BRCA2 Family Mutation Male Female Male Female pedigrees (67% vs 54%; ␹2 =11.19; 8 8234del23 11 11 7 8 PϽ.001) or BRCA-unrelated pedigrees 12 6503delTT 5 14 4 5 (67% vs 52%; ␹2 =18.66; PϽ.001) 16 5804delAAAA 14 10 9 4 (FIGURE). The sex ratio was also 106 E 3096 X 14 26 1 1 skewed against male births in the off- 110 936delAAAC 16 15 7 5 spring of BRCA1 carriers: 133 female 126 3492insTT 11 13 9 13 (67%) vs 65 male (33%) (Table 1). 139 8294insTT 5 6 5 6 On the other hand, the offspring of 171 3036delACAA 5 4 4 2 BRCA2 carriers have shown no evi- 172 Ser 1955 X 0 3 0 3 dence of sex-ratio abnormalities: 84 178 3036delACAA 6 7 2 5 (52%) female births vs 77 (48%) male 179 5373delTATG 11 9 6 4 births (Table 2). These data support 182 E 1308 X 10 17 6 13 an association between BRCA1 defects 186 Ser 1955 X 12 10 6 8 (but not BRCA2 defects) and sex ratio 192 Tyr 3006 X 22 13 12 11 skewed against male births in the off- 197 1709 delGATTA 8 17 7 9 spring (␹2=8.35; P=.004). Total 150 175 85 97 *All births indicated in the pedigree (only BRCA2-related lineage). †Carriers confirmed by genetic testing or nontested obligated carriers. COMMENT Taken together, our data confirm a sex-ratio distortion associated with gree. To determine the sex ratio of Centers for Disease Control and Pre- BRCA1 mutations. Our findings were births in the offspring of carriers, we vention, Atlanta, Ga). unexpected, but may be partly considered either BRCA carriers con- explained by recent data suggesting firmed by genetic testing (n=56) or RESULTS both a link between X-chromosome nontested obligated carriers (n=26). Overall, BRCA1 pedigrees were inactivation (XCI) and sex ratio2 and The ␹2 test was used in all statistical strongly skewed against male births: a role for BRCA1 in XCI.3,4 Although analyses and was performed using Epi 218 females vs 109 males (Table 1). XCI is a poorly understood biological Info statistical software (Version 5.01; By contrast, BRCA2 pedigrees (175 process, XIST and TSIX genes (acting

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on chromosome inactivation) are Defects in XCI may distort sex ratio sex ratio skewed against male births known to have opposite roles in XCI as has been shown in homozygous TSIX in the offspring of mutation carriers. regulation. In current XCI models, mutant mice.2 Lee3 demonstrated that XIST RNA accumulation along an X by abolishing TSIX activity, the sex ra- Author Contributions: Study concept and design: de la Hoya, Caldes. chromosome promotes silencing tio is skewed against female births. One Acquisition of data: de la Hoya, Ferna´ ndez, Tosar, along that chromosome. The expres- hypothesis is that BRCA1 haploinsuf- Godino, Sa´ nchez de Abajo, Pe´ rez-Segura, Caldes. Analysis and interpretation of data: de la Hoya, Vidart, sion of TSIX (its antisense counter- ficiency affects the ability of XIST RNA Pe´ rez-Segura, Diaz-Rubio, Caldes. part) blocks XIST accumulation and to accumulate along the X chromo- Drafting of the manuscript: de la Hoya, Caldes. Critical revision of the manuscript for important in- therefore inhibits XCI. An association some, mimics XIST inhibition, and pro- tellectual content: Ferna´ ndez, Tosar, Godino, Sa´ nchez between BRCA1 and XCI dysfunction duces an opposite sex-ratio distor- de Abajo, Vidart, Pe´ rez-Segura, Diaz-Rubio, Caldes. was first described in patients with tion; ie, a sex ratio skewed against male Statistical expertise: de la Hoya. Obtained funding: de la Hoya, Diaz-Rubio, Caldes. BRCA1 germline mutations and/or births. Administrative, technical, or material support: Fern- ovarian cancer.3 Recently, a direct role In conclusion, we report, for the a´ ndez, Tosar, Godino, Sa´ nchez de Abajo, Vidart, Pe´ rez- Segura, Diaz-Rubio. for BRCA1 in XCI has been suggested first time to our knowledge, a pheno- Study supervision: Caldes. as XIST RNA concentration in the type associated with BRCA1 but not Funding/Support: This work was supported by Aventis, Fondo de Investigacio´ n Sanitaria grant 01/ inactive X chromosome is dependent BRCA2 or BRCA-unrelated breast 3040, and Comunidad de Madrid grant 08.1/0018.1/ on BRCA1 status.5 and/or ovarian cancer, resulting in a 2000.

REFERENCES 1. Venkitaraman AR. Cancer susceptibility and the lies: implications for genetic testing. Int J Cancer. 2002; tween nonrandom X-chromosome inactivation and functions of BRCA1 and BRCA2. Cell. 2002;108:171- 97:466-471. BRCA1 mutation in germline DNA of patients with ovar- 182. 3. Lee JT. Homozygous TSIX mutant mice reveal a sex- ian cancer. J Natl Cancer Inst. 1999;91:339-346. 2. de la Hoya M, Osorio A, Godino J, et al. Associa- ratio distortion and revert to random X-inactivation. 5. Ganesan S, Silver DP, Greenberg RA, et al. BRCA1 tion between BRCA1 and BRCA2 mutations and can- Nat Genet. 2002;32:195-200. supports XIST RNA concentration on the inactive X cer phenotype in Spanish breast/ovarian cancer fami- 4. Buller RE, Sood AK, Lallas T, et al. Association be- chromosome. Cell. 2002;111:393-405.

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