BRCA2 Polymorphic Stop Codon K3326X and the Risk of Breast, Prostate, and Ovarian Cancers

Huong D. Meeks, Huntsman Cancer Institute
Honglin Song, University of Cambridge
Kyriaki Michailidou, University of Cambridge
Manjeet K. Bolla, University of Cambridge
Joe Dennis, University of Cambridge
Qin Wang, University of Cambridge
Daniel Barrowdale, University of Cambridge
Debra Frost, University of Cambridge
Lesley McGuffog, University of Cambridge
Steve Ellis, University of Cambridge
Bingjian Feng, Huntsman Cancer Institute
Saundra S. Buys, Huntsman Cancer Institute
John L. Hopper, Melbourne School of Population and Global Health
Melissa C. Southey, University of Melbourne
Andrea Tesoriero, University of Melbourne
Paul A. James, Peter Maccallum Cancer Centre
Fiona Bruinsma, Cancer Council Victoria
Ian G. Campbell, University of Melbourne
Annegien Broeks, Antoni van Leeuwenhoek Ziekenhuis
Marjanka K. Schmidt, Antoni van Leeuwenhoek Ziekenhuis
Frans B.L. Hogervorst, The Netherlands Cancer Institute


Background: The K3326X variant in BRCA2 (BRCA2∗c.9976A>T p.Lys3326∗rs11571833) has been found to be associated with small increased risks of breast cancer. However, it is not clear to what extent linkage disequilibrium with fully pathogenic mutations might account for this association. There is scant information about the effect of K3326X in other hormonerelated cancers. Methods: Using weighted logistic regression, we analyzed data from the large iCOGS study including 76637 cancer case patients and 83796 control patients to estimate odds ratios (ORw) and 95% confidence intervals (CIs) for K3326X variant carriers in relation to breast, ovarian, and prostate cancer risks, with weights defined as probability of not having a pathogenic BRCA2 variant. Using Cox proportional hazards modeling, we also examined the associations of K3326X with breast and ovarian cancer risks among 7183 BRCA1 variant carriers. All statistical tests were two-sided. Results: The K3326X variant was associated with breast (ORw = 1.28, 95% CI = 1.17 to 1.40, P = 5.9×10-6) and invasive ovarian cancer (ORw = 1.26, 95% CI = 1.10 to 1.43, P = 3.8×10-3). These associations were stronger for serous ovarian cancer and for estrogen receptor-negative breast cancer (ORw = 1.46, 95% CI = 1.2 to 1.70, P = 3.4×10-5 and ORw = 1.50, 95% CI = 1.28 to 1.76, P = 4.1×10-5, respectively). For BRCA1 mutation carriers, there was a statistically significant inverse association of the K3326X variant with risk of ovarian cancer (HR = 0.43, 95% CI = 0.22 to 0.84, P = .013) but no association with breast cancer. No association with prostate cancer was observed. Conclusions: Our study provides evidence that the K3326X variant is associated with risk of developing breast and ovarian cancers independent of other pathogenic variants in BRCA2. Further studies are needed to determine the biological mechanism of action responsible for these associations.