Innate Immunity Variants Associated With Earlier Breast Cancer in BRCA1 Carriers

This variability complicates decisions on when to undertake risk‑reducing surgery to remove the breasts, fallopian tubes, and ovaries. Understanding modifiers that shift disease onset could refine individualized risk prediction for surveillance and preventive care. New findings now demonstrate that damaging variants in innate immunity genes correlate with earlier breast cancer among BRCA1 carriers.

In work disseminated by the British Medical Journal (BMJ) and published in the Journal of Medical Genetics, investigators examined whole exome sequencing (WES) data from 321 Ashkenazi Jewish women with the BRCA1 185delAG mutation. Among Ashkenazi Jews, the prevalence of BRCA1 mutations is reported to be five to six times higher than in other ethnic groups worldwide. WES interrogates the protein‑coding exome—about 1–2% of DNA—where approximately 85% of known disease‑causing variants reside.

Of the 321 carriers, 98 had been diagnosed with breast cancer, with a mean age at diagnosis of 41.5 years and a range of 26 to 75 years. The analysis evaluated whether additional likely damaging missense variants in genes governing innate immune responses were associated with age at onset. The cohort design focused on a single founder mutation (185delAG) to assess modifying genetic factors.

Damaging variants in innate immunity genes were significantly associated with earlier disease onset. Associations were strongest for genes involved in natural killer (NK) cell activation, which function in rapid antitumor and antiviral defense. Carriers harboring such NK cell–related variants had a risk of earlier onset more than 3.5 times greater.

The authors characterized these results as preliminary and emphasized the need for replication in independent, ethnically diverse, larger cohorts that include carriers of heterogeneous BRCA1 pathogenic variants. They stated that the findings highlight a potential role for innate immune pathways as modifiers of BRCA1 penetrance and may support the development of more refined, personalized risk prediction models for BRCA1 carriers. The study, “Damaging missense variants in innate immunity genes are associated with earlier age of breast cancer onset in BRCA1 185delAG carriers,” appears in the Journal of Medical Genetics (2026).