Germline Variants in the Immune Response-Related Genes: Possible Modifying Effect on Age-Dependent BRCA1 Penetrance...

BRCA1/2 mutations are the most recognized causes of hereditary breast cancer (BC), but their penetrance is incomplete. BRCA1-driven tumors are often chromosomally unstable and exhibit increased antigenicity. We hypothesized that inherited variations in immune-related pathways may influence BRCA1 penetrance.

Case-control comparison of BC-affected versus non-affected BRCA1-mutated women is generally complicated because the latter groups are often low in numbers, represented by younger subjects and may contain relatives of the analyzed patients. We utilized a novel approach, i.e., we compared young-onset and late-onset BRCA1-associated BC cases, assuming that the early age at disease manifestation may be an indicator of increased BRCA1 penetrance.

NGS for 353 genes implicated in inborn errors of immunity was performed on 42 young-onset (<39 y.o.) and 35 late-onset (>57 y.o.) BC patients carrying BRCA1 pathogenic variants. This effort identified 22 potentially relevant variants, which were further analyzed in an extended cohort (up to 90 patients per group). The PRF1 p.Ala91Val variant, associated with familial hemophagocytic lymphohistiocytosis, was found in 9.6% of young-onset patients and none of the late-onset group (7/73 vs. 0/78, p = 0.005). The significance of this allele was further validated in an additional group of Russian patients (14/164 (8.5%) vs. 8/236 (3.4%), p = 0.042). This trend also retained upon the pooled analysis of Russian and Polish subjects (24/278 (8.6%) vs. 15/337 (4.4%), p = 0.045).

Rare variants in immune-related genes, such as PRF1 p.Ala91Val, may influence BRCA1 penetrance. Broader exome-wide analyses comparing affected vs. unaffected BRCA1/2 mutation carriers, or women stratified by age at cancer onset, could help identify additional genetic modifiers of cancer risk.