Genetic interactions between INPP4B and RAD50 is prognostic of breast cancer survival

RAD50 is commonly depleted in basal-like breast cancer with concomitant absence of INPP4B and several tumor suppressors such as BRCA1 and TP53. Our previous study revealed that INPP4B and RAD50 interact and such an interaction is associated with breast cancer survival at the transcriptional, translational and genomic levels. In the present study, we explored single nucleotide polymorphisms (SNPs) of these two genes that have synergistic effects on breast cancer survival to decipher mechanisms driving their interactions at the genetic level. The Cox's proportional hazards model was used to test whether SNPs of these two genes are interactively associated with breast cancer survival, following expression quantitative trait loci (eQTL) analysis and functional investigations. Our study revealed two disease-associating blocks, each encompassing five and two non-linkage disequilibrium linked SNPs of INPP4B and RAD50, respectively. Concomitant presence of any rare homozygote from each disease-associating block is synergistically prognostic of poor breast cancer survival. Such synergy is mediated via bypassing pathways controlling cell proliferation and DNA damage repair, which are represented by INPP4B and RAD50. Our study provided genetic evidence of interactions between INPP4B and RAD50, and deepened our understandings on the orchestrated genetic machinery governing tumor progression.