Identification of cancer modifiers using parental strain expression mapping

Inherited genetic risk factors play an important role in cancer. However, other than cancer susceptibility genes found in familial cancer syndromes and inherited in a Mendelian fashion, little is known about modifier genes (germline variants that interact with each other and with environmental factors) that contribute to individual susceptibility. Here we develop a strategy “parental strain expression mapping” (PSEM), which utilizes the homogeneity of inbred mice and genome-wide mRNA expression analyses, to directly identify candidate germline modifier genes and pathways underlying phenotypic differences among murine strains exposed to transgenic activation of AKT1. We identified multiple candidate modifier pathways and specifically, the glycolysis pathway as a candidate negative modulator of AKT1-induced proliferation. In keeping with findings in murine models, the expression of the glycolysis pathway was strongly enriched in the non-cancer prostate tissue from patients with prostate cancer who did not recur after surgical resection. Together these data suggest that PSEM can directly identify germline modifier pathways of relevance to human disease. Keywords: genetic modifier mRNA expression profiling was carried out with 24 samples of VP from 6 inbred strains.