Project Summary This is a request for a supplement to R01 CA279585 to train Ms. Andrea Valdespino, a highly talented graduate student from the University of Pennsylvania to train with Dr. Maureen Murphy at the Wistar Institute. The overarching goal of the parent R01 is to identify and test a gene expression signature for genetic variants of TP53; this goal followed from our recent publication that identified a 143-gene expression signature that accurately predicts whether heterozygous B cells contain a p53 hypomorph (a lesser functioning genetic variant) versus wild type (WT) p53 or a benign (fully functional) variant. This goal is critical to the 4.5 million people in the United States that are heterozygous for a lesser-functioning “hypomorphic” p53 allele, but who are currently categorized as a “variant of uncertain significance (VUS)”. As a VUS carrier, these individuals are uninformed as to cancer risk and they do not qualify for MRI screening for cancer. Ms. Valdespino has obtained very new data indicating that the interferon signaling pathway (IFN) is significantly upregulated in cells from p53 hypomorphs compared to WT sibling controls. The two aims of the proposed research will: 1) identify the mechanism underlying increased IFN signaling in hypomorph B cells, with focus on the dsRNA/TLR3 pathway and the mitochondrial/dsDNA pathway, and 2) test the other thirty cell lines in the laboratory from hypomorph carriers, compared to WT controls, for activation of IFN signaling. The hope is to determine whether including an activated IFN signaling pathway in our analysis improves the identification of individuals with an impaired p53 pathway. Such an outcome would allow for improved assessment of cancer risk in carriers with genetic variants of p53.