Use of RNA-Seq and a Transgenic Mouse Model to Identify Genes Which May Contribute to Mutant p53-Driven Prostate Cancer Initiation

SIMPLE SUMMARY: We use RNA-seq analysis to identify genes that may contribute to mutant p53-mediated prostate cancer initiation in a genetically engineered mouse model (B6.129S4-Trp53tm3.1Tyj/J). A total of 1378 differentially expressed genes, including wildtype p53 target genes (e.g. Cdkn1a, Bax, Bcl2, Kras, Mdm2), p53 gain-of-function-related genes (Mgmt, Id4), and prostate cancer-related genes (Cav-1, Raf1, Kras), were identified. Mice that were homozygous or heterozygous for the Trp53 R270H mutation developed grade one PIN lesions at 3 months and 5 months, respectively, whereas wildtype mice did not develop PIN. Immunohistochemical analysis revealed decreased levels of irradiation-mediated apoptosis in homozygous and heterozygous mice when compared to wildtype counterparts, and this aligned with observed differences in apoptosis-related gene expression. ABSTRACT: We previously demonstrated that the Trp53-R270H mutation can drive prostate cancer (CaP) initiation using the FVB.129S4 (Trp53(tm3Tyj/wt)); FVB.129S (Nkx3-1(tm3(cre)Mmswt)) genetically engineered mouse model (GEM). We now validate this finding in a different model (B6.129S4-Trp53(tm3.1Tyj)/J mice) and use RNA-sequencing (RNA-Seq) to identify genes which may contribute to Trp53 R270H-mediated prostate carcinogenesis. Wildtype (Trp53(WT/WT)), heterozygous (Trp53(R270H/WT)), and homozygous mice (Trp53(R270H/R270H)) were exposed to 5 Gy irradiation to activate and stabilize p53, and thereby enhance our ability to identify differences in transcriptional activity between the three groups of mice. Mouse prostates were harvested 6 h post-irradiation and processed for histological/immunohistochemistry (IHC) analysis or were snap-frozen for RNA extraction and transcriptome profiling. IHC analyses determined that presence of the Trp53-R270H mutation impacts apoptosis (lower caspase 3 activity) but not cell proliferation (Ki67). RNA-Seq analysis identified 1378 differentially expressed genes, including wildtype p53 target genes (E.g., Cdkn1a, Bax, Bcl2, Kras, Mdm2), p53 gain-of-function (GOF)-related genes (Mgmt, Id4), and CaP-related genes (Cav-1, Raf1, Kras). Further understanding the mechanisms which contribute to prostate carcinogenesis could allow for the development of improved preventive methods, diagnostics, and treatments for CaP.