Abstract
Simple SummaryWe 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.We previously demonstrated that the Trp53-R270H mutation can drive prostate cancer (CaP) initiation using the FVB.129S4 (Trp53tm3Tyj/wt); FVB.129S (Nkx3-1tm3(cre)Mmswt) genetically engineered mouse model (GEM). We now validate this finding in a different model (B6.129S4-Trp53tm3.1Tyj/J mice) and use RNA-sequencing (RNA-Seq) to identify genes which may contribute to Trp53 R270H-mediated prostate carcinogenesis. Wildtype (Trp53WT/WT), heterozygous (Trp53R270H/WT), and homozygous mice (Trp53R270H/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.
Highlights
Mechanisms which contribute to CaP initiation is important because it can inform the development of chemoprevention strategies, which could reduce this number as well as support the development of improved diagnostic and prognostic biomarkers
Prostatic intraepithelial neoplasia (PIN) lesions were observed in B6.129S4-Trp53tm3.1Tyj /J
At 3 months of age, areas of metaplasia and atypical hyperplasia were observed in heterozygous mice, and grade one prostatic intraepithelial neoplasia (PIN) lesions were observed in homozygous mice
Summary
Loss of PTEN and amplification of Myc can both drive CaP initiation in mouse models [3]; these genetic alterations occur in up to 60 and 50% of CaP patients, respectively [4,5]. Our group has previously demonstrated that the Trp53-R270H mutation can drive CaP initiation in FVB.129S4 (Trp53tm3Tyj/wt ); FVB.129S (Nkx3-1tm3(cre)Mmswt ) mice (Vinall et al, 2012). In this model, Trp53R270H/R270H mice developed prostatic intraepithelial neoplasia (PIN) as early as 6 weeks, and Trp53R270H/+ mice developed PIN as early as 3 months [9].
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