A p53 super-tumor suppressor reveals a tumor suppressive p53-Ptpn14-Yap axis in pancreatic cancer

The p53 transcription factor is a critical barrier to pancreatic cancer progression. To unravel mechanisms of p53-mediated tumor suppression, we analyzed pancreatic cancer predisposition in mice expressing p53 transactivation domain (TAD) mutants. Surprisingly, we observed that p53 TAD2 mutant behaves as a “super-tumor suppressor”, with an enhanced capacity to suppress pancreatic cancer and to activate a subset of novel p53 target genes. One such gene, Ptpn14, is a direct p53-inducible gene encoding a negative regulator of the Yap oncoprotein. To determine the effects of p53 deficiency on Yap target gene expression in pre-malignant mouse pancreatic intraepithelial neoplasia (PanIN) lesions, we sorted the CD133-positive ductal epithelial cells that make up the PanINs and used these cells for RNA-sequencing analysis. This analysis revealed that a Yap signature is induced upon p53 deficiency, suggesting that p53 loss promotes the induction of a Yap transcriptional program. Overall design: RNA-seq was performed to determine the differentially expressed genes in wild-type and p53-/- PanIN cells, sorted from KrasG12D;Pdx1-Cre;p53+/+ and KrasG12D;Pdx1-Cre;p53-/- mice.

p53转录因子（transcription factor）是胰腺癌进展过程中的关键屏障。为阐明p53介导的肿瘤抑制机制，我们对表达p53反式激活结构域（transactivation domain, TAD）突变体的小鼠开展了胰腺癌易感性分析。令人意外的是，我们发现p53 TAD2突变体可作为「超级肿瘤抑制因子」，其抑制胰腺癌的能力更强，且能够激活一组新型p53靶基因。其中一个基因为Ptpn14，它是直接受p53诱导的基因，编码Yap癌蛋白的负调控因子。为探究p53缺失对癌前小鼠胰腺上皮内瘤变（pancreatic intraepithelial neoplasia, PanIN）病灶中Yap靶基因表达的影响，我们分选出构成PanIN的CD133阳性导管上皮细胞，并将其用于RNA测序分析。该分析结果显示，p53缺失可诱导Yap特征基因集的表达，提示p53缺失会促进Yap转录程序的激活。实验整体设计：本研究通过RNA测序，分析从KrasG12D;Pdx1-Cre;p53+/+与KrasG12D;Pdx1-Cre;p53-/-小鼠中分选出的野生型与p53-/- PanIN细胞中的差异表达基因。