PO-192 The emt factor zeb1 promotes adenoma formation through the inhibition of cell senescence and apoptosis

Introduction More than 70% of sporadic colorectal carcinomas (CRC) harbour loss-of-function mutations in the APC gene, which cause aberrant activation of Wnt signalling and ultimately lead to the onset of colon adenomas. The Apc min/+ mouse model is an appropriate tool for the study of the formation of early adenomas, which progress into carcinomas when mice are crossed with other oncogenic models, establishing a direct link between Wnt signalling and colorectal cancer. The EMT-TF ZEB1 is induced by Wnt pathway and, at the same time, acts as a mediator of the pathway in the regulation of key Wnt target genes. However, the role of ZEB1 during the formation of early intestinal adenomas remains unknown. Material and methods The study has made use of a wide range of in vitro , in vivo and high throughput approaches, including a mouse model of intestinal adenomas, a mouse deficient for ZEB1 and RNA sequencing. Results and discussions To explore the role of ZEB1 in adenoma formation, we downregulated its expression in the Apc min/+ mouse by crossing it with Zeb1 +/- mice (Apc min/+ /Zeb1 +/- ) and compared the formation of adenomas with respect Apc min/+ /Zeb1 +/+ . Compared to Apc min/+ /Zeb1 +/+ counterparts, Apc min/+ /Zeb1 +/- mice presented half the number of tumours and a more differentiated histological pattern. Likewise, tumours in Apc min/+ /Zeb1 +/- showed no significant difference in proliferation—as assessed by PCNA staining—but increased number of senescent and apoptotic cells—determined by β-galactosidase and TUNEL assays—than the tumours developed in Apc min/+ /Zeb1 +/+ mice. In order to ascertain the mechanisms by which ZEB1 regulates adenoma formation, the gene signature of Apc min/+ /Zeb1 +/+ and Apc min/+ /Zeb1 +/- adenomas was determined by RNA sequencing. Interestingly, in line with the results from the TUNEL assay, bioinformatics analysis of RNAseq revealed that several apoptosis-related genes were differentially expressed, with Bbc3 and Cd82 being validated in an independent series of intestinal adenoma samples. Lastly, Apc min/+ /Zeb1 +/- mice exhibited enhanced survival with respect to Apc min/+ /Zeb1 +/+ . Conclusion Altogether, our data indicate that ZEB1 promotes adenoma formation by inhibition of apoptosis and senescence in adenoma cells. In turn, a partial downregulation of Zeb1 is sufficient to inhibit adenoma formation and improve survival in the Apc min/+ mouse model.