SELENOP modifies sporadic colorectal carcinogenesis and WNT signaling activity through LRP5/6 interactions

Abstract

Although selenium deficiency correlates with colorectal cancer (CRC) risk, the roles of the selenium-rich antioxidant selenoprotein P (SELENOP) in CRC remain unclear. In this study, we defined SELENOP’s contributions to sporadic colorectal carcinogenesis. In human scRNA-seq datasets, we discovered that SELENOP expression rises as normal colon stem cells transform into adenomas that progress into carcinomas. We next examined the effects of Selenop knockout in a mouse adenoma model that involves conditional, intestinal epithelial-specific deletion of the tumor suppressor adenomatous polyposis coli (Apc) and found that Selenop knockout decreased colon tumor incidence and size. We mechanistically interrogated SELENOP-driven phenotypes in tumor organoids as well as CRC and noncancer cell lines. Selenop knockout tumor organoids demonstrated defects in organoid formation and decreases in WNT target gene expression, which could be reversed by SELENOP restoration. Moreover, SELENOP increased canonical WNT signaling activity in noncancer and CRC cell lines. In defining SELENOP’s mechanism of action, we mapped protein-protein interactions between SELENOP and the WNT co-receptor low-density lipoprotein receptor-related protein 5/6 (LRP5/6). Lastly, we confirmed that SELENOP:LRP5/6 interactions contributed to SELENOP’s effects on WNT activity. Overall, our results position SELENOP as a modulator of the WNT signaling pathway in sporadic CRC.