Effects of the loss of the KCASH2 oncosuppressor on colon inflammation and tumorigenesis

KCASH2 is a member of the KCASH family of proteins and acts as a negative regulator of the Hedgehog (Hh) pathway, which is crucial during embryonic development and, when deregulated, contributes to the tumorigenesis of various organs (Carballo, Honorato et al. 2018). Growing evidence show that Hh signaling plays a key role in intestinal development, in pathogenesis of inflammatory bowel diseases (IBD) and colorectal cancer (CRC), but also in modulating immune and inflammatory responses within the intestinal microenvironment (Xie, Zhang et al. 2021). Given the relevance of KCASH2 as a negative regulator of the Hh pathway, we investigated how its loss affects the development, progression, and immune response in colon inflammation and inflammation-driven CRC, using the well-established AOM/DSS-induced model of colitis-associated cancer in the KCASH2-KO mouse model, previously generated in our laboratory. In physiological conditions, the absence of KCASH2 leads to increased Hh pathway activity in the colon and in lymphoid organs, including spleen, mesenteric and inguinal lymph nodes, suggesting a functional role for KCASH2 in these tissues. Following AOM/DSS treatment, KCASH2-KO mice showed heightened sensitivity, characterized by greater weight loss, increased mortality, and more severe mucosal damage. Coherently, this increased sensitivity during the acute phase of inflammation correlated with a reduction in immune cell populations involved in tissue repair. Indeed, flow cytometric analyses of spleen and colon revealed that the absence of KCASH2 was associated with a reduction in type 2 immune cells (Th2, ILC2, DC2), regulatory T cells (Tregs), Th17, natural killer (NK) cells, and myeloid populations such as eosinophils and neutrophils. Lastly, we analyzed the effects of the loss of KCASH2 on the development and progression of CRC after 12 weeks of AOM/DSS treatment. Macroscopic analysis of the colon revealed that KCASH2 KO mice developed greater number of tumor lesions, with increased tumor size and total tumor area compared to control mice. A deeper understanding of how KCASH2 modulates the Hh pathway in colonic inflammation, inflammation-associated CRC, and immune regulation may offer important findings for the development of novel therapeutic strategies for the treatment of inflammatory disorders and intestinal malignancies characterized by aberrant Hh pathway activation.