Abstract 4430: Implication of the primary cilium in the Hedgehog pathway in colorectal cancer cells

Abstract

Abstract Background: The Hedgehog (HH) pathway is involved in the maintenance of numerous cell types both during development and in the adult. Often deregulated in cancers, its involvement in colorectal cancer has come into view during the last few years, although its role remains poorly defined. In most tissues, the HH pathway is highly connected to the primary cilium (PC), an organelle not expressed in the normal colonic epithelium which recruits the functional components and regulates the pathway. Aims: Since the intestinal epithelium is known to be a non-ciliated tissue, the HH pathway as related to the PC has not been explored. We investigated the presence of PC in colon cancer tumors and cell lines. Our hypothesis is that PC formation controls the HH activation that has been reported in numerous colon cancer studies. Materials and methods: We used cellular models to look at HH activation, focusing on the final effector Gli1. The link between PC and the HH pathway was shown by the recruitment of the Smo receptor in the PC. We looked for PC in a subset of 63 tumors from a Tissue Micro Array and in 4 colorectal cell lines by immunofluorescence using two well-known markers, acetylated α-tubulin and polyglutamylated tubulin. 3D deconvoluted pictures were obtained to characterize the shape and size of PC. Using cellular models we investigated HH pathway expression by qPCR. We assessed the functional link between HH pathway and PC through localization of the Smo receptor in the PC using immunofluorescence. Results: We observed the presence of the PC in the epithelium of primary colorectal tumors at all stages but not in their normal counterparts. Using human colorectal cancer cell lines we found a clear correlation between the presence of the PC and the expression of the final HH effector, GLI1, and provide evidence of a functional link between the two by demonstrating the recruitment of the SMO receptor to the PC membrane. Conclusion: We conclude that the PC directly participates in the HH pathway in colorectal cancer cells which is the first observation of PC expression in tumors arising from a non-ciliated tissue. Functional studies are required to determine the mode of action of this organelle in carcinogenesis. Citation Format: Blanche Senicourt. Implication of the primary cilium in the Hedgehog pathway in colorectal cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4430.