PO-168 Loss of the MCC gene expression promotes invasiveness of colon cancer cells

ABSTRACT Introduction The ‘Mutated in colorectal cancer’ (MCC) gene was originally discovered due to its linkage with the APC gene. MCC is silenced through gene promoter methylation in colorectal cancer (CRC) but its significance has been poorly understood. MCC promoter methylation occurs early in premalignant tumours and is associated with increased lymph node metastasis in advanced CRC. Here we determined the consequences of MCC knockdown on cell-cell adhesion and invasiveness of colon cancer cells and further characterised the gene methylation in patient tumours. Material and methods MCC promoter methylation was determined in a cohort of 365 CRC and compared with clinicopathological features, with research ethics approval by the Sydney Local Health District. MCC expression was stably knocked down in HCT116 colon cancer cells or induced in HCT15 cells using lentiviral vectors. The impact of MCC knockdown on invasiveness was determined using an organotypic assay and on cell-cell adhesion with dispase and transepithelial electrical resistance (TEER) assays. Protein complexes were characterised using Blue-Native PAGE, co-immunoprecipitation, immunofluorescence and Proximity Ligation Assay (PLA). Results and discussions MCC promoter methylation was found in 58% of cancers in the right colon, 28% in the left colon and 24% in the rectum. Methylation was associated with larger, poorly differentiated, circumferential or mucinous tumours, and higher T stage that indicates increased invasiveness. We established that the MCC protein interacts with the E-cadherin/beta-catenin complex in HCT116 and HCT15 cells. MCC knockdown in HCT116 cells caused a reduction in E-cadherin protein level, disrupted cell-cell adhesive strength and integrity, increased cell invasiveness and hepatocyte growth factor-induced cell scatter. MCC expression in HCT15 cells had the opposite effect in dispase, TEER and PLA assays. The invasive properties induced by MCC knockdown were abrogated by dasatinib, a candidate anti-invasive drug. Thus we have described a novel function of MCC in the regulation of E-cadherin mediated functions. Conclusion Our study advances current understanding of the protein-protein interactions that control cell-cell adhesion and suppress epithelial-mesenchymal-transition. Potential therapies exploiting our findings may include strengthening cellular junctions with dasatinib or other anti-invasive combination therapies.