Investigating the Interaction of AURKA and UBE2C in Colorectal Cancer Cells

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in the US. Among the many genomic aberrations previously implicated in colorectal cancer, recurrent amplification of chromosome 20q is frequently associated with liver metastasis. Previous research in our lab identified a gene signature on chromosome 20q associated with colorectal cancer progression. In this study, one of the genes in the signature, the ubiquitin conjugating enzyme UBE2C, was identified through preliminary bioinformatics analysis as a candidate for further examination of its role in CRC progression. Co-expression analysis of UBE2C in tumor-normal datasets from the public database Oncomine revealed all the datasets showing its highest co-expression with Aurora kinase A (AURKA) pathway members, i.e. with AURKA and its binding co-factor and activator TPX2, all being localized on chromosome 20q. In addition, preliminary immunoblotting experiments in a panel of ten CRC cell lines showed high positive correlation between endogenous protein expression of UBE2C and AURKA. Overexpression of AURKA led to an increase in UBE2C protein as well as transcript levels, although UBE2C protein levels remained stable when cells were treated with Aurora kinase A inhibitor, suggesting that the mechanism of regulation is independent of the kinase activity. Furthermore, we found evidence of a novel interaction between AURKA and UBE2C protein by co-immunoprecipitation experiments. Finally, we assessed the impact of AURKA expression on the half-life of UBE2C protein using cycloheximide pule-chase assay. In summary, we report a novel relationship between two cell cycle proteins AURKA and UBE2C with potential implications for a new combination therapy in colon cancer