Although membrane trafficking regulators have been linked to cancer there is relatively little known about these proteins contribution to tumorigenesis. As these proteins are essential for cellular transport in signaling we hypothesized that alterations in the expression of trafficking regulators may be important in cancer. Our understanding of cancer mechanisms has been advanced by our ability to analyze the expression of genes on a genome wide scale. We have employed this strategy to identify novel roles for proteins reported or predicted to function in membrane trafficking that are differentially expressed in cancer. Previously, I carried out expression profiling via analysis of microarray data on 650 genes associated with membrane trafficking, referred to as the membrome. This analysis was performed on tumors from the major cancers affecting the population. From this analysis I observed a higher level of membrome proteins, including Rabs, expressed in pancreatic cancer. Since starting my lab at the NCI this year we have collaborated with Laufey Amundadottir at NCI DCEG to further examine the expression of membrome proteins in pancreatic tumors and cells lines using RNA seq. Using both these approaches and data available from the NCI60 and expression data published in the literature we have identified candidate genes for further investigation. We undertook an MTA to bring to the NIC a lentivirus expression system that enables inducible expression of short hairpin RNA (shRNA) in order to deplete the expression of candidate proteins in cells. Using RNA interference candidate proteins are to be monitored for gain or loss of function effects on cell growth, apoptosis, motility, and other tumor related functions in cultured cell lines. shRNA expressing cells will also be used in mouse xenograft studies to examine functions in tumor formation and metastasis.The first protein tested in this study was Rab31, found to be overexpressed in panreatic cancer. Using RNAi we have found that Rab31 is required for cell migration and invasion but not important for proliferation and apoptosis. Xenograph studies (tail vein injection) were initiated in June 2012 and results of the study are expected in August 2012. Additional, biochemical studies of immunoprecipitated Rab31 identified candidate binding proteins associated with cell migration including Cdc42 and Rac1.
