Pancreatic cancer is a leading cause of cancer deaths in both men and women, and approximately 90% of all pancreatic malignancies are pancreatic ductal adenocarcinoma (PDAC). Therapeutic efficacy and long-term prognosis of treatment are strongly depended on time of diagnosis and stage of tumor, but overall patient prognosis remains dismal. Thus, it is imperative to further study the underlying biology of PDAC. Previous large-scale expression profiling analyses performed by the group identified, among others, Cytochrome C
Oxidase Assembly Factor 4 Homolog (COA4) and RNA Polymerase III Subunit K (POLr3K) as significantly overexpressed among PDAC tissues. My work aimed to detect the molecular function of these two candidate genes in PDAC. RNAi-mediated knockdown approaches against the candidate genes revealed that cell growth inhibition caused by COA4 and POLr3K was due to inhibition of proliferation rather than induction of cell apoptosis. Moreover, knockdown of target genes interfered with anchorage independent growth (both targets) as well as cell migration (only COA4). Expression of the cell cycle related proteins p21 and Cyclin D1 were significantly changed upon siRNA transfection in both cases. Cell cycle analyses by flow cytometry suggested that inhibition of COA4, but not POLr3K, could attenuate cell cycle progression. To further investigate functional effectors of COA4 and POLr3K, RNA-Seq and TaqMan human microRNA array analyses were performed respectively. Gene enrichment analysis and subsequent functional analyses demonstrated that Plasminogen Activator (PLAU) was differentially expressed gene upon COA4 inhibition and was a central mediator of the inhibitory effects of COA4 silencing on cell migratory potential. miR-30d-5p (miR30d) was identified as significantly
repressed upon POLr3K inhibition, and rescue experiments using microRNA mimics indicated that miR30d served to regulate cell growth downstream of POLr3K. Tissue microarray (TMA) based immunohistochemistry analyses did not indicate a direct and strong association of COA4 or POLr3K expression with patient survival. Nonetheless, COA4 and POLr3K appeared to be potential novel therapeutic targets in PDAC and may turn out to be clinically useful prognostic markers as well as.