Hepatocyte Nuclear Factor 1A (HNF1A) as a possible tumor suppressor in pancreatic cancer

Abstract

Background: HNF1A (Hepatocyte nuclear factor 1 alpha) is a transcription factor that is known to regulate pancreatic differentiation and maintain homeostasis of endocrine pancreas. Recently, genome-wide association studies have implicated HNF1A as a susceptibility gene for pancreatic cancer. However, the functional significance and molecular mechanism of HNF1A in pancreatic carcinogenesis remains unclear. Methods: Using RT-PCR, Western blot and immunohistochemistry methods, we examined HNF1A gene expression in eight pancreatic carcinoma cell lines and in paired tumor and normal tissue samples from patients with resected pancreatic ductal adenocarcinoma. We knocked down the HNF1A gene expression in two cancer cell lines using three siRNA sequences. The impacts on cell proliferation, apoptosis, and cell cycle as well as the phosphorylation of Akt signaling transduction proteins were examined using ATP assay, flow cytometry and Western blot. Results: HNF1A was expressed in three out of eight pancreatic adenocarcinoma cell lines and the level of HNF1A mRNA and protein expression was significantly lower in tumors than in normal adjacent tissues by both RT-PCR and Western Blot analyses. Immunohistochemistry revealed that the level of HNF1A expression was significantly lower in tumor tissues than in non-tumor tissues. Selective blocking of HNF1A by specific siRNA conferred a 2-fold higher rate of cell proliferation, 20% increased S phase and G2 phase cells, and 30-40% reduced apoptosis in pancreatic cancer cell lines. We further demonstrated that HNF1A knockdown activated Akt and its downstream target, the mammalian target of rapamycin (mTOR) in pancreatic cancer cells. Conclusion: These observations provide experimental evidence supporting a possible tumor suppressor role of HNF1A in pancreatic cancer.