256P Recombination signal binding protein for immunoglobulin- kappa-J region (RBPJ) and Mastermind-like 3 (MAML3) are potential therapeutic targets for pancreatic cancer

Abstract

Background We have reported that Hypoxia induces Smo transcription, which is driver gene of Hh signaling, and that hypoxia enhances invasion and proliferation of pancreas cancer cells through increased Smo transcription. We have also reported protein-bound polysaccharide-K (PSK) can reduce Smo transcription under hypoxia. However, the precise mechanism of hypoxia-induced activation of Smo transcription remains unclear. Our goal is to find pivotal factors which regulates hypoxia-induced activation of SMO transcription and to detect a new effective therapeutic target for pancreatic cancer. Methods Three pancreatic cancer cell lines (ASPC1, SUIT2 and PANC1) were cultured under normoxic and hypoxic (1% O2) conditions. DNA microarray analysis was performed using cells cultured under normoxia and hypoxia. RNA interference and plasmid were used to knock down and overexpress each genes. mRNA expression was estimated by Real time RT-PCR, and Protein expression was by Western blotting. Proliferation assay, Matrigel invasion assay were performed to investigate cell functions. We used PSK to block Smo transcription. Results 1) A transcriptional regulator, recombination signal binding protein for immunoglobulin-kappa-J region (RBPJ) and a transcriptional co-activator, Mastermind-like 3 (MAML3) were picked up for candidate genes. 2) Expressions of SMO, RBPJ and MAML3 were increased under hypoxia in pancreatic cancer cell lines. PSK reduced these expressions under hypoxia. 3) RBPJ and MAML3 inhibition under hypoxia led to decreased SMO and GLI1 expressions. 4) Overexpression of RBPJ under hypoxia led to increased SMO expression and PSK reduced this increased expression. 5) Overexpression of RBPJ under hypoxia showed increased invasiveness and proliferation. PSK reduced these invasiveness and proliferation. Conclusions These results suggest that hypoxia promotes SMO transcription through upregulation of MAML3 and RBPJ to induce proliferation, invasiveness in pancreatic cancer, and that MAML3 and RBPJ can be a new therapeutic target for pancreatic cancer. In addition to that, PSK can be a promising drug for pancreatic cancer by down regulating these new targets. Legal entity responsible for the study N/A Funding JSPS KAKENHI grant number 26293289 Disclosure All authors have declared no conflicts of interest.