Research Of MicroRNA-141/MAP4K4Pathway In Pancreatic Cancer

Background and objectivePancreatic cancer remains a hard nut to crack in all human cancers, with traditionaldiagnosis and treatments having little effect on the disease course. It is now quite urgent toclarify the mechanism of pancreatic cancer’s occurrence and seek for novel diagnosticmethods and effective therapeutic ways for pancreatic cancer.MicroRNAs (miRNAs) have been reported associating with various cancer types via theirability to affect expression of genes that modulate tumorigenesis, including pancreaticcancer. MiR-141is a member of the miR-200family that mainly takes effect onepithelial-mesenchymal transition (EMT) process. Recent data have shown that miR-141plays an important fact in tumorigenesis. However, the exact role of miR-141in pancreaticcancer has not been elucidated yet. In this study, we explored the role of miR-141andinvestigated the mechanism of miR-141/MAP4K4pathway in pancreatic cancer.Methods40cases of pancreatic adenocarcinoma tissue samples and their paired adjacentnormal tissues were selected from2009to2012in our hospital. Real-time PCR wasperformed to detect the expression of miR-141and MAP4K4. The correlation betweenmiR-141and MAP4K4was statistically analyzed. Dual-luciferase reporter gene assay wasused to investigate the effect of miR-141on the activity of MAP4K4in pancreatic cancercell lines.MiR-141mimic, MAP4K4siRNA and other chemical synthetic segments weretransfected into PANC-1and MiaPaCa-2cell lines using LipofectamineTM2000. Real-timePCR and western blot were used to demonstrate the effect of transfection. Western blot wasalso used to detect the expression of MAP4K4, MMPs, Bax, Bcl-2, cyclinD1in cell lines. Cell proliferation was performed using MTT assay. The cell cycle and apoptosis weremeasured by flow cytometry. Cell invasive ability was evaluated by Transwell research.ResultsMiR-141was significantly lower in pancreatic cancer tissues than in normalpancreatic tissues (P<0.01). Additionally, compared to the normal pancreatic samples, themiR-141expression in five human pancreatic cancer cell lines (AsPC-1, BxPC-3, PANC-1,MiaPaCa-2and SW1990) were all significantly decreased (P<0.01). However, theexpression of MAP4K4was obviously higher in pancreatic cancer tissues than in adjacentnormal tissues. Pearson’s correlation showed the expression of miR-141was inverselyrelated to MAP4K4in the tissue samples (P<0.05).Overexpression of miR-141resulted in inhibition of cell proliferation, colonyformation and invasion, leads to increasing of G1phase arrest and apoptosis, which wassimilar to knockdown of MAP4K4.Dual-luciferase report gene assay showed that the relative luciferase activity of theplasmid carrying MAP4K43’UTR of wild type was significantly suppressed in thepresence of miR-141mimic (P<0.01), whereas this obvious effect was not able to detectedin the structure that carrying the mutant MAP4K43’UTR (P>0.05).ConclusionsMiR-141is downregulated in pancreatic cancer, while MAP4K4is overexpressed.Negative correlation exists between these two genes. MiR-141has a potential to inhibitpancreatic cancer cell growth through directly targeting MAP4K4. Therefore, our presentstudy implicated that miR-141acts as an inhibitor in pancreatic cancer and may serve as anovel therapeutic agent in pancreatic cancer treatment.