MiR-221 inhibits proliferation of pancreatic cancer cells via down regulation of SOCS3.

Abstract

The over-activation of Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway induced by cytokines are closely correlated with tumorigenesis. Suppressor of cytokine signaling 3 (SOCS3) serves as a negative regulator for JAK-STAT, and its down-regulation is involved in the oncogenesis of pancreatic cancer. We aimed at investigating the effect of miR-221 on the expression and proliferation, cycle and apoptosis of pancreatic cancer cells and determine the related mechanism. Dual luciferase reporter gene assay was used to analyze the regulation between miR-221 and SOCS3. The expressions of miR-221, SOCS3, p-JAK and p-STAT3 in normal human pancreatic epithelial cell HPDE6-C7 and pancreatic cancer cell PANC-1 were quantified by qPCR and Western blot. Flow cytometry was used to identify cell cycle and proliferation. In vitro cultured PANC-1 cells were transfected with miR-221 inhibitor or pIRES2-SOCS3. The expressions of miR-221, SOCS3, p-JAK and p-STAT3, along with the cell proliferation or apoptosis, were compared. Bioinformatics analysis showed the existence of binding site between miR-221 and 3'-UTR of SOCS3 mRNA. Dual luciferase gene reporter assay confirmed the targeted regulation between miR-221 and SOCS3. Compared to HPDE6-C7 cells, higher levels of miR-221, p-JAK and p-STAT3 expression, and lower expression of SOCS3, were found in PANC-1 cells, along with the increase of cell proliferation. Transfection of miR-221 inhibitor or pIRES2-SOCS3 remarkably enhanced SOCS3 expression, inhibited the levels of p-JAK and p-STAT3 expression, and impeded the proliferation of PANC-1 cells. MiR-221 decreases proliferation potency of PANC-1 cells and affects JAK-STAT3 signaling pathway via inhibiting SOCS3.