Antitumor Activity Of Curcumin Is Involved In Down-regulation Of YAP Expression In Pancreatic Cancer Cells

Pancreatic cancer(PC)is one of the most aggressive human malignancies worldwide and is the fourth leading cause of cancer-related deaths.Curcumin(diferuloylmethane)is a polyphenol derived from the Curcuma longa plant.Certain studies have demonstrated that curcumin exerts its anti-tumor function in a variety of human cancers including PC,via targeting multiple therapeutically important cancer signaling pathways.However,the detailed molecular mechanisms are not fully understood.Two transcriptional co-activators,YAP(Yes-associated protein)and its close paralog TAZ(transcriptional coactivator with PDZ-binding motif)exert oncogenic activities in various cancers.Therefore,in this study we aimed to determine the molecular basis of curcumin-induced cell proliferation inhibition in PC cells.Methods1.The cell proliferation was detected by CTG assay and colony formation assay after curcumin treatment in pancreatic cancer cells.2.The cell apoptosis and cell cycle arrest were analyzed by flow cytometry and inverted fluorescence microscope in pancreatic cancer cells with the treatment of curcumin.3.The ability of migration and invasion was measured by wound-healing assay and Transwell assay in pancreatic cancer cells with the treatment of curcumin.4.The expression of YAP/TAZ and its downstream protein Notch1 was analyzed by Western blotting assay in pancreatic cancer cells after curcumin treatment.5.The molecular mechanism of curcumin inhibiting the progression and development of pancreatic cancer cells was researched by transfection of YAP plasmid or small interfering RNA(siRNA),which regulate the expression of YAP/TAZ in pancreatic cancer cells.Results1.Curcumin inhibited PC cells growth.2.Curcumin induced PC cells apoptosis and caused cell cycle arrest.3.Curcumin inhibited cell migration and invasion in PC cells and inhibited YAP/TAZ expression.4.Overexpression of YAP triggered cell proliferation,abrogated cell apoptosis and promoted cell invasion in PC cells.5.Overexpression of YAP enhanced PC cells migration and improved the protein expression of Notch1.6.Overexpression of YAP abrogated curcumin-mediated anti-tumor activity in PC cells.7.Knockdown of YAP inhibited cell proliferation,promoted cell apoptosis and inhibited cell invasion in PC cells.8.Knockdown of YAP inhibited PC cells migration and reduced the protein expression of Notch1.9.Knockdown of YAP enhanced curcumin-induced anti-tumor function in PC cells.ConclusionsWe found that curcumin significantly suppressed cell growth,weakened clonogenic potential,inhibited migration and invasion,and induced apoptosis and cell cycle arrest in PC cells.We further observed that overexpression of YAP enhanced cell proliferation and abrogated the cytotoxic effects of curcumin on PC cells.Moreover,we found that curcumin markedly down-regulated YAP and TAZ expression and subsequently suppressed Notch-1 expression.Collectively,these findings suggest that pharmacological inhibition of YAP and TAZ activity by curcumin may be a promising anticancer strategy for the treatment of PC patients.