SiRNA-mediated silencing of beta-catenin suppresses invasion and chemosensitivity to doxorubicin in MG-63 osteosarcoma cells. beta-catenin, the chief oncogenic component of the canonical Wnt pathway, is known to be involved in development of a variety of cancers, but its role in human osteosarcomas is not fully understood. Here we investigate the effect of small interfering RNA-mediated beta-catenin knockdown on the survival, invasion and chemosensitivity of a human osteosarcoma cell line.A siRNA against beta-catenin was constructed and transfected into MG-63 cells. Expression of beta-catenin was determined by qRT-PCR and Western blotting. Cell growth and apoptosis were assessed in the presence or absence of doxorubicin by MTT and flow cytometry, respectively, cell invasion by transwell assay, and XIAP, Bclxl, nulear P65 and MT1-MMP expression by western blot and real-time PCR.Transfection of beta-catenin siRNA resulted in decreased expression of beta-catenin, suppression of invasion and motility of MG-63 cells and reduced chemosensitivity to doxorubicin in vitro, but little change in cell growth and apoptosis. At the same time, down-regulation of MT1-MMP and up-regulation of NF-kappaB activation were observed.Knock-down of beta-catenin gene may decrease the invasion ability through down-regulation of MT1-MMP expression and enhance the chemoresistance to doxorubicin via the NF-kappaB pathway. In contrast to other tumors, beta-catenin may not play an oncogenic role in osteosarcoma cells.