GSK3B and osteosarcoma: In order to confirm that these anti-osteosarcoma results are specifically achieved by PPI-induced inactivation of Wnt/β-catenin, and not due to nonspecific effects of PPI treatment, we pretreated 143-B cells with the specific GSK-3β inhibitor, CHIR99021, before challenging 143-B cells with 0.8 μM PPI.