Effects of tnf-related apoptosis inducing ligand (TRAİL) and epoxomicin on apoptosis in different types of osteosarcoma cells

Osteosarcoma (OS) is one of the most frequent primary malignant tumors of bone. Despite recent improvement in therapy, there is inherent or acquired resistance to chemotherapeutic agents in some OS cases. In addition, the other disadvantages of the chemotherapeutic agentsare their cyctotoxic effects to normal tissues and organs. Novel therapeutic approaches are needed for improvement of OS treatment. The purpose of our study was to determine the effects of epoxomicin on TRAIL resistance in MG-63 and Saos-2 osteosarcoma cells with an attempt to find novel anti-cancer agents that target cancer cells or confer synergy with TRAIL. We determined the cytotoxic effect of epoxomicin and TRAIL in Saos-2 and MG-63 OS cell lines using MTT and WST-8 assays. We measured apoptosis markers such as caspase -3, -8, -9 activities and pro-apoptotic Bax levels. We demonstrated apoptosis immunochemically using TUNEL assay. We foundLD50 doses of epoxomicin on MG-63 cells viability as 272 nM, 124 nM and 12 nM after incubations for 24, 48, and 72 h, respectively (P<0.001). We found LD50 doses of epoxomicin on Saos-2 cells viability as approximately 355 nM, 255 nM and 7 nM after incubations for 24, 48, and 72 h, respectively. Incubation with TRAIL and epoxomicin for 24 h significantly increased caspase -3, -8, -9 activities and Bax levels compared to the cells incubated separately with TRAIL or epoxomicin (p<0.01). We determined cell viabilities of MG-63 and Saos-2 upon incubation with different doses of TRAIL and Epoxomicin. This dose study gives us useful information for further apoptosis studies. Our data demonstrated that combining TRAIL with epoxomicin enhanced apoptosis and overcome TRAIL resistance which promises improvement in future OS treatment modalities Key words: Osteosarcoma, TRAIL, Epoxomicin, Apoptosis, MG-63, Saos-2.