Establishment and Characterization of Single and Triple-Agent Resistant Osteosarcoma Cell Lines.

Two human osteosarcoma cell lines (MG-63 and HOS-143B) are developed into drug-resistant models using a short-term drug exposure and recovery in drug-free media. Cisplatin, doxorubicin, and methotrexate are used as single agents and in triple combination. The highest level of resistance to cisplatin is observed in MG-63/CISR8, doxorubicin in HOS-143B/DOXR8, and methotrexate in HOS-143B/MTXR8. The MG-63/TRIR8 and HOS-143B/TRIR8 triple-resistance models show lower levels of resistance to combination treatment and are not resistant to the drugs individually. Apoptosis assays suggest that the resistance in MG-63/TRIR8 isfrom cisplatin and methotrexate and not doxorubicin. In contrast, the resistance in HOS-143B/TRIR8 is from doxorubicin and methotrexate instead of cisplatin. Upregulation of P-glycoprotein is seen in all resistant models except those developed with single-agent methotrexate. However, P-glycoprotein is not causing resistance in all cell lines as the inhibitor elacridar only reverses the resistance of doxorubicin on MG-63/DOXR8 and HOS-143B/TRIR8. The migration of the MG-63 resistant models is significantly increased, their invasion rate tends to increase, and RT-PCR shows a switch from epithelial to mesenchymal gene signaling. In contrast, a significant decrease in migration is seen in HOS-143B resistant models with their invasion rate tending to decrease and a switch from mesenchymal to epithelial gene signaling.