PTBP1 and osteosarcoma: Next, to investigate the relationship between PTBP1 and drug-resistant osteosarcoma cells, we determined the expression of PTBP1 in human osteoblast line (hFOB), DXR-resistant osteosarcoma cell lines (U2OS/DXR, MG63/DXR, HOS/DXR) and their parental cells by RT-qPCR.