CD274 and osteosarcoma: To exclude the possibility that the antitumor effects of PD-L1 knockdown and/or doxorubicin treatment are due to transfection and/or establishment of a stable cell line, we evaluated apoptosis induced by PD-L1 knockdown in 143B parental cells, which express higher levels of both ICSBP and PD-L1 than any other osteosarcoma cell lines (Figure 1A).