TP53 and osteosarcoma: An investigation designed OBP‐702, a tumor suppressor p53‐expressing oncolytic adenovirus, with the capability of inducing antitumor responses against human osteosarcoma cells. This study revealed that the expression of MDR1 was significantly upregulated in doxorubicin‐resistant osteosarcoma cells and suppressed by OBP‐702, inducing doxorubicin‐ apoptosis.