TP53 and osteosarcoma: reported that in the hypoxic microenvironment of osteosarcoma, the level of phosphorylated p53 (an active form of p53) decreased when compared to normoxic conditions which results in the reduction of the chemotherapy-induced apoptosis, and this action is HIF-1A-independent as it is neither stimulated nor reversed by expression or inhibition of HIF-1A [41].