We found that the expression of Bcl-2 was higher in drug-resistant osteosarcoma cells than in drug-sensitive osteosarcoma cells after treated with doxorubicin, whereas the expression of pro-apoptotic proteins was the opposite, leading to defective apoptosis in drug-resistant osteosarcoma cells, inhibiting apoptosis and mediating doxorubicin chemoresistance. The gene discussed is BCL2; the disease is osteosarcoma.