HSP90AA1 and osteosarcoma: Overexpression of HSP90AA1 rendered them resistant to apoptosis induced by cisplatin, doxorubicin and methotrexate, as indicated by an increase in the cell proliferation rate (Fig. 2g), a decrease in the number of Annexin V-PE positive cells (Fig. 2h), and a decrease in the level of cleaved PARP (Fig. 3a and Additional file 1: Figure S1f) compared with pHBLV control treated cells, confirming an antiapoptotic role of HSP90AA1 in osteosarcoma cells.