Acquisition of multidrug resistance in osteosarcomas, analyzed by doxorubicin binding assay, and histologic response to chemotherapy.

BACKGROUND

The mechanism by which multidrug resistance is acquired in human osteosarcomas remains unclear. In this study, we analyzed the changes in doxorubicin (DOX) binding ability (%DB), showing chemosensitivity before and after chemotherapy with DOX and cisplatin (CDDP), and evaluated the histologic response of human osteosarcomas to chemotherapy.

MATERIALS AND METHODS

Eight osteosarcomas were analyzed. %DB by the DOX binding assay was measured in fresh tumor tissues at biopsy and at resection after preoperative chemotherapy. The histologic response to chemotherapy was also evaluated.

RESULTS

Changes in %DB before and after chemotherapy were classified into 4 patterns; A: high (> 80%) to low (< 80%), B: high to high, C: low to low, D: low to high. The two tumors, classified as type A and B were responders (> 90% necrosis), whereas the 6 tumors of type C and D were classified as non-responders (< 90% necrosis). Based on these data, we speculated that the fraction of cell populations with different chemosensitivities to DOX and CDDP varied and found that type B tumors have no population of resistant cells, whereas type C tumors have a large fraction of resistant cells.

CONCLUSION

We concluded that osteosarcomas are composed of mixed cell populations with different chemosensitivities to anticancer agents and also that survival of multidrug resistant cell populations may be the most important mechanism in acquisition of multidrug resistance of osteosarcomas after chemotherapy.