Expression of the multidrug resistance gene in osteosarcoma: a pilot study.

Resistance to combination chemotherapy remains a challenge in the treatment of osteosarcoma yet has not been studied extensively in this tumour. One mechanism of multiple drug resistance is increased expression of the multidrug resistance gene (mdr1). The level of mdr1 messenger RNA (mRNA) expression has been found to correlate with the degree of drug resistance in a number of tumour cell lines in vitro, which suggests that it also may be useful as a predictor of similar resistance in vivo. Using a highly sensitive assay based on the polymerase chain reaction to measure the amount of mdr1 mRNA, we detected various levels of mdr1 expression in 18 osteosarcoma specimens from 15 patients with resectable nonmetastatic osteosarcoma. At follow-up at a minimum of 30 months later, a trend toward a worse outcome was observed in patients with tumours exhibiting high levels of mdr1 expression. The results of this pilot study suggest that a larger scale prospective investigation of the effect of mdr1 gene expression on outcome in osteosarcoma is warranted.