EXPRESSION OF THE MULTIDRUG-RESISTANCE GENE IN OSTEOSARCOMA - A PILOT-STUDY

Resistance to combination chemotherapy remains a challenge in the trea tment of osteosarcoma yet has not been studied extensively in this tum our. 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 d rug resistance in a number of tumour cell lines in vitro, which sugges ts that it also may be useful as a predictor of similar resistance in vivo. Using a highly sensitive assay based on the polymerase chain rea ction to measure the amount of mdr1 mRNA, we detected various levels o f mdr1 expression in 18 osteosarcoma specimens from 15 patients with r esectable 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 investigatio n of the effect of mdr1 gene expression on outcome in osteosarcoma is warranted.