Ornithine decarboxylase--a predictor for tumor chemosensitivity.

The activity of ornithine decarboxylase (ODC) was determined in P388 murine leukemia cells treated with adriamycin (ADR) and methotrexate (MTX). Some of the cell lines were resistant to ADR, MTX or their combinations. A similar pattern was found between the cytotoxicity and the suppression of ODC activity in these cell lines in terms of drug concentrations. In a cell line resistant to one drug, a relatively high concentration of that drug was required to inhibit ODC activity. This effect was independent of the sensitivity of the cells to the other drug. A similar correlation between arrest of growth and the inhibition in the induction of ODC was also observed in human epithelial carcinoma cells. In this case too, the growth of multidrug resistant cells was not affected by vinblastine, neither was the induction of ODC. On the other hand, both the growth and the induction of ODC were inhibited by vinblastine in drug-sensitive cells. These findings suggest that ODC measurements might be used for predicting the chemosensitivity of tumor cells.