In vitro evaluation of new anticancer drugs, exemplified by vinorelbine, using the fluorometric microculture cytotoxicity assay on human tumor cell lines and patient biopsy cells

The feasibility of combined studies on a cell-line panel and primary cultures of patient tumor cells in the preclinical evaluation of new anticancer drugs was evaluated in a study of the activity and cross-resistance pattern in vitro of the new semi-synthetic vinca alkaloid vinorelbine (Vrb). The activity of Vrb was investigated in ten cell lines representing different resistance mechanisms and in a total of 256 fresh human tumor samples, using the fluorometric microculture cytotoxicity assay (FMCA). Resistance to Vrb in the cell lines was associated with expression of the multidrug resistance-mediating P-glycoprotein and the multidrug resistance-associated protein (MRP) and by a recently described tubulin-associated mechanism, while the cell lines with topoisomerase II- and glutathion-associated resistance did not show decreased sensitivity to the drug. Cross-resistance to vincristine (Vcr) and other tubulin-active agents was high in cell lines as well as in patient cells. As with most commonly used anti-cancer drugs, Vrb was more active in hematological than in solid tumor samples. Among the solid tumors investigated, the highest in vitro response rates were observed in ovarian cancer (27%), sarcoma (25%), non-small cell lung cancer (21%) and bladder cancer (20%), while no response was observed in renal or colorectal cancer. Compared to Vcr, Vrb appeared to be slightly more active in solid tumors and slightly less active in hematological tumors. The results show that although Vrb displays a high degree of cross-resistance to Vcr and other tubulin-active drugs, some difference in the activity spectrum could be detected and that the drug is sensitive to multiple mechanisms of resistance. The results also suggest that leukemias, ovarian cancer, sarcoma and bladder cancer are possible further targets for Vrb. The combination of studies on a cell-line panel and patient tumor cells from a broad spectrum of diagnoses to evaluate a new drug seems feasible and may give information on the mechanism of action and target diagnoses for phase II trials.