Marked activity of irofulven toward human carcinoma cells: comparison with cisplatin and ecteinascidin.

PURPOSE: To characterize the activities of irofulven, a novelanticancer agent derived from the mushroom natural productilludin S toward human cancer cells. EXPERIMENTAL
DESIGN: We have determined the activity spectrum of irofulven toward a human tumor cell panel comprised of 10 different tumor types in comparison with cisplatin and ET-743. We have also evaluated the influence of major resistance mechanisms, such as expression of multidrug resistance-associated drug efflux pumps, cisplatin resistance, loss of p53 function, and absence of mismatch repair on the cytotoxic activity of irofulven.
RESULTS: The activity spectrum of irofulven is clearly different from that of ET-743 and cisplatin. Irofulven shows excellent cytotoxicity toward the majority of human carcinoma cell lines tested, but lesser activity toward sarcoma and leukemia cell lines. The cytotoxic activity of irofulven was particularly pronounced toward head and neck, non-small cell lung, colon, and ovary carcinoma cells, as well as toward malignant glioma cell lines. In addition, irofulven displayed good activity toward poorly differentiated, androgen-independent prostate cancer cells and cell lines expressing high levels of the detoxifying enzymes glutathione S-transferase and gamma-glutamyl cysteine synthetase. The cytotoxicity of irofulven was not affected by loss of p53 or mismatch repair function, and the drug was not a substrate for multidrug transporters, such as the P-glycoprotein and multidrug resistance protein 1.
CONCLUSIONS: Irofulven has an unusual activity spectrum with strong activity toward tumor cells of epithelial origin. Furthermore, irofulven is not or only marginally affected by resistance mechanisms limiting the efficacy of other alkylating agents.