Irofulven (6-hydroxymethylacylfulvene, MGI 114) induces caspase 8 and 9-mediated apoptosis in human pancreatic adenocarcinoma cells

Background: Irofulven (MGI 114) is a novel, clinically active sesquiterpene whose mechanism of action is not fully understood. We sought to identify a poptotic effectors induced by this agent in human pancreatic cancer cells. Materials and Methods: MTT assay was used to assess IC50. Apoptosis was qua ntitated by flow cytometry and DAPI staining. Caspase activation was identi fied by western blot analysis. Results: Irofulven was cytotoxic against all pancreatic cancer cell lines tested (IC(50)1-18 muM), and induced 10-fold (4% +/- 2, vs. 41% +/- 5) induction of apoptosis. Irofulven-treated cells a lso demonstrated PARP(3) cleavage and DAPI staining. Apoptosis was reduced to baseline levels by Z-VAD-FMK, a broad-spectrum caspase inhibitor. Wester n blot analysis revealed that caspases-3, -7, -8, and -9 were activated by irofulven. Time course evaluation demonstrated that caspases-8 and -9 were the initial species activated. Conclusion: Our data demonstrate that the cy totoxicity of irofulven in human pancreatic carcinoma cell lines is mediate d by caspase-induced apoptosis.