isocoumarin-nm-3 and Multiple-Myeloma

The isocoumarin NM-3 reverses resistance of human multiple myeloma (MM) cells to dexamethasone and is in clinical trials. In the present work, the NM-3 analog, 185322, has been studied for activity against MM cells.. Human U266, RPMI8226 and primary MM cells were analyzed for the effects of 185322 on cell cycle distribution, tubulin polymerization and induction of apoptosis.. We show that, in contrast to NM-3, treatment with 185322 is associated with a marked arrest of MM cells in M phase. The results also demonstrate that treatment with 185322 is associated with a rapid decrease in tubulin assembly and an increase in Bcl-2 phosphorylation, consistent with disruption of mitosis. Our results further demonstrate that mitotic failure induced by 185322 results in activation of an apoptotic response in MM cell lines and primary MM cells. By contrast, 185322 had little if any effect on growth and survival of human carcinoma cells.. These findings identify a novel inhibitor of microtubule assembly that induces mitotic arrest and apoptosis of MM cells.

Topics: Antimitotic Agents; Apoptosis; Cell Division; Cell Line, Tumor; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Flow Cytometry; Humans; Isocoumarins; Microtubules; Mitosis; Multiple Myeloma

2-(8-Hydroxy-6-methoxy-1-oxo-1Eta-2-benzopyran-3-yl)propionic acid (NM-3) is a small molecule isocoumarin derivative that has recently entered clinical trials as an orally bioavailable anticancer agent. NM-3 induces lethality of human carcinoma cells by both apoptotic and nonapoptotic mechanisms and potentiates the effects of cytotoxic chemotherapeutic agents. The present studies have evaluated the effects of NM-3 on human multiple myeloma (MM) cells. The results demonstrate that NM-3 potentiates dexamethasone-induced killing of both dexamethasone-sensitive MM1.S and dexamethasone-resistant RPMI8226 and U266 MM cells. We show that NM-3 enhances dexamethasone-induced release of the mitochondrial apoptogenic factors cytochrome c and Smac/DIABLO. The results also demonstrate that NM-3 enhances dexamethasone-induced activation of the intrinsic caspase-9->caspase-3 apoptotic pathway. In concert with these results, NM-3 potentiates dexamethasone-induced apoptosis of MM1.S cells. Moreover, NM-3 acts synergistically with dexamethasone in inducing apoptosis of the dexamethasone-resistant RPMI8226 and U266 MM cells. These findings indicate that NM-3 may be effective in combination with dexamethasone in the treatment of MM.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Apoptosis Regulatory Proteins; Carrier Proteins; Caspase 3; Caspase 9; Caspases; Cell Line, Tumor; Coumarins; Cytochromes c; Dexamethasone; Drug Resistance, Neoplasm; Drug Synergism; Enzyme Activation; Humans; Intracellular Signaling Peptides and Proteins; Isocoumarins; Mitochondria; Mitochondrial Proteins; Multiple Myeloma; Reactive Oxygen Species