Pironetin, isolated from Streptomyces sp., is a potent inhibitor of microtubule assembly and the first compound identified that covalently binds to
alpha-tubulin at Lys352. We examined whether
pironetin is an effective agent against human
small cell lung cancer H69 cells, including two cell lines resistant to the microtubule-targeted drugs
vindesine (H69/VDS) and
paclitaxel (H69/Txl) that interact with
beta-tubulin.
Pironetin was found to be effective against these resistant cells as well as their parental cells. In addition,
pironetin inhibited the growth of human leukemic K562 multidrug-resistant cells (K562/ADM), which have mdr1 gene expression, as well as the parental K562 cells. In these cell lines, including the parental and resistant cells,
pironetin caused complete mitotic arrest; in addition, apoptosis inductions by 30 and 100 nM
pironetin were observed. In this study, the new mitotic inhibitor,
pironetin, was found to be effective not only against human tumor cell lines resistant to microtubule-targeted drugs, but also multidrug-resistant cells with mdr1 gene expression. These results suggest that
pironetin is a useful agent for overcoming drug resistance in
cancer chemotherapy.