QTMP, a microtubule-depolymerizing agent, induces autophagy in neuroblastoma cells

Microtubule-targeting agents are highly effective chemotherapeutic agents against cancer, yet their role in modulating complex cellular pathways, such as autophagy, remains poorly understood. In this study, we report that a novel microtubule-depolymerizing antiproliferative agent, 5-(quinolin-2-yl)-4-(3,4,5-trimethoxyphenyl)-1H-imidazol-2-amine (QTMP), induces autophagy in neuroblastoma cells (SH-SY5Y and IMR-32). QTMP demonstrated potent cytotoxicity against SH-SY5Y and IMR-32 neuroblastoma cells, with half-maximal inhibitory values of 21 ± 1 nM and 9.3 ± 1.3 nM, respectively. A brief exposure to QTMP depolymerized microtubules, whereas prolonged exposure resulted in mitotic arrest in SH-SY5Y cells. Furthermore, QTMP caused mitochondrial dysfunction and increased reactive oxygen species production. Microtubule disruption induced oxidative stress and triggered autophagy in QTMP-treated cells, as evidenced by increased microtubule-associated protein 1A/1B light chain 3-II (LC3-II) formation, upregulation of ATG-5, and degradation of p62. Autophagy flux was further confirmed by increased monomeric red fluorescent protein-LC3 puncta in QTMP-treated cells. Importantly, QTMP exhibited a synergistic effect with the autophagy inducer rapamycin and an antagonistic effect with the autophagy inhibitors 3-methyladenine and SAR405, indicating that autophagy contributes to QTMP's cytotoxic mechanism in SH-SY5Y neuroblastoma cells. Similar to QTMP, colchicine and vinblastine also induced autophagy in SH-SY5Y cells, suggesting that autophagy induction is a consequence of microtubule disruption. The findings highlight QTMP as a promising therapeutic candidate that exerts cytotoxic effects by depolymerizing microtubules, inducing mitochondrial dysfunction, increasing reactive oxygen species production, and activating cytotoxic autophagy in neuroblastoma cells. SIGNIFICANCE STATEMENT: This study identifies QTMP (5-(quinolin-2-yl)-4-(3,4,5-trimethoxyphenyl)-1H-imidazol-2-amine), a potent analog of combretastatin A-4, as a promising therapeutic candidate for neuroblastoma. QTMP induces cell death by depolymerizing microtubules, thereby causing severe mitochondrial dysfunction, increased oxidative stress, and subsequent activation of cytotoxic autophagy. These findings provide new insight into the cellular mechanisms of QTMP and highlight the involvement of cytotoxic autophagy in its anticancer activity against neuroblastoma cells.