Serotonin type-3 receptor antagonists selectively kill melanoma cells through classical apoptosis, microtubule depolymerisation, ERK activation, and NF-κB downregulation.

Malignant melanoma is a highly metastatic tumour, resistant to treatment. Serotonin type-3 (5-HT3) receptor antagonists, such as tropisetron and ondansetron, are well-tolerated antiemetic drugs commonly used to prevent nausea caused by chemotherapy or radiotherapy. We investigated the anticancer effects of these drugs on melanoma cancer cell lines WM-266-4 and B16F10 with or without paclitaxel. We constructed IC50 curves and performed Chou-Talalay analysis, using data obtained with the MTT assay. Flow cytometry and fluorescent microscopy were used to examine characteristics of the cell cycle, cell death and cytoskeleton changes. Protein levels and activation were analysed by western blotting and molecular docking studies carried out. Data were analysed by one way ANOVA and post hoc testing. Ondansetron and tropisetron showed selective concentration-dependent cytotoxicity in melanoma cell lines WM-266-4 and B16F10. The effect in combination with paclitaxel was synergistic. The drugs did not cause cell cycle arrest but did promote characteristics of classical apoptosis, including accumulation of subG1 DNA, cleaved caspase-3, mitochondrial membrane permeability and phosphatidylserine exposure. As well, the cytosolic calcium level in the melanoma cells was enhanced, phosphorylated ERK1/2 induced and NF-κB inhibited. Finally, the formation of microtubules was shown to be impaired in melanoma cells treated with ondansetron or tropisetron. Docking studies were used to predict that these drugs could bind to the colchicine binding site on the tubulin molecule. Antiemetic drugs, already given in combination with chemotherapy, may enhance the cytotoxic effect of chemotherapy, following successful delivery to the tumour site.

Fluvoxamine combination therapy with tropisetron for obsessive-compulsive disorder patients: A placebo-controlled, randomized clinical trial.

BACKGROUND: About 50% of obsessive-compulsive disorder patients still suffer significant symptoms even after the recommended first-line therapy. This demonstrates the necessity to investigate strategies to improve alleviation of symptoms. OBJECTIVE: The main objective of this study was to investigate the efficacy of a 5-hydroxytryptophan 3 receptor antagonist, tropisetron, as an adjuvant therapy to selective serotonin reuptake inhibitors, in ameliorating obsessive-compulsive disorder symptoms. METHODS: Men and women between the ages of 18-60 years diagnosed with obsessive-compulsive disorder, based on DSM5, who had a Yale-Brown obsessive compulsive scale score of more than 21 were recruited in a double-blinded, parallel-group, placebo-controlled, clinical trial of 10 weeks to receive either tropisetron (5 mg twice daily) and fluvoxamine (100 mg daily initially followed by 200 mg daily after week 4) or placebo and fluvoxamine. The primary outcome of interest in this study was the Yale-Brown obsessive compulsive scale total score decrease from baseline. RESULTS: One hundred and eight participants were equally randomized into two groups; 48 participants in each group finished the trial. The Yale-Brown obsessive compulsive total score significantly dropped in both groups while the tropisetron group participants experienced a significantly higher decrease in their scores (Greenhouse-Geisser F(1.53-65.87)=3.516, p-value=0.04). No major adverse effect was observed in any of the groups. CONCLUSION: This trial showed a significant efficacy for tropisetron over placebo in treatment of obsessive-compulsive disorder symptoms when added to fluvoxamine.