The Proapoptotic Effect of MB-653 Is Associated with the Modulation of Metastasis and Invasiveness-Related Signalling Pathways in Human Colorectal Cancer Cells

Colorectal cancer is one of the most common cancers worldwide and has a high mortality rate. In this study, we investigated the cytotoxic, proapoptotic, and anti-invasive effects of the synthetic indole phytoalexin MB-653. The antiproliferative effect was determined using an MTT assay, showing IC values of 5.8 ± 0.3 μmol/L for HCT116 cells and 6.1 ± 2.1 μmol/L for Caco2 cells. Flow cytometry and Western blot analysis were employed to investigate the molecular mechanisms underlying cytotoxicity, proapoptotic action, and anti-invasion effects. The proapoptotic activity was evidenced by the activation of caspases 3 and 7, mitochondrial dysfunction, and an increased number of apoptotic cells, confirmed by annexin V/PI and AO/PI staining. Additionally, MB-653 induces dose-dependent G2/M phase cell cycle arrest, the cause of which could be cyclin B1/CDC2 complex dysfunction and/or a decrease in α-tubulin protein expression. Another important observation was that MB-653 modulated several signalling pathways associated with various cellular activities, including survival, proliferation, tumour invasiveness, metastasis, and epithelial-mesenchymal transition (EMT). We further demonstrated its safety for topical and parenteral application. To sum up, our results indicate the real potential of MB-653 in treating colorectal cancer.