Discovery of inhibitors of membrane traffic from a panel of clinically effective anticancer drugs

Abstract

In addition to their major targets, clinically effective drugs may have unknown off-targets. By identifying such off-targets it may be possible to repurpose approved drugs for new indications. We are interested in the Golgi apparatus as a novel target for cancer therapy, but there is a paucity of candidate Golgi-disrupting drugs. Here, we aimed to identify Golgi-disrupting compounds from a panel of 34 approved anticancer drugs by using HBC-4 human breast cancer cells and immunofluorescence microscopy to visualize the Golgi apparatus. The screen identified five drugs having Golgi-disrupting activity. Four of them were vinca alkaloids (vinorelbine, vindesine, vincristine and vinblastine), and the fifth drug was eribulin. This is the first study to demonstrate that vinorelbine, vindesine and eribulin possess Golgi-disrupting activity. The 5 drugs are known to inhibit tubulin polymerization and to induce microtubule depolymerization. Interestingly, a microtubule-stabilizer paclitaxel did not induce Golgi-disruption, suggesting that the three-dimensionally preserved microtubules are partly responsible for maintaining the Golgi complex. Concerning eribulin, a noteworthy drug because of its high clinical efficacy against advanced breast cancer, we further confirmed its Golgi-disrupting activity in three different human breast cancer cell lines, BSY-1, MDA-MB-231 and MCF-7. Golgi-disruption may contribute to anticancer efficacy of eribulin. In conclusion, the present study revealed that four vinca alkaloids and eribulin possessed potential Golgi-disrupting activity among a panel of 34 approved anticancer drugs. Other drugs covering various molecular-targeted drugs and classical DNA-damaging drugs showed no Golgi-disrupting effect. These results suggest that tubulin polymerization-inhibitors might be promising candidate drugs with Golgi-disrupting activity.