Mechanism-inspired drug repurposing that augments standard treatments offers a cost-effective and rapid route toward addressing the burgeoning problem of plateauing of effective therapeutics for drug-resistant micrometastases. We show that the antibiotic minocycline, by its ability to minimize DNA repair via reduced expression of tyrosyl-DNA phosphodiesterase-1 (Tdp1), removes a key process attenuating the efficacy of irinotecan, a frequently used chemotherapeutic against metastatic disease. Moreover, minocycline and irinotecan cooperatively mitigate each other's undesired cytokine inductions of VEGF and IL8, respectively, thereby reinforcing the benefits of each modality. These mechanistic interactions result in synergistic enhancement of irinotecan-induced platinum-resistant epithelial ovarian cancer cell death, reduced micrometastases in the omenta and mesentery by >75%, and an extended overall survival by 50% in a late-stage peritoneal carcinomatosis mouse model. Economic incentives and easy translatability make the repurposing of minocycline as a reinforcer of the topoisomerase class of chemotherapeutics extremely valuable and merits further investigations. Mol Cancer Ther; 17(2); 508-20. ©2017 AACR.
©2017 American Association for Cancer Research.