Caffeine May Improve the Chemotherapeutic Effect of Docetaxel by Inducing UPR and Autophagy in Breast Cancer Cells

Breast cancer is the most frequently diagnosed cancer type among women. Chemotherapeutics are widely used for breast cancer treatment but acquired drug resistance is the main reason that limits their efficacy. Therefore, there is a continuing need for more effective treatment approaches with fewer side effects. One of the naturally occurring xanthine in coffee beans, caffeine is the most commonly used psychoactive substance worldwide. Numerous studies have drawn attention to the health benefits of coffee intake including decrement in risk of heart disease and risk of some cancers. Docetaxel is a second-generation antineoplastic agent of the taxane family and is widely used in the treatment of numerous cancers such as breast cancer. Herein, we evaluate the effect of caffeine and its combination with docetaxel on MCF-7 breast cancer cells. To test the effect of caffeine and its combination with docetaxel, we evaluate the autophagy, ubiquitin-proteasome system, unfolded protein response signaling and apoptosis-related protein levels were examined by immunoblotting. Cell viability was measured by WST-1 method. Morphological alterations in cells were evaluated in microscopical examinations. We found that caffeine remarkably induced UPR signaling, accelerated autophagic flux, and UPS-dependent protein turnover. Co-administration of caffeine and docetaxel strongly diminished the viability of MCF-7 cells by expanding the cytotoxic effect of docetaxel through accelerating the UPS-dependent protein turnover, induction of autophagy and apoptotic protein levels in a manner dose-dependently. Our results suggest that caffeine supplementation with docetaxel may expand the chemotherapeutic efficiency of docetaxel in breast cancer.