Sulforaphane Enhances the Anticancer Properties of Paclitaxel in Two Human Derived Prostate Cancer Cell Lines

Abstract

Abstract Background: In cancer therapy, combined treatment results in additive and synergistic outcomes and reduces the development of drug resistance in response to anticancer agents compared with monotherapy. We propose that when Paclitaxel (Taxol, PTX) is combined with Sulforaphane (SFN), may result in better treatment outcomes in prostate cancer. Understanding the mechanism of drug synergy, as opposed to simply knowing which drugs to combine, enables further optimization of advantageous drug interactions and can provide efficient therapeutic strategies in preclinical research. Methods: We measured apoptosis, cell cycle, and expression of Bax and Bcl2 in response to the PTX and SFN individual and combined treatments. Cell lines (PC-3) and (LNCaP), were individually treated with different concentrations of PTX, SFN, and its combination. Annexin V/PI positivity and data analysis were conducted using a flow cytometer and guava data acquisition and analysis software. Graph-Pad Prism 6, and Microsoft Excel software were used for statistical analyses and graphs generation. Student’s t-tests or one-way analysis of variance with Tukey’s correction were used to determine the significant difference between mono- and combination treatments.Results: The effect of the PTX or SFN treatments on reducing cell viability increased in a dose-dependent manner. Combined treatment enhanced PTX’s effects and reduced the EC50 values of both drugs compared to individual treatments. Flow cytometry analysis revealed that PTX or SFN treatments redistributed cell-cycle phases by inducing S-phase arrest and increasing apoptotic cell population in PC-3 cells. Such effects were enhanced in the PTX+SFN combination group. Interestingly, the necrotic cells were not affected by the combination treatments. Caspase-3 cleavage and morphological deformations of the cell nuclei are signs of apoptotic cell death; such parameters were examined by western blot and fluorescent microscopy in response to mono- and combination treatments.Conclusion: The PTX or SFN differentially modulated the expression of Bax and Bcl2 in PC-3 and LNCaP cell lines, and the combined treatment enhanced these effects in favor of cell apoptosis versus survival. Our data indicated that combination therapy of PTX and SFN significantly increased Bax protein expression and Bax: Bcl2 ratio compared to PTX or SFN individual treatments. Such findings will help develop new biomarkers and guide therapy choices.