Synergistic Effects of Paclitaxel and Sulforaphane in Prostate Cancer Treatment: Mechanistic Insights for Optimizing Combination Therapy

Abstract

Background: In cancer therapy, combining treatments can result in additive and synergistic outcomes, reducing the development of drug resistance compared with monotherapy. We propose that combining Paclitaxel (Taxol, PTX) 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 individual and combined treatments of PTX and SFN in PC-3 and LNCaP cells. Different concentrations of PTX, SFN, and their combination were used. We conducted Annexin V/PI positivity and data analysis using a flow cytometer and guava data acquisition and analysis software. Statistical analyses and graph generation were performed using Graph-Pad Prism 6 and Microsoft Excel software. 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 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 the apoptotic cell population in PC-3 cells. These effects were further enhanced in the PTX+SFN combination group. Interestingly, the combination treatments did not affect the necrotic cells. Caspase-3 cleavage and morphological deformations of the cell nuclei were examined by western blot and fluorescent microscopy in response to mono- and combination treatments, indicating apoptotic cell death. Conclusion: The PTX or SFN treatments 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. These findings could help develop new biomarkers and guide therapy choices. Understanding the mechanism of drug synergy is essential to optimize drug interactions and provide efficient therapeutic strategies in preclinical research.