Berbamine targets cancer stem cells and reverses cabazitaxel resistance via inhibiting IGF2BP1 and p‐STAT3 in prostate cancer

Abstract Background Cancer stem cells (CSCs) are a small subpopulation of tumor cells with the capability of self‐renewal and drug resistance, leading to tumor progression and disease relapse. Our study aimed to investigate the antitumor effect of berbamine, extracted from berberis amurensis, on prostate CSCs. Methods Sphere formation was used to collect prostate CSCs. The viability, proliferation, invasion, migration, and apoptosis assays were used to evaluate the antitumor effect of berbamine on prostate CSCs. Prostate CSC markers were analyzed by flow cytometry and qRT‐PCR. Small RNA sequencing analysis was conducted to analyse miRNAs. Exosomes were extracted using the ExoQuick‐TC kit and verified by testing exosomal markers using western blot. Results Berbamine targets prostate CSCs. Additionally, berbamine enhanced the antitumor effect of cabazitaxel, a second‐line chemotherapeutic drug for advanced prostate cancer, and re‐sensitized Cabazitaxel‐resistant PCa cells (CabaR‐DU145) to cabazitaxel by inhibiting ABCG2, CXCR4, IGF2BP1, and p‐STAT3. Berbamine enhanced the expression of let‐7 miRNA family and miR‐26b and influenced the downstream targets IGF2BP1 and p‐STAT3, respectively. Silencing CXCR4 and ABCG2 downregulated the expression of IGF2BP1 and p‐STAT3, respectively. Importantly, berbamine enhanced also levels of exosomal let‐7 family and miR‐26b, suggesting that berbamine possibly influences the expression of let‐7 family and miR‐26b through exosome delivery. Exosomes derived from berbamine‐treated CabaR‐DU145 cells re‐sensitized the cells to cabazitaxel. Conclusion Berbamine enhanced the toxic activity of cabazitaxel and reversed cabazitaxel resistance potentially through CXCR4/exosomal let‐7/IGF2BP1 and ABCG2/exosomal miR‐26b/p‐STAT3 axes.