AGD1/USP10/METTL13 complexes enhance cancer stem cells proliferation and diminish the therapeutic effect of docetaxel via CD44 m6A modification in castration resistant prostate cancer.

Background: Most patients with prostate cancer inevitably progress to castration-resistant prostate cancer (CRPC), at which stage chemotherapeutics like docetaxel become the first-line treatment. However, chemotherapy resistance typically develops after an initial period of therapeutic efficacy. Increasing evidence indicates that cancer stem cells confer chemotherapy resistance via exosomes. This study demonstrated that AGD1, derived from prostate cancer stem cells (PCSCs), enhanced the stemness of prostate cancer cells and reduced the therapeutic effect of docetaxel in CRPC.

Methods: Quantitative real-time PCR (qPCR) was employed to determine the expression levels of AGD1 and METTL13 mRNAs in PCSCs and exosomes. Protein expression levels were examined using western blots and dot blots. The potential functions of AGD1 and METTL13 in CRPC were investigated through cell proliferation assay, Transwell assay, EdU incorporation assays, Annexin V-FITC/PI staining, and sphere formation assays. To uncover the underlying mechanisms of AGD1, RNA pull-down assay, RIP, co-Immunoprecipitation (co-IP), mass spectrometry (MS), Methylated RNA immunoprecipitation (MeRIP) and single-base elongation and ligation-based qPCR amplification method (SELECT) were performed. The effects of AGD1 and METTL13 on CRPC development and metastasis under docetaxel treatment were analyzed using a xenograft mouse model and an organoid model. Additionally, liposomal-chitosan nanocomplex drug delivery systems were designed to explore AGD1's role in regulating docetaxel treatment resistance in CRPC.

Results: AGD1 expression was upregulated in PCSCs and exosomes. Downregulating AGD1 enhanced the sensitivity of CRPC to docetaxel treatment by inhibiting their stemness, with the reverse also being true. RNA pull-down, combined with MS, co-IP and RIP assays, demonstrated that AGD1 binds to METTL13 and USP10, forming a complex that facilitates METTL13 protein accumulation through USP10-induced deubiquitination. MeRIP assay and SELECT assay revealed that METTL13 transcriptionally controls the mRNA decay of CD44 via m6A methylation. Additionally, this process activates the pSTAT3/PI3K-AKT signaling pathway. Organoid models and liposomal-chitosan nanocomplex drug delivery systems showed that reducing AGD1 expression enhanced the therapeutic effect of docetaxel in CRPC.

Conclusions: AGD1 mediates the stemness and apoptosis of PCSCs and promotes docetaxel treatment resistance by enhancing tumor growth and metastasis through USP10/METTL13-mediated CD44 mRNA decay in CRPC.