Cancer stem-like cells (CSCs) play pivotal roles in both chemoresistance and recurrence of many cancer types, including urothelial bladder cancer (UBC). In addition to intrinsic signaling pathways, extracellular cues from the tumor microenvironment (TME) are indispensable for the maintenance of CSCs. To better understand the mechanisms involved in TME-mediated generation and support of UBC CSCs, we focused on the role of cancer-associated fibroblasts (CAFs) in this study. Overexpression of miR-146a-5p in CAFs promoted CAF-to-UBC cell interactions, cancer stemness, and chemoresistance to treatment with gemcitabine and cisplatin. Mechanistically, miR-146-5p upregulated SVEP1 in CAFs by enhancing the recruitment of transcriptional factor YY1. Meanwhile, by targeting the 3’UTR of mRNAs of ARID1A and PRKAA2 (also known as AMPKα2) in UBC cells, CAF-secreted miR-146a-5p promoted cancer stemness and chemoresistance. Downregulation of ARID1A resulted in the inhibition of SOCS1 and subsequent STAT3 activation, and downregulated PRKAA2 led to the activation of mTOR signaling. Elevated levels of exosomal miR-146a-5p in the serum of UBC patients were correlated with both tumor stage and relapse risk. These findings altogether indicate that CAF-derived miR-146a-5p can promote stemness and enhance chemoresistance in UBC. Exosomal miR-146a-5p may be a biomarker of UBC recurrence and a potential therapeutic target.
Background
Docetaxel (DTX) is the most widely prescribed first-line chemotherapy for advanced prostate cancer (PCa). Unfortunately, DTX resistance invariably emerges, leading to worse prognosis of PCa. Growing evidence has shown that circRNAs had complex spatiotemporal specificity during the tumor development and oncogenesis. This study was designed to investigate the biological functions and possible molecular mechanisms of circRNAs in DTX resistance of PCa.
Methods
circRNAs in established DTX-resistant DU145 cell line were identified by RNA sequencing. Biological function of circCYP24A1 was verified in vitro and in vivo. The potential role of circCYP24A1 in the development of DTX-resistant PCa was investigated via dual-luciferase reporter assays, RIP assays and RNA pull-down assays. Univariate and multivariate logistic regression analyses was used to predict DTX-chemotherapy response based on patients’ clinical and biological information.
Results
CircCYP24A1 was identified to be upregulated in DTX-resistant DU145 cells. Upregulated circCYP24A1 was found to suppress the DTX chemosensitivity in vitro and in vivo. Furthermore, we found that circCYP24A1 promoted DTX resistance in PCa via regulating ALDH1A3 expression by sponging miR-1301-3p and activating PI3K/AKT/mTOR signaling pathway. Statistical analyses elucidated that circCYP24A1 was an independent risk factor to predict DTX response (OR = 0.165; 95% CI: 0.038–0.723; P = 0.017).
Conclusions
This study demonstrated that circCYP24A played an essential role in DTX resistance in PCa, suggesting that circCYP24A1 could be a promising biomarker to predict DTX response and a potential therapeutic target in PCa patients resistant to DTX chemotherapy.
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