SummaryIt has been reported that functionally distinct cancer stem cells (CSCs) exist in human bladder cancer (BCa). Here, we found that Sox2, a transcription factor that is well characterized as a marker for stem cells, is upregulated in both mouse and human BCa. Sox2 expression is absent in normal urothelial cells, but it begins to be expressed in pre-neoplastic bladder tumors and continues to be expressed in invasive mouse BCa. Using s as a reporter of Sox2 transcriptional expression, we demonstrated that Sox2-expressing cells mark a subpopulation of tumor cells that fuel the growth of established BCa. SOX2-positive cells also expressed other previously reported BCa CSC markers, including Keratin14 (KRT14) and CD44v6. Ablation of Sox2-expressing cells within primary invasive BCa led to enhanced tumor regression, supporting the essential role of SOX2-positive cells in regulating BCa maintenance and progression. Our data show that Sox2 is a marker of bladder CSCs and indicate it as a potential clinical target for BCa therapy.

MicroRNAs (miRNAs) have been reported to participate in many biological behaviours of multiple malignancies. Recent studies have shown that miR‐15b‐5p (miR‐15b) exhibits dual roles by accelerating or blocking tumour progression. However, the molecular mechanisms by which miR‐15b contributes to prostate cancer (PCa) are still elusive. Here, miR‐15b expression was found significantly up‐regulated in PCa in comparison with the normal samples and was positively correlated with age and Gleason score in patients with PCa. Notably, PCa patients with miR‐15b high expression displayed a higher recurrence rate than those with miR‐15b low expression (P = 0.0058). Knockdown of miR‐15b suppressed cell growth and invasiveness in 22RV1 and PC3 cells, while overexpression of miR‐15b reversed these effects. Then, we validated that RECK acted as a direct target of miR‐15b by dual‐luciferase assay and revealed the negative correlation of RECK with miR‐15b expression in PCa tissues. Ectopic expression of RECK reduced cell proliferation and invasive potential and partially abrogated the tumour‐promoting effects caused by miR‐15b overexpression. Additionally, miR‐15b knockdown inhibited tumour growth activity in a mouse PCa xenograft model. Taken together, our findings indicate that miR‐15b promotes the progression of PCa cells by targeting RECK and represents a potential marker for patients with PCa.

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