Urinary bladder cancer (UBC) is one of the most common malignancies worldwide. UBC patients at muscle invasive stage have poor clinical outcome, due to high propensity for metastasis. Non-tumor activated fibroblasts, named α-SMA+Fs, is similar to carcinoma-associated fibroblasts (CAFs) which could express α-SMA. However, whether α-SMA+Fs patients could induce UBC cell invasion is unclear. Herein, we found that characterization of primary α-SMA+Fs separated from PBOO (partial bladder outlet obstruction) rats was fell in between normal fibroblasts (α-SMA-Fs) and CAFs. Additionally, the conditional medium from α-SMA+Fs enhanced the NBT-II cell invasion through inducing EMT, and the oncogenic function of mixed supernatant of α-SMA+Fs/CAFs was stronger than that of CAFs. Inhibition of TGF-β1 by TGF-β1 neutralizing antibody decreased the EMT-associated gene expression and NBT-II cell invasion, suggesting that α-SMA+Fs can induce tumor EMT through TGF-β1. Xenograft experiments showed that the tumorigenic effect of α-SMA+Fs in mice was also between CAFs and α-SMA-Fs, and α-SMA+Fs/CAFs also had a strong tumorigenic effect. We preformed rats with PBOO and found that the incidence of invasive bladder cancer in PBOO+BBN group was higher than in BBN group, suggesting the PBOO treatment contributed to tumorigenesis. Thus, α-SMA+Fs promoted tumorigenesis by secreting TGF-β1 to induce EMT.

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