Fibroblasts from pBOO promote tumorigenesis by secreting TGFbeta1 to induce EMT in bladder urothelial carcinoma cells

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.