M2 tumor-associated macrophages regulate the migration and invasion of human bladder cancer cells via the TGF-β1/MYO1B pathway

Objective To preliminarily explore the effect and mechanism of tumor-associated macrophages (TAMs) on the migration and invasion of human bladder cancer cells. Methods THP-1 cells were stimulated with phorbol 12-myristate 13-acetate (PMA) to induce adhesion, followed by induction with interleukin (IL)-4 and IL-13 to polarize them into M2-type tumor-associated macrophages (M2 TAMs), thereby establishing an M2 TAM model. Using a 0.4 μm Transwell chamber, M2 TAMs and bladder cancer cell lines were co-cultured in a non-contact manner. The concentration of transforming growth factor-β1 (TGF-β1) in the supernatant of the co-culture media was measured by ELISA. Western blot was used to detect the expression of myosin ⅠB (MYO1B) in bladder cancer cells from three groups: monoculture, M2 TAM co-culture, and M2 TAM co-culture with TGF-β1 neutralizing antibody. Wound healing and Transwell invasion assays were performed to assess the migration and invasion abilities of bladder cancer cells treated with M2 TAM supernatant (with or without TGF-β1 neutralizing antibody), as well as after MYO1B overexpression or knockdown. Results The M2 TAM model was successfully established. The TGF-β1 concentration in the M2 TAM co-culture supernatant was significantly higher than that of the control group (P<0.001). After 72 h of co-culture with M2 TAMs, the migration rates and number of invaded T24 and 5637 bladder cancer cells significantly increased (P<0.01), and MYO1B expression in the cells was elevated compared with the control group. After the addition of TGF-β1 neutralizing antibody, the migration rate, invasion cell count, and MYO1B protein expression in T24 and 5637 cells were significantly reduced compared with the co-culture group (P<0.001). Overexpression of MYO1B significantly increased the migration rate and number of invaded cells in T24 and 5637 compared with the control and vector groups, while MYO1B knockdown significantly reduced them (P<0.001). Conclusions M2 TAMs promote the migration and invasion of bladder cancer cells by secreting TGF-β1, which upregulates MYO1B protein expression in these cells.