Objective To explore the mechanism that macrophages promote epithelial-mesenchymal transformation (EMT) in bladder cancer cells. Methods A total of 137 tissues of bladder cancer (BC) were collected from Department of Urological Oncology of Chongqing University Cancer Hospital between 2000 and 2015. Immunohistochemical (IHC) assay was used to detect the expression of CLDN10 in 137 bladder cancer specimens, and statistical analysis was used to investigate the association in CLDN10 expression and clinical features. In mouse RAW264.7 macrophages and bladder cancer MB49 cells, siRNA technology was used to knockdown the expression of TNF-α in RAW264.7 cells. Western blot assay was performed to detect the levels of related protein expression of EMT in MB49 cells, while immunofluorescence assay was used to detect the combination of CLDN10 and β-catenin. Plate clone formation assay was performed to detect the levels of related protein expression of EMT in MB49 cells and RAW264.7 cells. Results In 137 samples, the proportion of overexpression of CLDN10 was 49.6% (68/137). Overexpression of CLDN10 was positively correlated with tumor(P=0.014) and lymphatic metastasis (P=0.005), and was negatively correlated with survival time(P=0.048) and recurrence-free survival (P=0.008). Treatment of exogenous TNF-α led to accumulation of CLDN10 in BC cell nucleus. The results of Western blotting showed the levels of EMT related proteins Vimentin, Snail and Twist were up-regulated(P < 0.05). Adversely, repression of TNF-α in macrophages resulted in decrease of the levels of EMT related proteins, Vimentin, Snail and Twist (P < 0.05). The levels of expression of Vimentin, snail and Twist were increased while the level of E-cadherin was decreased(P < 0.05) in MB49 cells after co-culturing of RAW264.7 cells and MB49 cells. Conclusion Macrophages can modulate BC cell proliferation and EMT progression by secreting TNF-α to regulate CLDN10/β-catenin mediated signaling pathway.
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