Tim-3 promotes cell aggressiveness and paclitaxel resistance through the NF-κB /STAT3 signaling pathway in breast cancer

Abstract Background: T-cell immunoglobulin and mucin-domain containing molecule-3 (Tim-3) has been recognized as a promising target for cancer immunotherapy, but its exact role in breast cancer has not been fully elucidated. Methods: The gene expression level of Tim-3 in breast cancer and its prognostic significance were analysed. In vitro functions and associated mechanisms were then explored through establishing Tim-3 overexpressing breast cancer cells. Results: The gene expression level of Tim-3 was significantly higher (p<0.001) in breast cancer tissue compared to normal tissue following pooled analysis of the TCGA database. Tim-3 was a prognosis indicator in breast cancer patients as shown by KM-plotter (RFS: p=0.004; OS: p=0.099). Overexpression of the Tim-3 in Tim-3 low breast cancer cells promoted aggressiveness of breast cancer cells including proliferation, migration, invasion, tight junction deterioration and tumour-associated tubal formation. Furthermore, Tim-3 enhanced cellular resistance to paclitaxel. Tim-3 exerted its function by activating the NF-κB/STAT3 signalling pathway, and mediating gene regulation (upregulating CCND1, C-Myc, MMP1, TWIST, VEGF while downregulating E-cadherin). Additionally, Tim-3 downregulated tight junction molecules: ZO-2, ZO-1 and Occludin, which might further facilitate the tumour progression. Conclusions: Tim-3 plays a tumour-promoting role in breast cancer, suggesting that targeting Tim-3 may acquire a clinical benefit in antitumor therapy. Keywords: breast cancer, Tim-3, tight junction, chemoresistance, aggressiveness.