Background: T-cell immunoglobulin mucin 3 (TIM3) is a negative immune checkpoint and plays a crucial part in tumor-induced immune suppression. However, the mechanism of TIM3 in regulating immunosuppression in head and neck squamous cell carcinoma (HNSCC) was still not quite clear.
Methods: We carried out the immunohistochemistry staining of HNSCC tissue microarrays. Through quantification of the histoscore, we performed the correlation analysis among the TIM3, Galectin-9, Foxp3, CD68 and CD163. The effects of TIM3 on regulatory T cells (Tregs) and macrophages were detected by utilizing the Tgfbr1/Pten 2cKO HNSCC mouse model. Flow cytometry were used to analysis the percent of Tregs, macrophages and IFN-γ.
Results: We demonstrated the close association among TIM3/Galectin-9 pathway, regulatory T cell marker (Foxp3) and macrophage marker (CD68, CD163) in human HNSCC. In the transgenic HNSCC mouse model, blockade of TIM3 by the anti-TIM3 monoclonal antibody induced a reduction of CD4+CD25+Foxp3+ Tregs. Meanwhile, the population of TIM3+ Tregs was also decreased. However, the population of CD206+ macrophages was not significantly declined. The increased IFN-γ production on CD8+ T cells in anti-TIM3 treatment mice showed that the antitumor immune response was enhanced through suppression of these negative immune factors.
Conclusions: The present study demonstrated that TIM3 was associated with the immunosuppression in HNSCC. And targeting TIM3 can enhance anti-tumor immune response by decreasing Tregs in HNSCC.
Keywords: Head and neck cancer; Immune checkpoint; Immunosuppression; Immunotherapy; Macrophages; Tregs.