IL17A and colorectal cancer: Tumor-infiltrating γδT17 cells are the main IL-17-producing cells in human colorectal cancer, and activated γδT17 cells promote the proliferation of PMN-MDSCs by secreting cytokines such as IL-17, IL-8, TNF-α and GM-CSF, and maintain its immunosuppressive activity, promoting tumor progression (Wu et al., 2014b).