Distinctive profiles of tumor-infiltrating immune cells and association with intensity of infiltration in colorectal cancer

Tumor-infiltrating immune cells are heterogeneous and consist of characteristic compartments, including T helper (Th) 1 and regulatory T (Treg) cells that exhibit distinctive biological functions. The present study investigated the profile of infiltrating immune cells from surgically removed tumor tissues from patients with colorectal cancer. The characteristic transcription factors of Th1 and Th2 cells, Treg cells, Th17 cells and T follicular helper (Tfh) cells were analyzed. The results demonstrated that a marked increased number of Treg cells presented in tumor infiltrates when compared with non-tumor adjacent tissues. An increased number of Th1 and Tfh cells existed in tumor infiltrates compared with non-tumorous adjacent tissues, while the infiltration of Th17 and Th2 cells was similar between tumor and non-tumor adjacent tissues. Furthermore, there were an increased number of Treg cells in tumors with low infiltration compared with those with high infiltration. The expression of CXC motif chemokine (CXC) receptor 3, CXC ligand (CXCL)L9 and CXCL10 was significantly increased on infiltrating T cells in tumors with high infiltration as compared with those with low infiltration. Macrophages exhibited a dominant M2 phenotype in tumor infiltrates of colorectal cancer, whereas a balanced M1 and M2 phenotype presented in macrophages from the peripheral blood. In vitro stimulation of macrophages isolated from tumor tissue of colorectal cancer with granulocyte macrophage colony-stimulating factor and lipopolysaccharide did not drive to an inflammatory phenotype. The results provide insights into the pattern of immune cell infiltration in Chinese patients with colorectal cancer. It may be beneficial that patients with colorectal cancer are screened for the defined profile along with the expression of CXCL9 and CXCL10 in order to achieve better efficacy in clinical applications of immune-based therapy, including anti-programmed cell death protein 1 therapy.