SLAMF8, a potential new immune checkpoint molecule,is associated with the prognosis of colorectal cancer

Recently, immune checkpoint inhibitors (ICIs), such as programmed cell death 1 (PD-1) monoclonal antibodies (mAbs), have revolutionized the treatment of malignant tumors. Therefore, the number of studies aiming to screen and identify new immune checkpoint molecules for antitumor immunotherapy is increasing. Signaling lymphocytic activation molecule (SLAM) family members are mainly expressed by and regulate the functions of immune cells. Recent studies have shown that several SLAM family members are involved in the regulation of the tumor immune microenvironment and are promising targets for antitumor immunotherapy. Signaling lymphocytic activation molecule family member 8 (SLAMF8) is a type I cell surface glycoprotein and is encoded on chromosome 1q21. To further illustrate the clinical value of SLAMF8 in colorectal cancer (CRC), we retrospectively analyzed the relationship between SLAMF8 expression and the prognosis of CRC patients and the associations between SLAMF8 expression and the expression levels of other SLAM family members and other classic immune checkpoint molecules using The Cancer Genome Atlas (TCGA) data, RNA sequencing data, tissue immunohistochemistry staining, and systematic follow-up analysis. Here, high SLAMF8 expression was associated with poor overall survival (OS) in CRC. The mRNA expression level of SLAMF8 was positively correlated with the expression levels of multiple classic immune checkpoints and other SLAM family members. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that the pathways enriched in CRC tissues with high SLAMF8 expression were associated with the regulation of the tumor immune microenvironment.