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The study aimed to investigate correlations between HHLA2 levels and parameters, including microsatellite instability (MSI) status, CD8+ cells, and histopathological features: budding, tumor-infiltrating lymphocytes (TILs), TNM scale, grading, cytokines, chemokines, and cell signaling moleculesin colorectal cancer (CRC). Furthermore, the immune infiltration landscape and HHLA2-related pathways in colorectal cancer using available online datasets were analyzed. The study included 167 patients diagnosed with CRC. Expression of HHLA2 was detected by immunohistochemistry method (IHC) and enzyme-linked immunosorbent assay (ELISA). The IHC was used to evaluate the MSI and CD8+ status. The budding and TILs were measured using a light microscope. The concentrations of cytokines, chemokines, and cell signaling molecules were measured to analyze the data by the Bio-Plex Pro Human cytokine screening panel, 48 cytokine assay, and principal component analysis (PCA). Geneset enrichment analysis (GSEA) was conducted to identify HHLA2-related pathways. The biological function of HHLA2 was predicted by Gene Ontology (GO). Analysis of the immune infiltration landscape of HHLA2 in colorectal cancer was made by the web-based tool Camoip. High HHLA2 expression was detected in CRC tumor tissues compared to the adjacent noncancerous tissues. The percentage of HHLA2-positive tumors was 97%. GSEA and GO showed that HHLA2 upregulation correlated with cancer-related pathways and several biological functions. Tumor-infiltrating lymphocytes score correlated positively with IHC HHLA2 expression level percentage. There was a negative correlation between HHLA2, anti-tumor cytokines and pro-tumor growth factors. This study provides a valuable insight into the role of HHLA2 in CRC. We reveal the role of HHLA2 expression as well as a stimulatory and inhibitory immune checkpoint in colorectal cancer. Further research may verify the therapeutic values of the HHLA2-KIR3DL3/TMIGD2 pathway in colorectal cancer. [ABSTRACT FROM AUTHOR]

The immunotherapies based on ICIs in CRC are nowadays limited to microsatellite unstable tumours which are approximately 15% of all CRC cases. There are a few new immune checkpoints belonging to the B7 family, including B7H4. B7H4 expression is associated with so-called "cold tumours", and its function is linked to the downregulation of various immune cell populations. Our study aimed to investigate whether B7H4 expression is dependent on microsatellite status in CRC and on elucidating the immunological context in which the expression of B7H4 occurs. We enrolled 167 patients in the study. We prepared the homogenates from tumour tissues and healthy adjacent tissue to assess the B7H4 levels and the Bio-Plex Pro Human 48-cytokine panel. We assessed the microsatellite status of the tumour, B7H4 expression, CD8+ T cell population, and the TILs and budding in H + E stained slides by the IHC method. We used an online available database for further exploring the biological characteristics of B7H4. The expression of B7H4 was more frequent in microsatellite stable tumours, and was negatively associated with TILs. B7H4 is positively correlated with antitumour immunosuppressive iTME, thus contributing to the immunosuppressive environment in CRC. [ABSTRACT FROM AUTHOR]