[Study on the correlation between high expression of GIT1 and M2 macrophage infiltration and prognosis in hepatocellular carcinoma].

<b>Objective:</b> To investigate the expression, prognosis, and role of G protein-coupled receptor kinase-interacting protein 1 (GIT1) in patients with hepatocellular carcinoma (HCC) tumor micro environments. <b>Methods:</b> Clinical data of 140 cases who underwent complete HCC surgical resection from January 2015 to December 2021 in Subei People's Hospital affiliated to Yangzhou University, Jiangsu Province, were included. Tumor tissue and adjacent tissue samples were collected for immunohistochemical analysis. The patients were divided into a high expression group and a low expression group according to the expression of GIT1. Cox regression was used to analyze the risk factors for prognosis in patients with HCC. Fifteen pairs of cancer tissues and adjacent tissues were randomly matched for quantitative polymerase chain reaction (RT-PCR), western blot (WB), and immunohistochemical analysis. GITI knockout or overexpression cell lines of human hepatoma cell lines HepG2, HuH7 and MHCC97-H, and mouse hepatoma cell line Hepa 1-6 were constructed. The effects on M2 macrophage polarization were analyzed by flow cytometry. A mice tumor model was constructed. The growth curve of tumor tissue overexpressing GIT1 was plotted. Bioinformatics analysis of the Cancer Genome Atlas (TCGA) data was performed using OncoLnc, Kaplan-Meier Plotter, UALCAN, and GEPIA databases to explore the differential expression of GIT1 in HCC patients and its effect on prognosis. <b>Results:</b> Bioinformatics analysis showed that the expression level of GIT1 was significantly higher in HCC tissues than in normal liver tissues (<i>P</i><0.05). RT-PCR and WB experiments showed that GIT1 was highly expressed in HCC. The follow-up results showed that high expression of GIT1 was associated with poor prognosis in patients with HCC. The high expression of GIT1 was an independent risk factor for the prognosis in patients with HCC (<i>HR</i>=2.562, 95%<i>CI</i>: 0.231-0.704, <i>P</i><0.05). Functional enrichment analysis combined with TIMER database analysis found that GIT1 expression level was associated with multiple immune cell infiltrations in HCC, but the correlation coefficient with macrophage infiltration was the highest (<i>r</i>=0.545, <i>P</i><0.001). Mice tumorigenesis experiments showed that the tumor volume of GIT1-overexpressing mice was significantly increased (<i>P</i><0.05). Additionally, flow cytometry indicated that after GIT1 overexpression, there was a low degree of M1 infiltration/polarization (wild type: 5.06%±0.11%, overexpression type: 4.09%±0.04%; <i>P</i><0.05) and a high degree of M2 infiltration/polarization (wild type: 10.20%±0.33%, overexpression type: 14.7%±0.12%; <i>P</i><0.05). <b>Conclusion:</b> GIT1 serves as a prognostic biomarker in HCC, promoting tumor progression through its high expression and enhances M2 macrophage infiltration.