Abstract:  Objective To investigate the expression of UBQLN2 gene in colon cancer and its immunoregulatory function. Methods Colon cancer and their matched paracancer tissues surgically removed in the First Affiliated Hospital of Hebei North University from January 2021 to June 2023 were collected. The expression of UBQLN2 was detected by transcriptome sequencing, the expression level of UBQLN2 mRNA was detected by qRT⁃PCR, and the expression of UBQLN2 protein was detected by immunohistochemical. The relationship between the expression of UBQLN2 and the clinical pathological characteristics and prognosis of colon cancer patients was analyzed. Multicolor immunofluorescence was used to detect the co⁃expression of UBQLN2 and TGF⁃β. Single⁃cell transcriptome sequencing and TCGA database were used to verify the expression of UBQLN2 in colon cancer and its relationship with immunosuppressive factors, TGF⁃β and prognosis of colon cancer. Results Transcriptome analysis showed that UBQLN2 gene was significantly overexpressed in colon cancer tissues, and its mRNA expression level was higher than that in cancer⁃adjacent tissues (P<0.01). The relative expressions of UBQLN2 mRNA in 275 colon cancer tissues and 41 paracancer tissues which collected from TCGA database were also significantly higher in colon cancer tissues than that in cancer⁃adjacent tissues (P<0.001). Immunohistochemical results showed that UBQLN2 was mainly expressed in the cytoplasm, and the positive expression intensity of UBQLN2 protein in colon cancer tissues was obviously higher than that in  cancer⁃adjacent tissues. The results of qRT⁃PCR showed that UBQLN2 mRNA expression in colon cancer tissues was significantly higher than that in cancer⁃adjacent tissues (P<0.001). Pathway enrichment analysis showed that the tumor proliferation pathway was significantly up⁃regulated, and the immune activation pathway was significantly down⁃regulated in the UBQLN2 high expression group. Moreover, compared with UBQLN2 low expression group, UBQLN2 high expression group had higher immune escape score (P<0.05), lower expression of CD8+ T cell specific markers, smaller immune recruitment factors and immune killer factors (all P<0.05), and higher expression of immune depletion molecules (all P<0.05). The expressions of TGF⁃β, IL10, ARG1 and other immunosuppressive cytokines in UBQLN2 high expression group were higher than those in UBQLN2 low expression group (all P<0.05), and UBQLN2 was positively correlated with TGF⁃β expression (r=0.280, P<0.0001); UBQLN2 and TGF⁃β were co⁃expressed in tumors. Patients with both high expression of TGF⁃β and UBQLN2 had worse prognosis than those with both low expression (P=0.004). Single⁃cell transcriptome sequencing showed that colon cancer with high expression of UBQLN2 was highly expressed TGF⁃β and the microenvironment was immunosuppressed. Conclusions UBQLN2 is highly expressed in colon cancer and associated with poor prognosis. Colon cancer with high expression of UBQLN2 may inhibit the killing activity of CD8+T cells by releasing TGF⁃β cytokines and realizing immune escape. UBQLN2 may be a potential molecular target for the treatment of colon cancer.

Key words: Colon cancer')">Colon cancer, Immunosuppression, UBQLN2, TGF?-β