Pseudogene HLA-DRB6 Regulates Immune Microenvironment of Cutaneous Melanoma by miR-338/CXCL10 Axis
Abstract Background: The relationship between the pseudogene and tumor immune microenvironment in cutaneous melanoma is unclear. In this study, we analyzed the role of the pseudogene HLA-DRB6 and its effect on the tumor immune microenvironment in skin cutaneous melanoma (SKCM) using bioinformatics tools. Method: The GEPIA database was used to analyze the expression of HLA-DRB6 and CXCL10 mRNA in tumor tissues. The TIMER database was used to analyze the relationship between mRNA levels and the infiltration of immune cells. The enrichment of HLA-DRB6 and CXCL10 in melanoma tissues was analyzed by single cell portal. The binding sites of HLA-DRB6 with its target genes was predicted via starBase database. The gene expression profiling and clinical data from GEO database (GSE94873) was used to verify the potential of CXCL10 as a biomarker. Result: The expression of HLA-DRB6 in SKCM tumor is higher than in normal tissues, and patients with high HLA-DRB6 expression had a better prognosis (P<0.05). Furthermore, HLA-DRB6 is positively correlated with the infiltration of immune cells such as B cells, CD4+ T, and CD8+ T lymphocytes, and the expression of immune checkpoint molecules such as PD-1, PD-L1, and CTLA-4. Single cell transcriptome sequencing data showed that HLA-DRB6 is mainly enriched in macrophages and had the highest correlation with CXCL10 than other chemokines (cor=0.66, P<0.0001). In addition, we found that CXCL10 can be used as a potential biomarker for predicting responsiveness and survival rate in SKCM patients who treated with Tremelimumab (a human anti-CTLA-4 antibody). Conclusion: In the microenvironment of SKCM, HLA-DRB6 is mainly enriched in macrophages and regulates the expression of CXCL10 through the ceRNA mechanism. Furthermore, the CXCL10 in peripheral blood can be used as a biomarker to predict the responsiveness and the prognosis for patients treated with tremelimumab.