Identification of new biomarkers in immune microenvironment of testicular germ cell tumour.

To seek novel prognostic biomarkers for testicular germ cell tumour (TGCT) and investigate the tumour immune microenvironment, we identified critical differentially expressed genes (DEGs) by overlapping GSE1818 dataset from Gene Expression Omnibus (GEO). Protein-protein interaction (PPI) network was used to investigate key modules and hub genes. Functional enrichment analysis was performed to investigate the underlying molecular functions of the DEGs in TGCT development and progression. The following survival analysis based on The Cancer Genome Atlas (TCGA) TGCT dataset indicated that AKAP4, SPA17 and TNP1 are correlated with TGCT prognosis. Immunohistochemistry and quantitative real-time polymerase chain reaction verified the down-regulation of the 3 hub genes in TGCT. Gene set enrichment analysis was conducted to further explore the role of the 3 hub genes in TGCT respectively. In addition, TGCT samples had high infiltration of CD8+ T cells, M0 and M1 macrophage cells, and resting myeloid dendritic cells in immune microenvironment. We also constructed the microRNA-gene regulatory networks to identify the key upstream microRNAs in TGCT. In conclusion, our findings indicated that AKAP4, SPA17 and TNP1 are promising biomarkers of TGCT. AKAP4 and TNP1 might regulate immune cells infiltration in immune microenvironment.