Background: Testicular cancer severely affects male health, so finding effective diagnosis and prognostic indicators and exploring its pathogenesis are very important.
Purpose: This study aims to explore the hub genes that play important roles in the occurrence and development of testicular germ cell tumor (TGCT).
Methods: Data were obtained from Gene Expression Omnibus datasets (GSE3218 and GSE1818) and verified in The Cancer Genome Atlas database and the Genotype-Tissue Expression database and the Human Protein Atlas database. A protein-protein interaction network was constructed to obtain hub genes. GEO2R, R software and packages were used to analyze differentially expressed genes (DEGs), receiver operating characteristic curve assessment, Cox regression analysis, Kaplan-Meier survival curve assessment, Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, the relationship with clinicopathological information, gene set enrichment analysis, the correlation with immune cells’ infiltration, and the expression in pan-cancers of the hub genes.
Results: PLK4, TRIP13, TPR, KIF18A, CDKN3, HMMR, PBK, PTTG1, CKS2, SYCP1, HSPA2 , and MKI67  were selected as the hub genes. mRNA of PLK4, TRIP13, CDKN3, SYCP1, HSPA2 , and MKI67  had high diagnostic values, and higher expression of CDKN3  and HSPA2  mRNA were poor prognostic factors for progression-free interval of TGCT. The hub genes involved organelle division and cell cycle, chromosome and centromeric region, heat shock protein binding, and more. Downregulated TPR  and PLK4  were selected as research targets for continued study, and they may participate in multiple signaling pathways. The expression of TPR  and PLK4  correlated with the infiltration of a variety of immune cells and differed in pan-cancers.
Conclusion: The mRNA levels of multiple hub genes have high diagnostic and prognostic values for TGCT. TPR  and PLK4  may play a role in the occurrence and development of TGCT through cancer-related signaling pathways.
Keywords: testicular cancer, mRNA, hub gene, diagnosis, prognosis, biomarker, immune infiltration, signal pathway