Identification of Prognostic Biomarkers and Molecular Targets Among JAK Family in Breast Cancer

BACKGROUND: Janus kinases (JAKs) are a family of non-receptor tyrosine kinases involved in multiple malignancies. However, clinical values of JAKs as prognostic markers and potential mechanism as molecular targets in breast invasive carcinoma (BC) are not completely clarified. METHODOLOGY: TIMER, UALCAN and GEPIA were used to assess the expression and methylation levels of JAKs in BC. Kaplan–Meier Plotter, bc-GenExMiner, SurvExpress, TRGAted, MethSurv, and SurvivalMeth were used to assess the multilevel prognostic significance of JAKs in breast cancer patients. And cBioPortal, TIMER, STRING, GeneMANIA, NetworkAnalysis, LinkedOmics, DAVID 6.8, and Metascape were applied for multilayer networks and functional enrichment analyses. Correlations between immune cell infiltrates/their gene markers and JAKs were evaluated by TIMER. RESULTS: We first explored the expression and methylation level of JAKs in breast cancer and found significantly reduced JAK1 and JAK2 expression at mRNA and protein levels, significantly higher JAK3 protein expression, and significantly increased TYK2 expression at mRNA level but decreased at protein level. In addition, hypermethylation of JAK3 and TYK2 and hypomethylation of JAK1 were found in tumor samples. In terms of prognostic values of JAKs in BC patients, low transcriptional levels of JAK1, JAK2, JAK3, and TYK2 indicated worse OS/DMFS/PPS/RFS/DFS, inferior DFS, worse RFS, and shorter OS/DMFS/RFS, respectively. The mRNA signature analysis showed that high-risk group had unfavorable OS/RFS/MFS. Low JAK2 protein level indicated unfavorable DSS/PFS in BC patients. Five CpGs of JAK1, four CpGs of JAK2, 20 CpGs of JAK3, and 13 CpGs of TYK2 were significantly associated with prognosis in BC patients. The DNA methylation signature analysis also suggested worse prognosis in the high-risk group. For potential biological roles of JAKs, interaction analyses, functional enrichment analyses for biological process, cellular component, molecular function, and KEGG pathway analyses of JAKs and their neighbor genes in BC were conducted. Kinase targets, gene–miRNA interactions, and transcription factor–gene interactions of JAKs were also identified. Furthermore, JAKs were found to be significantly related to immune infiltrates as well as the expression levels of multiple immune markers in BC. CONCLUSION: JAKs showed multilevel prognostic value and important biological roles in BC. They might serve as promising prognostic markers and possible targets in breast cancer.