Purpose: Paired Box 5 (PAX5) is a transcription factor that is widely associated with carcinogenesis. PAX5 can maintain Epstein-Barr virus (EBV) latency in B cells, while a close association exists between EBV infection and nasopharyngeal carcinoma (NPC). However, there are very few reports on the correlation between PAX5 and NPC development. The aim of this study was to investigate the role of PAX5 in NPC.
Patients and Methods: The clinical value and prognostic significance of PAX5 in NPC and the association with PAX5 expression and immune cell infiltration were analyzed by multiple GEO datasets. In vivo and in vitro experiments including real-time PCR, Western blot, CCK-8 assay, and methylation sequencing were used to validate the results of bioinformatics analysis.
Results: The expression of PAX5 was significantly reduced in NPC tissues, with the low expression being correlated with advanced clinical stage, low tumor mutation burden and immune activation, high relative expression of EBV, poor survival for NPC patients. PAX5 exhibited excellent diagnostic performance and had potential as a predictive factor for response to the immune checkpoint inhibitors therapy. Enrichment analysis suggested that the low expression of PAX5 was associated with the dysregulation of Hippo and Wnt signaling pathways. The promoter of PAX5 gene was hypermethylated in NPC tissues. Furthermore, the in vitro and in vivo experiments revealed that NPC tissue and cell lines had low mRNA expression levels of PAX5, the PAX5 promoter was hypermethylated in NPC cell lines, and PAX5 overexpression inhibited NPC cell proliferation and tumor growth in nude mice.
Conclusion: PAX5 may be a tumor suppressor and serve as a novel potential diagnostic and prognostic marker for NPC.

Keywords: nasopharyngeal carcinoma, transcription factor, PAX5, prognosis, immunity, Epstein-Barr virus