Single cell and microarray data collection
Single-cell data were obtained from GSE150430. Data from 15 NPC tumor and 1 normal biopsies were used for global analysis. Epithelial cells were identified using EPCAM, KRT5, KRT15 and KRT19. ENOX2 expression in malignant tumor cells were obtained from 11 patients. ENOX2 expression was indicated by color scale. Data visualizations were generated by plotly. NPC gene expression profiling datasets GSE34573, GSE53819 and GSE12452, and gene methylation profiling datasets GSE52068 were obtained from the gene expression omnibus (GEO, https://www.ncbi.nlm.nih.gov/geo/) database of The National Center for Biotechnology Information. GSE12452 contained 31 NPC specimens and 10 normal nasopharyngeal tissues, GSE53819 included 18 NPC and 18 normal specimens whereas GSE34573 included 13 NPC specimens and 3 normal nasopharyngeal tissues excised by laser microdissection. The datasets were based on the GPL570 [HG-U133_Plus_2] Affymetrix Human Genome U133 Plus 2.0 Array platform. GSE52068 used Infinium Human Methylation 450K BeadChip and the probes targeted CpG sites of genes. CpG sites are usually found at or near transcription start site (TSS), so high level of methylation of CpG might lead to suppressed expression of RNA transcripts.

Statistics

Differences in quantitative variables were analyzed by the Mann–Whitney U test when comparing 2 groups and by the two-way ANOVA or Kruskal-Wallis with Dunn’s post-test when comparing >2 groups when appropriate. A p value < 0.05 was considered as statistically significant.