PNPO and paraganglioma: PNPO expression was significantly upregulated in BLCA, BRCA, CESC, COAD, ESCA, GBM, HNSC, LUAD, LUSC, PAAD, PCPG (pheochromocytoma and paraganglioma), PRAD, READ, STAD, and UCEC (Figure 1C), while PNPO was downregulated in CHOL, KICH (kidney chromophobe), KIRC, and THCA (Figure 1C) than the control group.