GDF6 and pheochromocytoma-paraganglioma: Conversely, GDF6 showed tumor-specific upregulation in seven cancer subtypes, notably pan-kidney cohort (KIPAN), head and neck squamous cell carcinoma (HNSC), kidney renal clear cell carcinoma (KIRC), ovarian serous cystadenocarcinoma (OV), pancreatic adenocarcinoma (PAAD), pheochromocytoma and paraganglioma (PCPG), and adrenocortical carcinoma (ACC) (Figure 1B–D).