REN and cancer: Expression of components of the renin-angiotensin system (RAS) by CSCs has been demonstrated in different cancer types including glioblastoma (64), OCSCC affecting the oral tongue (65), buccal mucosa (66), and lip (67) squamous cell carcinoma (SCC), primary HNcSCC (68), metastatic colon adenocarcinoma (42), and metastatic malignant melanoma (43).