Amlodipine exerts inhibitory effects against glioma stem cells through degrading EGFR and down-regulating its downstream pro-survival pathways

Glioblastoma is the most aggressive and lethal primary brain tumor in adults with the poorest prognosis, due to its high therapeutic resistance and rapid recurrence, which is closely associated with glioma stem cells (GSCs), which represent a critical therapeutic target in this refractory malignancy. As a classical calcium channel blocker (CCB), amlodipine exhibits exact anti-tumor effect independent of CCB activity. The present study further investigated its effects on GSCs and elucidated the relevant molecular mechanisms. Our results revealed that amlodipine exerted multifaceted inhibitory effects on GSCs, including reducing cell viability, self-renewal, invasiveness, and stemness, while enhancing apoptosis and suppressing intracranial tumor growth derived from GSCs. In contrast, other dihydropyridine CCBs and calcium chelators did not exhibit comparable anti-GSC effects at equivalent concentrations, suggesting that the anti-GSC activity of amlodipine is independent of calcium channel blockade. Mechanistically, amlodipine demonstrated high binding affinity to EGFR on the plasma membrane of GSCs, triggering its internalization via clathrin-independent lipid raft-mediated endocytosis. This process leaded to the lysosomal degradation of EGFR, resulting in the downregulation of EGFR protein levels and subsequent inhibition of downstream pro-survival signaling pathways. Taken together, our studies suggest that amlodipine suppresses GSCs-initiated tumor development via degrading EGFR and down-regulating its downstream pro-survival pathways, implying that amlodipine has novel potential as a therapeutic agent targeting GSCs in glioblastoma, deserving further investigations.