Table 2.

Natural molecules which target ErbB proteins.

Name	Target	Mechanism of action	Clinical applications/ in vitro or in vivo experiments	References
Epigallocatechin-3-gallate (EGCG)	EGFR ErbB2 ErbB3 ErbB4	Inhibits the binding of EGF to EGFR followed by inhibition of the signaling pathways Alters the lipid organization on the plasma membrane (lipid rafts) Promotes internalization of nonactivated EGFR monomer Reduces phosphorylation of EGFR	Clinical trial HNSCC; in vitro experiments: epidermoid carcinoma cell line (A-431)	[84, 85, 166, 167]
Quercetin	ErbB2 ErbB3	Reduces the expression level of ErbB2 and ErbB3 Reduces phosphorylation of ErbB2 and ErbB3	In vitro experiments: prostate cancer cell lines	[168, 169]
Curcumin	EGFR ErbB2	Induces degradation of ErbB2 by ubiquitination Induces EGFR degradation	In vitro experiments: EGFR in several lung adenocarcinoma cell lines; ErbB2 transfected COS7 cell line	[97, 98, 170]
Resveratrol	ErbB2	Downregulates ErbB2 gene Induces apoptosis	In vitro experiments: SK-BR-3 breast cancer cell lines	[171]
Apigenin	ErbB2 ErbB3	Inhibits ErbB2 autophosphorylation and transphosphorylation Depletes ErbB2 by polyubiquitination Inhibits the activity of ErbB2/ErbB3 heterodimer	In vitro experiments: BT-474, SK-BR-3 breast cancer cell lines	[172]

HNSCC, squamous cell carcinoma of the head and neck.