Table 1.

HER ligands and receptors.

Receptor homodimer/heterodimer	Ligands	Over-expression associated malignancies
EGFR (HER1)	EGF, TGF-α, AR, HB-EGF, EPG, EPR, BTC	NSCLC, breast, glioma, head and neck, bladder, kidney, soft tissue sarcoma
HER2/HER3	EPR, NRG1-α, NRG2-β	Breast
HER3	NRG1-β, NRG2-β	Breast, colon, gastric, prostate, other carcinomas, soft tissue sarcoma
HER4	HB-EGF, BTC, EPR, NRG1-β, NRG2-β, NRG4	Childhood medullo-blastoma
HER2/HER4	EGF, TGF-α, HB-EGF, EPR, BTC, NRG2-α, NRG3

EGF, epidermal growth factor; TGF, transforming growth factor; AR, amphiregulin; HB-EGF, heparin binding epidermal growth factor; EPG, epigen; EPR, epiregulin; BTC, betacellulin; NRG, neuregulin.