표피성장인자(epidermal growth factor, EGF)는 1962년 Cohen이 처음으로 쥐의 하악 타액선에서 분리한 분자량이 6045 dalton인 single-chain polypeptide hormone으로 세포의 성장 및 분화를 자극하는 것으로 알려졌다. EGF가 세포들에서 mitogen으로 작용하기 위해서는 표피성장인자 수용체(epidermal growth factor receptor, EGFR)와 결합하여야 한다. EGFR은 분자량이 170,000dalton의 변형막 당단백(transmembtane glycoprotein)으로써 cysteine이 풍부한 외세포 리간드 결합영역(intracellular tyrosin kinase doman)으로 구성되어 있으며, 그 기능은 paracrine 방법으로 EGF와 EGFR은 정상 및 비정상 세포에서의 증식 및 분화에 관여하는 것으로 알려져 있다. 특히 EGF가 세포의 발암현상(carcinogenesis)에 관여한다는 근거로 1986년 Stoscheck 등에 의하여 널리 증명되었으며 그후 많은 연구업적들이 암과 EGFR과의 상관관계에 대하여 진행되어 왔다.

It has been investigated over recent decades that the molecular mechanisms involved in the development and uncontrolled proliferation of cancers involve abnormalities of oncogenes and growth factor-receptor systems. Epidermal growth factor(EGF) is a single-chain polypeptide(MW 6045) that was first isolated from the mouse submaxillary gland by Cohen in 1962. It is known that the epidermal growth factor-stimulated growth regulatory system is involved in cellular proliferation, both normal and neoplastic(Cowley et al., 1986 ; Ozanne et al., 1986 ; Stoscheck et al., 1986 ; Fixher et al., 1990). In order for EGF to interact with the cell, a specific receptor located at the cell surface is required. Epidermal growth factor receptor(EGFR) is a 170 KDa membrane-bound glycoprotein encoded for by the c-erbB-1 oncogene. It was first purified from the A431 cellline which was derived from the epidermoid carcinoma of the vulva(Cohen, 1983 ; Carpenter et al., 1986 ; Carpenter et al., 1987 ; Yarden et al., 1988). EGFR is a member of growth factor receptor family of protein tyrosine kinases, a class of cell cycli regulatory molecules. The receptor is capable of binding several ligands such as EGF, transforming growth factor(TGF)a(Fisher et al., 1990), amphiregulin(Shoyab et al.,1989), and heparin-binding EGF(Higashiyama et al., 1991). It is activated when its ligand binds to the extracellular domain, resulting in autophosphorylation of the receptor`s intracellular tyrosine kinase domain(Cohen et al., 1980 ; Schreiber et al., 1983). Dimerization, conformational changes ans internalization of EGFR function to transmit intracellular signals leading to regulation of cell growth(Carpenter and Cohen, 1979).