<Original Articles>Relation of Epidermal Growth Factor Receptor Concentration to Growth of Human Esophageal Cancer Cell Lines

Abstract

The relation between the concentration of epidermal growth factor (EGF) receptor and the effects of EGF on cell proliferation were studied using 16 newly established human esophageal cancer cell lines. According to 125_I-EGF binding assay, the amount of EGF receptor was found to vary from 6×10_4 to 1. 2×10_7 (sites/cell). Changes in EGF-stimulated tyrosine-specific protein kinase activity almost paralleled changes in the number of EGF receptors per cell. Amplification of EGF receptor gene was detected in only one cell line. Under monolayer culture conditions, we found three types of growth responses of esophageal cell lines to EGF; growth in 5 cell lines was inhibited and that in 4 cell lines was stimulated while that in the other 7 cell lines remained unaffected. Relation was observed between the number of EGF receptors per cell and the growth response to EGF. On the other hand, cell lines whose growth was inhibited by EGF in monolayer culture were stimulated by EGF in soft agar culture, though the opposite was not necessarily true.

上皮細胞増殖因子(EGF)の細胞増殖に対する効果と上皮細胞増殖因子受容体(EGFR)数の関連を食道癌細胞株16株について検討した. 125_I-EGF結合分析による EGFR 数は細胞あたり 6x10_4個から1. 2x10_7個であった. EGF により活性化されるチロシンキナーゼ活性はほぼ細胞あたりの EGFR 数に一致した. EGFR 遺伝子の増幅は1株に認めたのみであった. 単層培養において食道癌細胞株は EGF に対し3種類の増殖形態を示した. すなわち5株は増殖抑制, 4株は増殖促進, 7株は不変で, さらにこれら EGF に対する増殖反応と EGFR 数に関連が認められた. 一方, 単層培養で EGF により増殖が抑制される細胞株は軟寒天培養では増殖が促進されたが, 軟寒天培養で増殖が促進される細胞株は, 単層培養では抑制されるとはかぎらなかった.