Chen J K, Li L W, Mioh H
Cancer Res. 1987 Oct 1;47(19):4995-9.
The effects of retinoic acid on the epidermal growth factor (EGF) receptor binding and cell growth of normal and simian virus 40 (SV40)-transformed BALB/c 3T3 cells were compared under identical culture conditions. Retinoic acid induced a rapid enhancement of EGF binding to SV40-transformed cells. Half-maximal enhancement occurred at about 7 h after the cells were exposed to 20 ng/ml of retinoic acid, and maximal stimulation (from 2.5- to 3.5-fold over the control) was obtained after 12 h of exposure. The kd of the control and retinoic acid-treated cells was calculated to be 8.0 X 10(-10) M and 8.2 X -10 M, respectively. However, the number of unoccupied EGF binding sites increased from 0.98 X 10(4) to 2.28 X 10(4) per cell. Normal 3T3 cells would not respond to retinoic acid unless they were cultured in serum-containing medium. After 96 h of exposure, only a 50% enhancement of EGF binding was observed. The EGF receptor number of the untreated normal cells was calculated to be 1.82 X 10(4) per cell, twice the number expressed by untreated SV40-transformed cells. The increase of EGF receptor number caused by retinoic acid in SV40-transformed cells was blocked by either actinomycin D or cycloheximide treatment. These results indicated that SV40 transformation of BALB/c 3T3 cells altered the regulatory mechanism governing the complement of cell surface EGF receptors.
在相同培养条件下，比较了视黄酸对正常和猿猴病毒40（SV40）转化的BALB/c 3T3细胞的表皮生长因子（EGF）受体结合及细胞生长的影响。视黄酸可迅速增强EGF与SV40转化细胞的结合。细胞暴露于20 ng/ml视黄酸后约7小时出现半数最大增强，暴露12小时后获得最大刺激（比对照高2.5至3.5倍）。对照细胞和视黄酸处理细胞的解离常数（kd）经计算分别为8.0×10⁻¹⁰ M和8.2×10⁻¹⁰ M。然而，每个细胞未占据的EGF结合位点数量从0.98×10⁴增加到2.28×10⁴。正常3T3细胞除非在含血清培养基中培养，否则对视黄酸无反应。暴露96小时后，仅观察到EGF结合增强50%。未处理的正常细胞的EGF受体数量经计算为每个细胞1.82×10⁴，是未处理的SV40转化细胞所表达数量的两倍。视黄酸在SV40转化细胞中引起的EGF受体数量增加被放线菌素D或环己酰亚胺处理所阻断。这些结果表明，BALB/c 3T3细胞的SV40转化改变了控制细胞表面EGF受体补充的调节机制。
