Lippman M E, Dickson R B, Kasid A, Gelmann E, Davidson N, McManaway M, Huff K, Bronzert D, Bates S, Swain S
J Steroid Biochem. 1986 Jan;24(1):147-54. doi: 10.1016/0022-4731(86)90044-0.
Previous work from our laboratory has demonstrated that human breast cancer (BC) cells in culture can be stimulated by physiologic concentrations of estrogen. In an effort to further understand this process, we have examined the biochemical and biological properties of proteins secreted by human BC cells in vitro. We have developed a defined medium system which simultaneously allows the collection of factors secreted by the BC cells, facilitates their purification and allows for an unequivocal assay of their effect on other BC cells. By both biochemical and radioimmunoassay procedures, MCF-7 cells secrete large quantities of IGF-I-like activity. The cells contain receptors for IGF-I and are stimulated by physiologic concentrations of IGF-I. Multiple additional peaks of growth stimulatory activity can be obtained by partial purification of conditioned media from human BC cells by sequential dialysis, acid extraction and Biogel P60 chromatography. These peaks are induced up to 200-fold by physiologic concentrations of estrogen. Several of these peaks cross-react in a radioreceptor assay with EGF and are thus candidates for transforming growth factors. Monoclonal antibodies (MCA) have been prepared which react with secreted proteins from the MCF-7 cells. One of these MCAs binds to material from MCF-7 and ZR-75-1 hormone-dependent BC cells only when these two lines are treated with estrogen but reacts with conditioned medium from several other hormone-independent cell lines in the absence of estrogen stimulation. This MCA is currently undergoing further characterization and evaluation of its biological potency. We conclude that with estrogen stimulation, hormone-dependent human BC cells secrete peptides which when partially purified can replace estrogen as a mitogen. Their role as autocrine or paracrine growth factors and their effects on surrounding nonneoplastic stroma may suggest a means of interfering with tumor proliferation.
我们实验室之前的研究表明，培养中的人乳腺癌（BC）细胞可受到生理浓度雌激素的刺激。为了进一步了解这一过程，我们研究了人BC细胞体外分泌蛋白的生化和生物学特性。我们开发了一种特定的培养基系统，该系统能同时收集BC细胞分泌的因子，便于其纯化，并能明确测定它们对其他BC细胞的作用。通过生化和放射免疫分析程序，MCF-7细胞分泌大量类胰岛素样生长因子-I（IGF-I）活性。这些细胞含有IGF-I受体，并受到生理浓度IGF-I的刺激。通过对人BC细胞条件培养基进行连续透析、酸提取和Biogel P60层析进行部分纯化，可获得多个额外的生长刺激活性峰。这些峰在生理浓度雌激素作用下可诱导增加至200倍。其中几个峰在放射受体分析中与表皮生长因子（EGF）发生交叉反应，因此是转化生长因子的候选物。已制备出与MCF-7细胞分泌蛋白反应的单克隆抗体（MCA）。其中一种MCA仅在这两种细胞系用雌激素处理时才与MCF-7和ZR-75-1激素依赖性BC细胞的物质结合，但在无雌激素刺激的情况下与其他几种激素非依赖性细胞系的条件培养基发生反应。这种MCA目前正在进行进一步的特性鉴定及其生物学效能评估。我们得出结论，在雌激素刺激下，激素依赖性人BC细胞分泌的肽经部分纯化后可替代雌激素作为有丝分裂原。它们作为自分泌或旁分泌生长因子的作用及其对周围非肿瘤性基质的影响可能提示了一种干扰肿瘤增殖的方法。
