Coexpression of the c-kit and stem cell factor genes in breast carcinomas.
Coexpression of the c-kit and stem cell factor genes in breast carcinomas.
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发表时间：
1995-06
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通讯作者：
Susan J. Hines;C. Organ;MJ Kornstein;G. Krystal
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作者：
Susan J. Hines;C. Organ;MJ Kornstein;G. Krystal
C-kit酪氨酸激酶生长因子受体在一些乳腺肿瘤中的表达已有报道，但关于其配体干细胞因子的表达尚无相关数据。本研究的目的是确定c-kit和干细胞因子基因在乳腺肿瘤和肿瘤衍生细胞系中共表达的频率，并确定c-kit和干细胞因子的共同表达是否能够刺激乳腺肿瘤细胞的生长。用核糖核酸酶保护法检测c-kit和干细胞因子基因在组织标本和细胞系中的表达，用免疫组织化学和Western blotting分别证实c-kit蛋白在肿瘤组织和细胞系中的表达。在研究的11个肿瘤标本中，9个表达了数量可变但可检测到的c-kit；13个肿瘤来源的细胞系中有7个也表达c-kit。所有的肿瘤标本和细胞系都表达可检测到的干细胞因子mRNA，这表明在大多数乳腺癌中可能存在自分泌生长环。为了确定c-kit和干细胞因子共表达的生物学效应，将c-kit表达载体导入只表达干细胞因子的MCF-7细胞系。C-kit和干细胞因子在MCF-7细胞中的共表达可提高细胞的生长速度和克隆效率，但不影响该细胞对雌激素的依赖性。对表达不同量c-kit蛋白的亚克隆的分析表明，尽管它们在含有IGF-1的无血清培养中都表现出比对照组更强的生长，但只有c-kit表达最高的亚克隆对外源可溶性干细胞因子有额外的生长反应。然而，当接触封闭的抗c-kit抗体时，所有表达c-kit的克隆，而不是对照克隆，都显示出生长抑制。该封闭抗体还可显著抑制已建立的ZR75-1细胞系在含有IGF-1的无血清培养液中的生长。综上所述，这些数据表明，干细胞因子和c-kit的共同表达可能是导致大量乳腺癌生长失控的原因。
Expression of the c-kit tyrosine kinase growth factor receptor has been reported in some breast tumors; however, no data exist concerning expression of its ligand, stem cell factor. The aim of this study was to determine how frequently the c-kit and stem cell factor genes were coexpressed in breast tumors and tumor-derived cell lines and to determine whether coexpression of c-kit and stem cell factor could result in growth stimulation of breast tumor cells. Expression of the c-kit and stem cell factor genes in tissue specimens and cell lines was determined using an RNase protection assay, with confirmation of c-kit protein expression by immunohistochemistry and Western blotting in tumor tissue and cell lines, respectively. Of 11 tumor specimens studied, 9 expressed variable but detectable quantities of c-kit; 7 of 13 tumor-derived cell lines also expressed c-kit. All tumor specimens and cell lines expressed detectable stem cell factor mRNA, suggesting that an autocrine growth loop could exist in the majority of breast carcinomas. To determine the biological effects of coexpression of c-kit and stem cell factor, the MCF-7 cell line, which expresses only stem cell factor, was transfected with a c-kit expression vector. Coexpression of c-kit and stem cell factor in MCF-7 cells resulted in an enhanced growth rate and cloning efficiency but not a loss of the dependence of this cell line upon estrogen. Analysis of subclones expressing different amounts of c-kit protein revealed that, although they all showed enhanced growth relative to control transfectants in serum-free medium containing IGF-1, only the highest c-kit expressor responded with additional growth to exogenous soluble stem cell factor. However, all c-kit-expressing clones, but not control clones, showed growth inhibition when exposed to a blocking anti-c-kit antibody. This blocking antibody also significantly inhibited the growth of the established ZR75-1 cell line in serum-free medium containing IGF-1. Taken together, these data suggest that coexpression of stem cell factor and c-kit could be responsible for growth deregulation in a significant number of breast carcinomas.