Differential effects of transforming growth factor-beta on proliferation of normal and malignant rat liver epithelial cells in culture.
Differential effects of transforming growth factor-beta on proliferation of normal and malignant rat liver epithelial cells in culture.
复制标题
转化生长因子-β对培养的正常和恶性大鼠肝上皮细胞增殖的不同影响。
作者：
McMahon Jb;Richards Wl;del Campo Aa;Min Song;S. Thorgeirsson
转化生长因子（tgf - β）已被证明对多种正常和肿瘤细胞的细胞生长具有刺激和抑制作用。tgf - β对不同类型细胞增殖的抑制作用的性质目前尚不清楚。我们利用新鲜分离的大鼠肝细胞、正常二倍体大鼠肝上皮细胞系（NRLM）和由其获得的经黄曲霉毒素B1体外转化的亚系（AFB），研究了tgf - β诱导的生长抑制的性质及其在化学诱导肿瘤转化后的改变。与黄曲霉毒素b1转化的细胞相比，tgf - β对正常大鼠肝上皮细胞（包括新分离的和NRLM细胞）的增殖有很大不同的影响。20 pg/ml的tgf - β对NRLM的集落形成有83%的抑制作用，而浓度高达10 ng/ml的tgf - β对AFB细胞的生长没有影响。在原代肝细胞和NRLM细胞中，浓度在10 pg至10 ng/ml之间时，tgf - β对DNA合成的抑制作用呈平行剂量依赖性。AFB细胞对DNA合成无抑制作用。此外，tgf - β既不诱导NRLM细胞的非锚定生长，也不影响AFB细胞在软琼脂中的生长。tgf - β诱导的NRLM细胞抑制在本质上是不可逆的，因为在培养基中去除tgf - β后，被处理的细胞无法增殖和形成菌落。此外，NRLM细胞在每毫升20 pg tgf - β存在4天后表现出细胞质肥大和大量脂质体衍生物形成的形态学变化，其中一些类似于脂褐素。tgf - β引起NRLM细胞高度不可逆抑制的发现强调了在解释抑制研究数据时需要谨慎，因为目前使用的大多数检测都是为评估体外生长刺激而设计的，并没有充分区分生长抑制剂可能的细胞毒性和/或细胞抑制作用。
Transforming growth factors (TGF-betas) have been shown to cause both stimulatory and inhibitory effects on cellular growth in a variety of normal and neoplastic cells. The nature of the inhibitory effects of TGF-beta on proliferation of different cell types is at present unclear. We have used freshly isolated rat hepatocytes, a normal diploid rat liver epithelial cell line (NRLM), and a subline (AFB) derived from it which was transformed in vitro by aflatoxin B1 to study the nature of TGF-beta-induced growth inhibition and its alteration following chemically induced neoplastic transformation. TGF-beta had a vastly different effect on proliferation of normal rat liver epithelial cells (both freshly isolated and NRLM cells) compared to aflatoxin B1-transformed cells. TGF-beta at 20 pg/ml caused 83% inhibition of colony formation of NRLM, whereas the growth of AFB cells was unaffected by TGF-beta at concentrations as high as 10 ng/ml. A parallel dose-dependent inhibition of DNA synthesis by TGF-beta was observed in both primary hepatocytes and NRLM cells at concentrations between 10 pg and 10 ng/ml. No inhibition of DNA synthesis was observed in AFB cells. Furthermore, TGF-beta did neither induce anchorage-independent growth of NRLM cells nor affect the growth of AFB cells in soft agar. TGF-beta-induced inhibition of the NRLM cells was irreversible in nature, since treated cells were unable to proliferate and form colonies upon removal of TGF-beta from the medium. Also, NRLM cells showed, after 4 days in the presence of 20 pg of TGF-beta per ml morphological changes characterized by cytoplasmic hypertrophy and the formation of abundant liposomal derivatives, some of which resemble lipofuscin. The finding that TGF-beta caused a high degree of irreversible inhibition of NRLM cells emphasizes the need for caution in interpreting data from inhibition studies, since most assays presently used are designed for assessing growth stimulation in vitro and do not adequately distinguish between the possible cytotoxic and/or cytostatic action of growth inhibitors.