Yuspa S H, Vass W, Scolnick E
Cancer Res. 1983 Dec;43(12 Pt 1):6021-30.
Mouse epidermal basal cells can be cultured in medium with a Ca2+ concentration below 0.1 mM and induced to terminally differentiate in medium with higher Ca2+. Infection of basal cells with Kirsten or Harvey sarcoma virus causes a marked stimulation of basal cell proliferation. Challenge of infected basal cell cultures with 0.5 mM Ca2+ medium indicates that terminal differentiation is altered, since infected cultures persist in this medium for long periods without stratifying and sloughing from the culture dish. Infected cultures express much higher levels of protein with a molecular weight of 21,000 than controls, and studies with temperature-sensitive mutants indicate that persistent function of protein with a molecular weight of 21,000 is required for the observed effects of the sarcoma viruses on terminal differentiation. In response to 0.5 mM Ca2+, the proliferation rate is markedly reduced in both control and virally infected cells. However, the proliferation rate of the sarcoma virus-infected cultures is reduced less in response to elevated levels of calcium. Virus-infected cells as well as controls also demonstrate a rise in the differentiation-associated enzymatic activity of epidermal transglutaminase and will terminally differentiate when the multiplicity of infection is below one. These results suggest that sarcoma virus-infected cells are not blocked completely in their program of terminal differentiation in response to 0.5 mM Ca2+ and differ in this respect from epidermal cells altered by exposure to chemical carcinogens and from malignant keratinocytes. Infection with Kirsten or Harvey sarcoma virus and expression of protein with a molecular weight of 21,000 therefore are closely linked to epidermal proliferation and retard, but do not completely block, the program of terminal differentiation. The effects of ras oncogenes on NIH 3T3 cells are discussed relative to the effects of ras oncogenes observed on the primary mouse epidermal cells in the context of multistep models for naturally occurring epithelial cancers.
小鼠表皮基底细胞可在钙离子浓度低于0.1 mM的培养基中培养，并在钙离子浓度较高的培养基中诱导终末分化。用柯斯顿或哈维肉瘤病毒感染基底细胞会显著刺激基底细胞增殖。用0.5 mM钙离子培养基对感染的基底细胞培养物进行刺激，结果表明终末分化发生了改变，因为感染的培养物在这种培养基中能长时间持续存在，而不会从培养皿中分层和脱落。与对照相比，感染的培养物表达的分子量为21,000的蛋白质水平要高得多，对温度敏感突变体的研究表明，肉瘤病毒对终末分化的观察到的影响需要分子量为21,000的蛋白质持续发挥作用。在0.5 mM钙离子作用下，对照细胞和病毒感染细胞的增殖率均显著降低。然而，肉瘤病毒感染的培养物对钙离子水平升高的反应中，增殖率降低得较少。病毒感染细胞以及对照细胞还表现出表皮转谷氨酰胺酶的分化相关酶活性升高，并且当感染复数低于1时会终末分化。这些结果表明，肉瘤病毒感染的细胞在0.5 mM钙离子作用下其终末分化程序并未被完全阻断，在这方面与接触化学致癌物而改变的表皮细胞以及恶性角质形成细胞不同。因此，用柯斯顿或哈维肉瘤病毒感染以及分子量为21,000的蛋白质的表达与表皮增殖密切相关，并延缓但并未完全阻断终末分化程序。在自然发生的上皮癌的多步骤模型背景下，讨论了ras癌基因对NIH 3T3细胞的影响相对于在原代小鼠表皮细胞上观察到的ras癌基因的影响。
