Overell R W, Weisser K E, Hess B, Namen A E, Grabstein K H
Department of Molecular Biology, Immunex Corporation, Seattle, Washington 98101.
Oncogene. 1989 Dec;4(12):1425-32.
The retroviral vector delta RM coexpresses the v-Ha-ras and v-mycMC29 oncogenes, under the transcriptional control of the retroviral long terminal repeat and an internal SV40 promoter respectively. In this report, the transforming activity of the delta RM virus on murine pre-B cells has been compared and contrasted with its activity on mature splenic B cells. Infection of primary bone marrow cells, followed by growth in the Whitlock-Witte culture system, resulted in the rapid outgrowth of transformed pre-B cells. These cells grew to high saturation densities and could give rise to immortal, interleukin-7-independent progeny that were able to grow independently of stromal elements. In contrast, infection of mature B cells purified from murine spleen resulted in only a transient increase in proliferation, and no immortal B cell lines were obtained. This inability of delta RM to transform mature B lymphocytes was not due to a low infection frequency, since parallel experiments with ecotropic retroviruses conferring drug resistance showed that the mature B cells were readily infectable. Moreover, Northern analysis showed that the delta RM-infected mature B cells expressed ras and myc mRNAs to higher levels than the delta RM transformed pre-B cells. Thus, coexpression of ras and myc resulted in the transformation of primary pre-B cells but not of the mature B cells. The potential explanations for the stage-specific transforming activity of the delta RM retrovirus are discussed.
逆转录病毒载体δRM分别在逆转录病毒长末端重复序列和内部SV40启动子的转录控制下，共表达v-Ha-ras和v-mycMC29癌基因。在本报告中，比较并对比了δRM病毒对小鼠前B细胞和成熟脾B细胞的转化活性。用原代骨髓细胞感染，然后在惠特洛克-维特培养系统中培养，导致转化的前B细胞迅速生长。这些细胞生长到高饱和密度，并能产生不依赖白细胞介素-7的永生后代，这些后代能够独立于基质成分生长。相比之下，用从小鼠脾脏纯化的成熟B细胞进行感染，仅导致增殖短暂增加，未获得永生B细胞系。δRM无法转化成熟B淋巴细胞并非由于感染频率低，因为用赋予耐药性的嗜亲性逆转录病毒进行的平行实验表明，成熟B细胞易于感染。此外，Northern分析表明，δRM感染的成熟B细胞中ras和myc mRNA的表达水平高于δRM转化的前B细胞。因此，ras和myc的共表达导致原代前B细胞而非成熟B细胞的转化。本文讨论了δRM逆转录病毒阶段特异性转化活性的潜在解释。
