Study of the Signal Transduction of and Cellular Response (Growth Stimulation and Cytotoxicity) to Tumor Necrosis Factor

肿瘤坏死因子（TNF）在体外和体内对某些肿瘤细胞发挥细胞毒性和细胞生长抑制作用，而不影响正常细胞。TNF被认为具有生长刺激和抑制信号。我们发现，人二倍体成纤维细胞FS-4细胞，其生长被TNF刺激，产生前列腺素，抑制细胞生长。通过对前列腺素的分析，发现FS-4细胞产生的前列腺素主要是PGE_2，且这种前列腺素的产生可被TNF刺激。此外，当通过添加花生四烯酸来增强前列腺素的产生时，TNF充当针对FS-4细胞的细胞毒性因子。为了阐明TNF-信号转导的早期事件，通过TNF-亲和层析纯化TNF受体。TNF受体是一个分子量为300 kDa的分子集合体，包括G蛋白。因此，TNF信号可能通过G蛋白刺激磷脂酶A_2，使花生四烯酸转化为花生四烯酸。接下来，使用TNF敏感的L929细胞和TNF抗性的亚系检查了在TNF的细胞毒性作用中的洋地黄素的参与。L929细胞产生前列腺素的TNF治疗，而TNF耐药的亚系没有。此外，TNF对L929细胞的细胞毒作用被消炎痛抑制，提示前列腺素可能参与TNF的细胞毒作用。这些结果表明，在TNF的细胞毒作用中，涉及到胰高血糖素产生途径。

Tumor Necrosis Factor (TNF) exerts cytotoxic and cytostatic action against certain tumor cells while sparing normal cells both in vitro and in vivo. TNF is thought to have both growth stimulatory and inhibitory signals. We discovered that human diploid fibroblast FS-4 cells, which growth was stimulated by TNF, generated prostaglandin that suppressed cell growth. By the analysis of prostaglandins, PGE_2 was the main prostaglandin produced in FS-4 cells and the production of this prostaglandin was stimulated by TNF-treatment. Furthermore, when prostaglandin production was enhanced by the addition of arachidonate, TNF acts as cytotoxic factor against FS-4 cells. For elucidating the early event of TNF-signal transduction, TNF receptor was purified by TNF-affinity chromatograpy was examined. TNF receptor was a molecular assembly of 300 kDa, including G-protein. Therefore, TNF-signal might stimulate phospholipase A_2 via G-protein, then released arachidonate might convert to prostaglandins. Next, the involvement of prostaglandins in the cytotoxic action of TNF was examined using TNF-sensitive L929 cells and TNF-resistant sublines. L929 cells generated prostaglandin by the treatment of TNF, whereas TNF-resistant sublines did not. Furthermore the cytotoxic action of TNF on L929 cells was inhibited by the addition of indomethacin, suggesting that prostaglandin may be involved in the cytotoxic action of TNF. These results indicate the involvement of prostaglandinproducing pathway in the cytotoxic action of TNF.