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

肿瘤坏死因子（Tumor Necrosis Factor， TNF）在体外和体内均对某些肿瘤细胞发挥细胞毒和细胞抑制作用，而对正常细胞不产生影响。TNF被认为同时具有生长刺激和抑制信号。我们发现在TNF刺激下生长的人二倍体成纤维细胞FS-4细胞产生抑制细胞生长的前列腺素。通过对前列腺素的分析，FS-4细胞产生的主要前列腺素是PGE_2， tnf刺激了PGE_2的产生。此外，当添加花生四烯酸酯增强前列腺素的产生时，TNF作为细胞毒因子作用于FS-4细胞。为了阐明TNF信号转导的早期事件，采用TNF亲和层析纯化TNF受体。TNF受体是一个300 kDa的分子组装体，包括g蛋白。因此，tnf信号可能通过g蛋白刺激磷脂酶A_2，释放的花生四烯酸可能转化为前列腺素。接下来，使用TNF敏感的L929细胞和TNF耐药亚群检测前列腺素参与TNF的细胞毒性作用。L929细胞通过TNF治疗产生前列腺素，而TNF耐药亚群则没有。此外，加入吲哚美辛可抑制TNF对L929细胞的细胞毒作用，提示前列腺素可能参与TNF的细胞毒作用。这些结果提示前列腺素产生途径参与TNF的细胞毒性作用。

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.