Neuner P, Klosner G, Pourmojib M, Trautinger F, Knobler R
Department of Special and Environmental Dermatology, University of Vienna, Austria.
Cancer Res. 1994 Nov 15;54(22):6001-5.
Most tumor cells produce both tumor necrosis factor (TNF) receptors, the M(r) 55,000 TNFRI and the M(r) 75,000 TNFRII, but they are mostly resistant to TNF-alpha-induced cytotoxicity. To gain further insight into the escape mechanisms of tumor cells from the harmful effect of TNF-alpha, we investigated the production of TNF-binding proteins (TNF-BPI, TNF-BPII, both M(r) 30,000) by malignant and normal epidermal cells and studied their functional role in TNF-alpha-induced cytotoxicity. Malignant human keratinocytes (A431, KB, HaCaT) and malignant human melanoma cells (KRFM) produced significant levels of both TNF-BPI and TNF-BPII on stimulation with phorbol myristate acetate. In contrast, normal human keratinocytes (HNK) and normal human melanocytes (HNM) released TNF-BPI but not TNF-BPII. The specific production of TNF-BPII in concert with TNF-BPI by the malignant cell lines revealed an inhibitory effect of supernatants on recombinant human TNF-alpha-mediated cytotoxicity of the TNF-dependent murine cell line L929, while supernatants of normal epidermal cells had no effect. Preincubation of supernatants with anti-TNF-BPI monoclonal antibody htr-9 or anti-TNF-BPII monoclonal antibody utr-1 reversed this inhibitory effect additively, indicating that the production of both TNF-BPs is necessary to protect cells from TNF-alpha-mediated cytotoxicity. A TNF-alpha scavanging effect of TNF-BPs resulting in subsequent inhibition of TNF-alpha binding to L929 cells could be demonstrated by ligand blotting and fluorescence-activated cell sorting analysis. Thus the production of TNF-BPII by epidermal tumor cells in concert with TNF-BPI appears to demonstrate a specific mechanism by which malignant epithelial cells escape from TNF-alpha-mediated cytotoxicity.
大多数肿瘤细胞都能产生两种肿瘤坏死因子（TNF）受体，即分子量为55,000的TNFR I和分子量为75,000的TNFR II，但它们大多对TNF-α诱导的细胞毒性具有抗性。为了进一步深入了解肿瘤细胞逃避TNF-α有害作用的机制，我们研究了恶性和正常表皮细胞产生的TNF结合蛋白（TNF-BP I、TNF-BP II，分子量均为30,000），并研究了它们在TNF-α诱导的细胞毒性中的功能作用。恶性人角质形成细胞（A431、KB、HaCaT）和恶性人黑色素瘤细胞（KRFM）在用佛波酯肉豆蔻酸酯刺激后，会产生大量的TNF-BP I和TNF-BP II。相比之下，正常人角质形成细胞（HNK）和正常人黑色素细胞（HNM）释放TNF-BP I，但不释放TNF-BP II。恶性细胞系协同TNF-BP I特异性产生TNF-BP II，这表明其培养上清液对TNF依赖性小鼠细胞系L929的重组人TNF-α介导的细胞毒性具有抑制作用，而正常表皮细胞的培养上清液则无此作用。将培养上清液与抗TNF-BP I单克隆抗体htr-9或抗TNF-BP II单克隆抗体utr-1预孵育，可相加性地逆转这种抑制作用，表明两种TNF-BP的产生对于保护细胞免受TNF-α介导的细胞毒性是必需的。通过配体印迹和荧光激活细胞分选分析可以证明，TNF-BP具有TNF-α清除作用，从而导致随后TNF-α与L929细胞的结合受到抑制。因此，表皮肿瘤细胞协同TNF-BP I产生TNF-BP II似乎证明了一种恶性上皮细胞逃避TNF-α介导的细胞毒性的特定机制。
