Sato T, Watanabe N, Yamauchi N, Sasaki H, Kobayashi D, Tsuji N, Okamoto T, Hagino T, Niitsu Y
Fourth Department of Internal Medicine, Sapporo Medical University, School of Medicine, Japan.
Int J Cancer. 1998 Oct 5;78(2):223-32. doi: 10.1002/(sici)1097-0215(19981005)78:2<223::aid-ijc17>3.0.co;2-b.
The present study examined differentiation-inducing activity by various tumor-necrosis-factor(TNF) mutants against the human leukemic cell lines HL-60 and U-937. Mutant TNF 471, from which 7 N-terminal amino acids of native TNF were deleted and Pro8, Ser9 and Asp10 were replaced by Arg, Lys and Arg, possessed the highest activity among the TNF mutants, and its activity was 120-fold that of native TNF. The various biological activities of TNF were signaled through 2 distinct receptors, p55 and p75. Although cytotoxicity was reported to involve mainly p55, this differentiation-inducing activity was not well understood. The fact that the affinity of TNF 471 was higher to p55 and lower to p75 than that of native TNF by a binding competition assay suggested that the differentiation-inducing activity was also signaled through p55. To verify this hypothesis, the human myelogenous leukemic cell line, KG-1, which scarcely expresses either receptor and does not differentiate with TNF, was transduced with the p55 or p75 gene. Subsequently p55 transfectants manifested a greater ability to differentiate; however, p75 transfectants did not differ from parental cells or from mock-transfectants. Further, the differentiation of p55 transfectants induced by TNF was reduced by the inhibitor of protein-kinase-C (PKC), staurosporine. These results indicate that the differentiation-inducing activity was signaled through the TNF receptor, p55, via PKC and that the excellent ability of TNF 471 to induce differentiation was related to its high affinity for p55.
本研究检测了各种肿瘤坏死因子（TNF）突变体对人白血病细胞系HL-60和U-937的分化诱导活性。突变体TNF 471缺失了天然TNF的7个N端氨基酸，并且Pro8、Ser9和Asp10分别被Arg、Lys和Arg取代，在TNF突变体中具有最高活性，其活性是天然TNF的120倍。TNF的各种生物学活性通过两种不同的受体p55和p75传递信号。虽然据报道细胞毒性主要涉及p55，但这种分化诱导活性还不太清楚。结合竞争试验表明，TNF 471对p55的亲和力高于天然TNF，而对p75的亲和力低于天然TNF，这表明分化诱导活性也是通过p55传递信号的。为了验证这一假设，将几乎不表达任何一种受体且不会被TNF诱导分化的人骨髓性白血病细胞系KG-1转导p55或p75基因。随后，p55转染细胞表现出更强的分化能力；然而，p75转染细胞与亲本细胞或空载体转染细胞没有差异。此外，蛋白激酶C（PKC）抑制剂星形孢菌素可降低TNF诱导的p55转染细胞的分化。这些结果表明，分化诱导活性是通过TNF受体p55经PKC传递信号的，并且TNF 471优异的诱导分化能力与其对p55的高亲和力有关。
