Larsson L G, Carlsson M, Schena M, Lantz M, Caligaris-Cappio F, Nilsson K
Department of Pathology, University of Uppsala, University Hospital, Sweden.
Leukemia. 1993 Feb;7(2):226-34.
Tumor necrosis factor-alpha (TNF-alpha) has recently been implicated as a regulator growth and differentiation of normal and malignant B cells. We utilized a selected clone (I-83) of primary resting B-type chronic lymphocytic leukemia (B-CLL) cells, inducible to activation, growth and differentiation in vitro, as a model system to study the possible role of TNF-alpha as an autocrine growth factor for such cells. Our results show that unstimulated I-83 B-CLL cells produced a low level of TNF-alpha mRNA, as shown by Northern blot analysis, and cytoplasmic TNF-alpha, determined in individual cells by immunocytochemistry. Secreted TNF-alpha could, however, not be detected in the medium by ELISA. TNF-alpha synthesis and secretion was, however, induced to high levels by stimulation of the B-CLL cells with interleukin-2 (IL-2) after activation by 12-O-tetradecanoylphorbol-13-acetate (TPA) or Staphylococcus aureus Cowan strain I (SAC) and B-cell stimulatory factor-MP6 (thioredoxin). A moderate increase in TNF-alpha secretion was also induced by TPA or IL-2 alone. IL-4 did not have any major effects on the production of TNF-alpha in activated cells, but inhibited the IL-2-induced production of TNF-alpha in SAC-activated cells. The cell surface expression of TNF-alpha receptors (TNF-R), as determined by binding assay using 125I-labelled recombinant TNF-alpha (rTNF-alpha), was also induced after SAC or TPA activation, but shed receptors (TNF-binding proteins) were only observed after TPA activation. Exogenously added rTNF-alpha in combination with TPA or SAC induced a high level of DNA synthesis in I-83 B-CLL cells. The increased endogenous production and secretion of TNF-alpha during induced growth stimulation, the induced expression of TNF-R, and the mitogenic effect of TNF-alpha on activated B-CLL cells raise the question whether TNF-alpha may function as an autocrine co-stimulator of B-CLL cell growth as recently suggested. anti-TNF-alpha and anti-TNF-R antibodies, however, failed to inhibit the IL-2- and IL-4-induced proliferation of activated I-83 B-CLL cells.
肿瘤坏死因子-α（TNF-α）最近被认为是正常和恶性B细胞生长及分化的调节因子。我们利用一个选定的原发性静止B型慢性淋巴细胞白血病（B-CLL）细胞克隆（I-83），该克隆在体外可被诱导激活、生长和分化，以此作为模型系统来研究TNF-α作为此类细胞自分泌生长因子的可能作用。我们的结果显示，如通过Northern印迹分析所示，未受刺激的I-83 B-CLL细胞产生低水平的TNF-α mRNA，并且通过免疫细胞化学在单个细胞中测定到细胞质TNF-α。然而，通过ELISA在培养基中未检测到分泌的TNF-α。不过，在用12-O-十四烷酰佛波醇-13-乙酸酯（TPA）或金黄色葡萄球菌Cowan I株（SAC）以及B细胞刺激因子-MP6（硫氧还蛋白）激活后，用白细胞介素-2（IL-2）刺激B-CLL细胞可诱导TNF-α的合成和分泌达到高水平。单独的TPA或IL-2也可诱导TNF-α分泌适度增加。IL-4对活化细胞中TNF-α的产生没有任何主要影响，但抑制SAC活化细胞中IL-2诱导的TNF-α产生。通过使用125I标记的重组TNF-α（rTNF-α）的结合试验测定，TNF-α受体（TNF-R）的细胞表面表达在SAC或TPA激活后也被诱导，但仅在TPA激活后观察到脱落的受体（TNF结合蛋白）。外源性添加的rTNF-α与TPA或SAC联合可诱导I-83 B-CLL细胞高水平的DNA合成。在诱导生长刺激期间TNF-α内源性产生和分泌的增加、TNF-R的诱导表达以及TNF-α对活化B-CLL细胞的促有丝分裂作用，引发了TNF-α是否可能如最近所提出的那样作为B-CLL细胞生长的自分泌共刺激因子的问题。然而，抗TNF-α和抗TNF-R抗体未能抑制IL-2和IL-4诱导的活化I-83 B-CLL细胞的增殖。
