Humblet C, Greimers R, Delvenne P, Deman J, Boniver J, Defresne M P
Laboratory of Pathological Anatomy and Cytopathology, University Hospital of Liège, Belgium.
J Natl Cancer Inst. 1996 Jun 19;88(12):824-31. doi: 10.1093/jnci/88.12.824.
Split-dose irradiation (1.75 Gy given weekly for 4 weeks) of C57BL/Ka mice induces the emergence of preleukemic cells (PLCs). These cells develop into leukemic cells after a latency period of 3-6 months. The survival and transformation of PLCs are dependent on radiation-induced alterations of the thymic epithelium and of resident lymphocyte (i.e., thymocyte) subpopulations in the thymus. PLCs can be eliminated, concomitantly with the restoration of the thymus, by grafting bone marrow cells immediately after the last irradiation. Our hypothesis was that any agent able to restore the thymus after leukemogenic irradiation would exert the same effects as a bone marrow graft. Tumor necrosis factor-alpha (TNF-alpha) is one such possible agent, since it has been shown to modulate some functions of the thymic epithelium and thymocyte subpopulations.
The goal of this study was to assess the ability of repeated intraperitoneal injections of TNF-alpha to functionally replace bone marrow transplantation in the restoration of normal intrathymic lymphopoiesis and in the prevention of thymic lymphomas in split-dose-irradiated mice.
We replaced the bone marrow graft with repeated injections of TNF-alpha (25 000 U/injection) in the split-dose-irradiated (4 x 1.75 Gy) C57BL/Ka mouse model. We analyzed the expression of the cell differentiation markers CD4 and CD8 on thymocytes by flow cytometry. We also studied the thymic environment by isolating thymic nurse cells, the bone marrow prothymocyte activity by analyzing thymic repopulation, and the evolution of PLCs by an in vivo transplantation assay. Local production of TNF-alpha after bone marrow grafting was examined by in situ hybridization. Injections of anti-TNF-alpha antibodies were given to split-dose-irradiated mice to test the effect of neutralizing TNF-alpha in vivo. One-way analysis of variance and Newman-Keuls two-tailed tests were used to test statistical significance.
Multiple injections of TNF-alpha into split-dose-irradiated mice did not influence bone marrow prothymocyte activity but restored thymocyte subpopulations and thymic epithelium, induced the disappearance of PLCs, and prevented the development of lymphomas. Moreover, a bone marrow graft significantly stimulated intrathymic production of TNF-alpha messenger RNA (P<.01), and anti-TNF-alpha antibodies partially inhibited the antilymphomatous effects of bone marrow graft in split-dose-irradiated mice (P<.05).
These data strongly suggest that TNF-alpha is a mediator that is involved in the mechanisms by which bone marrow transplantation functions to prevent thymic lymphomas in split-dose-irradiated mice.
Cytokines might be used in some biological systems, particularly in the hemopoietic system, as a therapeutic agent for the secondary prevention of cancer.
对C57BL/Ka小鼠进行分次照射（每周1.75 Gy，共4周）可诱导白血病前期细胞（PLCs）的出现。这些细胞在3 - 6个月的潜伏期后会发展为白血病细胞。PLCs的存活和转化依赖于辐射诱导的胸腺上皮和胸腺中驻留淋巴细胞（即胸腺细胞）亚群的改变。在最后一次照射后立即移植骨髓细胞，可在恢复胸腺的同时消除PLCs。我们的假设是，任何能够在致白血病照射后恢复胸腺的因子，其作用都与骨髓移植相同。肿瘤坏死因子-α（TNF-α）就是这样一种可能的因子,因为它已被证明可调节胸腺上皮和胸腺细胞亚群的某些功能。
本研究的目的是评估在分次照射的小鼠中，重复腹腔注射TNF-α在恢复正常胸腺内淋巴细胞生成以及预防胸腺淋巴瘤方面，能否在功能上替代骨髓移植。
在分次照射（4×1.75 Gy）的C57BL/Ka小鼠模型中，我们用重复注射TNF-α（25000 U/次）替代骨髓移植。通过流式细胞术分析胸腺细胞上细胞分化标志物CD4和CD8的表达。我们还通过分离胸腺哺育细胞来研究胸腺环境，通过分析胸腺再填充来研究骨髓前体细胞活性，并通过体内移植试验研究PLCs的演变。通过原位杂交检测骨髓移植后TNF-α的局部产生情况。给分次照射的小鼠注射抗TNF-α抗体，以测试在体内中和TNF-α的效果。采用单因素方差分析和Newman-Keuls双尾检验来检验统计学意义。
对分次照射的小鼠多次注射TNF-α，并不影响骨髓前体细胞活性，但能恢复胸腺细胞亚群和胸腺上皮，诱导PLCs消失，并预防淋巴瘤的发生。此外，骨髓移植显著刺激胸腺内TNF-α信使核糖核酸的产生（P<0.01），抗TNF-α抗体部分抑制了分次照射小鼠中骨髓移植的抗淋巴瘤作用（P<0.05）。
这些数据有力地表明，TNF-α是一种介质，参与了骨髓移植在分次照射小鼠中预防胸腺淋巴瘤的机制。
细胞因子可能在某些生物系统中，特别是在造血系统中，用作癌症二级预防的治疗剂。
