CYTOKINE REGULATION OF NORMAL AND NEOPLASTIC HEMATOPOIETIC CELL GROWTH

这个项目的目标是更好地了解细胞外 正负信号及细胞内相互作用 造血干细胞的调节因子，因为它们与 恶性转化机制(S)及其对肿瘤发展的影响 治疗上有用的基因治疗方案。我们和其他人有 显示了启动和维持生长和分化的 原始祖细胞，多种细胞因子刺激(生长 要素协同作用)是必需的。最近，我们展示了这样的 细胞生长的负调控因子之间也存在协同作用， 原始祖细胞的增殖能力取决于 在细胞接收到的积极和消极信号的平衡上。 直接和可逆的转化生长因子-β 抑制具有骨髓再生能力的造血干细胞。 此外，短期孵育转化生长因子-β不会损害血管 这些干细胞的自我更新能力。转化生长因子-β具有抑制作用 多种细胞因子受体对细胞表面表达的影响 与其对细胞生长的影响直接相关。例如，词干 转化生长因子-β下调细胞因子受体(c-kit)的表达 这部分是通过影响c-kit基因的稳定性来实现的。此外，转化生长因子-β阻止S 通过细胞内机制的细胞周期时相进展 涉及转录因子调控和细胞周期调控 蛋白质。体内实验结果表明，转化生长因子-β对小鼠具有保护作用 从5-FU的致命性造血毒性以及 地塞米松的非造血毒性。这些发现表明，一个负面的 造血调节剂可成功地系统应用于 在体内介导化学保护。此外，积极的监管机构 用体内造血法测定其对小鼠心脏功能的影响 骨髓再生。重组人白介素7的给药 (rh IL-7)可使小鼠体内的细胞总数增加20倍 外周血白细胞(PBL)数。这些PBL包含 长期骨髓回填的干细胞数量增加 能力。利用我们调节血细胞生长的能力， 在此条件下对基因转移的可行性进行了研究。 我们发现单纯疱疹病毒胸苷的体外转移 先将自杀基因导入T细胞，然后再输注 造血干细胞可以在体内选择性耗尽 使用更昔洛韦的T细胞。因此，干细胞的细胞因子调节 细胞可能在治疗上有用。

The goal of this project is to better understand the extracellular signals and intracellular interactions between positive and negative regulators of hematopoietic stem cells as they pertain to the mechanism(s) of malignant transformation and to the development of therapeutically useful gene therapy protocols. We and others have shown that initiate and maintain the growth and differentiation of primitive progenitor cells, multiple cytokine stimulation (growth factor synergy) is required. Recently, we showed that such cooperativity also occurs between negative regulators of cell growth, and that the ability of primitive progenitors to proliferate depends on the balance of positive and negative signals the cell receives. Transforming growth factor-beta (TGF-beta) directly and reversibly inhibits hematopoietic stem cells with marrow repopulating ability. Also, short-term incubation with TGF-beta does not damage the self-renewal potential of these stem cells. TGF-beta has inhibitory effects on the cell surface expression of many cytokine receptors that directly correlates with its effect on cell growth. For example, stem cell factor receptor (c-kit) expression is down-regulated by TGF-beta in part by affecting c-kit mRNA stability. Also, TGF-beta prevents S phase cell cycle progression through an intracellular mechanism involving regulation of transcription factors and cell cycle regulatory proteins. In vivo results demonstrated that TGF-beta can protect mice from both the lethal hematopoietic toxicity of 5-FU, as well as the non-hematopoiesis toxicity of DXR. These findings show that a negative regulator of hematopoiesis can be successfully used systemically to mediate chemoprotection in vivo. Also, positive regulators of hematopoiesis were used in vivo to determine their effect on myelopoiesis. Administration of recombinant human interleukin-7 (rhIL-7) to mice resulted in up to a 20-fold increase in the total number of peripheral white blood cells (PBL). These PBL contained increased number of stem cells with lomg-term marrow repoulating ability.Using our ability to regulate the growth of hematologic cells, the feasibility of gene transfer was studied under these conditions. We showed that the ex-vivo transfer of the herpes simplex thymidine kinase suicide gene into T cells before their infusion with hematopoietic stem cells could allow for selective in vivo depletion of these T cells with ganciclovir. Thus, cytokine regulation of stem cells might be therapeutically useful.