A study of growth mechanism of leukemic blast progenitors in AML.

AML患者白血病原始细胞系祖细胞的生长受复杂的细胞因子网络控制。在急性髓系白血病产生的细胞因子中，肿瘤坏死因子-α具有最强的作用。我们研究了不同细胞因子对白血病原始细胞祖细胞生长、原癌基因表达、诱导细胞凋亡和细胞周期的影响。转化生长因子-β1的作用。转化生长因子β1对G-CSF支持的正常造血祖细胞的生长无影响，但对GM-CSF、IL-3或SCF支持的正常造血祖细胞有抑制作用，且抑制作用按顺序递增。无论使用何种生长因子，转化生长因子-β1都能显著抑制白血病原始细胞祖细胞的生长。通过c-Myc和c-Myb反义寡核苷酸实验和Northern印迹分析，c-Myc和c-Myb可能与抑制转化生长因子-β1直接相关。在正常造血祖细胞中，转化生长因子-β1优先抑制原始造血祖细胞。在血液…中恶性程度越高，转化生长因子β1的抑制程度越强，可能与内源性酪氨酸激酶活性的激活有关。结论：1.转化生长因子β1抑制急性髓系白血病细胞c-kit和Fas基因的表达，可能具有抗细胞凋亡和分化的作用。肿瘤坏死因子-α的作用。单独应用肿瘤坏死因子-α可促进急性髓系白血病原始细胞向S期转化，但不能促进白血病原始细胞的生长。在IL-3等细胞因子存在的情况下，肿瘤坏死因子-α对克隆形成细胞的生长有明显的刺激作用。肿瘤坏死因子-α刺激成纤维细胞表达c-kit、c-jun、Fas基因，并诱导细胞分化。转化生长因子-β1几乎完全阻断肿瘤坏死因子-α的促生长作用，诱导急性髓系白血病细胞凋亡。在不加生长因子的条件下体外培养急性髓系白血病细胞，观察到c-jun、c-fos基因的表达，向S期过渡，并诱导细胞凋亡。IL-3等抑制细胞凋亡，抑制c-jun基因转录，增强c-fos基因表达。部分AML患者细胞停留在G0/G1期，不表达c-jun和c-fos基因，未见细胞凋亡。C-jun/c-Fos的比例可能在诱导AML细胞凋亡中起重要作用。较少

The growth of leukemic blast progenitors from AML patients is under the control of complex network of cytokines. Among cytokines produced by AML blasts and stimulate the growth of their own progenitors, TNF-a possess most powerful effect. We investigated the effects of various cytokines on the growth of leukemic blast progenitors and expression of proto-oncogenes, induction of apoptosis, and cell cycle of blasts.1. Role of TGF-b1. TGF-b1 did not affect the growth of G-CSF supported normal hematopoietic progenitors, but suppressed the one supported by GM-CSF, IL-3, or SCF, and the suppression by TGF-b1 was increased in this order. TGF-b1 profoundly suppressed the growth of leukemic blast progenitors, irrespective of growth factor used. By experiments with c-Myc and c-Myb antisense oligonucleotides and Northern blot analysis, c-Myc and c-Myb may be directly related to TGF-b1 suppression. In normal hematopoietic progenitors, TGF-b1 preferentially suppressed the primitive ones. In hematolo … More gic malignancies, TGF-b1 suppression was increased with progression of clonal evolution, and may be related to the activation of endogenous tyrosine kinase activity. TGF-b1 inhibited the expression of c-kit and Fas mRNA by AML blasts, and seems to act against apoptosis and differentiation.2. Role of TNF-a. TNF-a alone enhanced the transition of AML blasts to S phase, but failed to stimulate the growth of leukemic blast progenitors. In the presence of cytokine such as IL-3, TNF-a powerfully stimulated the clonogenic cell growth. TNF-a stimulated the expression of c-kit, c-jun, and Fas mRNA by blasts, and induced differentiation of the cells. TGF-b1 almost completely abolished growth stimulating effect of TNF-a.Induction of apoptosis of AML blasts. When AMl blasts were cultured in vitro in the absence of growth factor, expression of c-jun and c-fos mRNA, transition into S phase, and induction of apoptosis of the cells were observed. Addition of factor such as IL-3 prevented apoptosis and suppressed c-jun transcript and enhanced c-fos transcript. In some AML cases, cells remained in G0/G1 phase, and did not express c-jun and c-fos mRNA, and apoptosis was not observed. The proportion of c-Jun/c-Fos may play an importent role in induction of apoptosis of AML blasts. Less