Study of endothelial cell-specific signal transduction pathways and effect of chronic hypoxia. A strategy for the development of an effective antiangiogenic therapy.

血管生成受许多促血管生成因子的调控。因此，阻断通常作为几种促血管生成因子受体下蒸汽的信号分子，以调节内皮细胞的血管生成细胞反应，很可能必须有效地同时抑制几种促血管生成因子驱动的肿瘤血管生成。为了识别这些信号分子，我们研究了内皮细胞中的信号转导途径，发现；Fyn在fgf -2诱导的内皮细胞分化中起重要作用。Src是hgf和血管生成素1诱导的内皮细胞分化所必需的。Fes参与血管生成素1 （Ang1）诱导的内皮细胞增殖和fgf -2定向迁移。因此，Src家族激酶和Fes将成为抗血管生成治疗的潜在靶点。虽然抗血管生成策略在动物异种移植肿瘤模型中有效抑制肿瘤生长和进展，但在临床试验中，抗血管生成单一疗法未能减轻肿瘤的进展。这种差异的原因之一可能是人类肿瘤内皮细胞长期暴露于缺氧中。为了研究缺氧如何影响抗血管生成治疗的效果，我们在慢性缺氧条件下培养内皮细胞，并观察Src家族激酶抑制剂PP2对ang1诱导的毛细血管形态发生的影响。尽管小干扰RNA （small interfering RNA, siRNA）下调Src对常氧和缺氧条件下内皮细胞ang1诱导的毛细血管形态发生均有抑制作用，但PP2对缺氧条件下内皮细胞的抑制作用无效。这些细胞过度表达多药物相关蛋白1，通过siRNA下调其表达恢复PP2的作用。提示小分子蛋白激酶抑制剂与ABC转运蛋白抑制剂联用有利于提高分子靶向治疗的疗效。

Angiogenesis is regulated by a number of proangiogenic factors. It is therefore likely that blockade of signaling molecules that commonly act downsteam of several proangiogenic factor receptors for the regulation of angiogenic cellular responses by endothelial cells must efficiently inhibit tumor angiogenesis driven by several proangiogenic factors simultaneously. To identify such signaling molecules, we investigated the signal trandiuction pathways in endothelial cells and found that ;a. Fyn played an important roles for FGF-2-induced differentiation of endothelial cellsb. Src was required for HGF-and angiopoietin 1-induced differentiation of endothelial cellsc. Fes was involved in angiopoietin 1 (Ang1)-induced proliferation and FGF-2-directed migration by endothelial cells.Thus, Src family kinases and Fes would be potential targets for antiangiogenic therapy.While antiangiogenic strategy potently inhibits tumor growth and progression in xenografted tumor models in animals, antiangiogeic monotherapy failed to attenuate the progression of tumors in clinical trials. One of the reasons of this discrepancy may be that human tumor endothelial cells are chronically exposed to hypoxia. To examine how hypoxia affects the efficacy of antiangiogenic therapy, we cultured the endothelial cells under chronic hypoxia and the effect of a Src family kinase inhibitor PP2 on Ang1-induced capillary morphogenesis. Although downregulation of Src by small interfering RNA (siRNA) inhibited Ang1-induced capillary morphogenesis by endothelial cells cultured under both normoxic and hypoxic conditions, PP2 failed to inhibit it by hypoxic endothelial cells. These cells overexpressed multidrug associated protein 1, of which downregulation by siRNA restored the effect of PP2. This result suggests that combination of small molecular weight protein kinase inhibitors and ABC transporter inhibitos would be beneficial for increase in the efficacy of molecular targeting therapy.