Thorpe P E, Derbyshire E J, Andrade S P, Press N, Knowles P P, King S, Watson G J, Yang Y C, Rao-Betté M
Department of Pharmacology, University of Texas Southwestern Medical School, Dallas 75235-8576.
Cancer Res. 1993 Jul 1;53(13):3000-7.
Inhibitors of angiogenesis hold potential in the treatment of cancer and other diseases where the disease is caused or maintained by the inappropriate growth of blood vessels. In the present study, a novel inhibitor of angiogenesis was synthesized by covalently linking a nonanticoagulating derivative of heparin, heparin adipic hydrazide (HAH), by an acid-labile bond to the antiangiogenic steroid, cortisol. The rationale was that the heparin derivative, which binds to sulfated polyanion receptors on endothelial cells, should concentrate the steroid on the surface of vascular endothelial cells. Endocytosis of the conjugate and decomposition of the acid-labile linkage inside lysosomes and other acidic intracellular compartments should then lead to release of the cortisol and expression of its antiproliferative activity. Analysis of the stability of HAH-cortisol showed that it was stable at pH 7.4 and broke down rapidly (t1/2 15 min) at pH 4.8 at 37 degrees C. Treatment of murine pulmonary capillary endothelial cells with HAH-cortisol at 10(-5) M (with respect to cortisol) suppressed their DNA synthesis by 50% and inhibited their migration into wounded areas of confluent monolayers. HAH-cortisol at 10(-4) M (with respect to cortisol) did not suppress the DNA synthesis of Lewis lung carcinoma cells. Daily i.p. injections of HAH-cortisol into mice bearing s.c. sponge implants retarded vascularization of the sponge, and injections directly into the sponge abolished vascularization for as long as the injections were continued. Daily i.v. injections of HAH-cortisol at doses causing no apparent toxicity retarded the growth of solid s.c. Lewis lung carcinomas in mice by up to 65%. In all of these assays, equivalent treatments with a mixture of the HAH plus cortisol was significantly less effective. The antiproliferative effect of HAH-cortisol on endothelial cells appeared independent of the glucocorticoid activity of the steroid since HAH conjugated to 5 beta-pregnane-3 alpha,17 alpha,21-triol-20-one, a steroid lacking glucocorticoid or mineralocorticoid activity, was even more effective at inhibiting DNA synthesis by murine pulmonary capillary endothelial cells than was HAH-cortisol. In conclusion, HAH-cortisol represents the prototype of a new class of angiogenesis inhibitors for the treatment of cancer and other angiogenic diseases.
血管生成抑制剂在治疗癌症及其他由血管异常生长引发或维持的疾病方面具有潜力。在本研究中，通过酸不稳定键将肝素的非抗凝血衍生物己二酸酰肼肝素（HAH）与抗血管生成甾体皮质醇共价连接，合成了一种新型血管生成抑制剂。其原理是，与内皮细胞上硫酸化多阴离子受体结合的肝素衍生物应能使甾体在血管内皮细胞表面富集。缀合物的内吞作用以及溶酶体和其他酸性细胞内区室中酸不稳定键的分解随后应导致皮质醇释放并发挥其抗增殖活性。对HAH - 皮质醇稳定性的分析表明，它在pH 7.4时稳定，在37℃、pH 4.8时迅速分解（半衰期15分钟）。用10⁻⁵ M（相对于皮质醇）的HAH - 皮质醇处理小鼠肺毛细血管内皮细胞，可使其DNA合成抑制50%，并抑制其迁移至汇合单层的损伤区域。10⁻⁴ M（相对于皮质醇）的HAH - 皮质醇并未抑制Lewis肺癌细胞的DNA合成。每日腹腔注射HAH - 皮质醇给皮下植入海绵的小鼠，可延缓海绵的血管化，而直接注射到海绵中，只要持续注射就能消除血管化。每日静脉注射无明显毒性剂量的HAH - 皮质醇可使小鼠皮下实体Lewis肺癌的生长延缓高达65%。在所有这些实验中，用HAH加皮质醇的混合物进行等效处理效果明显较差。HAH - 皮质醇对内皮细胞的抗增殖作用似乎与甾体的糖皮质激素活性无关，因为与5β - 孕烷 - 3α,17α,21 - 三醇 - 20 - 酮（一种缺乏糖皮质激素或盐皮质激素活性的甾体）缀合的HAH在抑制小鼠肺毛细血管内皮细胞DNA合成方面比HAH - 皮质醇更有效。总之，HAH - 皮质醇代表了一类用于治疗癌症和其他血管生成性疾病的新型血管生成抑制剂的原型。
