Dimitroulakos J, Ye L Y, Benzaquen M, Moore M J, Kamel-Reid S, Freedman M H, Yeger H, Penn L Z
Division of Cellular and Molecular Biology Ontario Cancer Institute, University Health Network, Toronto, Canada.
Clin Cancer Res. 2001 Jan;7(1):158-67.
3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase is the rate-limiting enzyme of the mevalonate pathway, the diverse array of end products of which are vital for a variety of cellular functions, including cholesterol synthesis and cell cycle progression. We showed previously that this enzyme holds a critical role in regulating tumor cell fate, including cell death, as its expression is down-regulated in response to retinoic acid, a potent anticancer therapeutic. Indeed, direct inhibition of HMG-CoA reductase with lovastatin, a competitive inhibitor of this enzyme, induced a pronounced apoptotic response in neuroblastoma and acute myeloid leukemic cells. We have now extended this work and evaluated a wide variety and large number of tumor-derived cell lines for their sensitivity to lovastatin-induced apoptosis. These cell lines were exposed to a wide range (0-100 microM) of lovastatin for 2 days and assayed for cell viability using the 3,4,5-dimethyl thiazlyl-2,2,5-diphenyltetrazolium bromide assay and the induction of apoptosis by flow cytometric and ultrastructural analyses. Lovastatin induced a pronounced apoptotic response in cells derived from juvenile monomyelocytic leukemia, pediatric solid malignancies (rhabdomyosarcoma and medulloblastoma), and squamous cell carcinoma of the cervix and of the head and neck. Interestingly, the subset of malignancies that are particularly sensitive to lovastatin-induced apoptosis correspond to those tumor subtypes that are sensitive to the biological and antiproliferative effects of retinoids in vitro. The nature of the biologically active form of lovastatin has been challenged recently as the growth-inhibitory effects of this drug were attributed to its prodrug lactone form that does not inhibit HMG-CoA reductase function. In this report, we demonstrate that the apoptotic properties of lovastatin are triggered by the open ring acid form that is a potent inhibitor of HMG-CoA reductase activity. Thus, we have identified a subset of tumors that are sensitive to lovastatin-induced apoptosis and show HMG-CoA reductase as a potential therapeutic target of these cancers.
3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶是甲羟戊酸途径的限速酶，该途径的各种终产物对多种细胞功能至关重要，包括胆固醇合成和细胞周期进程。我们之前表明，这种酶在调节肿瘤细胞命运（包括细胞死亡）中起关键作用，因为其表达会因视黄酸（一种有效的抗癌治疗药物）而下调。事实上，用洛伐他汀（该酶的竞争性抑制剂）直接抑制HMG-CoA还原酶，可在神经母细胞瘤和急性髓系白血病细胞中诱导明显的凋亡反应。我们现在扩展了这项工作，并评估了大量不同的肿瘤来源细胞系对洛伐他汀诱导凋亡的敏感性。这些细胞系暴露于广泛范围（0 - 100微摩尔）的洛伐他汀中2天，并使用3,4,5-二甲基噻唑-2,2,5-二苯基四氮唑溴盐法检测细胞活力，并通过流式细胞术和超微结构分析检测凋亡诱导情况。洛伐他汀在源自青少年单核细胞白血病、儿童实体恶性肿瘤（横纹肌肉瘤和髓母细胞瘤）以及宫颈和头颈部鳞状细胞癌的细胞中诱导了明显的凋亡反应。有趣的是，对洛伐他汀诱导凋亡特别敏感的恶性肿瘤子集与那些在体外对视黄酸的生物学和抗增殖作用敏感的肿瘤亚型相对应。最近，洛伐他汀生物活性形式的性质受到了质疑，因为这种药物的生长抑制作用被归因于其前药内酯形式，而该形式并不抑制HMG-CoA还原酶功能。在本报告中，我们证明洛伐他汀的凋亡特性是由开环酸形式触发的，该形式是HMG-CoA还原酶活性的有效抑制剂。因此，我们确定了一组对洛伐他汀诱导凋亡敏感的肿瘤，并表明HMG-CoA还原酶是这些癌症的潜在治疗靶点。
