David Justin M, Owens Tori A, Inge Landon J, Bremner Ross M, Rajasekaran Ayyappan K
Authors' Affiliations: Department of Biological Sciences, University of Delaware, Newark; Nemours Center for Childhood Cancer Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware; and Center for Thoracic Disease and Transplantation, Heart and Lung Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.
Mol Cancer Ther. 2014 Apr;13(4):788-99. doi: 10.1158/1535-7163.MCT-13-0891. Epub 2014 Feb 3.
Ionophores are hydrophobic organic molecules that disrupt cellular transmembrane potential by permeabilizing membranes to specific ions. Gramicidin A is a channel-forming ionophore that forms a hydrophilic membrane pore that permits the rapid passage of monovalent cations. Previously, we found that gramicidin A induces cellular energy stress and cell death in renal cell carcinoma (RCC) cell lines. RCC is a therapy-resistant cancer that is characterized by constitutive activation of the transcription factor hypoxia-inducible factor (HIF). Here, we demonstrate that gramicidin A inhibits HIF in RCC cells. We found that gramicidin A destabilized HIF-1α and HIF-2α proteins in both normoxic and hypoxic conditions, which in turn diminished HIF transcriptional activity and the expression of various hypoxia-response genes. Mechanistic examination revealed that gramicidin A accelerates O(2)-dependent downregulation of HIF by upregulating the expression of the von Hippel-Lindau (VHL) tumor suppressor protein, which targets hydroxylated HIF for proteasomal degradation. Furthermore, gramicidin A reduced the growth of human RCC xenograft tumors without causing significant toxicity in mice. Gramicidin A-treated tumors also displayed physiologic and molecular features consistent with the inhibition of HIF-dependent angiogenesis. Taken together, these results demonstrate a new role for gramicidin A as a potent inhibitor of HIF that reduces tumor growth and angiogenesis in VHL-expressing RCC.
离子载体是疏水性有机分子，可通过使膜对特定离子具有通透性来破坏细胞跨膜电位。短杆菌肽A是一种形成通道的离子载体，它形成一个亲水性膜孔，允许单价阳离子快速通过。此前，我们发现短杆菌肽A在肾细胞癌（RCC）细胞系中诱导细胞能量应激和细胞死亡。RCC是一种对治疗耐药的癌症，其特征是转录因子缺氧诱导因子（HIF）的组成性激活。在此，我们证明短杆菌肽A在RCC细胞中抑制HIF。我们发现，在常氧和缺氧条件下，短杆菌肽A都会使HIF-1α和HIF-2α蛋白不稳定，进而降低HIF转录活性以及各种缺氧反应基因的表达。机制研究表明，短杆菌肽A通过上调靶向羟基化HIF进行蛋白酶体降解的von Hippel-Lindau（VHL）肿瘤抑制蛋白的表达，加速HIF的氧依赖性下调。此外，短杆菌肽A可减少人RCC异种移植瘤的生长，且对小鼠无明显毒性。经短杆菌肽A处理的肿瘤还表现出与抑制HIF依赖性血管生成一致的生理和分子特征。综上所述，这些结果证明了短杆菌肽A作为一种有效的HIF抑制剂的新作用，它可减少表达VHL的RCC中的肿瘤生长和血管生成。
