Department of Imaging research, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
NMR Biomed. 2011 Jul;24(6):582-91. doi: 10.1002/nbm.1644. Epub 2011 Mar 8.
Metastasis is a multistep process that culminates in the spread of cells from a primary tumor to a distant site or organs. For tumor cells to be able to metastasize, they have to locally invade through basement membrane into the lymphatic and the blood vasculatures. Eventually they extravasate from the blood and colonize in the secondary organ. This process involves multiple interactions between the tumor cells and their microenvironments. The microenvironment surrounding tumors has a significant impact on tumor development and progression. A key factor in the microenvironment is an acidic pH. The extracellular pH of solid tumors is more acidic in comparison to normal tissue as a consequence of high glycolysis and poor perfusion. It plays an important role in almost all steps of metastasis. The past decades have seen development of technologies to non-invasively measure intra- and/or extracellular pH. Most successful measurements are MR-based, and sensitivity and accuracy have dramatically improved. Quantitatively imaging the distribution of acidity helps us understand the role of the tumor microenvironment in cancer progression. The present review discusses different MR methods in measuring tumor pH along with emphasizing the importance of extracelluar tumor low pH on different steps of metastasis; more specifically focusing on epithelial-to-mesenchymal transition (EMT), and anti cancer immunity.
转移是一个多步骤的过程，最终导致细胞从原发肿瘤扩散到远处部位或器官。为了使肿瘤细胞能够转移，它们必须局部穿透基底膜进入淋巴管和血管系统。最终，它们从血液中逸出并在次级器官中定植。这个过程涉及肿瘤细胞与其微环境之间的多种相互作用。肿瘤周围的微环境对肿瘤的发展和进展有重大影响。微环境中的一个关键因素是酸性 pH 值。与正常组织相比，由于糖酵解水平高和灌注不良，实体瘤的细胞外 pH 值更酸性。它在转移的几乎所有步骤中都起着重要作用。在过去的几十年中，已经开发出了非侵入性测量细胞内和/或细胞外 pH 值的技术。最成功的测量方法是基于磁共振的，其灵敏度和准确性有了显著提高。定量成像酸度分布有助于我们了解肿瘤微环境在癌症进展中的作用。本综述讨论了测量肿瘤 pH 值的不同磁共振方法，并强调了细胞外肿瘤低 pH 值对转移不同步骤的重要性；更具体地说，重点关注上皮-间充质转化 (EMT) 和抗肿瘤免疫。
