Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305-5494, USA.
Br J Cancer. 2010 Feb 2;102(3):561-9. doi: 10.1038/sj.bjc.6605491. Epub 2010 Jan 5.
Tumours contain hypoxic regions that select for an aggressive cell phenotype; tumour hypoxia induces metastasis-associated genes. Treatment refractory patients with metastatic cancer show increased numbers of circulating tumour cells (CTCs), which are also associated with disease progression. The aim of this study was to examine the as yet unknown relationship between hypoxia and CTCs.
We generated human MDA-MB-231 orthotopic xenografts and, using a new technology, isolated viable human CTCs from murine blood. The CTCs and parental MDA-MB-231 cells were incubated at 21 and 0.2% (hypoxia) oxygen, respectively. Colony formation was assayed and levels of hypoxia- and anoxia-inducible factors were measured. Xenografts generated from CTCs and parental cells were compared.
MDA-MB-231 xenografts used to generate CTCs were hypoxic, expressing hypoxia factors: hypoxia-inducible factor1 alpha (HIF1alpha) and glucose transporter protein type 1 (GLUT1), and anoxia-induced factors: activating transcription factor 3 and 4 (ATF3 and ATF4). Parental MDA-MB-231 cells induced ATF3 in hypoxia, whereas CTCs expressed it constitutively. Asparagine synthetase (ASNS) expression was also higher in CTCs. Hypoxia induced ATF4 and the HIF1alpha target gene apelin in CTCs, but not in parental cells. Hypoxia induced lower levels of carbonic anhydrase IX (CAIX), GLUT1 and BCL2/adenovirus E1B 19-KD protein-interacting protein 3 (BNIP3) proteins in CTCs than in parental cells, supporting an altered hypoxia response. In chronic hypoxia, CTCs demonstrated greater colony formation than parental cells. Xenografts generated from CTCs were larger and heavier, and metastasised faster than MDA-MB-231 xenografts.
CTCs show an altered hypoxia response and an enhanced aggressive phenotype in vitro and in vivo.
肿瘤内含有选择侵袭性表型的缺氧区域；肿瘤缺氧诱导转移相关基因。患有转移性癌症且治疗抵抗的患者循环肿瘤细胞（CTC）数量增加，这些细胞也与疾病进展相关。本研究旨在探讨缺氧与 CTC 之间尚未明确的关系。
我们生成了人 MDA-MB-231 原位异种移植，并使用新技术从鼠血中分离出有活力的人 CTC。分别将 CTC 和 MDA-MB-231 亲本细胞在 21%和 0.2%（缺氧）氧气下孵育。检测集落形成，并测量缺氧和乏氧诱导因子的水平。比较来自 CTC 和亲本细胞的异种移植物。
用于生成 CTC 的 MDA-MB-231 异种移植瘤呈缺氧状态，表达缺氧因子：缺氧诱导因子 1 阿尔法（HIF1alpha）和葡萄糖转运蛋白 1 型（GLUT1），以及乏氧诱导因子：激活转录因子 3 和 4（ATF3 和 ATF4）。亲本 MDA-MB-231 细胞在缺氧时诱导 ATF3，而 CTC 则持续表达。天冬酰胺合成酶（ASNS）在 CTC 中的表达也更高。缺氧诱导 CTC 中 ATF4 和 HIF1alpha 靶基因 apelin，但不诱导亲本细胞表达。与亲本细胞相比，缺氧诱导 CTC 中碳酸酐酶 IX（CAIX）、GLUT1 和 BCL2/腺病毒 E1B 19-KD 蛋白相互作用蛋白 3（BNIP3）蛋白的表达水平更低，支持缺氧反应改变。在慢性缺氧时，CTC 的集落形成能力强于亲本细胞。来自 CTC 的异种移植物比 MDA-MB-231 异种移植物更大、更重，并且转移更快。
CTC 在体外和体内表现出改变的缺氧反应和增强的侵袭性表型。
