Currie M J, Gunningham S P, Han C, Scott P A, Robinson B A, Harris A L, Fox S B
Anatomical Pathology, Canterbury Health, Christchurch Hospital, Christchurch, New Zealand.
Clin Cancer Res. 2001 Apr;7(4):918-27.
Angiogenesis is essential for tumor growth and metastasis. It is a complex, dynamic process that is coordinated by several classes of angiogenic factors. One candidate family is the Tie2 tyrosine kinase, whose expression is restricted largely to endothelial cells. Tie2 has three known ligands, angiopoietin (Ang)-1, Ang-2, and Ang-4, that have different functional effects but play a requisite role in embryonic vessel remodeling. Because there are only limited data on the Tie2 pathway in human breast cancer, and our previous data have suggested that breast tumors establish a blood supply by vascular remodeling, we have investigated the expression of Ang-1, Ang-2, Ang-4, and Tie2 in a series of normal and neoplastic human breast tissues.
We examined mRNA expression by reverse transcription-PCR in 6 normal and 52 malignant breast tissues and correlated expression with clinicopathological and angiogenic variables. We also examined the effect of physiological levels of estrogen on Ang expression.
Ang-1, Ang-2, Ang-4, and Tie2 were detected in 19%, 52%, 35%, and 65%, respectively, of tumor samples. There was a significant reduction in expression of tumor Ang-1 (P = 0.04), Ang-2 (P = 0.01), Ang-4 (P = 0.004), and Tie2 (P = 0.02) compared with that in normal breast tissues. There was a significant relationship in tumors between all Angs and between each ligand and Tie2. In a multivariate analysis, there were significant positive correlations between Ang-4 and estrogen receptor (P = 0.016) and a significant inverse correlation between Ang-1 and thymidine phosphorylase expression (P = 0.01). No significant associations were observed between the other members of the Ang/Tie2 gene family and patient age, tumor size, lymph node status, tumor grade, vascular invasion, tumor vascularity, vascular maturation, thymidine phosphorylase, or vascular endothelial growth factor A expression (P > 0.05 for all). The potential regulation of Ang-4 by estrogen was further investigated in vitro. Addition of physiological concentrations of 17beta-estradiol (1 nM) to hormone-free media caused no significant change in Ang-4 mRNA abundance (P = 0.75) in the estrogen receptor-positive cell line MCF-7 after either 2 or 18 h, despite demonstrating induction for the estrogen response gene pS2.
These findings suggest that the Ang/Tie2 pathway plays a significant role in human breast tumor angiogenesis but provide no initial evidence for direct regulation of the pathway by estrogen.
血管生成对于肿瘤的生长和转移至关重要。它是一个复杂的动态过程，由几类血管生成因子协调。Tie2酪氨酸激酶是一个候选家族，其表达主要局限于内皮细胞。Tie2有三种已知的配体，即血管生成素（Ang）-1、Ang-2和Ang-4，它们具有不同的功能效应，但在胚胎血管重塑中发挥着必要作用。由于关于Tie2通路在人类乳腺癌中的数据有限，且我们之前的数据表明乳腺肿瘤通过血管重塑建立血供，因此我们研究了Ang-1、Ang-2、Ang-4和Tie2在一系列正常和肿瘤性人类乳腺组织中的表达。
我们通过逆转录聚合酶链反应检测了6例正常乳腺组织和52例恶性乳腺组织中的mRNA表达，并将表达与临床病理和血管生成变量进行关联。我们还研究了生理水平的雌激素对Ang表达的影响。
在肿瘤样本中，分别有19%、52%、35%和65%检测到Ang-1、Ang-2、Ang-4和Tie2。与正常乳腺组织相比，肿瘤中Ang-1（P = 0.04）、Ang-2（P = 0.01）、Ang-4（P = 0.004）和Tie2（P = 0.02）的表达显著降低。在肿瘤中，所有Ang之间以及每个配体与Tie2之间均存在显著相关性。在多变量分析中，Ang-4与雌激素受体之间存在显著正相关（P = 0.016），Ang-1与胸苷磷酸化酶表达之间存在显著负相关（P = 0.01）。未观察到Ang/Tie2基因家族的其他成员与患者年龄、肿瘤大小、淋巴结状态、肿瘤分级、血管侵犯、肿瘤血管生成、血管成熟、胸苷磷酸化酶或血管内皮生长因子A表达之间存在显著关联（所有P > 0.05）。在体外进一步研究了雌激素对Ang-4的潜在调节作用。在无激素培养基中添加生理浓度的17β-雌二醇（1 nM），在雌激素受体阳性细胞系MCF-7中，2小时或18小时后Ang-4 mRNA丰度均无显著变化（P = 0.75），尽管雌激素反应基因pS2有诱导表达。
这些发现表明Ang/Tie2通路在人类乳腺肿瘤血管生成中起重要作用，但未提供雌激素直接调节该通路的初步证据。
