Li Jian-Yi, Zhang Yang, Zhang Wen-Hai, Jia Shi, Kang Ye, Zhu Xiao-Yu
Department of Breast Surgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning Province, China.
Asian Pac J Cancer Prev. 2012;13(5):1901-6. doi: 10.7314/apjcp.2012.13.5.1901.
The discovery that microRNA (miRNA) regulates metastasis provide a principal molecular basis for tumor heterogeneity. A characteristic of solid tumors is their heterogenous distribution of blood vessels, with significant hypoxia occurring in regions (centers of tumor) of low blood flow. It is necessary to discover the mechanism of breast cancer metastasis in relation to the fact that there is a differential distribution of crucial microRNA in tumors from centers to edges.
Breast tissues from 48 patients (32 patients with breast cancer) were classified into the high invasive and metastatic group (HIMG), low invasive and metastatic group (LIMG), and normal group. Samples were collected from both the centers and edges of all tumors. The first six specimens were detected by microRNA array, and the second ten specimens were detected by real-time qRT- PCR and Western blot analyses. Correlation analysis was performed between the miRNAs and target proteins.
The relative content of miR-20a and miR-20b was lower in the center of the tumor than at the edge in the LIMG, lower at the edge of the tumor than in the center in the HIMG, and lower in breast cancer tissues than in normal tissues. VEGF-A and HIF-1alpha mRNA levels were higher in the HIMG than in the LIMG, and levels were higher in both groups than in the normal group; there was no difference in mRNA levels between the edge and center of the tumor. VEGF-A and HIF-1alpha protein levels were higher in the HIMG than in the LIMG, and protein levels in both groups were higher than in the normal group; there was a significant difference in protein expression between the edge and center of the tumor. Correlation analysis showed that the key miRNAs (miR-20a and miR-20b) negatively correlated with the target proteins (VEGF-A and HIF-1alpha).
Our data suggest that miR-20a and miR-20b are differentially distributed in breast cancer, while VEGF-A and HIF-1alpha mRNA had coincident distributions, and VEGF-A and HIF-1alpha proteins had uneven and opposing distributions to the miRNAs. It appears that one of the most important facets underlying metastatic heterogeneity is the differential distribution of miR-20a and miR-20b and their regulation of target proteins.
微小RNA（miRNA）调控转移的发现为肿瘤异质性提供了主要分子基础。实体瘤的一个特征是其血管分布不均，在低血流区域（肿瘤中心）会出现明显的缺氧。鉴于关键微小RNA在肿瘤中心到边缘存在差异分布，有必要探寻其与乳腺癌转移相关的机制。
将48例患者（32例乳腺癌患者）的乳腺组织分为高侵袭转移组（HIMG）、低侵袭转移组（LIMG）和正常组。从所有肿瘤的中心和边缘采集样本。前六个样本通过微小RNA芯片检测，后十个样本通过实时定量逆转录-聚合酶链反应（qRT-PCR）和蛋白质免疫印迹分析进行检测。对miRNA与靶蛋白进行相关性分析。
在LIMG中，肿瘤中心的miR-20a和miR-20b相对含量低于边缘；在HIMG中，肿瘤边缘的miR-20a和miR-20b相对含量低于中心；在乳腺癌组织中的miR-20a和miR-20b相对含量低于正常组织。HIMG中VEGF-A和HIF-1α mRNA水平高于LIMG，两组均高于正常组；肿瘤边缘和中心的mRNA水平无差异。HIMG中VEGF-A和HIF-1α蛋白水平高于LIMG，两组均高于正常组；肿瘤边缘和中心的蛋白表达存在显著差异。相关性分析表明，关键miRNA（miR-20a和miR-20b）与靶蛋白（VEGF-A和HIF-1α）呈负相关。
我们的数据表明，miR-20a和miR-20b在乳腺癌中分布存在差异，而VEGF-A和HIF-1α mRNA分布一致，VEGF-A和HIF-1α蛋白分布不均且与miRNA相反。看来转移异质性的一个最重要方面是miR-20a和miR-20b的差异分布及其对靶蛋白的调控。
