Department of Genetics, Albert Einstein College of Medicine, Yeshiva University, 1301 Morris Park Avenue, Bronx, NY 10461, USA.
Breast Cancer Res. 2011 Aug 10;13(4):R76. doi: 10.1186/bcr2924.
Altered expression of Septin 9 (SEPT9), a septin coding for multiple isoform variants, has been observed in several carcinomas, including colorectal, head and neck, ovarian and breast, compared to normal tissues. The mechanisms regulating its expression during tumor initiation and progression in vivo and the oncogenic function of its different isoforms remain elusive.
Using an integrative approach, we investigated SEPT9 at the genetic, epigenetic, mRNA and protein levels in breast cancer. We analyzed a panel of breast cancer cell lines, human primary tumors and corresponding tumor-free areas, normal breast tissues from reduction mammoplasty patients, as well as primary mammary gland adenocarcinomas derived from the polyoma virus middle T antigen, or PyMT, mouse model. MCF7 clones expressing individual GFP-tagged SEPT9 isoforms were used to determine their respective intracellular distributions and effects on cell migration.
An overall increase in gene amplification and altered expression of SEPT9 were observed during breast tumorigenesis. We identified an intragenic alternative promoter at which methylation regulates SEPT9_v3 expression. Transfection of specific GFP-SEPT9 isoforms in MCF7 cells indicates that these isoforms exhibit differential localization and affect migration rates. Additionally, the loss of an uncharacterized SEPT9 nucleolar localization is observed during tumorigenesis.
In this study, we found conserved in vivo changes of SEPT9 gene amplification and overexpression during human and mouse breast tumorigenesis. We show that DNA methylation is a prominent mechanism responsible for regulating differential SEPT9 isoform expression and that breast tumor samples exhibit distinctive SEPT9 intracellular localization. Together, these findings support the significance of SEPT9 as a promising tool in breast cancer detection and further emphasize the importance of analyzing and targeting SEPT9 isoform-specific expression and function.
与正常组织相比，在几种癌症中，包括结直肠癌、头颈部癌、卵巢癌和乳腺癌，观察到 Septin 9（SEPT9）的表达发生改变，SEPT9 是一种编码多种同工型变体的 septin。其在体内肿瘤起始和进展过程中的表达调控机制及其不同同工型的致癌功能仍不清楚。
我们采用综合方法研究了乳腺癌中 SEPT9 的遗传、表观遗传、mRNA 和蛋白质水平。我们分析了一组乳腺癌细胞系、人原发性肿瘤及其对应的无肿瘤区域、来自减肥乳房切除术患者的正常乳腺组织，以及源自多瘤病毒中 T 抗原或 PyMT 的原发性乳腺腺癌细胞。用于确定其各自的细胞内分布和对细胞迁移影响的 MCF7 克隆表达单个 GFP 标记的 SEPT9 同工型。
在乳腺癌发生过程中观察到基因扩增和 SEPT9 表达的总体增加。我们确定了一个内含子内的替代启动子，其甲基化调节 SEPT9_v3 的表达。在 MCF7 细胞中转染特定的 GFP-SEPT9 同工型表明，这些同工型表现出不同的定位并影响迁移率。此外，在肿瘤发生过程中观察到未表征的 SEPT9 核仁定位丧失。
在这项研究中，我们发现 SEPT9 基因扩增和过表达在人类和小鼠乳腺癌发生过程中有一致的体内变化。我们表明，DNA 甲基化是调节 SEPT9 同工型表达差异的主要机制，并且乳腺癌样本表现出独特的 SEPT9 细胞内定位。这些发现共同支持 SEPT9 作为乳腺癌检测的有前途工具的重要性，并进一步强调了分析和靶向 SEPT9 同工型特异性表达和功能的重要性。
