McSherry Elaine A, McGee Sharon F, Jirstrom Karin, Doyle Emma M, Brennan Donal J, Landberg Goran, Dervan Peter A, Hopkins Ann M, Gallagher William M
UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Ireland.
Int J Cancer. 2009 Sep 15;125(6):1343-51. doi: 10.1002/ijc.24498.
The cell-cell adhesion protein junctional adhesion molecule-A (JAM-A) influences epithelial cell morphology and migration. As migration is required for tumor cell invasion and metastasis, we sought to elucidate the role of JAM-A in invasive breast cancer. A breast cancer tissue microarray was analyzed for JAM-A protein expression, in parallel with analysis of JAM-A gene expression data from a breast cancer clinical dataset. Our data demonstrate a novel association between JAM-A gene and protein upregulation and poor prognosis in breast cancer. To mechanistically dissect this process, we used lentiviral technology to stably knock down JAM-A gene expression by shRNA in MCF7 breast cancer cells, which express high-endogenous levels of JAM-A. We also antagonized JAM-A function in wild-type MCF7 cells using an inhibitory antibody that blocks JAM-A dimerization. Knockdown or functional antagonism of JAM-A decreased breast cancer cell migration in scratch-wound assays. Reductions in beta1-integrin protein levels were observed after JAM-A-knockdown in MCF7 cells, suggesting a mechanism for reduced motility after loss of JAM-A. Consistent with this hypothesis, tissue microarray analysis of beta1-integrin protein expression in invasive breast cancer tissues revealed a trend toward high beta1-integrin protein levels being indicative of poor prognosis. Twenty-two percent of patients were observed to coexpress high levels of JAM-A and beta1-integrin protein, and MDA-MB-231 breast cells stably overexpressing JAM-A showed an increase in beta1-integrin protein expression. Our results are consistent with a previously unreported role for JAM-A overexpression as a possible mechanism contributing to progression in primary breast cancer; and a potential therapeutic target.
细胞间黏附蛋白连接黏附分子A（JAM-A）影响上皮细胞形态和迁移。由于肿瘤细胞侵袭和转移需要迁移，我们试图阐明JAM-A在浸润性乳腺癌中的作用。对乳腺癌组织芯片进行JAM-A蛋白表达分析，并同时分析来自乳腺癌临床数据集的JAM-A基因表达数据。我们的数据表明JAM-A基因和蛋白上调与乳腺癌预后不良之间存在新的关联。为了从机制上剖析这一过程，我们使用慢病毒技术通过shRNA在高内源性表达JAM-A的MCF7乳腺癌细胞中稳定敲低JAM-A基因表达。我们还使用一种阻断JAM-A二聚化的抑制性抗体在野生型MCF7细胞中拮抗JAM-A功能。在划痕试验中，JAM-A的敲低或功能拮抗降低了乳腺癌细胞的迁移。在MCF7细胞中敲低JAM-A后，观察到β1整合素蛋白水平降低，提示JAM-A缺失后运动性降低的机制。与此假设一致，浸润性乳腺癌组织中β1整合素蛋白表达的组织芯片分析显示，β1整合素蛋白水平高有预后不良的趋势。观察到22%的患者共表达高水平的JAM-A和β1整合素蛋白，稳定过表达JAM-A的MDA-MB-231乳腺癌细胞显示β1整合素蛋白表达增加。我们的结果与之前未报道的JAM-A过表达作为原发性乳腺癌进展的可能机制以及潜在治疗靶点的作用一致。
