Smalley Keiran S M, Brafford Patricia, Haass Nikolas K, Brandner Johanna M, Brown Eric, Herlyn Meenhard
Wistar Institute, 3601 Spruce St., Philadelphia, Pennsylvania 19104, USA.
Am J Pathol. 2005 May;166(5):1541-54. doi: 10.1016/S0002-9440(10)62370-X.
During the process of malignant transformation, nascent melanoma cells escape keratinocyte control through down-regulation of E-cadherin and instead communicate among themselves and with fibroblasts via N-cadherin-based cell-cell contacts. The zonula occludens (ZO) protein-1 is a membrane-associated component of both the tight and adherens junctions found at sites of cell-cell contact. In most cancers, levels of ZO-1 are typically down-regulated, leading to increased motility. Here we report the novel observation that ZO-1 expression is up-regulated in melanoma cells and is located at adherens junctions between melanoma cells and fibroblasts. Immunofluorescence and co-immunoprecipitation studies showed co-localization of ZO-1 with N-cadherin. Down-regulation of ZO-1 in melanoma cells through RNA interference produced marked changes in cell morphology--leading to a less-dendritic, more rounded phenotype. Consistent with a role in N-cadherin-based adhesion, RNAi-treated melanoma cells were less adherent and invasive when grown in a collagen gel. These data provide the first evidence that increased ZO-1 expression in melanoma contributes to the oncogenic behavior of this tumor and further illustrate that protein products of genes, such as ZO-1, can function in either a pro- or anti-oncogenic manner when expressed in different cellular contexts.
在恶性转化过程中，新生黑色素瘤细胞通过下调E-钙黏蛋白逃避角质形成细胞的控制，转而通过基于N-钙黏蛋白的细胞间接触在自身之间以及与成纤维细胞之间进行通讯。紧密连接蛋白-1（ZO-1）是在细胞间接触部位发现的紧密连接和黏着连接的膜相关成分。在大多数癌症中，ZO-1的水平通常下调，导致细胞运动性增加。在此我们报告一项新发现，即ZO-1在黑色素瘤细胞中表达上调，且位于黑色素瘤细胞与成纤维细胞之间的黏着连接处。免疫荧光和免疫共沉淀研究显示ZO-1与N-钙黏蛋白共定位。通过RNA干扰下调黑色素瘤细胞中的ZO-1会导致细胞形态发生显著变化——形成较少树突状、更圆的表型。与基于N-钙黏蛋白的黏附作用一致，经RNAi处理的黑色素瘤细胞在胶原凝胶中生长时黏附性和侵袭性较低。这些数据首次证明黑色素瘤中ZO-1表达增加有助于该肿瘤的致癌行为，并进一步说明诸如ZO-1等基因的蛋白质产物在不同细胞环境中表达时可发挥促癌或抑癌作用。
