Abstract：
Breast carcinomas originate from cells in the terminal duct-lobular unit. Carcinomas are associated with increased cell proliferation and migration, altered cellular adhesion, as well as loss of epithelial polarity. In breast cancer, aberrant and high levels of aquaporin-5 (AQP5) are associated with increased metastasis, poor prognosis, and cancer recurrence. AQP5 increases the proliferation and migration of cancer cells, and ectopic expression of AQP5 in normal epithelial cells reduces cell-cell adhesion and increases cell detachment and dissemination from migrating cell sheets, the latter via AQP5-mediated activation of the Ras pathway. Here, we investigated if AQP5 also affects cellular polarity by examining the relationship between the essential polarity protein Scribble and AQP5. In tissue samples from invasive lobular and ductal carcinomas, the majority of cells with high AQP5 expression displayed low Scribble levels, indicating an inverse relationship. Probing for interactions via a Glutathione S-transferase pull-down experiment revealed that AQP5 and Scribble interacted. Moreover, overexpression of AQP5 in the breast cancer cell line MCF7 reduced both size and circularity of three-dimensional (3-D) spheroids and induced cell detachment and dissemination from migrating cell sheets. In addition, Scribble levels were reduced. An AQP5 mutant cell line, which cannot activate Ras (AQP5S156A) signaling, displayed unchanged spheroid size and circularity and an intermediate level of Scribble, indicating that the effect of AQP5 on Scribble is, at least in part, dependent on AQP5-mediated activation of Ras. Thus, our results suggest that high AQP5 expression negatively regulates the essential polarity protein Scribble and thus, can affect cellular polarity in breast cancer.
摘要：
乳腺癌起源于终末导管-小叶单位的细胞。癌与细胞增殖和迁移增加有关，细胞粘附改变，以及上皮极性的丧失。在乳腺癌中，AQP5的异常和高水平与转移增加有关，预后不良和癌症复发。AQP5增加癌细胞的增殖和迁移，AQP5在正常上皮细胞中的异位表达减少了细胞与细胞的粘附，增加了细胞从迁移细胞片的脱离和扩散，后者经由过程AQP5介导Ras通路的激活。这里,我们通过检查必需极性蛋白Scribble和AQP5之间的关系来研究AQP5是否也影响细胞极性。在浸润性小叶和导管癌的组织样本中，大多数AQP5高表达的细胞显示出低Scribble水平，表示反比关系。通过GST下拉实验探索相互作用，发现AQP5和Scribble相互作用。此外，AQP5在乳腺癌细胞系MCF7中的过表达降低了3D球体的大小和圆形度，并诱导了细胞从迁移的细胞片脱离和扩散。此外,涂鸦水平降低。AQP5突变细胞系,不能激活Ras(AQP5S156A)，显示不变的球体大小和圆形度，以及中间水平的涂鸦，表明AQP5对涂鸦的影响是，至少在某种程度上,依赖AQP5介导的Ras激活。因此，我们的结果表明，高AQP5表达负调节必需极性蛋白Scribble，会影响乳腺癌的细胞极性。
