Adham Sirin A I, Al Rawahi Hasina, Habib Sumaya, Al Moundhri Mansour S, Viloria-Petit Alicia, Coomber Brenda L
Department of Biology, College of Science, Sultan Qaboos University, P. O. Box 36, 123 Muscat, Oman.
Department of Medicine, College of Medicine, Sultan Qaboos University, P.O. Box 35, 123 Muscat, Oman.
PLoS One. 2014 Nov 17;9(11):e113103. doi: 10.1371/journal.pone.0113103. eCollection 2014.
Breast cancer (BC) arises commonly in women with metabolic dysfunction. The underlying mechanism by which glycemic load can exert its action on tumor metastasis is under investigated. In this study we showed that glycemic microenvironment alters the expression of three classes of proteins, VEGF and its receptors, cell to cell, and cell to extracellular matrix (ECM) adhesion proteins in MDA-MB-231 parental cells and its two metastatic variants to the bone and brain (MDA-MB-231BO and MDA-MB-231BR, respectively). Using western blotting, we showed that VEGFR2 levels were higher in these variant cells and persisted in the cells under extreme hypoglycemia. Hypoglycemia did not alter VEGFR2 expression per se but rather suppressed its posttranslational glycosylation. This was reversed rapidly upon the restoration of glucose, and cyclohexamide (CHX) treatment demonstrated that this deglycosylated VEGFR2 was not a product of de-novo protein synthesis. VEGFR2 co-receptor Neuropilin-1 was up-regulated four-fold in all MDA-MB-231 cells (parental and two variants) compared to VEGFR2 expression, and was also susceptible to glycemic changes but resistant to CHX treatment for up to 72 hrs. Hypoglycemia also resulted in a significant decrease in specific catenin, cadherin, and integrin proteins, as well as cellular proliferation and colony forming ability. However, MDA-MB-231BR cells showed a unique sensitivity to hypo/hyperglycemia in terms of morphological changes, colony formation ability, integrin β3 expression and secreted VEGF levels. In conclusion, this study can be translated clinically to provide insight into breast cancer cell responses to glycemic levels relevant for our understanding of the interaction between diabetes and cancer.
乳腺癌（BC）常见于代谢功能障碍的女性。血糖负荷对肿瘤转移发挥作用的潜在机制正在研究中。在本研究中，我们发现血糖微环境改变了MDA-MB-231亲代细胞及其向骨和脑转移的两个变体（分别为MDA-MB-231BO和MDA-MB-231BR）中三类蛋白质的表达，即血管内皮生长因子（VEGF）及其受体、细胞间和细胞与细胞外基质（ECM）粘附蛋白。通过蛋白质印迹法，我们发现这些变体细胞中的血管内皮生长因子受体2（VEGFR2）水平较高，并且在极端低血糖条件下仍持续存在。低血糖本身并未改变VEGFR2的表达，而是抑制了其翻译后糖基化。葡萄糖恢复后，这种情况迅速逆转，环己酰亚胺（CHX）处理表明这种去糖基化的VEGFR2不是从头合成蛋白质的产物。与VEGFR2表达相比，VEGFR2共受体神经纤毛蛋白-1在所有MDA-MB-231细胞（亲代细胞和两个变体）中上调了四倍，并且也易受血糖变化的影响，但在长达72小时的时间内对CHX处理具有抗性。低血糖还导致特定连环蛋白、钙粘蛋白和整合素蛋白显著减少，以及细胞增殖和集落形成能力下降。然而，MDA-MB-231BR细胞在形态变化、集落形成能力、整合素β3表达和分泌的VEGF水平方面对低血糖/高血糖表现出独特的敏感性。总之，本研究可转化应用于临床，以深入了解乳腺癌细胞对血糖水平的反应，这有助于我们理解糖尿病与癌症之间的相互作用。
