英國曼徹斯特大學(University of Manchester)的研究人員,利用胚胎幹細胞〔embryonic stem (ES) cells〕來觀察一些會轉移的腫瘤細胞,因為這種型態的細胞在癌症治療上更加困難。Chris Ward博士發現了一些癌細胞能開始轉移及擴散到其他組織的線索,此研究發表於Molecular Biology of the Cell 期刊。
早期的癌細胞就像正常的上皮細胞(epithelial cells)一樣,細胞之間會緊密的黏在一起形成牢固的組織層,當癌細胞更進一步的發展,有些細胞就會轉變成間葉細胞(mesenchymal cells),間葉細胞彼此之間是不會黏合在一起的,反而是一團混亂又能四處移動的組織,這個過程的變化稱為上皮-間葉的過渡時期(epithelial-mesenchymal transition),這種現象也能在早期的胚胎發育中看到類似的進程。在這個過渡期,細胞喪失了一些能促使彼此黏合的蛋白質,同時也產生了一些能促使癌細胞擴散的蛋白質。希望能透過對ES細胞的研究,了解癌細胞擴散的一些關鍵因子,為癌症轉移提供一個治療之道。
研究團隊發現:「在細胞正常生長的情況下,E-cadherin蛋白能阻止細胞的轉移。E-cadherin蛋白不但能協助細胞緊密黏合,也能阻止其他促進癌細胞轉移的蛋白質的活性,E-cadherin蛋白的這兩種功能,提供了阻止腫瘤細胞擴散的線索。」國際癌症研究協會(Association for International Cancer Research,AICR)的會長Derek Napier就表示:「這項發現將對癌細胞擴散研究的相關領域帶來重大的影響,也期盼由此能找到更多新的策略,以阻止癌細胞的擴散。」
原始出處:
MBC in Press, published online ahead of print May 16, 2007
Mol. Biol. Cell 10.1091/mbc.E06-09-0875
*Centre for Molecular Medicine, Faculty of Medical and Human Sciences, The University of Manchester, Manchester M13 9PT, United Kingdom; Cancer Research UK Immunology Group and Cancer Research UK Stem Cell Biology Group, Paterson Institute for Cancer Research, University of Manchester, Christie Hospital National Health Service Trust, Manchester M20 4BX, United Kingdom; Materials Science Centre, The University of Manchester, Manchester M1 7HS, United Kingdom; ||Department of Molecular Embryology, Max-Planck Institute of Immunobiology, D-79108 Freiburg, Germany
Monitoring Editor: Marianne Bronner-Fraser
Abstract
Epithelial-mesenchymal transition (EMT) events occur during embryonic development and are important for the metastatic spread of epithelial tumors. We show here that spontaneous differentiation of mouse ES cells is associated with an E- to N-cadherin switch, upregulation of E-cadherin repressor molecules (Snail and Slug proteins), gelatinase activity (MMP-2 and MMP-9) and increased cellular motility, all characteristic EMT events. The 5T4 oncofoetal antigen, previously shown to be associated with very early ES cell differentiation and altered motility, is also a part of this coordinated process. E-cadherin, N-cadherin and 5T4 proteins are independently regulated during ES cell differentiation and are not required for induction of EMT-associated transcripts and proteins, as judged from the study of the respective knockout ES cells. Further, abrogation of E-cadherin mediated cell-cell contact in undifferentiated ES cells using neutralizing antibody results in a reversible mesenchymal phenotype and actin cytoskeleton rearrangement which is concomitant with translocation of the 5T4 antigen from the cytoplasm to the cell surface in an energy-dependent manner. E-cadherin null ES cells are constitutively cell surface 5T4 positive and while forced expression of E-cadherin cDNA in these cells is sufficient to restore cell-cell contact, cell surface expression of 5T4 antigen is unchanged. 5T4 and N-cadherin knockout ES cells exhibit significantly decreased motility during EMT, demonstrating a functional role for these proteins in this process. We conclude that E-cadherin protein stabilizes cortical actin cyoskeletal arrangement in ES cells and this can prevent cell surface localization of the promigratory 5T4 antigen.
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