在腫瘤形成的過程中，癌化的組織通常都會比正常的組織來得硬，而這很有可能是由於細胞外基質的沉積所造成的。由一些致癌基因活化之後所致使的細胞轉型過程中，細胞骨架actin細絲結構被打亂及焦點附著蛋白形成的數目下降都是常見的現象。而這種改變跟細胞的懸浮性生長及細胞的癌化過程非常的相關。因此我們假設，經過這樣轉變的癌細胞應該會跟正常細胞有不一樣的生物物理性質。在本篇論文中，我們使用了正常的乳腺上皮細胞(M10)以及三株乳癌細胞株(MCF7，MDA-MB 468，MDA-MB 231) 來進行初步的研究。我們進行了細胞移動能力試驗，侵犯性能力以及固著非依賴性的測試，發現相對於較不惡性的MCF7細胞而言，具有侵犯性的MDA-MB 231細胞的移動能力是最高的。在固著非依賴性的試驗中，我們發現只有癌細胞具有這種可以在非附著的情況下有聚落形成的能力。為了要更進一步的探討這些細胞的生物物理性質，我們使用了原子力顯微鏡(AFM)來進行細胞軟硬度的量測。結果發現，正常的乳腺上皮細胞M10相對於其他的癌細胞有著較高的硬度。然而，在這些癌化的細胞中，最惡性的MDA-MB 231相對於較沒有侵犯能力的MCF7細胞卻有著較高的硬度。也就是說，隨著癌細胞的惡性程度上升，其細胞硬度也會隨之增加。這個現象也可以在肺腺癌細胞CL1系列的細胞中被發現。這個系統中的癌細胞相較於原始分離出來的CL1-0母細胞，較具有侵犯能力的CL1-1及CL1-5細胞都具有著較高的細胞硬度。更重要的是，若是將這些乳癌細胞培養在不同軟硬度的polyacrylamide gel上，則可以發現正常的M10細胞只有些許改變細胞硬度的能力，而non-malignant MCF7的細胞硬度則是不會因為外界環境的硬度改變而改變。最惡性的MDA-MB 231細胞則是會隨著外界基材硬度的下降而降低它們的細胞硬度。分析蛋白質表現的結果顯示，MCF7的β1-integrin and FAK表現很低，而MDA-MB 231則增加了EMT相關蛋白質(如β1-integrin, FAK, vimentin, fibronectin) 的表現。我們推測，MCF7對基質軟硬的不反應也許是因為失去了mechansensory machinery，而MDA-MB 231則是因為癌化的進程EMT而使得它能像fibroblast cells 可以因基質軟硬度的不同而調控細胞的軟硬度。綜合以上，這篇論文的研究方向可以對癌細胞在癌化過程中的物理性質變化，提供更多的了解。

During cancer progression, the tumor tissues become stiffer than normal ones due to deposition of extra cellular matrix (ECM). Disruption of actin filaments and a decrease in focal adhesions are common features following transformation of cells by various oncogenes. Such changes are highly related to both anchorage-independent growth and cellular tumorigenicity. In this study, we hypothesized that cancer cells may exhibit different biophysical properties from normal cells. To test this hypothesis, we performed normal mammary epithelial cell line M10 and three breast cancer cell lines, including MCF7, MDA-MB 468, and MDA-MB 231. We first examined the metastatic potential of these cell lines by migration assay, invasion assay and anchorage-independent assay. The MDA-MB 231 showed the highest migration ability as well as invasiveness compared to the less malignant MCF7 cell lines. In anchorage-independent assay, only cancer cell lines formed colonies while the M10 cell did not. To further evaluate the biophysical properties of these cell lines, we employed atomic force microscopy (AFM) to measure cell stiffness. The data revealed that normal mammary cell line M10 was stiffer than all other cancer cell lines. Among these breast cancer cell lines, MDA-MB 231 showed highest cell stiffness. Similar results were also observed in the CL1 lung adenocarcinoma cell lines where highly invasive CL1-1 and CL1-5 cells exhibited higher cell stiffness compared to the original CL1-0 cells. To further investigate whether these cell lines respond to the external environmental changes, cells were cultured on type I collagen coated polyacrylamide gel with different stiffness. M10 cells exhibited low ability to modulate their cell stiffness on different substrates, whereas MDA-MB 231 cells gradually reduced their cell stiffness on the softer substratum. However, MCF7 did not change their stiffness. By western blot analysis, MCF 7 expressed lowest levels of β1 integrin and FAK and MDA-MB 231 expressed those of EMT related protein, such as β1 integrin, FAK, vimentin, and fibronectin. These data suggested that MCF7 lose its response to substratum stiffness might be due to lack of mechanosensory machinery and malignant MDA-MB 231 behaved like fibroblast to modulate their stiffness on different substratum stiffness probably due to the result of EMT.
Taken together, these studies along this line might unravel how cancer cells alter their physical property during cancer progression.

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