腫瘤微環境在癌症的進程中扮演了決定性的角色，而腫瘤相關巨噬細胞是腫瘤微環境中主要促成腫瘤轉移以及血管新生的主要一員。然而，關於癌細胞是如何教育巨噬細胞，使巨噬細胞轉變成促進腫瘤生長的表現型態，這點仍然是未知的。Eps8的高表達在很多的癌症中被發現，並且與癌症病人較差的癒後狀況有關。本研究在探討是否癌細胞內Eps8扮演著調控巨噬細胞活性的重要角色。在此實驗中，共同培養的條件下我們發 現4T1和RAW 264.7的細胞爬行能力都是上升的，然而壓制4T1中的Eps8表達不但會抑制4T1自身的爬行能力，也連帶影響RAW 264.7細胞；此外，在共同培養時4T1及RAW 264.7的Eps8表現及Src和FAK的活性都是增加的。在動物實驗方面，壓制4T1細胞內Eps8表達會減少腫瘤的大小並且降低巨噬細胞在腫瘤中的聚集；更進一步的，我們發現Eps8基因轉殖鼠相較於一般小鼠，有較高的乳癌轉移比例以及巨噬細胞的聚集。綜合上述，我們可知4T1中的Eps8扮演重要的因子，會去活化癌細胞與巨噬細胞內Src和FAK的活性，並且促進腫瘤的形成。

Tumor microenvironment (TME) has been highlighted as an important entity to determine the progression of human cancer. Tumor associated macrophages (TAMs) are the major components in TME to promote tumor angiogenesis and metastasis. However, how cancer cells re-educate macrophages toward tumor-promoting phenotypes remains largely unknown. Eps8 is expressed at elevated levels in various types of cancer and correlates with poor prognosis in cancer patients. In this study, we want to address whether Eps8 participates in the interaction between macrophage and cancer cells to promote tumor progression. By using ibidi insert to create a co-culture system, we observed the enhanced motility of both 4T1 cells and RAW 264.7 cells. However, silencing Eps8 in 4T1 cells reduced the cell motility of both 4T1 and RAW 264.7 cells. Besides, when directly mixed 4T1 and RAW 264.7 cells together in the culture dish, we found that the expression of Eps8 and the active form of Src, FAK, STAT3 and ERK were elevated. Next, when these cells were cultured in a transwell chamber, the expression of Eps8 and the kinase activity of Src and FAK in both 4T1 and RAW 264.7 cells were still upregulated and silencing Eps8 in 4T1 abolished this phenomenon. In animal study, we discovered that knockdown of Eps8 in 4T1 cells inhibited tumor formation and impaired macrophage recruitment. Moreover, Eps8 transgenic mice appeared to have increasing breast cancer metastasis and macrophage recruitment compared with wild type mice. Taken together, results of this study indicated that Eps8 in 4T1 cells act as an important activator to mediate the activation of FAK and Src in both 4T1 and RAW264.7 cells.

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