- 學位論文
葉酸對人類結腸腫瘤細胞的遷移能力之影響
Effects of Folic acid on human colon cancer cell migration
摘要
根據流行病學研究顯示葉酸與乳癌、子宮頸癌、卵巢癌、食道癌、胃癌、胰腺癌、肺癌以及大腸直腸癌之間呈現負相關，且在先前的文獻統計數據指出，攝取大量的葉酸會減少大腸直腸癌罹患的風險，但其所經由的作用機制目前還不是很明確。過去在本實驗室的研究中已經證明葉酸會抑制人類血管內皮細胞的遷移能力，主要是透過活化folic acid receptor/cSrc/p190RhoGAP的訊息傳遞路徑來抑制RhoA的活性，進而達到抑制內皮細胞遷移的作用。然而葉酸是如何影響大腸直腸癌細胞遷移能力的研究文獻目前還不多，且根據先前流行病學的實驗結果發現攝取葉酸能夠降低大腸直腸癌的惡化程度，致使我們推測在大腸直腸癌細胞中，葉酸是否也是透過抑制RhoA活性的機轉來抑制大腸直腸癌細胞的遷移能力，進而去減少大腸直腸癌的發生。根據本實驗室初步的實驗結果發現葉酸會透過抑制COLO-205細胞的生長能力，但在遷移能力的效用還未知。首先利用Transwell invasion assay的實驗結果得知，單獨給予葉酸會抑制COLO-205細胞的遷移能力，但是如果同時給予葉酸與cSrc抑制劑則會回復，藉此我們推測葉酸是透過活化cSrc路徑抑制細胞的遷移。既然已確定葉酸的確會抑制COLO-205細胞的遷移能力，因此，更進一步探討葉酸是透過什麼樣的分子機轉來抑制大腸直腸癌細胞的遷移。我們的實驗結果顯示葉酸是透過活化cSrc/ERK所傳導的訊息途徑增加p27蛋白的表現，進而抑制RhoA的活性，造成COLO-205細胞遷移的抑制作用。
並列摘要
It has been suggested that folic acid has negative correlation with the development of cancers, such as cervical cancer, lung cancer, breast cancer and colorectal cancer. Therefore, high folate intake is associated with decreased risk of colorectal cancer. However, its molecular mechanism underlying is not very clear. Previously, our laboratory demonstrated that folic acid inhibits endothelial cell proliferation through activating the cSrc/ERK2/NF-κB/p53 pathway mediated by folic acid receptor and inhibits endothelial cell migration through inhibiting the RhoA activity mediated by activating the folic acid receptor/cSrc/ p190RhoGAP-signaling pathway. These findings suggest that folic acid can affect the cell proliferation and migration, and encourage me to hypothesize that folic acid might be able to regulate the migration of colorectal cancer cells. Previous studies from our laboratory have shown that folic acid could inhibit COLO-205 proliferation through activating the cSrc/ERK1/2/NFkB/p53 pathway. However, the effect folic acid on COLO-205 cell migration and its mechanisms underlying are still unclear. Using the Transwells assay, our data showed that treatment with folic acid alone significantly reduced the migration ability of COLO-205 cells. Pre-treatment with a cSrc inhibitor, PP2, abolished the folic acid-induced migration inhibition in COLO-205 cells, suggesting that folic acid inhibited the migration of COLO-205 cells through activating the cSrc-mediated pathway. To explore the underlying molecular mechanism folic acid-induced migration inhibition in COLO-205 cells, Western blot analyses were performed. Our data suggest that folic acid activated the cSrc/ERK-mediated signaling pathway to increase the level of p27, which in turn reduced the RhoA activity, eventually inhibiting the migration in COLO-205 cells.