高度入侵性A431癌細胞中過氧化氫之生成及MnSOD表現量對細胞轉移及入侵能力探討

Abstract

癌細胞的轉移(metastasis)一直是造成癌症病患致死的主要原因，因此了解癌細胞的轉移機制一直是個重要的研究課題。在過去的文獻中指出，過氧化氫 (H2O2)和癌細胞的惡化有密切的關係，在較惡化的癌細胞體內，H2O2 產生的量的確有明顯上升的情形。在癌細胞惡化的過程中，H2O2可以藉由活化不同的訊息傳遞途徑去活化 matrix metalloproteinase (MMP) 的釋放以及增加癌細胞貼附到細胞外間質 (Extracellular matrix) 的能力, 進而造成癌細胞移動能力以及入侵能力的上升。 在本實驗室稍早的研究中，我們成功的使用Boyden chamber assay從 A431 P 細胞中挑選出一群具有高度入侵性的癌細胞，我們將它們命名為 A431 III。比較這兩株癌細胞之後，我們發現 A431 III 相較於 A431 P 產生較多的 H2O2 ，這個原因可能是由於 A431 III 細胞內抗氧化酵素的表現量改變的關係造成的，包括了MnSOD 的上升以及 Catalase 的下降。由於這些抗氧化素表現量的變化是平衡細胞內 H2O2 的一個重要防禦機制。因此在本實驗中，我們進一步的使用了 MnSOD siRNA 來抑制 MnSOD 表現量，間接的促使細胞內 H2O2 產生的量上升。這些累積在細胞中的 H2O2 促進了癌細胞惡化情形的上升，包括移動能力入侵能力，貼附能力，以及 MMP 釋放的增加。這些結果顯示了 A431 III 入侵能力的上升可能是經由 H2O2 表現量的上升，進而活化細胞移動能力與 增加 MMP 的分泌所造成的結果。

Tumor metastasis has always been the main factor that causes the death of cancer patients, thus it is important to realize the mechanism of cancer metastasis. It has been appreciated for a number of years that H2O2 production is increased in malignant cancer cells. During tumor progression, H2O2 can activate MMP activity, cell-ECM adhesion, and subsequently promotes the capability of cell migration and cell invasion. The signaling pathway involved in these processes are thought to be achieved through redox modification of signaling molecules such as protein kinases and transcription factors. In the previous study from our laboratory, we have selected highly invasive tumor cell sub-line A431III from A431 by using Boyden Chamber Assay (unpublished data). In this study, we take the advantage of this highly invasive sub-line to further explore the role of H2O2 in cancer cells. We find that H2O2 production is increased in A431III sub-line compared to A431P. This result may attribute to differential expression of antioxidants, which were important in balancing cellular H2O2 levels. We find that MnSOD expression is increased whereas catalase is decreased in A431III sub-line compared to A431P. To further investigate the role of H2O2, we used MnSOD siRNA to suppress the expression of MnSOD. Interestingly, the amounts of H2O2 production were increased after transfection of MnSOD siRNA. The elevated H2O2 lead to increase the capabilities of cell migration, cell invasion, cell-ECM adhesion, and MMP expression. These results described above suggesting that H2O2 may act as an important messenger in regulating cell metastasis in A431 III sub-line.