肝癌細胞中自體吞噬現象之探討

Abstract

肝癌是世界上常見的癌症，發生率排名第五，而致死率則高居第三，但是卻遲遲未出現有效的藥物治療。Statins 在臨床前實驗中，發現其對於癌症的預防具有發展潛力，在我們的研究中，證明了其發展為肝癌治療用藥的潛力。我們發現，atorvastatin在試管內或活體實驗中可抑制肝癌細胞株的生長，在皮下腫瘤的模式，利用電子顯微鏡觀察其細胞型態的改變，裸鼠餵食atorvastatin能讓其皮下移植的腫瘤有自體吞噬的現象。配合西方點墨法確認有給予atorvastatin的腫瘤細胞中LC3-II有增加現象。Atorvastatin 藉由活化AMPK抑制mTOR，使肝癌細胞產生自體吞噬現象，除了自體吞噬外，atorvastatin也引起了細胞凋零現象。合併atorvastatin以及自體吞噬抑制劑（3-MA或baf A1），可抑制atorvastatin所產生的自體吞噬，增加其對癌細胞的毒殺作用以及細胞凋零之現象。因此，atorvastatin在肝癌細胞所引起的自體吞噬現象，可能是扮演細胞保護並對抗細胞凋零的角色，若合併自體吞噬抑制劑，可加強atorvastatin對肝癌的治療效果。本研究還使用HDAC inhibitor---SAHA進行實驗，同樣看到其抑制肝癌細胞株之生長，以及自體吞噬和細胞凋零現象。然而，合併SAHA和自體吞噬抑制劑，卻降低SAHA對於肝癌細胞的毒性，因此SAHA所引發之自體吞噬現象，可能是走向細胞死亡。 本研究證明了atorvastatin 以及SAHA使用於肝癌治療的潛力，這兩種藥物所產生之自體吞噬現象，為治療肝癌的重要標的。

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer death worldwide. Drug treatments for HCC have been largely unsuccessful. Statins show promise for cancer prevention in preclinical and randomized controlled studies. This study investigated the potential of atorvastatin as a treatment for HCC. Atorvastatin inhibited cell growth of Huh7 cells in vitro and in vivo. In xenograft model, morphologic examinations by electron microscopy revealed atorvastatin-induced autophagosome formation. Increase in LC3-II and beclin-1 were also observed by Western blotting. Atorvastatin induced autophagy in an AMPK/mTOR pathway, and also induced apoptosis in Huh7 cells. Both of them were involved in atorvastatin-induced cell death. The atorvastatin-induced cell death and apoptosis could be enhanced by autophagy inhibitors, 3-MA and baf A1. Thus, atorvastatin induced autophagy might lead to cell survival and anti-apoptosis. We also found that a HDAC inhibitor, SAHA, induced autophagy and apoptosis. However, SAHA-induced cell death could be reversed by autophagy inhibitors or using Atg5-/- MEFs, indicating that SAHA induced autophagic cell death. Taken together, our results show the potential of atorvastatin and SAHA as a treatment for HCC. In addition, the pharmacological targeting of autophagy provides promise for the management of cancer therapy.