泰若美沛可 (tetra-O-methyl nordihydroguaiaretic acid, M4N) 在人類肝癌細胞中對於CPT1α 的影響

Abstract

本研究主要在探討藉由泰若美沛可 (tetra-O-methyl nordihydro -guaiaretic acid, M4N) 調節肝癌細胞中肉鹼棕櫚醯基轉移酶 (CPT1α) 的表現，達到調控肝癌細胞的生長。腫瘤細胞會自生長環境中吸取大量的能量供其快速生長，但環境中能量大量減少後，便會造成腫瘤細胞的生長壓力；為克服能量缺少所造成的壓力，腫瘤細胞會提高 β 氧化作用路徑，來氧化脂肪酸獲得更多的能量。肉鹼棕櫚醯基轉移酶 (CPT1α) 是 β 氧化作用路徑的重要因子之一，同時 CPT1α 亦扮演增加癌細胞存活率與促進癌細胞移動的角色。M4N 是Nordihydroguaiaretic acid (NDGA) 之衍生物，為 Sp1 專一性的轉錄因子抑制劑，於肝癌細胞可抑制 Sp1 轉錄因子的依賴性基因的表現，並誘發細胞週期停滯與誘導細胞凋亡。經分析 CPT1a 的啟動子後，其具有數個 Sp1 轉錄因子調控區，因此推測 M4N 可能調節 CPT1α 的表現。實驗結果顯示，在培養的 HepG2 肝癌細胞株以 M4N 處理後，M4N 可抑制 HepG2中 CPT1α 的 mRNA 和蛋白質的表現。在 HepG2 細胞中，以不含 Sp1 轉錄因子調控區的 CMV 啟動子驅動表現小鼠 CPT1a 基因時，小鼠 CPT1α 蛋白質會表現於粒腺體，但 M4N 不能降低此外源性 CPT1α 的 mRNA 和蛋白質的表現，且 M4N 對於HepG2 細胞和 CMV 啟動子驅動表現 mCPT1α 之 HepG2 細胞的抑制生長效果相類似。結果顯示 M4N 可以抑制 CPT1α 的 mRNA 轉錄並抑制 CPT1a 蛋白質的表現，且 M4N 可透過調節 CPT1α 的表現來抑制肝癌細胞株的生長。

It has been known tumor cells require amounts of energy to support rapid proliferation. In order to gain energy, tumor cells increase β-oxidation paythway to earn extract energy from metabolism of fatty acid. Carnitine palmitoyltransferase 1 α (CPT1α is the critical factor of β-oxidation, it has been found to promote the survival and migration in several types of human cancers which include liver cancer. From bioinformatics analysis, CPT1α promoter regin contained several regulatory elements of Sp1 transcription factor. A specific inhibitor of Sp1 transcription factor named M4N is a derivative of nordihydroguaiaretic acid (NDGA). It can arrest cell cycle and induce apoptosis by suppressing the regulation of Sp1 transcription factor in liver cancer cells. In this study, we investigated the role of M4N on CPT1α expression to control the cell growth in HepG2 liver cancer cell line. HepG2 cells treated with M4N, mRNA and protein expression of CPT1α were decreased in HepG2 cells. CMV promoter triggered the overexpression of the mice CPT1α (mCPT1α) gene in HepG2 cells. Results showed mCPT1α protein can overexpressed in the mitochondria. However, M4N did not reduce the expression of mCPT1α mRNA and protein. Results also indicated M4N can suppressive HepG2 cells growed in CMV-driven mCPT1α overexpressed HepG2 cells. In this study, M4N can inhibit expression of the CPT1α mRNA and protein to regulate cell growth in HepG2 liver cencer cell line.