Activating transcription factor 3 (ATF3) 屬於 basic-region leucine zipper (bZIP) 家族中,ATF (Activating transcription factor)/CREB (cAMP response elementbinding) 次家族的一員,可誘導 CCAAT/enhancer-binding protein (C/EBP) 和 AP-1 活化。 ATF 3 是易受不同生理壓力快速誘發的轉錄因子,並在許多研究 中證實其具有誘導癌細胞走向凋亡的能力。坊間常見的健康食品 - 蜂膠,在過去文獻指出,其具有多種生物性功能,包括: 抗菌、抗氧化、抗發炎和抗腫瘤功效等。在本實驗室先前的研究中發現,台灣蜂膠衍生物NBM-TP-007 -GS-002 (GS-002) 和 PPG 在免疫不全裸鼠體內具有抑制神經膠質瘤生長的功效。本研究中探討 GS-002 和 PPG 在肝癌細胞 (Hep3B 和HepG2) 中的抗腫瘤能力。首先,我們發現,GS-002 和 PPG 隨著劑量增加,明顯抑制肝癌細胞生長並誘導 細胞走向凋亡途徑。GS-002 可經由活化細胞凋亡所需的 caspase-3、caspase-9 和PARP cleavage 形式的蛋白質等,使 Hep3B 細胞凋亡。GS-002 和 PPG 皆可引起 ATF3 mRNA 和蛋白質的表現,使肝癌細胞走向細胞凋亡的途徑。此外,本實驗也測試了誘導ATF3 的壓力訊息傳遞路徑-MAPK (mitogen-activated protein kinase) 訊息傳遞路徑中三個主要的路徑,分別為p38,JNK (c-Jun N-terminal kinase)/SAPK(stress-activated protein kinase) 和ERK (extracellular-signal-regulated kinase)) 訊息傳遞路徑,也發現GS-002 可活化MAPK 相關的蛋白質激酶。更進一步利用暫時性基因轉殖使細胞內 ATF3 大量表現,發現在ATF3 過表現並給予GS-002 的情形下,其細胞存活率明顯較對照組低。由上述結果可知,蜂膠衍 生物 GS-002 可透過依賴 ATF3 的細胞死亡路徑使細胞凋亡,達到抗腫瘤的功效。因此,蜂膠衍生物 GS-002 可能具有提供抗肝癌藥物研發及肝癌治療之價值。
Activating transcription factor 3 (ATF3) is a member of the ATF/CREB subfamily of the basic-region leucine zipper (bZIP) family, which includes members of CCAAT/enhancer-binding protein (C/EBP) and AP-1. ATF3 is rapidly up-regulated under various stress conditions and plays an important role in induction of cancer cell apoptosis. NBM-TP-007-GS-002 (GS-002) and PPG are Taiwanese propolis derivatives. Recent reporters indicated that propolis had various biological activities, including anti-microbial, antioxidative, anti-inflammatory and anti-tumoral activity. Our previous examination have found that both GS-002 and PPG significantly inhibited tumor growth in nude mice (Balb/cAnN-Foxn1nu/CrlNarl) which bearing xenografts of C6 glioma cells. In this study, we have examined the anti-tumoral effect of GS-002 and PPG in human hepatoma cells Hep3B and HepG2 in vitro. First we found that GS-002 and PPG significantly inhibited cell proliferation and induced cell apoptosis by a dose-dependent manner. Several main apoptotic indicators were found in GS-002- and PPG-treated cells, such as cleavage form of caspase-3、caspase-9 and PARP. Both GS-002 and PPG also dose-dependently induced the mRNA and protein expression of ATF3. The induction of ATF3 expression is mediated through mitogen-activated protein kinases (MAPKs) signalling pathways in GS-002-treated cells. Furthermore we found that GS-002 induced more cell apoptosis in ATF3 overexpression cells than control cells. These results suggest that the induction of apoptosis by propolis derivatives GS-002 is partially mediated through ATF3-dependent pathway, and the GS-002 has a potential to develop as a anti-tumoral drug.