- 學位論文
紫檀芪抑制乳癌細胞株之侵襲與癌化能力機轉探討
Studies on the anti-invasive and anti-tumorigenic mechanisms of pterostilbene in human breast cancer cells
摘要
Pterosti lbene是一個resveratrol的甲基結構衍生物，由葡萄、藍莓中所萃取出的多酚化合物。Pterostilbene具有許多藥理的特性，像是：抗癌、抗發炎、抗氧化、細胞凋亡、抗增生與止痛的能力。然而，有關pterostilbene對於預防癌細胞的侵襲與癌化能力，仍不清楚。在本篇論文中主要利用人類乳腺癌細胞株（MCF-7）來探討當細胞內HER2過度活化情形下，pterostilbene抑制癌細胞侵襲與癌化的機轉，其中包括pterostilbene對於HRG-β1誘發癌細胞轉移的MMP-9與促進癌細胞增生主要因子FASN的影響。隨著pterostilbene處理的濃度增加，MMP-9蛋白質與mRNA表現亦隨之下降，MAPKs訊息傳遞路徑的p38磷酸化會隨著pterostilbene劑量增加而受到抑制。而細胞的存活率隨著pterostilbene處理的時間與濃度增加，導致存活率下降，並使停留在G1細胞週期的細胞數目比例增加。此外，我們發現調控細胞生長的主要因子FASN，亦會隨著pterostilbene處理的濃度增加，降低其蛋白質與mRNA表現，同時誘發FASN活化的PI3K/Akt路徑中Akt磷酸化表現亦受到抑制。Pterostilbene並能夠降低FASN mRNA與蛋白質表現量。綜合以上結果，說明了pterostilbene癌症化學預防的潛力，pterostilbene可作為抑制HER2過量表現之乳癌細胞轉移與癌化能力之抑制劑。
並列摘要
Pterostilbene (trans-3,5-dimethoxy-4’-hydroxystilbene) is a natural dimethylated analogue of resveratrol. Similar to diverse pharmacologic activities of resveratrol, Pterostilbene (trans-3,5-dimethoxy-4’-hydroxystilbene) is a natural dimethylated analogue of resveratrol. Similar to diverse pharmacologic activities of resveratrol, pterostilbene exerts its cancer chemopreventive activity including anticancer, anti-inflammation, antioxidation, apoptosis, antiproliferation and analgesic potential. However, the cancer chemopreventive mechanisms of action of pterostilbene remain unclear yet. Almost 25% of breast cancers overexpress HER2, a member of epidermal growth factor receptor family with a more aggressive phenotype with decreased survival. Overexpression of HER2 leads to receptor activation, stimulation of tumor cell proliferation, survival and metastases and is associated with a poor prognosis in patients with primary breast cancer. In addition, matrix metalloproteinases (MMPs)-9, a group of zinc-dependent endopeptidases, is related to tumor invasion and metastasis by their capacity for tissue remodeling via extracellular matrix as well as basement membrane degradation and induction of angiogenesis. Among them, the expression of MMP-9 mediated by HER2 or its releated ligand such as heregulin-β1 (HRG-β1, a combinatorial ligand for the HER3 and HER4 receptors can transactivate HER2 receptor) has been shown to be highly associated with breast cancer metastasis, suggesting that MMP-9 may be an accessible target for improving the health of breast cancer patients under metastatic progression. Recently, many studies have demonstrated that fatty acid synthase expression positively correlates with the level of Her-2/neu oncogene expression in a panel of human breast cancer cell lines. Fatty acid synthase (FASN) is a key enzyme that catalytes de novo fatty acid biosynthesis. In breast cancer cells, the expression of FASN is closely related to the aggressiveness of cancers as well as to the growth, proliferation, maintenance, and cell cycle progression of human cancers. A recent discovery about a bi-directional linkage of FASN with the oncogenic HER2 pathway, a positive correlation between high levels of FASN expression and overexpression of HER2 oncogene exists in human breast cancer cell lines, suggesting that upregulation of FASN expression and activity might play a vital role in HER2-induced tumorigenesis and breast cancer progression. In this study, we assessed the effects of pterostilbene on HRG-β1-associated cell signaling of human breast cancer MCF-7 cells. We found that pterostilbene inhibited HRG-β1-induced activation of PI3K/Akt patheay of MCF-7 cells, accompanied with the dose-related reduction of HRG-β1-induced fatty acid synthase (FASN) expression. Pterostilbene also inhibited mRNA and protein expression of matrix metalloproteinase-9 (MMP-9) induced by HRG-β1via inhibiting p38 MAPK pathwy. Moreover, pterostilbene strongly inhibited HRG-β1-triggered MCF-7 cells proliferation by MTT assay. Taken together, our current data demonstrate that pterostilbene may down-regulate HRG-β1-mediated signaling essential for cell proliferation and metastasis of breast cancer cells, but the detailed action mechanisms require further investigation.