麥黃酮抑制神經膠質瘤細胞株其轉移能力之機制及路徑探討

人類惡性腦瘤細胞具有快速增生以及非常高的轉移能力特性，而惡性腦瘤病人的術後存活率都很低且復發率極高，因此尋找控制惡性腦瘤的影響因子是現今很重要的課題。麥黃酮 (Tricetin)，一種在自然界中發現可能具有抑制癌症增生與轉移的類黃酮化合物，但其抑制惡性腦瘤轉移的機制卻還不清楚。因此本實驗利用兩株Glioblastoma cell (GBM8401和U87)進行細胞轉移與侵入的實驗測定。在癌症轉移中，腫瘤會釋出生長因子及基質金屬蛋白酶 (Matrix metalloproteinase, MMP)，分解細胞外基質，形成血管新生，並藉由血液流動，轉移到其他組織。實驗結果發現麥黃酮在濃度20-80 µM之間可以減少MMP-2的活性，再利用Real-time PCR與luciferase assay的實驗中也證實Tricetin可以透過抑制轉錄因子特異蛋白 (SP-1)的DNA結合能力進而抑制MMP-2的表現; 另外在訊息傳遞的部分，也發現加入ERK抑制劑也可以抑制MMP-2的活性，再利用transwell migration assay在tricetin作用下，確實可以觀察到GBM8401細胞的轉移有受到明顯的抑制情形。總結以上本實驗發現麥黃酮對於SP-1具有抑制效果，進而可以調控MMP-2的活性並影響細胞轉移的能力，並且發現麥黃酮結合ERK抑制劑可以更有效抑制腦癌細胞的侵入，期許未來可能可以當作一種預防腦癌的有效試劑。

Glioblastoma multiforme (GBM) is a severely invasive tumor that can be fatal because it is difficult to treat. Tricetin, a natural flavonoid, was demonstrated to inhibit the growth of various cancers, but the effect of tricetin on cancer motility is largely unknown. In the present study, we examined the anti-invasive properties of tricetin in human GBM cells. Our results showed that tricetin (20-80 µM) inhibited the migration/invasion of two GBM cell lines (GBM 8401 and U87). During cancer metastasis, the extracellular matrix (ECM) was decomposed by releasing of growth factors and matrix metalloproteinases (MMPs), followed by angiogenesis formation through the blood flow, and then transferring to other organs. We found that tricetin inhibited matrix metalloproteinase (MMP)-2 expression in the GBM cells. Real-time PCR and promoter activity assays indicated that tricetin inhibited MMP-2 expression at the transcriptional level. Such inhibitory effects were associated with the suppression of specificity protein 1 (SP-1) DNA-binding activity and SP-1 expression. An examination of clinical samples revealed a positive correlation between SP-1 and MMP-2 in glioma specimens, and higher expression levels were correlated with a worse probability of survival. Moreover, blocking the ERK pathway also inhibited MMP-2-mediated cell motility, and further enhanced the anti-invasive ability of tricetin in GBM 8401 cells. In conclusion, SP-1 is an important target of tricetin for suppressing MMP-2-mediated cell motility in GBM cells, and a combination of tricetin and an ERK inhibitor may be a good strategy for preventing GBM invasion.