在腫瘤生長及轉移的過程中需要新的血管由周邊發展出來，供給腫瘤細胞所需的氧氣、養份及生長因子。在腫瘤生長的過程中，由於生長速度過快造成內部血管來不及長好，而形成一種缺氧的環境。細胞在缺氧環境下會開啟缺氧誘發因子 (hypoxia-inducible factor 1, HIF-1) 的調控路徑，促進腫瘤生長及血管新生。HIF-1是一種由 HIF-1α及HIF-1β組成的異形二聚物 (heterodimer) 。當HIF-1α 與下游基因調控子中的缺氧反應元件 (hypoxia-response element, HRE) 結合後，啟動下游的缺氧反應基因轉錄，例如: 血管內皮細胞生長因子 (vascular endothelial growth factor, VEGF)。血管內皮細胞生長因子為一個血管新生因子，幫助血管新生有助於腫瘤細胞的生長，因此透過減少血管內皮細胞生長因子的分泌，能有效抑制血管新生及抗腫瘤生長。半枝蓮 (Scutellaria barbata, S. barbata) 為一中草藥，被用於抗發炎及抗腫瘤的治療上。在過去的研究中指出半枝蓮可以抑制腫瘤生長及誘發癌細胞發生細胞凋亡 (apoptosis)。在我們的研究中，試圖建立一個由帶有缺氧反應元件 (Hypoxia response element) 調控子調控的冷光酶 (luciferase) 基因 (6xHRE-Luc) 當作篩選具抑制血管新生功能的中草藥平台。我們利用人類肺腺癌細胞CL1-5在多種中草藥中做篩選，發現半枝蓮萃取液可以透過減少HIF-1 α蛋白量，抑制由缺氧誘發升高的HIF-1轉錄活性。我們進一步證實給予半枝蓮的人類肺腺癌細胞其分泌血管內皮細胞生長因子的能力被抑制。由於半枝蓮減少癌細胞分泌的血管內皮細胞生長因子，因此我們利用博登細胞爬行分析 (Boyden chamber) 證明，半枝蓮可抑制人類臍帶微血管的內皮細胞 (human microvascular endothelial cell line-1, HMEC-1) 的爬行及增生。同時我們也證實半枝蓮可透過抑制Akt磷酸化路徑，而減少HIF-1α蛋白表現。此研究中，我們證實半枝蓮具有抑制肺腺癌的效果，進一步提供中草藥未來在臨床運用的機會。

Angiogenesis is the formation of new blood vessels from preexisting ones and is required for supplying oxygen, nutrient, and growth factors to tumor growth and metastasis. In the processes of tumor growth, a rapidly growing tumor mass quickly outstrips its vasculature and lacks oxygen and nutrients, thus making a hypoxia environment. One way that cells respond to hypoxia is through hypoxia-inducible factor 1 (HIF-1), leading to promoting tumor growth and angiogenesis. HIF-1 is a heterodimer that consists of the hypoxic response factor HIF-1α and HIF-1β. HIF-1α binds to hypoxia-response elements (HREs), thereby activating the expression of numerous hypoxia-response genes, such as vascular endothelial growth factor (VEGF). VEGF is an angiogenic factor, which regulates neoangiogenesis to promote tumor growth. Therefore, anti-angiogenesis is a promising approach for cancer therapy. Scutellaria barbata is a traditional Chinese medicine and has been used as anti-inflammatory and antitumor agents. Previous studies have shown that S. barbata inhibits tumor growth and induces cancer cell apoptosis. In this study, we constructed a reporter vector in which a luciferase reporter gene was driven by the CMV minimal promoter conjugated with HREs as a selective platform to screen herbal medicines as anticancer drugs. In several herbal medicines, we found that the extract of S. barbata could decrease the transcriptional activity of HIF-1 under hypoxic condition in CL1-5 lung adenocarcinoma cells through the reduction of HIF-1α protein level. The production of VEGF in CL1-5 cells was reduced after S. barbata treatment. S. barbata inhibited migration and proliferation of human microvascular endothelial cells (HMEC-1), as demonstrated by the Boyden chamber assay. Furthermore, S. barbata decreased HIF-1α expression through inhibiting the phosphorylation of Akt. Taken together, this study demonstrated therapeutic efficacy of S. barbata for lung adenocarcinoma. Furthermore, this strategy may have implications for clinical trials on this cancer.

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