洛神葉萃取物在活體中抗前列腺癌之研究

洛神葉(Hibiscus sabdariffa Linnaeus leaf)在東南亞一帶為普遍烹煮的蔬菜類食物，過去的研究顯示洛神葉中富含有類黃酮等多酚(polyphenol)成分，並具有降血糖及抑制雄激素之功效，顯示洛神葉可以扮演一個化學預防的角色。近年來，許多研究趨向以天然物質來抑制或延遲癌症的發生，可食的植物被認為是抗癌藥物的來源之一。因此本研究以洛神葉水萃取物(H. sabdariffa L. leaf extract, HLE)、多酚萃取物(H. sabdariffa leaf ployphenol-rich extract, HLP)以及洛神植株特有類黃酮類之棉花皮素(gossypetin)為實驗材料，利用裸鼠移植性腫瘤試驗模式，分析在in vivo狀態下HLE、HLP和gossypetin之抑癌作用及其機轉。動物實驗結果中發現：HLE、HLP和gossypetin對於LNCaP細胞移植誘導之裸鼠，可以有效抑制腫瘤的發生、腫瘤生長以及促進細胞死亡。HLE、HLP和gossypetin也能夠有效降低血清中總前列腺特異抗原( total prostate specific antigen, tPSA)含量、血紅素以及腫瘤組織中VEGF的表現，也顯示出HLE、HLP和gossypetin可能具有抑制轉移及血管新生之能力。進一步藉由TUNEL實驗得知，HLE、HLP和gossypetin使腫瘤組織內細胞凋亡；再以西方點墨法及免疫組織染色法進行腫瘤組織蛋白分析，提出HLE和HLP可能藉由調控Bax及FasL機轉路徑以促使腫瘤細胞邁向凋亡，進而抑制腫瘤之形成及生長。並證實HLE、HLP和gossypetin抑制腫瘤組織增生及減少惡化之情形；其調控路徑可能透過p53、p21、p27相關蛋白使細胞週期停滯及LXRα/ABCA1/Flotillin路徑抑制前列腺癌細胞的惡化表現。綜合動物實驗的結果，洛神葉具有成為抗前列腺癌試劑之潛力，並期許在洛神葉在農業以及經濟應用上更具有價值。

Roselle leaves (Hibiscus sabdariffa Linnaeus leaf) are generally cooked vegetable foods in Southeast Asia. Previous studies have indicated H. sabdariffa L. leaf extract (HLE) has antioxidant and estrogenic-like effects. In this study, investigations were conducted to examine the anticancer activity of HLE, its polyphenolic extracts (HLP) and gossypetin on human prostate cancer LNCaP cells in xenograft tumor studies (in vivo). When the nude mice were injected subcutaneously with LNCaP cells, HLE, HLP and gossypetin resulted in inhibition of tumor incidence, volume and weight. TUNEL assay showed that the HLE, HLP, and gossypetin induced apoptosis in the tumor tissue. Western blotting and immunohistochemistry demonstrated that the apoptosis effects of HLE, HLP and gossypetin might be mediated via regulation of Bax/Bcl and activation of caspase-3. In addition, HLE, HLP and gossypetin affected the cell cycle arrest-related proteins (p53, p21 and p27) expressions and caused an increase in the expression of LXRα/ABCA1/flotillin pathway. Finally, HLE, HLP and gossypetin also reduced the expression of VEGF, serum total prostate specific antigen (tPSA) and hemoglobin (Hb). Thus, our data indicate that HLE, HLP and gossypetin could play inducer roles in apoptosis and cell cycle arrest, and inhibitior roles in progression of human prostate cancer and might be potential drugs for antitumor therapy. Our findings indicate that Hibiscus leaves could be developed as potent anticancer agents and natural healthy foods for the management of cancer.