荔枝花乙醇萃取物誘導肝癌細胞(HepG2)凋亡與自體吞噬之研究

Abstract

Litchi (Litchi chinensis Sonn.) belonging to Sapindaceae family is an important commercial crops in Taiwan, which blooms in late March and fruit matures in late June. The flower is usually considered as disposable agricultural byproducts. Our pervious study found that litchi flower extract had a noticeable phenolic level and also exhibited good antioxidant and anti-inflammatory activities. Reports indicated that phenolic compounds had good anti-carcinogenic effect. There are, however, no related reports regarding anti-carcinogenic effect of litchi flower. In this study, cytotoxic activity of ethanolic extract from litchi flower on A549, KB, MCF-7 and HepG2 cancer cell lines was evaluated first. The litchi flower extract had better anti-proliferative effect on HepG2 cells. Through the comparative experiments with Clone 9 normal rat liver cell line and two drugs (fluorouracil (5-FU) and methotrexate (MTX) used in the treatment of cancer), 0.3 mg/ml is the best concentration used to investigate the apoptotic and autophagic mechanisms for the litchi flower extract-induced death in HepG2 cells. Cell cycle analysis showed that HepG2 cell treated with ethanolic extract from litchi flower was arrested at G2/M phase. Western blot analysis showed that ethanolic extract from litchi flower-induced HepG2 cell apoptosis should attribute decrease of Bcl-2 expression and increase of Bid expression; furthermore, decreased expression of procaspases-3, 7, 8 and 9, and increased PARP degradation could also be observed. For PI3K/Akt pathway, expression of PI3K and Akt was increased, and phosphorelation of Akt was down-regulated through treatment of the litchi flower extract, which led to HepG2 cell apoptosis. Moreover, ethanolic extract from litchi flower-induced HepG2 cell autophagy should attribute increase of p53 expression, which suppressed expression of phosphorylated mTOR, phosphorylated p70S6K, PS6K(D57) and PS6K(D58), and up-regulated LC3 I/II expression.