Pheophorbide a, an Active Component in Scutellaria barbata, Reverses P-glycoprotein-mediated Multidrug Resistance on a Human Hepatoma Cell Line R-HepG2

Patrick Ming-Kuen Tang, Judy Yuet-Wa Chan, Dong-Mei Zhang, Shannon Wing-Ngor Au, Wing-Ping Fong, Siu-Kai Kong, Stephen Kwok-Wing Tsui, Mary Mui-Yee Waye, Thomas Chung-Wai Mak and Kowk-Pui Fung

volume 6 | issue 4

April 2007
Pages: 504 - 509

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Scutellaria barbata, a Traditional Chinese Medicine native in southern China, has been widely used for treating liver diseases. In this study, the anti-proliferative effect of Pheophorbide a (Pa), an active component from S. barbata, was examined on a multi-drug resistant (MDR) human hepatoma cell line R-HepG2. Our study showed that Pa could significantly inhibit the growth of R-HepG2 cells with an IC50 value at 25.0μM after 48 hours treatment. When compared with the parental HepG2 cells, Pa showed weak resistance to R-HepG2. Efflux of Pa out of R-HepG2 cells was not observed as its cellular uptake level showed no significant difference comparing with HepG2 cells. Interestingly, significant reduction of P-glycoprotein expression on Pa-treated R-HepG2 cells was found at both transcriptional and translational levels, leading to reduction of P-glycoprotein activity. In addition, mechanistic study elucidated that Pa induced cell cycle arrest at G2/M phase and inhibited the expressions of G2/M phase cell cycle regulatory proteins, cyclin-A1 and cdc2 in a dose-dependent manner.