In vitro studies (human cell lines)
Lucidenic acids (triterpenoids) isolated from Ganoderma lucidum (YK-02 strain) have been reported to have antiinvasive effects on human hepatoma cells (Weng et al., 2007). Triterpene-enriched extracts from Ganoderma lucidum have also been shown to inhibit growth of human hepatoma Huh-7 cells via suppression of protein kinase C, activating mitogen-activated protein kinases (intermediates in hormonal signalling pathways) and G2-phase cell cycle arrest. In contrast, the extracts did not inhibit growth of Chang liver cells, a normal human liver cell line (Lin et al., 2003).
Native and sulfated fractions of a water-soluble, hyperbranched beta-glucan, extracted from sclerotia of Pleurotus tuberregium possess anti-tumour activities in vivo and in vitro. The sulfated derivatives exhibited relatively higher in vitro anti-tumour activity against the human hepatic cancer cell line HepG2 than a native fraction. Water solubility and introduction of sulfate groups were the main factors in enhancing anti-tumour activity (Tao et al., 2006).
The cultivated mycelium of Cordyceps sinensis has also been shown to produce a significant and dose-dependent inhibitory effect on the proliferation of HepG2 human hepatocellular carcinoma (Wu et al., 2007b).
Chaga (Inonotus obliquus) extract has also been shown to inhibit cell growth in HepG2 cells in a dose-dependent manner, which was accompanied with G0/G1-phase arrest and apoptotic cell death. In addition, G0/G1 arrest in the cell cycle was closely associated with down-regulation of p53, pRb, p27, cyclins D1, D2, E, cyclin-dependent kinase (Cdk) 2, Cdk4, and Cdk6 expression (Youn et al., 2008).
Animal model (rat) studies
An aqueous extract of Agaricus blazei has been shown to exert a hepato-protective effect on both liver toxicity and hepato-carcinogenesis on rat liver toxicity induced by different doses of diethylnitrosamine (Barbisan et al., 2002).
A subsequent study from another group has also demonstrated the chemo-preventative potential of an Agaricus blazei (Ab) Murrill mushroom meal in a medium-term rat liver carcinogenesis model (Pinheiro et al., 2003). Addition of Pleurotus pulmonarius extracts in the diet of mice has also been shown to delay progression of a chemically induced hepatocellular carcinoma (Wasonga et al., 2008).