Ganoderic acid X

Lanostanoid triterpenes isolated from Ganoderma amboinense were found to inhibit the growth of numerous cancer cell lines, and some of them inhibited the activities of topoisomerases I and IIalpha in vitro. Among the bioactive isolates, one of the most potent triterpene was identified to be 3 alpha-hydroxy-15 alpha-acetoxy-lanosta-7,9(11),24-trien-26-oic acid, ganoderic acid X (GAX). Treatment of human hepatoma HuH-7 cells with GAX caused immediate inhibition of DNA synthesis as well as activation of ERK and JNK mitogen-activated protein kinases, and cell apoptosis. Molecular events of apoptosis including degradation of chromosomal DNA, decrease in the level of Bcl-xL, the disruption of mitochondrial membrane, cytosolic release of cytochrome c and activation of caspase-3 were elucidated. The ability of GAX to inhibit topoisomerases and to sensitize the cancer cells toward apoptosis fulfills the feature of a potential anticancer drug.

In some human cancer cases, the activity of p53 is inhibited by over-expressed Mdm2. The Mdm2 acts as an ubiquitin ligase, resulting in p53 ubiquitination and subsequent p53 proteasomal degradation. The disruption of the Mdm2-p53 interaction using small-molecule inhibitors is recognized as a promising strategy for anti-cancer drug design. Mushrooms are an important source of powerful compounds with anti-tumour properties. In this study, the first virtual screening of low molecular weight compounds present in mushroom is presented as potential Mdm2 inhibitors. A re-docking and cross-docking method was used to validate the virtual screening protocol. The steroids: ganoderic acids X (K(i) = 16nM), Y (K(i) = 22nM) and F (K(i) = 69nM); 5,6-epoxy-24(R)-methylcholesta-7,22-dien-3β-ol (K(i) = 74nM) and polyporenic acid C (K(i) = 59nM) stand out as the top ranked potential inhibitors of Mdm2. The docking pose of the most promising compounds were carefully analysed and the information provided shows several interesting starting points for further development of Mdm2 inhibitors.