Antiproliferative Effects of a Triterpene-Enriched Extract from Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes), on Human Lung Cancer Cells.

Ganoderma lucidum, a mushroom that has been used to treat disease in East Asia for centuries, has been shown to be effective against many types of tumors, but the exact cellular mechanism of action is unknown. In this study we examined proliferation of a lung cancer cell line after treatment with 12 concentrations of powdered G. lucidum for 24, 48, and 120 hours. Based on half-maximal inhibitory concentrations values, proliferation of the H1793 cell line seemed to be sensitive to the extract in a time- and dose-dependent manner. We used immunoblot analysis to examine the amounts of cell cycle proteins (cyclin D, Cdk4, and Cdc2) and apoptotic proteins (Bcl-xL and Bax) after treatment with a range of G. lucidum concentrations. Changes in amounts of proteins that regulate the cell cycle were consistent with longer G1 and G2 phases. Proapoptotic protein (Bax) levels increased 6.5-fold, with a commensurate increase in the Bax-to-Bcl ratio, especially at 48 and 120 hours. These results suggest that the decrease in cellular proliferation correlated with a change in both cell cycle progression and apoptosis, and that the triterpenoid in G. lucidum is the bioactive component. Further biochemical characterization of this ancient herbal remedy could hold promise for treating lung cancer.

Auxin and Tryptophan Homeostasis Are Facilitated by the ISS1/VAS1 Aromatic Aminotransferase in Arabidopsis.

Indole-3-acetic acid (IAA) plays a critical role in regulating numerous aspects of plant growth and development. While there is much genetic support for tryptophan-dependent (Trp-D) IAA synthesis pathways, there is little genetic evidence for tryptophan-independent (Trp-I) IAA synthesis pathways. Using Arabidopsis, we identified two mutant alleles of ISS1 ( I: ndole S: evere S: ensitive) that display indole-dependent IAA overproduction phenotypes including leaf epinasty and adventitious rooting. Stable isotope labeling showed that iss1, but not WT, uses primarily Trp-I IAA synthesis when grown on indole-supplemented medium. In contrast, both iss1 and WT use primarily Trp-D IAA synthesis when grown on unsupplemented medium. iss1 seedlings produce 8-fold higher levels of IAA when grown on indole and surprisingly have a 174-fold increase in Trp. These findings indicate that the iss1 mutant's increase in Trp-I IAA synthesis is due to a loss of Trp catabolism. ISS1 was identified as At1g80360, a predicted aromatic aminotransferase, and in vitro and in vivo analysis confirmed this activity. At1g80360 was previously shown to primarily carry out the conversion of indole-3-pyruvic acid to Trp as an IAA homeostatic mechanism in young seedlings. Our results suggest that in addition to this activity, in more mature plants ISS1 has a role in Trp catabolism and possibly in the metabolism of other aromatic amino acids. We postulate that this loss of Trp catabolism impacts the use of Trp-D and/or Trp-I IAA synthesis pathways.