Gene induction by glycyrol to apoptosis through endonuclease G in tumor cells and prediction of oncogene function by microarray analysis

Glycyrrhiza uralensis (Leguminosae) has long been known as an antiinflammatory agent for gastric ulcers, arthritis, and rheumatism. The flavonoid glycyrol (GC) (10 μg/ml) isolated from G. uralensis dramatically inhibits phorbol ester (phorbol 12-myristate 13-acetate)-induced nuclear factor (NF)-κB-dependent transcriptional activity, as determined by luciferase reporter activity in human kidney epithelial 293T cells. To investigate global gene expression profiling in cells by GC, we performed high-density oligonucleotide microarrays. Our microarray analyses showed that GC inhibited phorbol ester-induced NF-κB-dependent transcriptional activity in inflammatory-related gene expression. RT-PCR analysis, based on microarray data, showed that NF-κB-dependent genes (such as CCL2, CCL7, CD44, and HSPB8 in addition to NF-κB itself) were significantly downregulated by GC. Treatment with GC (10 μg/ml) inhibited I-κB degradation induced by phorbol 12-myristate 13-acetate. The microarray data also suggested that GC induces gene expression to p53-dependent apoptosis through endonuclease G, instead of CAD/DFF and AIF/PDCD8, as a downstream-apoptosis factor in human kidney epithelial 293T tumor cells, and induces oncogenes with a suppressor role as an added function.