Co., Ltd., Sapporo, Japan, and by Aureo Co., Ltd., Tokyo, Japan. There are no other patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLoS ONE policies on Cyanidin 3-O-glucoside chloride site sharing data and materials. of organisms, such as mushrooms, yeasts, and fungi, are believed to exhibit a variety of beneficial effects. Due to this, these -glucans are commercially available and consumed as food supplements. Among the various proposed efficacies, the most prominent effect of -glucans would be its anti-tumor activity. Actually, several anti-tumor drugs containing -glucan as the main compound, such as Krestin, Picibanil, Lentinan, and Sizofiran, have been developed and are used in the treatment of cancers. Although, in principle, these -glucanbased drugs are used in combination with other chemical anti-tumor drugs, it has been demonstrated that -glucans enhance the anti-tumor activity of chemical anti-tumor drugs through the activation of immunity to eliminate tumor cells in clinical trials. Black yeast, Aureobasidium Pullulans produces a water soluble -glucan in growth medium under certain conditions. AP-PG is characterized by being more highly branched with –D-glycosidic linked glucose residues than -glucans derived from other organisms. PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19776382 Overall, the effects of AP-PG in mammals are assumed to be the same as those of -glucans derived from other organisms, and actually, anti-tumor, anti-allergy, and antiinfectious disease effects of AP-PG have been identified under experimental conditions. It is speculated that the induction of apoptosis of tumor cells plays an important role 
in the anti-tumor activity of -glucan. Apoptosis is classified as type I programmed cell death, and is characterized by morphological changes such as cell shrinkage, chromatin condensation, and DNA fragmentation. Apoptosis is an important physiological mechanism to remove injurious cells from the body. Therefore, strategies for induction of apoptosis specific to tumor cells are thought to be important in the development of anti-cancer drugs. Several extracellular cytokines are related to the transmission of cell signals for induction of apoptosis, and especially, death ligands belonging to the tumor necrosis factor superfamily are assumed to be central to the signal transduction for apoptosis induction. Here, TNF-, FasL, and TRAIL are well known death ligands, and TRAIL, the most recently identified molecule among these ligands, is thought to be crucial for the tumor killing. As PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19778700 TRAIL has been identified as an apoptosis inducing ligand which specifically induces apoptosis to transformed cells but not to normal cells, there have been attempts to develop novel drugs utilizing the characteristics of TRAIL. The aim of this study is to propose a possible mechanism on the anti-tumor activity of AP-PG. This report shows that stimulation with AP-PG has the potential to induce TRAILdependent apoptosis through an activation of the TRAIL expression in macrophages. Stimulation with AP-PG induces TRAIL in mouse and human macrophage-like cell lines, RAW264.7 cells, MONO MAC 6 cells, and macrophage-differentiated THP-1 cells. The induction activity of TRAIL by AP-PG was compared with curdlan, a bacterial -glucan. The results show that both curdlan and AP-PG similarly induce TRAIL expression in RAW264.7, whereas TRAIL induction activity with curdlan in macrophage-differentiated THP-1 cells is apparently weaker than that with AP-PG. In additio
