After oral administration, parent ginseng compounds were biotransformed to Rg3 and PPD in the gut before absorption. Recently, it was observed that the p53-DR5 crosstalk regulatory network might contribute to the induced ATR inhibitor apoptosis by ginsenoside Rg3 in hepatoma cells (48). Consistent with these studies, our data suggested that PPD-induced colon cancer cell apoptosis

is partially mediated by the regulation of crosstalk of the p53-DR4/DR5 interaction, a TRAIL pathway. PPD may have potential in preventing colorectal tumorigenesis and treating CRC alone or in combination with other chemotherapeutic agents (26). In summary, the present study demonstrated that PPD possessed significant antitumor effects in an in vivo model. Human colorectal cancer

lines, especially HTC-116 cells, are highly sensitive to the growth inhibition by PPD. The effects of the compound are associated with G1 cell cycle arrest and induction of apoptosis. Microarray analysis showed that PPD inhibited CRC cell growth by activation of a cluster of gene expression, including oncogenes as well as tumor suppressors. Our data suggested that by regulating the interactions between p53 and DR4/DR5, the TRAIL pathway played an important role in PPD’s CRC inhibition. The logical next step for TRAIL apoptotic pathway verification should be employing western blot or immunostaining to evaluate expressions of the key target regulators. These observations should lead check details to the marker identifications that reflect the responsiveness of colon tumor to PPD treatment. The authors report no conflict of interest. This work was supported in part by the grants of NIH/National Center for Complementary and Alternative MedicineAT004418 and AT005362, NIH/National Institute of General Medical

Sciences074197 and 5P30DK042086, Metalloexopeptidase NIH/National Cancer InstituteCA149275, and U.S. Department of DefenseW81XWH-10-1-0077 “
“Nitric oxide (NO) plays a crucial role in maintaining homeostasis (1), (2), (3) and (4). NO is synthesized from its precursor L-arginine by a family of NO synthases (NOSs) that include neuronal (nNOS), inducible (iNOS), and endothelial NOS (eNOS). It was initially reported that nNOS and eNOS are constitutively expressed mainly in the nervous system and the vascular endothelium, respectively, synthesizing a small amount of NO in a calcium-dependent manner under basal conditions and upon stimulation, and that iNOS is induced only when stimulated by microbial endotoxins or certain proinflammatory cytokines, producing a greater amount of NO in a calcium-independent manner (3) and (4). However, recent studies have revealed that nNOS and eNOS are also subject to expressional regulation (5), (6), (7), (8) and (9), and that iNOS is expressed even under physiological conditions (10) and (11). Thus, it has become evident that all three NOS isoforms are expressed under both physiological and pathological conditions (10) and (12).