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Hepatocellular carcinoma (HCC)3 is a leading cause of mortality in patients with liver cirrhosis (1). In the United States, the incidence of HCC has risen during the last few decades from 1.3/100,000 population between 1978 and 1980 to 3.3/100,000 population between 1998 and 2001 (2, 3). This is likely to continue, primarily due to progressive liver diseases attributable to the hepatitis C virus in individuals infected a few decades ago (4). However, as hepatitis B virus infection is more prevalent globally than hepatitis C virus, hepatitis B virus remains the single most important cause of HCC worldwide, and is particularly high in Asia and Africa (5). Treatment of HCC is clinically difficult, as HCC expresses multidrug-resistance genes and is insensitive to current chemotherapeutic agents (6). HCC cells are characterized by high cellular levels of cyclin-dependent kinases (Cdks). Up-regulation of Cdks results from the inactivation of p16 Ink4, p21Waf1 and p27 Kip1 , Cdk inhibitory proteins, and abnormal activation of cyclins (7-10). For this reason, Cdk inhibitors are strong candidates for the treatment of HCC, and some (e.g. olomoucine, roscovitine and flavopiridol) have been tested in clinical trials (11).Cdks regulate two biological processes essential for cancer cell survival: cell cycle progression and gene transcription (12). They control entry into each stage of the cell cycle by phosphorylating key substrates such as pRb (13,14). Cdks usually form heterodimers with cyclins to create active complexes and, because cyclin levels oscillate throughout the cell cycle, this contributes to the temporal activation of specific Cdks. Cdks also regulate transcription by phosphorylating the carboxylterminal domain (CTD) of the large subunit of RNA polymerase II (15). In humans, the CTD contains 52 heptapeptide (YSPTSPS) repeats that can be phosphorylated on serines, threonines, and tyrosines (15). A number of Cdks phosphorylate these sites, including Cdk7/cyclin H/Mat1 (part of the TFIIH complex that initiates transcription) (16) and Cdk9/cyclin T (also called P-TEFb), which activates transcriptional elongation (17-21).Mcl-1, an anti-apoptotic member of the Bcl-2 family (22), was first identified as a protein up-regulated in a human carcinoma cell line induced to differentiate along the monocyte lineage (23), and is essential for the survival of carcinoma cells (24 -27). Mcl-1 is thought to act by antagonizing pro-apoptotic proteins such as Bim (28). Inhibitor of apoptosis protein (IAP) is a family of proteins that regulates cell death; X-linked IAP (XIAP) and survivin are two important members of this family in mammals. Both inhibit caspases and block apoptosis (29).Ibulocydine, ((2S,3S,4S,5S)-5-(4-amino-6-bromo-5-carbamoyl-1H-pyrrolo [2,3-d]pyrimidin-1-yl)-3,4-dihydroxytetrahydrofuran-2-yl)methyl isobutyrate, is an isobutyrate ester prodrug of a novel synthetic Cdk inhibitor, BMK-Y101 (4-amino-6-bromo-1-((2S,3S,4S,5S)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-1H-pyrrolo[2,3-d]pyrimidine-5-carboxamide) ...

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Background NAD(P)H:quinone oxidoreductase-1 (NQO1) is a widely-distributed flavin adenine dinucleotide-dependent flavoprotein that promotes obligatory 2-electron reductions of quinones, quinoneimines, nitroaromatics, and azo dyes. This reduces quinone levels and thereby minimizes generation of excess reactive oxygen species (ROS) formed by redox cycling, and concurrent depletion of intracellular thiol pools. Ajoene is derived from crushed garlic. It is formed by a reaction involving two allicin molecules, and is composed of allyl sulfide and vinyl disulfide. Ajoene is present in two isomers, E- and Z-form. Methods Expression of antioxidant enzymes and nuclear factor E2-related factor-2 (Nrf2) was measured by Western blot analysis. NQO1 promoter activity was assessed by the luciferase reporter gene assay. ROS accumulation was monitored by using the fluorescence-generating probe 2′,7′-dichlorofluorescein diacetate. The intracellular glutathione levels were measured by using a commercially available kit. Results Z-ajoene significantly up-regulated the expression of representative antioxidant enzyme NQO1 in non-tumorigenic breast epithelial MCF-10A cells at non-toxic concentrations. Z-ajoene enhanced up-regulation and nuclear translocation of Nrf2, which plays a pivotal role in the induction of many genes encoding antioxidant enzymes and other cytoprotective proteins. Z-ajoene treatment also increased the activity of nqo1 -promoter harboring antioxidant response element consensus sequences in MCF-10A cells. Silencing of Nrf2 by small interfering RNA abrogated ajoene-induced expression of NQO1. Z-ajoene activated extracellular signal-regulated kinase (ERK). Inhibition of ERK activation by U0126 abrogated ability of Z-ajoene to activate Nrf2 and to induce NQO1 expression. Intracellular ROS accumulation was observed after treatment with Z-ajoene, whereas the E-isoform was not effective. The inhibition of ROS by treatment with N-acetylcysteine, a radical scavenger, abrogated Z-ajoene-induced expression of NQO1 as well as activation of ERK and Nrf2, suggesting that Z-ajoene augments the Nrf2-dependent antioxidant defense via ROS generation and ERK activation. Conclusions Z-ajoene induces NQO1 expression in MCF-10A cells through ROS-mediated activation of Nrf2.