Sustained activation of extracellular signal-regulated kinase (ERK) has been detected previously in numerous tumors in the absence of RAS-activating mutations. However, the molecular mechanisms responsible for ERK-unrestrained activity independent of RAS mutations remain unknown. Here, we evaluated the effects of the functional interactions of ERK proteins with dual-specificity phosphatase 1 (DUSP1), a specific inhibitor of ERK, and S-phase kinase-associated protein 2 (SKP2)/ CDC28 protein kinase 1b (CKS1) ubiquitin ligase complex in human hepatocellular carcinoma (HCC). Levels of DUSP1, as assessed by real-time reverse transcription-PCR and Western blot analysis, were significantly higher in tumors with better prognosis (as defined by the length of patients' survival) when compared with both normal and nontumorous surrounding livers, whereas DUSP1 protein expression sharply declined in all HCC with poorer prognosis. In the latter HCC subtype, DUSP1 inactivation was due to either ERK/SKP2/CKS1-dependent ubiquitination or promoter hypermethylation associated with loss of heterozygosity at the DUSP1 locus. Noticeably, expression levels of DUSP1 inversely correlated with those of activated ERK, as well as with proliferation index and microvessel density, and directly with apoptosis and survival rate. Subsequent functional studies revealed that DUSP1 reactivation led to suppression of ERK, CKS1, and SKP2 activity, inhibition of proliferation and induction of apoptosis in human hepatoma cell lines. Taken together, the present data indicate that ERK achieves unrestrained activity during HCC progression by triggering ubiquitin-mediated proteolysis of its specific inhibitor DUSP1. Thus, DUSP1 may represent a valuable prognostic marker and ERK, CKS1, or SKP2 potential therapeutic targets for human HCC.

Mounting evidence underlines the role of genomic hypomethylation in the generation of genomic instability (GI) and tumorigenesis, but whether DNA hypomethylation is required for hepatocellular carcinoma (HCC) development and progression remains unclear. We investigated the correlation between GI and DNA methylation, and influence of methionine metabolism deregulation on these parameters and hepatocarcinogenesis in c-Myc and cMyc/Tgf-a transgenic mice and human HCCs. S-adenosyl-L-methionine/S-adenosylhomocysteine ratio and liver-specific methionine adenosyltransferase (MatI/III) progressively decreased in dysplastic and neoplastic liver lesions developed in c-Myc transgenic mice and in human HCC with better (HCCB) and poorer (HCCP) prognosis (based on patient's survival length). Deregulation of these parameters resulted in a rise of global DNA hypomethylation both in c-Myc and human liver lesions, positively correlated with GI levels in mice and humans, and inversely correlated with the length of survival of HCC patients. No changes in MATI/ III and DNA methylation occurred in c-Myc/Tgf-a lesions and in a small human HCC subgroup with intermediate prognosis, where a proliferative activity similar to that of c-Myc HCC and HCCB was associated with low apoptosis. Upregulation of genes involved in polyamine synthesis, methionine salvage and downregulation of polyamine negative regulator OAZ1, was highest in c-Myc/Tgf-a HCCs and HCCP. Our results indicate that alterations in the activity of MAT/I/III, and extent of DNA hypomethylation and GI are prognostic markers for human HCC. However, a small human HCC subgroup, as c-Myc/Tgf-a tumors, may develop in the absence of alterations in DNA methylation. ' 2007 Wiley-Liss, Inc.Key words: DNA hypomethylation; hepatocellular carcinoma; genomic instability; prognosis; transgenic mice Hepatocellular carcinoma (HCC), is the fifth most frequent human cancer, with the highest frequency in sub-Saharan Africa and far eastern Asia, where hepatitis B virus and hepatitis C virus infections are endemic and food is contaminated by Aflatoxin B1. 1 HCC incidence is rising in Europe and United States, presumably due to increased incidence of hepatitis C virus infection, cirrhosis related to Type II diabetes, and alcoholic hepatitis.2 HCC is rapidly fatal, since most patients at risk are not diagnosed in time and amenable to potentially curative treatments, i.e., partial liver resection or transplantation. 1,2 Hepatocarcinogenesis is characterized by the accumulation of various alterations in oncogenes and oncosuppressor genes.3 This event is presumably due to the increased tendency of initiated cells to acquire mutations following dysregulation of the mechanisms preserving genome integrity, a condition known as genomic instability 4 (GI). Indeed, a number of studies have demonstrated the progressive appearance of GI, such as point mutations, loss of heterozygosity and chromosomal alterations from preneoplastic liver to HCC.5 In addition, microsatellite instability occurs in HCC, although l...

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In the cure of cancer, a major cause of today's mortality, chemotherapy is the most common treatment, though serious frequent challenges are encountered by current anticancer drugs. We discovered that few-layer graphene (FLG) dispersions have a specific killer action on monocytes, showing neither toxic nor activation effects on other immune cells. We confirmed the therapeutic application of graphene on an aggressive type of cancer that is myelomonocytic leukemia, where the monocytes are in their malignant form. We demonstrated that graphene has the unique ability to target and boost specifically the necrosis of monocytic cancer cells. Moreover, the comparison between FLG and a common chemotherapeutic drug, etoposide, confirmed the higher specificity and toxicity of FLG. Since current chemotherapy treatments of leukemia still cause serious problems, these findings open the way to new and safer therapeutic approaches.

Although artemisinin-based combination therapies (ACTs) treat Plasmodium falciparum malaria effectively throughout most of the world, the recent expansion of ACT-resistant strains in some countries of the Greater Mekong Subregion (GMS) further increased the interest in improving the effectiveness of treatment and counteracting resistance. Recognizing that (1) partially denatured hemoglobin containing reactive iron (hemichromes) is generated in parasitized red blood cells (pRBC) by oxidative stress, (2) redox-active hemichromes have the potential to enhance oxidative stress triggered by the parasite and the activation of artemisinin to its pharmaceutically active form, and (3) Syk kinase inhibitors block the release of membrane microparticles containing hemichromes, we hypothesized that increasing hemichrome content in parasitized erythrocytes through the inhibition of Syk kinase might trigger a virtuous cycle involving the activation of artemisinin, the enhancement of oxidative stress elicited by activated artemisinin, and a further increase in hemichrome production. We demonstrate here that artemisinin indeed augments oxidative stress within parasitized RBCs and that Syk kinase inhibitors further increase iron-dependent oxidative stress, synergizing with artemisinin in killing the parasite. We then demonstrate that Syk kinase inhibitors achieve this oxidative enhancement by preventing parasite-induced release of erythrocyte-derived microparticles containing redox-active hemichromes. We also observe that Syk kinase inhibitors do not promote oxidative toxicity to healthy RBCs as they do not produce appreciable amounts of hemichromes. Since some Syk kinase inhibitors can be taken daily with minimal side effects, we propose that Syk kinase inhibitors could evidently contribute to the potentiation of ACTs.