Ahmad Barghash

Fatty Acid Elongation in Non-Alcoholic Steatohepatitis and Hepatocellular Carcinoma

Non-alcoholic steatohepatitis (NASH) represents a risk factor for the development of hepatocellular carcinoma (HCC) and is characterized by quantitative and qualitative changes in hepatic lipids. Since elongation of fatty acids from C16 to C18 has recently been reported to promote both hepatic lipid accumulation and inflammation we aimed to investigate whether a frequently used mouse NASH model reflects this clinically relevant feature and whether C16 to C18 elongation can be observed in HCC development. Feeding mice a methionine and choline deficient diet to model NASH not only increased total hepatic fatty acids and cholesterol, but also distinctly elevated the C18/C16 ratio, which was not changed in a model of simple steatosis (ob/ob mice). Depletion of Kupffer cells abrogated both quantitative and qualitative methionine-and-choline deficient (MCD)-induced alterations in hepatic lipids. Interestingly, mimicking inflammatory events in early hepatocarcinogenesis by diethylnitrosamine-induced carcinogenesis (48 h) increased hepatic lipids and the C18/C16 ratio. Analyses of human liver samples from patients with NASH or NASH-related HCC showed an elevated expression of the elongase ELOVL6, which is responsible for the elongation of C16 fatty acids. Taken together, our findings suggest a detrimental role of an altered fatty acid pattern in the progression of NASH-related liver disease.

Hepatic hepcidin expression is decreased in cirrhosis and HCC

et al. Expression of iron regulatory genes in a rat model of hepatocellular carcinoma. Liver Int 2006;26:976–985. [4] Youn P, Kim S, Ahn JH, Kim Y, Park JD, Ryu DY. Regulation of iron metabolism-related genes in diethylnitrosamine-induced mouse liver tumors. Toxicol Lett 2009;184:151–158. [5] Roessler S, Jia H-L, Budhu A, Forgues M, Ye Q-H, Lee J-S, et al. A unique metastasis gene signature enables prediction of tumor relapse in early-stage hepatocellular carcinoma patients. Cancer Res 2010;70:10202–10212. [6] Kijima H, Sawada T, Tomosugi N, Kubota K. Expression of hepcidin mRNA is uniformly suppressed in hepatocellular carcinoma. BMC Cancer 2008;8:167–175. [7] Girelli D, Pasino M, Goodnough JB, Nemeth E, Guido M, Castagna A, et al. Reduced serum hepcidin levels in patients with chronic hepatitis C. J Hepatol 2009;51:845–852. [8] Miura K, Taura K, Kodama Y, Schnabl B, Brenner DA. Hepatitis C virusinduced oxidative stress suppresses hepcidin expression through increased histone deacetylase activity. Hepatology 2008;48:1420–1429. [9] Weizer-Stern O, Adamsky K, Margalit O, Ashur-Fabian O, Givol D, Amariglio N, et al. Hepcidin, a key regulator of iron metabolism, is transcriptionally activated by p53. Br J Haematol 2007;138:253–262. [10] Nault J-C, Zucman-Rossi J. Genetics of hepatocellular carcinoma: the next generation. J Hepatol 2014;60:224–226.

Lipid Metabolism Signatures in NASH-Associated HCC—Letter

An article published recently in Cancer Research elegantly performed lipidomic and gene expression analyses in a murine model of nonalcoholic steatohepatitis (NASH)–associated hepatocellular carcinoma (HCC) and compared the findings with serum samples from patients with fibrosis and HCC ([1][1

IMP2/p62 induces genomic instability and an aggressive hepatocellular carcinoma phenotype

Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related deaths and commonly develops in inflammatory environments. The IGF2 mRNA-binding protein IMP2-2/IGF2BP2-2/p62 was originally identified as an autoantigen in HCC. Aim of this study was to investigate a potential pathophysiological role of p62 in hepatocarcinogenesis. Human HCC tissue showed overexpression of IMP2, which strongly correlated with the fetal markers AFP and DLK1/Pref-1/FA-1 and was particularly elevated in tumors with stem-like features and hypervascularization. Molecular classification of IMP2-overexpressing tumors revealed an aggressive phenotype. Livers of mice overexpressing the IMP2 splice variant p62 highly expressed the stem cell marker DLK1 and secreted DLK1 into the blood. p62 was oncogenic: diethylnitrosamine (DEN)-treated p62 transgenic mice exhibited a higher tumor incidence and multiplicity than wild types. Tumors of transgenics showed a more aggressive and stem-like phenotype and displayed more oncogenic chromosomal aberrations determined with aCGH analysis. DEN-treated p62 transgenic mice exhibited distinct signs of inflammation, such as inflammatory cytokine expression and oxidative stress markers, that is, thiobarbituric acid-reactive substance (TBARS) levels. Reactive oxygen species (ROS) production was elevated in HepG2 cells, which either overexpressed p62 or were treated with DLK1. p62 induced this ROS production by a DLK1-dependent induction and activation of the small Rho-GTPase RAC1, activating NADPH oxidase and being overexpressed in human HCC. Our data indicate that p62/IMP2 promotes hepatocarcinogenesis by an amplification of inflammation.

Transferring functional annotations of membrane transporters on the basis of sequence similarity and sequence motifs

BackgroundMembrane transporters catalyze the transport of small solute molecules across biological barriers such as lipid bilayer membranes. Experimental identification of the transported substrates is very tedious. Once a particular transport mechanism has been identified in one organism, it is thus highly desirable to transfer this information to related transporter sequences in different organisms based on bioinformatics evidence.ResultsWe present a thorough benchmark at which level of sequence identity membrane transporters from Escherichia coli, Saccharomyces cerevisiae, and Arabidopsis thaliana belong to the same families of the Transporter Classification (TC) system, and at what level these membrane transporters mediate the transport of the same substrate. We found that two membrane transporter sequences from different organisms that are aligned with normalized BLAST expectation value better than E-value 1e-8 are highly likely to belong to the same TC family (F-measure around 90%). Enriched sequence motifs identified by MEME at thresholds below 1e-12 support accurate classification into TC families for about two thirds of the sequences (F-measure 80% and higher). For the comparison of transported substrates, we focused on the four largest substrate classes of amino acids, sugars, metal ions, and phosphate. At similar identity thresholds, the nature of the transported substrates was more divergent (F-measure 40 - 75% at the same thresholds) than the TC family membership.ConclusionsWe suggest an acceptable threshold of 1e-8 for BLAST and HMMER where at least three quarters of the sequences are classified according to the TC system with a reasonably high accuracy. Researchers who wish to apply these thresholds in their studies should multiply these thresholds by the size of the database they search against. Our findings should be useful to those who wish to transfer transporter functional annotations across species.

Overexpression of IGF2 mRNA-Binding Protein 2 (IMP2/p62) as a Feature of Basal-like Breast Cancer Correlates with Short Survival.

To the Editor: Recent evidence published in this journal suggested that autoantibodies against IMP2/p62 may be useful serum biomarkers for early-stage breast cancer screening and diagnosis [1]. The study by Liu et al. [1] elegantly demonstrated that the frequency of autoantibodies against IMP2 and IMP2 expression itself is significantly increased in breast tumour tissues compared to normal tissues. An autoimmune response to IMP2/p62 is also known for other tumours, for example colon carcinoma and hepatocellular carcinoma (HCC) [2, 3]. To test the relevance of IMP2 expression for prognosis in breast cancer, we analysed a large human Gene Omnibus (GEO) data set (GSE42568 [4]). Interestingly, high IMP2 expression correlated with short survival (Fig. 1A). Therefore, IMP2 expression could serve not only as a diagnostic but also as a prognostic biomarker. It is well known that there are different classes of human breast tumours, which are characterized by different molecular patterns [5]. Luminal cancers are the most common subtype. The basal-like subtype, which mostly corresponds to the triple-negative subtype, stands for about 20% of breast cancer cases with a shorter survival than the luminal subtype [6]. To test whether IMP2 expression might be a feature of a specific breast cancer subtype, we analysed an additional human data set, which provided subtype-classified samples (GDS1329 [7]). IMP2 was especially elevated in tissues of basal-like cancer compared to the luminal or apocrine subtype (Fig. 1B). The overexpression of IMP2 was confirmed in another set of basal-like breast cancer tissues (GDS2250 [8]) compared to non-basal-like samples and normal tissues (Fig. 1C). In conclusion, detection of IMP2/p62 expression in breast cancer presented by Liu and colleagues [1] might

Elevated expression of the IGF2 mRNA binding protein 2 (IGF2BP2/IMP2) is linked to short survival and metastasis in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) represents the sixth leading cause of cancer-related deaths and develops in Barrets esophagus affected tissues. The IGF2 mRNA binding protein IMP2/IGF2BP2/p62 was originally identified as an autoantigen in hepatocellular carcinoma. Aim of this study was to investigate the expression and prognostic role of IMP2 in EAC. Human EAC and Barrets esophagus tissue showed overexpression of IMP2, particularly in tumors of increased size and in metastatic tissues. Molecular classification based on published gene signatures of esophageal cancer revealed a specific subtype, in which the expression of IMP2 is high. According to GO and KEGG pathway analyses, genes showing highly correlated expression with IMP2 are associated with growth, proliferation, metabolism, inflammation, and cancerous processes. Clustering of EAC samples according to published survival marker genes strongly suggests that IMP2 overexpressing samples show poor survival. Finally, IMP2 expression correlated with short survival in patients with EAC or esophageal squamous carcinoma. Our data indicate that IMP2 might be a useful prognostic marker for Barrets esophagus and EAC.