Epithelioid glioblastoma (eGBM) and pleomorphic xanthoastrocytoma (PXA) with anaplastically transformed foci (ePXA) show overlapping features. Eleven eGBMs and 5 ePXAs were reviewed and studied immunohistochemically. Fluorescence in situ hybridization for EGFR amplification, PTEN deletion and ODZ3 deletion was also performed, with Ilumina 450 methylome analysis obtained in five cases. The average age for eGBM was 30.9 (range 2-79) years, including five pediatric cases and a M : F ratio of 4.5. The ePXA patients had a M : F ratio of 4 and averaged 21.2 (range 10-38) years in age, including two pediatric cases. Six eGBMs and two ePXAs recurred (median recurrence interval of 12 and 3.3 months, respectively). All tumors were composed of solid sheets of loosely cohesive, "melanoma-like" cells with only limited infiltration. ePXAs showed lower grade foci with classic features of PXA. Both tumor types showed focal expression of epithelial and glial markers, retained INI1 and BRG1 expression, occasional CD34 positivity, and lack of mutant IDH1 (R132H) immunoreactivity. BRAF V600E mutation was present in four eGBMs and four ePXAs. ODZ3 deletion was detected in seven eGBMs and two ePXAs. EGFR amplification was absent. Methylome analysis showed that one ePXA and one eGBM clustered with PXAs, one eGBM clustered with low-grade gliomas, and two eGBMs clustered with pediatric-type glioblastomas. Common histologic, immunohistochemical, molecular and clinical features found in eGBM and ePXA suggest that they are closely related or the same entity. If the latter is true, the nomenclature and WHO grading remains to be resolved.

Abstract-C57BL/6J mice are susceptible to atherosclerosis when fed a diet consisting of fat, cholesterol, and taurocholate.The susceptibility to diet-induced atherosclerosis is linked to a reduction in plasma high density lipoprotein (HDL). Diet-induced reduction of plasma HDL shows a physiological and a genetic correlation with repression of cholesterol-7-␣-hydroxylase, the liver-specific enzyme that regulates the conversion of cholesterol into bile acids. To examine the hypothesis that the repression of cholesterol-7-␣-hydroxylase is responsible for initiating the metabolic alterations leading to the formation of atherosclerosis and gallstones, we determined whether constitutive transgenic expression of cholesterol-7-␣-hydroxylase in C57BL/6J mice would confer resistance to these 2 common human diseases. When fed the atherogenic diet, nontransgenic littermates, but not cholesterol-7-␣-hydroxylase transgenic mice, accumulated cholesterol and cholesterol esters in their livers and plasma. Although the atherogenic diet caused a marked decrease in plasma HDL cholesterol in nontransgenic mice, HDL levels in transgenic mice remained relatively unchanged. Moreover, the ability of cholesterol-7-␣-hydroxylase transgenic mice to maintain cholesterol and lipoprotein homeostasis completely prevented the formation of atherosclerosis and gallstones. These data establish the integral role that cholesterol-7-␣-hydroxylase has in maintaining hepatic cholesterol homeostasis and, thus, in the susceptibility to the formation of gallstones and atherosclerosis.

Stable plasmid-driven expression of the liver-specific gene product cholesterol 7␣-hydroxylase (7␣-hydroxylase) was used to alter the cellular content of transcriptionally active sterol response element binding protein 1 (SREBP1). As a result of stable expression of 7␣-hydroxylase, individual single cell clones expressed varying amounts of mature SREBP1 protein. These single cell clones provided an opportunity to identify SREBP1-regulated genes that may influence the assembly and secretion of apoB-containing lipoproteins. Our results show that in McArdle rat hepatoma cells, which normally do not express 7␣-hydroxylase, plasmid-driven expression of 7␣-hydroxylase results in the following: 1) a linear relationship between (i) the cellular content of mature SREBP1 and 7␣-hydroxylase protein, (ii) the relative expression of 7␣-hydroxylase mRNA and the mRNA's encoding the enzymes regulating fatty acid, i.e. acetylCoA carboxylase and sterol synthesis, i.e. HMG-CoA reductase, (iii) the relative expression of 7␣-hydroxylase mRNA and microsomal triglyceride transfer protein mRNA, a gene product that is essential for the assembly and secretion of apoB-containing lipoproteins; 2) increased synthesis of all lipoprotein lipids (cholesterol, cholesterol esters, triglycerides, and phospholipids); and 3) increased secretion of apoB100 without any change in apoB mRNA. Cells expressing 7␣-hydroxylase contained significantly less cholesterol (both free and esterified). The increased cellular content of mature SREBP1 and increased secretion of apoB100 were concomitantly reversed by 25-hydroxycholesterol, suggesting that the content of mature SREBP1, known to be decreased by 25-hydroxycholesterol, mediates the changes in the lipoprotein assembly and secretion pathway that are caused by 7␣-hydroxylase. These data suggest that several steps in the assembly and secretion of apoB-containing lipoproteins by McArdle hepatoma cells may be coordinately linked through the cellular content of mature SREBP1.Apolipoprotein B100 (apoB) 1 is an unusually large (Ͼ500 kDa) amphipathic protein responsible for the assembly and secretion of plasma lipoproteins by the liver and intestine (reviewed in Refs. 1-3). Its concentration in plasma, as a component of LDL, is a major determinant of susceptibility to the development of atherosclerotic cardiovascular disease (4, 5). Hepatic derived apoB100-containing lipoproteins are the precursors of plasma LDL (6). Hepatic assembly and secretion of apoB-containing lipoproteins require an orchestration of many seemingly independent processes as follows: 1) the production of component lipids (cholesterol, cholesterol esters, triglycerides, and phospholipids); 2) the synthesis of apoB, a uniquely large polypeptide containing multiple amphipathic structural domains that irreversibly associate with phospholipids (7); 3) translocation across the endoplasmic reticulum that requires an intralumenal protein complex consisting of MTP and PDI (8); and 4) the assembly of VLDL particle within the endoplasmic reticulum (1, ...

Sustained virologic response (SVR) after direct‐acting antiviral (DAA) therapy for chronic hepatitis C results in significant decreases in liver stiffness measured by transient elastography (TE). The aim of this study was to clarify if TE can guide post‐SVR management in patients with advanced fibrosis or cirrhosis prior to treatment as current guidelines are unclear on the role of TE after SVR. In total, 84 patients with hepatitis C virus and advanced fibrosis or cirrhosis and from a single center underwent DAA treatment and achieved SVR. Overall, 62% had improved liver stiffness that was consistent with regression of at least one stage of fibrosis. In the cirrhosis group, 48% showed fibrosis regression by at least two stages by TE (<9.5 kPa). In the F3 fibrosis group, 39% regressed by at least two stages (<7 kPa). The median time from SVR to regression by TE was 1 year. Fifteen patients with liver biopsies prior to SVR underwent a biopsy after SVR; 13 of these patients had improved liver stiffness (to <9.5 kPa). The post‐SVR liver biopsies of only 4 patients showed F1‐F2 while 11 patients showed F3‐F4; however, morphometry of the first 11 biopsied patients revealed that 10 patients had an average 46% decrease in collagen content. Conclusion: This is the first DAA study that also has paired liver biopsies showing fibrosis regression. After SVR is achieved, improvements in liver stiffness measured by TE are seen in a majority of patients with advanced fibrosis/cirrhosis within 2 years. TE improvements are overstated when compared to histologic staging but confirmed with morphometric analysis. It is unclear whether TE following SVR can reliably predict when patients no longer require advanced fibrosis/cirrhosis monitoring after SVR.

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In this study, we explored how sterol metabolism altered by the expression of cholesterol-7␣-hydroxylase NADPH:oxygen oxidoreductase (7␣-hydroxylase) affects the ubiquitin-dependent proteasome degradation of translocation-arrested apoB53 in Chinese hamster ovary cells. Stable expression of two different plasmids that encode either rat or human 7␣-hydroxylase inhibited the ubiquitin conjugation of apoB and its subsequent degradation by the proteasome. Oxysterols (25-hydroxycholesterol and 7-ketocholesterol) reversed the inhibition of apoB degradation caused by 7␣-hydroxylase. The combined results suggest that the normally rapid proteasome degradation of translocation-arrested apoB can be regulated by a sterol-sensitive polyubiquitin conjugation step in the endoplasmic reticulum. Blocked ubiquitin-dependent proteasome degradation caused translocation-arrested apoB to become sequestered in segregated membrane domains. Our results described for the first time a novel mechanism through which the "quality control" proteasome endoplasmic reticulum degradative pathway of translocation-arrested apoB is linked to sterol metabolism. Sterol-sensitive blocked ubiquitin conjugation appears to selectively inhibit the proteasome degradation of apoB, but not 7␣-hydroxylase protein, with no impairment of cell vitality or function. Our findings may help to explain why the hepatic production of lipoproteins is increased when familial hypertriglyceridemic patients are treated with drugs that activate 7␣-hydroxylase (e.g. bile acid-binding resins).ApoB is the major structural protein responsible for the assembly of lipoproteins by the liver and intestine. Multiple forms of apoB, designated as the percentage of the N terminus of the largest secretory product apoB100 (4536 amino acids), are produced from a single gene transcript by mRNA editing and proteolytic cleavage (reviewed in Refs. 1-3). Overproduction of apoB-containing lipoproteins by the liver is responsible for familial combined hyperlipidemia (4). In addition, overproduction of triglyceride-rich lipoproteins is responsible for the human disease familial hypertriglyceridemia (5). In these patients, the secretion of triglyceride-rich lipoproteins varies in parallel with the rate of bile acid synthesis (6 -8). These findings suggest that the secretion of very low density lipoprotein triglyceride is linked to hepatic sterol metabolism via an as yet undefined mechanism that is dependent upon genes that contribute to hypertriglyceridemia.The rate of hepatic secretion of apoB is regulated post-transcriptionally. Only a portion of de novo synthesized apoB is secreted; the remaining portion is degraded intracellularly (9). Interruption of apoB translocation is one of several criteria that lead to increased intracellular degradation (reviewed in Ref. 10). Both translocation and lipid addition require the presence of microsomal triglyceride transfer protein (MTP) 1 in the ER (11-13). MTP exists in the ER lumen as a heterodimer with protein-disulfide isomerase (reviewed in Ref. 14). I...

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Due to the absence of microsomal triglyceride transfer protein (MTP), Chinese hamster ovary (CHO) cells lack the ability to translocate apoB into the lumen of the endoplasmic reticulum, causing apoB to be rapidly degraded by an N-acetyl-leucyl-leucyl-norleucinal-inhibitable process. The goal of this study was to examine if expression of MTP, whose genetic deletion is responsible for the human recessive disorder abetalipoproteinemia, would recapitulate the lipoprotein assembly pathway in CHO cells. Unexpectedly, expression of MTP mRNA and protein in CHO cells did not allow apoBcontaining lipoproteins to be assembled and secreted by CHO cells expressing apoB53. Although expression of MTP in cells allowed apoB to completely enter the endoplasmic reticulum, it was degraded by a proteolytic process that was inhibited by dithiothreitol (1 mM) and chloroquine (100 M), but resistant to N-acetyl-leucylleucyl-norleucinal. In marked contrast, coexpression of the liver-specific gene product cholesterol 7␣-hydroxylase with MTP resulted in levels of MTP lipid transfer activity that were similar to those in mouse liver and allowed intact apoB53 to be secreted as a lipoprotein particle. These data suggest that, although MTP-facilitated lipid transport is not required for apoB translocation, it is required for the secretion of apoB-containing lipoproteins. We propose that, in CHO cells, MTP plays two roles in the assembly and secretion of apoB-containing lipoproteins: 1) it acts as a chaperone that facilitates apoB53 translocation, and 2) its lipid transfer activity allows apoB-containing lipoproteins to be assembled and secreted. Our results suggest that the phenotype of the cell (e.g. expression of cholesterol 7␣-hydroxylase by the liver) may profoundly influence the metabolic relationships determining how apoB is processed into lipoproteins and/or degraded.The assembly and secretion of lipoproteins containing apoB occur in several tissues (liver, intestine, yolk sac, and heart) and are essential for the transport and delivery of fat during development and in the adult (reviewed in Refs. 1-4). There are at least three distinct human familial disorders associated with developmental and nutritional abnormalities caused by the inability of the liver and/or intestine to assemble and secrete apoB-containing lipoproteins (5). Hypobetalipoproteinemia is caused by mutations of the apoB gene leading to forms that are incapable of forming lipoprotein particles and/or to impaired synthesis of apoB by the liver and intestine (1, 6). The expression of human hypobetalipoproteinemic apoB genes in mice recapitulates many of the phenotypic abnormalities observed in human (7,8). Abetalipoproteinemia is caused by mutations in the MTP 1 gene (9 -12). The absence of MTP lipid transfer activity in the lumen of the endoplasmic reticulum (ER) causes apoB to be degraded rather than secreted as a lipoprotein particle by the liver and intestine (12, 13). The recent demonstration that inactivation of a single allele of the MTP gene in mice causes signifi...