Interaction of LNA oligonucleotides with mdr1 promoter

LNA oligonucleotides [1] can be used for targeting to double stranded DNA by the "strand invasion" mechanism. We used affinity modification by reactive oligonucleotide conjugates for investigation of oligonucleotides interaction with structured DNA. The tested LNAs and oligonucleotides of the same sequence were assayed as anti-mdr1 drugs in different cell cultures. One of the oligos, LNA79 strongly inhibited mdr1 induction in Hela cells and totally prevented activation of mdr1 in K-562.     

Inhibition of PPARα/RXRα-mediated direct hyperplasia pathways during griseofulvin-induced hepatocarcinogenesis

Chronic griseofulvin (GF) feeding induces preneoplastic foci followed by hepatocellular carcinoma in the mouse liver. Our previous study suggested that GF-induced hepatocellular proliferation had a different mechanism from that of peroxisome proliferator (PP)–induced direct hyperplasia. The GF-induced hepatocellular proliferation was mediated through activation of immediate early genes such as Fos, Jun, Myc, and NFκB. In contrast, PP-induced direct hyperplasia does not involve activation of any of these immediate early genes. It has been shown that nuclear hormone receptors including peroxisome proliferator activated receptors (PPARs) and retinoid x receptors (RXRs) play important roles in mediating the pleiotropic effects of PPs. To examine the possible roles of PPARs and RXRs during non-PP-induced hepatocellular proliferation and the interaction between PP and non-PP-induced proliferation, we have studied the expression of the PPAR and RXR genes in the GF model using northern blot hybridizations and gel retardation assays. The data showed that the expression of PPARα and RXRα genes was down-regulated in the livers containing preneoplastic nodules and in the liver tumors induced by GF. The mRNA down-regulation was accompanied by a decrease in the amount of nuclear protein–bound to peroxisome proliferator and retinoic acid responsive elements. Down-regulation was also associated with the suppressed expression of the PPARα/RXRα target genes (i.e., acyl-Co oxidase and cytochrome P450 4A1) and the catalase gene. The RXRγ gene was also down-regulated, but the RARα, β, and γ and PPARβ and γ genes were up-regulated. These results indicated that the hepatocarcinogenesis induced by GF is accompanied by suppression of the PPARα/RXRα-mediated direct hyperplasia pathway. The differential expression of these nuclear hormone receptors reveals a new aspect for understanding the individual roles and intercommunication of PPAR, RXR, and RAR isoforms in the liver. J. Cell. Biochem. 69:189–200, 1998. © 1998 Wiley-Liss, Inc.     

Liver-Specific Expressions of HBx and src in the p53 Mutant Trigger Hepatocarcinogenesis in Zebrafish

Hepatocarcinogenesis is a multistep process that starts from fatty liver and transitions to fibrosis and, finally, into cancer. Many etiological factors, including hepatitis B virus X antigen (HBx) and p53 mutations, have been implicated in hepatocarcinogenesis. However, potential synergistic effects between these two factors and the underlying mechanisms by which they promote hepatocarcinogenesis are still unclear. In this report, we show that the synergistic action of HBx and p53 mutation triggers progressive hepatocellular carcinoma (HCC) formation via src activation in zebrafish. Liver-specific expression of HBx in wild-type zebrafish caused steatosis, fibrosis and glycogen accumulation. However, the induction of tumorigenesis by HBx was only observed in p53 mutant fish and occurred in association with the up-regulation and activation of the src tyrosine kinase pathway. Furthermore, the overexpression of src in p53 mutant zebrafish also caused hyperplasia, HCC, and sarcomatoid HCC, which were accompanied by increased levels of the signaling proteins p-erk, p-akt, myc, jnk1 and vegf. Increased expression levels of lipogenic factors and the genes involved in lipid metabolism and glycogen storage were detected during the early stages of hepatocarcinogenesis in the HBx and src transgenic zebrafish. The up-regulation of genes involved in cell cycle regulation, tumor progression and other molecular hallmarks of human liver cancer were found at later stages in both HBx and src transgenic, p53 mutant zebrafish. Together, our study demonstrates that HBx and src overexpression induced hepatocarcinogenesis in p53 mutant zebrafish. This phenomenon mimics human HCC formation and provides potential in vivo platforms for drug screening for therapies for human liver cancer.     

Retinol-induced mdr1 and mdr3 modulation in cultured rat Sertoli cells is attenuated by free radical scavengers

The effects of retinol on modulation of mdr genes in Sertoli cells were investigated. The hypothesis that free radical scavengers may attenuate the effect of retinol was also tested. Sertoli cells isolated from 15-day-old Wistar rats were cultured for 48 h and then treated with retinol for 24 h with or without free radical scavengers (1 mM mannitol, 0.1 mM Trolox or superoxide dismutase [200 U/ml]). Expression of mdr1, mdr2 and mdr3 genes was monitored by RT-PCR. Mitochondrial superoxide production was used as an index of ROS production. Expression of mdr1 and mdr3 was inhibited by retinol treatment (7 microM, 24 h), while mdr2 was not detected in response to any of the treatments. We also observed that retinol supplementation (7 microM, 24 h) increased superoxide production. The observed inhibition of mdr genes was attenuated by all co-treatments, suggesting that retinol-induced ROS are required for inhibition of mdr1 and mdr3 expression. The results suggest that retinol may play an important role in the modulation of the mdr gene family in cultured rat Sertoli cells and that these effects appear to be mediated by ROS.     

Overexpression of Endothelin 1 Triggers Hepatocarcinogenesis in Zebrafish and Promotes Cell Proliferation and Migration through the AKT Pathway

Hepatocarcinogenesis commonly involves the gradual progression from hepatitis to fibrosis and cirrhosis, and ultimately to hepatocellular carcinoma (HCC). Endothelin 1 (Edn1) has been identified as a gene that is significantly up-regulated in HBx-induced HCC in mice. In this study, we further investigated the role of edn1 in hepatocarcinogenesis using a transgenic zebrafish model and a cell culture system. Liver-specific edn1 expression caused steatosis, fibrosis, glycogen accumulation, bile duct dilation, hyperplasia, and HCC in zebrafish. Overexpression of EDN1 in 293T cells enhanced cell proliferation and cell migration in in vitro and xenotransplantation assays and was accompanied with up-regulation of several cell cycle/proliferation- and migration-specific genes. Furthermore, expression of the unfolded protein response (UPR) pathway-related mediators, such as spliced XBP1, ATF6, IRE1, and PERK, was also up-regulated at both the RNA and protein levels. In the presence of an EDN1 inhibitor or an AKT inhibitor, these increases were diminished and the EDN1-induced migration ability also was disappeared, suggesting that the EDN1 effects act through activation of the AKT pathway to enhance the UPR and subsequently activate the expression of downstream genes. Additionally, p-AKT is enhanced in the edn1 transgenic fish compared to the GFP-mCherry control. The micro RNA miR-1 was found to inhibit the expression of EDN1. We also observed an inverse correlation between EDN1 and miR-1 expression in HCC patients. In conclusion, our data suggest that EDN1 plays an important role in HCC progression by activating the PI3K/AKT pathway and is regulated by miR-1.     

mdr2 encodes P-glycoprotein expressed in the bile canalicular membrane as determined by isoform-specific antibodies.

We have produced antibodies specific for the three P-glycoprotein (P-gp) isoforms encoded by the mouse mdr1, mdr2, and mdr3 genes. The anti-Mdr2 and anti-Mdr3 antibodies were generated against synthetic peptides derived from the "linker" region, whereas the anti-Mdr1 antibody was raised against a fusion protein containing the amino terminus of Mdr1. Western blot analysis showed that the three antibodies could discriminate between the three isoforms in membrane fractions from Hamster cells transfected with the corresponding full-length or chimeric mdr cDNAs. Immunocytochemistry studies of mdr-transfected cells showed that the three antibodies specifically recognized each P-gp isoform expressed in whole cells. Immunoblotting of normal mouse tissues revealed that the Mdr2 isoform was expressed at very high levels in liver canalicular membrane vesicles (CMV) but not in membrane vesicles prepared from the basolateral (sinusoidal) domain (SMV). Mdr3 was detected in intestinal brush border membrane vesicles and also in CMV, although at levels much lower than Mdr2. Mdr1 was not detected in CMV or SMV but was detected in endometrial tissue from the gravid uterus. Photolabeling experiments with [125I]iodoarylazidoprazosin followed by immunoprecipitation with isoform-specific antibodies indicated that, in CMV, Mdr3 but not Mdr2 could bind the drug analogue.     

The mdr1 gene, responsible for multidrug-resistance, codes for P-glycoprotein

The development of simultaneous resistance to multiple drugs in cultured cells occurs after selection for resistance to single agents. This multidrug-resistance phenotype is thought to mimic multidrug-resistance in human tumors treated with chemotherapy. Both the expression of a membrane protein, termed P170 or P-glycoprotein, and the expression of a cloned DNA fragment, termed mdr1, have been shown independently to be associated with multidrug-resistance in cultured cells. In this work, we show that human KB carcinoma cells which express the mdr1 gene also express P-glycoprotein, and that cDNAs encoding P-glycoprotein cross-hybridize with mdr1 cDNAs. Thus, the mdr1 gene codes for P-glycoprotein.     

Multidrug resistance of DNA-mediated transformants is linked to transfer of the human mdr1 gene.

Mouse NIH 3T3 cells were transformed to multidrug resistance with high-molecular-weight DNA from multidrug-resistant human KB carcinoma cells. The patterns of cross resistance to colchicine, vinblastine, and doxorubicin hydrochloride (Adriamycin; Adria Laboratories Inc.) of the human donor cell line and mouse recipients were similar. The multidrug-resistant human donor cell line contains amplified sequences of the mdr1 gene which are expressed at high levels. Both primary and secondary NIH 3T3 transformants contained and expressed these amplified human mdr1 sequences. Amplification and expression of the human mdr1 sequences and amplification of cotransferred human Alu sequences in the mouse cells correlated with the degree of multidrug resistance. These data suggest that the mdr1 gene is likely to be responsible for multidrug resistance in cultured cells.     

Proteomic analysis of liver tissue from HBx‐transgenic mice at early stages of hepatocarcinogenesis

The hepatitis B virus X‐protein (HBx), a multifunctional viral regulator, participates in the viral life cycle and in the development of hepatocellular carcinoma (HCC). We previously reported a high incidence of HCC in transgenic mice expressing HBx. In this study, proteomic analysis was performed to identify proteins that may be involved in hepatocarcinogenesis and/or that could be utilized as early detection biomarkers for HCC. Proteins from the liver tissue of HBx‐transgenic mice at early stages of carcinogenesis (dysplasia and hepatocellular adenoma) were separated by 2‐DE, and quantitative changes were analyzed. A total of 22 spots displaying significant quantitative changes were identified using LC‐MS/MS. In particular, several proteins involved in glucose and fatty acid metabolism, such as mitochondrial 3‐ketoacyl‐CoA thiolase, intestinal fatty acid‐binding protein 2 and cytoplasmic malate dehydrogenase, were differentially expressed, implying that significant metabolic alterations occurred during the early stages of hepatocarcinogenesis. The results of this proteomic analysis provide insights into the mechanism of HBx‐mediated hepatocarcinogenesis. Additionally, this study identifies possible therapeutic targets for HCC diagnosis and novel drug development for treatment of the disease.     

Serial analysis of gene expression in chronic hepatitis C and hepatocellular carcinoma

Hepatitis C virus (HCV) causes chronic hepatitis C (CH-C) and is epidemiologically linked with the occurrence of hepatocellular carcinoma (HCC). To elucidate the comprehensive gene expression profiles of CH-C and HCC, serial analysis of gene expression (SAGE) libraries were made from CH-C and HCC tissues of a patient, and compared with a reported SAGE library of a normal liver (NL). Scatter plots of the distribution of tags from the HCC library exhibited the existence of many differentially expressed genes compared with those from the CH-C and NL libraries. Up-regulation of IFN-gamma inducible genes and oxidative stress-inducible genes were identified in both the CH-C and HCC libraries, and some unpublished new genes were specifically up- or down-regulated in the HCC library. This genome-wide scanning study discloses the molecular portraits of CH-C and HCC, and provides novel candidate genes that should help clarify the mechanism of hepatocarcinogenesis in the chronically HCV-infected liver.     

Expression of mdr49 and mdr65 multidrug resistance genes in larval tissues of Drosophila melanogaster under normal and stress conditions

In situ expression of 2 multidrug resistance genes, mdr49 and mdr65, of Drosophila melanogaster was examined in wild-type third instar larval tissues under physiological conditions and after heat shock or colchicine feeding. Expression of these 2 genes was also examined in tumorous tissues of lethal (2) giant larvae I(2)gl4 mutant larvae. These 2 mdr genes show similar constitutive expression in different larval tissues under physiological conditions. However, they are induced differentially by endogenous (tumorous growth) and exogenous stresses (colchcine feeding or heat shock): whereas heat shock and colchicine feeding induce mdr49, tumorous condition is accompanied by enhanced expression of mdr49 and mdr65 genes.     

Increase in the concentration of carbon 18 monounsaturated fatty acids in the liver with hepatitis C: analysis in transgenic mice and humans

Steatosis is one of the histologic characteristics of chronic hepatitis C and is well reproduced in a transgenic mouse model for hepatocellular carcinoma (HCC) in which the core protein of hepatitis C virus (HCV) plays a pivotal role in inducing steatosis and HCC. In the present study, the lipid composition in the liver of the HCV core gene transgenic mice as well as in those of chronic hepatitis C patients was determined. The concentration of carbon 18 monounsaturated (C18:1) fatty acids, such as oleic and vaccenic acids, which are known to increase membrane fluidity leading to higher cell division rates, significantly increased in the livers of transgenic mice compared to nontransgenic control mice. The concentration of C18:1 fatty acids also significantly increased in the livers of chronic hepatitis C patients compared to subjects without HCV infection. These results suggest that HCV may affect a specific pathway in the lipid metabolism and cause steatosis in the liver.