Modulation of glucokinase expression by hypoxia-inducible factor 1 and upstream stimulatory factor 2 in primary rat hepatocytes

ER-stress promotes VHL-independent degradation of hypoxia-inducible factors via FBXW1A/βTrCP

Metabolic adaptation and signal integration in response to hypoxic conditions is mainly regulated by hypoxia-inducible factors (HIFs). At the same time, hypoxia induces ROS formation and activates the unfolded protein response (UPR), indicative of endoplasmic reticulum (ER) stress. However, whether ER stress would affect the hypoxia response remains ill-defined. Here we report that feeding mice a high fat diet causes ER stress and attenuates the response to hypoxia. Mechanistically, ER stress promotes HIF-1α and HIF-2α degradation independent of ROS, Ca²⁺, and the von Hippel-Lindau (VHL) pathway, involving GSK3β and the ubiquitin ligase FBXW1A/βTrCP. Thereby, we reveal a previously unknown function of the GSK3β/HIFα/βTrCP1 axis in ER homeostasis and demonstrate that inhibition of the HIF-1 and HIF-2 response and genetic deficiency of GSK3β affects proliferation, migration, and sensitizes cells for ER stress promoted apoptosis. Vice versa, we show that hypoxia affects the ER stress response mainly through the PERK-arm of the UPR. Overall, we discovered previously unrecognized links between the HIF pathway and the ER stress response and uncovered an essential survival pathway for cells under ER stress.

hsa-miR-875-5p inhibits tumorigenesis and suppresses TGF-β signalling by targeting USF2 in gastric cancer

Background

Gastric cancer (GC) is one of the most common malignancies, and an increasing number of studies have shown that its pathogenesis is regulated by various miRNAs. In this study, we investigated the role of miR-875-5p in GC.

Methods

The expression of miR-875-5p was detected in human GC specimens and cell lines by miRNA qRT–PCR. The effect of miR-875-5p on GC proliferation was determined by Cell Counting Kit-8 (CCK-8) proliferation and 5-ethynyl-2′-deoxyuridine (EdU) assays. Migration and invasion were examined by transwell migration and invasion assays as well as wound healing assays. The interaction between miR-875-5p and its target gene upstream stimulatory factor 2(USF2) was verified by dual luciferase reporter assays. The effects of miR-875-5p in vivo were studied in xenograft nude mouse models. Related proteins were detected by western blot.

Results

The results showed that miR-875-5p inhibited the proliferation, migration and invasion of GC cells in vitro and inhibited tumorigenesis in vivo. USF2 was proved to be a direct target of miR-875-5p. Knockdown of USF2 partially counteracted the effects of miR-875-5p inhibitor. Overexpression of miR-875-5p could inhibit proliferation, migration and invasion and suppress the TGF-β signalling pathway by downregulating USF2.

Conclusions

MiR-875-5p can inhibit the progression of GC by directly targeting USF2. And in the future, miR-875-5p is expected to be a potential target for GC diagnosis and treatment.

Functional interplay between the transcription factors USF1 and PDX-1 and protein kinase CK2 in pancreatic β-cells

Glucose homeostasis is regulated by insulin, which is produced in the β-cells of the pancreas. The synthesis of insulin is controlled by several transcription factors including PDX-1, USF1 and USF2. Both, PDX-1 and USF1 were identified as substrates for protein kinase CK2. Here, we have analysed the interplay of PDX-1, USF1 and CK2 in the regulation of PDX-1 gene transcription. We found that the PDX-1 promoter is dose-dependently transactivated by PDX-1 and transrepressed by USF1. With increasing glucose concentrations the transrepression of the PDX-1 promoter by USF1 is successively abrogated. PDX-1 binding to its own promoter was not influenced by glucose, whereas USF1 binding to the PDX-1 promoter was reduced. The same effect was observed after inhibition of the protein kinase activity by three different inhibitors or by using a phospho-mutant of USF1. Moreover, phosphorylation of USF1 by CK2 seems to strengthen the interaction between USF1 and PDX-1. Thus, CK2 is a negative regulator of the USF1-dependent PDX-1 transcription. Moreover, upon inhibition of CK2 in primary islets, insulin expression as well as insulin secretion were enhanced without affecting the viability of the cells. Therefore, inhibition of CK2 activity may be a promising approach to stimulate insulin production in pancreatic β-cells.

Multiple E-boxes in the distal promoter of the rat pyruvate carboxylase gene function as a glucose-responsive element

Pyruvate carboxylase (PC) is an anaplerotic enzyme that regulates glucose-induced insulin secretion in pancreatic islets. Dysregulation of its expression is associated with type 2 diabetes. Herein we describe the molecular mechanism underlying the glucose-mediated transcriptional regulation of the PC gene. Incubation of the rat insulin cell line INS-1 832/13 with glucose resulted in a 2-fold increase in PC mRNA expression. Transient transfections of the rat PC promoter-luciferase reporter construct in the above cell line combined with mutational analysis indicated that the rat PC gene promoter contains the glucose-responsive element (GRE), comprising three canonical E-boxes (E1, E3 and E4) and one E-box-like element (E2) clustering between nucleotides –546 and –399, upstream of the transcription start site. Mutation of any of these E-boxes resulted in a marked reduction of glucose-mediated transcriptional induction of the reporter gene. Electrophoretic mobility shift assays revealed that the upstream stimulatory factors 1 and 2 (USF1 and USF2) bind to E1, the Specificity Protein-1 (Sp1) binds to E2, USF2 and the carbohydrate responsive element binding protein (ChREBP) binds to E4, while unknown factors binds to E3. High glucose promotes the recruitment of Sp1 to E2 and, USF2 and ChREBP to E4. Silencing the expression of Sp1, USF2 and ChREBP by their respective siRNAs in INS-1 832/13 cells blunted glucose-induced expression of endogenous PC. We conclude that the glucose-mediated transcriptional activation of the rat PC gene is regulated by at least these three transcription factors.

Factors affecting insulin-regulated hepatic gene expression

Obesity has become a major concern of public health. A common feature of obesity and related metabolic disorders such as noninsulin-dependent diabetes mellitus is insulin resistance, wherein a given amount of insulin produces less than normal physiological responses. Insulin controls hepatic glucose and fatty acid metabolism, at least in part, via the regulation of gene expression. When the liver is insulin-sensitive, insulin can stimulate the expression of genes for fatty acid synthesis and suppress those for gluconeogenesis. When the liver becomes insulin-resistant, the insulin-mediated suppression of gluconeogenic gene expression is lost, whereas the induction of fatty acid synthetic gene expression remains intact. In the past two decades, the mechanisms of insulin-regulated hepatic gene expression have been studied extensively and many components of insulin signal transduction pathways have been identified. Factors that alter these pathways, and the insulin-regulated hepatic gene expression, have been revealed and the underlying mechanisms have been proposed. This chapter summarizes the recent progresses in our understanding of the effects of dietary factors, drugs, bioactive compounds, hormones, and cytokines on insulin-regulated hepatic gene expression. Given the large amount of information and progresses regarding the roles of insulin, this chapter focuses on findings in the liver and hepatocytes and not those described for other tissues and cells. Typical insulin-regulated hepatic genes, such as insulin-induced glucokinase and sterol regulatory element-binding protein-1c and insulin-suppressed cytosolic phosphoenolpyruvate carboxyl kinase and insulin-like growth factor-binding protein 1, are used as examples to discuss the mechanisms such as insulin regulatory element-mediated transcriptional regulation. We also propose the potential mechanisms by which these factors affect insulin-regulated hepatic gene expression and discuss potential future directions of the area of research.

STUB1/CHIP is required for HIF1A degradation by chaperone-mediated autophagy

The transcription factor HIF1 is mostly regulated by the oxygen-dependent proteasomal degradation of the labile subunit HIF1A. Recent data showed degradation of HIF1A in the lysosome through chaperone-mediated autophagy (CMA). However the molecular mechanism involved has not been elucidated. This study shows that the KFERQ-like motif, that has been identified in all CMA substrates, is required to mediate the interaction between HIF1A and the chaperone HSPA8. Moreover, mutations in the KFERQ-like motif of HIF1A preclude the interaction with the CMA receptor LAMP2A, thus inhibiting its lysosomal degradation. Importantly, we show for the first time that the ubiquitin ligase STUB1 is required for degradation of HIF1A in the lysosome by CMA. Indeed, mutations in STUB1 that inhibit either the ubiquitin ligase activity or its ability to bind to HSPA8, both prevent degradation of HIF1A by CMA. Moreover, we show that HIF1A binds to and is translocated into intact lysosomes isolated from rat livers. This new pathway for degradation of HIF1A does not depend on the presence of oxygen and is activated in response to nutrient deprivation such that the levels of HIF1A bound to CMA positive lysosomes significantly increase in starved animal livers and the binding of HIF1A to LAMP2A increases in response to serum deprivation. Moreover, excessive degradation of HIF1A by CMA compromises cells' ability to respond to and survive under hypoxia, suggesting that this pathway might be of pathophysiological importance in conditions that combine hypoxia with starvation.

Upstream stimulatory factor 1 activates GATA5 expression through an E-box motif

Silencing of GATA5 gene expression as a result of promoter hypermethylation has been observed in lung, gastrointestinal and ovarian cancers. However, the regulation of GATA5 gene expression has been poorly understood. In the present study, we have demonstrated that an E (enhancer)-box in the GATA5 promoter (bp -118 to -113 in mice; bp -164 to -159 in humans) positively regulates GATA5 transcription by binding USF1 (upstream stimulatory factor 1). Using site-directed mutagenesis, EMSA (electrophoretic mobility-shift analysis) and affinity chromatography, we found that USF1 specifically binds to the E-box sequence (5'-CACGTG-3'), but not to a mutated E-box. CpG methylation of this E-box significantly diminished its binding of transcription factors. Mutation of the E-box within a GATA5 promoter fragment significantly decreased promoter activity in a luciferase reporter assay. Chromatin immunoprecipitation identified that USF1 physiologically interacts with the GATA5 promoter E-box in mouse intestinal mucosa, which has the highest GATA5 gene expression in mouse. Co-transfection with a USF1 expression plasmid significantly increased GATA5 promoter-driven luciferase transcription. Furthermore, real-time and RT (reverse transcription)-PCR analyses confirmed that overexpression of USF1 activates endogenous GATA5 gene expression in human bronchial epithelial cells. The present study provides the first evidence that USF1 activates GATA5 gene expression through the E-box motif and suggests a potential mechanism (disruption of the E-box) by which GATA5 promoter methylation reduces GATA5 expression in cancer.

Hypoxia and hypoxia inducible factors: diverse roles in liver diseases

Hypoxia has been shown to have a role in the pathogenesis of several forms of liver disease. The hypoxia inducible factors (HIFs) are a family of evolutionarily conserved transcriptional regulators that affect a homeostatic response to low oxygen tension and have been identified as key mediators of angiogenesis, inflammation, and metabolism. In this review we summarize the evidence for a role of HIFs across a range of hepatic pathophysiology. We describe regulation of the HIFs and review investigations that demonstrate a role for HIFs in the development of liver fibrosis, activation of innate immune pathways, hepatocellular carcinoma, as well as other liver diseases in both human disease as well as murine models.

Hypoxia and hypoxia inducible factors: diverse roles in liver diseases

Hypoxia has been shown to have a role in the pathogenesis of several forms of liver disease. The hypoxia inducible factors (HIFs) are a family of evolutionarily conserved transcriptional regulators that affect a homeostatic response to low oxygen tension and have been identified as key mediators of angiogenesis, inflammation, and metabolism. In this review we summarize the evidence for a role of HIFs across a range of hepatic pathophysiology. We describe regulation of the HIFs and review investigations that demonstrate a role for HIFs in the development of liver fibrosis, activation of innate immune pathways, hepatocellular carcinoma, as well as other liver diseases in both human disease as well as murine models.

Disruption of HIF-1α in hepatocytes impairs glucose metabolism in diet-induced obesity mice

The liver plays a central role in glucose homeostasis in the whole-body by responding to environmental factors including nutrients, hormones, and oxygen. In conditions of metabolic overload such as diabetes mellitus and obesity, coordinated regulation between oxygen supply and consumption has been reported to be disrupted and subsequently cause tissue hypoxia, although pathological significance of the disease-related hypoxia remains elusive. To investigate the role of tissue hypoxia in the liver on systemic glucose homeostasis, mice lacking HIF-1α gene, a critical component of a master regulator of hypoxic response, in hepatocytes were exposed to high fat/sucrose diet (HFSD). Exposure to HFSD for 5 weeks elicited liver hypoxia with a transient increase in HIF-1α protein expression in the liver of control mice. Glucose disposal was marginally impaired in control mice when challenged oral glucose tolerance test, but such impairment was enhanced in the mutant mice. This alteration was accompanied by a complete inhibition of glucokinase induction with a significant reduction of hepatic glucose uptake. Mice fed HFSD for 20 weeks exhibited fasting hyperglycemia and glucose intolerance, whereas these metabolic phenotypes deteriorated considerably with severe insulin resistance in skeletal muscles and adipose tissues in the mutant mice. These findings suggest that HIF-1 in hepatocytes plays protective roles against the progression of diabetes mellitus.

The Loss of HIF1α Leads to Increased Susceptibility to Cadmium-Chloride-Induced Toxicity in Mouse Embryonic Fibroblasts

Wild-type and HIF1α −/− MEF cells were used to determine the role of HIF1α in cadmium-induced toxicity. Cadmium treatment did not affect HIF1-mediated transcription but led to caspase activation and apoptotic cell death in wild-type and HIF1α −/− cells. Cadmium-induced cell death, however, was significantly higher in HIF1α −/− cells as compared to their wild-type counterparts. Increased cell death in the HIF1α −/− cells was correlated with lower metallothionein protein, elevated levels of reactive oxygen species, and decreased superoxide dismutase enzyme activity. The total and oxidized glutathione levels, and, correspondingly, lipid peroxidation levels were elevated in the null cells compared to wild-type cells, indicating increased antioxidant demand and greater oxidative stress. Overall, the results suggest that basal levels of HIF1α play a protective role against cadmium-induced cytotoxicity in mouse embryonic fibroblasts by maintaining metallothionein and antioxidant activity levels.

Neonatal exposure to oxidants induces later in life a metabolic response associated to a phenotype of energy deficiency in an animal model of total parenteral nutrition

Failure to protect total parenteral nutrition (TPN) from ambient light exacerbates the generation of peroxides, which affects blood glucose and plasma triacylglyceride (TG) in neonates. Based on the concept that the origin of adult diseases can be traced back to perinatal life, it was hypothesized that neonatal exposure to peroxides may affect energy availability later in life. Three-day-old guinea pigs, fitted with a jugular catheter, were fed regular chow (sham) +/- i.v. 350 microM H2O2 (sham + H2O2) or nourished with light-protected TPN [TPN(-)L, 209 +/- 9 microM peroxides] or light-exposed TPN [TPN(+)L, 365 +/- 15 microM peroxides]. After 4 d, infusions were stopped and animals fed chow. Spontaneous ambulatory movements, fasting blood glucose, glucose tolerance, TG, hepatic activities of glucokinase, phosphofructokinase (key enzymes of glycolysis), and acetyl-CoA carboxylase (key enzymes of lipogenesis) were determined at 12-14 wk and compared by ANOVA (p < 0.05). Relative to sham, the animals from sham + H2O2, TPN(-)L and TPN(+)L groups had lower plasma TG explained for 36% by low phosphofructokinase activity; they had lower glucose tolerance, lower body weight, and lower physical activity. In conclusion, neonatal exposure to oxidant molecules such as peroxides has important consequences later in life on lipid and glucose metabolism leading to a phenotype of energy deficiency.

FoxO1 and HNF-4 are involved in regulation of hepatic glucokinase gene expression by resveratrol

Resveratrol, a polyphenol derived from grapes, exerts important effects on glucose and lipid metabolism, yet detailed mechanisms mediating these effects remain unknown. The liver plays a central role in energy homeostasis, and glucokinase (GK) is a key enzyme involved in glucose utilization. Resveratrol activates SIRT1 (sirtuin 1), which promotes deacetylation of the forkhead transcription factor FoxO1. Previously, we reported that FoxO1 can suppress and that HNF-4 can stimulate GK expression in the liver. Here, we examined the role of FoxO1 and HNF-4 in mediating resveratrol effects on liver GK expression. Resveratrol suppressed hepatic GK expression in vivo and in isolated hepatocytes, and knocking down FoxO1 with shRNAs disrupted this effect. Reporter gene, gel shift, supershift assay, and chromatin immunoprecipitation studies show that FoxO1 binds to the GK promoter and that the interplay between FoxO1 and HNF-4 within the GK promoter is essential for mediating the effects of resveratrol. Resveratrol promotes deacetylation of FoxO1 and enhances its recruitment to the FoxO-binding element. Conversely, resveratrol suppresses recruitment of HNF-4 to its binding site, and knockdown of FoxO1 blocks this effect of resveratrol. Coprecipitation and chromatin immunoprecipitation studies show that resveratrol enhances interaction between FoxO1 and HNF-4, reduces binding of HNF-4 to its own site, and promotes its recruitment to the FoxO site in a FoxO1-dependent manner. These results provide the first evidence that resveratrol represses GK expression via FoxO1 and that the interaction between FoxO1 and HNF-4 contributes to these effects of resveratrol.

Target gene specificity of USF-1 is directed via p38-mediated phosphorylation-dependent acetylation

How transcription factors interpret the output from signal transduction pathways to drive distinct programs of gene expression is a key issue that underpins development and disease. The ubiquitously expressed basic-helix-loop-helix leucine zipper upstream stimulating factor-1 binds E-box regulatory elements (CANNTG) to regulate a wide number of gene networks. In particular, USF-1 is a key component of the tanning process. Following UV irradiation, USF-1 is phosphorylated by the p38 stress-activated kinase on threonine 153 and directly up-regulates expression of the POMC, MC1R, TYR, TYRP-1 and DCT genes. However, how phosphorylation on Thr-153 might affect the activity of USF-1 is unclear. Here we show that, in response to DNA damage, oxidative stress and cellular infection USF-1 is acetylated in a phospho-Thr-153-dependent fashion. Phospho-acetylated USF-1 is nuclear and interacts with DNA but displays altered gene regulatory properties. Phospho-acetylated USF-1 is thus proposed to be associated with loss of transcriptional activation properties toward several target genes implicated in pigmentation process and cell cycle regulation. The identification of this critical stress-dependent USF-1 modification gives new insights into understanding USF-1 gene expression modulation associated with cancer development.

HINT1 inhibits beta-catenin/TCF4, USF2 and NFkappaB activity in human hepatoma cells

In this study we explored the relevance of Hint, a novel tumor suppressor gene, to human hepatoma. The human hepatoma cell lines Hep3B and HepG2 express very low levels of the HINT1 protein but the Huh7 cells express a relatively high level. In Hep3B and HepG2 cells, but not in Huh7 cells, the promoter region of Hint1 is partially methylated and treatment with 5-azadcdeoxycytidine increased expression of the HINT1 protein and Hint1 mRNA in Hep3B and HepG2 cells. Increased expression of HINT1 in HepG2 cells markedly inhibited their growth. It also inhibited the transcriptional activities of beta-catenin/TCF4, and USF2, and inhibited the expression of endogenous cyclin D1 and TGFbeta2. Furthermore, HINT1 co-immunoprecipitated with USF2 in extracts of Hep2 cells. HINT1 also inhibited NFkappaB transcription factor reporter activity and inhibited translocation of the endogenous p65 protein to the nucleus of HepG2 cells. Therefore, decreased expression of the Hint1 gene through epigenetic silencing may play a role in enhancing the growth of a subset of human hepatoma by increasing the expression of genes controlled by the transcription factors beta-catenin, USF2, and NFkappaB.

The role of hypoxia inducible factor-1 in cell metabolism--a possible target in cancer therapy

In many cancer types, intratumoural hypoxia is linked to increased expression and activity of the transcription factor hypoxia-inducible factor (HIF-1alpha), which is associated with poor patient prognosis. This increased the interest in HIF-1alpha as a cancer drug target. Further, HIF-1alpha has also a central role in the adaptive cellular programme responding to hypoxia in normal tissues. Many of the HIF-1alpha-regulated genes encode enzymes of metabolic pathways. Therefore, studying the link and the feedback mechanisms between metabolism and HIF-1alpha is of major importance to find new and specific therapeutic strategies.

HIF-dependent induction of apical CD55 coordinates epithelial clearance of neutrophils

Sites of inflammation are associated with dramatic shifts in tissue metabolism. Inflammation can result in significant tissue hypoxia, with resultant induction of hypoxia-responsive genes. Given this association, we hypothesized that neutrophil (PMN) ligands expressed on epithelial cells may be regulated by hypoxia. Initial studies confirmed earlier results that epithelial hypoxia enhances PMN transepithelial migration and promotes apical clearance of PMN from the epithelial surface. A screen of known PMN ligands revealed a surprisingly stable expression pattern in hypoxia. However, this screen identified one gene, CD55, as a highly hypoxia-inducible molecule expressed on the apical membrane of mucosal epithelia. Subsequent studies verified the induction of CD55 mRNA and protein expression by hypoxia. Overexpression of CD55 by transfection in nonhypoxic epithelia resulted in a similar pattern of apical PMN clearance, and peptide mimetics corresponding to the PMN binding site on DAF blocked such apical clearance of PMN. Studies directed at understanding molecular pathways of hypoxia inducibility revealed that a approximately 200 bp region of the CD55 gene conferred hypoxia inducibility for CD55. These studies identified a functional binding site for the transcriptional regulator hypoxia-inducible factor (HIF). Taken together, these results identify HIF-dependent induction of epithelial CD55 in the resolution of ongoing inflammation through clearance of apical PMN.

Upstream stimulating factors: highly versatile stress-responsive transcription factors

Upstream stimulating factors (USF), USF-1 and USF-2, are members of the eucaryotic evolutionary conserved basic-Helix-Loop-Helix-Leucine Zipper transcription factor family. They interact with high affinity to cognate E-box regulatory elements (CANNTG), which are largely represented across the whole genome in eucaryotes. The ubiquitously expressed USF-transcription factors participate in distinct transcriptional processes, mediating recruitment of chromatin remodelling enzymes and interacting with co-activators and members of the transcription pre-initiation complex. Results obtained from both cell lines and knock-out mice indicates that USF factors are key regulators of a wide number of gene regulation networks, including the stress and immune responses, cell cycle and proliferation, lipid and glucid metabolism, and in melanocytes USF-1 has been implicated as a key UV-activated regulator of genes associated with pigmentation. This review will focus on general characteristics of the USF-transcription factors and their place in some regulatory networks.

Roles for USF-2 in lung cancer proliferation and bronchial carcinogenesis

The upstream stimulatory factors USF-1 and USF-2 dimerize to regulate transcription through E-box motifs in target genes. Although widely expressed, they can mediate tissue-specific transcription and we previously reported that USF-2 can enhance transcription of arginine vasopressin, a neuropeptide growth factor in small cell lung cancer. Here we determine the expression and role of USF-2 in lung cancer subtypes and examine USF-2 distribution in the bronchial epithelium. For a panel of 12 cell lines and 10 frozen human tumour samples, immunoblotting demonstrated that USF-2 expression was more frequent and abundant in small cell lung cancer than in non-small cell lung cancer. An immunohistochemical study of 108 formalin-fixed and paraffin-embedded human samples was undertaken to localize USF-2 expression and included 44 small cell and 32 non-small cell lung cancers, and 32 samples with bronchial dysplasia. USF-2 was restricted to ciliated cells in normal bronchial epithelium, but was more strongly expressed in dysplastic epithelium (72%) and certain lung cancer types, including small cell lung cancer (71%), squamous cell carcinoma (69%) and a large cell neuroendocrine carcinoma, but was less common in adenocarcinoma (11%). In a small series, expression was assessed adjacent to positively staining tumours; in phenotypically normal bronchial tissues, USF-2 was more highly expressed at 1 cm than at 5 cm from the tumour. Transient USF-2 overexpression in non-small cell lung cancer cell lines significantly stimulated in vitro cell proliferation; this response was most apparent for NCI-H460 (p < 0.005), reducing the mean cell doubling time from 19 to 16 h. Dominant-negative USF-2 mutants had no significant effect on cell growth. Taken together, these data suggest that USF-2 represents a relatively early molecular marker for the development of bronchial dysplasia and non-adenocarcinoma lung cancer. USF may also play a role in bronchial carcinogenesis, perhaps through promoting cell proliferation, although the genes through which this is regulated remain to be determined.

Construction of two vectors harboring PNP gene under control of two different promoters and their expression

AIM: To construct two expression vectors carrying PNP gene under a cytomegalovirus (CMV) promoter and a hybrid a-fetoprotein (AFP) tissue-specific promoter, and to detect and analyze their expression in different cell lines.

METHODS: [HRE]AF promoter was inserted into pcDNA3.0 vector, and a recombinant vector controlled by the hybrid AFP promoter, p[HRE]AF, was constructed. Inserting PNP gene into pcDNA3.0 and p[HRE]AF vectors separately, two PNP gene expression vectors driven by two different promoters, pcDNA3.0/PNP and p[HRE]AF /PNP, were constructed by using recombinant DNA techniques. The recombinants were analyzed and identified by restriction enzymes, PCR and sequencing. pcDNA3.0/PNP and p[HRE]AF/PNP were transfected into human hepatocellular carcinoma cell lines by liposome-mediated method. The expression of PNP gene in four different cell lines was detected by RT-PCR method.

RESULTS: All target fragments were separately cloned into corresponding vectors. We detected the expression of PNP gene under the control of CMV promoter in all cell lines, and the tissue-specific expression of PNP gene under the control of [HRE]AF promoter in AFP positive and negative hepatocellular carcinoma cell line was positive.

CONCLUSION: Two expression vectors harboring PNP gene are novel effective vectors for human hepatocellular carcinoma gene therapy, and p[HRE]AF/PNP is a target-expressing vector in AFP positive, especially in AFP negative hepatocellular carcinoma cells.