Improvement in liver histology due to lifestyle modification is independently associated with improved kidney function in patients with non-alcoholic steatohepatitis.

BACKGROUND: Several recent studies have shown a strong association between non-alcoholic steatohepatitis (NASH) and chronic kidney disease. AIM: To examine the relationship between changes in liver histology and renal function in patients with NASH. METHODS: The present analysis represents a post hoc analysis of a recently published trial that included 261 patients with NASH who were treated with lifestyle modifications during 52 weeks. Kidney function was evaluated through Chronic Kidney Disease Epidemiology Collaboration estimated glomerular filtration rates (eGFR, mL/min/1.73 m2 ) overtime. We explored correlations between the kidney function and improvement in histological outcomes at 52 weeks. RESULTS: Interestingly, a one-stage reduction in fibrosis (r = 0.20, P < 0.01) and resolution of NASH (r = 0.17, P < 0.01) were significantly correlated with an improvement in the kidney function. The eGFR values significantly increased in patients with fibrosis improvement (+7.6 ± 6.5 mL/min/1.73 m2 ), compared to those without fibrosis improvement (-1.98 ± 6.4 mL/min/1.73 m2 ) (P < 0.01) at end of treatment (EOT). Likewise, NASH resolution was associated with an increase in eGFR compared with patients without NASH resolution (2.32 ± 7.8 mL/min/1.73 m2 vs. -1.04 ± 5.9 mL/min/1.73 m2 , P = 0.04) at EOT. After controlling for the confounders, the association between fibrosis improvement, NASH resolution and eGFR change remained significant (P < 0.05 for both). CONCLUSIONS: Improvement in liver histology due to lifestyle modification is independently associated with improved kidney function in NASH. As new drugs for NASH emerge, studies should address whether improvement in histology in response to pharmacotherapies yield the same improvement in kidney function as weight loss.

Early Liver Transplantation for Severe Alcoholic Hepatitis in the United States--A Single-Center Experience.

Early liver transplantation (LT) in European centers reportedly improved survival in patients with severe alcoholic hepatitis (AH) not responding to medical therapy. Our aim was to determine if a strategy of early LT for severe AH could be applied successfully in the United States. We reviewed 111 patients with severe AH at our center from January 2012 to January 2015. The primary end point was mortality at 6 months or early LT, with a secondary end point of alcohol relapse after LT. Survival was compared between those receiving early LT and matched patients who did not. Using a process similar to the European trial, 94 patients with severe AH not responding to medical therapy were evaluated for early LT. Overall, 9 (9.6%) candidates with favorable psychosocial profiles underwent early LT, comprising 3% of all adult LT during the study period. The 6-month survival rate was higher among those receiving early LT compared with matched controls (89% vs 11%, p<0.001). Eight recipients are alive at a median of 735 days with 1 alcohol relapse. Early LT for severe AH can achieve excellent clinical outcomes with low impact on the donor pool and low rates of alcohol relapse in highly selected patients in the United States.

Standard operating procedures in experimental liver research: thioacetamide model in mice and rats.

In addition to carbon tetrachloride (CCl4), thioacetamide (TAA) represents a second widely used model for the induction of experimental liver fibrosis, but can also be employed for the development of acute liver failure and liver tumours. While TAA itself is not hepatotoxic, its reactive metabolites covalently bind to proteins and lipids thereby causing oxidative stress and centrilobular necrosis. Compared with CCl4, TAA leads to more periportal infiltrates and more pronounced ductal proliferation. While TAA has been shown to induce liver fibrosis development in several different mouse strains, wide variations in the administration routes, doses and treatment durations have been reported. Therefore, an adoption of a universal standard operating procedure for the administration of TAA is urgently needed. For that purpose, we are presenting here two TAA models (intraperitoneal administration of 150 mg/kg of TAA three times per week for 11 weeks in rats, and TAA administration in drinking water at 300 mg/L for 2-4 months in mice) with which we have had success in reliably and reproducibly developing chronic liver injury and fibrosis.

GSK3ß phosphorylation of the KLF6 tumor suppressor promotes its transactivation of p21.

KLF6, a ubiquitously expressed Krüppel-like transcription factor, is frequently inactivated in human cancer and has significant roles in cellular proliferation, apoptosis, differentiation and development. A key mechanism of KLF6-mediated growth suppression is through p53-independent transactivation of p21. Several cancer-derived KLF6 mutants lead to the loss of p21-mediated growth suppression through an unknown mechanism. Because several colorectal cancer and hepatocellular carcinoma-derived KLF6 mutations affect a glycogen synthase kinase 3ß (GSK3ß) phosphorylation consensus site, we investigated the role of GSK3ß in the regulation of KLF6 function. Based on transient transfection, GSK3ß augments the transactivation of a p21 promoter luciferase by KLF6. Reciprocal co-immunoprecipitation of hemagglutinin (HA)-GSK3ß and Flag-KLF6 validated the interaction between these two proteins. KLF6 phosphorylation is augmented in the presence of GSK3ß based on in vitro and in vivo (32)P incorporation assays. Site-directed mutagenesis of the candidate phosphorylation sites to alanines ('KLF6-4A' phosphomutant) eliminated a higher molecular weight phosphorylated isoform of KLF6 based on western blot. GSK3ß augmented the transactivation by wild-type KLF6, but not KLF6-4A, towards the p21 promoter, and increased p21 protein. Functionally, GSK3ß enhanced KLF6-mediated growth suppression, which was abrogated by the KLF6-4A phosphomutant. These data establish that GSK3ß directly phosphorylates KLF6, which augments its induction of p21 and resultant growth suppression. This interaction may account for the growth-promoting effects of cancer-derived KLF6 mutants that lack tumor suppressor activity.

Natural history of small duct primary sclerosing cholangitis: a case series with review of the literature.

BACKGROUND AND AIMS: Information about the natural history of small duct primary sclerosing cholangitis (SDPSC) remains scant despite literature suggesting that it constitutes 6-16% of all cases of primary sclerosing cholangitis (PSC). We combined clinical data on SDPSC cases from two tertiary care institutions with liver transplantation programs with the aim of studying the natural history of SDPSC. METHODS: Medical records of 25 individuals with SDPSC were reviewed. Diagnosis of SDPSC was based on liver biopsy findings consistent with PSC, a normal cholangiogram, and elimination of known causes of secondary sclerosing cholangitis. Demographic information, symptoms, past medical history, laboratory values, and histologic data were evaluated. Our primary outcome measure was liver transplantation or death. Secondary outcome measures included evidence of end-stage liver disease, development of cholangiocarcinoma, and/or the development of classic PSC on a repeat cholangiogram. RESULTS: Data on 25 individuals (13 males, 12 females; mean age 40 ± 15 years) diagnosed with SDPSC were analyzed. Upon presentation, 11 patients had symptoms including abdominal pain, fatigue, and pruritus. Inflammatory bowel disease was present in 14 patients (56%) at diagnosis. On initial liver biopsy, 60% had early-stage disease (I or II) and none had cirrhosis. On follow-up (1-168 months, median 17 months), malignancy or progression to classic large duct PSC was not noted. Two (8%) patients had evidence of varices and one of the two also developed ascites; one of these patients underwent liver transplantation and the other one died due to sepsis. CONCLUSIONS: SDPSC, a mild disease at presentation typically runs a benign course and likely is not an early stage of classic PSC. Further studies with a control group of classic PSC and longer follow-up are needed to study the natural history of SDPSC.

Hepatocyte apoptotic bodies encasing nonstructural HCV proteins amplify hepatic stellate cell activation: implications for chronic hepatitis C.

Chronic hepatitis C infection leads to increased hepatocyte apoptosis. Because engulfment of apoptotic bodies (ABs) by hepatic stellate cells (HSC) is profibrogenic, we compared the effects of ABs derived from hepatitis C virus (HCV)-negative vs HCV-infected (Con1+) Huh7 hepatoblastoma cells on fibrogenic and activation-related mRNA expression by a human HSC line (LX2). Uptake of Huh7(Con1+) ABs by LX2 cells dose dependently upregulated profibrotic genes (COL1A1, TGFB1; TIMP1; TIMP2). When normalized to the apoptotic cytokeratin-18 M30 neoepitope, HCV(+) ABs exhibited a more pronounced effect than HCV(-) ABs. In contrast, neither noningested ABs nor nucleic acids obtained from Huh7, Huh7(Con1+) or HepG2 cells triggered those AB-dependent effects. Both the engulfment of Huh7(Con1+) ABs and their effects were partially blocked by masking of phosphatidylserine with annexin V and completely inhibited by the class-A scavenger receptor ligand, polyinosinic acid. Our findings demonstrate that AB uptake stimulates HSCs and indicate that HCV infection leads to amplified fibrogenic mRNA expression and enhanced HSC activation.

Antimicrobial resistance of Campylobacter isolates from retail meat in the United States between 2002 and 2007.

The emergence of antimicrobial resistance in Campylobacter spp. has been a growing public health concern globally. The objectives of this study were to determine the prevalence, antimicrobial susceptibility, and genetic relatedness of Campylobacter spp. recovered by the National Antimicrobial Resistance Monitoring System (NARMS) retail meat program. Retail meat samples (n = 24,566) from 10 U.S. states collected between 2002 and 2007, consisting of 6,138 chicken breast, 6,109 ground turkey, 6,171 ground beef, and 6,148 pork chop samples, were analyzed. A total of 2,258 Campylobacter jejuni, 925 Campylobacter coli, and 7 Campylobacter lari isolates were identified. Chicken breast samples showed the highest contamination rate (49.9%), followed by ground turkey (1.6%), whereas both pork chops and ground beef had <0.5% contamination. The most common resistance was to doxycycline/tetracycline (46.6%), followed by nalidixic acid (18.5%), ciprofloxacin (17.4%), azithromycin and erythromycin (2.8%), telithromycin (2.4%), clindamycin (2.2%), and gentamicin (<0.1%). In a subset of isolates tested, no resistance to meropenem and florfenicol was seen. C. coli isolates showed higher resistance rates to antimicrobials, with the exception of doxycycline/tetracycline, than those seen for C. jejuni. Pulsed-field gel electrophoresis (PFGE) fingerprinting resulted in 1,226 PFGE profiles among the 2,318 isolates, with many clones being widely dispersed throughout the 6-year sampling period.

beta-Lactam resistance in salmonella strains isolated from retail meats in the United States by the National Antimicrobial Resistance Monitoring System between 2002 and 2006.

Ampicillin-resistant (Amp(r)) Salmonella enterica isolates (n = 344) representing 32 serotypes isolated from retail meats from 2002 to 2006 were tested for susceptibility to 21 other antimicrobial agents and screened for the presence of five beta-lactamase gene families (bla(CMY), bla(TEM), bla(SHV), bla(OXA), and bla(CTX-M)) and class 1 integrons. Among the Amp(r) isolates, 66.9% were resistant to five or more antimicrobials and 4.9% were resistant to 10 or more antimicrobials. Coresistance to other beta-lactams was noted for amoxicillin-clavulanic acid (55.5%), ceftiofur (50%), cefoxitin (50%), and ceftazidime (24.7%), whereas less than 5% of isolates were resistant to piperacillin-tazobactam (4.9%), cefotaxime (3.5%), ceftriaxone (2%), and aztreonam (1.2%). All isolates were susceptible to cefepime, imipenem, and cefquinome. No Salmonella producing extended-spectrum beta-lactamases was found in this study. Approximately 7% of the isolates displayed a typical multidrug-resistant (MDR)-AmpC phenotype, with resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline, plus resistance to amoxicillin-clavulanic acid, cefoxitin, and ceftiofur and with decreased susceptibility to ceftriaxone (MIC > or = 4 microg/ml). Pulsed-field gel electrophoresis results showed that several MDR clones were geographically dispersed in different types of meats throughout the five sampling years. Additionally, 50% of the isolates contained bla(CMY), 47% carried bla(TEM-1), and 2.6% carried both genes. Only 15% of the isolates harbored class I integrons carrying various combinations of aadA, aadB, and dfrA gene cassettes. The bla(CMY), bla(TEM), and class 1 integrons were transferable through conjugation and/or transformation. Our findings indicate that a varied spectrum of coresistance traits is present in Amp(r) Salmonella strains in the meat supply of the United States, with a continued predominance of bla(CMY) and bla(TEM) genes in beta-lactam-resistant isolates.

Antimicrobial resistance in Salmonella enterica serovar Heidelberg isolates from retail meats, including poultry, from 2002 to 2006.

Salmonella enterica serovar Heidelberg frequently causes food-borne illness in humans. There are few data on the prevalence, antimicrobial susceptibility, and genetic diversity of Salmonella serovar Heidelberg isolates in retail meats. We compared the prevalences of Salmonella serovar Heidelberg in a sampling of 20,295 meats, including chicken breast (n = 5,075), ground turkey (n = 5,044), ground beef (n = 5,100), and pork chops (n = 5,076), collected during 2002 to 2006. Isolates were analyzed for antimicrobial susceptibility and compared genetically using pulsed-field gel electrophoresis (PFGE) and PCR for the bla(CMY) gene. A total of 298 Salmonella serovar Heidelberg isolates were recovered, representing 21.6% of all Salmonella serovars from retail meats. One hundred seventy-eight (59.7%) were from ground turkey, 110 (36.9%) were from chicken breast, and 10 (3.4%) were from pork chops; none was found in ground beef. One hundred ninety-eight isolates (66.4%) were resistant to at least one compound, and 49 (16.4%) were resistant to at least five compounds. Six isolates (2.0%), all from ground turkey, were resistant to at least nine antimicrobials. The highest resistance in poultry isolates was to tetracycline (39.9%), followed by streptomycin (37.8%), sulfamethoxazole (27.7%), gentamicin (25.7%), kanamycin (21.5%), ampicillin (19.8%), amoxicillin-clavulanic acid (10.4%), and ceftiofur (9.0%). All isolates were susceptible to ceftriaxone and ciprofloxacin. All ceftiofur-resistant strains carried bla(CMY). PFGE using XbaI and BlnI showed that certain clones were widely dispersed in different types of meats and meat brands from different store chains in all five sampling years. These data indicate that Salmonella serovar Heidelberg is a common serovar in retail poultry meats and includes widespread clones of multidrug-resistant strains.

Immunomodulatory effects of plasminogen activators on hepatic fibrogenesis.

Tissue-type plasminogen activators (tPA) and urokinase-type plasminogen activators (uPA) are involved in liver repair. We examined the potential immunomodulatory actions of uPA, tPA and uPA-receptor (uPAR) in carbon-tetrachloride-induced hepatic fibrosis in wild-type (WT), tPA-/-, uPA-/- and uPAR-/- mice. Carbon-tetrachloride treatment increased fibrosis in four groups but significantly less in three knock-out models. Serum cytokines and intrahepatic T cells elevated significantly following fibrosis process in WT animals but not in the knock-out groups. In culture, uPA increased lymphocyte proliferation significantly in WT and uPA-/- but not uPAR-/- animals. Following uPA exposure in vivo, there was CD8 predominance. To isolate uPA's effect on lymphocytes, WT mice were irradiated sublethally and then reconstituted with WT or uPA-/- lymphocytes. In these animals fibrosis was decreased and T cells were reduced in the uPA-/- recipients. Based on these data we postulate that plasminogen activators affect fibrosis in part by liver-specific activation of CD8 subsets that govern the fibrogenic activity of hepatic stellate cells.

Characterization of multidrug resistant Salmonella recovered from diseased animals.

Three hundred and eighty Salmonella isolates recovered from animal diagnostic samples obtained from four state veterinary diagnostic laboratories (AZ, NC, MO, and TN) between 2002 and 2003 were tested for antimicrobial susceptibilities and further characterized for bla(CMY) beta-lactamase genes, class 1 integrons and genetic relatedness using PFGE. Forty-seven serovars were identified, the most common being S. Typhimurium (26%), S. Heidelberg (9%), S, Dublin (8%), S. Newport (8%), S. Derby (7%), and S. Choleraesuis (7%). Three hundred and thirteen (82%) isolates were resistant to at least one antimicrobial, and 265 (70%) to three or more antimicrobials. Resistance was most often observed to tetracycline (78%), followed by streptomycin (73%), sulfamethoxazole (68%), and ampicillin (54%), and to a lesser extent chloramphenicol (37%), kanamycin (37%), amoxicillin-clavulanic acid (20%), and ceftiofur (17%). With regards to animal of origin, swine Salmonella isolates displayed the highest rate of resistance, being resistant to at least one antimicrobial (92%), followed by those recovered from turkey (91%), cattle (77%), chicken (68%), and equine (20%). Serovars commonly showing multidrug resistance (MDR) to > or =9 antimicrobials were S. Uganda (100%), S. Agona (79%), and S. Newport (62%), compared to S. Heidelberg (11%) and S. Typhimurium (7%). Class-1 integrons were detected in 43% of all isolates, and were found to contain aadA, aadB, dhfr, cmlA and sat1 gene cassettes alone or in various combinations. All ceftiofur resistant isolates (n=66) carried the bla(CMY) beta-lactamase gene. A total of 230 PFGE patterns were generated among the 380 isolates tested using XbaI, indicating extensive genetic diversity across recovered Salmonella serovars, however, several MDR clones were repeatedly recovered from different diseased animals.

The ecology of childhood overweight: a 12-year longitudinal analysis.

OBJECTIVE: To investigate ecological correlates of the development of overweight in a multisite study sample of children followed from age 2 to 12. DESIGN: Longitudinal examination of covariates of overweight status throughout childhood, with covariates drawn from three ecological levels: sociocultural or demographic, quality of the child's home environment, and proximal child experience that could directly affect the balance between energy intake and energy expenditure. SUBJECTS: A total of 960 children participating in a long-term longitudinal study provided growth data at least once; 653 of the children had complete data on covariates. MEASUREMENTS: Height and weight measured seven times between ages 2 and 12 were converted to a body mass index (BMI) and entered into a latent transition analysis to identify patterns of overweight across childhood. Ecological correlates measured longitudinally included demographic characteristics obtained by maternal report, home environment quality obtained by observation and maternal report, and proximal child experience factors obtained by observation, maternal report and child report. RESULTS: Four patterns of overweight were found: never overweight, overweight beginning at preschool age, overweight beginning in elementary school, and return to normal weight after being overweight at preschool age. The weight status groups differed on home environment quality and proximal child experience factors but not on demographics. Children overweight at preschool had less sensitive mothers than never overweight children. Children overweight at school age had fewer opportunities for productive activity at home than did never overweight children. School-age overweight children also watched the most TV after school. Multivariate logistic regression analyses further indicated the significance to children's weight status of proximal child experience variables. Less physically active children and those who watched more television after school were more likely to become overweight. Results did not vary by child sex. CONCLUSION: The results support the idea that childhood overweight is multiply determined. The one potentially important and changeable factor identified as a target for intervention centers on how children spend their time, especially their after-school time. Children who are more physically active and spend less time watching TV after school are less likely to become overweight by age 12.

In vivo regulation of p21 by the Kruppel-like factor 6 tumor-suppressor gene in mouse liver and human hepatocellular carcinoma.

Kruppel-like factor (KLF) 6 is a tumor-suppressor gene functionally inactivated by loss of heterozygosity, somatic mutation and/or alternative splicing that generates a dominant-negative splice form, KLF6-SV1. Wild-type KLF6 (wtKLF6) expression is decreased in many human malignancies, which correlates with reduced patient survival. Additionally, loss of the KLF6 locus in the absence of somatic mutation in the remaining allele occurs in a number of human cancers, raising the possibility that haploinsufficiency of the KLF6 gene alone contributes to cellular growth dysregulation and tumorigenesis. Our earlier studies identified the cyclin-dependent kinase inhibitor p21 as a transcriptional target of the KLF6 gene in cultured cells, but not in vivo. To address this issue, we have generated two genetic mouse models to define the in vivo role of KLF6 in regulating cell proliferation and p21 expression. Transgenic overexpression of KLF6 in the liver resulted in a runted phenotype with decreased body and liver size, with evidence of decreased hepatocyte proliferation, increased p21 and reduced proliferating cell nuclear antigen expression. In contrast, mice with targeted deletion of one KLF6 allele (KLF6+/-) display increased liver mass with reduced p21 expression, compared to wild type littermates. Moreover, in primary hepatocellular carcinoma samples, there is a significant correlation between wtKLF6 and p21 mRNA expression. Combined, these data suggest that haploinsufficiency of the KLF6 gene may regulate cellular proliferation in vivo through decreased transcriptional activation of the cyclin-dependent kinase inhibitor p21.

E-cadherin is a novel transcriptional target of the KLF6 tumor suppressor.

The tumor suppressor KLF6 is a member of the Krüppel-like family of transcription factors, which has been implicated in the pathogenesis of several human carcinomas. Uncovering the transcriptional targets relevant for its tumorigenic properties, including cellular proliferation and invasion, will be essential to understanding possible mechanisms by which KLF6 and its antagonistic splice form, KLF6-SV1, regulate this development. To begin defining possible metastatic-related pathways, we analysed the effect of KLF6 dysregulation on a recognized suppressor of cellular invasion, E-cadherin. Targeted KLF6 reduction in an ovarian cancer cell line, SKOV-3, resulted in a 50% reduction of E-cadherin expression (P<0.01) and conversely, KLF6-SV1 silencing upregulated E-cadherin approximately fivefold (P<0.0001). These changes resulted from KLF6 directly transactivating the E-cadherin promoter as demonstrated by luciferase promoter assay and chromatin immunoprecipitation (ChIP). KLF6-mediated changes in E-cadherin levels were accompanied by downstream changes in both the subcellular localization of beta-catenin and c-myc expression levels. Moreover, and consistent with these experimental findings, patient-derived epithelial ovarian tumors with low KLF6 and high KLF6-SV1 expression ratios had significantly decreased E-cadherin expression (P<0.0001). These combined findings highlight the E-cadherin pathway as a novel and functionally important mediator by which changes in KLF6 and KLF6-SV1 can directly alter ovarian tumor invasion and metastasis.

Antifibrotic agents for liver disease.

Complications from chronic hepatitis C (HCV) and recurrent HCV post-transplant are responsible for significant morbidity and mortality in the United States and Europe. Current antiviral therapies are at best, effective in up to 50% of patients in the pre-transplant setting, and in the post-transplant setting are associated with more limited efficacy and increased toxicity. With this reduced efficacy of antiviral strategies in the post-transplant setting, new approaches are urgently needed. Substantial progress has been made in understanding the pathogenesis of hepatic fibrosis over the last 20 years, which has yielded potential new therapeutic targets. The prospect of antifibrotic therapies is nearing reality in order to reduce progression to cirrhosis, thereby reducing morbidity, mortality and the need for re-transplantation. Current and evolving approaches primarily target the activated hepatic stellate cells, which are the main source of extracellular matrix, along with related fibrogenic cell types. Key issues yet to be clarified include the optimal duration of antifibrotic therapies, endpoints of clinical trials, indications in clinical practice and whether combination therapies might yield synergistic activity.

Human hepatic stellate cell lines, LX-1 and LX-2: new tools for analysis of hepatic fibrosis.

BACKGROUND: Hepatic stellate cells (HSCs) are a major fibrogenic cell type that contributes to collagen accumulation during chronic liver disease. With increasing interest in developing antifibrotic therapies, there is a need for cell lines that preserve the in vivo phenotype of human HSCs to elucidate pathways of human hepatic fibrosis. We established and characterised two human HSC cell lines termed LX-1 and LX-2, and compared their features with those of primary human stellate cells. METHODS AND RESULTS: LX-1 and LX-2 were generated by either SV40 T antigen immortalisation (LX-1) or spontaneous immortalisation in low serum conditions (LX-2). Both lines express alpha smooth muscle actin, vimentin, and glial fibrillary acid protein, as visualised by immunocytochemistry. Similar to primary HSCs, both lines express key receptors regulating hepatic fibrosis, including platelet derived growth factor receptor beta (betaPDGF-R), obese receptor long form (Ob-RL), and discoidin domain receptor 2 (DDR2), and also proteins involved in matrix remodelling; matrix metalloproteinase (MMP)-2, tissue inhibitor of matrix metalloproteinase (TIMP)-2, and MT1-MMP, as determined by western analyses. LX-2 have reduced expression of TIMP-1. LX-2, but not LX-1, proliferate in response to PDGF. Both lines express mRNAs for alpha1(I) procollagen and HSP47. Transforming growth factor beta1 stimulation increased their alpha1(I) procollagen mRNA expression, as determined by quantitative reverse transcription-polymerase chain reaction. LX-2, but not LX-1, cells are highly transfectable. Both lines had a retinoid phenotype typical of stellate cells. Microarray analyses showed strong similarity in gene expression between primary HSCs and either LX-1 (98.4%) or LX-2 (98.7%), with expression of multiple neuronal genes. CONCLUSIONS: LX-1 and LX-2 human HSC lines provide valuable new tools in the study of liver disease. Both lines retain key features of HSCs. Two unique advantages of LX-2 are their viability in serum free media and high transfectability.

KLF6, a candidate tumor suppressor gene mutated in prostate cancer.

Kruppel-like factor 6 (KLF6) is a zinc finger transcription factor of unknown function. Here, we show that the KLF6 gene is mutated in a subset of human prostate cancer. Loss-of-heterozygosity analysis revealed that one KLF6 allele is deleted in 77% (17 of 22) of primary prostate tumors. Sequence analysis of the retained KLF6 allele revealed mutations in 71% of these tumors. Functional studies confirm that whereas wild-type KLF6 up-regulates p21 (WAF1/CIP1) in a p53-independent manner and significantly reduces cell proliferation, tumor-derived KLF6 mutants do not. Our data suggest that KLF6 is a tumor suppressor gene involved in human prostate cancer.

DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells.

Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.

Transcriptional regulation in hepatic stellate cells.

Modulation of gene expression through altered transcription regulates stellate cell behavior in normal liver and following hepatic injury. Transcription factors are generally classified according to conserved motifs within either the activation- or DNA- binding domains of the molecules. Transcriptional activity in stellate cells represents a delicate fine tuning of multiple inputs. Activities of these transcription factors are modified by their intracellular localization, rate and pathway of degradation, oligomerization, and interactions with heterologous factors and chromatin, as well as by posttranslational modifications, including phosphorylation, glycosylation, and acetylation. General paradigms of transcriptional control are increasingly being validated in hepatic stellate cells, particularly involving the transcription factors CCAAT/enhancer-binding proteins, c-myb, CREB, nuclear factor kappaB, peroxisome proliferator-activated receptor, and Kruppel-like zinc finger factors. Although there are no simple rules that govern mechanisms of transcriptional regulation in stellate cells, continued advances will yield new insights into their role in normal liver homeostasis and in the response to injury.

Phosphorylation of retinoid X receptor alpha at serine 260 impairs its metabolism and function in human hepatocellular carcinoma.

Retinoids induce apoptosis and differentiation of hepatocellular carcinoma (HCC) cells and are used clinically in the chemoprevention of HCC. We have shown previously that hepatocarcinogenesis is accompanied by accumulation of full-length retinoid X receptor alpha (RXRalpha), although the underlying mechanisms and biological implications have remained unclear. The present studies were based on the finding that the accumulated full-length RXRalpha was phosphorylated at serine/threonine residues both in all human HCC tissues examined and in human HCC-derived HuH7 cells. Phosphorylation at serine 260 of RXRalpha, a consensus site of mitogen-activated protein kinase, was closely linked to its retarded degradation, low transactivating activity, and the promotion of cancer cell growth. There was no genomic mutation in the RXRalpha gene, and abrogation of phosphorylation by mitogen-activated protein kinase-specific inhibitors restored the degradation of RXRalpha in an RXR ligand-dependent manner. These results suggest that phosphorylation of RXRalpha may interfere with its metabolism and signaling in human HCC, which could lead to growth promotion of these tumors.