Human actin genes are single copy for alpha-skeletal and alpha-cardiac actin but multicopy for beta- and gamma-cytoskeletal genes: 3' untranslated regions are isotype specific but are conserved in evolution

Insights on Droplet Digital PCR-Based Cellular Kinetics and Biodistribution Assay Support for CAR-T Cell Therapy

Characterizing in vivo cellular kinetics and biodistribution of chimeric antigen receptor T (CAR-T) cells is critical for toxicity assessment, nonclinical and clinical efficacy studies. To date, the standardized assay to characterize CAR-T cell distribution, expansion, contraction, and persistence profiles is not readily available. To overcome this limitation and increase comparability among studies, we have established a universal protocol for analysis. We established a duplexing ddPCR protocol for the CAR-T transgene and reference gene to normalize the genomic DNA input prepared from mouse blood and tissues. The high-throughput gDNA extraction method enabled highly reproducible gDNA extraction while eliminating labor-intensive steps. The investigational CAR-T cells were intravenously injected into immunodeficient mice bearing human colorectal cancer xenografts. The blood and tissue samples were collected to measure the cellular kinetics by ddPCR and flow cytometry. The standard curves were linear throughout the calibration range with acceptable intra- and inter-day precision and accuracy. The gDNA recovery study performed by spiking in the exo-gene plasmid DNA or CAR-T cells revealed that the recovery ranged from 60 to 100% in blood and tissue homogenates. The use of both units of copy/μg gDNA and copy/μL blood met the current regulatory requirement and allowed for a systematic understanding of CAR-T cell expansion and a direct comparison with the flow cytometry data. A standardized ddPCR assay, including automated gDNA extraction procedures, has been established for evaluating cellular kinetics and biodistribution in CAR-T cell therapies.

Mechanical Roles of F-Actin in the Differentiation of Stem Cells: A Review

In the development and differentiation of stem cells, mechanical forces associated with filamentous actin (F-actin) play a crucial role. The present review aims to reveal the relationship among the chemical components, microscopic structures, mechanical properties, and biological functions of F-actin. Particular attention is given to the functions of the cytoplasmic and nuclear microfilament cytoskeleton and their regulation mechanisms in the differentiation of stem cells. The distributions of different types of actin monomers in mammal cells and the functions of actin-binding proteins are summarized. We discuss how the fate of stem cells is regulated by intra/extracellular mechanical and chemical cues associated with microfilament-related proteins, intercellular adhesion molecules, etc. In addition, we also address the differentiation-induced variation in the stiffness of stem cells and the correlation between the fate and geometric shape change of stem cells. This review not only deepens our understanding of the biophysical mechanisms underlying the fates of stem cells under different culture conditions but also provides inspirations for the tissue engineering of stem cells.

P-Glycoprotein but not Topoisomerase II and Glutathione-S-Transferase-Pi Accounts for Enhanced Intracellular Drug-Resistance in LoVo MDR Human Cell Lines

The biochemical bases of the multidrug-resistant (MDR) phenotype were investigated in drug-resistant sublines derived from LoVo human colon carcinoma cell lines by doxorubicin (DOX) and teniposide (VM26) selection. In addition to P-glycoprotein-mediated drug extrusion through the plasma-membrane, LoVo MDR cells display a further drug-resistance mechanism. That is, to achieve equitoxic effects, LoVo MDR sublines require much higher intracellular drug concentrations than those required by LoVo drug-sensitive parent cell line. Involvement of mdr1, topoisomerase Il and glutathione-S-transferase-pi (GST-π) drug-resistance systems in intracellular drug resistance was investigated. Pharmacologic and biochemical data indicated that intracellular drug resistance in LoVo MDR sublines is uniquely consequent to the drug-transporting property of intracytoplasmic membrane-bound P-glycoprotein molecules which compartment drugs in vacuolelike structures.

Sensitivity Pattern of Normal and Ha-Ras Transformed Nih3T3 Fibroblasts to Antineoplastic Drugs

Ha-ras-transformed NIH3T3 fibroblasts were compared with the parental cell line to investigate the influence of the Ha-ras oncogene on cellular chemosensitivity to antineoplastic drugs. Four NIH3T3 cell clones independently transformed by the Ha-ras oncogene, activated by mutation or overexpression, were analyzed: 3 clones were obtained by transfection of NIH3T3 cells with a mutation-activated Ha-ras gene and 1 clone by transfection of a large copy number of the normal Ha-ras protooncogene. Chemosensitivity of the transformed clones and of the parental cell line was analyzed when cells were in the same condition of proliferative activity and cell cycle phase distribution. No significant differences in chemosensitivity were observed between transformed and untrans-formed cell lines to doxorubicin, VP-16, cis-platinum or mitomycin C. Therefore, data suggest that activated Ha-ras oncogenes have no role in sensitivity to these antineoplastic agents.

Comparison of Six RNA Extraction Methods for the Detection of Classical Swine Fever Virus by Real-Time and Conventional Reverse Transcription–PCR

Six RNA extraction methods, i.e., RNAqueous kit, Micro-to-midi total RNA purification system, NucleoSpin RNA II, GenElute mammalian total RNA kit, RNeasy mini kit, and TRIzol LS reagent, were evaluated on blood and 7 tissues from pig infected with classical swine fever virus (CSFV). Each of the 6 extraction methods yielded sufficient RNA for positive results in a real-time reverse transcription–PCR (RT-PCR) for CSFV, and all RNA, except the one extracted from blood by TRIzol LS reagent, yielded positive results in both a conventional RT-PCR for CSFV and a conventional RT-PCR for an endogenous gene encoding β-actin. The RNA extracted from blood by TRIzol LS reagent became positive in both conventional RT-PCR assays when it was diluted to 1:2, 1:4, or up to 1:64 in nuclease-free water. It is concluded that all 6 methods are more or less useful for the detection of CSFV by real-time and conventional RT-PCR in swine blood and tissues. However, some of the 6 reagents offer certain advantages not common to all 6 extraction procedures. For example, RNA extracted by the TRIzol LS reagent constantly had the highest yield; that by the RNAqueous kit had the highest A260/A280 ratio for almost all samples; and that by the NucleoSpin RNA II and the GenElute mammalian total RNA kit was most likely to be free of contaminations with genomic DNA.

Accurate measurement of mitochondrial DNA deletion level and copy number differences in human skeletal muscle

Accurate and reliable quantification of the abundance of mitochondrial DNA (mtDNA) molecules, both wild-type and those harbouring pathogenic mutations, is important not only for understanding the progression of mtDNA disease but also for evaluating novel therapeutic approaches. A clear understanding of the sensitivity of mtDNA measurement assays under different experimental conditions is therefore critical, however it is routinely lacking for most published mtDNA quantification assays. Here, we comprehensively assess the variability of two quantitative Taqman real-time PCR assays, a widely-applied MT-ND1/MT-ND4 multiplex mtDNA deletion assay and a recently developed MT-ND1/B2M singleplex mtDNA copy number assay, across a range of DNA concentrations and mtDNA deletion/copy number levels. Uniquely, we provide a specific guide detailing necessary numbers of sample and real-time PCR plate replicates for accurately and consistently determining a given difference in mtDNA deletion levels and copy number in homogenate skeletal muscle DNA.

Beta-Actin Is Involved in Modulating Erythropoiesis during Development by Fine-Tuning Gata2 Expression Levels

The functions of actin family members during development are poorly understood. To investigate the role of beta-actin in mammalian development, a beta-actin knockout mouse model was used. Homozygous beta-actin knockout mice are lethal at embryonic day (E)10.5. At E10.25 beta-actin knockout embryos are growth retarded and display a pale yolk sac and embryo proper that is suggestive of altered erythropoiesis. Here we report that lack of beta-actin resulted in a block of primitive and definitive hematopoietic development. Reduced levels of Gata2, were associated to this phenotype. Consistently, ChIP analysis revealed multiple binding sites for beta-actin in the Gata2 promoter. Gata2 mRNA levels were almost completely rescued by expression of an erythroid lineage restricted ROSA26-promotor based GATA2 transgene. As a result, erythroid differentiation was restored and the knockout embryos showed significant improvement in yolk sac and embryo vascularization. These results provide new molecular insights for a novel function of beta-actin in erythropoiesis by modulating the expression levels of Gata2 in vivo.

Expression of EBV-encoded oncogenes and EBV-like virions in multiple canine tumors

Epstein-Barr virus (EBV) is a ubiquitous human oncovirus. Previous studies by us and others have indicated that pet dogs frequently encounter EBV or EBV-related viral infection. In this study, we explored whether EBV is involved in canine malignancies in dogs. EBV-specific BamHI W sequence was detected by polymerase chain reaction (PCR) in 10 of 12 canine tumor specimens, including 8 of 10 oral tumors. Using reverse transcription-PCR, gene expressions of latent membrane protein 1 (LMP 1) and BamHI H rightward reading frame 1 (BHRF1) were identified in 8 and 7 of 12 specimens, respectively. A novel LMP1 variant, T0905, was predominant in 5 canine tumor specimens and found to exist in EBV positive human BC-2 cells. Another LMP1 variant, T0902, was similar to human tumor variant JB7. The BHRF1 sequence identified from these canine tumors was identical to that of the B95-8 viral strain. LMP1 protein and EBV-encoded RNA (EBER) were detected by immunohistochemistry and fluorescent in situ hybridization, respectively, in several tumors, particularly in tumor nests of oral amelanotic melanomas. Furthermore, EBV-like virions adopting a herpesvirus egress pathway were detected in a canthal fibroblastic osteosarcoma and an oral amelanotic melanoma. In conclusion, we report the expressions of BHRF1 transcript (a viral anti-apoptotic protein), LMP1 (a viral oncoprotein) transcript and protein, EBER (a viral oncogenic RNA), and EBV-like virions in multiple canine tumors. The identity of BHRF1 and the resemblance of LMP1 variants between canine and human tumors indicate either a close evolutionary relationship between canine and human EBV, or the possibility of zoonotic transmission.

Plant vegetative and animal cytoplasmic actins share functional competence for spatial development with protists

Actin is an essential multifunctional protein encoded by two distinct ancient classes of genes in animals (cytoplasmic and muscle) and plants (vegetative and reproductive). The prevailing view is that each class of actin variants is functionally distinct. However, we propose that the vegetative plant and cytoplasmic animal variants have conserved functional competence for spatial development inherited from an ancestral protist actin sequence. To test this idea, we ectopically expressed animal and protist actins in Arabidopsis thaliana double vegetative actin mutants that are dramatically altered in cell and organ morphologies. We found that expression of cytoplasmic actins from humans and even a highly divergent invertebrate Ciona intestinalis qualitatively and quantitatively suppressed the root cell polarity and organ defects of act8 act7 mutants and moderately suppressed the root-hairless phenotype of act2 act8 mutants. By contrast, human muscle actins were unable to support prominently any aspect of plant development. Furthermore, actins from three protists representing Choanozoa, Archamoeba, and green algae efficiently suppressed all the phenotypes of both the plant mutants. Remarkably, these data imply that actin's competence to carry out a complex suite of processes essential for multicellular development was already fully developed in single-celled protists and evolved nonprogressively from protists to plants and animals.

Nuclear and membrane expression of the angiogenesis regulator delta-like ligand 4 (DLL4) in normal and malignant human tissues

AIMS

Delta-like ligand 4 (DLL4) is one of five known Notch ligands in mammals and interacts predominantly with Notch 1. DLL4 is induced by vascular endothelial growth factor (VEGF) and acts downstream of VEGF as a 'brake' on VEGF-induced vessel growth, forming an autoregulatory negative feedback loop inactivating VEGF. This action was believed to occur only in vascular development, raising hopes that DLL4 could be a specific drug target for controlling vessel growth in tumours and other pathological conditions. Our aim was to pursue this by raising a monoclonal antibody to the internal domain of DLL4 and assess its distribution in normal and malignant tissues in comparison with antibodies against the external domain of DLL4.

METHODS AND RESULTS

The anti-DLL4 monoclonal antibody was raised using conventional mouse hybridoma techniques. The antibody has been fully characterized by Western blotting and transfectant immunostaining. It has also been comprehensively compared with other antibodies against both the internal and external domains of DLL4. The antigen is widely expressed on human tissues not only on endothelium but also on epithelium and stromal cells. Indeed, in our comprehensive survey only pulmonary alveoli failed to express DLL4. Of a wide range of malignancies, most also expressed DLL4 on tumour cells with a predominantly cytoplasmic pattern, although a number also displayed nuclear positivity.

CONCLUSIONS

Contrary to previous beliefs, DLL4 is widely distributed in tissues other than vessels including many malignancies. Furthermore, the molecule is internalized on binding its receptor and often transported to the nucleus. These findings raise many interesting possibilities for further study of DLL4 and its potential as a therapeutic target.

Prostaglandin E2 induces hypertrophic changes and suppresses alpha-skeletal actin gene expression in rat cardiomyocytes

Prostaglandin E2 (PGE2) is a potent lipid mediator in a diverse range of biological processes. This study examined the hypertrophic effect of PGE2 in primary cultured rat neonatal cardiomyocytes. PGE2 increased total protein synthesis in a dose-dependent manner, as measured by [3H]-phenylalanine uptake. PGE2 increased the cell size and surface area and induced the reorganization of myofilaments. Phosphorylation of the p42/44 and p38 mitogen-activated protein kinases (MAPK) was also induced by PGE2, and U0126 [a mitogen-activated extracellular signal regulated kinase kinase (MEK) 1/2 inhibitor] significantly inhibited the PGE2-induced protein synthesis. Expression of the hypertrophic marker genes, atrial natriuretic peptide and brain natriuretic peptide, was increased by PGE2, but expression of the alpha-skeletal actin gene was significantly attenuated. Transcripts for all 4 PGE2 receptor subtypes (EP1, EP2, EP3, and EP4) were detected in the cardiomyocytes. AE3-208 (an EP4-selective antagonist) significantly inhibited the alpha-skeletal actin gene suppression induced by PGE2, whereas SC51322 (an EP1-selective antagonist) did not. In conclusion, PGE2 induced hypertrophic changes in cardiomyocytes and attenuated alpha-skeletal actin gene expression in part via EP4.

Hypoxia-inducible factor-1alpha mRNA contains an internal ribosome entry site that allows efficient translation during normoxia and hypoxia

HIF-1alpha is the regulated subunit of the HIF-1 transcription factor, which induces transcription of a number of genes involved in the cellular response to hypoxia. The HIF-1alpha protein is rapidly degraded in cells supplied with adequate oxygen but is stabilized in hypoxic cells. Using polysome profile analysis, we found that translation of HIF-1alpha mRNA in NIH3T3 cells is spared the general reduction in translation rate that occurs during hypoxia. To assess whether the 5'UTR of the HIF-1alpha mRNA contains an internal ribosome entry site (IRES), we constructed a dicistronic reporter with the HIF-1alpha 5'UTR inserted between two reporter coding regions. We found that the HIF-1alpha 5'UTR promoted translation of the downstream reporter, indicating the presence of an IRES. The IRES had activity comparable to that of the well-characterized c-myc IRES. IRES activity was not affected by hypoxic conditions that caused a reduction in cap-dependent translation, and IRES activity was less affected by serum-starvation than was cap-dependent translation. These data indicate that the presence of an IRES in the HIF-1alpha 5'UTR allows translation to be maintained under conditions that are inhibitory to cap-dependent translation.

beta- and gamma-actin genes differ in their mechanisms of down-regulation during myogenesis

During the differentiation of myoblasts to form myotubes, the expression patterns of the different actin isoforms change. The cytoplasmic actins, beta and gamma, are down-regulated and the muscle specific isoforms are up-regulated. The region responsible for the down-regulation of the beta-actin gene has been located in the 3'end of the gene. Since the beta- and gamma-actin genes arose from a gene duplication (Erba et al. [1988] J. Cell. Biol. 8:1775-1789), it is possible that the region responsible for down-regulation of the gamma-actin gene may also be in the 3'end of the gene. We have tested this by transfection of human gamma-actin gene constructs into myogenic C2 cells. To our surprise, we found that the region responsible for down-regulation of the gamma-actin gene during differentiation is not in the 3' end of the gene in contrast to that for beta-actin. Rather, we found that intron III is required for appropriate down-regulation of gamma-actin during myogenesis. Intron III containing transcripts from the gamma-actin gene were also found to accumulate during myogenesis. We, therefore, propose that excision of intron III from the primary transcript is inhibited during myogenesis resulting in degradation of the RNA. Removal of intron III from the gene allows it to escape this regulatory mechanism.

BENE, a novel raft-associated protein of the MAL proteolipid family, interacts with caveolin-1 in human endothelial-like ECV304 cells

The MAL proteolipid, an integral protein present in glycolipid- and cholesterol-enriched membrane (GEM) rafts, is an element of the machinery necessary for apical sorting in polarized epithelial Madin-Darby canine kidney cells. MAL was the first member identified of an extended family of proteins that have significant overall sequence identity. In this study we have used a newly generated monoclonal antibody to investigate an unedited member of this family, named BENE, which was found to be expressed in endothelial-like ECV304 cells and normal human endothelium. Human BENE was characterized as a proteolipid protein predominantly present in GEM rafts in ECV304 cells. Coimmunoprecipitation experiments revealed that BENE interacted with caveolin-1. Confocal immunofluorescence and electron microscopic analyses indicated that BENE mainly accumulated into intracellular vesicular/tubular structures that partially colocalize with internal caveolin-1. In response to cell surface cholesterol oxidation, BENE redistributed to the dilated vesicular structures that concentrate most of the caveolin-1 originally on the cell surface. After cessation of cholesterol oxidation, a detectable fraction of the BENE molecules migrated to the plasmalemma accompanying caveolin-1 and then returned progressively to its steady state distribution. Together, these features highlight the BENE proteolipid as being an element of the machinery for raft-mediated trafficking in endothelial cells.

Nucleotide sequence of the mouse VEGF 3'UTR and quantitative analysis of sites of polyadenylation

Sequencing of rat and human vascular endothelial growth factor (VEGF) cDNA clones has previously identified a 3' untranslated region of approximately 1.9 kb, although the apparent site of polyadenylation differed in the two species, despite a high degree of sequence conservation in the region. Neither site is preceded by a canonical AAUAAA polyadenylation signal, a situation frequently found in genes that are subject to alternative polyadenylation. We have sequenced 2.25 kb of the 3' region of the mouse VEGF gene and mapped the usage of potential polyadenylation sites in fibroblasts cultured under both normoxic and hypoxic conditions. We find that two sites for polyadenylation are present in the mouse VEGF gene but the majority of transcripts contain the longer form of the 3'UTR and that their usage is not effected by environmental oxygen tension.

Telomerase activity by TRAP assay and telomerase RNA (hTR) expression are predictive of outcome in neuroblastoma

BACKGROUND

Recent studies have associated telomerase with prognostic factors and survival in neuroblastoma.

PROCEDURE

We examined telomerase activity by telomere repeat amplification protocol (TRAP) and expression of the RNA component of telomerase (hTR) by Northern blotting in 106 primary neuroblastoma tumors and 22 established cell lines.

RESULTS

Overall survival at 5 years for all 106 tumors was significantly better for patients with undetectable TRAP (75% vs. 59%; P = 0.03) or low hTR expression (84% vs. 43%; P < 0.0001), and especially for patients whose tumors had both low hTR expression and undetectable TRAP (all patients, 91% vs. 54%, P = 0.0002; for 17 stage IV-S tumors, 100% vs. 72%, P = 0.04). Strong expression of hTR was seen in 22 cell lines from aggressive tumors, and all maintained telomere length, but 3/22 were TRAP negative.

CONCLUSIONS

These data suggest that both hTR expression and telomerase activity via the TRAP assay should be performed concurrently to predict survival in neuroblastoma patients, particularly in stage 4-S.

Retinoic acid induces persistent, RARalpha-mediated anti-proliferative responses in Epstein-Barr virus-immortalized b lymphoblasts carrying an activated C-MYC oncogene but not in Burkitt's lymphoma cell lines

We have previously demonstrated that 13-cis-retinoic acid (RA), 9-cis-RA and all-trans-RA (ATRA) powerfully inhibit the proliferation of Epstein-Barr virus-immortalized B-lymphoblastoid cell lines (LCLs). The aim of the present study was to assess whether these compounds are effective at inhibiting the growth of B cells at more advanced stages of lymphomagenesis, including fully transformed B lymphocytes. To this end, c-myc-transfected LCLs (myc-LCLs) and Burkitt's lymphoma (BL) cell lines were used. We report that 13-cis-RA, 9-cis-RA and ATRA also markedly inhibit the proliferation of myc-LCLs by inducing G(0)/G(1) growth arrest as well as enhancing rates of apoptosis. Conversely, all but 1 (DG75) of the 8 BL cell lines investigated were poorly RA-responsive. Moreover, unlike LCLs and myc-LCLs, RA-treated DG75 cells rapidly resumed proliferation upon drug removal. Analysis of cell cycle-regulatory proteins showed that, as in LCLs, strong up-regulation of p27(Kip-1) and increased levels of under-phosphorylated pRb and p130 were detected in RA-treated DG75 cells. While the catalytic activity of all 3 G(1)-associated CDKs (CDK2, CDK4 and CDK6) was strongly inhibited in RA-treated LCLs, only CDK2-associated kinase activity was reduced in DG75 cells arrested in G(0)/G(1) by RA. Moreover, RA-treated DG75 cells failed to show the down-regulation of cyclin D3 observed in LCLs. Use of receptor-selective agonists and antagonists showed that in LCLs and RA-responsive BL cells, RA-induced growth arrest is mainly mediated by RARalpha. The RARalpha-selective agonist Ro 40-6055 was also effective at very low concentrations (10(-10) M). Nevertheless, comparable levels of RARalpha mRNA were found in RA-responsive and -resistant BL cell lines, indicating that mechanisms different from transcriptional deregulation of RARalpha probably underlie the differential responsiveness of BL cells.

Role of TNFalpha in regulation of myeloperoxidase expression in irradiated HL60 promyelocytic cells

Irradiation increases the generation of reactive oxygen intermediates, including hydrogen peroxide (H(2)O(2)). Myeloperoxidase (MPO), a heme-containing glycoprotein located in the primary granules of polymorphonuclear leukocytes and monocytes, reacts with H(2)O(2) and halide ion and produces a more potent microbicidal oxidant, hypochlorous acid (HOCl). Human HL60 promyelocytes constitutively had high levels of MPO protein and mRNA. Irradiation decreased the levels of MPO transcripts; the decrease in MPO transcripts by irradiation occurred in an almost dose-dependent manner. HL60 cells produce tumor necrosis factor alpha (TNFalpha), and irradiation markedly increased the TNFalpha production in these cells; in turn, TNFalpha decreased the levels of MPO transcripts in these cells. Furthermore, treatment of cells with anti-TNFalpha antibody blocked the reduction of MPO by irradiation. We also found that irradiation decreased the levels of the MPO mRNA with concomitant increased levels of TNFalpha mRNA in differentiation-induced HL60 cells and human THP-1 monocytic cells. Irradiation reduced the rate of MPO transcription but had only a slight effect on the half-life of MPO mRNA in HL60 cells. Our results suggest that irradiation reduces the steady-state levels of MPO mRNA mainly at transcriptional level and the endogenous production of TNFalpha is required for the reduction by irradiation in HL60 cells.

A subpopulation of cardiomyocytes expressing alpha-skeletal actin is identified by a specific polyclonal antibody

The NH(2)-terminal decapeptide of alpha-skeletal actin that contains a primary sequence specific for this isoform was used to raise a polyclonal antibody in rabbits. Using sequential affinity chromatography, we recovered from serum antibodies reacting exclusively with alpha-skeletal actin when tested by immunoblotting and immunofluorescence. Epitope mapping by means of competition assays with synthetic peptides indicated that the acetyl group and the first 9 amino acids are essential for specificity. The monospecific antibody was then used to investigate the distribution of alpha-skeletal actin in the myocardium of newborn and normal or hypertensive (with or without fibrotic areas) adult rats. Immunostaining of normal heart revealed that alpha-skeletal actin is diffusely distributed within practically all myocardial fibers of the newborn rat, whereas it is restricted to a small proportion of adult rat cardiomyocytes, which appear intensely stained. A correlation, albeit not complete, was found between the distribution of alpha-skeletal actin and beta-myosin heavy chain. During cardiac hypertrophy induced by aortic ligature between the renal arteries, the expressions of alpha-skeletal actin mRNA and protein were increased. The distribution of immunostaining had a focal pattern similar to that of normal adult rats, reactive fibers being more numerous and more intensely stained compared with normal myocardium. Positive fibers were particularly abundant at the periphery of fibrotic areas. Using this antibody, we have demonstrated for the first time the differential distribution of alpha-skeletal actin in heart tissues. Changes in the distribution of this isoform in hypertrophic heart provide new insight into the mechanisms by which the heart adapts to work overload. This antibody will prove useful in exploring the mechanisms of expression of alpha-skeletal actin and in defining its role in physiological and pathological situations.

Rat liver myofibroblasts and hepatic stellate cells: different cell populations of the fibroblast lineage with fibrogenic potential

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered the principal matrix-producing cells of the damaged liver. However, other cell types of the fibroblast lineage that have not yet been characterized are also involved in liver tissue repair and fibrogenesis.

METHODS

We established cultures of cells of the fibroblast lineage, termed rat liver myofibroblasts, and analyzed their phenotypical and functional properties in comparison with HSCs.

RESULTS

HSCs and rat liver myofibroblasts were discernible by morphological criteria and growth behavior. Prolonged subcultivation of rat liver myofibroblasts was achieved, but HSCs were maintained in culture at maximum until second passage. HSCs were characterized by expression of glial fibrillary acidic protein, desmin, and vascular cell adhesion molecule 1, which were almost completely absent in rat liver myofibroblasts. For synthetic properties, HSCs and rat liver myofibroblasts displayed mostly overlapping properties with 4 striking differences. The complement-activating protease P100 and the protease inhibitor alpha(2)-macroglobulin were preferentially expressed by HSCs, whereas interleukin 6-coding messenger RNAs and the extracellular matrix protein fibulin 2 were almost exclusively detectable in rat liver myofibroblasts.

CONCLUSIONS

The data show that morphologically and functionally different fibroblastic populations, HSCs and rat liver myofibroblasts, can be derived from liver tissue. HSCs may not represent the single matrix-producing cell type of the fibroblast lineage in the liver.

Increased expression of plasminogen activator and plasminogen activator inhibitor during liver fibrogenesis of rats: role of stellate cells

BACKGROUND/AIMS

Plasminogen activators and plasminogen activator inhibitors are important regulators of the balance between the proteolytic and antiproteolytic activities that determine extracellular matrix turnover. We examined the expression of plasminogen activator-plasmin system components in experimental liver fibrosis of rats.

METHODS

Liver fibrosis was produced in rats by injecting carbon tetrachloride for 6 to 12 weeks. Gene expression for plasminogen activator inhibitor-1 (PAI-1), urokinase and tissue plasminogen activators (uPA and tPA), urokinase plasminogen activator receptor (uPAR), and transforming growth factor-beta1 (TGF-beta1) was examined by Northern analysis. Western analysis was performed to detect protein expression of PAI-1, uPA and uPAR. An immunohistochemical study was performed to detect the localization of PAI-1. Additionally, primary cultured liver cells were examined by Northern and Western analyses for this protein with or without prior incubation with TGF-beta1.

RESULTS

At 6 weeks, when fibrosis had occurred, uPA and uPAR mRNAs had increased 2.8-fold and 1.8-fold, respectively; PAI-1 and tPA mRNA levels were unchanged. At the cirrhotic stage (9 to 12 weeks), mRNA levels for PAI-1, uPA, uPAR and tPA were all increased. Western analysis also showed increased uPA and uPAR expressions in fibrotic liver, and increased PAI-1, uPA and uPAR expressions in cirrhotic liver. PAI-1 protein was also demonstrated immunohistochemically along sinusoids, vessels, and bile duct cells of normal and fibrotic liver. In liver cell cultures, Kupffer cells, hepatocytes, and especially stellate cells, expressed PAI-1. Expression was enhanced in stellate cells cultured from fibrotic or cirrhotic liver or stimulated in vitro with TGF-beta1.

CONCLUSION

Though increased uPA and uPAR may act on matrix degradation in fibrotic liver, increased PAI-1 together with uPA, uPAR and tPA are associated with overall inhibition of matrix degradation in cirrhotic liver. Hepatic stellate cells are an important source of PAI-1 during liver fibrosis.

Cultured porcine coronary artery smooth muscle cells. A new model with advanced differentiation

Arterial intimal thickening after endothelial injury induced in rodents has proven to be a relatively unreliable model of restenosis for testing clinically useful compounds. The same has been found for cultured rat or rabbit vascular smooth muscle cells (SMCs). To test alternative possibilities, we have studied several differentiation features of porcine coronary artery SMCs, cultured up to the 5th passage after enzymatic digestion of the media. The effects of heparin, transforming growth factor (TGF)-beta1 or TGF-beta2, and all-trans-retinoic acid (tRA) on proliferation, migration, and differentiation of these cells also were examined. Porcine arterial SMCs in culture not only express high levels of alpha-smooth muscle (SM) actin but, contrary to rodent SMCs, also maintain an appreciable expression of SM myosin heavy chain isoforms 1 and 2, desmin, and smoothelin, a recently described late differentiation marker of vascular SMCs. We demonstrate for the first time that smoothelin is colocalized with alpha-SM actin in these cells. Finally, we show that in the porcine model, heparin is more potent than TGF-beta1 or TGF-beta2 and tRA in terms of inhibition of proliferation and migration and of increasing the expression of differentiation markers. This model should be a useful complement to in vivo studies of SMC differentiation and of pathological situations such as restenosis and atheromatosis.

Hypoxic regulation of vascular endothelial growth factor mRNA stability requires the cooperation of multiple RNA elements

Vascular endothelial growth factor (VEGF) is a key regulator of developmental, physiological, and tumor angiogenesis. Upregulation of VEGF expression by hypoxia appears to be a critical step in the neovascularization of solid cancers. The VEGF mRNA is intrinsically labile, but in response to hypoxia the mRNA is stabilized. We have systematically analyzed the regions in the VEGF mRNA that are responsible for its lability under normoxic conditions and for stabilization in response to hypoxia. We find that the VEGF mRNA not only contains destabilizing elements in its 3' untranslated region (3'UTR), but also contains destabilizing elements in the 5'UTR and coding region. Each region can independently promote mRNA degradation, and together they act additively to effect rapid degradation under normoxic conditions. Stabilization of the mRNA in response to hypoxia is completely dependent on the cooperation of elements in each of the 5'UTR, coding region, and 3'UTR. Combinations of any of two of these three regions were completely ineffective in responding to hypoxia, whereas combining all three regions allowed recapitulation of the hypoxic stabilization seen with the endogenous VEGF mRNA. We conclude that multiple regions in the VEGF mRNA cooperate both to ensure the rapid degradation of the mRNA under normoxic conditions and to allow stabilization of the mRNA in response to hypoxia. Our findings highlight the complexity of VEGF gene expression and also reveal a mechanism of gene regulation that could become the target for strategies of therapeutic intervention.

Spatial distribution of tissue inhibitor of metalloproteinase-1 mRNA in chronic liver disease

BACKGROUND/AIMS

Tissue inhibitor of metalloproteinase-1, a specific inhibitor of matrix metalloproteinases, plays an important role in the pathogenesis of fibrosis and tumor progression. However, the precise expression of tissue inhibitor of metalloproteinase-1 messenger RNA in human hepatic fibrosis has not yet been defined. We investigated the spatial distribution of tissue inhibitor of metalloproteinase-1 messenger RNA in chronic human liver disease.

METHODS

Northern and in situ hybridization of probes to tissue inhibitor of metalloproteinase-1 messenger RNA were performed in specimens from 16 surgically resected human livers. Immunohistochemical staining of sections for tissue inhibitor of metalloproteinase-1 and immunoelectron microscopy were also performed.

RESULTS

Northern hybridization demonstrated that expression of tissue inhibitor of metalloproteinase-1 messenger RNA was increased 3.9-fold in mild chronic hepatitis, 6.8-fold in moderate chronic hepatitis, and 6.4-fold in cirrhosis, compared with control liver. In situ hybridization showed the expression of tissue inhibitor of metalloproteinase-1 messenger RNA in spindle-shaped cells in the fibrous septa and lobules in chronic hepatitis and cirrhosis; these cells were immunohistochemically positive for a-smooth muscle actin. Immunoelectron microscopy revealed localization of tissue inhibitor of metalloproteinase-1 in between fibers, to the rough endoplasmic reticula of stellate cells located in the lobules and periportal areas, and to fibroblasts in the fibrous septa. These results indicate that tissue inhibitor of metalloproteinase-1 was produced mainly by stellate cells in the specimens of chronic liver diseases.

CONCLUSIONS

Expression of tissue inhibitor of metalloproteinase-1 messenger RNA is increased in hepatic fibrosis and stellate cells are involved primarily in its expression.

Expression of matrix metalloproteinase-13 and tissue inhibitor of metalloproteinase-1 in acute liver injury

BACKGROUND/AIMS

Matrix metalloproteinase-13, one of the principal neutral proteinases capable of cleaving native fibrillar collagens, is important in the degradation and remodeling of extracellular matrix. However, its precise expression in liver injury has not been characterized. We examined the kinetics of the expression of matrix metalloproteinase-13 and one of its specific inhibitors, tissue inhibitor of metalloproteinase-1, in acute liver injury in rats.

METHODS

Acute liver injury was induced by administration of carbon tetrachloride or two different doses of D-galactosamine hydrochloride in Wistar rats. Hepatic matrix metalloproteinase-13 and tissue inhibitor of metalloproteinase-1 mRNA levels were then examined by Northern blotting.

RESULTS

All rats survived after liver injury induced by carbon tetrachloride or low doses of D-galactosamine hydrochloride. However, rats died 5 days after induction of liver injury by high doses of D-galactosamine hydrochloride. In carbon tetrachloride-induced liver injury, matrix metalloproteinase-13 mRNA was transiently increased between 6 h and 1 day after injury. Tissue inhibitor of metalloproteinase-1 mRNA expression was increased between 6 h and 3 days after the peak of matrix metalloproteinase-13 expression. Similar patterns of matrix metalloproteinase-13 and tissue inhibitor of metalloproteinase-1 expression were observed in low-dose D-galactosamine hydrochloride-induced liver injury. In contrast, in high-dose D-galactosamine hydrochloride-induced liver injury, tissue inhibitor of metalloproteinase-1 expression peaked before matrix metalloproteinase-13 expression, which was increased 2 days after injury. Both mRNA levels continued to increase until death.

CONCLUSIONS

Transient expression of matrix metalloproteinase-13, followed by that of tissue inhibitor of metalloproteinase-1, was observed during recovery from acute liver injury induced by carbon tetrachloride and low-dose D-galactosamine hydrochloride. In contrast, disordered expression of matrix metalloproteinase-13 was observed in fatal liver injury caused by high-dose D-galactosamine hydrochloride. These results indicate that matrix metalloproteinase13 plays an important role in the early phase of recovery from liver injury.

Endothelial cell integrin alpha5beta1 expression is modulated by cytokines and during migration in vitro

Alterations in endothelial cell-extracellular matrix interactions are central to the process of angiogenesis. We have investigated the effect of wound-induced two-dimensional migration, basic fibroblast growth factor (bFGF), transforming growth factor-beta1 (TGF-beta1) and leukemia inhibitory factor (LIF) on expression of the alpha5beta1 integrin in endothelial cells. In multiple-wounded monolayers of bovine microvascular endothelial (BME) cells, an increase in mRNA and total protein for both alpha5 and beta1 subunits was observed, and this could be correlated with a reduction in cell density but not proliferation, both of which are induced following wounding. Although as previously reported, the alpha5 subunit was increased when cells were exposed to TGF-beta1 alone, co-addition of bFGF and TGF-beta1 resulted in a striking synergistic induction of alpha5, with no significant changes in the expression of beta1. In contrast, the alpha5 subunit was decreased by LIF in bovine aortic endothelial but not in BME cells. These findings suggest that quantitative alterations in alpha5 and beta1 integrin subunit expression modulate the adhesive and migratory properties of endothelial cells during angiogenesis.

Differential brain expression of a new beta-actin gene from zebrafish (Danio rerio)

It has been shown that actin genes exhibit distinct tissue and stage-specific patterns of expression. We have cloned a new beta-actin gene from the teleost zebrafish (Danio rerio), a well-established model for developmental studies, and analysed its expression by Northern blot and in situ hybridization studies. Our results suggest that in adult brain zebrafish, this new gene is expressed during neuronal cell proliferation.

Expression and regulation of cell adhesion molecules by hepatic stellate cells (HSC) of rat liver: involvement of HSC in recruitment of inflammatory cells during hepatic tissue repair

Hepatic stellate cells (HSC), a pericyte-like nonparenchymal liver cell population, are regarded as the principal matrix-synthesizing cells of fibrotic liver. They might also play a role during liver inflammation. The present study analyzed (i) expression of cell adhesion molecules (CAMs) mediating cell infiltration, like intercellular adhesion molecule-1 (I-CAM-1) and vascular cell adhesion molecule-1 (V-CAM-1), by HSC, (ii) CAM regulation in HSC by growth factors and inflammatory cytokines, and (iii) CAM expression in situ during liver inflammation, using immunochemistry and Northern blot analysis. I-CAM-1 and V-CAM-1 expression was present in HSC in vitro and in cells located in the sinusoidal/perisinusoidal area of normal liver. Growth factors, eg, transforming growth factor-beta1, down-regulated I-CAM-1- and V-CAM-1-coding mRNAs and stimulated N-CAM expression of HSC. In contrast, inflammatory cytokines like tumor necrosis factor-alpha reduced N-CAM-coding mRNAs, whereas induction of I-CAM-1- and V-CAM-1-specific transcripts increased several fold. In situ, messengers specific for I-CAM-1 and V-CAM-1 were induced 3 hours after CCl4 treatment (thereby preceding mononuclear cell infiltration starting at 12 hours), were expressed at maximal levels 9-12 hours after CCl4 application, and decreased afterwards. I-CAM-1 and V-CAM-1 immunoreactivity increased in a linear fashion starting 3 hours after CCl4-induced liver injury, was detected in highest amounts at 24-48 hours characterized by maximal cell infiltration, and returned to baseline values at 96 hours. Interestingly, the induction/repression of CAM-specific messengers paralleled the time kinetics of tumor necrosis factor-alpha transforming growth factor-beta1 expression in injured liver. HSC might be important during the onset of hepatic tissue injury as proinflammatory elements and might interact with I-CAM-1 and V-CAM-1 ligand-bearing cells, namely lymphocyte function-associated antigen-1- or Mac-1/very late activation antigen-4-positive inflammatory cells, thereby modulating the recruitment and migration of mononuclear cells within the perisinusoidal space of diseased livers.

MAL, a novel integral membrane protein of human T lymphocytes, associates with glycosylphosphatidylinositol-anchored proteins and Src-like tyrosine kinases

A large fraction of glycosylphosphatidylinositol (GPI)-anchored proteins and Src-like kinases are confined to glycolipid-enriched membrane (GEM) microdomains. The particular membrane topology of GPI-anchored proteins has led to the postulation of the existence of integral membrane proteins linking extracellular stimuli with cytosolic machinery for endocytosis and signaling. The human MAL cDNA was identified during a search for novel genes differentially expressed during T cell development, and encodes a multispanning membrane protein displaying lipid-like properties. To address the biochemical characterization of endogenous MAL and to analyze its possible association with other proteins, we have generated a monoclonal antibody (mAb) specific to the MAL molecule. Using this mAb, we have identified MAL in GEM microdomains of both the HPB-ALL T cell line and human peripheral blood lymphocytes. Co-immunoprecipitation experiments with antibodies to the MAL molecule or to the GPI-anchored CD59 antigen indicated specific association of MAL with GPI-anchored proteins and Src-like tyrosine kinases. In addition, both MAL and the Src-like kinase Lck were identified in GEM obtained from an endosomal-enriched membrane fraction. These features of MAL closely match some of the properties expected for the hypothetical integral membrane linker proteins acting in specialized GEM-mediated functions.

The human proteinase-activated receptor-3 (PAR-3) gene. Identification within a Par gene cluster and characterization in vascular endothelial cells and platelets

Proteolytically activated receptors (PARs) represent an emerging subset of seven transmembrane G protein-coupled receptors that mediate cell activation events by receptor cleavage at distinct scissile bonds located within receptor amino termini. Differential genomic blotting using a yeast artificial chromosome known to contain the PAR-1 and PAR-2 genes identified the PAR-3 gene within a PAR gene cluster spanning approximately 100 kilobases at 5q13. The PAR-3 gene is relatively small (approximately 12 kilobases); and, like the PAR-1 and PAR-2 genes, it displays a two-exon structure, with the majority of the coding sequence and the proteolytic cleavage site contained within the larger second exon. Sequence analysis of the 5'-flanking region demonstrates that the promoter is TATA-less, similar to that seen with PAR-1, with the identification of nucleic acid motifs potentially involved in transcriptional gene regulation, including AP-1, GATA, and octameric sequences. PAR-3 transcripts were apparent in human vascular endothelial cells, although at considerably lower levels than those of PAR-1 and not significantly modulated by the endothelial cell stimulus tumor necrosis factor-alpha. Likewise, although PAR-3 mRNA was evident in human platelets, receptor cell surface expression was modest (approximately 10%) compared with that of PAR-1. Thus, although PAR-3 is postulated to represent a second thrombin receptor, its modest endothelial cell and platelet expression suggest that PAR-3 activation by alpha-thrombin is less relevant for physiological responses in these mature cells. Rather, given its disparately greater expression in megakaryocytes (and megakaryocyte-like human erythroleukemia cells), a regulatory role in cellular development (by protease activation) could be postulated.

Expression of the MAL gene in the thyroid: the MAL proteolipid, a component of glycolipid-enriched membranes, is apically distributed in thyroid follicles

The MAL proteolipid, an integral membrane protein expressed in T lymphocytes, polarized epithelial MDCK cells, and myelin-forming cells, has been identified as a component of internal glycolipid-enriched membrane (GEM) microdomains. On the basis of its ability to induce vesicle formation by ectopic expression, MAL has been recently proposed as a component of the machinery for GEM vesiculation. Taking into account the proposed role of GEMs in polarized transport, we have investigated the expression of the MAL gene in thyroid cells. Interestingly, MAL messenger RNA species were detected in the human thyroid, whereas they were undetectable in other endocrine glands tested. Moreover, epithelial FRT cells, a polarized rat cell line of thyroid origin, also expressed MAL transcripts. Immunohistochemical analysis of thyroid follicles, with a newly developed anti-MAL monoclonal antibody, indicates that MAL distribution is restricted to the apical zone of thyroid epithelial cells. Biochemical analyses, using FRT cells, indicate exclusive residence of MAL in GEM microdomains, and these analyses allowed the identification of MAL as a major protein component of the GEM fraction in this cell line. Our results are consistent with a role for MAL as a component of GEM microdomains in thyroid epithelial cells.

Mast cell collagenase correlates with regression of pulmonary vascular remodeling in the rat

Pulmonary vascular remodeling, produced by cell hypertrophy and extracellular matrix protein synthesis in response to hemodynamic stress, regresses after reduction of blood pressure, possibly by proteolysis of structural proteins. To test this postulate, we assessed the breakdown of extracellular matrix proteins and expression of collagenase and elastase in pulmonary arteries of rats exposed to hypoxia (10% O2 for 10 d) followed by normoxia. During hypoxia, contents of collagen and elastin increased in pulmonary arteries and latent rat interstitial collagenase was expressed without increased collagenolytic activity or mRNA levels. At 3 days after normoxia, collagen and elastin contents decreased coincident with the new appearance of activated collagenase and transient increases in collagenolytic and elastolytic activities. The amount of immunoreactive collagenase, localized predominately in connective tissue-type mast cells, was increased in the adventitia and media of hypertensive vessels. We conclude that mast cells containing latent collagenase are recruited into the outer walls of pulmonary arteries during remodeling. It is possible that mast cell-derived collagenase contributes to collagen breakdown in pulmonary arteries during early recovery from hypoxia and plays a role in restoration of vascular architecture.

Asymmetrical localization of mRNAs in enterocytes of human jejunum

Intracellular localization of specific mRNAs is known to be a mechanism for targeting proteins to specific sites within the cell. Previous studies from this laboratory have demonstrated co-localization of mRNAs and proteins for a number of genes in absorptive enterocytes of fetal rat intestine. The present study was undertaken to examine in human enterocytes the intracellular localization patterns of mRNAs for the microvillous membrane proteins lactase-phlorizin hydrolase (LPH), sucrase-isomaltase (SI), and intestinal alkaline phosphatase (IAP), and the cytoskeletal protein beta-actin. In sections of human jejunum, mRNAs were localized by in situ hybridization using digoxigenin-labeled anti-sense RNA probes. Both LPH and SI mRNAs were localized to the apical region of villous enterocytes, whereas IAP and beta-actin mRNAs were detected both apically and basally relative to the nucleus. Therefore, in contrast to LPH, SI, and beta-actin mRNAs, which co-localize with their encoded proteins, that of IAP is present in the basal region of the cell where IAP protein has not directly been demonstrated to be present. Absorptive enterocytes from humans possess the mechanisms for intracellular mRNA localization, but not all mRNAs co-localize with their encoded proteins.

Osteoblast cytoskeletal modulation in response to mechanical strain in vitro

The structural integrity of microfilaments has been shown to be necessary for the signal transduction of mechanical stimuli within osteoblasts. Qualitative and quantitative changes within the cytoskeleton of osteoblasts may therefore be crucial components of the signal transduction processes of these cells in response to mechanical stimulation. Avian osteoblasts were strained with a device that deforms a flexible, cell-laden membrane at a defined frequency and intensity in a uniform biaxial manner. We examined the effects of mechanical strain on the accumulation of protein and the expression of the major cytoskeletal elements and specific integrin-binding (arginine-glycine-aspartic acid) proteins of these cells. Mechanical strain increased the level of total extracellular matrix-accumulated fibronectin by approximately 150% and decreased that of osteopontin by approximately 60% but had no quantifiable effect on the accumulation of beta1 integrin subunit or collagen type I. An examination of the major elements of the cytoskeleton demonstrated that neither the level of actin nor that of the intermediate filament protein vimentin changed; however, the amount of tubulin decreased by approximately 75% and the amount of vinculin, a major protein of focal adhesion complexes, increased by approximately 250%. An analysis of protein synthesis by two-dimensional gel electrophoresis of [35S]methionine-labeled cytoskeletal proteins demonstrated that the changes in the accumulation of vinculin and tubulin resulted from their altered synthesis. Messenger RNA analysis confirmed that the changes in accumulation and protein synthesis observed for vinculin, fibronectin, and osteopontin were controlled at a pretranslational level. Immunofluorescent microscopy demonstrated that mechanical strain led to increased formation and thickening of actin stress fibers, with a commensurate dissociation in microtubules and a clear increase in levels of vinculin at the peripheral edges of the cells. In conclusion, the elevated rate of synthesis and the increased accumulation of vinculin and fibronectin, as well as the increase in the number and size of stress fibers and focal adhesion complexes, suggest that mechanical strain leads to a coordinated change both in the cytoskeleton and in extracellular matrix proteins that will facilitate tighter adhesion of an osteoblast to its extracellular matrix.

Interferon-gamma and retinoic acid down-regulate N-myc in neuroblastoma through complementary mechanisms of action

The N-myc oncogene plays a key role in the biology of neuroblastoma and the differentiation process. N-myc expression is associated with metastatic disease, as well as the undifferentiated state of normal neuroblasts migrating from the neural crest during embryogenesis. Its down-regulation is a pivotal event in the differentiation of neuroblastoma cells by retinoic acid (RA). Our previous work has shown that RA works synergistically with other agents, such as interferon-gamma (IFN-gamma), to down-regulate N-myc expression and induce differentiation. The present study demonstrates that IFN-gamma, like RA, decreases N-myc transcription. However, functional analysis of N-myc upstream regulatory sequences using 5' deletion mutants of a promoter-CAT construct containing germ line sequences from nucleotide position -887 to +151 showed that IFN-gamma and RA act through different sites on the N-myc promoter. In addition to its transcriptional effect, IFN-gamma was also found to shorten the half-life of N-myc mRNA. Taken together, these findings provide a mechanistic basis for the synergistic action of IFN-gamma and RA in inducing neuroblastoma differentiation and a rationale for the possible development of combination differentiation therapy for clinical use.

Alterations of p16INK4A and p15INK4B genes in gastric carcinomas

BACKGROUND

It has been suggested that cyclin-dependent kinase inhibitors (CDKIs), including p16 and p15, are tumor suppressor genes. Alterations of CDKIs have been found in most types of cancer. However, little is known about the status of p16 and p15 genes, including methylation of the promoter region, in gastric carcinoma.

METHODS

Thirty-six primary gastric tumors and 9 gastric carcinoma cell lines were examined for alterations of the p16 and p15 genes. Deletion of the p16 and p15 genes was assessed by Southern blot analysis, expression by Northern blot analysis, and mutation by polymerase chain reaction-single strand conformation polymorphism followed by direct sequencing. The methylation status of the 5' CpG island of the p16 gene was evaluated using methylation-sensitive restriction enzymes, and reversal of the transcriptional block of the p16 gene was determined by Northern blot analysis after treatment with 5-aza-2'-deoxycytidine.

RESULTS

Homozygous deletions of the p16 and 15 genes from 2 of 9 gastric carcinoma cell lines were found. In contrast, no deletions were detected in 36 primary gastric tumors, and one primary tumor showed rearrangements of the p16 and p15 genes. Two gastric carcinoma cell lines showed a point mutation and an insertional mutation of the p16 gene, respectively; however, no point mutations were noted for the p16 and p15 genes in any of the primary gastric tumors. Constitutive levels of p16 mRNA expression in gastric carcinoma cell lines were quite heterogeneous; four gastric carcinoma cell lines had no detectable p16 mRNA and 6 gastric carcinoma cell lines had negligible expression of p15 mRNA. Of 10 primary gastric tumors, only 1 tumor expressed p16 mRNA. Furthermore, abnormal DNA methylation patterns of the p16 gene were found in 2 gastric carcinoma cell lines through the use of methylation-sensitive restriction enzymes. These cell lines lacked expression of p16 mRNA without deletions of the p16 gene. These transcriptional blocks were reversed by treatment with 5-aza-2'-deoxycytidine.

CONCLUSIONS

Deletions or mutations of the p16 and p15 genes are uncommon in primary gastric carcinomas. However, defective mRNA transcription, sometimes by aberrant DNA methylation, might be one of the pathways of inactivation of the p16 gene that leads to the development of gastric carcinoma.

Alterations of p16INK4A and p15INK4B genes in gastric carcinomas

BACKGROUND

It has been suggested that cyclin-dependent kinase inhibitors (CDKIs), including p16 and p15, are tumor suppressor genes. Alterations of CDKIs have been found in most types of cancer. However, little is known about the status of p16 and p15 genes, including methylation of the promoter region, in gastric carcinoma.

METHODS

Thirty-six primary gastric tumors and 9 gastric carcinoma cell lines were examined for alterations of the p16 and p15 genes. Deletion of the p16 and p15 genes was assessed by Southern blot analysis, expression by Northern blot analysis, and mutation by polymerase chain reaction-single strand conformation polymorphism followed by direct sequencing. The methylation status of the 5' CpG island of the p16 gene was evaluated using methylation-sensitive restriction enzymes, and reversal of the transcriptional block of the p16 gene was determined by Northern blot analysis after treatment with 5-aza-2'-deoxycytidine.

RESULTS

Homozygous deletions of the p16 and 15 genes from 2 of 9 gastric carcinoma cell lines were found. In contrast, no deletions were detected in 36 primary gastric tumors, and one primary tumor showed rearrangements of the p16 and p15 genes. Two gastric carcinoma cell lines showed a point mutation and an insertional mutation of the p16 gene, respectively; however, no point mutations were noted for the p16 and p15 genes in any of the primary gastric tumors. Constitutive levels of p16 mRNA expression in gastric carcinoma cell lines were quite heterogeneous; four gastric carcinoma cell lines had no detectable p16 mRNA and 6 gastric carcinoma cell lines had negligible expression of p15 mRNA. Of 10 primary gastric tumors, only 1 tumor expressed p16 mRNA. Furthermore, abnormal DNA methylation patterns of the p16 gene were found in 2 gastric carcinoma cell lines through the use of methylation-sensitive restriction enzymes. These cell lines lacked expression of p16 mRNA without deletions of the p16 gene. These transcriptional blocks were reversed by treatment with 5-aza-2'-deoxycytidine.

CONCLUSIONS

Deletions or mutations of the p16 and p15 genes are uncommon in primary gastric carcinomas. However, defective mRNA transcription, sometimes by aberrant DNA methylation, might be one of the pathways of inactivation of the p16 gene that leads to the development of gastric carcinoma.

Differential expression of the rat retinoid X receptor gamma gene during skeletal muscle differentiation suggests a role in myogenesis

Even though previous studies have shown that transcripts encoding the murine retinoid X receptor gamma (RXRgamma) are present in skeletal muscle of mouse embryos and that cultured myoblasts are induced to differentiate upon retinoid treatment, a function for RXRgamma and retinoids in mammalian myogenesis has not yet been identified. To begin to understand the possible role of RXRgamma during mammalian myogenesis we isolated novel rat RXRgamma cDNA sequences and examined in detail the spatio-temporal expression pattern of RXRgamma transcripts in relation to skeletal muscle differentiation in rat embryos and cultured myoblasts. We show that the onset of RXRgamma expression coincides with the differentiation of limb myoblasts in vivo. In vitro, RXRgamma is expressed in differentiating myoblasts, but not in proliferating myoblasts. In the myotome, however, RXRgamma is first expressed after myoblast differentiation, with RXRgamma transcripts being confined initially to its ventral region. Subsequently, RXRgamma becomes expressed throughout limb and myotome-derived muscle masses, and by the end of the primary myogenic wave, RXRgamma transcripts are mainly confined to their periphery. This dynamic expression pattern of RXRgamma during myogenesis suggests its possible involvement in the differentiation of limb myoblasts but excludes a role in the differentiation of early myotomal myoblasts.

Telomerase expression in primary neuroblastomas

Maintenance of chromosomal telomeres is necessary for continued cell growth, and this is carried out in germline tissues by telomerase. In contrast to most somatic tissues, many tumours have telomerase activity. The RNA component of human telomerase (hTR) was measured by Northern analyses of 150 primary untreated neuroblastomas and compared with clinical stage at diagnosis. hTR expression > 33 (relative to cell line control = 100) was seen in 41% of all tumours and the frequency of hTR > 33 increased with stage of disease. Expression of hTR may be involved in progression of neuroblastoma.

Increased frequency of P-glycoprotein gene amplification in colchicine-resistant Rat-1 clones transformed by v-src

A rat fibroblast cell line (Rat-1) carrying a temperature-sensitive mutation of v-src was used to determine whether inducible cellular transformation altered the ability of cells to amplify the p-glycoprotein gene in response to colchicine selection. Transformed and nontransformed Rat-1 fibroblasts selected under 4 times the LD50 generated the same number of colchicine-resistant colonies. We next examined colchicine-resistant colonies derived from transformed cells and compared them to colchicine-resistant colonies derived from nontransformed cells. When Rat-1 cells were selected at 35 degrees C (transforming temperature), 7 out of 7 clones exhibited a 3- to 5-fold p-glycoprotein gene amplification. These results contrasted to those found at the nontransforming temperature (40 degrees C); none of the 8 colchicine-resistant clones examined had amplified the p-glycoprotein gene. Thus in Rat-1 cells carrying a temperature-sensitive v-src gene, p-glycoprotein gene amplification was observed at a high frequency only in transformed clones selected at the temperature permissive for v-src activity.

Cloning and sequencing of a full-length sea bream (Sparus aurata) beta-actin cDNA

A full-length cDNA clone encoding beta-actin (beta-actin) was isolated from a sea bream (Sparus aurata) liver cDNA library. Sequencing of this clone reveals an open reading frame encoding a 375 amino acid protein that shares a high degree of conservation to other known actins. The sea bream beta-actin sequence showed 98% identity to carp and human beta-actin and 95% and 94% identity to sea squirt and Dictyostelium cytoplasmic actins, respectively.

Bone morphogenetic protein-6 is expressed in nonparenchymal liver cells and upregulated by transforming growth factor-beta 1

Bone morphogenetic protein-6 (BMP-6) is a member of the TGF-beta superfamily, which controls growth and differentiation during embryogenesis and acts as an osteoinductive factor in the adult organism. In order to gain further insights into the role of BMP-6, the present study analyzed the expression pattern of BMP-6 in adult rat tissues with special emphasis to the liver, since TGF-beta 1, another member of the TGF-beta superfamily, has been shown to play a fundamental role in liver physiology. Rat BMP-6-coding cDNAs were generated by homology cloning using RT-PCR and displayed 89.6 and 83.4% homology to mouse and human BMP-6, respectively. By Northern blotting BMP-6-specific transcripts 3.7 kb in size were detected in major amounts in lung and in minor quantities in spleen, kidney, heart, brain, and liver. Among the different hepatic cell populations tested BMP-6 expression was confined to nonparenchymal liver cells, namely rat hepatic stellate cells (HSC) and Kupffer cells (KC). During primary culture BMP-6 expression was increased in HSC but declined in KC. Interestingly, TGF-beta 1 stimulated BMP-6 expression of HSC especially at an early time point of culture, while interferon-gamma downregulated BMP-6 expression. The detection of BMP-6 transcripts in the liver, the cell-type-restricted expression pattern, and its regulation propose that, in addition to its osteoinductive properties, BMP-6 might play a role in liver growth and differentiation, in particular after tissue damage.

Muscle isoactin expression during in vitro differentiation of murine embryonic stem cells

Embryonic stem (ES) cells are pluripotent cells derived from mouse blastocysts. ES cells can differentiate into complex embryoid bodies (EBs) which exhibit many of the characteristics of 4-10-d embryos, including areas which rhythmically contract. The expression of the four muscle isoactins was examined in EBs by using transcript-specific probes for each of the muscle actin mRNAs and selectively reactive MAbs to muscle actins. Northern blot analyses from undifferentiated ES cells and EBs after 5, 10, 15, and 20 d in suspension culture demonstrated that no muscle actin transcripts could be detected in the undifferentiated cells, whereas during differentiation, the vascular and enteric smooth muscle isoactin mRNAs were easily detected. To further define the pattern of expression polymerase chain reaction analyses were carried out on RNA isolated from individual EBs. The data indicated that all four muscle-specific actin genes are transcribed. We also demonstrated the presence of muscle actins in at least two distinct cell populations within the EBs using selectively reactive MAbs. Fibroblast-like cells exhibit significant levels of the two smooth muscle actins (vascular and enteric) localized to stress fibers. In addition, one or both of the striated muscle actins (cardiac and skeletal) are expressed in cardiomyocyte-like cells. As is the case in embryonic heart, alpha-smooth muscle actin and the striated muscle actin(s) are incorporated into well organized sarcomeres in these cardiomyocyte-like cells. Thus, differentiating EBs provide an in vitro system to study both striated and smooth muscle cell gene expression.

High and low dose rate irradiation have opposing effects on cytokine gene expression in human glioblastoma cell lines

Effects of radiation on five cytokine expressing human glioblastoma cell lines were studied. In comparison to unirradiated controls, IL-1 beta and IL-6 mRNAs were generally reduced after low (LDR, 1.0 cGy/min) and very low (VLDR, 0.35 cGy/min) dose rate irradiation. In contrast, high (HDR, 200 cGy/min) and intermediate (IDR, 4.1 cGy/min) dose rates increased steady-state levels of IL-1 beta and IL-6 mRNAs. The surviving fraction was generally inversely proportional to the dose rate; however, these glioma cells were unusually susceptible to LDR. In the two cell lines tested, IDR was less cytotoxic than either HDR or LDR irradiation. Although cytokine gene expression had no clear effect on radiation survival in vitro, autologous cytokines could be important to radiation response in vivo by affecting immune response, tumour stroma, vasculature or surrounding tissues. Adjusting dose rates to account for inverse dose rate effects and altered gene expression may be a useful strategy in optimising radiation therapy of glioblastomas.

Interferon-gamma regulates collagen and fibronectin gene expression by transcriptional and post-transcriptional mechanisms

Interferon-gamma (IFN-gamma) regulates the expression of collagen and fibronectin genes by molecular mechanisms not completely understood. We investigated the effects of IFN-gamma on the expression of the genes encoding alpha 1 (I) procollagen (COL1A1), alpha 1 (III) procollagen (COL3A1), and fibronectin (FN) in cultured normal human lung fibroblasts. Labeled newly synthesized proteins were analysed by electrophoresis, mRNA levels and stability by Northern hybridizations, and transcription rates by in vitro assays. IFN-gamma caused a reduction in the production of alpha 1 (I) and alpha 1 (III) procollagens and of fibronectin. The reduction in the production of procollagen chains was shown to result from a combination of IFN-gamma-induced inhibition of the transcription rates of the COL1A1 and COL3A1 genes and destabilization of the corresponding transcripts. IFN-gamma increased the transcription rate of FN, but also decreased the stability of the corresponding transcripts. The net results indicate that the regulation of the expression of extracellular matrix genes by IFN-gamma is a complex process that involves changes in gene transcription rates, alterations in mRNAs stability, and possibly, modulation of the rates of translation.

Anti-cancer agent OK432 induces manganese superoxide dismutase in human granulocytes

Manganese superoxide dismutase (MnSOD) is a mitochondrial enzyme involved in scavenging O2-. OK432, a Streptococcal preparation, has anti-tumor activity and is also known to be a biological-response modifier. In this study, we have examined the regulation of MnSOD gene by OK432 in human granulocytes. Granulocytes had a low activity of MnSOD; OK432 increased MnSOD mRNA levels in a dose-dependent manner and its activity in granulocytes. OK432 also induced the MnSOD mRNA in HL60 promyelocytes, while not affecting the levels of MnSOD mRNA in human fibroblasts. Pre-treatment with either actinomycin D or cycloheximide inhibited the induction of MnSOD mRNA by OK432. OK432 increased the levels of interleukin-1 (IL-1) and tumor-necrosis-factor-alpha (TNFalpha) mRNA in granulocytes. Furthermore, the induction of MnSOD mRNA by OK432 was blocked by anti-IL-1 antibody but not by anti-TNF antibody. These results suggest that the induction of MnSOD mRNA by OK432 is regulated at the transcriptional level, and OK432 induces MnSOD mRNA, at least in part, through production of IL-1 in granulocytes.

Regional delivery of an adenovirus vector containing the Escherichia coli cytosine deaminase gene to provide local activation of 5-fluorocytosine to suppress the growth of colon carcinoma metastatic to liver

To evaluate the hypothesis that regional delivery of an adenovirus vector containing the Escherichia coli cytosine deaminase gene (AdCMV.CD) together with systemic 5-FC could suppress the growth of metastatic colon cancer in the liver, the AdCMV.CD vector was injected 0.8-1 cm from the site of a human colon cancer tumor in the livers of nude mice. The growth of the human colon cancer cells was quantified by dot blot analysis of genomic DNA extracted from tumor-bearing liver, hybridized with a human-specific Alu probe. The combination of regional AdCMV.CD plus systemic 5-fluorocytosine (5-FC) suppressed the growth of the metastatic tumors over the 21 days of evaluation following vector administration. Histologic evaluation showed necrosis at the site of the tumor in the livers of mice treated with AdCMV.CD/5-FC, but not in control groups. Evaluation of the potential toxicity of AdCMV.CD plus 5-FC on the normal liver showed only mild, self-limited dose-related inflammation, with no deaths. These data suggest that the regional administration of AdCMV.CD together with systemic 5-FC may be a safe and effective strategy to suppress the growth of metastases of colorectal carcinoma in the liver.