Liver cancer protease activity profiles support therapeutic options with matrix metalloproteinase-activatable oncolytic measles virus

Primary and secondary cancers of the liver are a significant health problem with limited treatment options. We sought here to develop an oncolytic measles virus (MV) preferentially activated in liver tumor tissue, thus reducing infection and destruction of healthy tissue. We documented that in primary tumor tissue, urokinase-type plasminogen activator and especially matrix metalloproteinase-2 (MMP-2) are significantly more active than in adjacent nontumorous tissue. We then generated variants of the MV fusion protein by inserting different MMP substrate motifs at the protease cleavage site and identified the motif PQGLYA as the most efficient cleavage site as determined by syncytia formation on protease-positive tumor cells. The corresponding MMP-activatable oncolytic MV-MMPA1 virus was rescued and shown to be strongly restricted on primary human hepatocytes and healthy human liver tissue, while remaining as effective as the parental MV in the tumor tissue sections. Our findings underline the clinical potency of the MMP activation concept as a strategy to generate safer oncolytic viruses for the treatment of primary and secondary cancers of the liver.

Abstract 3551: Role of proteasome in the development of multidrug resistance in childhood rhabdomyosarcoma

Multidrug resistance (MDR) is a common problem in the treatment of childhood rhabdomyosarcoma (RMS). The aim of this study was to investigate different mechanism of MDR in childhood RMS and to analyze possible reversal strategies.

Female athymic mice underwent xenotransplantation with embryonal (A204) or alveolar (Rh30) RMS cells and were treated with vincristine (0.75 mg/kg/d i.p.). Gene expression analysis with Affymetrix oligonucleotide microarrays HU-Gene 1.0 revealed 2314 differentially expressed genes between the groups in alveolar RMS and 1387 in embryonal RMS. Ingenuity Pathways Analysis of biological pathways and functions of these genes revealed a cluster 21 genes related to the ubiquitin pathway. Among them 4 genes shown an up-regulation and 17 a 0.5 lower expression in vincristine treated samples. Furthermore, among of 45 genes of the proteasome cluster with 35 being down-regulated in RMS from animals treated with vincristine, putative mediating the development of MDR. Changes of gene expression were confirmed by qRT-PCR for selected proteasome components, such as PSMB1, PSMB6 and PSMD14. Specific inhibition of proteasome activity with bortezomib and MG132 inhibits proliferation of RMS cells, but reduces the cytotoxic activity of vincristine in a cell vitality assay. Our results emphasize the role of proteasome in the development of MDR in rhabdomyosarcoma treated with vincristine.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3551.

Adenovirus-mediated cytosine deaminase/5-fluorocytosine suicide gene therapy of human hepatoblastoma in vitro

BACKGROUND

Multidrug resistance is a key factor for the sobering outcome of relapsed and metastatic human hepatoblastoma (HB). Gene directed treatment approaches were recently identified as possible treatment options against advanced HB, in which standard chemotherapy regimens are partially insufficient. The aim of this study was to systematically analyze the effects of suicide gene therapy in three HB cell lines using a yeast-derived cytosine deaminase (YCD)-combined yeast uracil phosphoribosyltransferase (YUPRT)-based adenovirus-mediated gene transfer.

PROCEDURE

YCD and YUPRT were fused to form the bifunctional suicide gene SuperCD. Adeonoviral vectors were used for transduction. Tumor cells transduced at MOI 50 were incubated with 5-fluorocytosine (5-FC) in ascending concentrations.

RESULTS

Transduction rates were 87.8% (+6.7) in the mixed HB cell line HUH6, 98.6% (+1.4) in the epithelial HB cell line HepT1 and 93.6% (+0.6) in the multifocal HB embryonal cell line HepT3, respectively. In HepT3 and HepT1 cells suicide gene therapy with SuperCD/5-FC was highly effective leading to HB cell damage far above those of application of the prodrug 5-FC only. In HUH6 cells the approach had no effect due to a lack in activity of the CMV promoter being employed for transcription of the SuperCD transgene.

CONCLUSION

Assuming employment of fully active promoters, the SuperCD/5-FC approach may serve as a potentially useful anti-tumor strategy against advanced HB.

Human precision-cut liver tumor slices as a tumor patient-individual predictive test system for oncolytic measles vaccine viruses

Availability of an individualized preselection of oncolytic viruses to be used for virotherapy of tumor patients would be of great help. Using primary liver tumor resection specimens we evaluated the precision-cut liver slice (PCLS) technology as a novel in vitro test system for characterization of paramount tumor infection parameters of individual patients. PCLS slices from resection specimens of 20 liver tumor patients were cultivated in vitro for up to 5 days and infected with 5 different oncolytic measles vaccine virus (MeV) strains. Effectiveness of tumor infection was monitored by viral nucleocapsid (N) protein detection in immunofluorescence staining or Western blot analysis or by detection of GFP marker gene expression. MeV spreading in PCLS cultures was visualized by confocal microscopy. Oncolytic MeV vaccine particles were demonstrated to efficiently infect PCLS slices originating from different primary and secondary tumors of the liver with MeV strains Moraten/Edmonston Zagreb and AIK-C showing highest infection rates (75% of all tested tumor specimens). Employing mixed liver tissue slices (exhibiting both tumorous and non-tumorous tissue areas on one and the same sample) a distinct tumor area favouring pattern of MeV infections was observed being in accordance with our finding that primary human hepatocytes are also permissive to MeV particles, albeit at a much lower rate and with a much less pronounced cytopathic effect. Furthermore, confocal microscopy demonstrated virus penetration throughout tumor tissues into deep cell layers. In conclusion, the PCLS technology is suitable to perform a tumor-patient individualized preselection of oncolytic agents prior to clinical virotherapeutic applications.

In vitro photodynamic therapy in pediatric epithelial liver tumors promoted by hypericin

Limited treatment results in advanced pediatric liver tumors have emphasised the need for alternative treatment approaches in these malignancies. Photodynamic therapy (PDT) has been proposed as promising treatment approach in various malignancies. Hypericin, a naturally occurring substance found in the St. John's Wort, has regularly and successfully been used for visualisation and as photosensitizer in various tumor models. However, there exist no data on the effects of hypericin as photodynamic agent in pediatric malignant epithelial liver tumors. In this study, we investigated the potential role of hypericin for visualization and treatment in hepatoblastoma (HB) and pediatric hepatocellular carcinoma (HCC) cells. Two HB cell lines (HUH6, HepT1) and one HCC cell line (HepG2) were incubated with ascending concentrations of hypericin. Uptake and fluorescending capability were assessed using fluorescence microscopy and FACS. PDT with white light was performed for varying time intervals. Cell viability, cell proliferation and apoptotic rates were assessed using MTT assay, Ki-67 immunocytochemisty and TUNEL test, respectively. The changes within tumor cells under therapy were monitored using standard cytology. Relevant hypericin uptake was observed in all cell lines according to the applied concentrations. Histological analysis revealed no alterations of cell structure in HB and HCC cells after solely hypericin uptake, but severe alterations were found after PDT. Enhancement of the hypericin concentration (up to 12.5 microM) and illumination time of up to 40 min resulted in a decrease of tumor cell viability (HUH6 99.8+/-2.4%, HepT1 99+/-2%, HepG2 98.4+/-1.6%, p<0.05), proliferative activity and complete apoptosis of all cells in all investigated cell lines. These data show that hypericin might be a useful tool for visualisation and as alternative treatment option in HB and HCC.

Direct and natural killer cell-mediated antitumor effects of low-dose bortezomib in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) displays particular resistance to conventional cytostatic agents. Alternative treatment strategies focus on novel substances exhibiting antineoplastic and/or immunomodulatory activity enhancing for example natural killer (NK) cell antitumor reactivity. However, tumor-associated ligands engaging activating NK cell receptors are largely unknown. Exceptions are NKG2D ligands (NKG2DL) of the MHC class I-related chain and UL16-binding protein families, which potently stimulate NK cell responses. We studied the consequences of proteasome inhibition with regard to direct and NK cell-mediated effects against HCC.

EXPERIMENTAL DESIGN

Primary human hepatocytes (PHH) from different donors, hepatoma cell lines, and NK cells were exposed to Bortezomib. Growth and viability of the different cells, and immunomodulatory effects including alterations of NKG2DL expression on hepatoma cells, specific induction of NK cell cytotoxicity and IFN-gamma production were investigated.

RESULTS

Bortezomib treatment inhibited hepatoma cell growth with IC(50) values between 2.4 and 7.7 nmol/L. These low doses increased MICA/B mRNA levels, resulting in an increase of total and cell surface protein expression in hepatoma cells, thus stimulating cytotoxicity and IFN-gamma production of cocultured NK cells. Importantly, although NK cell IFN-gamma production was concentration-dependently reduced, low-dose Bortezomib neither induced NKG2DL expression or cell death in PHH nor altered NK cell cytotoxicity.

CONCLUSIONS

Low-dose Bortezomib mediates a specific dual antitumor effect in HCC by inhibiting tumor cell proliferation and priming hepatoma cells for NK cell antitumor reactivity. Our data suggest that patients with HCC may benefit from Bortezomib treatment combined with immunotherapeutic approaches such as adoptive NK cell transfer taking advantage of enhanced NKG2D-mediated antitumor immunity.

Establishing a novel single-copy primer-internal intron-spanning PCR (spiPCR) procedure for the direct detection of gene doping

So far, the abuse of gene transfer technology in sport, so-called gene doping, is undetectable. However, recent studies in somatic gene therapy indicate that long-term presence of transgenic DNA (tDNA) following various gene transfer protocols can be found in DNA isolated from whole blood using conventional PCR protocols. Application of these protocols for the direct detection of gene doping would require almost complete knowledge about the sequence of the genetic information that has been transferred. Here, we develop and describe the novel single-copy primer-internal intron-spanning PCR (spiPCR) procedure that overcomes this difficulty. Apart from the interesting perspectives that this spiPCR procedure offers in the fight against gene doping, this technology could also be of interest in biodistribution and biosafety studies for gene therapeutic applications.

In vitro photodynamic therapy of childhood rhabdomyosarcoma

Treatment of childhood rhabdomyosarcoma is limited by recurrent disease and the development of multidrug resistance. Therefore, novel treatment options are desirable. Photodynamic therapy (PDT) using the photodynamic agent hypericin is proposed as an alternative approach for intraoperative visualization and treatment of this disease. The aim of this study was to investigate in vitro effects of hypericin on childhood rhabdomyosarcoma and to evaluate photodynamic therapy as a possible basis for treatment. Rhabdomyosarcoma cells and fibroblasts (control) were incubated with increasing concentrations of hypericin. in vitro uptake and visualization of hypericin was evaluated by fluorescence microscopy and FACS. For photodynamic therapy, cells were exposed to white light for different time periods. Cytopathologic effects were assessed using standard histology. Cancer cells were investigated for cell viability (MTT assay), proliferative activity (Ki-67 assay), and apoptosis (TUNEL test). A 100% uptake of hypericin was found within the population of rhabdomyosarcoma cells. Uptake of hypericin in the fibroblasts was much less than in rhabdomyosarcoma cells. Hypericin without exposure to white light had no effect on tumor cell viability. After irradiation, PDT resulted in a nearly complete inhibition of cell proliferation of rhabdomyosarcoma cells with a corresponding increase in the frequency of apoptosis. In fibroblasts, PDT was less effective compared to tumor cells. Our data suggest hypericin as a novel tool for visualization and photodynamic therapy of childhood rhabdomyosarcoma.

Epigenetic combination therapy as a tumor-selective treatment approach for hepatocellular carcinoma

BACKGROUND

Innovative epigenetic therapeutics comprise histone deacetylase inhibitors (HDAC-I) and demethylating agents (DA). It was recently found that HDAC-I compounds exhibit profound therapeutic activities against hepatocellular carcinoma (HCC). A comprehensive preclinical investigation was performed on the potential of a combined HDAC-I/DA epigenetic regimen for the highly chemotherapy-resistant HCC entity.

METHODS

Human HCC-derived cell lines or primary human hepatocytes (PHH) were treated with HDAC-I compound suberoylanilide hydroxamic acid (SAHA) or DA compound 5-aza-2'-deoxycytidine (5-aza-dC) or both and examined for cellular damage, proliferation, histone acetylation pattern, and DNA methylation. In vivo activities were investigated in a xenograft hepatoma model.

RESULTS

Monotherapeutic application of SAHA or 5-aza-dC was found to induce substantial antiproliferative effects in HCC-derived cells, strongly enhanced by combined SAHA and 5-aza-dC treatment. PHH from different human donors did not exhibit any relevant cellular damage even when applying high doses of the combination regimen, whereas HCC-derived cell lines showed a dose-dependent damage. In vivo testing demonstrated a statistical significant inhibition of hepatoma cell growth for the combined treatment regime.

CONCLUSIONS

Because the combined HDAC-I/DA epigenetic approach was found to produce significant antitumor effects in HCC model systems and did not impair cellular integrity of untransformed hepatocytes, this combination therapy is now considered for further investigation in clinical trials.

Optimizing vector application for gene transfer into human hepatoblastoma cells

Gene targeting is currently of distinct interest as an innovative additive treatment option in various malignancies. Its role in pediatric liver tumors has not yet been evaluated thoroughly. For the first time the authors systematically analyzed both lipid-based transfection as well as transduction with adenovirus vectors (Ad) and Sendai virus vectors (SeVV) in order to optimize gene transfer into hepatoblastoma (HB) cells. Two HB cell lines were infected with Ad or SeVV coding for green fluorescent protein (Ad-GFP, SeVV-GFP); transduction efficiencies and apoptosis were assessed using flow cytometry. Furthermore, lipofection of HB cell lines with plasmid-constructs comprising liver-specific promoters was performed using Lipofectamine 2000 and FuGENE 6; lipofection efficiency was monitored by flow cytometry, microscopy, and luciferase activity. The Ad-GFP showed higher transduction rates (61-86%) than the SeVV-GFP (4-24%) depending on the HB cell line used. Infections with first generation SeVV vectors (SeVV-GFP) led to increased target cell apoptosis (7-43%) compared to Ad-GFP (4-16%). The Lipofectamine 2000 revealed a higher transfection efficiency than the FuGENE 6 for both HB cell lines tested. The liver-specific promoters were found to be differently active in the HB cell lines. This study delineates recombinant adenovirus vectors as a promising tool for gene transduction in the HB cells. Furthermore, enhanced activity of the liver-specific promoters in HUH6 cells compared to HepT1 cells supports the observation of varying biological behavior in histologically differing HB tissues.

Combinatorial epigenetic treatment approach for hepatocellular carcinoma

10066

Hepatocellular carcinoma (HCC) displays a striking resistance to chemotherapeutic drugs. Alternative approaches comprise employment of epigenetic compounds such as histone deacetylase inhibitors (HDAC-I) or demethylating agents (DA). Since we could recently demonstrate that HDAC-I exhibit inherent in vitro therapeutic activities against HCC cells, we now explored the potential of a HDAC-I / DA combined epigenetic treatment approach for the highly chemotherapy resistant tumor entity HCC. Methods: HCC cell lines (HepG2, Hep3B, HuH7) and primary human hepatocytes (PHH) were treated with a HDAC-I compound (Suberoylanilide hydroxamic acid - SAHA) together with or without a DA (5-aza-2dC) and examined for cellular damage (enzyme release), proliferation inhibition (SRB), apoptotic cells (FACS), histone acetylation pattern (Western blot) and methylation status (methylation specific PCR). The in vivo activity of our approach was investigated in a HuH7 xenograft mouse hepatoma model. Results: Both SAHA and 5-aza-2dC were found to induce substantial antiproliferative effects and apoptotic cell death in HCC cells; interestingly, combinatorial treatment (SAHA plus 5-aza-2dC) resulted in strongly enhanced anti-HCC effects. Interferences between DA and HDAC-I activities could be excluded by determining both (i) the methylation status of two model genes (p16, SOCS-1; known to be abberantly methylated in HCC) as well as (ii) patterns of histone acetylation. Most importantly, non-malignant primary human hepatocytes (5 different donors) did not exhibit any relevant cellular damage even when high doses of SAHA plus 5-aza-2dC were applied. Finally, in vivo testing of our combinatorial regimen (SAHA plus 5-aza-2dC) was found to be superior in suppression of tumor cell growth when compared to the application of single substances (SAHA or 5-aza-2dC) or placebo. Conclusion: Our combined epigenetic approach in chemotherapy resistant HCC not only has been found to be a highly active treatment option with profound anti-tumor effects both in vitro and in a small animal model in vivo, but did not impair primary human hepatocytes. Thus, this combination therapy now is considered for further investigation in clinical trials.

No significant financial relationships to disclose.

Bifunctional chimeric SuperCD suicide gene -YCD: YUPRT fusion is highly effective in a rat hepatoma model

AIM

To investigate the effects of catalytically superior gene-directed enzyme prodrug therapy systems on a rat hepatoma model.

METHODS

To increase hepatoma cell chemosensitivity for the prodrug 5-fluorocytosine (5-FC), we generated a chimeric bifunctional SuperCD suicide gene, a fusion of the yeast cytosine deaminase (YCD) and the yeast uracil phosphoribosyltransferase (YUPRT) gene.

RESULTS

In vitro stably transduced Morris rat hepatoma cells (MH) expressing the bifunctional SuperCD suicide gene (MH SuperCD) showed a clearly marked enhancement in cell killing when incubated with 5-FC as compared with MH cells stably expressing YCD solely (MH YCD) or the cytosine deaminase gene of bacterial origin (MH BCD), respectively. In vivo, MH SuperCD tumors implanted both subcutaneously as well as orthotopically into the livers of syngeneic ACI rats demonstrated significant tumor regressions (P<0.01) under both high dose as well as low dose systemic 5-FC application, whereas MH tumors without transgene expression (MH naive) showed rapid progression. For the first time, an order of in vivo suicide gene effectiveness (SuperCD>> YCD>>BCD>>>negative control) was defined as a result of a direct in vivo comparison of all three suicide genes.

CONCLUSION

Bifunctional SuperCD suicide gene expression is highly effective in a rat hepatoma model, thereby significantly improving both the therapeutic index and the efficacy of hepatocellular carcinoma killing by fluorocytosine.

HDAC inhibitor treatment of hepatoma cells induces both TRAIL-independent apoptosis and restoration of sensitivity to TRAIL

Hepatocellular carcinoma (HCC) displays a striking resistance to chemotherapeutic drugs or innovative tumor cell apoptosis-inducing agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Recently, we found 2 histone deacetylase inhibitors (HDAC-I), valproic acid and ITF2357, exhibiting inherent therapeutic activity against HCC. In TRAIL-sensitive cancer cells, the mechanism of HDAC-I-induced cell death has been identified to be TRAIL-dependent by inducing apoptosis in an autocrine fashion. In contrast, in HCC-derived cells, a prototype of TRAIL-resistant tumor cells, we found a HDAC-I-mediated apoptosis that works independently of TRAIL and upregulation of death receptors or their cognate ligands. Interestingly, TRAIL resistance could be overcome by a combinatorial application of HDAC-I and TRAIL, increasing the fraction of apoptotic cells two- to threefold compared with HDAC-I treatment alone, whereas any premature HDAC-I withdrawal rapidly restored TRAIL resistance. Furthermore, a tumor cell-specific downregulation of the FLICE inhibitory protein (FLIP) was observed, constituting a new mechanism of TRAIL sensitivity restoration by HDAC-I. In contrast, FLIP levels in primary human hepatocytes (PHH) from different donors were upregulated by HDAC-I. Importantly, combination HDAC-I/TRAIL treatment did not induce any cytotoxicity in nonmalignant PHH. In conclusion, HDAC-I compounds, exhibiting a favorable in vivo profile and inherent activity against HCC cells, are able to selectively overcome the resistance of HCC cells toward TRAIL. Specific upregulation of intracellular FLIP protein levels in nonmalignant hepatocytes could enhance the therapeutic window for clinical applications of TRAIL, opening up a highly specific new treatment option for advanced HCC.

In vitro gene targeting in human hepatoblastoma

Poor treatment results in advanced hepatoblastoma (HB) made alternative treatment approaches desirable. Gene-directed tumor therapy is increasingly investigated in different malignancies. The aim of this study was to analyze possible alternatives of gene transfer into HB cells and to study therapeutic applications based on different strategies. Liposomal transfection of HB cells was assessed using liver-specific promoters, and adenovirus and Sendai virus transductions were performed in vitro. Transfer efficiencies were measured via flow cytometry determining expression of vector-encoded marker gene green fluorescent protein. Gene silencing of the anti-apoptotic bcl-2 gene in HUH6 cells was performed using lipofection of small interfering RNA (siRNA). Additionally, suicide gene therapy was carried out through a yeast-derived cytosine deaminase (YCD)-combined yeast uracil phosphoribosyltransferase (YUPRT)-based adenovirus-mediated gene transfer, leading to a potent intracellular prodrug transformation of 5-fluorocytosine into 5-fluorouracil. Treatment efficiencies were monitored via MTT viability assay. Highest gene transfer rates (86%) were observed using adenovirus transduction. We furthermore observed a significant therapeutic effect of adenovirus-mediated YCD::YUPRT suicide gene transfer. Liposomal-mediated anti-bcl-2 siRNA transfer led to a significant improvement of cisplatin treatment in HUH6 cells. Liver-specific promoters were found to be strongly active in HUH6 cells (mixed HB-derived), but less active in HepT1 cells (embryonal HB-derived). Liposomal transfection and viral transduction are effective approaches to genetically manipulate HB cells in vitro. For the first time, we demonstrate a positive effect of siRNA gene silencing in this malignancy. Additionally, we successfully investigated a model of adenovirus-based suicide gene therapy in HB cell cultures. Our data strongly encourage further studies assessing these alternative treatment approaches.

Severe Impairment of Dendritic Cell Allostimulatory Activity by Sendai Virus Vectors Is Overcome by Matrix Protein Gene Deletion

Delivery of Ags to dendritic cells (DCs) plays a pivotal role in the induction of efficient immune responses ranging from immunity to tolerance. The observation that certain viral pathogens are able to infect DCs has led to a concept in which applications of recombinant viruses are used for Ag delivery with the potential benefit of inducing potent Ag-specific T cell responses directed against multiple epitopes. As a prerequisite for such an application, the infection of DCs by recombinant viruses should not interfere with their stimulatory capacity. In this context, we could show that an emerging negative-strand RNA viral vector system based on the Sendai virus (SeV) is able to efficiently infect monocyte-derived human DCs (moDCs). However, after infection with SeV wild type, both the response of DCs to bacterial LPS as a powerful mediator of DC maturation and the allostimulatory activity were severely impaired. Interestingly, using various recombinant SeV vectors that were devoid of single viral genes, we were able to identify the SeV matrix (M) protein as a key component in moDC functional impairment after viral infection. Consequently, use of M-deficient SeV vectors preserved the allostimulatory activity in infected moDCs despite an efficient expression of all other virally encoded genes, thereby identifying M-deficient vectors as a highly potent tool for the genetic manipulation of DCs.

Liver-directed gene expression employing synthetic transcriptional control units

AIM: To generate and characterize the synthetic transcriptional control units for transcriptional targeting of the liver, thereby compensating for the lack of specificity of currently available gene therapeutic vector systems.

METHODS: Synthetic transcriptional control unit constructs were generated and analyzed for transcriptional activities in different cell types by FACS quantification, semi-quantitative RT-PCR, and Western blotting.

RESULTS: A new bifunctionally-enhanced green fluorescent protein (EGFP)/neo^r fusion gene cassette was generated, and could flexibly be used both for transcript quantification and for selection of stable cell clones. Then, numerous synthetic transcriptional control units consisting of a minimal promoter linked to “naturally” derived composite enhancer elements from liver-specific expressed genes or binding sites of liver-specific transcription factors were inserted upstream of this reporter cassette. Following liposome-mediated transfection, EGFP reporter protein quantification by FACS analysis identified constructs encoding multimerized composite elements of the apolipoprotein B100 (ApoB) promoter or the ornithin transcarbamoylase (OTC) enhancer to exhibit maximum transcriptional activities in liver originating cell lines, but only background levels in non-liver originating cell lines. In contrast, constructs encoding only singular binding sites of liver-specific transcription factors, namely hepatocyte nuclear factor (HNF)1, HNF3, HNF4, HNF5, or CAAT/enhancer binding protein (C/EBP) only achieved background levels of EGFP expression. Finally, both semi-quantitative RT-PCR and Western blotting analysis of Hep3B cells demonstrated maximum transcriptional activities for a multimeric 4xApoB cassette construct, which fully complied with the data obtained by initial FACS analysis.

CONCLUSION: Synthetic transcriptional control unit constructs not only exhibit a superb degree of structural compactness, but also provide new means for liver-directed expression of therapeutic genes.

Natural killer cell-mediated lysis of hepatoma cells via specific induction of NKG2D ligands by the histone deacetylase inhibitor sodium valproate

Natural killer (NK) cells as components of the innate immunity substantially contribute to antitumor immune responses. However, the tumor-associated ligands engaging activating NK cell receptors are largely unknown. An exception are the MHC class I chain-related molecules MICA and MICB and the UL16-binding proteins (ULBP) which bind to the activating immunoreceptor NKG2D expressed on cytotoxic lymphocytes. A therapeutic induction of NKG2D ligands that primes cancer cells for NK cell lysis has not yet been achieved. By microarray studies, we found evidence that treatment of human hepatocellular carcinoma cells with the histone deacetylase inhibitor (HDAC-I) sodium valproate (VPA) mediates recognition of cancer cells by cytotoxic lymphocytes via NKG2D. VPA induced transcription of MICA and MICB in hepatocellular carcinoma cells, leading to increased cell surface, soluble and total MIC protein expression. No significant changes in the expression of the NKG2D ligands ULBP1-3 were observed. The induction of MIC molecules increased lysis of hepatocellular carcinoma cells by NK cells which was abolished by addition of a blocking NKG2D antibody. Importantly, in primary human hepatocytes, VPA treatment did not induce MIC protein expression. Taken together, our data show that the HDAC-I VPA mediates specific priming of malignant cells for innate immune effector mechanisms. These results suggest the clinical evaluation of HDAC-I in solid tumors such as hepatocellular carcinoma, especially in combination with immunotherapy approaches employing adoptive NK cell transfer.

Apoptosis on hepatoma cells but not on primary hepatocytes by histone deacetylase inhibitors valproate and ITF2357

BACKGROUND/AIMS

Due to a particular resistance against conventional chemotherapeutics, palliative treatment of hepatocellular carcinomas (HCC) is highly ineffective. Recent demonstration of both proliferation-inhibition and apoptosis of hepatoma cells by a histone deacetylase inhibitor (HDAC-I) treatment opens up a promising new approach. However, little is known about tumor cell death mechanisms and HDAC-I influences on healthy hepatocytes.

METHODS

HDAC-I substances with favourable in vivo profiles, valproate (VPA) and ITF2357, were investigated on HCC cell lines and primary human hepatocytes (PHH). Histone acetylation and apoptosis-modulating proteins were investigated by western-blotting, proliferation by sulforhodamin B binding, toxicity by enzyme release, apoptosis by FACS analysis.

RESULTS

VPA and ITF2357 inhibited proliferation in HCC cell lines. Both substances induced considerable cellular damage in HCC-derived cells, but PHH tolerated these substances well. A downregulation of anti- and upregulation of proapoptotic factors was found. Moreover, Bcl-X(L) transfection into HCC cells abrogated apoptosis induced by both substances, indicating that modulation of intracellular pro- and anti-apoptotic proteins is a key event in VPA or ITF2357 induced tumor-cell death.

CONCLUSIONS

Preferential induction of cell death in HCC-derived cell lines, without toxicity in PHH, demonstrates the potential of VPA and ITF2357 to become promising new tools in the fight against HCC.

Efficient propagation of single gene deleted recombinant Sendai virus vectors

Recombinant Sendai virus vectors (SeVV) have become an attractive tool for basic virological as well as for gene transfer studies. However, to (i) reduce the cellular injury induced by basic recombinant SeV vectors (encoding all six SeV genes as being present in SeV wild-type (wt) genomes) and to (ii) improve SeV vector safety, deletions of viral genes are necessary for the construction of superior SeVV generations. As a strong expression system recombinant replication-incompetent adenoviruses, coding for SeV proteins hemagglutinin-neuraminidase (HN), fusion (F), or matrix (M), were generated and successfully employed for the propagation of single gene deleted (DeltaHN, DeltaF, DeltaM) recombinant SeVV. Further investigations of the propagation procedures required for single gene deleted recombinant SeVV demonstrated (i) modifications of the cell culture medium composition as well as (ii) incubation with vitamin E as crucial steps for the enhancement of SeVV-DeltaHN, -DeltaF, or -DeltaM viral particle yield. Such optimized propagation procedures even led to a successful propagation of HN-deleted viral particles (SeVV-DeltaHN), which has not been reported before.

Changes in vascular endothelial growth factor (VEGF) after chemoendocrine therapy in breast cancer

PURPOSE

Angiogenesis has been proposed as a possible target for anticancer treatment, either by inhibition of the production of angiogenic factors or by inhibition of endothelial cell proliferation. The impact of preoperative chemoendocrine therapy is unknown in the regulation of angiogenic factors, but recent reports suggest that anticancer drugs have antiangiogenic activity.

METHODS

The expression of two angiogenic factors VEGF and Angiopoetin-1 were quantified at different concentrations of doxorubicin, docetaxel, tamoxifen, exemestane and letrozol on MCF-7 and T47D cells.

RESULTS

Low-drug concentrations led to increased VEGF-A gene transcription whereas high (10-fold increased) drug concentrations suppressed gene expression. A similar cell reaction was observed for VEGF protein with a smaller variety in the extent of modulation. Incubation of MCF-7 cells to different drugs showed a similar dose-dependent modulation of Angiopoietin-1 gene expression with enhancement at low-drug concentrations.

CONCLUSION

Treatment of breast cancer cells following a preoperative protocol showed a dose-dependent expression of VEGF and Angiopoetin-1. Only high-drug concentrations were followed by a decreased secretion of both factors whereas low concentrations induced up-regulation of VEGF and Angiopoietin 1.

Sendai virus vectors as an emerging negative-strand RNA viral vector system

The power to manipulate the genome of negative-strand RNA viruses, including the insertion of additional non-viral genes, has led to the development of a new class of viral vectors for gene transfer approaches. The murine parainfluenza virus type I, or Sendai virus (SeV), has emerged as a prototype virus of this vector group, being employed in numerous in vitro as well as animal studies over the last few years. Extraordinary features of SeV are the remarkably brief contact time that is necessary for cellular uptake, a strong but adjustable expression of foreign genes, efficient infection in the respiratory tract despite a mucus layer, transduction of target cells being independent of the cell cycle, and an exclusively cytoplasmic replication cycle without any risk of chromosomal integration. In this review we describe the current knowledge of Sendai virus vector (SeVV) development as well as the results of first-generation vector applications under both in vitro and in vivo conditions. So far, Sendai virus vectors have been identified to be a highly efficient transduction tool for a broad range of different tissues and applications. Future directions in vector design and development are discussed.

Adenoviral gene transfer of tumor necrosis factor-related apoptosis-inducing ligand overcomes an impaired response of hepatoma cells but causes severe apoptosis in primary human hepatocytes

Ligands of the tumor necrosis factor family play key roles in liver pathogenesis. The ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is unique, because it is thought to be nontoxic to normal cells while killing a broad range of tumor cells. However, hepatocellular carcinoma is considered resistant to soluble TRAIL treatment. Therefore, a direct gene transfer of TRAIL to malignant cells is part of an alternative delivery strategy. We show that an adenoviral gene transfer (Ad-TRAIL) overcomes an impaired response of hepatocellular carcinoma cell lines to soluble TRAIL, but the transduction of primary human hepatocytes revealed a high number of apoptotic cells. Our data imply that Ad-TRAIL administration in vivo must either be restricted to tumor tissue or controlled by a tumor-specific promoter to avoid severe liver damage in human trials.

Cell cycle independent infection and gene transfer by recombinant Sendai viruses

A common problem for viral vectors in the field of somatic gene therapy is the dependence of an efficient cellular transduction on the cell cycle phase of target cells. An optimized viral vector system should therefore transduce cells in different cell cycle phases equally to improve transduction efficiencies. Recent observations that recombinant Sendai viruses (SeV) can infect a broad range of different tissues suggested SeV to be a good candidate for future gene therapeutic strategies in which dividing and non-dividing cells have to be reached. However, detailed data on the influence of distinct cell cycle phases on the infection of SeV or related viruses are missing. We report that synchronization of NIH 3T3 cells as well as contact inhibition of human fibroblast cells did not exhibit any negative influence on SeV infection rates. Furthermore, different attractive target tissues like human umbilical cord derived cells or primary human hepatocytes can be reached by SeV efficiently. As an important information for further cell cycle studies of paramyxoviruses we discovered surprisingly that the DNA polymerase inhibitor aphidicolin (induces a G(1)/M arrest) functions as an inhibitor of SeV but not of an adenoviral expression vector. In conclusion, the results demonstrate SeV based vector particles to be an ideal tool to reach equally cells coexisting in different cell cycle phases.

Negative-strand RNA viral vectors: intravenous application of Sendai virus vectors for the systemic delivery of therapeutic genes

Treatment by gene replacement is critical in the field of gene therapy. Suitable vectors for the delivery of therapeutic genes have to be generated and tested in preclinical settings. Recently, extraordinary features for a local gene delivery by Sendai virus vectors (SeVV) have been reported for different tissues. Here we show that direct intravenous application of SeVV in mice is not only feasible and safe, but it results in the secretion of therapeutic proteins to the circulation, for example, human clotting Factor IX (hFIX). In vitro characterization of first-generation SeVV demonstrated that secreted amounts of hFIX were at least comparable to published results for retroviral or adeno-associated viral vectors. Furthermore, as a consideration for application in humans, SeVV transduction led to efficient hFIX synthesis in primary human hepatocytes, and SeVV-encoded hFIX proteins could be shown to be functionally active in the human clotting cascade. In conclusion, our investigations demonstrate for the first time that intravenous administration of negative-strand RNA viral vectors may become a useful tool for the wide area of gene replacement requirements.

Vascular endothelial growth factor (VEGF165) and its influence on angiogenesis versus arteriogenesis in different vascular beds

PURPOSE

To use local gene delivery to determine any district-specific influence of vascular endothelial growth factor (VEGF(165)) on angiogenesis and arteriogenesis in arteries of distinct developmental origin.

METHODS

Coronary and peripheral arteries were chronically occluded in 30 Pietrain pigs using a percutaneous approach and blinded stent-graft. DNA was delivered to the adventitia in dosages corresponding to 10% of the body weight-adapted amount used in clinical trials. The coronary arteries in 12 animals and the peripheral arteries in 12 animals were treated or used as controls (no occlusion or occlusion with transfection of the beta-galactosidase gene). Six additional animals were sacrificed at 1 or 3 weeks for expression analyses, while the other 24 animals were sacrificed at 5 months for expression analysis and histology. Angiography, polymerase chain reaction analyses, and immunohistochemistry were performed.

RESULTS

Expression of the VEGF gene was observed at 1 and 3 weeks following application, while transfected DNA was detected up to 5 months. New collaterals formed around occluded coronary arteries (2.63 +/- 0.69 fold, p<0.05 versus 1.24 +/- 0.40 fold for peripheral arteries), and angiographic arterial area increase was more pronounced in coronary (2.49 +/- 0.59 fold, p<0.05) than peripheral arteries (1.49 +/- 0.05 fold). There was no collateralization surrounding occluded peripheral arteries, but new arterial branches were seen (2.0 +/- 0.28, p<0.05 versus 1.07 +/- 0.31 for coronary).

CONCLUSIONS

The response to VEGF, whether it is predominantly angiogenesis or arteriogenesis, is dependent on the target vessel. These observed differences in the behavior of arteries may be related to their differing developmental origins, which may have important implications for future therapeutic strategies using VEGF in different vessels.

Optimization of nonviral transfection: variables influencing liposome-mediated gene transfer in proliferating vs. quiescent cells in culture and in vivo using a porcine restenosis model

Cationic liposomes/DNA complexes are widely used vectors for delivering genes in clinical and experimental trials. Relatively low transfer efficiencies in vivo compared with viral gene transfer may be improved using local application. In addition, markedly increased transfer efficiency may be achieved in vitro and in vivo via optimization of known variables influencing liposomal transfection. Lipofection under different conditions was performed in various cell lines and primary porcine smooth muscle cells. Optimized conditions found in vitro were verified in vivo using a porcine restenosis model. Toxicity was monitored analyzing cell metabolism. Transfer efficiency and safety were determined using morphometry, histology, galactosidase assays, PCR, and RT-PCR. The most important variables enabling maximum transfer efficiency were firstly the appropriate selection of cationic lipids for the cell type to be transfected, secondly the DNA/liposome ratio chosen, which depended on the cell type and cationic lipids used, and thirdly the state of proliferation of the targeted cells. Transfection in vivo demonstrated two- to fivefold higher transfer efficiencies when transfer conditions were extrapolated from optimization experiments in stationary cells compared with the use of conditions established in proliferating cells. Application of the therapeutic gene for cecropin using optimized transfer conditions resulted in a significantly reduced neointima formation compared with the transfection using a control gene for ss-galactosidase. Thus, in this vascular model, initial optimization of lipofection in stationary cells in culture followed by local delivery in vivo and with selection of a suitable therapeutic gene led to markedly improved transfer efficiencies, gene expression, and biological effect. Stationary cell cultures simulate more realistically the in vivo situation and may therefore represent a better model for future in vivo experiments. In addition, the advantages of liposomes are easy handling, low toxicity, and the lack of carcinogenicity or immunogenic reactions.

Caspase-8 and Apaf-1-independent caspase-9 activation in Sendai virus-infected cells

Apoptotic cell death is of central importance in the pathogenesis of viral infections. Activation of a cascade of cysteine proteases, i.e. caspases, plays a key role in the effector phase of virus-induced apoptosis. However, little is known about pathways leading to the activation of initiator caspases in virus-infected host cells. Recently, we have shown that Sendai virus (SeV) infection triggers apoptotic cell death by activation of the effector caspase-3 and initiator caspase-8. We now investigated mechanisms leading to the activation of another initiator caspase, caspase-9. Unexpectedly we found that caspase-9 cleavage is not dependent on the presence of active caspases-3 or -8. Furthermore, the presence of caspase-9 in mouse embryonic fibroblast (MEF) cells was a prerequisite for Sendai virus-induced apoptotic cell death. Caspase-9 activation occurred without the release of cytochrome c from mitochondria and was not dependent on the presence of Apaf-1 or reactive oxygen intermediates. Our results therefore suggest an alternative mechanism for caspase-9 activation in virally infected cells beside the well characterized pathways via death receptors or mitochondrial cytochrome c release.

Quiescence, cell viability, apoptosis and necrosis of smooth muscle cells using different growth inhibitors

Smooth muscle cells and endothelial cells play an important role in cardiovascular diseases and may therefore be a potential target for gene therapy. Most in vitro experiments are performed using proliferating cell cultures. Nevertheless, non-dividing cells would represent more realistic in vivo conditions for gene therapy. Therefore, a simple method to achieve physiologically quiescence in cell cultures is needed for experiments. Growth to confluence is sufficient for endothelial cells to reach quiescence, in contrast to smooth muscle cells. Alternative techniques were investigated to achieve quiescence for smooth muscle cells. N-acetyl-cysteine, heparin, aphidicolin and serum-free medium are known inhibitors of smooth muscle cell proliferation and were tested for cell viability, necrosis and apoptosis. The inhibition status was evaluated counting cells in a cell counter. Toxicity, necrosis and apoptosis were determined using FACS analysis. Then, smooth muscle cells and endothelial cells were transfected with plasmid containing the beta-galactosidase gene using liposomes. Analysis of gene expression in transfected cells included a quantitative beta-galactosidase assay and X-gal staining. Growth inhibition was achieved with all agents tested. Using N-acetyl-cysteine, only slightly reduced growth rates were observed. Aphidicolin stopped cell growth almost immediately, but demonstrated enhanced toxicity. The amount of apoptotic and necrotic cells was lowest using heparin in the presence of foetal calf serum. Transfection experiments using stationary cultures of smooth muscle cells using heparin or aphidicolin demonstrated 5-10-fold lower transfection rates compared to transfected proliferating cell cultures serving as controls. Transfection experiments using stationary cultures of endothelial cells using growth inhibition through confluence demonstrated 40-fold lower transfection rates than transfected proliferating cell cultures. Transfer efficiency was much lower in endothelial cells compared to smooth muscle cells. In conclusion, quiescent cells simulate more realistically the in vivo situation and may therefore represent a better model for future in vivo experiments based on in vitro findings.

Evaluation of endovascular techniques for creating a porcine femoral artery occlusion model

PURPOSE

To determine the optimal endovascular approach to achieve long-term occlusion of large arteries, while preserving the integrity of periarterial tissue, in an animal model of ischemia.

METHODS

Femoral artery occlusions were created in 16 pigs using detachable balloons, coils, or blinded stent-grafts. Feasibility, safety, primary and long-term success, and the degree of neovascularization were determined over a 6-month period by serial angiography and histological analyses. Four animals served as untreated controls.

RESULTS

Overall primary success for all occlusion devices was 100%. The 6-month occlusion rate using detachable balloons or coils was 33% and 0%, respectively; however, all arteries occluded with blinded stent-grafts remained obstructed to the end of the study. There was no significant difference in capillary densities and collateralization of periarterial areas when occluded arteries were compared with nonoccluded controls in the same animal. No increase in collateralization was observed following endovascular arterial occlusion.

CONCLUSIONS

Percutaneous insertion of blinded stent-grafts easily, safely, and reliably creates long-term arterial occlusion in pigs, which may make this a more appropriate model for studying the effects of angiogenic factors in vivo.

In vivo perivascular implantation of encapsulated packaging cells for prolonged retroviral gene transfer

Long-term benefits of coronary angioplasty remain limited by the treatment-induced renarrowing of arteries, termed restenosis. One of the mechanisms leading to restenosis is the proliferation of smooth muscle cells. Therefore, proliferating cells of the injured arterial wall, which can be selectively transduced by retroviruses, are potential targets for gene therapy strategies. A direct single-dose therapeutic application of retroviral vectors for inhibition of cell proliferation is normally limited by too low transduction efficiencies. Encapsulated retrovirus-producing cells release viral vectors from microcapsules, and may enhance the transduction efficiency by prolonged infection. Primary and immortal murine and porcine cells and murine retrovirus-producing cells were encapsulated in cellulose sulphate. Cell viability was monitored by analysing cell metabolism. Safety, stability, transfer efficiency and extent of restenosis using capsules were determined in a porcine restenosis model for local gene therapy using morphometry, histology, in situ beta-galactosidase assay and PCR. Encapsulation of cells did not impair cell viability. Capsules containing retrovirus-producing cells expressing the beta-galactosidase reporter gene were implanted into periarterial tissue or a pig model of restenosis. Three weeks following implantation, beta-galactosidase activity was detected in the pericapsular tissue with a transduction efficiency of approximately 1 in 500 cells. Adventitial implantation of vector-producing encapsulated cells for gene therapy may, therefore, facilitate successful targeting of proliferating vascular smooth muscle cells, and allow stable integration of therapeutic genes into surrounding cells. The encapsulation of vector-producing cells could represent a novel and feasible way to optimize local retroviral gene therapy.

Involvement of E-cadherin in the Development of Erythroid Cells; Subject Heading

The cadherins represent a large family of structurally and functionally related cell adhesion molecules involved in morphogenesis of multicellular organisms and maintenance of solid tissues. In the hematopoietic system, however, almost nothing was known about the involvement of this family. PCR screening of RNA of human bone marrow mononuclear cells with specific primers for different classical cadherins revealed that members of this family are also expressed by bone marrow cells. Here we report that E-cadherin, which is mainly expressed by cells of epithelial origin, plays a critical role in the development of human erythrocytes. FACS analysis with human E-cadherin-specific antibodies and the use of immunoaffinity columns revealed that expression of E-cadherin is restricted to defined maturation stages of the erythropoietic cell lineage. Erythroblasts and normoblasts express E-cadherin, but mature erythrocytes do not. Lymphoid and all the other myeloid cell lineages do not express E-cadherin at any developmental stage. The differentiation of the erythroid lineage in vitro could be influenced by addition of anti-E-cadherin antibodies in a concentration dependent manner indicating a direct involvement of this cell adhesion molecule in the differentiation process. In line with these in vitro data is the finding that E-cadherin is down regulated during erythroleukemia on the developing erythroid cells. Our results suggest an unanticipated function of E-cadherin in the hematopoietic system.

N-cadherin is developmentally regulated and functionally involved in early hematopoietic cell differentiation

The cadherins, an important family of cell adhesion molecules, are known to play major roles during embryonic development and in the maintenance of solid tissue architecture. In the hematopoietic system, however, little is known of the role of this cell adhesion family. By RT-PCR, western blot analysis and immunofluorescence staining we show that N-cadherin, a classical type I cadherin mainly expressed on neuronal, endothelial and muscle cells, is expressed on the cell surface of resident bone marrow stromal cells. FACS analysis of bone marrow mononuclear cells revealed that N-cadherin is also expressed on a subpopulation of early hematopoietic progenitor cells. Triple-color FACS analysis defined a new CD34(+) CD19(+) N-cadherin(+) progenitor cell population. During further differentiation, however, N-cadherin expression is lost. Treatment of CD34(+) progenitor cells with function-perturbing N-cadherin antibodies drastically diminished colony formation, indicating a direct involvement of N-cadherin in the differentiation program of early hematopoietic progenitors. N-cadherin can also mediate adhesive interactions within the bone marrow as demonstrated by inhibition of homotypic interactions of bone-marrow-derived cells with N-cadherin antibodies. Together, these data strongly suggest that N-cadherin is involved in the development and retention of early hematopoietic progenitors within the bone marrow microenvironment.

Evaluation of beta-galactosidase activity in tissue in the presence of blood

The reporter gene for beta-galactosidase is frequently used to determine the efficiency of gene transfer in arteries. However, blood is often present in arterial explants and may compromise the results by the presence of hemoglobin. The light absorption of hemoglobin is similar to the absorption of several colorimetric products of the commonly used beta-galactosidase substrates, including o-nitrophenyl-beta-D-galactopyranoside (ONPG) and chlorophenol red galactopyranoside (CPRG). This may result in false-positive measurements of beta-galactosidase enzyme activity. The aim of this investigation was to determine the most appropriate method for quantification of beta-galactosidase activity in the presence of blood. Colorimetric substrates (ONPG, CPRG) or the chemiluminescent Galacton-Plus substrate were used, and light absorption was measured at different concentrations of erythrocyte extract. Among the beta-galactosidase substrates tested, CPRG was the most appropriate, allowing detection of enzyme activity at concentrations as low as 0.05 mU, independent of blood contamination. Addition of reducer stabilized enzyme activity for at least 5 h. Endogenous beta-galactosidase activity was evaluated and used to correct results. CPRG substrate, in combination with the reducer agent mercaptoethanol, was found to be the optimal reagent for quantifying beta-galactosidase activity in the presence of blood after nonviral in vivo reporter gene transfection, even with a relatively low transfer efficiency.

Optimization of nonviral gene transfer of vascular smooth muscle cells in vitro and in vivo

Gene therapy strategies for the prevention of restenosis postangioplasty are promising. Nonviral gene transfer to the arterial wall in vivo has so far been limited by poor efficiency. This study aimed to optimize transfection of primary vascular smooth muscle cells using cationic nonviral formulations based on cholesterol derivates (DC-, DAC-, DCQ-, and Sp-Chol), double-chained amphiphils (LipofectAMINE, DOTMA, DOSGA, DOSPER, and DOCSPER), or heterogeneous reagents (Superfect, Effectene, and Tfx-50). Estimation of transfection efficiencies was performed using galactosidase assays at different ratios of transfection reagent to plasmid DNA with reporter gene. Toxicity was monitored by analyzing cell metabolism. Transfer efficiency and safety were determined in a porcine restenosis model for local gene therapy using morphometry, histology, galactosidase assays, and reverse-transcriptase polymerase chain reaction. The highest in vitro transfection efficiency was achieved using the recently developed DOCSPER liposomes, with transfer rates of at least 20% in vascular smooth muscle cells. Transfer efficiency was further enhanced up to 20% by complexing with poly-L-lysine. Transfection efficiency in vivo in a porcine restenosis model was up to 15% of adventitial cells using DOCSPER versus 0.1% using LipofectAMINE. Toxicity in vivo and in vitro was lowest using DOCSPER. Increased biological effects were demonstrated following optimization of transfer conditions.

Prevention of Restenosis Using the Gene for Cecropin Complexed with DOCSPER Liposomes under Optimized Conditions

Up to 30% of patients undergoing coronary angioplasty develop a renarrowing of treated vessels following percutaneous transluminal coronary angioplasty with or without stent implantation, called restenosis. Smooth muscle cell proliferation, among other mechanisms, is an important factor in restenosis leading to neointima formation and consequent arterial lumen narrowing. Cecropins are antimicrobial peptides with antiproliferative properties in mammalian cells which have been shown to suppress neointimal formation. In this investigation, a plasmid carrying the gene for pre-pro-cecropin A, complexed with new generation liposomes optimized for transfer conditions for vascular cells was delivered to the adventitia of arteries in a porcine arterial injury model using a needle injection catheter. Retention of the plasmid in treated arteries was demonstrated for at least 21 days following delivery. Whereas previous experiments using first generation liposomes demonstrated significant but not complete neointima inhibition, the use of new liposomes under optimized conditions resulted in almost total suppression of neointimal proliferation. Thus, in vivo gene transfer of cecropins may be therapeutically applicable in restenosis prevention.

Needle injection catheter delivery of the gene for an antibacterial agent inhibits neointimal formation

Percutaneous transluminal coronary angioplasty is a routinely used non-surgical revascularization technique for patients with coronary artery disease. Up to 30% of patients undergoing coronary angioplasty develop a renarrowing of treated vessels, called restenosis. Smooth muscle cell proliferation is thought to be an important factor in restenosis; this leads to neointima formation and arterial lumen narrowing. Neointima may be reduced by the transfer of genes encoding proteins with antiproliferative effects. Cecropins are antimicrobial peptides with antiproliferative properties in mammalian cells. Cecropin A is one member of this family of peptides. In this article, a plasmid carrying the gene for the immature form, pre-pro-cecropin A, complexed with liposomes was locally delivered to perivascular tissue in a porcine arterial injury model using a needle injection catheter. Retention of the plasmid in the treated arteries was demonstrated at both 8 and 21 days following application. Transferred plasmid DNA was not detected in any other tissues analyzed. Pre-pro-cecropin A-specific transcripts could also be found in treated arteries. Balloon-injured vessels demonstrated significantly reduced neointima at 21 days in vessels treated with the pre-pro-cecropin A gene compared with neointimal area in those given a control gene (P < 0.05). The needle injection catheter appears to be useful for local intravascular gene delivery. In vivo gene transfer of cecropins may be of therapeutic relevance in restenosis prevention by limiting cell proliferation.

The adhesion molecule E-cadherin and a surface antigen recognized by the antibody 9C4 are selectively expressed on erythroid cells of defined maturational stages

The antigen expression of immature erythroid bone marrow cells was studied using two recently generated monoclonal antibodies (mAb), mAb 67A4 and 9C4, with specificities for the epithelial cell adhesion molecule E-cadherin (E-cad; mAb 67A4), and a novel 110 kDa differentiation antigen (mAb 9C4) with unknown molecular structure. Pappenheim staining of FACS-purified cells labeled with mAb 9C4 and anti-glycophorin A (GA) revealed that the majority of the 9C4+GA- and 9C4+GA+ cells consisted of erythroblasts. In contrast, the E-cad-positive population comprised normoblasts and erythroblasts. While the E-cad+GA- fraction contained mainly erythroblasts and basophilic normoblasts, the E-Cad+GA+ population was enriched in orthochromatic and polychromatophilic normoblasts. By colony assays of affinity column-purified cells it could be shown that erythroid colony forming units (CFU-E) were enriched and erythroid burst forming units (BFU-E) were depleted in the 9C4- and E-cad-positive fractions. Flow cytometric analysis of bone marrow cells double-labeled with mAb 67A4 and anti-CD71, anti-CD117, anti-CD34, or anti-GA revealed that about 90% of the E-cad-positive cells coexpressed CD71, about 70% were positive for CD117, about 50% for GA, and only about 5% coexpressed CD34. The expression pattern of 9C4 antigen was similar to that of E-Cad with the exception that only a minority of the 9C4-positive cells coexpressed GA. Lymphoid and myeloid markers were negative on both the E-Cad- and 9C4-positive populations. In these studies we describe the identification of a new mAb-defined antigen which is specifically expressed on erythroblasts and CFU-E(9C4) and demonstrate that E-Cad is not only expressed on epithelial cells but also on erythropoietic cells of defined maturational stages.

E-cadherin is functionally involved in the maturation of the erythroid lineage

Differentiation and proliferation of hematopoietic progenitors take place in the bone marrow and is a tightly controlled process. Cell adhesion molecules of the integrin and immunoglobulin families have been shown to be involved in these processes, but almost nothing was known about the involvement of the cadherin family in the hematopoietic system. A PCR screening of RNA of human bone marrow mononuclear cells with specific primers for classical cadherins revealed that E-cadherin, which is mainly expressed by cells of epithelial origin, is also expressed by bone marrow cells. Western blot analysis and immunofluorescence staining of bone marrow sections confirmed this unexpected finding. A more detailed analysis using immunoaffinity columns and dual color flow cytometry showed that the expression of E-cadherin is restricted to defined maturation stages of the erythropoietic lineage. Erythroblasts and normoblasts express E-cadherin, mature erythrocytes do not. A functional role of E-cadherin in the differentiation process of the erythroid lineage was indicated by antibody-inhibition studies. The addition of anti-E-cadherin antibody to bone marrow mononuclear cultures containing exogeneous erythropoietin drastically diminished the formation of erythropoietic cells. These data suggest a non-anticipated expression and function of E-cadherin in one defined hematopoietic cell lineage.