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T Licht

Publications and source records attributed to T Licht.

At least 19 recordsLinked to original sources
PubMed2006

[Soft tissue sarcoma of the extremities: current state of the art of adjuvant therapy].

Today, most sarcoma patients can be spared an amputation through the use of adjuvant radiotherapy. Treatment by an experienced multidisciplinary team offers the best chance of achieving permanent tumor control. Histopathologically-free resection margins are of the greatest importance. The indication for radiotherapy is determined by the recurrence risk profile of the individual patient. In addition to the well-proven postoperative irradiation, neoadjuvant radiotherapy is also successful. In the event of an unfavorably sited tumor, intra-operative irradiation can be applied in combination with either form. Patients with large G3 tumors can be given adjuvant chemotherapy to reduce the risk of distant metastases. On account of its appreciable toxicity, however, it should be reserved for patients younger than 65 in a good state of health.

Antibiotics, Antineoplastic↗
PubMed2003

Influence of differing radiotherapy strategies on treatment results in diffuse large-cell lymphoma: a review.

In the absence of evidence from randomised trials, radiation treatment of diffuse large-cell lymphoma of B-cell type represents an area of controversy with considerable differences in patterns of practice. The present literature survey aims at clarification of the role of radiotherapy in combined modality settings by identification of dose-response relationships, predictive factors for local control, and potential pitfalls in the interpretation of retrospective studies. Radiotherapy might increase local control in initially involved areas and is usually delivered to these sites (involved-field treatment). Combined modality treatment is currently recommended for patients in stage I or II if they are not treated in the context of prospective studies. Whether involved-field consolidation radiotherapy after systemic treatment in patients with bulky, stage III-IV lymphomas should be routinely recommended is presently unclear. Definition of bulky disease is arbitrary and varied between 6 and 10cm, reflecting a considerable difference in the number of clonogenic tumour cells. Several retrospective and one prospective randomised study suggest improved disease-free and overall survival by radiotherapy in advanced stages. The 5-year local control by radiotherapy was 93-98%. Currently, we recommend the following minimum doses for involved-field radiotherapy derived from this literature survey. Lymphomas with initial size <3.5 cm (possibly <6 cm) can be treated with 30 or 30.6Gy when a complete remission (CR) has been achieved by chemotherapy. The next group might be sufficiently controlled by 36Gy, but it remains unclear whether the cut-off should be 6cm or higher. Forty Gy appears to control tumours in the range of 7-10cm. Most likely, 45Gy does not have to be exceeded for larger lesions. Data on those with less than CR are contradictory. Judging the amount of viable tumour in these patients is problematic, but crucial to determine the intensity of further treatment. The value of positron emission tomography is still under investigation. Because the difference between doses of 30 and 40Gy might actually make a difference for the long-term toxicity of radiotherapy in some of the normal tissues and organs at risk (salivary glands, orbital structures, lung, heart, etc.), it appears prudent to resolve the open questions in prospective trials with careful documentation of side effects.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2002

Gene therapy for sarcoma.

Soft tissue sarcomas are mesenchymal tumors which respond poorly to systemic therapy. Recent studies suggest a higher response rate with an increased doxorubicin dosage. However, this was parallel with a profound hematotoxicity in 75% of patients. Transfer of the human multidrug resistance 1 (MDR1) gene to normal hematopoietic stem cells and transplantation may significantly reduce the hematotoxicity of anthracyclin-based chemotherapy. To test this concept of supportive gene therapy in advance of a clinical study, we transduced mobilized peripheral blood progenitor cells (PBPC) with the retroviral vector SF91m3 containing the human MDR1 gene, transplanted these cells to immune-deficient mice, allowed 6 weeks for engraftment to occur and treated the animals with MDR1-based chemotherapy. In the MDR1-transduced group the human leukocytes were significantly protected from the toxicity of chemotherapy (p < 0.05). While the gene transfer rate was in the range of 10% and thus comparable to recent clinical trials, the gene expression was 59% of transduced cells and thus significantly higher than previously reported for less-advanced vectors. On the other hand, ifosfamide, a drug which has been used successfully for stem cell mobilization, is active in soft tissue sarcoma. Due to these favorable characteristics sarcoma is an attractive target to test the efficacy of MDR1 gene therapy in a clinical setting. Gene therapeutic strategies may also be used to directly target sarcoma cells, e.g. by transfer of suicide genes. We found that adenoassociated virus 2 (AAV-2) vectors efficiently transduce human HS-1 and HT1080 sarcoma cells (>90%) while other tumor cell lines and primary human PBPC were less susceptible. The thymidine kinase (TK) suicide gene was cloned into an AAV-2 vector and a complete kill of TK-transduced HS-1 and HT1080 cells was observed following exposure to aciclovir or ganciclovir (GCV), while >90% of mock-transduced HS-1 cells survived at these dosages. Transplantation of those sarcoma cells to nonobese diabetic (NOD)/LtSz-severe-combined immunodeficient (scid)/scid (NOD/SCID) mice resulted in a survival of >5 months in the AAV-TK-transduced/GCV-treated group, while the mice in the mock-transduced/GCV-treated group had died after 3 weeks. These data show that soft tissue sarcomas are a particularly suitable model system for the development and clinical testing of new gene therapeutic concepts.

Animals↗
PubMed2001

Modulation of cell growth by the hepatitis C virus nonstructural protein NS5A.

Hepatitis C virus nonstructural protein, NS5A, is a phosphoprotein produced from the processing of the viral polyprotein precursor. NS5A associates with several cellular proteins in mammalian cells, and the biological consequences of this interaction are currently unknown. To this end, five stable NS5A-expressing murine and human cell lines were established. Tetracycline-regulated NIH3T3 cells and rat liver epithelial cells as well as the constitutive, NS5A-expressing, human Chang liver, HeLa, and NIH3T3 cells all exhibited cell growth retardation compared with the control cells. Cell cycle analysis by flow cytometry indicated that the NS5A-expressing human epitheloid tumor cells had a reduced S phase and an increase in the G(2)/M phase, which could be explained by a p53-dependent induction of p21(Waf1/Cip1) protein and mRNA levels. NS5A interacts with Cdk1 in vivo and in vitro, and a significant portion of the p21(Waf1/Cip1) was found to be in a complex with Cdk2 in the NS5A-expressing human hepatic cell line. Cdk1 and cyclin B1 proteins were also reduced in human Chang liver cells consistent with the increase in G(2)/M phase. Our results suggest that the NS5A protein causes growth inhibition and cell cycle perturbations by targeting the Cdk1/2-cyclin complexes.

3T3 Cells↗
PubMed2001

Efficient retrovirus-mediated transduction of primitive human peripheral blood progenitor cells in stroma-free suspension culture.

Retroviral transduction of hematopoietic cells has resulted in unsatisfactory gene marking in clinical studies. Since cytokine-stimulated stem cells have engrafted poorly in animal models, we investigated phenotypic changes during culture of peripheral blood progenitor cells (PBPC). Human CD34(+) HLA-DR(low) cells, immunomagnetically separated from PBPC collections, were found to extrude rhodamine-123, which is characteristic for primitive hematopoietic cells. Cells were grown in suspension cultures supplemented with cytokines. While interleukin-3-containing factor combinations promoted cell proliferation they caused loss of rhodamine-123 extrusion and reduced the frequencies of cobblestone area-forming cells (CAFC). Several other cytokines failed to stimulate cell divisions, which are required for retroviral transduction. A combination including Flt-3 ligand (FL), interleukin-6 and stem cell factor (SCF) preserved an immature phenotype for 5 to 6 days and stimulated cell divisions, which was improved upon addition of leukemia inhibitory factor and interleukin-11. Furthermore, the CAFC frequency among cells treated with these cytokines was increased as compared with widely used cocktails containing interleukin-3, interleukin-6 and SCF. Rhodamine-123 appeared to be a particularly sensitive indicator for differentiation of PBPC. For analysis of gene transfer, amphotropic retroviruses conferring an MDR1 cDNA were added repeatedly for 6 days to cytokine-treated PBPC stroma-free cultures. Proviral cDNA was detected by polymerase chain reaction in 68% of cobblestone areas derived from CD34(+)HLA-DR(low) cells that had been exposed to Flt-3 ligand, interleukin-6 and SCF. In summary, conditions were identified that facilitate efficient transduction of early PBPC with amphotropic retroviruses while preserving a primitive phenotype for extended periods.

Antigens, CD34↗
PubMed2000

Chemoprotection of hematopoietic cells by a mutant P-glycoprotein resistant to a potent chemosensitizer of multidrug-resistant cancers.

Cancers are frequently chemoresistant because of overexpression of P-glycoprotein. Two different approaches to improve cancer treatment are currently being investigated in clinical trials: inhibition of P-glycoprotein function by reversing agents, and alleviation of leukocytopenia by MDR1 gene transfer to normal bone marrow of patients. We report here that retroviral vectors encoding a mutant P-glycoprotein (MDR1-F983A) protect hematopoietic cells from anticancer drugs even in the presence of trans-(E)-flupentixol, an inhibitor of P-glycoprotein. Transfer of either mutant or wild-type MDR1 to K562 erythroleukemia cells or primary murine bone marrow resulted in reduced accumulation of daunomycin and vinblastine because of increased drug efflux.trans-(E)-Flupentixol at concentrations up to 10 microM failed to reverse drug efflux mediated by the product of the mutant MDR1 while wild-type P-glycoprotein was inhibited. In the presence of 2 microM trans-(E)-flupentixol chemoresistance to daunomycin was circumvented only in K562 cells transduced with wild-type, but not with mutant, MDR1. Moreover, drug resistance of KB-8-5 epidermoid cancer cells, which express the wild-type MDR1 gene at levels comparable to clinical specimens from multidrug-resistant cancers, was fully overcome in the presence of trans-(E)-flupentixol. Vectors expressing mutant P-glycoprotein may help improve chemotherapy by allowing safe dose intensification under conditions in which multidrug-resistant cancers are rendered drug sensitive by reversing agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Drug selection of MDR1-transduced hematopoietic cells ex vivo increases transgene expression and chemoresistance in reconstituted bone marrow in mice.

The MDR1 (multidrug resistance) gene, transferred to hematopoietic cells, is expected to protect them from anticancer chemotherapy and may serve as a selectable marker, restoring gene expression in vivo. Appropriate selection strategies, however, need to be established. To investigate whether preselection ex vivo affects chemoresistance, murine bone marrow cells were retrovirally transduced with high-titer or, as a model for suboptimal gene expression, low-titer retroviruses and exposed to daunomycin or colchicine for 48-96 h. Selection significantly increased chemoresistance of clonogenic progenitor cells. In tissue culture, the entire target population was rendered highly drug resistant after MDR1 transfer with high-titer viruses. If transduction was performed under suboptimal conditions, drug selection increased the frequency of chemoresistant colonies up to 40% over the number of unselected cells. Colchicine and daunomycin were equally efficient in increasing drug resistance ex vivo, but colchicine-preselected cells rescued lethally irradiated mice under conditions where daunomycin-selected bone marrow cells failed to do so. Hence, while hematopoietic cells can be protected by MDR1, the selection strategy is critical for repopulation of bone marrow with transduced cells. Preselection in culture before transplantation significantly increased P-gp expression and chemoresistance in vivo in mice reconstituted with transduced bone marrow cells. This study may help to facilitate the use of MDR1 as a selectable marker in gene therapy of the hematopoietic system. Gene Therapy (2000) 7, 348-358.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Targeting the human mdr1 gene by 125I-labeled triplex-forming oligonucleotides.

Antigene radiotherapy is our approach to targeting specific sites in the genome by combining the highly localized DNA damage produced by the decay of Auger electron emitters, such as 125I, with the sequence-specific action of triplex-forming oligonucleotides (TFO). As a model, we used the multidrug resistance gene (mdr1) overexpressed and amplified nearly 100 times in the human KB-V1 carcinoma cell line. Phosphodiester pyrrazolopyrimidine dG (PPG)-modified TFO complementary to the polypurine-polypyrimidine region of the mdr1 gene were synthesized and labeled with 125I-dCTP at the C5 position of two cytosines by the primer extension method. 125I-TFO were delivered into KB-V1 cells with several delivery systems. DNA from the 125I-TFO-treated cells was recovered and analyzed for sequence-specific cleavage in the mdr1 target by Southern hybridization. Experiments with plasmid DNA containing the mdr1 polypurine-polypyrimidine region and with purified genomic DNA confirmed the ability of the designed 125I-TFO to bind to and introduce double-strand breaks into the target sequence. We showed that 125I-TFO in nanomolar concentrations can recognize and cleave a target sequence in the mdr1 gene in situ, that is, within isolated nuclei and intact digitonin-permeabilized cells. Our results demonstrate the ability of 125I-TFO to target specific sequences in their natural environment, that is, within the eukaryotic nucleus. The nearly 100-fold amplification of the mdr1 gene in KB-V1 cells affords a very useful cell culture model for evaluation of methods to produce sequence-specific DNA double-strand breaks for gene-specific radiotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Influence of antipsychotic, antiemetic, and Ca(2+) channel blocker drugs on the cellular accumulation of the anticancer drug daunorubicin: P-glycoprotein modulation.

We investigated the effect of antiemetic, antipsychotic, and Ca(2+) blocker drugs on the function of P-glycoprotein (Pgp) in vitro and compared inhibitory concentrations with therapeutic blood levels. Human colon adenocarcinoma (Caco-2) and human blood-brain barrier endothelial cells were transfected or transduced to express Pgp, and the uptake of rhodamine123, calcein AM, or daunorubicin was measured by flow cytometry in the presence of the drugs. NIH3T3/MDR1 cells were used for reference testing. Results of the flow cytometric studies were supported by cell proliferation and monolayer permeability studies. Thirty-five drugs are included in this study, of which 13 modulate the function of Pgp at the therapeutic blood concentration and 8 at a concentration 2 to 4 times higher. Two drugs, which block the function of Pgp only partially at therapeutic blood concentrations, blocked the function of Pgp completely if used concomitantly. Based on these in vitro experiments, we conclude that administration of several drugs that modulate the function of Pgp simultaneously may adversely affect the natural function of this efflux pump and may cause drug-induced side effects in patients.

3T3 Cells↗
PubMed1999

Retroviral transfer of human MDR1 gene to hematopoietic cells: effects of drug selection and of transcript splicing on expression of encoded P-glycoprotein.

Protection of hematopoietic cells of patients undergoing anticancer chemotherapy by MDR1 gene transfer is currently being studied in clinical trials. From animal studies, it has been suggested that aberrant splicing due to cryptic donor and acceptor sites in the MDR1 cDNA could be a major reason for failure to obtain high-level expression of P-glycoprotein in bone marrow. We investigated effects of drug selection on protein expression levels and on splicing of MDR1 transcripts in murine bone marrow cells (BMCs) in vitro. To this end, retroviruses were generated through an identical plasmid, pHaMDR1/A, introduced into different packaging cells. GP + E86- but not PA317-derived producer cells were found to express truncated in addition to full-length message. In BMCs transduced with GP + E86-derived viruses, both messages were increased after treatment with colchicine or daunomycin. Similar results were obtained with NIH 3T3 fibroblasts. However, transduced and drug-selected BMCs displayed the spliced transcript even if the respective PA317-derived producer cells contained no truncated RNA as detected in transduced NIH 3T3 fibroblasts. Short-term drug selection in BMCs transduced with either ecotropic or amphotropic retroviruses resulted in a striking increase in P-glycoprotein expression. Thus, aberrant splicing failed to abrogate P-glycoprotein expression in BMCs. We also studied a vector in which MDR1 was coexpressed with glucocerebrosidase, using an internal ribosomal entry site. Although chemoprotection was less efficient than with pHaMDR1/A, augmentation of protein expression was observed at low selecting drug concentrations. Our study shows that drug selection can partially compensate for inefficient transduction of hematopoietic cells, and may help to develop strategies by which unstable expression of transduced genes can be overcome.

3T3 Cells↗
PubMed1998

Drug resistance of secondary acute myeloid leukemia with megakaryoblastic features and p190 BCR-ABL rearrangement.

A 46-year-old female presented with acute myeloid leukemia during complete remission of multiple myeloma after extensive treatment with alkylating agents. Leukemic blasts expressed CD34, platelet esterase and gp IIIa. RT-PCR analyses of peripheral blood cells detected a p190 type BCR-ABL rearrangement and high levels of MDR1. The patient expired during neutropenia shortly after induction chemotherapy. Autopsy revealed persistent blasts in the bone marrow, spleen and liver. 'Secondary' acute myeloid leukemia with megakaryoblastic features and p190-type BCR-ABL rearrangement has not previously been reported. The possibility that the combination of a BCR-ABL rearrangement with overexpression of MDR1 may have contributed to the treatment-refractory course is discussed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

In vivo drug-selectable genes: a new concept in gene therapy.

Chemoresistance genes, initially considered to be a major impediment to the successful treatment of cancer, may become useful tools for gene therapy of cancer and of genetically determined disorders. Various target cells are rendered resistant to anticancer drugs by transfer of chemoresistance genes encoding P-glycoprotein, the multidrug resistance-associated protein-transporter, dihydrofolate reductase, glutathione-S-transferase, O6-alkylguanine DNA alkyltransferase, or aldehyde reductase. These genes can be used for selection in vivo because of the pharmacology and pharmacokinetics of their substrates. In contrast, several other selectable marker genes conferring resistance to substrates like neomycin or hygromycin can only be utilized in tissue culture. Possible applications for chemoresistance genes include protection of bone marrow and other organs from adverse effects caused by the toxicity of chemotherapy. Strategies have also been developed to introduce and overexpress nonselectable genes in target cells by cotransduction with chemoresistance genes. Thereby expression of both transgenes can be increased following selection with drugs. Moreover, treatment with chemotherapeutic agents should restore transgene expression when or if expression levels decrease after several weeks or months. This approach may improve the efficacy of somatic gene therapy of hematopoietic disorders which is hampered by low or unstable gene expression in progenitor cells. In this article we review preclinical studies in tissue culture and animal models, and ongoing clinical trials on transfer of chemoresistance genes to hematopoietic precursor cells of cancer patients.

Animals↗
PubMed1997

Epidemiological features of Adamantiades-Behçet's disease in Germany and in Europe.

The German Registry of Adamantiades-Behçet's disease was founded in 1990 in Berlin and it provides current data on the epidemiology, the clinical manifestations and the course of the disease in Germany on a continuous basis. A total of 218 patients, including 89 German and 100 Turkish patients, had been reported to the German Registry until October 1997. One hundred and ninety-six patients fulfilled the criteria of the Behçet's disease classification tree. The prevalence of the disease evaluated in Berlin-West was 1.68/100,000 in 1989 and had risen to 2.26/100,000 by 1994. The median age of onset was 25 years (range 5 to 66 years; German-Turks, ns). Juvenile disease was recorded in 6.9% of patients. The complete clinical picture according to the criteria of the International Study Group of Behçet's Disease developed in 15.5 months. The interval between onset of the disease and diagnosis was 35 months, which was significantly longer than the duration of the development of the complete clinical picture (p < 0.0001). The disease was diagnosed later in German (48.5 months) than in Turkish patients (25.5 months, p = 0.003). While German patients presented an equal male-to-female ratio, a male predominance was shown in Turkish patients (M:F 2.1:1, p = 0.022). Familial occurrence was detected in 2.0% of German and 15.9% of Turkish patients (p = 0.013). The frequencies of major clinical manifestations were: oral ulcers 99%, skin lesions 76%, genital ulcers 75%, ocular manifestations 59%, arthritis 59%, and positive pathergy test 52%. Clinical differences between German and Turkish patients were only found in the frequency of ocular lesions (48% vs. 66%, p = 0.025). Oral ulcers were with 72% the most common onset symptom of the disease followed by erythema nodosum (9%), uveitis (7%), arthritis (7%), genital ulcers (3%), superficial thrombophlebitis (2%) and papules/sterile pustules (2%). Uveitis and erythema nodosum as onset symptoms shortened the median interval to diagnosis to 1.5 and 15 months, respectively, while arthritis delayed diagnosis (43.5 months; p = 0.029). A severe course developed in 25% of the patients; irreversible retinal vasculitis to blindness in 15%, sterile meningoencephalitis in 8%, severe arthritis in 5%, hemoptysis in 2%, lethal outcome in 2% and bowel perforation in 1%. The relative risk of HLA-B5 positive German natives developing the disease. HLA-B5 was confirmed as a marker of severe prognosis. Cardiolipin autoantibodies were associated with cutaneous vasculitis and superficial thrombophlebitis was correlated with systemic vessel involvement.

Adolescent↗
PubMed1996

Complete restoration of glucocerebrosidase deficiency in Gaucher fibroblasts using a bicistronic MDR retrovirus and a new selection strategy.

Retrovirus-mediated gene transfer is currently the most common method for the application of genetic therapy to cancer and many inherited and acquired disorders. Here we report the generation of an amphotropic producer cell line (CA2) that synthesizes viral particles carrying a bicistronic cassette in which the selectable MDR1 cDNA encoding P-glycoprotein (P-gp) a multidrug efflux pump, and the human glucocerebrosidase (GC) gene are transcriptionally fused. Transduction of human Gaucher fibroblasts with this recombinant virus allowed coordinate expression of P-gp and GC. Treatment of the transduced fibroblasts with various cytotoxic substrates of P-gp selected for cells with increased expression of GC, which paralleled the stringency of drug selection. Thus, selection of the genetically modified Gaucher fibroblasts in 1 microgram/ml colchicine raised their GC activity levels from nearly undetectable to those present in WI-38 normal human fibroblasts, correcting the enzyme deficiency present in Gaucher cells. Moreover, by simultaneously inhibiting the P-gp pump, it was possible to use much lower concentrations of colchicine to select for high-level expression of MDR1 and GC. Thus, selection with colchicine at 5 ng/ml in combination with the P-gp inhibitors verapamil or PSC 833 produced a complete correction of the GC deficiency in the CA2-transduced fibroblasts. These combination regimens, already in clinical use for the treatment of multidrug-resistant malignancies, may prove useful in gene therapy trials when utilized for high level selection of a nonselectable gene such as glucocerebrosidase when transcriptionally fused to the MDR1 gene.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Effect of combination of suboptimal concentrations of P-glycoprotein blockers on the proliferation of MDR1 gene expressing cells.

Pharmacologically active in vivo doses of P-glycoprotein (Pgp) blockers, specifically verapamil, Cremophor EL and PSC833 cause toxicity in addition to that from the concomitantly used cancer chemotherapeutic drugs. It was shown before that these blockers cause different types of toxicities in vivo. We found that these 3 chemically distinct Pgp blockers exert different biophysical effects on the membranes of L1210 MDR cells. They also affect the general metabolism of these cells differently, but all block affinity labeling of Pgp. We could also show that the combination of suboptimal doses of these blockers can restore the uptake of the Pgp substrate rhodamine 123 into L1210MDR, 3T3MDR and KB-VI cells and can reduce the survival rate of these cells when treated in combination with daunorubicin. Our results suggest that the combination of suboptimal doses of these Pgp blockers may be advantageous in clinical practice.

ATP Binding Cassette Transporter, Subfamily B, Mem↗