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Biomedical subjects

G P Georgiev

Publications and source records attributed to G P Georgiev.

At least 19 recordsLinked to original sources
PubMed2007

Axillary arch in Bulgarian population: clinical significance of the arches.

In order to study the incidence of the axillary arch in the Bulgarian population, we examined the axillary regions of 56 formol-carbol fixed human cadavers and observed two cases with a unilateral axillary arch. In the first case, the variant structure was situated on the right side of a 58-year-old female cadaver. The axillary arch extended from the lateral border of the latissimus dorsi to the posterior layer of the pectoralis major tendon. In the second case, the axillary arch was found on the left side of a 63-year-old male cadaver and had the same attachment points as in the first case. The innervation and blood supply of the arches are discussed. We have also reviewed extensive information concerning the clinical importance of the axillary arch, and for the first time, it was summarized clearly for clinicians. The summary consists of three parts: "diagnosis" of the axillary arch by physical investigation or imaging techniques; the axillary arch and surgical interventions in the region of the axilla; the axillary arch as an entrapment site for the axillary vessels and nerves.

Axilla↗
PubMed2005

Use of human VEGF(165) gene for therapeutic angiogenesis in coronary patients: first results.

The paper presents the first results of therapeutic angiogenesis in clinical cardiosurgery: human VEGF(165) gene transplantation to coronary patients. The use of this therapeutic method is particularly effective in patients with inoperable cardiovascular injuries, i.e. patients with the most severe condition, in whom treatment remains little effective at the modern level of cardiosurgery development.

Animals↗
PubMed2005

Methylation of DNA--one of the major epigenetic markers.

Regulation of gene expression is a complex process. It includes a great number of steps from control of mRNA synthesis to posttranslational modification of proteins. Epigenetic events play essential roles in regulation of transcription. In this review, we concentrate on methylation of DNA as one of the important epigenetic marks. It is well known that DNA methylation is associated with closed chromatin state and, therefore, repressed, inactive genes. Here we describe major processes that depend on DNA methylation: imprinting, X-inactivation, and oncogenesis. Also we describe a number of known methyl-DNA-binding proteins and links between methylation of DNA and higher-order chromatin structure.

Animals↗
PubMed2005

Phase I/II trial of gene therapy with autologous tumor cells modified with tag7/PGRP-S gene in patients with disseminated solid tumors: miscellaneous tumors.

BACKGROUND: The use of genetically modified autologous tumor cells appears to be a promising approach for cancer therapy. A phase I/II trial was undertaken to define the feasibility, safety and antitumor effects of the autologous vaccine prepared by transferring tag7/PGRP-S gene into malignant melanoma and renal cell carcinoma cells. PATIENTS AND METHODS: Twenty-one patients (17 with disseminated malignant melanoma and four with metastatic renal cell carcinoma) were enrolled in this study. Cytoreduction was performed in all cases prior to therapy. Autologous tumor cells were transfected with the tag7/PGRP-S gene, irradiated and injected intradermally every 3 weeks. RESULTS: Vaccinations were well tolerated by all patients, without clinically significant signs of toxicity. Delayed-type hypersensitivity was observed in 48% of cases. Antitumor immune response was observed in 95% of patients. There were no complete or partial responses; however, a minor response was achieved in one patient with renal cell carcinoma. The stabilization of neoplastic disease was observed in eight patients (seven with malignant melanoma and one with renal cell carcinoma). Median time to tumor progression was 3 months. CONCLUSIONS: The approach suggested here appears to be well tolerated and produces a number of durable clinical effects. Further studies are required to determine whether promising effects on immune activation will result in an actual clinical benefit for patients with malignant melanoma and renal cell carcinoma.

Adult↗
PubMed2005

[Melanoma cell lines as the basis for antitumor vaccine preparation].

The aim of the study was to obtain cell lines from tumor samples, and to determine phenotypic cell characteristics in order to choose the optimal line for vaccine preparation. 15 cell lines with stable growth, varying in cultural growth character and cytomorphology, were obtained from samples taken from patients with metastatic skin melanoma. Immunofluorescense method was used to determine the expression of T- and B-lymphocyte markers, antigens of major histocompatibility complex (MHC) class I and II, and CD86 co-stimulating molecule in the cell lines. The expression of melanocyte differentiation antigens and cancer/testicular antigens was evaluated using immunocytochemical assay. The results allowed the authors to distinguish three types of melanoma cell lines according to the expression of MHC molecules: MHC-negative; MHC class I positive; MHC classes I and II positive.

Antigens, Neoplasm↗
PubMed2004

Gene transfer approaches in cancer immunotherapy.

The idea of enhancing or establishing effective immune response against endogenously developed tumor cells is not novel. More than a hundred years ago, bacterial components were used to develop antitumor immune response. Later, when a number of immune system-effecting cytokines had been discovered, they were used for systemic treatment of cancer patients. However, systemic treatment often resulted in even negative outcome. Recent developments of genetic approaches of cell modifications allowed developing of modern techniques of targeted tumor cell elimination. In the present paper, we review modern trends of the antitumor response enhancement based on immunoregulatory gene transfer into different cell types both in vivo and in vitro. Almost all these approaches are based on the activation of the adaptive arm of the immune system in response to tumor cells. However, recent studies indicate that the innate arm of the immune system, as well as adaptive arm, is involved in tumor suppression. The innate immune system uses nonrearranging germline receptors, which could trigger cellular effector responses that are conditional (or instructive) to the subsequent adaptive immune response. Last years' viewpoints on 'self' and 'non-self' recognition and primary induction of the immune response have changed. The key role of lymphocytes is pathogen recognition and, following immune response induction, switched on the central role of dendritic cells in 'non-self' recognition and induction of both innate and adaptive responses. Moreover, innate response is supposed to be an essential starting point in induction of successful and effective acquired response. Most cancer vaccines do not have 'non-self' marks presentation due to their endogenous origin, thus lacking their effectiveness in the induction of the specific long-lasting immune response. Taking this point into consideration, we can conclude that to make cancer vaccine more effective we have to present tumor antigens, together with the molecules that can potentially activate downstream 'non-self' recognition events not in parallel, but as a consequence of tumor antigen processing and presentation.

Animals↗
PubMed2004

[Use of genetically modified embryonic stem cells for creating transgenic animals].

Targeted genetic modification of embryonic stem cells (ESC) was used to obtain nondifferentiated cell clones containing the foreign genetic material in the genome. It was demonstrated that transgenic animals may be obtained by ESC injection in preimplantation embryos and subsequent transplantation of the embryos into a recipient female. Using this method, we constructed chimeric animals with a modified genome.

Animals↗
PubMed2004

[Phase I-II trial of gene therapy with tag-7 modified autologous tumor cells in patients with metastatic solid tumors].

A prospective (phase I-II) trial was undertaken to study the efficacy and toxicity of gene therapy with tag 70-modified autologous tumor cells in 32 patients with metastatic renal cell carcinoma (RC) (5) and melanoma (MBL) (27) treated at the Institute's Clinic (2001-2003). Resected material was reduced to cell culture, which was transfected with tag 70 gene and devitalized by irradiation. Immune blotting was used for gene expression. Clinical and immunological effectiveness was evaluated in 22 patients (MBL--17 and RC--5) who received 1-6 injections (3 on the average). Full course of vaccination was given to 8 (MBL--6 and RC--2). No complete or partial response was reported while least regression (50%) was registered in a case of RC metastatic to the lung. According to CT and ultrasound evidence, stabilization was achieved in 5 (23.8%) (MBL--4 and RC--1). Relapse-free period was 6.5+/-3.5 months beginning from the start of treatment. The vaccine was well tolerated while DHT reaction was observed in 47.6% (10 out of 17) of primary immunized patients. A trend of increased content of T- and B-cells in peripheral blood and intensified functional activity was established.

Adult↗
PubMed2003

The differentially spliced mouse tagL gene, homolog of tag7/PGRP gene family in mammals and Drosophila, can recognize Gram-positive and Gram-negative bacterial cell wall independently of T phage lysozyme homology domain.

Tag7/PGRP, a recently characterized antimicrobial protein, is conserved from insects to mammals. Recently its involvement in Toll signalling in Drosophila was demonstrated. A number of genes representing a new family homologous to PGRP were identified in Drosophila and human. Here we describe a splicing pattern of the tagL gene, mouse member of tag7/PGRP family. Some of the identified splice variants lacked characteristics for the family T phage lysozyme homology domain (also known as PGRP domain). Accordingly to the predicted transmembrane domains, mouse TagL may be secreted as inducible proteins or retained on intracellular membranes. All detected splice variant isoforms of TagL bound Gram-positive, Gram-negative bacteria and peptidoglycan. This binding did not depend on the presence of T phage lysozyme homology domain but was associated with the C-terminal portion of the polypeptides. Thus, this variety of isoforms of a single gene may play a role in circulating bacteria recognition in mammals.

Alternative Splicing↗
PubMed2000

[Functional characteristics of the promoter region of the tag7/PGRP gene in KSML0, KSML100 murine mammary adenocarcinoma cell ines and VMR liver].

A study was carried out on the transcription regulation of the tag7/PGRP gene, whose product is similar to cytokines and is involved in recognizing peptidoglycane in mouse mammary adenocarcinoma cell lines KSML0, KSML100, and VMR-liver. The 3250-bp fragment of the promoter region was sequenced and tested for DNase I-hypersensitive sites (DHSs). In the KSML0 cells line, DHSs were found in the vicinity of the TATA box and approximately at position -3000 relative to the transcription start of the gene. Only a DHS cluster near the TATA box was found in the VMR-liver cell line. Regions involved in transcription regulation of the gene in the three cell lines were identified with the use of reporter constructions carrying the CAT gene under the control of deletion derivatives of the tag7/PGRP promoter region. The minimal promoter including only the TATA box with the nearest neighboring sequences was inactive in all cell lines. The elements (enhancers) positively regulating gene transcription in KSML0 and VMR-liver were mapped to region -192, -48. An element accounting for the transcriptional inactivity of the gene in KSML100 cells was assigned to region -315, -3250.

Adenocarcinoma↗
PubMed2000

[tag7 Gene and gene therapy of cancer].

Modern gene therapeutic approaches towards the treatment of malignant neoplasms are discussed. Specifically, results of the first experiments on the development of vaccines on the basis of tumor cells modified with various cytokines and activation molecules are described. We compare effectiveness of different cytokines used for modification of tumor cells are made and consider possible mechanisms of vaccine action. The reasons for impossibility of the development of effective endogenous antitumor immunity are examined. The results of comparative analysis of the Tag7 protein antitumor activity are presented. This evidence clearly shows that Tag7 is a promising agent for anticancer therapy.

Animals↗
PubMed2000

[Cloning and study of novel mammalian genes with structural homology with phage lysozyme].

The mouse tag7 gene was cloned and characterized in our previous works. This work is devoted to identifying and cloning its homologs. The human homolog of the tag7 gene was cloned. Data of analysis of the primary structure of the human tag7 and results from the study of the production of the corresponding protein in human organs and tissues indicate that this gene plays a major role in the mammalian immune system. The mouse and human tagL gene carrying an extended region of structural homology with the tag7 gene was detected by computer analysis and was subsequently cloned. Sequence analysis suggested the possible membrane localization of the gene, whereas the specific expression pointed to the role of this gene in the immune system. Both genes, tag7 and tagL, were localized in the human chromosome 19.

Amino Acid Sequence↗
PubMed1998

Molecular cloning and characterization of the mouse tag7 gene encoding a novel cytokine.

Cloning of the mouse tag7 gene encoding a novel cytokine is described. The Tag7 protein consists of 182 amino acids. Genomic organization of the tag7 gene and its promoter region remind those of the genes of the tumor necrosis factor locus, although the tag7 gene is not linked to this locus. The gene is located on chromosome 7 at the area that corresponds to band 7A3, which has genetic linkage with lupus-like disease in mouse models. tag7 transcription is essential for lymphoid organs. It is also detected in certain areas of lungs, brain, and intestine and in some tumors. Tag7 protein is detectable in both cell-associated and soluble forms. The soluble form of Tag7 triggers apoptosis in mouse L929 cells in vitro and does not involve NF-kappaB activation. The relationship between Tag7 and tumor necrosis factor family of ligands is discussed.

Amino Acid Sequence↗
PubMed1998

A minisatellite "core" element constitutes a novel, chromatin-specific activator of mts1 gene transcription.

Expression of the mts1 gene is often associated with malignant transformation of tumor cells. Transcription of the gene is controlled by a number of positive and negative regulatory elements, all of them being localized in the first intron (+38 to +1215) of the mts1 gene. Through analysis of the distribution of DNase I hypersensitive sites in the first intron of the gene we revealed a structurally conserved region that consisted of a non-canonical NFkB binding site and a minisatellite "core" element. Deletion of the minisatellite core DNA in the context of the first intron had no effect on its regulatory capacity when assayed in transient transfections, while a fivefold decrease was observed in a pool of stably transfected cells. The minisatellite core sequence CTGGGCAGGCAG is involved in DNA-protein interactions in vivo, and is similar to a binding site for the previously identified minisatellite DNA sequence binding protein (Msbp-1). The core DNA interacted in vitro with a protein that had an apparent molecular mass of 40 kDa. These data indicate that the minisatellite DNA represents the novel, chromatin-specific element in the mts1 complex enhancer.

Animals↗