Biomedical subjects

V Djonov

Publications and source records attributed to V Djonov.

15 recordsLinked to original sources

PubMed2001

Chorioallantoic membrane capillary bed: a useful target for studying angiogenesis and anti-angiogenesis in vivo.

The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane that is commonly used in vivo to study both angiogenesis and anti-angiogenesis. This review 1) summarizes the current knowledge about the structure of the CAM's capillary bed; 2) discusses the controversy about the existence of a single blood sinus or a capillary plexus underlying the chorionic epithelium; 3) describes a new model of the CAM vascular growth, namely the intussusceptive mode; 4) reports findings regarding the role played by endogenous fibroblast growth factor-2 in CAM vascularization; and 5) addresses the use and limitations of the CAM as a model for studying angiogenesis and anti-angiogenesis.

Allantois↗

PubMed2001

Expression of hypoxia-inducible factor-1alpha: a novel predictive and prognostic parameter in the radiotherapy of oropharyngeal cancer.

Hypoxia has long been recognized as detrimental to the successful treatment of malignant tumors with ionizing radiation. Because hypoxia-inducible factor (HIF)-1alpha plays an essential role in oxygen homeostasis in vitro, we explored the predictive potential of this factor in a cohort of 98 patients with squamous cell cancer of the oropharynx, who were treated by curative radiation therapy. Ninety-four % of the primary tumors showed overexpression of HIF-1alpha, relative to the surrounding tissue, as determined by immunohistochemistry. The degree of HIF-1alpha immunoreactivity correlated inversely with both the rate of complete remission of the primary tumor (odds ratio, 0.33; P = 0.03) and lymph node metastases (odds ratio, 0.34; P = 0.02) as well as with local failure-free survival (risk ratio, 2.15; P = 0.006), disease-free survival (risk ratio, 2.01; P = 0.008), and overall survival (risk ratio, 2.17; P = 0.002). The multivariate analysis revealed the predictive power of HIF-1alpha to be independent of other covariables. We conclude that HIF-1alpha is overexpressed in the vast majority of patients with squamous cell cancer of the oropharynx and that the degree of expression has predictive and prognostic significance in individuals undergoing curative radiation therapy.

Analysis of Variance↗

PubMed2001

Involvement of the hepatocyte growth factor/scatter factor receptor c-met and of Bcl-xL in the resistance of oropharyngeal cancer to ionizing radiation.

The activation of cytoplasmic signal transduction pathways by a number of growth factors and their tyrosine-kinase receptors, including hepatocyte growth factor/scatter factor (HGF/SF) and its receptor c-met, exerts an inhibitory influence on apoptosis induced by ionizing radiation in vitro. The clinical relevance of the aforementioned ligand-receptor pair, of Bcl-xL, which is targeted by HGF/SF/c-met signaling, and of Bcl-2, was assessed by evaluating their predictive and prognostic impact in a cohort of 97 patients with radically irradiated squamous cell cancers of the oropharynx. Immunohistochemical expression of c-met and Bcl-xL was correlated with decreased rates of complete remission of the primary tumor in both the univariate (c-met: P = 0.01; Bcl-xL: P = 0.001) and multivariate analyses. Expression of c-met was, moreover, a significant and independent predictor of impaired local failure-free survival (P = 0.003), disease-free survival (P = 0.003) and overall survival (p = 0.001). Bcl-2 expression was, on the other hand, associated with a favorable outcome, in terms of both local failure-free survival (P = 0.01) and overall survival (P = 0.001). In accordance with in vitro data, c-met and Bcl-xL appear to be involved in the resistance of oropharyngeal cancers to ionizing radiation, and may therefore represent attractive targets for radiosensitization.

Aged↗

PubMed2001

Vascular remodelling during the normal and malignant life cycle of the mammary gland.

The mammary gland life cycle is exemplified by massive, physiologically dictated changes in cell number and composition, architecture, and functionality. These drastic upheavals, by necessity, also involve the mammary endothelium, which undergoes angiogenic expansion during pregnancy and lactation followed by ordered regression during involution. In this review, we summarise data obtained using the Mercox methyl methacrylate corrosion cast technique to analyse the mammary gland vasculature during normal development and carcinogenesis. Concomitant with epithelial cell expansion, the mammary vasculature grows during the first half of pregnancy by sprouting angiogenesis whereas the last half of pregnancy and lactation are characterised by the non-proliferative intussusceptive angiogenesis. The vasculature of the lactating gland is composed of a well-developed capillary meshwork enveloping the secretory alveoli with basket-like honeycomb structures. During involution, regression of the vasculature is achieved by regional collapse of the honeycomb structures, capillary retraction, and endothelial attenuation. This process appears partly to involve apoptosis. However, an additional mechanism involving remodelling without cell death, which we have termed angiomeiosis, must exist to explain the morphological observations. Interestingly, in mammary tumours of neuT transgenic mice, both sprouting and intussusceptive angiogenesis was observed simultaneously in the same nodules, a finding with potential implications for cancer therapy. The underlying molecular mechanisms controlling angiogenic modulation in the mammary gland, particularly angiogenic regression and the endothelial:parenchymal interplay, are poorly understood. However, the data summarised in this review indicate that precisely these molecular mechanisms offer novel alternatives for specific and effective treatment of breast cancer.

Animals↗

PubMed2001

MMP-19: cellular localization of a novel metalloproteinase within normal breast tissue and mammary gland tumours.

Matrix metalloproteinases (MMPs) are instrumental in promoting and facilitating the spread of malignant diseases and in the de novo formation of blood vessels. This study has mapped the immunoreactivity of a novel, angiogenesis-related metalloproteinase--MMP-19--in normal breast tissue and in benign and malignant breast lesions and compared this pattern of expression with that of MMP-2. In the normal resting mammary gland, MMP-19 was strongly expressed in the myoepithelial layer of the ductal system; the alveolar and ductal epithelia displayed considerable, but lobule-specific, variations in labelling intensity. MMP-19 was also present within the smooth muscle and endothelial layers of large and medium-sized blood vessels, as well as within capillary walls. In benign lesions, all tumour cells and their surrounding vasculature were uniformly and strongly immunoreactive for MMP-19. Progression towards an invasive phenotype and neoplastic dedifferentiation led to the disappearance of MMP-19 from tumour cells and blood vessels and a concomitant rise in the levels of MMP-2. In vitro experiments conducted with isolated smooth muscle cells cultivated on a solid substratum, or within the interstices of a collagen matrix, indicated that the expression of MMP-19 is influenced by the architecture of the surrounding extracellular matrix.

Adolescent↗

PubMed2000

Intratumoral microvessel density predicts local treatment failure of radically irradiated squamous cell cancer of the oropharynx.

PURPOSE: To determine the predictive value of intratumoral microvessel density (IMD), and of the expression of p53, vascular endothelial growth factor (VEGF) and thrombospondin-1 (TSP-1) for the radiocurability of patients with squamous cell cancer of the oropharynx. MATERIALS AND METHODS: 139 patients with squamous cell cancer of the oropharynx were radically irradiated (median dose, 74 Gy) between 1991 and 1997. Biopsies from 100 patients were processed for immunohistochemistry. IMD was determined in hot spot areas of tissue stained with anti-CD31 at a magnification of x200. Staining for p53 was considered positive if more than 10% of the cell nuclei overexpressed the protein. Immunostaining of VEGF and TSP-1 was assessed semiquantitatively. RESULTS: Increasing IMD (range, 54-282) was strongly correlated with incomplete remission of both the primary tumors (p = 0.01) and lymph node metastases (p = 0.02). Moreover, multivariate Cox regression analysis revealed local failure-free survival to decline with increasing IMD (IMD continuous: risk ratio = 1.01 per increase of 1 microvessel, p = 0. 0001; IMD categorical: </= 80: baseline, 81-110: risk ratio = 2.71, 111-130: risk ratio = 4.55, > 130: risk ratio = 13.01). Neither the expression of p53, nor that of VEGF or TSP-1 was associated with the treatment outcome or IMD, but VEGF and TSP-1 expression were positively correlated (p = 0.02). CONCLUSION: IMD represents a powerful and independent predictive factor for local treatment failure in radically irradiated patients with squamous cell cancer of the oropharynx.

Analysis of Variance↗

PubMed2000

Intussusceptive angiogenesis: its role in embryonic vascular network formation.

Intussusceptive angiogenesis is a novel mode of blood vessel formation and remodeling, which occurs by internal division of the preexisting capillary plexus without sprouting. In this study, the process is demonstrated in developing chicken eye vasculature and in the chorioallantoic membrane by methylmethacrylate (Mercox) casting, transmission electron microscopy, and in vivo observation. In a first step of intussusceptive angiogenesis, the capillary plexus expands by insertion of numerous transcapillary tissue pillars, ie, by intussusceptive microvascular growth. In a subsequent step, a vascular tree arises from the primitive capillary plexus as a result of intussusceptive pillar formation and pillar fusions, a process we termed "intussusceptive arborization." On the basis of the morphological observations, a 4-step model for intussusceptive arborization is proposed, as follows: phase I, numerous circular pillars are formed in rows, thus demarcating future vessels; phase II, formation of narrow tissue septa by pillar reshaping and pillar fusions; phase III, delineation, segregation, growth, and extraction of the new vascular entity by merging of septa; and phase IV, formation of new branching generations by successively repeating the process, complemented by growth and maturation of all components. In contrast to sprouting, intussusceptive angiogenesis does not require intense local endothelial cell proliferation; it is implemented primarily by rearrangement and attenuation of the endothelial cell plates. In summary, transcapillary pillar formation, ie, intussusception, is a central and probably widespread process, which plays a role not only in capillary network growth and expansion (intussusceptive microvascular growth), but also in vascular plexus remodeling and tree formation (intussusceptive arborization).

Allantois↗

PubMed1999

Sorting of murine vascular smooth muscle cells during wound healing in the chicken chorioallantoic membrane.

The vascular wall is built up of a heterogeneous population of smooth muscle cells, which exhibit not only morphological distinctions but also important differences in the composition of their structural and contractile proteins. "Epithelioid" smooth muscle cells correspond to an intimal-like type and display features associated with immaturity, whereas "spindle-shaped" cells closely resemble the more typical medial smooth muscle population. We have investigated the integration of these two cell types into the vascular architecture of an in vivo wound-healing model. Stably transfected with the beta-galactosidase gene, intima- and media-like cells were injected intravenously into the chicken chorioallantoic membrane, within which superficial foci of granulation tissue had been created by thermal or chemical injury. At 24 to 72 h after injection, cells had honed in on the lesion sites and were observed in juxtaposition to the endothelial lining of the capillaries. They began to deposit laminin, thereby indicating an impending role in the formation of the vascular wall. Intima- and media-like smooth muscle cells did not differ in their capacity to associate with capillaries, and, in so doing, their biochemical lineage characteristics became indistinguishable from one another. However, intima-like cells also penetrated the adventitial and medial layers of arteries. These findings reveal vascular smooth muscle cells to possess an extraordinary degree of plasticity, being able to adapt flexibly to changes in functional demands.

Allantois↗

PubMed1998

Expression of smooth muscle markers in the developing murine lung: potential contractile properties and lineal descent.

Contractile cells in the mammalian lung develop in close association with the outgrowing stem bronchi. Fully differentiated smooth muscle cells are typically found in proximal regions, residing in the substantial muscular walls of the major airways and blood vessels. More distally, cells expressing markers of differentiated smooth muscle cells to a variable degree, and which may therefore possess contractile properties, are to be found scattered around the interstitium. We have investigated the temporal and spatial distribution of smooth muscle lineage markers (smooth muscle myosin mRNA) and of those indicative of contractile function (metavinculin mRNA) in the murine lung. In the smooth muscle layers of the bronchi and major blood vessels, these genes are expressed from the onset of pulmonary budding, concurrently with the appearance of alpha-smooth muscle actin and calponin proteins. During fetal development, smooth muscle-associated genes and proteins are restricted to this committed smooth muscle population. The first signs of myofibroblast or pericyte differentiation become manifest perinatally, when their expression of alpha-smooth muscle actin escalates. In the adult lung, such cells may be readily pin-pointed by their positive reaction for metavinculin mRNA, but, at maturity, they do not always coexpress alpha-smooth muscle actin.

Actins↗

PubMed1998

Programmed cell death contributes to postnatal lung development.

The rat lung undergoes the phase of maturation of the alveolar septa and of the parenchymal microvascular network mainly during the third postnatal week. Speculating that programmed cell death may contribute to the thinning of the alveolar septa, we searched for the presence of DNA fragmentation in rat lungs between postnatal days 6 and 36 using the TUNEL procedure. The number of positive nuclei was compared at different days. We observed an 8-fold increase of programmed cell death toward the end of the third week as compared to the days before and after this time point. The precise timing of the appearance of the peak depended on the size of the litter. Double-labeling for DNA fragmentation (TUNEL) and for type I and type II epithelial cells (antibodies E11 and MNF-116), as well as morphologic studies at electron microscopic level, revealed that during the peak of programmed cell death mainly fibroblasts and type II epithelial cells were dying. While both dying cell types were TUNEL-positive, nuclear fragments and apoptotic bodies were exclusively observed in the dying fibroblasts. We conclude that programmed cell death is involved in the structural maturation of the lung by reducing the number of fibroblasts and type II epithelial cells in the third postnatal week. We observed that the dying fibroblasts are cleared by neighboring fibroblasts in a later stage of apoptosis, and we hypothesize that type II epithelial cells are cleared by alveolar macrophages in early stages of the programmed cell death process.

Aging↗

PubMed1998

Cell-type specific and estrogen dependent expression of the receptor tyrosine kinase EphB4 and its ligand ephrin-B2 during mammary gland morphogenesis.

Morphogenesis of the mammary gland occurs mainly during adult life and is dependent on a complex interplay of hormonal, cell-cell and cell-matrix interactions. The molecular mechanisms involved in pattern formation of the mammary epithelium in adult life are poorly understood. Recently, several members of the Eph family of receptor tyrosine kinases and their ligands have been shown to participate in pattern formation during embryogenesis and conceivably may fulfill similar functions during adult morphogenesis. We have investigated the expression of a member of this family, EphB4, and its cognate ligand, ephrin-B2, during normal and malignant mouse mammary morphogenesis. A spatially, temporarily and hormonally coordinated expression of both the receptor and ligand was observed. The receptor was predominantly localized in the myoepithelial cells surrounding the ducts and alveoli whereas ligand expression was limited to the luminal epithelial cells. Expression of both was induced at the onset of gland morphogenesis at puberty and was differentially regulated during the estrus cycle. Ovariectomy of pre-pubertal or adult females abolished the expression of both receptor and ligand and administration of estrogen alone was sufficient to restore their normal expression. Disruption of the balanced expression was observed during experimental mouse mammary carcinogenesis. Ligand expression was lost at the onset of tumorigenesis and receptor expression shifted from myoepithelial to epithelial cells with progressive malignancy. These results implicate both the EphB4 receptor and its ligand ephrin-B2 in the hormone dependent morphogenesis of the mammary gland. Furthermore, their deregulated expression may contribute to mammary carcinogenesis.

Animals↗

PubMed1997

A novel family of serine/threonine kinases participating in spermiogenesis.

The molecular mechanisms regulating the spectacular cytodifferentiation observed during spermiogenesis are poorly understood. We have recently identified a murine testis-specific serine kinase (tssk) 1, constituting a novel subfamily of serine/threonine kinases. Using low stringency screening we have isolated and molecularly characterized a second closely related family member, tssk 2, which is probably the orthologue of the human DGS-G gene. Expression of tssk 1 and tssk 2 was limited to the testis of sexually mature males. Immunohistochemical staining localized both kinases to the cytoplasm of late spermatids and to structures resembling residual bodies. tssk 1 and tssk 2 were absent in released sperms in the lumen of the seminiferous tubules and the epididymis, demonstrating a tight window of expression restricted to the last stages of spermatid maturation. In vitro kinase assays of immunoprecipitates containing either tssk 1 or tssk 2 revealed no autophosphorylation of the kinases, however, they led to serine phosphorylation of a coprecipitating protein of approximately 65 kD. A search for interacting proteins using the yeast two-hybrid system with tssk 1 and tssk 2 cDNA as baits and a prey cDNA library from mouse testis, led to the isolation of a novel cDNA, interacting specifically with both tssk 1 and tssk 2, and encoding the coprecipitated 65-kD protein phosphorylated by both kinases. Interestingly, expression of the interacting clone was also testis specific and paralleled the developmental expression observed for the kinases themselves. These results represent the first demonstration of the involvement of a distinct kinase family, the tssk serine/threonine kinases, together with a substrate in the cytodifferentiation of late spermatids to sperms.

Amino Acid Sequence↗

PubMed1997

Transforming growth factor-beta 3 is expressed in nondividing basal epithelial cells in normal human prostate and benign prostatic hyperplasia, and is no longer detectable in prostate carcinoma.

BACKGROUND: We investigated the role of the transforming growth factor beta (TGF-beta) family in the neoplastic progression of the human prostate. METHODS: Expression of TGF-beta mRNA was measured by Northern blot analysis of tissue extracts, and TGF-beta protein by immunohistochemical analysis of tissue sections. Proliferating cells were detected by their expression of Ki-67 antigen. RESULTS: The level of TGF-beta 1 mRNA was equal among normal prostate, benign prostatic hyperplasia (BPH), and prostate carcinoma. TGF-beta 2 mRNA was not detectable, and TGF-beta 3 mRNA was expressed 20-fold lesion in carcinoma compared to BPH and normal prostate. TGF-beta 1 protein was expressed in the stromal cells in all three tissues and TGF-beta 3 protein in the basal layer of epithelial cells, but not in carcinoma. Proliferating epithelial cells fail to express TGF-beta 3. CONCLUSIONS: TGF-beta 1 and TGF-beta 3 are independently regulated, and carcinoma of the prostate is characterized by the loss of basal epithelial cells expressing TGF-beta 3.

Adult↗

PubMed1995

Protein tyrosine kinase expression during the estrous cycle and carcinogenesis of the mammary gland.

The susceptibility of the mammary epithelium to neoplastic transformation is linked to the exposure to estrogen during the estrous cycle. The effects of the estrous cycle on the mouse mammary gland have been investigated by analyzing 3H-thymidine incorporation, milk protein gene expression and DNA fragmentation. We found that the mammary epithelium undergoes limited proliferation, differentiation and apoptosis in a cycle-dependent manner. The estrous-responsive regulators of the mammary epithelium are unknown; however, considering the integral role of protein tyrosine kinases (PTKs) in the control of normal and malignant development, members of this family of enzymes are likely candidates for such regulatory molecules. Using a RT-PCR-based cloning strategy, we have undertaken a survey of PTKs expressed in the mammary gland at defined stages of development, with special emphasis on the estrous cycle. We identified 21 known and 4 novel PTKs. Their expression was analyzed throughout mammary gland development and in mammary neoplasias using a transgenic mouse model for invasive and non-invasive carcinogenesis. Most of the identified PTKs showed highest expression during the estrous cycle and were down-regulated during pregnancy and lactation. Deregulated expression was rarely observed in the non-invasive mammary tumors. In contrast, 10 of 19 PTKs expressed during the estrous cycle were also over-expressed in the invasive carcinomas, mostly involving members of the receptor family of PTKs.

Amino Acid Sequence↗

PubMed1994

Expression of stromelysin-1 and TIMP-1 in the involuting mammary gland and in early invasive tumors of the mouse.

The mammary gland, during post-lactational involution, is subjected to extensive tissue reconstruction. This process is governed by the concerted expression of extracellular-matrix-degrading enzymes and their inhibitors. During carcinogenesis, the invasive growth of tumor cells is characterized by the penetration of the basement membrane and stromal invasion. We compared the expression of the tissue-remodeling enzymes stromelysin-1, a matrix metalloproteinase, and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), during mammary gland involution and carcinogenesis in mouse. In involuting mammary glands, stromelysin-1 was expressed in myoepithelial cells, whereas TIMP-1 was confined to the stromal tissue. To analyze the involvement of these tissue-remodeling genes in tumor development, we examined mammary tumors of transgenic mice expressing either the activated Ha-ras or c-myc oncogene under the control of a milk-protein gene promoter. In the undifferentiated and metastasizing Ha-ras-induced tumors, stromelysin-1 expression was comparable to that seen in involution, whereas TIMP-1 expression was greatly elevated. During Ha-ras-induced carcinogenesis, stromelysin-1 expression was first detected in the myo-epithelial cells surrounding preneoplastic lesions. In contrast, in the well-differentiated and non-metastatic mammary tumors induced by c-myc, no expression of either gene was observed. Thus, expression of stromelysin-1 and TIMP-1 is confined to the aggressively growing tumors and is induced in the earliest stages of carcinogenesis.

Animals↗