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Biomedical subjects

Athanasios G Papavassiliou

Publications and source records attributed to Athanasios G Papavassiliou.

52 records · Page 3Linked to original sources
PubMed2003

Selective modulation of postmenopausal women: cutting the Gordian knot of hormone replacement therapy with breast carcinoma.

BACKGROUND: Hormone replacement therapy (HRT) has proven and presumable benefits for women desiring postmenopausal health preservation. Among HRT-associated risks, the fear of breast carcinoma intimidates women and physicians contemplating hormonal treatment and limits long-term compliance. Identifying effective alternative medications that are not associated with breast carcinoma or that even may prevent its development would be a major advance. METHODS: This article discusses the clinical perspective of HRT and selective estrogen receptor modulators (SERMs) in light of the molecular and cellular mechanisms of estrogen and progesterone action on the breast. Emphasis is placed on the potential of selective receptor modulation as the future of postmenopausal treatment. RESULTS: Current epidemiologic evidence suggests that HRT is associated with a small but substantial increase in the risk of breast carcinoma, and combined estrogen-progesterone regimens further increase this hazard. Ample biologic data support this clinical association and propose multiple molecular mechanisms for the effects of estrogen and progesterone on breast cells. SERMs are a novel class of drugs that demonstrate estrogen agonistic and antagonistic actions in a tissue specific manner. SERMs act by binding the estrogen receptor and selectively modulating its effect on gene transcription at target tissues. CONCLUSIONS: SERMs offer an alternative to HRT that can successfully circumvent the intimidating side-effect of breast carcinoma. Further insight into the molecular mechanisms of SERM action may enable the development of agents with improved target-tissue selectivity. Identifying selective modulators with unique pharmacologic properties would facilitate the creation of individualized treatment for the postmenopausal woman according to her particular predisposition for menopause-related morbidities and her overall clinical profile.

Breast Neoplasms↗
PubMed2003

The alpha2B adrenergic receptor deletion/insertion polymorphism in morbid obesity.

The sympathetic nervous system participates in the regulation of the basal metabolic rate (BMR) and in the manifestation of the obesity-related metabolic syndrome. A deletion/insertion germline polymorphism of the alpha(2B) adrenergic receptor that is associated with reduced agonist-promoted desensitization has been linked to low BMR in obese subjects and to a predisposition to gain weight. This study investigated an association of the alpha(2B) polymorphism with the BMR and metabolic syndrome-related parameters of morbidly obese patients. Genotype frequencies were similar in patients and in a control group. The patients' BMR, adjusted for fat-free mass, fat mass, sex and age, did not differ between alpha(2B) genotypes. The polymorphism was also not associated with the patients' BMI, systolic and diastolic blood pressure, resting heart rate, total and HDL cholesterol, triglycerides, fasting glucose and uric acid levels. These findings do not support a major functional significance of the alpha(2B) adrenergic receptor polymorphism in the present sample of morbidly obese subjects.

Adolescent↗
PubMed2003

Autonomously functioning thyroid nodules in a former iodine-deficient area commonly harbor gain-of-function mutations in the thyrotropin signaling pathway.

BACKGROUND: Somatic activating mutations of the thyrotropin (thyroid-stimulating hormone (TSH)) receptor (TSHR) and G(alphas) protein have been detected in solitary toxic adenomas and toxic multinodular goiters, but their role in the pathogenesis of autonomous nodules is debated. The frequency of mutations is highly variable among populations and is inversely proportional to iodine intake. DESIGN AND PATIENTS: We screened 28 clinically and histologically heterogeneous autonomous nodules from 24 Greek patients for the presence of TSHR and G(alphas) mutations. RESULTS: By direct sequencing of genomic DNA, we detected 11 somatic heterozygous gain-of-function mutations in TSHR and one in G(alphas). Forty-three percent (12 of 28) of all nodules and 57% (four of seven) of solitary toxic adenomas harbored an activating mutation. Typical adenomas and hyperplastic nodules did not differ in mutation frequency. Substitutions I568T and T632I were detected in both histological types of nodules. CONCLUSIONS: Our findings indicate that activating somatic mutations in the TSH signaling pathway are frequent in autonomous nodules in Greece. This may be due to earlier exposure of the population to iodine deficiency, which was corrected in Greece only over the past two decades. Gain-of-function mutations are shared by nodules with varying histological and clinical presentations. Thus, they may represent a common molecular mechanism underlying the pathogenesis of non-autoimmune thyroid autonomy.

Adenoma↗
PubMed2002

Non-palpable breast carcinomas: correlation of mammographically detected malignant-appearing microcalcifications and molecular prognostic factors.

Screening mammography has greatly increased the number of non-palpable breast carcinomas diagnosed in asymptomatic women. Malignant-appearing microcalcifications represent one of the earliest mammographic findings of non-palpable breast carcinomas. Many studies have attempted to correlate radiological and histological features of malignant-appearing microcalcifications. In the present study, we evaluated the association between mammographically detected malignant-appearing microcalcifications and the expression profile of selected biological markers in non-palpable breast carcinomas. Two hundred and eighty patients with non-palpable suspicious breast lesions that were detected during screening mammography were studied. All patients underwent mammographically-guided needle localization-excision breast biopsy. Histological examination showed 74 (26.4%) carcinomas of various subtypes. Immunohistochemistry was carried out in 58/74 carcinomas by using a panel of monoclonal and polyclonal antibodies against estrogen receptor (ER), progesterone receptor (PR), HER-2/neu, Bcl-2, Bax, Fas and DNA fragmentation factor (DFF). Malignant-appearing microcalcifications was the major mammographic finding in 45/58 (77%) patients. Nuclear ER positivity (65.5%) and PR positivity (46.5%) of non-palpable breast carcinomas were statistically correlated with malignant-appearing microcalcifications (p < 0.01 and p < 0.05, respectively). Statistically significant associations were also found between malignant-appearing microcalcifications and HER-2/neu positivity (p < 0.01), Bax positivity (p < 0.01), Fas positivity (p < 0.05) and DFF positivity (p < 0.01), whereas no statistical correlation was found with Bcl-2 positivity (p > 0.05). Malignant-appearing microcalcifications detected during screening mammography represent a diagnostic, prognostic and therapeutic challenge. The mammographic/biological associations and their potential implications in the management of women with non-palpable breast carcinomas are thoroughly discussed.

Adult↗
PubMed2002

The bone-specific transcriptional regulator Cbfa1 is a target of mechanical signals in osteoblastic cells.

A primary goal of bone research is to understand the mechanism(s) by which mechanical forces dictate the cellular and metabolic activities of osteoblasts, the bone-forming cells. Several studies indicate that osteblastic cells respond to physical loading by transducing signals that alter gene expression patterns. Accumulated data have documented the fundamental role of the osteoblast-specific transcription factor Cbfa1 (core-binding factor) in osteoblast differentiation and function. Here, we demonstrate that low level mechanical deformation (stretching) of human osteoblastic cells directly up-regulates the expression and DNA binding activity of Cbfa1. This effect seems to be fine tuned by stretch-triggered induction of distinct mitogen-activated protein kinase cascades. Our novel finding that activated extracellular signal-regulated kinase mitogen-activated protein kinase physically interacts and phosphorylates endogenous Cbfa1 in vivo (ultimately potentiating this transcription factor) provides a molecular link between mechanostressing and stimulation of osteoblast differentiation. Elucidation of the specific modifiers and cofactors that operate in this mechanotranscription circuitry will contribute to a better understanding of mechanical load-induced bone formation which may set the basis for nonpharmacological intervention in bone loss pathologies.

Cells, Cultured↗
PubMed2002

The insertion of an anti-MHC I ScFv into the N-terminus of an ecotropic MLV glycoprotein does not alter its fusiogenic potential on murine cells.

It is known that targeted infection requires the modification of the viral envelope, in order to render it capable of recognizing and specifically binding to a marker protein of the target cell. We have previously described such a recombinant envelope, which is able to extend the tropism of an ecotropic murine leukemia viruses (MLV) envelope to MHC I-expressing human cells. Although, this envelope was very efficient in binding human cells, it yielded very low infection titers. Our attempts to improve these yields by the additional cloning of a variety of spacers in the proximity of the single-chain variable fragment (ScFv) moiety did not significantly influenced human titers, although some alterations on murine titers were observed. To examine whether these low yields represent a decreased fusion capacity of the recombinant envelopes, we performed an assay which allowed the direct comparison between the fusiogenicity of the wild-type (w/t) and the chimeric envelopes. No fusiogenicity of the chimeric envelopes was observed when chimera-expressing cells were co-cultured with human cells. The inability of the chimeras to induce fusion after binding of the ScFv moiety to its ligand may explain, in part, the low infection titers on human cells. However, the several-fold differences observed between the titers of the w/t envelope and the various chimeras on murine cells were not reflected on their fusiogenic potentials, which were all in the same order of magnitude. Our results demonstrate that the binding of the ScFv moiety to its ligand induces no fusion, albeit its insertion into the envelope does not alter the intrinsic fusiogenic ability of the latter. Induction of fusion results from the binding of the envelope to the ecotropic receptor, without being directly proportional to its binding affinity. Chimeras with different infection titers on murine cells yielded similar syncytia counts after their binding to the ecotropic receptor.

Animals↗
PubMed2002

Effect of protein kinase inhibitors on the stretch-elicited c-Fos and c-Jun up-regulation in human PDL osteoblast-like cells.

Osteoblastic cells transduce signals of mechanical loading that plays a key role in maintaining bone formation. In an attempt to elucidate the biochemical events associated with the conversion of mechanical stress to biological outcome, we examined cultured human periodontal ligament (hPDL) osteoblastic cells exposed to continuous stretch, in terms of cellular parameters correlating known signaling cascades to the initial phase of osteoblast-specific transcriptional control. Time-course experiments revealed that mechanical stretch-loaded hPDL cells exhibit a very rapid and relatively sustained increase in the abundance of the immediate-early gene products, c-Fos and c-Jun, components of the activator protein-1 (AP-1) transcription factor. Moreover, this increase in protein levels was accompanied by hyperphosphorylation and thereby potentiation of c-Jun, the principal modulator of AP-1 activity. Importantly, these inductive effects were partly or completely abolished by pre-incubating the cells with SB 203580, PD 098059, and the novel compound Y-27632, inhibitors of p38 mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), and Rho-associated protein kinase (RhoK), respectively. These results consolidate AP-1 as the pivotal downstream effector in the early response of hPDL cells to continuous mechanical stretching, via the coordinate stimulation of de novo synthesis and post-translational regulation of AP-1 proteins. This "integrating" function of AP-1 is mediated through a mechanotransduction circuit that incorporates elements of well-defined upstream signaling protein kinase systems.

Amides↗
PubMed2002

Transcription factor E2F-1 acts as a growth-promoting factor and is associated with adverse prognosis in non-small cell lung carcinomas.

Numerous upstream stimulatory and inhibitory signals converge to the pRb/E2F pathway, which governs cell-cycle progression, but the information concerning alterations of E2F-1 in primary malignancies is very limited. Several in vitro studies report that E2F-1 can act either as an oncoprotein or as a tumour suppressor protein. In view of this dichotomy in its functions and its critical role in cell cycle control, this study examined the following four aspects of E2F-1 in a panel of 87 non-small cell lung carcinomas (NSCLCs), previously analysed for defects in the pRb-p53-MDM2 network: firstly, the status of E2F-1 at the protein, mRNA and DNA levels; secondly, its relationship with the kinetic parameters and genomic instability of the tumours; thirdly, its association with the status of its transcriptional co-activator CBP, downstream target PCNA and main cell cycle regulatory and E2F-1-interacting molecules pRb, p53 and MDM2; and fourthly, its impact on clinical outcome. The protein levels of E2F-1 and its co-activator CBP were significantly higher in the tumour area than in the corresponding normal epithelium (p<0.001). E2F-1 overexpression was associated with increased E2F-1 mRNA levels in 82% of the cases examined. The latter finding, along with the low frequency of E2F-1 gene amplification observed (9%), suggests that the main mechanism of E2F-1 protein overexpression in NSCLCs is deregulation at the transcriptional level. Mutational analysis revealed only one sample with asomatic mutation at codon 371 (Glu-->Asp) and one carrying a polymorphism at codon 393 (Gly-->Ser). Carcinomas with increased E2F-1 positivity demonstrated a significant increase in their growth indexes (r=0.402, p=0.001) and were associated with adverse prognosis (p=0.033 by Cox regression analysis). The main determinant of the positive association with growth was the parallel increase between E2F-1 staining and proliferation (r=0.746, p<0.001), whereas apoptosis was not influenced by the status of E2F-1. Moreover, correlation with the status of the pRb-p53-MDM2 network showed that the cases with aberrant pRb expression displayed significantly higher E2F-1 indexes (p=0.033), while a similar association was noticed in the group of carcinomas with deregulation of the p53-MDM2 feedback loop. In conclusion, the results suggest that E2F-1 overexpression may contribute to the development of NSCLCs by promoting proliferation and provide evidence that this role is further enhanced in a genetic background with deregulated pRb-p53-MDM2 circuitry.

Biomarkers, Tumor↗
PubMed2002

Transcription factors and neoplasia: vistas in novel drug design.

PURPOSE: The fundamental role of gene transcription and the recognition of transcription factors as important control elements of cell growth, differentiation, and programmed cell death (apoptosis) aroused an ever-increasing interest for these proteins as potential pharmaceutical targets for therapeutic intervention in various diseases, among them cancer. EXPERIMENTAL DESIGN-RESULTS: The vast array of information available for their molecular architecture and mode of action in various biological contexts, combined with the new opportunities offered by the flourishing technologies of structure-based drug design, computer-aided modeling, and functional genomics/proteomics, are creating an exciting scenery for the development of a novel generation of highly selective drugs. CONCLUSIONS: This transcription factor-based therapeutic approach may revolutionize the anticancer drug options and will add significantly to the current clinical armamentarium.

Antineoplastic Agents↗
PubMed2002

Genetic and molecular coordinates of neuroendocrine lung tumors, with emphasis on small-cell lung carcinomas.

The aim of this review is to present the advances in our understanding of the progression of tumorigenesis in neuroendocrine lung tumors. Current information on established and putative diagnostic and prognostic markers of neuroendocrine tumors are evaluated, with a special reference to small-cell lung carcinoma, due to its higher incidence and aggressive behavior. The genetic and molecular changes that accompany these neoplasms are highlighted, and factors that influence cell-cycle progression, apoptosis, drug resistance, and escape from immune surveillance are critically assessed.

Apoptosis↗
PubMed2002

The progression in the mouse skin carcinogenesis model correlates with ERK1/2 signaling.

BACKGROUND: The ras family of proto-oncogenes encodes for small GTPases that play critical roles in cell-cycle progression and cellular transformation. ERK1/2 MAP kinases are major ras effectors. Tumors in chemically treated mouse skin contain mutations in the Ha-ras proto- oncogene. Amplification and mutation of Ha-ras has been shown to correlate with malignant progression of these tumors. Cell lines isolated from mouse skin tumors represent the stages of tumor development, such as the PDV:PDVC57 cell line pair and B9 squamous carcinoma and A5 spindle cells. PDVC57 cells were selected from PDV cells, which were transformed with dimethyl-benzanthracene (DMBA) in vitro and then transplanted in adult syngeneic mice. The PDV:PDVC57 pair contains ratio of normal:mutant Ha-ras 2:1 and 1:2, respectively. This genetic alteration correlates with more advanced tumorigenic characteristics of PDVC57 compared to PDV. The squamous carcinoma B9 cell clone was isolated from the same primary tumor as A5 spindle cell line. The mutant Ha-ras allele, also present in B9, is amplified and overexpressed in A5 cells. Therefore these cell line pairs represent an in vivo model for studies of Ha-ras and ERK1/2 signaling in mouse tumorigenesis. MATERIALS AND METHODS: The ERK1/2 status in the above mouse cell lines was examined by using various molecular techniques. For the study of the tumorigenic properties and the role of the ras/MEK/ERK1/2 pathway in the cell lines mentioned, phenotypic characteristics, colony formation assay, anchorage-independent growth, and gelatin zymography were assessed, after or without treatment with the MEK inhibitor, PD98059. RESULTS: ERK1/2 phosphorylation was found to be increased in PDVC57 when compared to PDV. This also applies to A5 spindle carcinoma cells when compared to squamous carcinoma and papilloma cells. The above finding was reproduced when transfecting human activated Ha-ras allele into PDV, thus demonstrating that Ha-ras enhances ERK1/2 signaling. To further test whether ERK1/2 activation was required for growth we used the MEK-1 inhibitor, PD98059. The latter inhibited cell proliferation and anchorage-independent growth of squamous and spindle cells. In addition, PD98059 treatment partially reverted the spindle morphology of A5 cells. CONCLUSIONS: These data suggest, for the first time, that oncogenicity and the degree of progression in the mouse skin carcinogenesis model correlates with ERK1/2 signaling.

Animals↗
PubMedDate not supplied

Molecular mechanisms of transcriptional regulation by nuclear receptors. Perspectives for therapeutic implications.

Nuclear receptors are ligand-regulated transcription factors that evolved from an ancestral orphan receptor into a highly diverse family present throughout the entire animal kingdom. They encompass receptors for steroid and non-steroid hormones, vitamins and metabolic intermediates. These receptors signal through endocrine, paracrine, autocrine and intracrine networks to regulate multiple aspects of animal physiology, including homeostasis, development and reproduction. They exert genomic effects via direct binding as monomers, homo- or heterodimers on cognate DNA elements (hormone response elements). They also participate in signal transduction cross-talk to indirectly modulate other gene expression programmes. By coordinating expression of genetic programmes, nuclear receptors contribute to cell fate-determining processes, thereby shaping and sustaining the organism. All these actions result from one fundamental interaction: receptor binding of a cognate ligand, which induces a major allosteric change in the ligand-binding domain. This conformational alteration is transformed into cascades of protein-protein recognitions, culminating in the establishment of coregulator/cointegrator complexes on gene promoters. Coregulators induce chromatin remodelling and acetylation, thus enabling the targeted recruitment and activation of the basal transcription machinery. This review discusses the molecular infrastructure of nuclear receptor signalling. Emphasis is given to determinants of signalling specificity, especially since they highlight prominent targets for novel drug discovery.

Journal Article↗
PubMedDate not supplied

The role of Hemochromatosis C282Y and H63D mutations in the development of type 2 diabetes mellitus in Greece.

Several authors have suggested a positive association between diabetes type 2 (DM2) and the C282Y and H63D mutations of the hereditary hemochromatosis gene but others have disputed it. There are also papers reporting an increased iron load in diabetes type 2 and a possible association with the pathogenesis of the disease. We therefore performed a study in 100 type 2 diabetics and 100 age and sex matched controls to assess the possibility that C282Y and H63D mutations constitute a risk factor for DM2 in Greece. We also evaluated the iron load in 500 diabetes type 2 patients and 423 age and sex matched controls. We did not find any differences in the allele frequencies of the above mutations between patients with diabetes type 2 and controls. The allele frequencies were estimated to be 0.0075 for the C282Y and 0.115 for the H63D mutation. Subjects with even one mutation (C282Y or H63D) had higher transferrin saturation compared to those with no such mutations. This seems to apply to both diabetics (49+/- 8,6 vs 44,5+/- 5,4, p<0,01) and controls (49,3+/- 7,3 vs 42,6+/- 3,3 p<0,01). Patients with DM2 had higher transferrin saturation compared to the general population. These differences were found among men (n=250, mean+/- SD 31,8+11 vs n=73, mean+/- SD 29,5+8, p=0,05) as well as among women (n=250, mean+/- SD 28.5+10 vs n=350, mean+/- SD 25.5+9.6, p=0.001). The DM2 patients had higher ferritin levels compared to controls. In conclusion, DM2 patients have increased iron load. The C282Y and H63D mutations contribute to increased iron load in both DM2 and controls. There was no difference in the frequency of C282Y and H63D alleles between DM2 and controls in the Hellenic population.

Journal Article↗
PubMedDate not supplied

A somatic mutation in the thyrotropin receptor gene in a patient with an autonomous nodule within a multinodular goiter.

Thyrotropin (TSH) is the prime regulator of thyroid cell growth and function and acts through the thyrotropin receptor (TSHR) located on the surface membrane of thyrocytes. Somatic heterozygous mutations that cause TSHR activation in the absence of TSH have been found in toxic adenomas and in hot nodules of multinodular goiters. Clinically and histologically heterogeneous nodules can share common gain-of-function mutations. Mutation prevalence varies greatly and is inversely related to iodine intake of the population. We report a Greek patient presenting with subclinical hyperthyroidism due to a fast-growing autonomous hyperplastic nodule in a long-standing multinodular goiter. Direct DNA sequencing showed that the hot nodule harbored a somatic heterozygous activating TSHR mutation: substitution of glutamine for leucine in the third transmembrane helix. This mutation (L512Q) was recently described in two solitary toxic adenomas. This report expands the spectrum of mutations shared by dissimilar hot nodules, supporting a common mechanism for nonautoimmune thyroid autonomy. The identification of the L512Q substitution demonstrates that gain-of-function TSHR mutations are encountered in Greece, although iodine deficiency has been significantly corrected over the last three decades.

Journal Article↗