Biomedical subjects

George N Tzanakakis

Publications and source records attributed to George N Tzanakakis.

11 recordsLinked to original sources

PubMed2006

Design and synthesis of new pyranoxanthenones bearing a nitro group or an aminosubstituted side chain on the pyran ring. Evaluation of their growth inhibitory activity in breast cancer cells.

Some new 2,6-disubstituted pyrano- and 1,2-dihydropyrano[2,3-c]xanthen-7-ones have been synthesized and their antiproliferative activity has been evaluated against MDA-MB-231 breast cancer cells. The antiproliferative activity evaluation of the compounds provided evidence that a dimethylamino substituted side chain and the presence of 1,2 double bond play a key role in cell growth inhibition. Among the tested derivatives the 6-dimethylaminoethylamino-2-nitropyranoxanthenone analogue possessed a significant inhibitory effect in a wide range of concentrations.

Antineoplastic Agents↗

PubMed2005

Water-soluble amphotericin B-polyvinylpyrrolidone complexes with maintained antifungal activity against Candida spp. and Aspergillus spp. and reduced haemolytic and cytotoxic effects.

OBJECTIVES: Poor solubility and toxicity severely hinder the clinical use of amphotericin B (AmB), in spite of its attractive chemotherapeutic properties. Water-soluble complexes of AmB and polyvinylpyrrolidone (AmB-PVP) could display lower cytotoxicity while maintaining antifungal activity. METHODS: AmB-PVP [with PVP of 10, 24 and 40 kDa (AC1, AC2 and AC4)] were compared with free AmB for (i) activity against Candida spp. (five albicans; nine non-albicans) and Aspergillus spp. (four strains), (ii) haemolysis of sheep red blood cells, and (iii) release of lactate dehydrogenase from J774 macrophages [with further comparison with free PVP and a liposomal formulation of amphotericin (AmBisome)]. RESULTS: MICs and MFCs of AC1, AC2 and AC4 against Candida spp. and of AC2 and AC4 against Aspergillus spp. were similar to those of AmB (and even lower for some Candida strains). Killing kinetics (24 h) were also similar. Haemolytic activity of AC2 and AC4 was 2-fold lower than that of free AmB. Cytotoxicity of AC2 towards J774 macrophages was 8-fold lower, and that of AC4 5-fold lower than that of AmB and not significantly different from that of AmBisome. The lower cytotoxicity of AC2, AC4 was correlated with a lower cellular accumulation of amphotericin. Spectroscopic analysis shows that the lower toxicity of AmB-PVP was not owing to significant change in the monomeric/polymeric forms ratio of the drug. CONCLUSIONS: AmB-PVP complexes compared favourably with AmB for antifungal activity, were less haemolytic and cytotoxic than AmB, and show a similar cytotoxicity profile to AmBisome.

Amphotericin B↗

PubMed2005

Lead toxicity update. A brief review.

Lead is a metal which has been associated with human activities for the last 6000 years. In ancient civilizations, uses of lead included the manufacture of kitchen utensils, trays, and other decorative articles. However, lead is also toxic to humans, with the most deleterious effects on the hemopoietic, nervous, reproductive systems and the urinary tract. The main sources of lead exposure are paints, water, food, dust, soil, kitchen utensils, and leaded gasoline. The majority of cases of lead poisoning are due to oral ingestion and absorption through the gut. Lead poisoning in adults occurs more frequently during exposure in the workplace and primarily involves the central nervous system. Symptoms of hemopoietic system involvement include microcytic, hypochromic anemia with basophilic stippling of the erythrocytes. Hyperactivity, anorexia, decreased play activity, low intelligence quotient, and poor school performance have been observed in children with high lead levels. Lead crosses the placenta during pregnancy and has been associated with intrauterine death, prematurity, and low birth weight. In 1991, the Centers for Disease Control and Prevention in the USA redefined elevated blood lead levels as those > or = 10 microg/dl and recommended a new set of guidelines for the treatment of lead levels > or =15 microg/dl.

Adult↗

PubMed2003

Letrozole as a potent inhibitor of cell proliferation and expression of metalloproteinases (MMP-2 and MMP-9) by human epithelial breast cancer cells.

P450 aromatase catalyzes the conversion of androgens to estrogens and plays a key role in the cell growth of hormone-dependent breast cancer in postmenopausal women. On the other hand, matrix metalloproteinases (MMPs), which can degrade almost all components of the extracellular matrix, play a crucial role in tumor cell invasion and cancer metastasis. In the present study the effect of letrozole on cell proliferation of estrogen receptor (ER)-positive MCF-7 human epithelial breast cancer and MCF-12A human mammary epithelial cells was studied. The effect of letrozole on the in vitro release of MMPs, particularly type IV collagenases (MMP-2 and MMP-9), by the ER-positive MCF-7 cells was also investigated, using a solid-phase method of high sensitivity and accuracy. Using RNA isolates from cell lines MCF-7 and MCF-12A, reverse transcriptase-polymerase chain reaction analysis revealed that only MCF-7 cells express the P450 aromatase gene. Study of the effects of letrozole alone and the hormones 17-beta-estradiol, testosterone and 4-androstene-3, 17-dione in the presence and absence of letrozole on cell growth at the DNA synthesis level showed that letrozole significantly suppressed the endogenous aromatase-induced proliferation of MCF-7 cells. The majority of MMPs secreted by MCF-7 cells were identified in their pro-forms, which was in accordance with the low metastatic potential determined for these cells. After treatment of cells with letrozole (10 nM) for 24 and 48 h, significant inhibition of MMP levels was obtained. Furthermore, concurrent treatment of MCF-7 cells with 17-beta-estradiol in the presence of letrozole significantly suppressed the estradiol-induced stimulation of MMP levels. The data obtained suggest that letrozole is a potent in vitro inhibitor of cell proliferation and of type IV collagenases expressed by ER-positive MCF-7 cells and may be of value for suppressing breast tumor growth and invasiveness.

Breast Neoplasms↗

PubMed2003

The metastatic potential of human pancreatic cell lines in the liver of nude mice correlates well with cathepsin B activity.

BACKGROUND: Cathepsin B, a lysosomal cysteine protease, has a major role in the mechanisms of tumor metastasis. The aim of the present work was to examine the correlation between cathepsin B activity and the metastatic potential of human pancreatic cancer. METHODS: The primary cell line COLO 357 and the derivative tumor cell lines FG, L3.1, L3.2, L3.3, L3.4, and L3.5, which are characterized by progressively increasing metastatic potential, were injected intrasplenically in the athymic mice. Cathepsin B activity, metastasis, and ultrastructural characteristics were assessed. RESULTS: An increased number of liver tumor nodules was observed with each subsequent intrasplenic inoculation (p = 0.001), associated with lymph node, splenic, and pancreatic involvement. Cathepsin B activity progressively increased (p = 0.001) and was strongly positively correlated with the metastatic potential. However, no correlation was found between the metastatic potential and ultrastructural characteristics. CONCLUSIONS: These findings further support the central role of cathepsin B in metastasis in a combined in vitro/in vivo model.

Animals↗

PubMed2002

Light scattering and in vitro biocompatibility studies of poly (vinyl pyrrolidone) derivatives with amino-acid-dependent groups.

Two poly (vinyl pyrrolidone) (PVP) families with amino-acid residues (glycine, beta-alanine, gamma-aminobutiric acid and epsilon-aminocaproic acid) on the base of the co-polymer N-vinyl pyrrolidone and allyl-glycidyl ether (VP-AGE) and on the base of epoxidized PVP (EPVP) were synthesized. Static and dynamic light scattering measurements of these PVP derivatives in water showed that their structure/ behavior were similar to that of PVP. The bioreactivity was also similar to that of PVP. Further investigation of the immunoreactive properties of the derivatives in in vitro proliferation assays with fresh normal human peripheral blood lymphocytes and monocytes led to the determination of a costimulatory profile for each derivative in terms of polyclonal stimulation, specific antigen presentation, and immunoglobulin secretion. This profile allows the selection of an appropriate derivative as a carrier that would suit the immunoreactivity needs of the immobilized ligand.

Antigen Presentation↗

PubMed2002

The preventive effect of ketoconazole on experimental metastasis from a human pancreatic carcinoma may be related to its effect on prostaglandin synthesis.

BACKGROUND: Arachidonic acid metabolites known to affect platelet function also interfere with tumor growth and metastases. The purpose of this study was to evaluate the anti-metastatic potential of ketoconazole, a thromboxane synthetase and 5-lipoxygenase inhibitor, on hepatic metastasis from a human pancreatic adenocarcinoma in nude mice and its effect on serum prostaglandin levels. METHODS: The human pancreatic tumor cells (RWP-2) were injected intrasplenically in nude mice grouped into control, ketoconazole (270 microg), ketoconazole (360 microg), and ketoconazole (540 microg). The agent was administered intraperitoneally 30 min before and every 24 h after the tumor cell inoculation for 8 days. In a separate experiment thromboxane B2 (TxB2), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2) and 6-Keto-F1a (stable prostacyclin derivative) were measured on blood from controls, tumor bearing animals and animals bearing tumors treated with 270 microg of ketoconazole. RESULTS: Statistically significant differences were observed between the control and three-treatment groups on the reduction of liver tumor nodules (p < 0.001), and in the liver surface areas occupied by tumor (p < 0.001). The TxB2 levels decreased from 150.6 ng/mL in the tumor bearing to 104.8 ng/mL in the ketoconazole treated animals (p < 0.05). PGD2, PGE2 and 6-keto-F1a levels increased to 7.1 ng/mL, 8.3 ng/mL, and 13.6 ng/mL from 3 ng/mL, 5.8 ng/mL, and 0.02 ng/mL respectively (p < 0.001). CONCLUSIONS: These results indicate that ketoconazole significantly reduced hepatic metastases from the human pancreatic carcinoma RWP-2 in the nude mouse model, and inhibited thromboxane B2 formation, potentiating a concomitant redirection of platelet endoperoxide metabolism into PGD2, PGE2, and 6-keto-F1a. It is hypothesized that the changes in the arachidonic acid metabolism mediate the ameliorating effect of ketoconazole on experimental hepatic metastasis.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

IGF-I affects glycosaminoglycan/proteoglycan synthesis in breast cancer cells through tyrosine kinase-dependent and -independent pathways.

The insulin-like growth factor I (IGF-I) has been implicated in breast cancer development acting through insulin-like growth factor I receptor (IGF-IR), but also through estrogen receptor (ER). The effect of IGF on proteoglycan (PG) synthesis by two human breast cancer epithelial cell lines, the ER-positive MCF-7 and the ER-negative BT-20, was studied alone and in combination with genistein. Both cell lines synthesise hyaluronan (HA), matrix secreted and cell membrane-associated galactosaminoglycan containing proteoglycans (GalAGPGs) and heparan sulphate proteoglycans (HSPGs) in variable amounts. IGF-I affects the synthesis of PGs by BT-20 cells by decreasing the amounts of HA and secreted GalAGPGs and HSPGs and upregulates the expression of cell membrane-associated GalAGPGs and HSPGs. IGF-I exerts this effect on BT-20 cells acting mainly through receptors with protein tyrosine kinase activity (PTK). In contrast, IGF-I stimulates the synthesis of secreted GalAGPGs and HSPGs by MCF-7 cells, exhibiting only a slight suppression on synthesis of cell-associated GalAGPGs and HSPGs. The regulatory effect of IGF-I on PGs distribution in MCF-7 cells is mediated through a mix of pathways, which involves both receptors with PTK activity and PTK-independent signalling. It is suggested that the effects of IGF-I on the synthesis and distribution of PGs by epithelial breast cancer cells also depend on the presence or the absence of ER. The result of the IGF-I action is the balanced biosynthesis between the matrix and cell-associated PGs in both cell lines, approaching a common biosynthetic phenotype.

Antineoplastic Agents↗

PubMedDate not supplied

In vitro effects of genistein on the synthesis and distribution of glycosaminoglycans/proteoglycans by estrogen receptor-positive and -negative human breast cancer epithelial cells.

Genistein, a soy isoflavone, affects the proliferation of both estrogen receptor (ER)-positive and ER-negative cancer cells. Glycosaminoglycans (GAGs)/proteoglycans (PGs) are considered to be of great importance in the treatment of cancer. The synthesis of GAGs by two human breast cancer epithelial cell lines, the ER-positive MCF-7 and the ER-negative BT-20, was studied under the effects of genistein, and their distribution in the culture medium and the cell membranes was determined. The results obtained show that both cell lines synthesize extracellular hyaluronic acid (HA) and both extracellular and cell-associated galactosaminoglycans (GalAGs) and heparan sulphate (HS). The MCF-7 cell line synthesizes HA, GalAGs and HS at considerably lower rates than the BT-20 cell line. The effect of genistein on the synthesis of extracellularly secreted GAGs/PGs by ER-positive MCF-7 cells is dose-dependent and follows two mechanisms; one at low concentrations (< or = 35 microM) mediated via the estrogen receptor and the other at higher concentrations via protein tyrosine kinase (PTK). The synthesis of cell-associated GAGs/PGs by ER-positive MCF-7 cells and of both secreted and associated with the cell membrane GAGs/PGs by ER-negative BT-20 cells is mediated by a PTK mechanism. It is concluded that genistein affects the synthesis of GAGs/PGs, by breast cancer epithelial cells depending on the presence or absence of estrogen receptor and the localisation of PGs.

Adenocarcinoma↗

PubMedDate not supplied

Synthesis and expression of mRNA encoding for different versican splice variants is related to the aggregation of human epithelial mesothelioma cells.

Malignant mesothelioma often has a biphasic growth pattern of epithelial and/or sarcomatous morphology. In culture, epithelial cells form aggregates, whereas fibroblast-like cells do not. Two human mesothelioma cell sub-lines, one with epithelial differentiation and the other with fibroblast-like phenotype were studied. We have previously shown (Dobra et al, 2000) that distinct types of the cell-associated syndecans are involved in the regulation of mesothelioma cell differentiation, whereas the role of matrix proteoglycans (PGs) remains unknown. This study was undertaken to examine whether cell aggregation of the epithelial mesothelioma cells correlates to the differential expression of the matrix PGs versican and perlecan at different degrees of confluence. PGs were isolated from the culture medium using ion-exchange chromatography and identified by high-performance liquid chromatography, capillary electrophoresis and Western blotting. Fibroblast-like cells express substantially more versican than epithelial cells. RT-PCR showed that both cell lines express mRNA coding for versican splice variants V0 and V1, but not for V2. The dominating splice variant in both cell lines is the V0. Screening of versican splice variants in various degrees of culture confluence showed that the expression of mRNA conding for the versican splice variants V0 and V1 is different only in confluent cultures. No significant differences in the expression of perlecan between the two cell lines were recorded. These results suggest that the aggregation of epithelial cells is related to a significant decrease (p < or = 0.001) of the splice variant V1. This variant seems to be a biologically active constituent that affects tumor biology.

Alternative Splicing↗

PubMedDate not supplied

The effects of genistein on the synthesis and distribution of glycosaminoglycans/proteoglycans by two osteosarcoma cell lines depends on tyrosine kinase and the estrogen receptor density.

The soy isoflavone genistein is a phytochemical which can affect the proliferation of both normal and cancer cells. The specific inhibition of protein tyrosine kinase (PTK) by which it effects the proliferation of cancer cells is a well-known mechanism of its action. Glycosaminoglycans (GAGs)/proteoglycans (PGs) are considered to be of great importance in the development and progression of cancer. The synthesis of GAGs by two osteosarcoma cell lines, MG-63 and SAOS-2, which differ in the density of estrogen receptors (ER) they express, and the effects of genistein on their synthesis and distribution among culture medium and cell membrane were studied. The obtained results showed that both cell lines synthesized extracellular hyaluronan (HA) and both extracellular and cell-associated galactosaminoglycans (GalAGs) and heparan sulfate (HS). Even though both cell lines synthesized considerable amounts of PGs, the SAOS-2 cells produced HA, GalAGs and HS at considerably lower rates than the MG-63 cells. The inhibitory effect of genistein on the synthesis of both extracellularly secreted and cell-associated GAGs/PGs in SAOS-2 2 cells was found to be dose-dependent and mediated most probably by a PTK mechanism. The synthesis of GAGs/PGs by the MG-63 cells in the presence of genistein was dependent on their type and localization, suggesting that a more complex mechanism regulates the PG synthesis. This may well involve the effect of genistein via the estrogen receptors, which are present in much higher density in MG-63 cells as compared to SAOS-2 cells.

Bone Neoplasms↗