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Biomedical subjects

G Isola

Publications and source records attributed to G Isola.

At least 19 recordsLinked to original sources
PubMed1999

Tamoxifen induces oxidative stress and apoptosis in oestrogen receptor-negative human cancer cell lines.

Recent data have demonstrated that the anti-oestrogen tamoxifen (TAM) is able to facilitate apoptosis in cancer cells not expressing oestrogen receptor (ER). In an attempt to identify the biochemical pathway for this phenomenon, we investigated the role of TAM as an oxidative stress agent. In two ER-negative human cancer cell lines, namely T-leukaemic Jurkat and ovarian A2780 cancer cells, we have demonstrated that TAM is able to generate oxidative stress, thereby causing thiol depletion and activation of the transcriptional factor NF-kappaB. As described for other oxidative agents, TAM was able to induce either cell proliferation or apoptosis depending on the dose. When used at the lowest dose tested (0.1 microM), a slight proliferative effect of TAM was noticed in terms of cell counts and DNA synthesis rate, whereas at higher doses (10 microM) a consistent occurrence of apoptosis was detected. Importantly, the induction of apoptosis by TAM is not linked to down-regulation or functional inactivation by phosphorylation of the antiapoptotic bcl-2 protein.

Antineoplastic Agents, Hormonal↗
PubMed1999

Phosphorylation-dependent regulation of skeletogenesis in sea urchin micromere-derived cells and embryos.

Sea urchin embryo micromeres when isolated and cultured in vitro differentiate to produce spicules. Although several authors have used this model, almost nothing is known about the signaling pathways responsible for initiating skeletogenesis. In order to investigate the potential involvement of phosphorylation events in spiculogenesis, the effect of inhibitors of protein kinases and phosphatases on skeleton formation was studied. Results obtained using both cultured micromeres and embryos revealed that protein tyrosine kinase and phosphatase inhibitors blocked skeleton formation, but not serine/threonine phosphatase inhibitors. The inhibitors showed a dose-dependent effect and when removed from micromere or embryo culture, spicule formation resumed. Inhibition of tyrosine phosphatases resulted in an increase in the tyrosine phosphorylation level of two major proteins and a modest decrease in the expression of the mRNA coding for type I fibrillar collagen. These findings strongly suggest that tyrosine phosphorylation and dephosphorylation is required for micromere differentiation and for normal skeletogenesis during sea urchin embryo development.

Animals↗
PubMed1997

Synergistic antiproliferative activity of tamoxifen and docetaxel on three oestrogen receptor-negative cancer cell lines is mediated by the induction of apoptosis.

The taxanes are a promising family of anti-tumour drugs that block cell cycle replication by interfering with the microtubule network. The clinical use of these drugs involves some problems related to their low solubility and occurrence of resistance, which is mainly dependent on the multidrug-resistant (MDR) phenotype. To investigate the possible interaction between docetaxel and tamoxifen (TAM), three oestrogen receptor-negative cancer cell lines, MDR- MDA-MB 231, MDR + CEM-VBLr and MCF-7 ADRr, were used. In all three cell lines, the combination of docetaxel and TAM was more effective in terms of growth inhibition than single drug exposure. Isobolic analysis confirmed the presence of synergism in all cell lines when docetaxel was used at 0.2 microM and TAM at a dose equal to or higher than 1 microM. Flow cytometric DNA analysis performed on the three cell lines showed that TAM was able to increase the G2/M blocking activity of docetaxel. This blocking activity was followed by an increased flow cytometric DNA fragmentation suggestive of the presence of apoptosis, which was confirmed by DNA gel fragmentation and morphological analysis. While an antagonistic effect on P-glycoprotein (P-gp) activity may contribute to the synergistic effect of tamoxifen and docetaxel on CEM-VBLr and MCF-7 ADRr, other mechanisms must be involved, as the synergistic effect is also apparent with a P-gp-negative cell line.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Tamoxifen synergizes the antiproliferative effect of cisplatin in human ovarian cancer cells: enhancement of DNA platination as a possible mechanism.

We investigated the chemosensitizing activity of tamoxifen (TAM) on estrogen receptor negative ovarian cancer cell lines sensitive (A2780 WT) and resistant to cisplatin (CP) (A2780 CP3). Our results showed that the treatment of both cell lines with the association TAM + CP (concentration range 0.01-1 microN and 0.1-1 microgram/ml, respectively) results in a synergistic antiproliferative activity and a complete reversal of the acquired CP-resistant phenotype. We demonstrated that in A2780 cells the addition of TAM to CP treatment is able to significantly enhance at every tested CP dose (P < 0.001) the amount of platinum (Pt) bound to the DNA. Since Pt-DNA levels in the genome are clearly related to the growth inhibitory effect of CP (correlation value = 0.97, P < 0.001) in our experimental model, we hypothesized that TAM could act synergistically with CP and overcome the acquired CP-resistance by enhancing Pt binding to the DNA. We suggest that, from a clinical point of view, TAM may be usefully included in CP-based chemotherapy regimens for ovarian cancer patients since plasma concentrations of the drug capable of in vitro CP resistance modulation are achievable in vivo. A prospective clinical trial to verify the clinical usefulness of combined TAM + CP treatment in ovarian cancer patients refractory to prior Pt-based chemotherapy is now underway in our department.

Antineoplastic Agents↗
PubMed1996

Modulatory effect of tamoxifen and ICI 182,780 on adriamycin resistance in MCF-7 human breast-cancer cells.

In this study the ability of the new pure anti-estrogen ICI 182,780 to modulate the cytotoxic action of adriamycin (ADR) on parental and ADR-resistant MCF-7 (MCF-7 ADRr) human breast-cancer cells was investigated and compared with that of tamoxifen (TAM). TAM enhanced ADR cytotoxicity in MCF-7 ADRr cells in a dose-related manner, but this effect was slight or absent in MCF-7 WT. In contrast, ICI 182,780 was able to enhance ADR toxicity both in MCF-7 ADRr and in the parental cell line. ICI 182,780 was up to 2.5-fold more effective than TAM in reducing the IC50 of ADR in MCF-7 ADRr cells. Analysis of the data by the isobole method showed that the combination ADR/TAM and ADR/ICI 182,780 produced synergistic anti-proliferative activity in MCF-7 ADRr cells. Because ADR resistance in these cells is associated with the expression of high levels of P-glycoprotein (Pgp), we evaluated the effect of anti-estrogens on Pgp expression and activity. Both ICI 182,780 and TAM failed to modulate Pgp expression as assessed by flow cytometry and Western-blot analysis, performed using the monoclonal antibodies MM4.17 and C 219, which are specific for an external or an internal determinant respectively. Pgp activity was investigated by flow cytometry measuring the extrusion of ADR and the cationic dye Rhodamine 123 (Rh 123). ICI 182,780, but not TAM, reduced the activity of Pgp in MCF-7 ADRr cells. Flow cytometry was also used to investigate cell-cycle modifications induced by ADR in MCF-7 ADRr cells, both in the presence and in the absence of anti-estrogens. After 72 hr, higher doses induced an arrest of cells at the G2/M phase. The same effect was visible when lower doses of ADR were combined with ICI 182,780 or TAM. In terms of cell-cycle-blocking activity ICI 182,780 was largely more effective than TAM.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Methyl-p-hydroxyphenyllactate-esterase activity and type-II estrogen-binding sites in ovarian cancer: correlation with biological and clinico-pathological parameters.

We examined the levels of activity of methyl-p-hydroxyphenyllactate esterase (MeHPLA-ase) and cytosolic Type-II-estrogen-binding sites (Type-II EBS) in 61 and 71 cases, respectively, of primary ovarian cancer. MeHPLA-ase activity and Type-II EBS were seen to by asymmetrically distributed, in that levels were skewed towards the lower values. A statistically significant direct correlation was found between MeHPLA-ase activity and Type-II EBS. MeHPLA-ase activity and Type-II EBS were inversely correlated with ER and PR levels and showed a trend towards inverse correlation with the percentage of cells in S-phase of the cell cycle. MeHPLA-ase activity and Type-II EBS did not correlate with clinico-pathological parameters. The median MeHPLA-ase activity tended to be higher in responders than in unresponsive patients, but statistical significance was not reached. Higher Type-II-EBS levels were found in cases showing complete and partial response to chemotherapy than in cases which did not respond. A statistically significant relationship was found between high MeHPLA-ase activity and longer overall survival.

Carboxylic Ester Hydrolases↗
PubMed1995

Interaction of tamoxifen with cytosolic and nuclear type II estrogen binding sites (type II EBS).

The aim of this study was to investigate the interaction of tamoxifen (TAM) with the so-called Type II estrogen binding sites (Type II EBS) in both the cytosolic and the nuclear fraction of the ER-negative A 2780 human ovarian cancer cell line and in an ER-negative ovarian cancer tissue. Although cytosolic and nuclear Type II EBS in A 2780 cells showed substantially similar binding characteristics in terms of ligand affinity and specificity, TAM, while exhibiting the ability to displace [3H]estradiol from cytosolic Type II EBS failed to interact with nuclear Type II EBS. The ability of TAM to interact only with cytosolic Type II EBS seems also to be a characteristic of ovarian cancer tissue and to be shared by several TAM metabolites. The hypothesis that the interaction of TAM with cytosolic Type II EBS could mobilize the true endogenous ligand of Type II EBS which would become available for binding to nuclear Type II EBS was tested by incubating the nuclear fraction with the cytosolic fraction. In the presence of cytosol, TAM acquires the ability to displace the tracer from nuclear Type II EBS but when the cytosolic fraction was DCC, stripped in order to remove the endogenous ligand, the competing activity of TAM for nuclear Type II EBS was abolished. Our results suggest that TAM does not interact with nuclear Type II EBS, but can favor the nuclear binding of endogenous ligand by displacing it from cytosolic Type II EBS.

Binding Sites↗
PubMed1995

Tamoxifen and quercetin interact with type II estrogen binding sites and inhibit the growth of human melanoma cells.

The mechanism of the antiproliferative activity of tamoxifen on melanoma cells in vitro and in vivo is poorly understood, as it is not mediated by the antiestrogenic properties of tamoxifen. Using a whole-cell assay and nuclear and cytosolic radio-binding experiments with [3H]-estradiol as tracer, we found that MNT1, M10, and M14 melanoma cell lines as well as primary tumors expressed type II estrogen binding sites that bind tamoxifen and the flavonoid quercetin with similar affinity (KD 10-25 nM). Cell count and clonogenic assay showed both compounds to inhibit melanoma cell growth in a concentration-dependent manner in the range of concentrations between 1 nM and 1 microM. Neither the pure antiestrogen ICI-182780 nor the 3-rhamnosylglucoside of quercetin, rutin, bound to type II estrogen binding sites or inhibited cell growth. Our results suggesting that tamoxifen and quercetin can inhibit melanoma cell growth by interacting with type II estrogen binding sites help explain the reported effectiveness of tamoxifen, particularly in estrogen-receptor-negative tumors, and stress the potential role of quercetin in the treatment of melanoma.

Binding Sites↗
PubMed1994

Quercetin enhances transforming growth factor beta 1 secretion by human ovarian cancer cells.

Our study demonstrates that quercetin (Q)-induced growth-inhibitory activity in ovarian cancer cells may be mediated by modulation of transforming growth factor beta 1 (TGF beta 1) production. We used the OVCA 433 cell line which is very sensitive to the anti-proliferative effect of Q and expresses high-affinity, low-capacity TGF beta 1 receptors. Conditioned medium (CM) from Q-treated cells is able to displace 125I-TGF beta 1 from binding to its receptor; moreover Q (10 microM) increases TGF beta 1 activity in CM in a time-dependent fashion starting after 4 hr and reaching a maximum by 24 hr of Q treatment. Q-induced growth inhibition is reversed by a neutralizing anti-TGF beta 1 MAb both in OVCA 433 and in a clonogenic assay of cells from a primary ovarian tumor. Q-induced increase of TGF beta 1 activity in CM is specific since other anti-proliferative compounds, such as Dexamethasone, which is as active on the cell cycle as Q, had no effect on TGF beta 1 secretion. Northern-blot analysis of TGF beta 1 mRNA levels at various times of Q (10 microM) exposure revealed that there was no increase, suggesting that regulation of TGF beta 1 occurs at posttranscriptional levels.

Cell Division↗
PubMed1992

Synergistic antiproliferative activity of tamoxifen and cisplatin on primary ovarian tumours.

We looked for the presence of the so-called type II oestrogen binding sites (EBS), in four oestrogen (ER) and progesterone (PR) receptor negative primary ovarian tumours. Moreover, the colony-forming assay was used to evaluate the response of ovarian cancer cells from these primary tumours to tamoxifen and cisplatin used alone or in combination. All tumours contained type II EBS, and tamoxifen was able to compete for [3H] oestradiol binding to these sites. Cisplatin and tamoxifen exhibited a dose-dependent inhibition of colony formation in a range of concentrations between 10 and 1000 micrograms/l and 37 and 3710 micrograms/l, respectively. The combination of the two drugs resulted in a synergistic antiproliferative activity, with a potentiation up to and beyond 50-fold. Our results show that in ovarian cancer tamoxifen interacts with type II EBS with an affinity consistent with the concentration effective both in inhibition of colony formation and in synergising cisplatin activity. Based on the experiments performed the action of tamoxifen on cell growth is independent of ER expression, and could be mediated by type II EBS. The possibility that the association of tamoxifen and cisplatin may result in an improved clinical response in ovarian cancer should be investigated.

Binding Sites↗
PubMed1991

Atrial natriuretic peptide in trout ovarian follicles.

An immunocytochemical study on atrial natriuretic peptide (ANP) was carried out in trout ovaries using an antiserum raised against human atrial natriuretic peptide (hANP). Weakly immunoreactive material was observed both in the ooplasm of the previtellogenic and the early vitellogenic oocytes and in the follicular cells of the late vitellogenic oocytes. Binding sites for hANP have been located using 125I-ANP and light-microscopic autoradiography. These studies provide evidence of specific binding of ANP-like material in both early and advanced vitellogenic oocytes. Autoradiograms indicated that the ANP-like binding sites were localized to a subpopulation of follicles. The presence of ANP-like immunoreactive material and its specific binding sites in the ovary suggest a role for atrial natriuretic peptide as a regulator of the fish ovarian function.

Animals↗
PubMed1990

Chemotherapy versus tamoxifen versus chemotherapy plus tamoxifen in node-positive, estrogen receptor-positive breast cancer patients: results of a multicentric Italian study. Breast Cancer Adjuvant Chemo-Hormone Therapy Cooperative Group.

Between November 1, 1983 and June 30, 1987, 510 node-positive, estrogen receptor (ER)-positive breast cancer patients have been randomly allocated to receive either chemotherapy (six intravenous [IV] cyclophosphamide, methotrexate, and fluorouracil [CMF] courses followed by four IV epirubicin courses) or 5 years of tamoxifen treatment or a combination of both therapies. After a median follow-up of 40 months, patients receiving the combined treatment achieved the best results, and those treated with chemotherapy alone achieved the worst, the difference being particularly evident in postmenopausal women. However, while the concurrent use of chemotherapy and tamoxifen did improve the results achieved by chemotherapy alone, particularly in postmenopausal women and in those with four or more involved nodes, it did not significantly improve the results achieved by tamoxifen alone, particularly in patients with higher ER tumor concentrations. Side effects were more numerous and more severe in patients receiving chemotherapy (with or without tamoxifen). Our findings, although still preliminary, confirm that tamoxifen should be the treatment of choice for postmenopausal breast cancer patients with node-positive, ER-positive tumors. In addition, the findings suggest that tamoxifen may represent a safe alternative to chemotherapy (at least to the cytotoxic regimen we used) for younger women, provided they have ER-positive tumors. In patients with ER-positive tumors, the addition of chemotherapy to tamoxifen does not seem to improve significantly the effectiveness of tamoxifen alone.

Adult↗
PubMed1985

Plasma aldosterone in newborn and adult Vipera aspis.

In the venomous viviparous snake Vipera aspis, plasma aldosterone concentration shows significant seasonal changes mainly related to temperature-dependent behavior. A difference is also present between newborns and adults. A correlation between sodium and potassium status and aldosterone plasma level in active and inactive life is suggested.

Aldosterone↗
PubMed1985

Effect of hypophysectomy on plasma electrolytes and adrenal mineralocorticoid secretion in the terrestrial chelonian Testudo hermanni.

Na, K, ACTH, corticosterone and aldosterone plasma levels were studied in Testudo hermanni after hypophysectomy and dexamethasone administration. Hypophysectomy as well as dexamethasone treatment caused a deep decrease in the plasma levels of electrolytes, corticosterone and aldosterone when compared to sham-operated or normal controls. ACTH plasma level was markedly lower in hypophysectomized or dexamethasone-treated tortoises when compared to the controls but never reached undetectable levels. Administration of ACTH significantly increased plasma electrolytes and hormone levels in hypophysectomized and dexamethasone-treated tortoises. The present data seem to indicate that the pituitary plays a significant role on electrolyte homeostasis and on the regulation of plasma mineralocorticoids level in terrestrial chelonians.

Adrenal Glands↗