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Biomedical subjects

G Tortora

Publications and source records attributed to G Tortora.

At least 19 recordsLinked to original sources
PubMed2000

Resistance to taxanes is induced by c-erbB-2 overexpression in human MCF-10A mammary epithelial cells and is blocked by combined treatment with an antisense oligonucleotide targeting type I protein kinase A.

We have tested the sensitivity of human MCF-10A mammary epithelial cells and of their transformed derivatives overexpressing an activated c-Ha-ras gene (MCF-10A Ha-ras cells), the c-erbB-2 gene (MCF-10A c-erbB-2 cells) or both genes (MCF-10A HE cells) to different cytotoxic drugs. As compared with parental MCF-10A cells, the transformed cells exhibited an increased sensitivity to topoisomerase I- and topoisomerase II-inhibitors, and to platinum-derivatives with a 2- to 10-fold reduction in IC(50) values. A remarkable difference in sensitivity was observed following treatment with taxanes. While MCF-10A Ha-ras cells showed an increased sensitivity, MCF-10A c-erbB-2 and MCF-10A HE cells exhibited a relative resistance to taxol and taxotere, with an approximately 3.5- to 6.5-fold higher IC(50) as compared with MCF-10A cells suggesting that c-erbB-2 overexpression has a dominant effect compared with an activated c-Ha-ras gene. The type I cAMP-dependent protein kinase (PKAI) is overexpressed in cancer cells. Inhibition of PKAI by antisense oligonucleotides targeting its RIalpha regulatory subunit results in cancer cell growth inhibition. To evaluate the effect of blocking PKAI on MCF-10A cell sensitivity to taxanes, we treated these cells with taxol or taxotere in combination with a PKAI antisense oligonucleotide. Treatment with this agent, but not with a control scramble sequence, was able to overcome the effect of c-erbB-2 overexpression on MCF-10A cell sensitivity to taxol and taxotere, with a 20- to 40-fold shift in the IC(50) values for the 2 drugs.

Antineoplastic Agents↗
PubMed2000

Octylcyanoacrylate for the treatment of contaminated partial-thickness burns in swine: a randomized controlled experiment.

OBJECTIVE: To compare infection and reepithelialization rates of contaminated second-degree burns treated with octylcyanoacrylate (OCA), silver sulfadiazine (SSD), polyurethane (PU) film, and dry gauze (control; C) in swine. METHODS: Eighty standardized burns were created by applying an aluminum bar preheated to 80 degrees C to the backs and flanks of young pigs for 20 seconds. All burns were immediately contaminated with 0.1 mL of Staphylococcus aureus 10(5)/mL and randomly treated with OCA spray, SSD, PU, or dry gauze (C). Full-thickness biopsies were taken at 3, 7, and 14 days for blinded histopathologic evaluation using hematoxylin and eosin (H&E)-stained slides. Burns were considered infected in the presence of interstitial reticular dermal neutrophils containing bacteria (intraobserver agreement, kappa = 1.00). Quantitative wound cultures were performed on a second day-3 specimen. RESULTS: At day 3, wound infection rates were 30% (OCA), 50% (SSD), 55% (PU), and 50% (C); p = 0.40 (Kruskal-Wallis test). At day 7, infection rates were 35% (OCA), 85% (SSD), 70% (PU), and 65% (C); p = 0.01. Median bacterial counts at day 3 were 6,500 (OCA), 20,000 (SSD), 1,000,000 (PU), and 650,000 (C); p = 0.29. The proportion of completely reepithelialized wounds at day 14 were 75% (OCA), 90% (SSD), 85% (PU), and 90% (C); p = 0.50. CONCLUSIONS: Treatment of contaminated partial-thickness burns with OCA spray resulted in fewer infections at one week than with the other three treatments.

Animals↗
PubMed1999

Blood pressure-independent cardiac hypertrophy in acromegalic patients.

OBJECTIVE: Acromegaly is frequently associated with an increase in left ventricular mass, even in the absence of systemic hypertension. Pathological studies on acromegalic hearts have shown an extensive interstitial fibrosis, suggesting the existence of a specific acromegalic cardiomyopathy. The aim of this study was to assess left ventricular wall structure in acromegaly by ultrasonic tissue characterization. DESIGN AND METHODS: We studied 10 untreated acromegalic patients and 10 age-matched healthy control subjects. The echo patterns of two-dimensional long-axis end-diastolic echocardiograms were assessed by colour-scale analysis of the interventricular septum, with estimates of the mean colour scale value, the broad band (Bb) and the derived collagen volume fraction (dCVF). We also measured electrocardiographic QT interval dispersion (QTd) as a marker of dyshomogeneous ventricular repolarization. RESULTS: Seven patients had left ventricular hypertrophy according to the sex-independent criteria; of these, two had arterial hypertension. None of our patients had echocardiographic evidence of diastolic or systolic dysfunction. All patients showed significantly increased myocardial echoreflectivity (Bb = 106.4+/-12.1 versus 79.3+/-6.5; dCVF% = 2.78+/-0.53 versus 1.58+/-0.29; P < 0.0001) and QTd (66+/-13 ms versus 54+/-8 ms, P < 0.05). A significant correlation was found between dCVF and the duration of acromegaly (r = 0.80; P = 0.005). CONCLUSIONS: Left ventricular remodelling observed in acromegaly is not related to the presence of arterial hypertension; we hypothesize that the increased echoreflectivity and QTd are long-term consequences of cardiac hypertrophy and prolonged exposure to high levels of growth hormone and insulin-like growth factor-I.

Acromegaly↗
PubMed1999

Cooperative inhibitory effect of novel mixed backbone oligonucleotide targeting protein kinase A in combination with docetaxel and anti-epidermal growth factor-receptor antibody on human breast cancer cell growth.

Type I protein kinase A (PKAI) is overexpressed in the majority of human tumors and plays a relevant role in neoplastic transformation, conveying mitogenic signals of different growth factors and oncogenes. Inhibition of PKAI by antisense oligonucleotides targeting its RIalpha regulatory subunit results in cancer cell growth inhibition in vitro and in vivo. We have recently shown that a mixed backbone oligonucleotide targeting RIalpha can cooperatively inhibit human cancer cell growth when combined with selected cytotoxic drugs. In the present study, we have used HYB 165, a novel DNA/RNA hybrid mixed backbone oligonucleotide that exhibits improved pharmacokinetic and bioavailability properties in vivo and is presently undergoing Phase I trials. We have shown that HYB 165 exhibits a dose-dependent inhibitory effect on ZR-75-1 cells and a cooperative activity with docetaxel, a cytotoxic drug active in breast cancer. The antiproliferative activity is accompanied by increased apoptosis, as compared with each single agent. On the basis of our previous demonstration of a structural and functional relation between PKAI and epidermal growth factor receptor, we have performed a double blockade of these pathways using HYB 165 in combination with monoclonal antibody (MAb) C225, an anti-epidermal growth factor receptor chimeric MAb. The two compounds determined a cooperative growth inhibitory effect on ZR-75-1 cells and increased apoptosis. To study whether different biological agents and cytotoxic drugs can interact together, low doses of HYB 165, MAb C225, and docetaxel were combined causing an even greater cooperative effect toward growth inhibition. Finally, we have demonstrated that each single agent is able to induce bcl-2 phosphorylation and that the three agents, used in combination at suboptimal doses, determine a greater degree of bcl-2 phosphorylation and cause apoptosis of the majority of ZR-75-1 cells. These findings provide the basis for a novel strategy of treatment of breast cancer patients because both HYB 165 and MAb C225 are presently under clinical evaluation.

Antibodies, Monoclonal↗
PubMed1999

Antitumor activity of sequential treatment with topotecan and anti-epidermal growth factor receptor monoclonal antibody C225.

Epidermal growth factor (EGF)-related proteins such as transforming growth factor alpha (TGF-alpha) control cancer cell growth through autocrine and paracrine pathways. Overexpression of TGF-alpha and/or its receptor (EGFR) has been associated with a more aggressive disease and a poor prognosis. The blockade of EGFR activation has been proposed as a target for anticancer therapy. Monoclonal antibody (MAb) C225 is an anti-EGFR humanized chimeric mouse MAb that is presently in Phase II clinical trials in cancer patients. Previous studies have suggested the potentiation of the antitumor activity of certain cytotoxic drugs, such as cisplatin and doxorubicin, in human cancer cell lines by treatment with anti-EGFR antibodies. We have evaluated in human ovarian, breast, and colon cancer cell lines, which express functional EGFR, the antiproliferative activity of MAb C225 in combination with topotecan, a cytotoxic drug that specifically inhibits topoisomerase I and that has shown antitumor activity in these malignancies. A dose-dependent supraadditive increase of growth inhibition in vitro was observed when cancer cells were treated with topotecan and MAb C225 in a sequential schedule. In this respect, the cooperativity quotient, defined as the ratio between the actual growth inhibition obtained by treatment with topotecan followed by MAb C225 and the sum of the growth inhibition achieved by each agent, ranged from 1.2 to 3, depending on drug concentration and cancer cell line. Treatment with MAb C225 also markedly enhanced apoptotic cell death induced by topotecan. For example, in GEO colon cancer cells, 5 nM topotecan, followed by 0.5 microg/ml MAb C225, induced apoptosis in 45% cells as compared with untreated cells (6%) or to 5 nM topotecan-treated cells (22%). Treatment of mice bearing established human GEO colon cancer xenografts with topotecan or with MAb C225 determined a transient inhibition of tumor growth because GEO tumors resumed the growth rate of untreated tumors at the end of the treatment period. In contrast, an almost complete tumor regression was observed in all mice treated with the two agents in combination. This determined a prolonged life span of the mice that was significantly different as compared with controls (P < 0.001), to MAb C225-treated group (P < 0.001), or to the topotecan-treated group (P < 0.001). All mice of the topotecan plus MAb C225 group were the only animals alive 14 weeks after tumor cell injection. Furthermore, 20% of mice in this group were still alive after 19 weeks. The combined treatment with MAb C225 and topotecan was well tolerated by mice with no signs of acute or delayed toxicity. These results provide a rationale for the evaluation of the anticancer activity of the combination of topoisomerase I inhibitors and anti-EGFR blocking MAbs in clinical trials.

Animals↗
PubMed1999

Measurement of neovascularization is an independent prognosticator of survival in node-negative breast cancer patients with long-term follow-up.

We measured neovascularization, epidermal growth factor receptor, and c-erbB-2 expression in a consecutive series of 233 surgically resected axillary lymph node-negative breast cancer patients with a long-term follow-up to define the usefulness of these parameters as independent prognostic indicators of overall survival (OAS). Microvessel count (MVC), as a measure of neovascularization, was determined using a monoclonal antibody against human factor VIII-related antigen. The median MVC of 20 (range, 4-76) was used as a cutoff value for discriminating between low and high vascularized tumors. Epidermal growth factor receptor and c-erbB-2 expression were evaluated by immunohistochemistry. Tumors were considered positive if >10% of the cells showed specific membrane staining. OAS curves were estimated by the Kaplan-Meier method. The independent prognostic effect of each variable was determined with the Cox proportional hazards model. High MVC (P = 0.04), high nuclear grade (P = 0.005), and high S-phase (P = 0.02) significantly affected OAS at univariate analysis. In a Cox multivariate analysis, the characteristics with an independent prognostic effect on OAS were: MVC (relative hazard, 2.12; 95% confidence interval, 1.18-3.81; P = 0.01) and nuclear grade (relative hazard, 2.83; 95% confidence interval, 1.12-7.17; P = 0.01). These results demonstrate that quantification of neovascularization adds useful independent prognostic information on survival in node-negative breast cancer patients with long-term follow-up.

Adult↗
PubMed1998

Cooperative inhibition of renal cancer growth by anti-epidermal growth factor receptor antibody and protein kinase A antisense oligonucleotide.

BACKGROUND: The expression of epidermal growth factor receptor (EGFR) and type I cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKAI) is associated with neoplastic transformation. By use of human renal cancer cell lines (i.e., 769-P, ACHN, A498, and SW839), we investigated the antiproliferative activity and the antitumor activity of an anti-EGFR humanized chimeric mouse monoclonal antibody, MAb C225, and a novel mixed backbone 18-mer antisense oligonucleotide, HYB 190, that targets expression of the RIalpha regulatory subunit of PKAI. METHODS: The antiproliferative activity of MAb C225 and oligonucleotide HYB 190, alone or in combination, on different renal cancer cell lines was determined by monitoring cell growth in soft agar. In addition, the induction of apoptosis by treatment with the anti-EGFR antibody and/or antisense PKAI oligonucleotides was evaluated by flow cytometric analysis of fragmented DNA. The antitumor activity of MAb C225 and oligonucleotide HYB 190 was determined in athymic mice bearing established ACHN tumor xenografts. Cell proliferation and tumor growth data were evaluated for statistical significance using Student's t test; reported P values are two-sided. RESULTS: MAb C225 and oligonucleotide HYB 190 inhibited colony formation in soft agar in a dose-dependent manner for all renal cancer cell lines tested. We observed a potentiation of growth inhibition and induction of apoptosis when 769-P cells and ACHN cells were treated with both agents. Combination treatment with MAb C225 and oligonucleotide HYB 190 caused regression of ACHN tumor xenografts, whereas single-agent treatment only delayed tumor growth. CONCLUSION: The combination of anti-EGFR MAb C225 and ited cooperative antiproliferative effects and cooperative antitumor effects on EGFR and PKAI-expressing human renal cancer cell lines.

Animals↗
PubMed1998

Down-regulation of type I protein kinase A by transfection of human breast cancer cells with an epidermal growth factor receptor antisense expression vector.

MDA-468 human breast cancer cells overexpress the EGFR and exhibit a functional TGFalpha-EGFR autocrine pathway. Loss of EGFR expression following stable transfection with an antisense EGFR cDNA containing plasmid down-regulates type I cAMP-dependent protein kinase (PKAI) expression with acquisition of cell growth resistance to the PKAI inhibitor 8-Cl-cAMP. These results suggest that PKAI expression and function are controlled by a TGFalpha-EGFR autocrine pathway in human breast cancer cells overexpressing the EGFR.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1998

An improved method for coronary sinus blood flow monitoring by intravascular Doppler technique.

In order to obtain accurate measurements of coronary sinus blood flow (CSBF), a new catheter (7 French) with a radiopaque, flexible, and basket-shaped tip was developed for guiding a standard 3 Fr Doppler catheter in the coronary sinus (CS) in man. The radiopaque "basket" tip of the catheter allows the operator to stabilize the position of the Doppler transducer in the center of the CS and to accurately measure the CS internal diameter radiologically. CSBF was calculated as the product of CS cross-sectional area by mean CSBF velocity. Doppler-derived CSBF values at rest and during handgrip were compared with those obtained by the local thermodilution technique in 16 patients undergoing diagnostic coronary angiography. During handgrip, mean CSBF increased from 154+/-23 (rest) to 299+/-34 mL/min by the Doppler method and from 148+/-22 to 288+/-32 mL/min by the thermodilution technique. A good correlation (r = 0.86) between the CSBF values with the two techniques was observed. The authors conclude that the intravascular Doppler technique associated with the use of the basket guide catheter provides an accurate and simple tool for monitoring CSBF in patients.

Blood Flow Velocity↗
PubMed1998

Evaluation of epidermal growth factor-related growth factors and receptors and of neoangiogenesis in completely resected stage I-IIIA non-small-cell lung cancer: amphiregulin and microvessel count are independent prognostic indicators of survival.

We have determined the expression of transforming growth factor alpha (TGF alpha), amphiregulin (AR), CRIPTO, the epidermal growth factor receptor (EGFR), erbB-2, erbB-3, and tumor angiogenesis in a series of 195 patients with stage I-IIIA non-small cell lung cancer (NSCLC) treated with radical surgery to define their usefulness as prognostic indicators of survival. A variable degree of specific staining in cancer cells was observed for the three growth factors and for the three growth factor receptors in the majority of NSCLC patients. A statistically significant association between overexpression of TGF alpha, AR, and CRIPTO was observed. Enhanced expression of AR was significantly correlated with enhanced expression of erbB-2 and advanced T-stage. A direct association was also detected for overexpression of TGF alpha and of erbB-2 or erbB-3, respectively. Sex, tumor size, nodal status, stage, microvessel count, as a measure of neovascularization, and AR overexpression significantly correlated with overall survival at univariate analysis. In a Cox multivariate analysis, the only characteristics with an independent prognostic effect on OAS were microvessel count [relative hazard (RH), 6.61; P < 0.00001), nodal status (RH, 1.59; P = 0.0013), and AR overexpression (RH, 1.72; P = 0.02). These results suggest that evaluation of neoangiogenesis and of certain growth factors, such as AR, can be useful in addition to conventional pathological staging to select high-risk NSCLC patients who may benefit from post-surgical systemic therapies.

Adult↗
PubMed1998

Interactions between the epidermal growth factor receptor and type I protein kinase A: biological significance and therapeutic implications.

Peptide growth factors regulate normal cellular proliferation and differentiation through autocrine and paracrine pathways and are involved in cancer development and progression. Among the endogenous growth factors, the epidermal growth factor (EGF)-related proteins play an important role in the pathogenesis of human cancer. In fact, overexpression of EGF-related growth factors such as transforming growth factor alpha and amphiregulin and/or their specific receptor, the EGF receptor (EGFR), has been detected in several types of human cancers, including breast, lung, and colorectal cancers. Therefore, the blockade of EGFR activation by using anti-EGFR monoclonal antibodies (MAbs) has been proposed as a potential anticancer therapy. The cAMP-dependent protein kinase (PKA) is an intracellular enzyme with serine-threonine kinase activity that plays a key role in cell growth and differentiation. Two PKA isoforms with identical catalytic (C) subunits but different cAMP-binding regulatory (R) subunits (defined as RI in PKAI and RII in PKAII) have been identified. Predominant expression of PKAII is found in normal nonproliferating tissues and in growth-arrested cells, whereas enhanced levels of PKAI are detected steadily in tumor cells and transiently in normal cells exposed to mitogenic stimuli. Overexpression of PKAI has been correlated recently with poor prognosis in breast cancer patients. Inhibition of PKAI expression and function by specific pharmacological agents such as the selective cAMP analogue 8-chloro-cAMP (8-Cl-cAMP) induces growth inhibition in various human cancer cell lines in vitro and in vivo. We have provided experimental evidence of a functional cross-talk between ligand-induced EGFR activation and PKAI expression and function. In fact, PKAI is overexpressed and activated following transforming growth factor alpha-induced transformation in several rodent and human cell line models. Furthermore, PKAI is involved in the intracellular mitogenic signaling following ligand-induced EGFR activation. We have shown that an interaction between EGFR and PKAI occurs through direct binding of the RI subunit to the Grb2 adaptor protein. In this respect, PKAI seems to function downstream of the EGFR, and experimental evidence suggests that PKAI is acting upstream of the mitogen-activated protein kinase pathway. We have also demonstrated that the functional interaction between the EGFR and the PKAI pathways could have potential therapeutic implications. In fact, the combined interference with both EGFR and PKAI with specific pharmacological agents, such as anti-EGFR blocking MAbs and cAMP analogues, has a cooperative antiproliferative effect on human cancer cell lines in vitro and in vivo. The antitumor activity of this combination could be explored in a clinical setting because both the 8-Cl-cAMP analogue and the anti-EGFR blocking MAb C225 have entered human clinical trial evaluation. Finally, both MAb C225 and 8-Cl-cAMP are specific inhibitors of intracellular mitogenic signaling that have different mechanisms of action compared with conventional cytotoxic drugs. In this respect, a cooperative growth-inhibitory effect in combination with several chemotherapeutic agents in a large series of human cancer cell lines in vitro and in vivo has been demonstrated for anti-EGFR blocking MAbs or for 8-Cl-cAMP. Therefore, the combination of MAb C225 and 8-Cl-cAMP following chemotherapy could be investigated in cancer patients.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Synergistic inhibition of growth and induction of apoptosis by 8-chloro-cAMP and paclitaxel or cisplatin in human cancer cells.

8-Chloro-cAMP (8-Cl-cAMP) is a novel agent that is able to inhibit the growth of a wide variety of cancer cell types in vitro and in vivo and, at doses devoid of toxicity, to achieve plasma concentrations in cancer patients in a range effective for cancer cell growth inhibition. In this study, we have demonstrated that 8-Cl-cAMP, at a dose causing mild or no growth inhibition, synergistically increased the growth-inhibitory effect of paclitaxel or cisplatin in a wide series of cell lines including human breast, lung, ovary, colon, and head carcinomas and melanoma. A similar effect was also observed with another taxane, docetaxel, and with the platinum-derivative carboplatin. 8-Cl-cAMP also markedly enhanced apoptotic cell death induced by each cytotoxic drug. A cooperative antitumor effect was also observed in vivo, because treatment with paclitaxel followed by 8-Cl-cAMP markedly inhibited the growth of GEO human colon cancer xenografts as compared to paclitaxel alone without signs of toxicity. These data demonstrate that 8-Cl-cAMP synergistically increases the antiproliferative activity of taxanes and platinum-derived compounds and provide a rationale to use 8-Cl-cAMP in combination with taxanes and platinum-derived compounds.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Synergistic inhibition of human cancer cell growth by cytotoxic drugs and mixed backbone antisense oligonucleotide targeting protein kinase A.

Protein kinase A type I plays a key role in neoplastic transformation, conveying mitogenic signals of different growth factors and oncogenes. Inhibition of protein kinase A type I by antisense oligonucleotides targeting its RIalpha regulatory subunit results in cancer cell growth inhibition in vitro and in vivo. A novel mixed backbone oligonucleotide HYB 190 and its mismatched control HYB 239 were tested on soft agar growth of several human cancer cell types. HYB 190 demonstrated a dose-dependent inhibition of colony formation in all cell lines whereas the HYB 239 at the same doses caused a modest or no growth inhibition. A noninhibitory dose of each mixed backbone oligonucleotide was used in OVCAR-3 ovarian and GEO colon cancer cells to study whether any cooperative effect may occur between the antisense and a series of cytotoxic drugs acting by different mechanisms. Treatment with HYB 190 resulted in an additive growth inhibitory effect with several cytotoxic drugs when measured by soft agar colony formation. A synergistic growth inhibition, which correlated with increased apoptosis, was observed when HYB 190 was added to cancer cells treated with taxanes, platinum-based compounds, and topoisomerase II selective drugs. This synergistic effect was also observed in breast cancer cells and was obtained with other related drugs such as docetaxel and carboplatin. Combination of HYB 190 and paclitaxel resulted in an accumulation of cells in late S-G2 phases of cell cycle and marked induction of apoptosis. A cooperative effect of HYB 190 and paclitaxel was also obtained in vivo in nude mice bearing human GEO colon cancer xenografts. These results are the first report of a cooperative growth inhibitory effect obtained in a variety of human cancer cell lines by antisense mixed backbone oligonucleotide targeting protein kinase A type I-mediated mitogenic signals and specific cytotoxic drugs.

Animals↗
PubMed1997

Expression of Wnt5a is downregulated by extracellular matrix and mutated c-Ha-ras in the human mammary epithelial cell line MCF-10A.

Wnt genes are involved in tumour growth and regulate cell adhesion. Some (Wnt5a and Wnt7b) are more highly expressed in human breast cancer compared to normal tissues. Wnt5a is involved in the regulation of cell movement in Xenopus and is upregulated in several human cancers. Factors regulating Wnt gene expression in human breast epithelium are poorly understood, but c-erbB2 is amplified in many breast cancers and associated with rapid growth and metastasis, as is high expression of c-Ha-ras. To further understand the regulation of Wnt gene expression, this study investigated the effect of proto-oncogenes c-Ha-ras and c-erbB2, and collagen on Wnt mRNA expression, in a normal spontaneously immortalised human mammary epithelial cell line MCF-10A. Out of nine human Wnt genes investigated, Wnt5a and Wnt7b were expressed in the parental cell line, and neomycin-, c-Ha-ras- and c-erbB2-transfected cell lines. The level of Wnt5a mRNA expression was decreased 40-fold and 3-fold when parental cells were grown on collagen and in collagen, respectively. This downregulation correlated with cell branching. However, Wnt7b was not regulated by collagen. In the presence of activated c-Ha-ras, the level of Wnt5a mRNA expression was markedly decreased (> 200-fold) and cell growth rate was elevated. When treated with p21ras inhibitor, BZA-5B, there was a moderate reversal of Wnt5a mRNA expression (2-fold) with a parallel decrease in cell growth. The data indicate that c-Ha-ras is an upstream inhibitory regulator of Wnt5a, and provide further evidence of an inverse relationship between Wnt5a mRNA expression and cell branching. This demonstrates selectivity of regulation of individual members of the Wnt gene family by the ras pathway. Overexpression of c-erbB2 had no effect on Wnt5a or Wnt7b mRNA expression. Thus, extracellular matrix and ras regulate Wnt5a, providing a mechanism for feedback of morphogenetic movements, which is relevant also to cancer biology.

Benzodiazepines↗
PubMed1997

The RIalpha subunit of protein kinase A (PKA) binds to Grb2 and allows PKA interaction with the activated EGF-receptor.

Functional interactions between protein kinase A (PKA) and epidermal growth factor receptor (EGF-R) signalling pathways have been suggested. Unlike the type II isoform of PKA (PKAII), the type I (PKAI) and/or its regulatory subunit RIalpha are generally overexpressed in cancer cells and are induced following transforming growth factor alpha (TGF alpha)/EGF-R-dependent transformation. Downregulation of RIalpha/PKAI inhibits TGF alpha expression and EGF-R-dependent signalling. We have previously shown that addition of EGF to quiescent human normal epithelial MCF-10A cells determines PKAI expression and cell membrane translocation before cells enter S phase, while PKAI inhibition prevents S phase entry. Constitutive overexpression of PKAI confers the ability to grow in serum free medium, bypassing EGF requirement. Here we demonstrate a direct interaction of PKAI, but not of PKAII, with the activated EGF-R, that occurs within 5 min following EGF treatment of MCF-10A cells. Moreover, induction of mitogen-activated protein kinase (MAPK) activity following EGF-R activation is mimicked by PKAI overexpression and inhibited by downregulators of PKAI. Finally, the PKAI-EGF-R association occurs through the binding of RIalpha to the SH3 domain(s) of Grb2 adaptor protein, thus allowing the recruitment of the PKAI holoenzyme to the activated EGF-R. This is the first demonstration of a direct interaction of PKAI with the activated EGF-R macromolecular signalling complex.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Dose-response of X-irradiated human and equine lymphocytes.

We have investigated and compared DNA damage and cell killing induced in human and equine lymphocytes after in vitro X-irradiation. Our data show that the cytogenetic and the lethality effects are both greater in equine lymphocytes, but that the difference is wider for lethality. The ratios between doses inducing the same effect are 1.3, 1.7 and 9.4 for the number of binucleated cells with micronuclei, micronucleus frequency in binucleated cells and DNA synthesis inhibition, respectively. The very different radiosensitivity observed for the two mammalian species encourages us to use their lymphocytes in cell radiobiology studies.

Animals↗