Abstract:

Transgenic mice overexpressing growth hormone (GH) show increased hepatic protein content of the epidermal growth factor receptor (EGFR), which is broadly associated with cell proliferation and oncogenesis. However, chronically elevated levels of GH result in desensitization of STAT-mediated EGF signal and similar response of ERK1/2 and AKT signaling to EGF compared to normal mice. To ascertain the mechanisms involved in GH attenuation of EGF signaling and the consequences on cell cycle promotion, phosphorylation of signaling mediators was studied at different time points after EGF stimulation, and induction of proteins involved in cell cycle progression was assessed in normal and GH-overexpressing transgenic mice. Results from kinetic studies confirmed the absence of STAT3 and 5 activation and comparable levels of ERK1/2 phosphorylation upon EGF stimulation, which was associated with diminished or similar induction of c-MYC, c-FOS, c-JUN, CYCLIN D1 and CYCLIN E in transgenic compared to normal mice. Accordingly, kinetics of EGF-induced c-SRC and EGFR phosphorylation at activating residues demonstrated that activation of these proteins was lower in the transgenic mice with respect to normal animals. In turn, EGFR phosphorylation at serine 1046/1047, which is implicated in the negative regulation of the receptor, was increased in the liver of GH-overexpressing transgenic mice both in basal conditions and upon EGF stimulus. Increased basal phosphorylation and activation of the p38-mitogen-activated protein kinase might account for increased Ser 1046/1047 EGFR. Hyperphosphorylation of EGFR at serine residues would represent a compensatory mechanism triggered by chronically elevated levels of GH to mitigate the proliferative response induced by EGF.

Author affiliation: Gonzalez, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Miquet, Johanna Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Irene, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Diaz, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Rossi, Soledad Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Author affiliation: Sotelo, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Frungieri, Monica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Author affiliation: Hill, Cristal M.. Southern Illinois University; Estados Unidos

Author affiliation: Bartke, Andrzej. Southern Illinois University; Estados Unidos

Author affiliation: Turyn, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Abstract:

The conditions for in vitro oocyte maturation impact on cytoplasmic and nuclear processes in the oocyte. These events are differentially influenced by the nature of the maturation inducer and the presence of intact cumulus in cumulus–oocyte complexes. Epidermal growth factor is the main growth factor promoting oocyte maturation. Also, hyaluronic acid (HA) produced by cumulus cells is known to be responsible for the correct structural and functional organization of the cumulus during oocyte maturation. Therefore, we evaluated the developmental competence of bovine oocytes matured in vitro in a maturation medium supplemented with both EGF and HA, compared to FSH and fetal bovine serum (FBS). In addition, the impact of IVM conditions on the proteomic profile of metaphase II bovine oocytes was analyzed by two-dimensional electrophoresis. Cumulus–oocyte complexes were matured in two media: (1) 10 ng/mL EGF, 15 μg/mL HA, and 100-μM cysteamine and (2) 0.01 UI/mL rh-FSH and 10% FBS. The percentages of first polar body and embryo production and the kinetics of embryo development and oocyte proteomic profiles were analyzed. Oocytes matured in the presence of EGF-HA showed an increase (6%, P < 0.05) in the percentage of polar body extrusion. The blastocyst rate was 3% (P < 0.05) higher in the FSH-FBS group, but no differences were found in the rate of expanded blastocyst neither in total embryo production between IVM conditions. Cleavage rate of oocytes matured with FSH-FBS was 5% higher (P < 0.05) with respect to EGF-HA–matured oocytes when evaluated 30 hours after fertilization. However, at Day 7, those inseminated oocytes that underwent division at a correct timing showed that although there are still early blastocysts in the FSH-FBS condition, EGF-HA embryos have developed completely into blastocysts. Still, the production rate of those embryos that achieved expansion was similar between both maturation conditions. On the other hand, noncleaved presumptive zygotes at Day 7 developed into the different stages with similar rates (∼4%) independently of the medium condition. Modifications of IVM medium composition markedly affected protein profile of bovine oocytes in a differential manner. The proteomic approach revealed the presence of 68 spots in both treatments, 41 exclusively found in the FSH-FBS group and 64 exclusive for the EGF-HA group. Taken together, these results indicate that combined EGF-HA supplementation of in vitro maturation medium could be used to improve oocyte meiotic competence and ensure a better timing to develop into the blastocyst stage.

EEA Balcarce

Author affiliation: Rios, Glenda Laura. INTA. Estación Experimental Agropecuaria Balcarce. Departamento de Producción Animal. Biotecnología de la Reproducción; Argentina

Author affiliation: Buschiazzo, Jorgelina. INTA. Estación Experimental Agropecuaria Balcarce. Departamento de Producción Animal. Biotecnología de la Reproducción; Argentina. Consejo Nacional de Investigaciones Cientificas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Instituto de Investigaciones Bioquímicas Bahia Blanca; Argentina

Author affiliation: Mucci, Nicolas Crescencio. INTA. Estación Experimental Agropecuaria Balcarce. Departamento de Producción Animal. Biotecnología de la Reproducción; Argentina

Author affiliation: Kaiser, German Gustavo. INTA. Estación Experimental Agropecuaria Balcarce. Departamento de Producción Animal. Biotecnología de la Reproducción; Argentina

Author affiliation: Cesari, Andreina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; Argentina

Author affiliation: Alberio, Ricardo. INTA. Estación Experimental Agropecuaria Balcarce. Departamento de Producción Animal. Biotecnología de la Reproducción; Argentina

Abstract:

We have reported recently that the proliferation of PC12 cells exposed to micromolar concentrations of Tl(I) or Tl(III) has different outcomes, depending on the absence (EGF− cells) or the presence (EGF+ cells) of epidermal growth factor (EGF) added to the media. In the current work, we investigated whether EGF supplementation could also modulate the extent of Tl(I)- or Tl(III)-induced cell apoptosis. Tl(I) and Tl(III) (25–100 μM) decreased cell viability in EGF− but not in EGF+ cells. In EGF− cells, Tl(I) decreased mitochondrial potential, enhanced H2O2 generation, and activated mitochondrial-dependent apoptosis. In addition, Tl(III) increased nitric oxide production and caused a misbalance between the anti- and pro-apoptotic members of Bcl-2 family. Tl(I) increased ERK1/2, JNK, p38, and p53 phosphorylation in EGF− cells. In these cells, Tl(III) did not affect ERK1/2 and JNK phosphorylation but increased p53 phosphorylation that was related to the promotion of cell senescence. In addition, this cation significantly activated p38 in both EGF− and EGF+ cells. The specific inhibition of ERK1/2, JNK, p38, or p53 abolished Tl(I)-mediated EGF− cell apoptosis. Only when p38 activity was inhibited, Tl(III)-mediated apoptosis was prevented in EGF− and EGF+ cells. Together, current results indicate that EGF partially prevents the noxious effects of Tl by preventing the sustained activation of MAPKs signaling cascade that lead cells to apoptosis and point to p38 as a key mediator of Tl(III)-induced PC12 cell apoptosis.

Author affiliation: Pino, María Teresa Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Marotte, Clarisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Verstraeten, Sandra Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Abstract:

Background-Myocardial stretch increases force biphasically: the Frank-Starling mechanism followed by the slow force response (SFR). Based on pharmacological strategies, we proposed that epidermal growth factor (EGF) receptor (EGFR or ErbB1) activation is crucial for SFR development. Pharmacological inhibitors could block ErbB4, a member of the ErbB family present in the adult heart. We aimed to specifically test the role of EGFR activation after stretch, with an interference RNA incorporated into a lentiviral vector (small hairpin RNA [shRNA]-EGFR). Methods and Results-Silencing capability of p-shEGFR was assessed in EGFR-GFP transiently transfected HEK293T cells. Four weeks after lentivirus injection into the left ventricular wall of Wistar rats, shRNA-EGFR-injected hearts showed -60% reduction of EGFR protein expression compared with shRNA-SCR-injected hearts. ErbB2 and ErbB4 expression did not change. The SFR to stretch evaluated in isolated papillary muscles was ≈130% of initial rapid phase in the shRNA-SCR group, while it was blunted in shRNA-EGFR-expressing muscles. Angiotensin II (Ang II)-dependent Na+/H+ exchanger 1 activation was indirectly evaluated by intracellular pH measurements in bicarbonate-free medium, demonstrating an increase in shRNA-SCR-injected myocardium, an effect not observed in the silenced group. Ang II- or EGF-triggered reactive oxygen species production was significantly reduced in shRNA-EGFR-injected hearts compared with that in the shRNA-SCR group. Chronic lentivirus treatment affected neither the myocardial basal redox state (thiobarbituric acid reactive substances) nor NADPH oxidase activity or expression. Finally, Ang II or EGF triggered a redox-sensitive pathway, leading to p90RSK activation in shRNA-SCR-injected myocardium, an effect that was absent in the shRNA-EGFR group. Conclusions-Our results provide evidence that specific EGFR activation after myocardial stretch is a key factor in promoting the redox-sensitive kinase activation pathway, leading to SFR development.

Author affiliation: Brea, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Author affiliation: Diaz, Romina Gisel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Author affiliation: Escudero, Daiana Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Author affiliation: Caldiz, Claudia Irma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Author affiliation: Portiansky, Enrique Leo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina

Author affiliation: Morgan, Patricio Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Author affiliation: Perez, Nestor Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina

Abstract:

Previously, we studied the erythroblastic leukemia viral oncogene homolog (erbB) family of tyrosine kinase growth factor receptors in terms of protein expression, modulation and activation in the 3T3-L1 cell line. In the present study, the presence of full-length erbB mRNAs, and splice or proteolytic erbB variants, was evaluated using RT-PCR. Epidermal growth factor receptor (EGFR)/erbB1 expression was confirmed. Wild-type (wt) ErbB2, human erbB2 (HER2)-extracellular domain (ECD) and herstatin mRNA expression were analyzed. Restriction analysis confirmed wt expression. 3T3-L1 cells exhibited HER2-ECD and herstatin mRNA expression, although at extremely low levels (compared to the control cell lines). ErbB3 cDNA was amplified using mouse mammary tumors and rat acines as positive controls. ErbB4 was not positively identified in these cells. In conclusion, this study demonstrates that 3T3-L1 cells express EGFR/erbB1, erbB2 and erbB3, and possibly, certain erbB2 splice or proteolytic variants, which are worth pursuing.

Author affiliation: Pagano, Eleonora. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina. Pontificia Universidad Católica Argentina "Santa María de Los Buenos Aires"; Argentina

Author affiliation: Fontana, Vanina Andrea. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Author affiliation: Calvo, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Abstract:

During hypothermic preservation of cells (0-4°C), metab¬olism is diminished and energy-dependent transport processes are arrested. The effect of hypothermic preservation of hepatocytes in endocytic transport following rewarming has not been previously reported. We evaluated the uptake of EGF (Epidermal Growth Factor) ligand conjugated to fluorescent Quantum Dots (QDs) probes in rat hepatocytes after 24 and 72 h cold storage in University of Wisconsin (UW) solution at 4°C. QDs uptake was visualized during rewarming to 37°C under air or, in a second approach, at the end of rewarming under 5% CO2. After 24 h in UW solution, QDs were internalized under both rewarming conditions similar to non-preserved hepatocytes and cells maintained a normal cytoskeleton distribution. However, in hepatocytes preserved 72 h none of the cells internalized QDs, which remained bound to the membranes. After rewarming, this group showed diminished actin staining while viability was maintained at ~70%. Our results present evidence that, hypothermic preservation for 72 h in UW solution at 4°C does not prevent EGFR (Epidermal Growth Factor Receptor) activation but irreversibly impairs endocytic uptake upon EGF stimulation; presumably due to actin cytoskeleton disassembling. Our approach can be applied on other membrane receptor systems and with other hypothermic preservation solutions to understand the effect of cooling in endocytic transport and to determine the optimal cold storage period.

Author affiliation: Hovanyecz, P.. Universidad Nacional de Rosario. Secretaria de Ciencia y Tecnica. Centro Binacional de Investigación en Criobiologia Clinica y Aplicada; Argentina

Author affiliation: Guibert, Edgardo Elvio. Universidad Nacional de Rosario. Secretaria de Ciencia y Tecnica. Centro Binacional de Investigación en Criobiologia Clinica y Aplicada; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina

Author affiliation: Pellegrino, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Fisiología Experimental (i); Argentina

Author affiliation: Rodriguez, Joaquin Valentin. Universidad Nacional de Rosario. Secretaria de Ciencia y Tecnica. Centro Binacional de Investigación en Criobiologia Clinica y Aplicada; Argentina

Author affiliation: Sigot, Valeria. Universidad Nacional de Rosario. Secretaria de Ciencia y Tecnica. Centro Binacional de Investigación en Criobiologia Clinica y Aplicada; Argentina

Abstract:

Current GH administration protocols imply frequent s.c. injections, resulting in suboptimal compliance. Therefore, there is interest in developing delivery systems for sustained release of the hormone. However, GH has different actions depending on its continuous or pulsatile plasma concentration pattern. GH levels and circulating concentration patterns could be involved in the regulation of epidermal growth factor receptor (EGFR) expression in liver. Aberrant expression of this receptor and/or its hyperactivation has been associated with the pathogenesis of different types of carcinoma. Considering that one of the adverse effects associated with GH overexpression and chronic use of GH is the increased incidence of malignancies, the aim of this study was to analyze the effects of GH plasma concentration patterns on EGFR expression and signaling in livers of mice. For this purpose, GH was administered by s.c. daily injections to produce an intermittent plasma pattern or by osmotic pumps to provoke a continuously elevated GH concentration. Intermittent injections of GH induced upregulation of liver EGFR content, augmented the response to EGF, and the induction of proteins involved in promotion of cell proliferation in female mice. In contrast, continuous GH delivery in male mice was associated with diminished EGFR in liver and decreased EGF-induced signaling and expression of early genes. The results indicate that sustained delivery systems that allow continuous GH plasma patterns would be beneficial in terms of treatment safety with regard to the actions of GH on EGFR signaling and its promitogenic activity.

Author affiliation: Díaz, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina

Author affiliation: Miquet, Johanna Gabriela. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Rossi, Soledad Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Author affiliation: Irene, Pablo Ezequiel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Sotelo, Ana Isabel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Frungieri, Monica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Author affiliation: Turyn, Daniel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Gonzalez, Lorena. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Abstract:

Current GH administration protocols imply frequent s.c. injections, resulting in suboptimal compliance. Therefore, there is interest in developing delivery systems for sustained release of the hormone. However, GH has different actions depending on its continuous or pulsatile plasma concentration pattern. GH levels and circulating concentration patterns could be involved in the regulation of epidermal growth factor receptor (EGFR) expression in liver. Aberrant expression of this receptor and/or its hyperactivation has been associated with the pathogenesis of different types of carcinoma. Considering that one of the adverse effects associated with GH overexpression and chronic use of GH is the increased incidence of malignancies, the aim of this study was to analyze the effects of GH plasma concentration patterns on EGFR expression and signaling in livers of mice. For this purpose, GH was administered by s.c. daily injections to produce an intermittent plasma pattern or by osmotic pumps to provoke a continuously elevated GH concentration. Intermittent injections of GH induced upregulation of liver EGFR content, augmented the response to EGF, and the induction of proteins involved in promotion of cell proliferation in female mice. In contrast, continuous GH delivery in male mice was associated with diminished EGFR in liver and decreased EGF-induced signaling and expression of early genes. The results indicate that sustained delivery systems that allow continuous GH plasma patterns would be beneficial in terms of treatment safety with regard to the actions of GH on EGFR signaling and its promitogenic activity

Author affiliation: Díaz, Maria E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Author affiliation: Miquet, Johanna Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Author affiliation: Rossi, Soledad Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina

Author affiliation: Irene, Pablo E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Author affiliation: Sotelo, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Author affiliation: Frungieri, Monica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentina

Author affiliation: Turyn, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Author affiliation: Gonzalez, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisicoquímica Biológicas; Argentina

Abstract:

Epidermal growth factor (EGF) is a key regulator of cell survival and proliferation involved in the pathogenesis and progression of different types of cancer. The EGF receptor (EGFR) is activated by binding of the specific ligand but also by transactivation triggered by different growth factors including GH. Chronically, elevated GH levels have been associated with the progression of hepatocellular carcinoma. Considering EGF and GH involvement in cell proliferation and their signaling crosstalk, the objective of the present study was to analyze GH modulatory effects on EGF signaling in liver. For this purpose, GH receptor-knockout (GHR-KO) and GH-overexpressing transgenic mice were used. EGFR content was significantly decreased in GHR-KO mice. Consequently, EGF-induced phosphorylation of EGFR, AKT, ERK1/2, STAT3, and STAT5 was significantly decreased in these mice. In contrast, EGFR content as well as its basal tyrosine phosphorylation was increased in transgenic mice overexpressing GH. However, EGF stimulation caused similar levels of EGFR, AKT, and ERK1/2 phosphorylation in normal and transgenic mice, while EGF induction of STAT3 and STAT5 phosphorylation was inhibited in the transgenic mice. Desensitization of the STATs was related to decreased association of these proteins to the EGFR and increased association between STAT5 and the tyrosine phosphatase SH2-containing phosphatase-2. While GHR knockout is associated with diminished expression of the EGFR and a concomitant decrease in EGF signaling, GH overexpression results in EGFR overexpression with different effects depending on the signaling pathway analyzed: AKT and ERK1/2 pathways are induced by EGF, while STAT3 and STAT5 activation is heterologously desensitized.

Author affiliation: Gonzalez, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Author affiliation: Díaz, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Author affiliation: Miquet, Johanna Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Author affiliation: Sotelo, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Author affiliation: Fernandez, Diego Carlos. Universidad de Buenos Aires. Facultad de Medicina. Departamento de Bioquímica Humana; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Dominici, Fernando Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Author affiliation: Bartke, Andrzej. Southern Illinois University; Estados Unidos

Author affiliation: Turyn, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Fisico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Fisico-Química Biológicas; Argentina

Abstract:

The epidermal growth factor (EGF) plays a key role in physiological and pathological processes. This work reports on the influence of EGF concentration (c EGF) on the modulation of individual cell phenotype and cell colony kinetics with the aim of perturbing the colony front roughness fluctuations. For this purpose, HeLa cell colonies that remain confluent along the whole expansion process with initial quasi-radial geometry and different initial cell populations, as well as colonies with initial quasi-linear geometry and large cell population, are employed. Cell size and morphology as well as its adhesive characteristics depend on c EGF. Quasi-radial colonies (QRC) expansion kinetics in EGF-containing medium exhibits a complex behavior. Namely, at the first stages of growth, the average QRC radius evolution can be described by a t 1/2 diffusion term coupled with exponential growth kinetics up to a critical time, and afterwards a growth regime approaching constant velocity. The extension of each regime depends on c EGF and colony history. In the presence of EGF, the initial expansion of quasi-linear colonies (QLCs) also exhibits morphological changes at both the cell and the colony levels. In these cases, the cell density at the colony border region becomes smaller than in the absence of EGF and consequently, the extension of the effective rim where cell duplication and motility contribute to the colony expansion increases. QLC front displacement velocity increases with c EGF up to a maximum value in the 2-10 ng ml-1 range. Individual cell velocity is increased by EGF, and an enhancement in both the persistence and the ballistic characteristics of cell trajectories can be distinguished. For an intermediate c EGF, collective cell displacements contribute to the roughening of the colony contours. This global dynamics becomes compatible with the standard Kardar-Parisi-Zhang growth model, although a faster colony roughness saturation in EGF-containing medium than in the control medium is observed.

Author affiliation: Muzzio, Nicolás Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

Author affiliation: Carballido, Marcos. Facultad de Ciencias Exactas, Universidad Nacional de la Plata; Argentina

Author affiliation: Pasquale, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

Author affiliation: González, Pedro Horacio. CICBA. Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Cátedra de Patología; Argentina

Author affiliation: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

Author affiliation: Arvía, Alejandro Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina