María Teresa Poblete

Differential subcellular distribution of glucose transporters GLUT1–6 and GLUT9 in human cancer: Ultrastructural localization of GLUT1 and GLUT5 in breast tumor tissues

It has been proposed that the enhanced metabolic activity of tumor cells is accompanied by an increased expression of facilitative hexose transporters (GLUTs). However, a previous immunohistochemical analysis of GLUT1 expression in 154 malignant human neoplasms failed to detect the GLUT1 isoform in 87 tumors. We used 146 normal human tissues and 215 tumor samples to reassess GLUT1 expression. A similar number of samples were used to compare the expression of GLUT2–6 and 9. The classical expression of GLUT1–5 in different normal human tissues was confirmed, however, we were unable to detect GLUT2 in human pancreatic islet cells. GLUT6 was principally detected in testis germinal cells and GLUT9 was localized in kidney, liver, heart, and adrenal. In tumor samples, GLUT1, 2, and 5 were the main transporters detected. GLUT1 was the most widely expressed transporter, however, 42% of the samples had very low‐to‐negative expression levels. GLUT2 was detected in 31% of the samples, being mainly expressed in breast, colon, and liver carcinoma. GLUT5 was detected in 27% of breast and colon adenocarcinoma, liver carcinoma, lymphomas, and testis seminoma samples. In situ RT‐PCR and ultrastructural immunohistochemistry confirmed GLUT5 expression in breast cancer. GLUT6 and 9 are not clearly over‐expressed in human cancer. The extensive expression of GLUT2 and 5 (glucose/fructose and fructose transporters, respectively) in malignant human tissues indicates that fructose may be a good energy substrate in tumor cells. Our functional data obtained in vitro in different tumor cells support this hypothesis. Additionally, these results suggest that fructose uptake could be used for positron emission tomography imaging and, may possibly represent a novel target for the development of therapeutic agents in different human cancers. J. Cell. Physiol.

Stimulation of the bradykinin B1 receptor induces the proliferation of estrogen-sensitive breast cancer cells and activates the ERK1/2 signaling pathway

Kinin peptides exert multiple biological effects by binding to two types of G protein-coupled receptors known as B1 (B1R) and B2 receptors. Expression of the B1R in human breast cancer was recently reported, but up to now the consequences of its stimulation are unknown. Our aims were (1) to investigate the capacity of B1R to trigger cell proliferation in breast cancer cells, (2) to explore some of the downstream events occurring after B1R stimulation that may be linked to cell proliferation, and (3) to determine whether human breast tumors express potentially active B1R assessed by the binding of a radiolabeled agonist. Breast cancer cells expressed both the mRNA and the immunoreactive protein of B1R that once stimulated triggered cell proliferation at nanomolar concentrations of the ligand. Inhibitor studies suggested that the proliferative effects depend on the activity of epidermal growth factor receptor and subsequent ERK1/2 mitogen-activated protein kinases phosphorylation. B1R binding sites, were detected in 3/4 fibroadenomas, in 4/4 ductal carcinomas in situ and in 11/13 invasive ductal carcinomas. The B1R-epidermal growth factor receptor crosstalk may be a key interaction that maintains tumor growth, and antagonism of B1R may be a valuable alternative for the treatment of breast cancer.

Activation of kinin B1 receptor increases the release of metalloproteases-2 and -9 from both estrogen-sensitive and -insensitive breast cancer cells.

The kinin B(1) receptor (B(1)R) agonist Lys-des[Arg(9)]-bradykinin (LDBK) increases proliferation of estrogen-sensitive breast cancer cells by a process involving activation of the epidermal growth factor receptor (EGFR) and downstream signaling via the ERK1/2 mitogen-activated protein kinase pathway. Here, we investigated whether B(1)R stimulation induced release of the extracellular matrix metalloproteases MMP-2 and MMP-9 via ERK-dependent pathway in both estrogen-sensitive MCF-7 and -insensitive MDA-MB-231 breast cancer cells. Cells were stimulated with 1-100nM of the B(1)R agonist for variable time-points. Western blotting and gelatin zymography were used to evaluate the presence of MMP-2 and MMP-9 in the extracellular medium. Stimulation of B(1)R with as little as 1 nM LDBK induced the accumulation of these metalloproteases in the medium within 5-30min of stimulation. In parallel, immunocytochemistry revealed that metalloprotease levels in the breast cancer cells declined after stimulation. This effect was blocked either by pre-treating the cells with a B(1)R antagonist or by transfecting with B(1)R-specific siRNA. Activation of the ERK1/2 pathway and EGFR transactivation was required for release of metalloproteases because both the MEK1 inhibitor, PD98059, and AG1478, an inhibitor of the EGFR-tyrosine kinase activity, blocked this event. The importance of EGFR-dependent signaling was additionally confirmed since transfection of cells with the dominant negative EGFR mutant HERCD533 blocked the release of metalloproteases. Thus, activation of B(1)R is likely to enhance breast cancer cells invasiveness by releasing enzymes that degrade the extracellular matrix and thereby favor metastasis.

Cortesía verbal y modalidad: Los marcadores discursivos

El trabajo muestra evidencia, a nivel del contexto de entrevista clinica a mujeres pacientes, que los marcadores discursivos estan implicados en la marcacion de las estrategias de cortesia verbal y de la modalidad del discurso. Los analisis realizados se enmarcan en lateoria de la pragmatica, el analisis conversacional y las estrategias de cortesia, facilitadoras de las relaciones sociales y la expresion de los roles de los interactantes (Brown & Levinson,1987). Los resultados del analisis indican que la seleccion de uso de los marcadores discursivos depende de la tension entre poder y solidaridad en la situacion contextual, en concordancia con las estrategias de cortesia adoptadas. De este modo, la evidencia demuestra que el control de turnos y contenido de la entrevista esta relacionado con el contexto de inicio de turno dela entrevistadora en sus voces medico-empatica y educativo-empatica, en contraste con una mayor multifuncionalidad y frecuencia de uso de los marcadores en el desarrollo del turno en la funcion de la voz informativa de la paciente y en la funcion inductiva, instructiva y apelativa de la voz educativo-empatica de la profesional.

Análisis crítico del discurso en una entrevista semiformal

Basado en el principio de que el discurso oral conlleva la construccion del uso del poder, se presenta un extracto representativo de una entrevista semiformal a un hablante varon de la ciudad de Valdivia, Chile, generacion adulta mayor perteneciente al estrato alto, a modo de ejemplo aplicado de la metodologia del Analisis Critico del Discurso. Dicho extracto se analiza en los diversos niveles linguisticos (fonologico, morfofonologico, sintactico y lexicosemantico, pragmatico, interaccional, genero discursivo, topicos), extralinguisticos (estrato social, edad y sexo del entrevistado) y los procesos cognitivos de vision de mundo y de si mismo del hablante con el proposito de extrapolar el contenido subyacente del mensaje. Los resultados de este Analisis Critico del Discurso indican que la dimension cognitiva del control del poder se ejerce, entre otras variables, por el origen racial, genero, grupo etario y posicion sociocultural del entrevistado.