Association of gastric cancer incidence with MDR1 gene polymorphism in an ethnic Iranian population.

Background: The allele frequency of the multidrug resistance 1 (MDR1) gene C3435T polymorphism differs with different ethnic populations, such as Asian, African, and Caucasian. This polymorphism has been reported to be associated with the increase of gastric cancer. Objectives: The objective of this study was to find out the association of gastric cancer incidence with MDR1 gene polymorphism in an ethnic Iranian population. Materials and Methods: In this study, 48 gastric cancer patients were diagnosed. Genomic DNA was extracted by a salting-out method. The MDR1 polymorphism was studied by a polymerase chain reaction (PCR)-restriction fragment length polymorphism method, using a standard method. Results: The polymorphic homozygote (T/T) genotype showed significantly an association with the incidence of gastric cancer compared with controls (P < 0.05). Conclusions: This study suggests that C3435T polymorphism of the MDR1 gene may be associated with gastric cancer in an ethnic Iranian population.

Lymphocyte P-glycoprotein variability in healthy individuals / Variabilidad de la glicoproteína P linfocitaria en una población sana

The aim of the present work was to describe the distribution of lymphocyte P-glycoprotein activity on a population of healthy individuals, taking also into account sex and age. P-glycoprotein activity in lymphocytes was measured by the Rhodamine 123 efflux assay using flow cytometry, in the presence and absence of verapamil, a P-glycoprotein inhibitor. We obtained a range of P-glycoprotein activity from 1.04 to 3.79. The distribution of the activity in the population studied was better described by a bimodal model, according with the Kolmogorov-Smirnov test. The frequency adjusted to the following equation: F = 0.70 N (2.11; 0.43) + 0.30 N(3.29; 0.26), in which 0.70 and 0.30 represented the proportion of each group, and 0.43 and 0.26 were the standard deviations of the activity of each group, respectively. The study of the relationship between subjects´ age and P-glycoprotein activity showed no statistical significance. When healthy volunteers were separated according to sex, similar distributions were observed, although for men an increase in proportion of higher P-glycoprotein function group was observed. The variability observed in the population studied was important, with some volunteers with very scarce activity and some with a fourfold higher activity. Characterization of P-glycoprotein functionality in the population represents a useful contribution to the beginning of pharmacological treatments that consider its effect on pharmacokinetics and pharmacodynamics of individualized patients.

El objetivo del presente trabajo fue describir la distribución de la actividad de la glicoproteína P linfocitaria en una población de individuos sanos, considerando a su vez el sexo y la edad. La funcionalidad de la glicoproteína P fue determinada mediante el ensayo de eflujo de Rodamina 123, en presencia y ausencia de verapamilo, un inhibidor competitivo de este transportador, determinando la fluorescencia intracelular remanente mediante citometría de flujo. Obtuvimos un rango de actividades de entre 1.04 y 3.79. La distribución de la actividad en la población evaluada se ajusta a un modelo bimodal, según el test de Kolmogorov-Smirnov. La frecuencia ajusta a la siguiente ecuación: F = 0.70 N (2.11; 0.43) + 0.30 N (3.29; 0.26) donde 0.70 y 0.30 representan las proporciones de cada grupo, mientras que 0.43 y 0.26 corresponden al desvío estándar de la actividad de cada grupo respectivamente. Al estudiar la correlación entre la edad de los sujetos y la función de la proteína, no se observaron diferencias significativas. Cuando los individuos fueron clasificados en función del sexo, las distribuciones obtenidas fueron semejantes, aunque para los varones se observó un aumento en la proporción de individuos con alta actividad. La variabilidad observada fue importante, comprendiendo individuos con escasa actividad y otros que presentaron una actividad hasta cuatro veces mayor. La caracterización de la función de la glicoproteína P en la población representa una contribución indispensable para el desarrollo de tratamientos farmacológicos personalizados que consideren el efecto de dicho transportador en la farmacocinética y farmacodinámica de cada paciente.

Multidrug resistance in tumour cells: characterization of the multidrug resistant cell line K562-Lucena 1

Multidrug resistance to chemotherapy is a major obstacle in the treatment of cancer patients. The best characterised mechanism responsible for multidrug resistance involves the expression of the MDR-1 gene product, P-glycoprotein. However, the resistance process is multifactorial. Studies of multidrug resistance mechanisms have relied on the analysis of cancer cell lines that have been selected and present cross-reactivity to a broad range of anticancer agents. This work characterises a multidrug resistant cell line, originally selected for resistance to the Vinca alkaloid vincristine and derived from the human erythroleukaemia cell K562. This cell line, named Lucena 1, overexpresses P-glycoprotein and have its resistance reversed by the chemosensitisers verapamil, trifluoperazine and cyclosporins A, D and G. Furthermore, we demonstrated that methylene blue was capable of partially reversing the resistance in this cell line. On the contrary, the use of 5-fluorouracil increased the resistance of Lucena 1. In addition to chemotherapics, Lucena 1 cells were resistant to ultraviolet A radiation and hydrogen peroxide and failed to mobilise intracellular calcium when thapsigargin was used. Changes in the cytoskeleton of this cell line were also observed

Molecular characterisation of pancreatic zymogen granule ion channel and regulator proteins involved in exocytosis

In pancreatic acinar cells Ca(2+)-dependent secretagogues promote the fusion of zymogen granules (ZG) with the apical plasma membrane (PM) and exocytosis of digestive enzymes. In addition to exocytotic fusion complexes between SNARE proteins in the ZG membrane (ZGM) and the apical PM, enzyme secretion elicited by Ca(2+)-dependent secretagogues requires cytosolic Cl and K+ and is inhibited by blockers of Cl- and K+-channels. We have identified a Cl-conductance activated by ATP, and a K+-conductance (with properties similar to ATP-sensitive K+-channels), regulated by the granule matrix protein Zg-16p in the ZGM. Both conductances are inversely regulated by a 65-kD mdr1 gene product. We have also identified a novel Ca(2+)-activated anion conductance in ZGM, the Ca(2+)-sensitivity of which increases 50-fold when Cl is replaced by 1. This conductance is blocked by micromolar H2-DIDS or DTT, reminiscent of a family of epithelial Ca(2+)-activated Cl -channels (CaCC). Expression of a CaCC in exocrine pancreas has been confirmed by RT-PCR analysis, and by immunoblotting and immunogold labeling of ZG membranes. These data suggest that ion channels in the ZGM are essential elements in pancreatic exocytosis.

Resistencia multidroga (MDR) o pleiotropica / Multidrug or pleiotropic resistance

La resistencia que se genera a los agentes citotóxicos, es uno de los mayores obstáculos que se presenta en el tratamiento del cáncer, existiendo diversar causas para los fracasos terapúuticos, sidneo la principal una resistencia intrínseca de la célula tumoral. Así se ha determinado la presencia de una glicoproteina, en la membrana de las células tumorales, la P-glicoproteina de 170 Kd, que las conduce a ser resistentes a las drogas citotóxicas; tal hallazgo ha permitido describir un fenótipo de células multiresistentes (multidroga resistente o MDR) también llamada resistencia pleiotrópica. La P-glicoproteina, codificada por el gen mdr1 en el humano, actúa activamente expulsando las drogas citotóxicas fuera de las células, por lo cual su responsabilidad en la resistencia clínica puede pensarse en razón de su expresión frecuentemente elevada en cánceres resistentes intrínsecos o inducidos por la quimioterapia. En esta revisián se analizan los hallazgos más recientes en esta área, sugieriendose que tanto la actividad de la "bomba" P-glicoproteina como su regulación genética, podrían, potencialmente suminsitrar nuevos enfoques y medios para la terapéutica antineoplásica.

Fagocitosis no opsónica, lectinofagocitosis de Histoplasma capsulatum / Lactinophagocytosis of Histoplasma capsulatum

Objetivo: En este artículo se revisan algunos aspectos relevantes de la fagocitosis no opsónica de microorganismos intracelulares con especial énfasis en Histoplasma capsulatum, considerando que la participación de los mecanismos no opsónicos influyen en el destino final de los microorganismos dentro de los fagocitos. Introducción: Numerosos microorganismos intracelulares invaden y sobreviven en el interior de las células fagocíticas gracias a los medios utilizados para su internalización así como a la presencia de moléculas de superficie o productos metabólicos que neutralizan o inhiben los mecanismos microbicidas propios de los fagocitos del huésped. Participación de moléculas glicosiladas, de integrinas, y de otras moléculas, en la invasión de microorganismos al macrófago: La internalización de los microorganismos a través de los receptores independientes de opsoninas de los macrófagos generalmente facilita a la invasión de éstos, ya que algunos receptores no activan el metabolismo oxidativo, de ahí que el reconocimiento, entre la célula a ser infectada y el microorganismo, mediaso por carbohidratos y estructuras tipo lectinas constituye uno de los mecanismos de invasión más exitosos. Conclusión: El conocer estas alternativas de invasión favorecería entender mejor la patogénesis de muchas enfermedades intracelulares que representan importantes problemas de salud, como la histoplasmosis, la tuberculosis y la leishmaniasis, entre otras

P-glycoprotein as an intermediate end point of drug resistance to neoadjuvant chemotherapy in locally advanced gastric cancer

The expression of p-glycoprotein (p-gp) was evaluated in pre- and post-chemotherapy states after the administration of adriamycin-based chemotherapy in 24 gastric cancer patients. Among them, group A was composed of twelve patients who relapsed after surgery plus adjuvant chemotherapy and group B was composed of another twelve patients who received neoadjuvant chemotherapy plus surgery. Pre-chemotherapy p-gp was evaluated in 18 out of 24 patients (6 patients had no pre-chemotherapy paraffin blocks) and post-chemotherapy p-gp was evaluated from all 24 patients. Pre- and post-chemotherapy p-gp was expressed in 5 of 18 patients (27.8%), and 9 of 24 patients (37.5%), respectively, with immunohistochemical stain using monoclonal antibody JSB-1. No differences of disease-free survivals were observed in Group A based on post-chemotherapy p-gp expression from relapsed lesions. In Group B, there was a higher relapse rate (p = 0.04) and a lower one-year disease-free survival rate (p = 0.04) in post-chemotherapy p-gp positive patients when adjuvant treatment was done with the same regimen as neoadjuvant chemotherapy. In all patients studied, post-chemotherapy p-gp expression correlated with a higher systemic recurrence (p = 0.04). These data suggest that p-gp can be induced by an adriamycin-based chemotherapy in gastric cancer. Thus, we suggest that the prognosis of gastric cancer may be poor if a multidrug resistance (MDR)-related regimen is used in the presence of p-gp after neoadjuvant chemotherapy with an adriamycin-based regimen, even if the initial response is good.