RESUMEN
In the present study, an antigastric cancer monoclonal antibody, MGb2, was chosen to prepare an antibody-daunomycin conjugate. Daunomycin was modified by cis-aconitic anhydride, and the derivative was linked to antibody, a carbodiimide reagent being used to produce peptide bonding. Four to five molecules of daunomycin were specifically bound per molecule of antibody, without severely impairing the pharmacological activity of daunomycin and with minimal loss of antibody activity. A tetrazolium dye colorimetric assay indicated that the MGb2-daunomycin conjugate exhibited selective cytotoxicity against human gastric cancer cells SGC-7901 in vitro. The tumor localization in BALB/c nude mice showed that the specific conjugate could recognize the tumor as efficiently as the unconjugated antibody. MGb2-daunomycin conjugate could significantly suppress the growth of human gastric carcinoma GAII inoculated under the renal capsules of BALB/c nude mice. Intraperitoneal injection of MGb2-daunomycin conjugate twice a week for 3 weeks at a dose of 1 mg/kg of drug gave a tumor inhibition rate of 91.58%, far more effective than free daunomycin or an irrelevant conjugate.
Asunto(s)
Anticuerpos Monoclonales/uso terapéutico , Daunorrubicina/administración & dosificación , Inmunotoxinas/uso terapéutico , Neoplasias Gástricas/tratamiento farmacológico , Animales , Anticuerpos Monoclonales/metabolismo , Anticuerpos Antineoplásicos/uso terapéutico , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Neoplasias Gástricas/inmunología , Análisis de Supervivencia , Distribución Tisular , Células Tumorales CultivadasRESUMEN
Cellular prion protein (PrP(C)), a glycosylphosphatidylinositol-anchored membrane protein, was found in our lab to be widely expressed in gastric cancer cell lines. In order to evaluate its biological significance in human gastric cancer, we investigated its expression in a large series of gastric tissue samples (n = 124) by immuno histochemical staining with the monoclonal antibody 3F4. Compared with normal tissues, gastric adenocarcinoma showed increased PrP(C) expression, correlated with the histopathological differentiation (according to the WHO and Lauren classifications) and tumor progression (as documented by pTNM staging). To better understand the underlying mechanism, we introduced the PrP(C) and two pairs of RNAi into the poorly differentiated gastric cancer cell line AGS and found that PrP(C) suppressed ROS and slowed down apoptosis in transfected cells. Further study proved that the apoptosis-related protein Bcl-2 was upregulated whereas p53 and Bax were downregulated in the PrP(C)-transfected cells. A reverse effect was observed in PrP(C) siRNA-transfected cells. These results strongly suggested that PrP(C) might play a role as an effective antiapoptotic protein through Bcl-2-dependent apoptotic pathways in gastric cancer cells. Further study into the mechanism of these relationships might enrich the knowledge of PrP, better our understanding of the nature of gastric carcinoma, and further develop possible strategies to block or reverse the development of gastric carcinoma.
Asunto(s)
Apoptosis/fisiología , Regulación Neoplásica de la Expresión Génica , Proteínas PrPC/genética , Proteínas PrPC/fisiología , Neoplasias Gástricas/fisiopatología , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Línea Celular Tumoral , Citocromos c/genética , Citocromos c/fisiología , ADN Complementario , ADN de Neoplasias/genética , Femenino , Citometría de Flujo , Humanos , Inmunohistoquímica , Masculino , Persona de Mediana Edad , Proteínas PrPC/análisis , Proteínas Proto-Oncogénicas c-bcl-2/genética , Proteínas Proto-Oncogénicas c-bcl-2/fisiología , ARN Interferente Pequeño/genética , Especies Reactivas de Oxígeno , Neoplasias Gástricas/química , Neoplasias Gástricas/genética , Neoplasias Gástricas/patología , Transfección , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/fisiología , Proteína X Asociada a bcl-2/genética , Proteína X Asociada a bcl-2/fisiologíaRESUMEN
The aim of this study was to ascertain whether MG7Ag is a useful predictor of evolution of gastric dysplasia to carcinoma. A total of 1090 patients with confirmed dysplasia were stained immunohistochemically with MG7 monoclonal antibody by the ABC method. A prospective follow-up study was undertaken on 19 patients with MG7Ag positive staining and 16 with MG7 negative staining over a period of 10-78 months. The expression of MG7Ag was also compared in another two groups by conducting retrospective studies. One group showed an evolution into gastric cancer over 2-4 years, the other did not. Quantitative analysis of MG7Ag expression was carried out on the last two groups. The receiver operating characteristic curve and Youden index were used to assess the best critical value for MG7Ag. MG7Ag was found positive in 456/1090 cases (41.8%) with dysplasia. Prospective follow-up of 35 patients showed that 6/19 patients with MG7Ag positive staining developed gastric cancer, but there were no carcinomatous changes in 16 patients with MG7 negative staining. The results of MG7Ag expression in 72 cases with retrospective follow-up showed there were 24 with positive immunostaining among 34 cancerous cases (70.6%), and only 7 in 38 non-cancerous cases (18.4%) (p<0.01). Image analysis showed that an average MG7Ag density index ++0.19 could be regarded as the critical value for high risk of gastric mucosa with dysplasia evolving to cancer. Positive MG7Ag expression in gastric mucosa of patients with dysplasia, especially in cases with a density index ++0.19, was an indicator of high risk of malignant change.