Anti-proliferative effect of the gastrin-release peptide receptor antagonist RC-3095 plus temozolomide in experimental glioblastoma models.

Malignant gliomas have a dismal prognosis despite multi-modality treatments like neurosurgical resection, radiation therapy and chemotherapy. Evidence has indicated that gastrin-releasing peptide (GRP) and its receptor (GRPR) play a role in the development of a variety of cancers including gliomas. In the present study, we investigated the effects of RC-3095, a selective GRPR antagonist, alone or in combination with temozolomide (TMZ), a DNA alkylating agent, in in vitro and in vivo experimental rat C6 glioma models. Cellular proliferation was significantly reduced by all treatments with the combined administration of TMZ and RC-3095 being the most effective treatment. In in vivo experiments, the control group displayed the largest tumors (52 +/- 15.5 mm(3)), whereas RC-3095 reduced the tumor size, with the most significant effect at the dose of 0.3 mg/kg (21 +/- 9.7 mm(3)). The combined therapy produced further reduction in tumor size (10 +/- 7.5 mm(3)). Our results show that the combination of RC-3095 with TMZ produced an important reduction in in vitro and in vivo glioma growth therefore making RC-3095 a candidate drug to potentiate the effects of the DNA alkylating agent TMZ in the treatment of glioma.

Optimization of an electroporation protocol using the K562 cell line as a model: role of cell cycle phase and cytoplasmic DNAses.

The improvement of gene therapy protocols is intimately related to the establishment of efficient gene transfer methods. Electroporation has been increasingly employed in in vitro and in vivo protocols, and much attention has been given to increasing its transfection potential. The method is based on the application of an electric field of short duration and high voltage to the cells, forming reversible pores through which molecules can enter the cell. In this work, we describe the optimization of a protocol for the electroporation of K562 cells involving the combination of electric field, resistance and capacitance values. Using RPMI 1640 as pulsing buffer and 30 mug of pEGFP-N1 plasmid, 875 V cm(-1), 500 muF and infinite resistance, we achieved transfection rates of 82.41 +/- 3.03%, with 62.89 +/- 2.93% cell viability, values higher than those reported in the literature. Analyzing cell cycle after electroporation, with three different electric field conditions, we observed that in a heterogeneous population of cells, viability of G(1) cells is less affected by electroporation than that of cells in late S and G(2)/M phases. We also observed that efficiency of electroporation can be improved using the DNAse inhibitor Zn, immediately after the pulse. These results can represent a significant improvement of current methods of electroporation of animal and plant cells.