ABSTRACT
Combining gene therapy with radiotherapy and chemotherapy holds potential to increase the efficacy of cancer treatment, while minimizing side effects. We tested the responsiveness of synthetic gene promoters containing CArG elements from the Early Growth Response 1 (Egr1) gene after neutron irradiation, doxorubicin and cisplatin. Human MCF-7 breast adenocarcinoma and U373-MG glioblastoma cells were transfected with plasmids containing CArG promoters controlling the expression of the green fluorescent protein (GFP). Exposing the cells to neutrons, doxorubicin or cisplatin resulted in a significant induction of transgene expression. Therapeutic advantage was demonstrated by replacing the reporter with the herpes simplex virus thymidine kinase (HSVtk), able to convert the prodrug ganciclovir (GCV) into a cytotoxin. A 1.3 Gy neutron dose caused 49% growth inhibition in MCF-7 cells, which increased to 63% in irradiated CArG-HSVtk-transfectants treated with GCV. Exposure to 0.5 microM cisplatin or 0.01 microM doxorubicin induced a growth inhibition of 25-30% in MCF-7 cells. In the presence of GCV, this value increased to 65-70% in cells transfected with the CArG promoter constructs driving the expression of HSVtk. These data indicate that combining CArG-mediated HSVtk/GCV suicide gene therapy with radio- and chemotherapy can enhance antitumor toxicity, and validates future in vivo investigations.
Subject(s)
Antineoplastic Agents/pharmacology , Brain Neoplasms/therapy , Breast Neoplasms/therapy , DNA-Binding Proteins/genetics , Gene Expression Regulation/drug effects , Genetic Therapy/methods , Genetic Vectors , Immediate-Early Proteins/genetics , Transcription Factors/genetics , Adenocarcinoma/drug therapy , Adenocarcinoma/radiotherapy , Adenocarcinoma/therapy , Antiviral Agents/therapeutic use , Apoptosis , Brain Neoplasms/drug therapy , Brain Neoplasms/radiotherapy , Breast Neoplasms/drug therapy , Breast Neoplasms/radiotherapy , Cisplatin/pharmacology , Combined Modality Therapy , Doxorubicin/pharmacology , Early Growth Response Protein 1 , Ganciclovir/metabolism , Gene Transfer Techniques , Glioblastoma/drug therapy , Glioblastoma/radiotherapy , Glioblastoma/therapy , Green Fluorescent Proteins/metabolism , Humans , Neutrons , Promoter Regions, Genetic , Radiation-Sensitizing Agents/therapeutic use , Response Elements/genetics , Simplexvirus/enzymology , Simplexvirus/genetics , Thymidine Kinase/genetics , Thymidine Kinase/metabolism , Tumor Cells, Cultured , Zinc FingersABSTRACT
The aim of this paper is to study the correction of prostate motion and position during external beam therapy. The correction was performed using a commercially available ultrasound-based repositioning tool. Electronic portal imaging with the use of fiducial markers was used to assess efficacy and accuracy. Patients undergoing radiation treatment for adenocarcinoma of the prostate were enrolled in a positioning study. Fifteen patients had five to six gold fiducial markers implanted in their prostate. These patients were positioned daily in a standard manner and then were repositioned every other day using an ultrasound-based correction system. Every fraction of a patients' treatment was imaged. This yielded 156 image pairs with and 119 pairs without repositioning available for analysis. This group of patients with markers had the following residual positions measured after the use of ultrasound repositioning. A mean error of -0.4 mm (LL), -2.6 mm (CC), and +2.5 mm (AP) with a standard deviation of 4.3, 5.4, and 5.7 mm. In two directions the improvements of treatment using the ultrasound correction were smaller than the precision of this experiment. They were no larger than 0.81 mm (LAT), and 0.95 mm (CC). In the AP direction a significant improvement was found of 1.6 mm. A highly significant correlation (p < 0.001) was found between the residual errors in the cranio-caudal direction and the shifts performed on the basis of the ultrasound measurements (Spearman ranking R = 0.53). We presented a method to objectively estimate improvements by a correction scheme. This method applied to ultrasound-based adjustment showed significant improvement in one direction and no measurable improvement in two other directions.