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Updated: Aug 12, 2026
Orthotopic Injection of Breast Cancer Cells into the Mammary Fat Pad of Mice to Study Tumor Growth.
Published on: February 8, 2015
Enhanced gene expression in breast cancer cells in vitro and tumors in vivo
Huanzhang Lu1, Yufeng Zhang, David D Roberts
1Center for Cell and Gene Therapy, National Cancer Institute, National Institutes of Health, Building 10, Room 2A27, Bethesda, Maryland 20892, USA.
Abstract:
Gene therapy clinical trials for cancer frequently produce inconsistent results. Some of this variability could result from differences in transcriptional regulation that limit expression of therapeutic genes in specific cancers. Systemic liposomal delivery of a nonviral plasmid DNA showed efficacy in animal models for several cancers. However, we observed large differences in the levels of gene expression from a CMV promoter-enhancer between lung and breast cancers. To optimize gene expression in breast cancer cells in vitro and in vivo, we created a new promoter-enhancer chimera to regulate gene expression. Serial analyses of gene expression data from a panel of breast carcinomas and normal breast cells predicted that the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter is highly active in breast cancers. Furthermore, GAPDH is up-regulated by hypoxia, which is common in tumors. We added the GAPDH promoter, including the hypoxia enhancer sequences, to our in vivo gene expression plasmid. The novel CMV-GAPDH promoter-enhancer showed up to 70-fold increased gene expression in breast tumors compared to the optimized CMV promoter-enhancer alone. No significant increase in gene expression was observed in other tissues. These data demonstrate tissue-specific effects on gene expression after nonviral delivery and suggest that gene delivery systems may require plasmid modifications for the treatment of different tumor types. Furthermore, expression profiling can facilitate the design of optimal expression plasmids for use in specific cancers.
Insights
Optimizing gene therapy for breast cancer, researchers developed a novel promoter-enhancer. This new system significantly increased therapeutic gene expression in breast tumors, improving cancer treatment potential.
Area of Science:
- Oncology
- Molecular Biology
- Gene Therapy
Background:
- Gene therapy for cancer shows variable results due to transcriptional regulation differences.
- Nonviral plasmid DNA delivery has shown efficacy but exhibits variable gene expression across cancer types.
Purpose of the Study:
- To optimize gene expression in breast cancer cells for improved therapeutic outcomes.
- To develop a novel promoter-enhancer chimera for enhanced gene delivery in breast cancer.
Main Methods:
- Created a new promoter-enhancer chimera by combining CMV with the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter and hypoxia enhancer sequences.
- Utilized serial analyses of gene expression data to identify cancer-specific active promoters.
- Evaluated gene expression levels in breast tumors and other tissues in vivo.
Main Results:
- The novel CMV-GAPDH promoter-enhancer achieved up to 70-fold increased gene expression in breast tumors compared to the CMV promoter alone.
- Gene expression was significantly enhanced specifically in breast tumors, with no substantial increase in other tissues.
- Expression profiling facilitated the design of optimized expression plasmids for specific cancer types.
Conclusions:
- Gene delivery systems may require specific plasmid modifications for effective treatment of different tumor types.
- Tissue-specific promoter engineering is crucial for enhancing therapeutic gene expression in targeted cancers.
- Expression profiling is a valuable tool for designing optimal gene delivery vectors for cancer therapy.
