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Published on: August 13, 2013
Transcriptional targeting of adenoviral vector through the CXCR4 tumor-specific promoter
1Division of Human Gene Therapy, Department of Medicine, The Gene Therapy Center, University of Alabama at Birmingham, AL 35291, USA.
Abstract:
Adenoviral vectors are considered to be good gene delivery vectors for cancer gene therapy due to their wide host tissue range and cell cycle-independent infectivity. However, the disadvantages include the lack of specificity for cancer cells and the high liver accumulation in vivo. The human CXCR4 gene is expressed at high levels in many types of cancers, but is repressed in the liver. We explored the CXCR4 promoter as a candidate to restrict adenoviral transgene expression to tumor cells with a low expression in host tissues. The luciferase activities in multiple cancer cell lines infected with recombinant adenovirus reAdGL3BCXCR4 or the control vector reAdGL3BCMV revealed that the CXCR4 promoter exhibited relatively high transcriptional activity in a breast cancer cell line, MDA-MB-361, and two ovarian cancer cell lines, OVCAR-3 and SKOV3. ip1, 65% (P=0.0087), 16.7% (P=0.1) and 20% (P=0.0079) compared to that of the CMV promoter, respectively, and low expression, 4.9 and 0.1%, respectively, in both normal cell lines HFBC and HMEC. In addition, CXCR4 had a low expression of luciferase (0.32%) compared to that of the CMV promoter in mouse liver in vivo. The data also revealed that the CXCR4 promoter was a stronger tumor-specific promoter (TSP) than the Cox-2M promoter in primary melanomas obtained from two patients. The CXCR4 promoter is shown to have a 'tumor-on' and 'liver-off' status in vitro and in vivo, and CXCR4 may prove to be a good candidate TSP for cancer gene therapy approaches for melanoma and breast cancers.
Insights
The CXCR4 promoter restricts adenoviral gene expression to tumor cells, showing high activity in breast and ovarian cancers but low expression in normal tissues and the liver. This makes it a promising tumor-specific promoter for cancer gene therapy.
Area of Science:
- Oncolytic virotherapy
- Gene therapy vectors
- Molecular oncology
Background:
- Adenoviral vectors are widely used in cancer gene therapy due to broad infectivity.
- Limitations include lack of cancer cell specificity and high liver accumulation.
- The human CXCR4 gene is highly expressed in many cancers but repressed in the liver.
Purpose of the Study:
- To evaluate the CXCR4 promoter as a tumor-specific promoter (TSP) for adenoviral vectors.
- To restrict transgene expression to cancer cells and minimize off-target effects in normal tissues.
- To assess CXCR4 promoter activity in vitro and in vivo for cancer gene therapy applications.
Main Methods:
- Constructed recombinant adenoviruses utilizing the CXCR4 promoter (reAdGL3BCXCR4) and a control CMV promoter (reAdGL3BCMV).
- Assessed luciferase activity in various cancer and normal cell lines (in vitro).
- Evaluated luciferase expression in mouse liver (in vivo) and compared CXCR4 promoter with Cox-2M promoter in patient-derived melanomas.
Main Results:
- CXCR4 promoter showed high transcriptional activity in breast (MDA-MB-361) and ovarian (OVCAR-3, SKOV3) cancer cell lines.
- Exhibited significantly lower expression in normal human fibroblast (HFBC) and mammary epithelial (HMEC) cells.
- Demonstrated minimal expression in mouse liver in vivo (0.32% of CMV promoter) and outperformed Cox-2M promoter in melanoma samples.
Conclusions:
- The CXCR4 promoter functions as a 'tumor-on' and 'liver-off' switch.
- It is a potent tumor-specific promoter candidate for cancer gene therapy, particularly for melanoma and breast cancers.
- CXCR4 promoter offers improved specificity and reduced liver toxicity for adenoviral vector-based therapies.
