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Cellular response to an antisense-mediated shift of Bcl-x pre-mRNA splicing and antineoplastic agents
Danielle R Mercatante1, James L Mohler, Ryszard Kole
1UNC Lineberger Comprehensive Cancer Center and Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599-7295, USA.
Abstract:
Overexpression of Bcl-xL, an anti-apoptotic member of the Bcl-2 family, negatively correlates with the sensitivity of various cancers to chemotherapeutic agents. We show here that high levels of expression of Bcl-xL promoted apoptosis of cells treated with an antisense oligonucleotide (5'Bcl-x AS) that shifts the splicing pattern of Bcl-x pre-mRNA from the anti-apoptotic variant, Bcl-xL, to the pro-apoptotic variant, Bcl-xS. This surprising finding illustrates the advantage of antisense-induced modulation of alternative splicing versus down-regulation of targeted genes. It also suggests a specificity of the oligonucleotide effects since non-cancerous cells with low levels of Bcl-xL should resist the treatment. 5'Bcl-x AS sensitized cells to several antineoplastic agents and radiation and was effective in promoting apoptosis of MCF-7/ADR cells, a breast cancer cell line resistant to doxorubicin via overexpression of the mdr1 gene. Efficacy of 5'Bcl-x AS combined with chemotherapeutic agents in the PC3 prostate cancer cell line may be translated to clinical prostate cancer since recurrent prostate cancer tissue samples expressed higher levels of Bcl-xL than benign prostate tissue. Treatment with 5'Bcl-x AS may enhance the efficacy of standard anti-cancer regimens and should be explored, especially in recurrent prostate cancer.
Insights
Antisense oligonucleotides targeting Bcl-xL (5'Bcl-x AS) promote cancer cell apoptosis by shifting splicing to the pro-apoptotic Bcl-xS variant. This approach enhances sensitivity to chemotherapy and radiation, particularly in resistant cancers like prostate cancer.
Area of Science:
- Molecular Biology
- Cancer Research
- Drug Development
Background:
- Bcl-xL, an anti-apoptotic protein, is overexpressed in many cancers, correlating with reduced sensitivity to chemotherapy.
- Targeting Bcl-xL is a strategy to overcome cancer drug resistance.
Purpose of the Study:
- To investigate the efficacy of 5'Bcl-x AS, an antisense oligonucleotide, in modulating Bcl-x alternative splicing and inducing apoptosis in cancer cells.
- To evaluate the potential of 5'Bcl-x AS to sensitize cancer cells to conventional chemotherapeutic agents and radiation.
Main Methods:
- Utilized 5'Bcl-x AS to induce a shift in Bcl-x pre-mRNA splicing from the anti-apoptotic Bcl-xL isoform to the pro-apoptotic Bcl-xS isoform.
- Assessed the impact of 5'Bcl-x AS on apoptosis induction in various cancer cell lines, including MCF-7/ADR and PC3.
- Evaluated the combined efficacy of 5'Bcl-x AS with chemotherapeutic agents and radiation.
Main Results:
- High Bcl-xL expression levels were found to promote apoptosis in cells treated with 5'Bcl-x AS.
- 5'Bcl-x AS treatment sensitized cancer cells to multiple antineoplastic agents and radiation.
- The oligonucleotide was effective in inducing apoptosis in doxorubicin-resistant MCF-7/ADR breast cancer cells.
- Combined treatment with 5'Bcl-x AS and chemotherapy showed efficacy in PC3 prostate cancer cells, with higher Bcl-xL levels in recurrent prostate cancer tissues.
Conclusions:
- Antisense-induced modulation of alternative splicing offers an advantage over simple gene down-regulation.
- 5'Bcl-x AS demonstrates potential as an adjuvant therapy to enhance the efficacy of standard anti-cancer treatments.
- Further exploration of 5'Bcl-x AS is warranted, especially for recurrent prostate cancer.