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Targeting the 19S proteasomal subunit, Rpt4, for the treatment of colon cancer
Karen Boland1, Lorna Flanagan2, Niamh McCawley3
1Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland; Department of Gastroenterology, Beaumont Hospital, Beaumont, Dublin 9, Ireland.
Abstract:
Deregulation of the ubiquitin-proteasome pathway has been frequently observed in a number of malignancies. Using quantitative Western blotting of normal and matched tumour tissue, we here identified a significant increase in the 19S proteasome subunit Rpt4 in response to chemoradiation in locally advanced rectal cancer patients with unfavourable outcome. We therefore explored the potential of Rpt4 reduction as a therapeutic strategy in colorectal cancer (CRC). Utilizing siRNA to down regulate Rpt4 expression, we show that silencing of Rpt4 reduced proteasomal activity and induced endoplasmic reticulum stress. Gene silencing of Rpt4 also inhibited cell proliferation, reduced clonogenic survival and induced apoptosis in HCT-116 colon cancer cells. We next developed a cell penetrating peptide-based nanoparticle delivery system to achieve in vivo gene silencing of Rpt4. Administration of Rpt4 siRNA nanoparticles reduced tumour growth and improved survival in a HCT-116 colon cancer xenograft tumour model in vivo. Collectively, our data suggest that inhibition of Rpt4 represents a novel strategy for the treatment of CRC.
Insights
Elevated Rpt4 levels correlate with poor outcomes in rectal cancer. Inhibiting Rpt4 via siRNA nanoparticles reduced tumor growth and improved survival, suggesting Rpt4 as a therapeutic target for colorectal cancer (CRC).
Area of Science:
- Molecular Biology
- Oncology
- Cancer Therapeutics
Background:
- The ubiquitin-proteasome pathway is frequently dysregulated in malignancies.
- Increased levels of the 19S proteasome subunit Rpt4 are associated with unfavorable outcomes in rectal cancer patients treated with chemoradiation.
Purpose of the Study:
- To investigate the therapeutic potential of targeting Rpt4 in colorectal cancer (CRC).
- To evaluate the efficacy of Rpt4 gene silencing as a treatment strategy for CRC.
Main Methods:
- Quantitative Western blotting to assess Rpt4 levels in patient tissues.
- siRNA-mediated gene silencing of Rpt4 in HCT-116 colon cancer cells.
- Development of a cell-penetrating peptide-based nanoparticle delivery system for Rpt4 siRNA.
- In vivo studies using a HCT-116 colon cancer xenograft model.
Main Results:
- Rpt4 silencing reduced proteasomal activity and induced endoplasmic reticulum stress.
- Gene silencing of Rpt4 inhibited cell proliferation, clonogenic survival, and induced apoptosis in vitro.
- In vivo administration of Rpt4 siRNA nanoparticles significantly reduced tumor growth and improved survival.
Conclusions:
- Rpt4 is a potential therapeutic target for colorectal cancer.
- Inhibition of Rpt4 represents a novel strategy for CRC treatment.
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