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Updated: May 9, 2026
An Orthotopic Bladder Cancer Model for Gene Delivery Studies
Published on: December 1, 2013
Radiosensitisation of bladder cancer cells by panobinostat is modulated by Ku80 expression
Blaz Groselj1, Martin Kerr, Anne E Kiltie
1Gray Institute for Radiation Oncology and Biology, Department of Oncology, University of Oxford, United Kingdom.
Background And Purpose:
In muscle-invasive bladder cancer there is an urgent need to identify relatively non-toxic radiosensitising agents for use in elderly patients. Histone deacetylase inhibitors radiosensitise tumour cells but not normal cells in vitro and variously downregulate DNA damage signalling, homologous recombination (HR) and non-homologous end-joining (NHEJ) repair proteins. We investigated panobinostat (PAN) as a potential radiosensitiser in bladder cancer cells.
Materials And Methods:
Clonogenic assays were performed in RT112 bladder cancer cells, and RT112 cells stably knocked down for RAD51 or Ku80 by shRNAi. Resolution of γH2AX foci was determined by immunofluorescence confocal microscopy, cell cycle progression by FACS analysis and protein expression by western blotting.
Results:
PAN had a greater radiosensitising effect in Ku80KD than RT112 or RAD51KD cells; enhancement ratios 1.35 for Ku80KD at 10nM (IC(20) for Ku80KD) and 1.31 for RT112 and RAD51KD at 25 nM (IC(40) for both). PAN downregulated MRE11, NBS1 and RAD51, but not Ku70 and Ku80, increased γH2AX foci formation in a dose-dependent manner and delayed γH2AX foci repair after ionising radiation.
Conclusions:
PAN acts as a radiosensitiser in bladder cancer cell lines, and appears to target HR rather than NHEJ. As muscle-invasive bladder tumours have reduced Ku-DNA binding, PAN could be particularly useful as a radiosensitiser in bladder cancer.
Insights
Panobinostat (PAN) enhances bladder cancer cell radiosensitivity by targeting homologous recombination (HR) DNA repair, not non-homologous end-joining (NHEJ). This histone deacetylase inhibitor shows promise for elderly patients with muscle-invasive bladder cancer.
Area of Science:
- Oncology
- Cancer Biology
- Radiotherapy
Background:
- Muscle-invasive bladder cancer requires non-toxic radiosensitizers, especially for elderly patients.
- Histone deacetylase inhibitors (HDACi) show radiosensitizing potential by affecting DNA repair pathways.
- Panobinostat (PAN), an HDACi, was investigated for radiosensitizing effects in bladder cancer.
Purpose of the Study:
- To evaluate panobinostat (PAN) as a radiosensitizing agent in bladder cancer.
- To determine PAN's effect on DNA damage repair pathways, specifically homologous recombination (HR) and non-homologous end-joining (NHEJ).
- To assess PAN's efficacy in bladder cancer cells with varying DNA repair protein expression.
Main Methods:
- Clonogenic assays were used to assess cell survival after irradiation with PAN.
- RAD51 and Ku80 knockdown bladder cancer cells were utilized to investigate specific DNA repair pathway involvement.
- Immunofluorescence microscopy, FACS analysis, and western blotting were employed to analyze DNA damage foci, cell cycle, and protein expression.
Main Results:
- Panobinostat demonstrated a radiosensitizing effect in bladder cancer cells.
- PAN showed a greater radiosensitizing effect in cells with reduced Ku80 expression.
- PAN downregulated key homologous recombination (HR) proteins (MRE11, NBS1, RAD51) and delayed DNA damage repair (γH2AX foci resolution).
Conclusions:
- Panobinostat acts as a radiosensitizer in bladder cancer cell lines.
- PAN appears to primarily target the homologous recombination (HR) DNA repair pathway.
- Given that muscle-invasive bladder tumors often have impaired non-homologous end-joining (NHEJ), PAN could be a valuable radiosensitizer in this context.
