Radiosensitization in vivo by histone deacetylase inhibition with no increase in early normal tissue radiation toxicity

Blaz Groselj, Jia Ling Ruan, Helen Scott, Jessica Gorrill, Judith Nicholson, Jacqueline Kelly, Selvakumar Anbalagan, James Thompson, Michael R.L. Stratford, Sarah J. Jevons, Ester M. Hammond, Cheryl L. Scudamore, Martin Kerr, Anne E. Kiltie*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

As the population ages, more elderly patients require radiotherapy-based treatment for their pelvic malignancies, including muscle-invasive bladder cancer, as they are unfit for major surgery. Therefore, there is an urgent need to find radiosensitizing agents minimally toxic to normal tissues, including bowel and bladder, for such patients. We developed methods to determine normal tissue toxicity severity in intestine and bladder in vivo, using novel radiotherapy techniques on a small animal radiation research platform (SARRP). The effects of panobinostat on in vivo tumor growth delay were evaluated using subcutaneous xenografts in athymic nude mice. Panobinostat concentration levels in xenografts, plasma, and normal tissues were measured in CD1-nude mice. CD1-nude mice were treated with drug/irradiation combinations to assess acute normal tissue effects in small intestine using the intestinal crypt assay, and later effects in small and large intestine at 11 weeks by stool assessment and at 12 weeks by histologic examination. In vitro effects of panobinostat were assessed by qPCR and of panobinostat, TMP195, and mocetinostat by clonogenic assay, and Western blot analysis. Panobinostat resulted in growth delay in RT112 bladder cancer xenografts but did not significantly increase acute (3.75 days) or 12 weeks' normal tissue radiation toxicity. Radiosensitization by panobinostat was effective in hypoxic bladder cancer cells and associated with class I HDAC inhibition, and protein downregulation of HDAC2 and MRE11. Pan-HDAC inhibition is a promising strategy for radiosensitization, but more selective agents may be more useful radiosensitizers clinically, resulting in fewer systemic side effects.

Original languageEnglish
Pages (from-to)381-392
Number of pages12
JournalMolecular Cancer Therapeutics
Volume17
Issue number2
DOIs
Publication statusPublished - Feb 2018

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