Research Papers:

Synergy between histone deacetylase inhibitors and DNA-damaging agents is mediated by histone deacetylase 2 in colorectal cancer

Samer Alzoubi, Leigh Brody, Sunniyat Rahman, Anne-Laure Mahul-Mellier, Nicolas Mercado, Kazuhiro Ito, Mona El-Bahrawy, Andrew Silver, Alan Boobis, Jimmy D. Bell and Nabil Hajji _

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Oncotarget. 2016; 7:44505-44521. https://doi.org/10.18632/oncotarget.9887

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Samer Alzoubi1, Leigh Brody2, Sunniyat Rahman1, Anne-Laure Mahul-Mellier3, Nicolas Mercado4, Kazuhiro Ito4, Mona El-Bahrawy5, Andrew Silver6, Alan Boobis1, Jimmy D. Bell2, Nabil Hajji1

1Department of Medicine, Division of Experimental Medicine, Centre for Pharmacology & Therapeutics, Toxicology Unit, Imperial College London, London, UK

2Department of Life Sciences, Research Centre for Optimal Health, University of Westminster, London, UK

3Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

4Airway Disease Section, National Heart and Lung Institute, Imperial College, London, UK

5Department of Histopathology, Imperial College London, London, UK

6Colorectal Cancer Genetics, Centre for Genomics & Child Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, London, UK

Correspondence to:

Nabil Hajji, email: [email protected]

Keywords: colorectal cancer, histone acetylation, drug resistance and in vivo imaging, HDAC2, p53

Received: July 08, 2015     Accepted: May 28, 2016     Published: June 7, 2016


Previous studies have associated the overexpression of histone deacetylase 2 (HDAC2) and the presence of TP53 mutations with the progression to advanced stage drug resistant colorectal cancer (CRC). However, the mechanistic link between HDAC2 expression and the TP53 mutational status has remained unexplored. Here, we investigated the function of HDAC2 in drug resistance by assessing the synergistic effects of DNA-targeted chemotherapeutic agents and HDAC inhibitors (HDACis) on two TP53-mutated colorectal adenocarcinoma CRC cell lines (SW480 and HT-29) and on the TP53-wild type carcinoma cell line (HCT116 p53+/+) and its TP53 deficient sub-line (HCT116 p53-/-). We showed that in the untreated SW480 and HT-29 cells the steady-state level of HDAC2 was low compared to a TP53-wild type carcinoma cell line (HCT116 p53+/+). Increased expression of HDAC2 correlated with drug resistance, and depletion by shRNA sensitised the multi-drug resistance cell line HT-29 to CRC chemotherapeutic drugs such as 5-fluorouracil (5-FU) and oxaliplatin (Oxa). Combined treatment with the HDACi suberoylanilide hydroxamic acid plus 5-FU or Oxa reduced the level of HDAC2 expression, modified chromatin structure and induced mitotic cell death in HT-29 cells. Non-invasive bioluminescence imaging revealed significant reductions in xenograft tumour growth with HDAC2 expression level reduced to <50% in treated animals. Elevated levels of histone acetylation on residues H3K9, H4K12 and H4K16 were also found to be associated with resistance to VPA/Dox or SAHA/Dox treatment. Our results suggest that HDAC2 expression rather than the p53 mutation status influences the outcome of combined treatment with a HDACi and DNA-damaging agents in CRC.

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