This article is part of the supplement: São Paulo Advanced School of Comparative Oncology: Abstracts

Open Access Poster presentation

Targeting uroporphyrinogen decarboxylase for head and neck cancer treatment

Emma Ito12*, Shijun Yue2, Eduardo H Moriyama1, Angela B Hui2, Inki Kim2, Wei Shi2, Nehad M Alajez2, Nirmal Bhogal2, GuoHua Li3, Alessandro Datti45, Aaron D Schimmer12, Brian C Wilson1, Peter P Liu3, Daniel Durocher4, Benjamin G Neel12, Brian O’Sullivan67, Bernard Cummings67, Rob Bristow1267, Jeff Wrana4 and Fei-Fei Liu1267

Author Affiliations

1 Department of Medical Biophysics, University of Toronto, Toronto, Canada

2 Ontario Cancer Institute, Campbell Family Cancer Research Institute, University Health Network, Toronto, Canada

3 Toronto General Research Institute, University Health Network, Toronto, Canada

4 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada

5 Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy

6 Department of Radiation Oncology, Princess Margaret Hospital, University Health Network, Toronto, Canada

7 Department of Radiation Oncology, University of Toronto, Toronto, Canada

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BMC Proceedings 2013, 7(Suppl 2):P19  doi:10.1186/1753-6561-7-S2-P19

The electronic version of this article is the complete one and can be found online at:

Published:4 April 2013

© 2013 Ito et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Head and neck cancer (HNC) is the 8th most common malignancy worldwide. Despite advances in therapeutic options over the last few decades, treatment toxicities and overall clinical outcomes have remained disappointing, underscoring a need to develop novel therapeutic approaches, particularly those that enhance tumor cell death, while minimizing damage to the surrounding normal tissues.

Materials and methods

An RNA interference (RNAi)-based high-throughput screen (HTS) was performed for the large-scale identification of novel genes that will selectively sensitize HNC cells to ionizing radiation. The Dharmacon Protein Kinase and Druggable Genome siRNA Libraries were screened using FaDu cells (human hypopharyngeal squamous cell cancer). Radiosensitizing targets were subjected to in vitro and in vivo characterizations.


Sixty-seven target sequences with potential radiosensitizing effects were identified. Targets reducing the surviving fraction by >50% at 2 Gy relative to their un-irradiated counterparts were selected for further evaluation. A key regulator of heme biosynthesis, uroporphyrinogen decarboxylase (UROD), was thereby identified as a novel tumor-selective radiosensitizing target, demonstrating both in vitro and in vivo efficacy. Radiosensitization appeared to be mediated via enhancement of tumor oxidative stress from perturbation of iron homeostasis and increased free radical production. UROD was significantly over-expressed in HNC patient biopsies, wherein lower pre-radiation mRNA levels correlated with improved survival, suggesting UROD could potentially predict radiation response. UROD down-regulation also radiosensitized several different human cancer models, while sparing normal cells.


An RNAi-based radiosensitizer HTS has revealed UROD as a potent tumor-selective sensitizer for radiation, with potential relevance to many human malignancies.

Financial support

Canadian Institutes of Health Research (CIHR; grant 69023); Elia Chair in Head and Neck Cancer Research; philanthropic support from Wharton Family, J. Finley, and G. Tozer; Campbell Family Institute for Cancer Research; Ministry of Health and Long-Term Planning; CIHR Resource Maintenance grant (PRG-82679).