UNIVERSITY OF HULL
Towards Developing a Screening Assay for Predicting Biomarkers of Radiotherapy
Resistance
Bashak Onal, MBiomed Sci
Second year PhD student
School of Biological, Biomedical and Environmental Sciences
University of Hull
Address: Cancer Biology Proteomics Group, Research Labs, Daisy Building, Castle Hill
Hospital, Hull, HU16 5JQ
T: 01482 461895
E: B.Onal@2012.hull.ac.uk
Abstract word count: 395 words
Abstract
Background
Resistance to radiotherapy is a challenge for clinicians in the management of cancer
patients. This not only presents a barrier for effective cancer treatment but also means that
those patients with radioresistant tumours endure the harmful side effects for no therapeutic
gain. For these reasons, it is important to identify biomarkers which can predict tumour
response to radiotherapy prior to treatment.
Purpose
The aim of this project is to identify putative protein biomarkers of radiotherapy resistance
using radioresistant human cancer cell line models as well as cancer tissue biopsies by
employing comparative proteomic tools. It is hoped that these biomarkers can be used to
produce a predictive assay platform, enabling routine screening of cancer for radioresistant
properties at the point of diagnosis. Such screening will enable the personalisation of
radiotherapy treatment and as a result will provide a major breakthrough for the treatment of
cancer patients today.
Methods
Following ethical approval, two pairs of pre-treatment rectal cancer biopsy samples
(radioresistant versus radiosensitive samples) were investigated to identify differentially
expressed proteins (DEPs) involved in mediating resistance to radiotherapy. These were
studied using an antibody microarray proteomics platform. Data obtained from the
experiments were subjected to data mining using Ingenuity Pathway Analysis (IPA) which
mapped these DEPs onto their most relevant canonical signalling pathways.
Results
The antibody microarray analysis of the clinical samples revealed 25 DEPs from the first
experiment and 46 from the second experiment. The IPA analysis of this data combined
generated 253 canonical pathways. Amongst these, the most interesting pathways included
p53 signalling (12 DEPs mapped), death receptor signalling (7 DEPs mapped), apoptosis
signalling (5 DEPs mapped) and EGF signalling (4 DEPs mapped). A number of DEPs were
independently identified in previous proteomic analysis of radioresistant cell lines.
Radiotherapy is known to initiate cellular apoptosis via the intrinsic (mitochondrial) pathway.
However, the identification of some regulatory proteins involved in the extrinsic apoptotic
pathway has revealed a novel link between radiotherapy and the extrinsic death receptor
pathway.
Discussion and conclusion
Antibody microarray analysis of rectal cancer biopsy samples has enabled the identification
of a number of DEPs which may be involved in mediating response to radiotherapy. The
novel identification of the proteins involved in death receptor signalling may potentially be
classed putative biomarkers of radiotherapy resistance. However, further confirmation with
western blotting and validation with immunohistochemistry is required before such
biomarkers could be introduced into routine clinical management of cancer patients.