Proteomic identification of putative biomarkers of radiotherapy resistance

Scaife, Lucy

Abstract

Background
Currently, tumour response to radiotherapy cannot be predicted meaning that those patients with tumours resistant to the therapy endure the harmful side effects associated with ionising radiation in the absence of therapeutic gain. The aim of this project was to identify protein biomarkers predictive of radiotherapy response using comparative proteomic platforms to study radioresistant cell line models. The identification of such biomarkers will enable radiotherapy to be tailored on an individual patient basis and hence increase treatment efficacy.

Methods
Seven radioresistant (RR) cell line models derived from breast, head and neck (oral), and rectal cancers were investigated to identify differentially expressed proteins (DEPs) associated with radiotherapy resistance. This included the establishment of 2 RR rectal cancer cell line models and the proteomic analysis of 2 RR oral cancer cell lines and 2 RR rectal cancer cell lines. Proteomic analysis included 3 different platforms, namely antibody microarray, 2D MS and iTRAQ. Data mining of all biomarker discovery data, from all 7 novel RR cell lines was carried out using Ingenuity Pathway Analysis (IPA) which identified canonical pathways associated with the data. Protein candidates from selected canonical pathways were confirmed by western blotting and assessed clinically using immunohistochemistry.

Results
Following the combination of all biomarker discovery data for all 7 RR cell lines, 373 unique DEPs were successfully mapped onto the Ingenuity Knowledge Base, generating 339 canonical pathways. Of these, 13 of the most relevant pathways were selected for further interpretation. Several proteasomal subunits were identified during the biomarker discovery phase and were mapped onto the protein ubiquitination pathway by IPA. DR4, was identified in 4/7 RR cell lines and was mapped onto the death receptor signalling pathway by IPA. Radiotherapy is typically thought to induce cellular apoptosis via the intrinsic (mitochondrial) pathway, therefore the repeated identification of the DR4 protein involved in the extrinsic apoptotic pathway has potentially lead to the discovery of a novel relationship between radiotherapy and the extrinsic death receptor pathway. The differential expression of both the 26S Proteasome and DR4 were confirmed by western blotting. Clinical assessment using immunohistochemistry revealed a significant association between expression of the 26S Proteasome and radioresistance in breast cancer.

Discussion
A large number of DEPs which may be associated with radiotherapy resistance in breast, oral and rectal cancers have been identified using comparative proteomic platforms. The protein ubiquitination pathway and the death receptor signalling pathway may play a significant role in radioresistance and proteins within these pathways may be putative biomarkers of radiotherapy response.

Citation

Scaife, L. Proteomic identification of putative biomarkers of radiotherapy resistance. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4214086

• Thesis Type: Thesis
• Deposit Date: May 7, 2013
• Publicly Available Date: Feb 22, 2023
• Keywords: Medicine
• Public URL: https://hull-repository.worktribe.com/output/4214086
• Additional Information: Postgraduate Medical Institute, The University of Hull
• Award Date: Jul 1, 2012