ITRAQ Identification of Candidate Serum Biomarkers Associated with Metastatic Progression of Human Prostate Cancer

Ishtiaq Rehman,Phillip C Wright,Jenny Down,Freddie C Hamdy,Ow Saw Yen,Simon S Cross,Adam Glen,Caroline A Evans,Colby L Eaton,Giancarlo Pesce,George N Thalmann,Joshua T Phillips,Karl X Chai

doi:10.1371/journal.pone.0030885

Abstract

A major challenge in the management of patients with prostate cancer is identifying those individuals at risk of developing metastatic disease, as in most cases the disease will remain indolent. We analyzed pooled serum samples from 4 groups of patients (n = 5 samples/group), collected prospectively and actively monitored for a minimum of 5 yrs. Patients groups were (i) histological diagnosis of benign prostatic hyperplasia with no evidence of cancer ‘BPH’, (ii) localised cancer with no evidence of progression, ‘non-progressing’ (iii) localised cancer with evidence of biochemical progression, ‘progressing’, and (iv) bone metastasis at presentation ‘metastatic’. Pooled samples were immuno-depleted of the 14 most highly abundant proteins and analysed using a 4-plex iTRAQ approach. Overall 122 proteins were identified and relatively quantified. Comparisons of progressing versus non-progressing groups identified the significant differential expression of 25 proteins (p<0.001). Comparisons of metastatic versus progressing groups identified the significant differential expression of 23 proteins. Mapping the differentially expressed proteins onto the prostate cancer progression pathway revealed the dysregulated expression of individual proteins, pairs of proteins and ‘panels’ of proteins to be associated with particular stages of disease development and progression. The median immunostaining intensity of eukaryotic translation elongation factor 1 alpha 1 (eEF1A1), one of the candidates identified, was significantly higher in osteoblasts in close proximity to metastatic tumour cells compared with osteoblasts in control bone (p = 0.0353, Mann Whitney U). Our proteomic approach has identified leads for potentially useful serum biomarkers associated with the metastatic progression of prostate cancer. The panels identified, including eEF1A1 warrant further investigation and validation.

Highlights

In Europe and the US, prostate cancer is the second most common cancer diagnosis and the third most common cause of cancer-related deaths in men [1,2]
In an effort to identify leads for potentially useful serum biomarkers for prostate cancer diagnosis and progression, we profiled pooled serum samples from 4 carefully selected groups of patients representing the various stages of prostate cancer development and progression using a 4-plex isobaric Tags for Relative and Absolute Quantitation’ (iTRAQ) approach
Of the proteins previously associated with prostate cancer; C-reactive protein (CRP) is an acute phase reactant (APR) protein produced by the liver in response to inflammation

Summary

Introduction

In Europe and the US, prostate cancer is the second most common cancer diagnosis and the third most common cause of cancer-related deaths in men [1,2]. Most patients with prostate cancer are diagnosed at an early stage, but even with screening over 7% of cases develop metastatic disease [4]. Bone is the most common site for prostate cancer metastasis and is associated with bone pain, spinal cord compression and marrow failure [4]. Bone metastatic lesions are determined by imaging such as isotope bone scanning, the identification of a serum based biomarker(s) for predicting the susceptibility of patients to develop bone metastasis could enable a more accurate clinical assessment of the disease and help guide therapy

Methods

Results

Conclusion