Quantitative proteomic analysis in HCV-induced HCC reveals sets of proteins with potential significance for racial disparity

Simon T Dillon,Xiaoxing Feng,Manoj K Bhasin,David W Koh,Sayed S Daoud

doi:10.1186/1479-5876-11-239

Abstract

BackgroundThe incidence and mortality of hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) is higher in African Americans (AA) than other racial/ethnic groups in the U.S., but the reasons for this disparity are unknown. There is an urgent need for the discovery of novel molecular signatures for HCV disease progression to understand the underlying biological basis for this cancer rate disparity to improve the clinical outcome.MethodsWe performed differential proteomics with isobaric labeling tags for relative and absolute quantitation (iTRAQ) and MS/MS analysis to identify proteins differentially expressed in cirrhotic (CIR) and HCC as compared to normal tissues of Caucasian American (CA) patients. The raw data were analyzed using the ProteinPilot v3.0. Searches were performed against all known sequences populating the Swiss-Prot, Refseq, and TrEMBL databases. Quality control analyses were accomplished using pairwise correlation plots, boxplots, principal component analysis, and unsupervised hierarchical clustering. Supervised analysis was carried out to identify differentially expressed proteins. Candidates were validated in independent cohorts of CA and AA tissues by qRT-PCR or Western blotting.ResultsA total of 238 unique proteins were identified. Of those, around 15% were differentially expressed between normal, CIR & HCC groups. Target validation demonstrates racially distinct alteration in the expression of certain proteins. For example, the mRNA expression levels of transferrin (TF) were 2 and18-fold higher in CIR and HCC in AA as compared to CA. Similarly; the expression of Apolipoprotein A1 (APOA1) was 7-fold higher in HCC of AA. This increase was mirrored in the protein expression levels. Interestingly, the level of hepatocyte nuclear factor4α (HNF4α) protein was down regulated in AA, whereas repression of transcription is seen more in CA compared to AA. These data suggest that racial disparities in HCC could be a consequence of differential dysregulation of HNF4α transcriptional activity.ConclusionThis study identifies novel molecular signatures in HCV-induced HCC using iTRAQ-based tissue proteomics. The proteins identified will further enhance a molecular explanation to the biochemical mechanism(s) that may play a role in HCC racial disparities.

Highlights

The incidence and mortality of hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) is higher in African Americans (AA) than other racial/ethnic groups in the U.S, but the reasons for this disparity are unknown
Clinical characteristics of the study population A total of 26 liver and tumor tissue samples from Caucasian American (CA) and AA populations were used in this study (Additional file 2: Table S1)
There were no significant differences of age and sex between cases in the two groups

Summary

Introduction

The incidence and mortality of hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) is higher in African Americans (AA) than other racial/ethnic groups in the U.S, but the reasons for this disparity are unknown. The increasing incidence in the US is associated with the rise in hepatitis C virus (HCV) infection [2]. It is estimated that 3.2 million people in this country are infected with HCV; a blood-borne disease linked to 12,000 US deaths a year [3]. Following an acute infection with HCV, the disease becomes chronic in about 80% of cases. After 20–30 years of chronic infection, 20-30% of patients develop liver cirrhosis, which leads to HCC in 80-90% of all cirrhotic livers [5]

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