Differentially expressed serum haptoglobin alpha chain isoforms with potential application for diagnosis of head and neck cancer

Abstract

Background The discovery of molecular biomarkers is crucial to the diagnosis of head and neck squamous cell cancer (HNSCC). Methods Proteins from pre-surgery serum samples of patients with HNSCC and healthy individuals were analyzed by 2-dimensional gel electrophoresis (2-DE) using a 17 cm-long immobilized pH gradient gel strip (large gel). The differentially expressed protein spots were detected by statistical analysis. Because 2 haptoglobin (Hp) α chains were found to be differentially expressed, the genotypic distribution of Hp α chains in patients and healthy individuals was assayed by polymerase chain reaction. The protein expression levels of Hp α chains in individuals carrying different Hp alleles were analyzed by 2-DE with a small gel. Results Two isoforms of haptoglobin α2 chain (Hp α2) in patients' sera were found from 2-DE analysis to be up-regulated, while the isoforms of haptoglobin α1 chain (Hp α1) were significantly down-regulated. Apolipoprotein AII and 2 isoforms of apolipoprotein CII were also differentially expressed in the sera of patients with HNSCC. The Hp α2 chain was significantly up-regulated in the patients carrying at least one haptoglobin 2 allele, according to the spot intensities from scanned images of small-gel 2-DE. Conclusions The expression pattern of seven differentially expressed polypeptides and the up-regulation of Hp α2 in individuals with the Hp 2 allele are potential biomarkers.