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

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.