Identification and validation of metastasis-associated proteins in head and neck cancer cell lines by two-dimensional electrophoresis and mass spectrometry.

Despite improvements in treatment of patients with head and neck squamous cell carcinoma (HNSCC) over the last two decades, the survival rate of these patients has not increased significantly. One of the major factors in the poor outcome of the disease is regional metastasis. To better understand the mechanisms of this process at the protein level, we performed two-dimensional electrophoresis (2-DE) and mass spectrometry using SELDI ProteinChip technology to identify proteins differentially expressed in two HNSCC cell lines, UMSCC10A and UMSCC10B, from the same patient. UMSCC10A was derived from the primary tumor and UMSCC10B from a metastatic lymph node. The differentially expressed proteins were excised from the gels. Following in-gel digestion by trypsin, mass profiles of the peptides were generated. Proteins were identified by submitting the peptide mass profiles to a public available NCBInr databases (www.proteometrics.com). Two membrane-associated proteins, annexin I and annexin II and glycolytic protein enolase-alpha were found to be upregulated, and calumenin precursor down-regulated, in metastatic cell line UMSCC10B. The identity of these proteins was confirmed by analyzing additional peptide mass fingerprints obtained by endoproteinase lysine-C digestion. The results were also validated by Western blotting analysis. Our results showed that enolase-alpha, annexin-I and annexin-II might be important molecules in head and neck cancer invasion and metastasis. The results also suggest an important complementary role for proteomics in identification of molecular abnormalities important in cancer development and progression.