Annexin A2 localizes to the basal epithelial layer and is down-regulated in dysplasia and head and neck squamous cell carcinoma

Annexin A2 is a highly expressed gene with important roles in cell membrane physiology and is frequently dysregulated in cancer. The objective of this study was to determine the pattern of expression and prognostic significance of annexin A2 protein in head and neck squamous cell carcinoma. We assessed both quantitative changes and qualitative distribution of annexin A2 mRNA and protein expression in normal and diseased tissues by immunohistochemistry, immunofluorescence and in situ hybridization. Annexin A2 expression was confined to the basal and suprabasal cells of normal epithelium and the protein cellular location was consistently observed at the cell membrane. Expression levels correlated with histopathological grade, showing significant suppression in moderately and poorly differentiated tumours. We conclude that annexin A2 exhibits a characteristic pattern of expression, distinct from other annexins and suggestive of a cell-specific functional role. The marked reduction of annexin A2 in poorly differentiated tumours and dysplastic tissue is expected to result in a loss of function aimed at the coordination of membrane signalling enzyme complexes, actin polymerization and extracellular matrix proteolysis. The phenotypic consequences may become manifest in an alteration of epithelial tissue growth and remodelling with secondary influence on tumour development, progression and metastasis.