Up-regulation of neutrophil gelatinase-associated lipocalin in oral squamous cell carcinoma: Relation to cell differentiation

Neutrophil gelatinase-associated lipocalin (NGAL, also known as lipocalin2, LCN2) is a secreted glycoprotein with increased expression in solid tumors. The expression and functions of NGAL in oral cancer, however, remain unclear. We investigated the expression of NGAL in oral cancer tissues and oral cancer cell lines. By immunohistochemical examinations, NGAL expression was strongly up-regulated in well-differentiated OSCC tissues and moderately to weakly up-regulated in moderately to poorly differentiated OSCC tissues. In contrast, NGAL expression was weak or very weak in normal mucosa and leukoplakia. By western blot analysis, NGAL expression levels positively correlated with cell morphology patterns and loss of E-cadherin. In addition, the enzymatic activity of the NGAL/MMP-9 complex significantly correlated with the results obtained by zymographic analysis. In conclusion, NGAL expression is high in well-differentiated cancer, suggesting that NGAL may be a useful diagnostic marker of tumor-cell differentiation.