Expression of myelin and lymphocyte protein (MAL) in oral carcinogenesis.

In the pathological diagnosis of oral squamous cell carcinoma, we often confront the difficulty of determining whether it is invasive carcinoma or epithelial dysplasia. Recently, myelin and lymphocyte protein (MAL; T-cell differentiation-related gene) has been reported to be a candidate gene suppressed in esophageal carcinoma. When we performed cDNA microarray analysis, we found that gene expression of MAL was significantly downregulated in oral squamous cell carcinoma (OSCC). We evaluated the expression of the MAL gene by laser microdissection and real-time PCR methods and protein localization by immunohistochemistry. The gene expression of MAL was significantly decreased in OSCC compared with normal epithelium (P < 0.05). Furthermore, protein expression of MAL disappeared gradually in proportion to malignancy. The results suggest that MAL plays an important role during oral carcinogenesis and that the gene may have potential as a biomarker target for OSCC.