Downregulation of HLA Class I Molecules in Primary Oral Squamous Cell Carcinomas and Cell Lines

Background and AimsLoss or downregulation of human leukocyte antigen (HLA) class I expression has been reported in a variety of human tumors including oral squamous cell carcinoma (OSCC).MethodsExpression of HLA class I molecules were evaluated by immunohistochemistry, flow cytometry, semi-quantitative Western blot and RT-PCR in 43 tissue samples of primary oral squamous cell carcinomas (pOSCC) from Chinese patients and two OSCC cell lines.ResultsHLA class I heavy chain of B/C locus and A locus and β2-microglobulin were obviously lost or downregulated in pOSCC with the percentage of 31, 55 and 35% respectively. The expression of HLA B/C, LMP2, LMP7, LMP10 and PA28β in OSCC cell lines was also presumably reduced in comparison with normal epithelial cell line.ConclusionsThese data suggested that the downregulation of HLA class I molecules in OSCC was closely associated with the low–efficient transcription and abnormality of post-transcription regulation of HLA class I genes and antigen presentation-related genes. These results can add more light to the mechanism by which OSCC escape from immunological surveillance.