Mutation in the beta 2m gene is not a frequent event in head and neck squamous cell carcinomas

In cryostat sections of 84 head and neck squamous cell carcinomas (HNSCC) H LA class I and beta 2m expression was analysed using monomorphic and locus specific monoclonal antibodies. Loss of expression was heterogeneous and no ne of the rumours test-ed showed a total loss of HLA class I and/or beta 2m when analysed with W6/32, which recognises HLA class I determinants and an ti-beta 2m MoAbs. Weak HLA class I and beta 2m expression was found in 9 ru mours (11%)and heterogeneous expression was found in 2 tumours (2%). When a nalysed with locus-specific antibodies (HCA2 and HC10, anti-HLA-A and anti- HLA-B/C, respectively) 37 rumours (44%) showed a loss, weak or heterogeneou s expression of one or both loci. Tumours showing a down-regulated HLA clas s I expression were analysed for mutations in either allele of the beta 2m gene by sequencing based mutation analysis (SBMA). Exon 1 and exons 2 and 3 were amplified separately by PCR using M13-tailed intron-specific primers. PCR products were sequenced in two directions. In none of the tumours muta tions in the beta 2m gene were detected. In 59% of the rumours with down-re gulated HLA class I expression, lost or down-regulated TAP 1 expression was found when analysed with anti-TAP 1 antibodies. This indicates an importan t role for TAP in down-regulation of HLA class I expression in HNSCC. (C) A merican Society for Histocompatibility and Immunogenetics, 1999 Published b y Elsevier Science Inc.