Loss of Heterozygosity at 6p21 and HLA Class I Expression in Esophageal Squamous Cell Carcinomas in China

Background and objective: The loss or downregulation of human leukocyte antigen ( HLA-Ⅰ) has been proposed to contribute to immune evasion by cancer cells. Since the human leukocyte antigen (HLA-Ⅰ) complex is located at 6p21.3, loss of heterozygosity of this region may alter HLA class Ⅰ tumor phenotypes. The aim of this study was to analysis loss of heterozygosity (LOH) of chromosome 6p in ESCC samples and correlate this with HLA class I expression. Materials and methods: A total of 87 formalin-fixed, paraffin-embeded and frozen-fresh of ECSS lesions were collected. HLA-Ⅰand antigen-processing machinery component expression was investigated by immunohistochemistry with anti-HLA classⅠ monoclonal antibody and a panel of 49 ESCCs with downregulated HLA class Ⅰ expression wereselected for LOH studies using 3 microsatellite markers located at 6p21.3 (D6S105,D6S265,D6S273).
Results: HLA-Ⅰantigen,TAP1 and LMP were lost or down-regulated in 57.5, 29.8 and 47.0% of the ESCC lesions, respectively. In 23/49(46.9%) of the ESCCs, allelic loss for at least one locus at 6p21.3 was found.
Conclusions: Our data show that downregulation of HLA class I expression is correlated with loss of heterozygosity regions at 6p21.3 in ESCC.