Lack of MHC class I antigens and tumour aggressiveness of the squamous cell carcinoma of the larynx

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Abstract
A series of 60 primary laryngeal and hypopharyngeal tumours, 24 lymph node metastases and normal tissue were evaluated in frozen sections for the expression of MHC class I antigens, using monoclonal antibodies and the APAAP technique. We found 13 tumours presenting total HLA-ABC loss, five with selective loss of HLA-A antigens and one with absence of HLA-B antigens. These losses were statistically associated with clinical and pathological parameters, such as T stage, degree of differentiation, scores according to the Jakobsson and Glanz grading systems and degree of leukocytic infiltration. Our results lead us to the following conclusions: (a) HLA class I losses were found in a group of tumours showing greater aggressiveness and worse prognosis; (b) these alterations in expression were not associated with an increased metastatic potential. Thus, the absence of HLA molecules in laryngeal tumours is related to greater local aggressiveness, and the loss of class I antigens seems to constitute an adaptive tumour mechanism to avoid the different anatomical and immunological barriers within the larynx.