Expression of HLA class I and II antigens in bronchogenic carcinomas: its relationship to cellular DNA content and clinical-pathological parameters.

We studied the presence of HLA class I antigens in 115 samples of bronchogenic carcinomas (66 frozen and 49 formalin-fixed and paraffin-embedded specimens) by the immunophosphatase alkaline and immunoperoxidase methods with antibodies against major histocompatibility complex antigens. We also studied HLA class II antigens on the 66 frozen tumor samples. Nonneoplastic lung tissue was also analyzed for purposes of comparison. Pneumocytes and epithelial respiratory cells expressed HLA class I and II antigens. The expression of class I antigens was totally lost in 29 tumors (25%). The defect in HLA gene expression affected both heavy chain and beta 2-microglobulin, as demonstrated by the null reactivity with specific antibodies. In 2 cases of 66 studied in cryostatic section, the selective loss of A locus was observed, and in three cases selective loss of B locus was detected. The expression of class I antigens was compared with clinical-pathological parameters such as histological type, degree of differentiation, and tumor stage, as well as tumoral ploidy. The absence of expression of HLA class I molecules was significantly associated with poorly differentiated and undifferentiated tumors (P less than 0.0001) and with aneuploid tumors (P less than 0.001), suggesting that some lung tumors may escape immune surveillance and become biologically more aggressive. Class II antigens were expressed in 13 cases of 66 studied (18%) in frozen specimens, and a clear relationship was observed with well-differentiated tumors (P less than 0.05).