EXPRESSION OF BETA-2-MICROGLOBULIN BY PREMALIGNANT EPITHELIUM

Many human tumors express low amounts of HLA class I molecules relativ e to the normal cells from which they are derived. From experimental w ork it is clear that the malignant behavior of a tumor cell may depend on its MHC class I expression. Therefore, it is of obvious interest t o study the HLA class I expression of human tumors in their various st ages. We have studied the HLA class I expression by the cells in prema lignant epithelial lesions and invasive carcinoma of the bladder and u terine cervix using immunoperoxidase staining for beta2-microglobulin of paraffin-embedded tissue. We here assume that beta2-microglobulin e xpression by malignant and premalignant cells equals HLA class I expre ssion. Thirty-two of the 36 invasive tumors expressed less overall bet a2-microglobulin than cells from the normal epithelium. In contrast, a pproximately two-thirds of 34 premalignant bladder epithelia and 47 pr emalignant cervix epithelia displayed higher overall beta2-microglobul in expression than the normal epithelium. Thus, a systematic large-sca le elimination of HLA class I high-expressing tumor cell variants may take place only after the tumor penetrates the basement membrane.