Modulated expression of human leucocyte antigen class I and class II determinants in hyperplastic and malignant human prostatic epithelium.

OBJECTIVES

To determine whether human prostatic carcinoma cells express Class I and/or Class II major histocompatibility complex (MHC) determinants and whether they might thus be immune-competent targets for cell-mediated cytotoxicity.

MATERIALS AND METHODS

Immunohistochemistry, performed both before and after neuraminidase digestion, was employed to compare 13 benign prostatic hyperplasias with 42 primary and 44 metastatic prostatic carcinomas obtained from the United Kingdom and from the United States of America. Expression of beta 2-microglobulin was used as the marker of Class I and HLA-DR as the marker of Class II expression.

RESULTS

Before desialylation, Class I MHC determinants were expressed in all of the benign hyperplasias, in 26% of primary carcinomas and in 14% of lymph node metastases. Cells expressing Class II determinants were identified in 69% of benign hyperplasias and in 2% of primary carcinomas, but in none of the lymph node metastases. After desialylation. Class I determinants were expressed in 100% of benign hyperplasias. 59% of primary carcinomas and 34% of the lymph node metastases. Class II determinants were expressed in 100% of benign hyperplasias, but only 19% of primary carcinomas and 5% of the lymph node metastases. While more than 50% of epithelial cells in each of the benign hyperplasias expressed MHCs, < 5% of the tumour cell populations in the positive malignant tissues (primary and metastatic) expressed MHCs, even after neuraminidase digestion. No correlation was found between expression of Class I or Class II MHC and Gleason morphological grade.

CONCLUSIONS

Failure to express Class I and/or Class II MHC determinants is a common feature of the majority of human prostatic carcinoma cells. Absence of these recognition molecules may be associated with avoidance of immune-surveillance and contribute to the metastatic dissemination of this malignancy.