CLASS-I MAJOR HISTOCOMPATIBILITY COMPLEX ANTIGENS AND TUMOR PLOIDY INBREAST AND BRONCHOGENIC CARCINOMAS

We determined the frequency of expression of the major histocompatibil ity complex antigens HLA-A,B,C, in tumor cells from 207 primary tumor lesions of breast and bronchogenic carcinomas, to see if the expressio n of theses antigens was Linked with several clinical pathological par ameters associated with tumor aggressivity, such as abnormal cellular DNA content. We compared tumor tissues with nonneoplastic tissues and tissues from 15 benign breast lesions. HLA class I expressor and nonex pressor tumor cells were determined by using immunohistochemical stain s CPAP and APAAP methods) and antibodies against these antigens. Reduc tion of HLA class I antigen was detected in 65 tumors (31.7%) and was significantly associated with poor tumor differentiation and abnormal cellular DNA content (p < 0.001). These characteristics might define a group of aggressive tumors in which the decrease of HLA class I antig ens would enable tumor cells to avoid eliciting host immune responses. On the other hand, the altered regulatory mechanisms, of tumors with abnormal cellular DNA content, might modulate the expression of HLA cl ass I molecules.