REGULATION OF THE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I GENES IN HUMAN COLORECTAL-CANCER

Products encoded by the major histocompatibility complex class I genes are down-regulated in many tumors. The under-representation of HLA antigens in human tumors is usually associated with a poor prognosis. In this report, the expression of HLA genes in human colorectal carcinomas was studied using HLA-A and HLA-B locus-specific probes. Over 50% of the colorectal carcinomas studied showed a reduction in the amount of steady-state HLA mRNA. For some carcinomas, non-coordinated regulation of the HLA-A and HLA-B genes was observed. The HLA expression in some, but not all cases, could be enhanced by gamma-interferon. Over 60% of the colorectal carcinomas also expressed high level of the c-myc oncogene mRNA. However, no correlation could be made between the increase of c-myc expression and the down-regulation of the HLA genes.