LOSS OF HUMAN-LEUKOCYTE ANTIGEN EXPRESSION ON COLORECTAL TUMOR-CELL LINES - IMPLICATIONS FOR ANTITUMOR IMMUNITY AND IMMUNOTHERAPY

A system devised for tissue typing the human leukocyte antigen-A (HLA- A) locus from genomic DNA by the polymerase chain reaction (PCR) has b een used to investigate abnormalities of HLA expression in a panel of 30 cell lines derived from colorectal adenocarcinomas, by comparison o f the HLA-A locus genotype with surface expression of HLA. Eleven cell lines gave single HLA-A locus specificity on PCR typing, suggesting t hat loss of HLA alleles is a common abnormality. In one of these cell lines the loss of an HLA-A locus allele was confirmed by comparison wi th DNA from a lymphoblastoid B cell line derived from the same patient . In three cell lines, loss of expression of an HLA-A locus determinan t was observed in spite of the presence of the relevant allele in geno mic DNA. Three cell lines showed absent HLA expression associated with failure to expreSS beta2-microglobulin. These data indicate that at l east three independent mechanisms were involved in the loss of HLA exp ression on the colorectal tumor cell lines.