Distribution of HLA class I altered phenotypes in colorectal carcinomas: high frequency of HLA haplotype loss associated with loss of heterozygosity in chromosome region 6p21.
HLA class I loss or down-regulation is a widespread mechanism used by tumor cells to avoid tumor recognition by cytotoxic T lymphocytes, and thus favor tumor immune escape. Multiple mechanisms are responsible for these HLA class I alterations. In different epithelial tumors, loss of heterozygosity (LOH) at chromosome region 6p21.3, leading to HLA haplotype loss, occurs in 6-50% of all cases depending on the tumor entity. In this paper we report the frequency of LOH at 6p21 in 95 colorectal carcinomas (CRC) previously analyzed for altered HLA class I expression with immunohistological techniques. We used PCR microsatellite amplification of selected STR markers located on Chromosome 6 to identify LOH with DNA from microdissected tumor tissues and the surrounding stroma. Sequence-specific oligonucleotide analysis was performed in microdissected stroma and tumor cells for HLA typing, and to detect HLA haplotype loss. A high frequency (40%) of HLA haplotype loss was found in CRC. Eight tumors showed microsatellite instability. We sometimes observed two or more mechanisms responsible for HLA alteration within the same HLA-altered phenotype, such as LOH and HLA class I total loss. In 25 tumors (26%) no HLA class I alteration could be identified. These data are potentially relevant for CRC patients undergoing T-cell-based immunotherapy.
Maleno
Isabel
I
Servicio de Análisis Clínicos, Hospital Universitario Virgen de las Nieves, Avd. Fuerzas Armadas 2, 18014 Granada, Spain.
Cabrera
Carmen Maria
CM
Cabrera
Teresa
T
Paco
Laura
L
López-Nevot
Miguel Angel
MA
Collado
Antonia
A
Ferrón
Antonio
A
Garrido
Federico
F
D002896:Chromosomes, Human, Pair 6 / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000276:immunology; D015972:Gene Expression Regulation, Neoplastic; D005787:Gene Frequency; D005805:Genes, MHC Class I; D006680:HLA Antigens / Q000032:analysis*; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D019656:Loss of Heterozygosity; D018895:Microsatellite Repeats; D010641:Phenotype
D006680:HLA Antigens