Recovery HLA-A2 and Beta2-microglobulin Expression in Tumor Cells Using Viral Vectors

Abstract

Background: Tumor elimination and the success of cancer immunotherapy depend on the proper expression of HLA class I complex (HLA-I) required for the presentation of tumor-associated peptides to cytotoxic T-lymphocytes. Tumors escape immune attack by losing HLA-I expression, often due to irreversible genetic/chromosomal alterations, including mutations in beta2-microglobulin (B2M) or lack of HLA-A2 allele due to a haplotype loss. The introduction of these genes and re-expression of the missing HLA-I specificity on the tumor cell surface is an attractive strategy to induce tumor rejection by T-lymphocytes. Methods: Using genomic HLA-I typing and gene sequencing we determined HLA-I phenotypes and alterations in different human tumor cell lines previously characterized in our laboratory. We used adeno- and adeno-associated viruses to reconstitute/up-regulate HLA-A2 or/and B2M expression in these cells in vitro. Using flow cytometry and immunocytochemistry we evaluated levels and patterns of HLA-I expression in these cells. Methods: Using genomic HLA-I typing and gene sequencing we determined HLA-I phenotypes and alterations in different human tumor cell lines previously characterized in our laboratory. We used adeno- and adeno-associated viruses to reconstitute/up-regulate HLA-A2 or/and B2M expression in these cells in vitro. Using flow cytometry and immunocytochemistry we evaluated levels and patterns of HLA-I expression in these cells. Conclusion: Using gene therapy, it is possible to recover normal B2M and HLA-A2 gene expression caused by structural “hard” alteration and to induce co-expression of both genes in cells naturally lacking HLA-A2 allele. In addition, we demonstrated that transfected tumor cells ae able to express seven HLA-I alleles. The recovery of the missing HLA-I molecules frequently observed in tumor cells using adeno and adeno-associated viruses can be a useful strategy to circumvent cancer immune escape and increase tumor rejection.