Efficient Recovery of HLA Class I Expression in Human Tumor Cells After Beta2‐Microglobulin Gene Transfer Using Adenoviral Vector: Implications for Cancer Immunotherapy

Here we report a successful use of a non-replicating adenovirus expressing the wild-type human β2m gene in recovery of normal human leucocyte antigen (HLA) class I expression in β2m-null cancer cells. Total loss of HLA class I expression in these cell lines is caused by a mutation in β2m gene and a loss of heterozygosity in chromosome 15 carrying another copy of that gene. Normal HLA class I expression on the tumour cell surface is critical for the successful outcome of cancer immunotherapy as T cells can only recognize tumour-derived peptides in a complex with self-HLA class I molecules. In this report we characterize the newly generated adenoviral vector AdCMVβ2m and demonstrate an efficient β2m gene transfer in tumour cell lines of different histological origin, including melanoma, prostate and colorectal carcinoma. The β2m re-expression lasted for an extended period of time both in vitro and in vivo in human tumour xenograft transplants. We propose that in a subset of cancer patients with structural defect in β2m gene or chromosome 15, the adenoviral-mediated recovery (or even increase) of HLA class I expression on tumour cells in combination with vaccination or adoptive T-cell therapy can provide a complementary approach to improve the clinical efficacy of cancer immunotherapy.