The invention provides processes and compositions for enhancing the immunogenicity of TAP-1 expression-deficient cells by increasing the presentation of MHC Class 1 surface molecules for detection by cytotoxic T-lymphocyte cells through increased TAP-1 expression, which comprises administering to the TAP-1 expression-deficient cells a TAP-1 expression increasing amount of a bio-acceptable substance that promotes transcription of TAP-1 gene in the cells to cause enhanced MHC Class 1 surface expression of the cells. The bio-acceptable substance may be a histone H3 deacetylase inhibitor such as trichostatin A, a transcriptional co-activator having intrinsic histone acetyl transferase activity or a histone acetyl transferase comprising at least one member of the CBP/p300 protein family. The process and compositions increase the immunogenicity of the target cells, e.g. tumor cells, to enhance their destruction by cytotoxic lymphocytes.
