Over-expression of C-myc increases the sensitivity of Epstein-Barr virus immortalized lymphoblastoid cells to non-MHC-restricted cytotoxicity.

Epstein-Barr virus (EBV)-carrying Burkitt lymphoma (BL) lines which maintain the phenotypic characteristics of the in vivo tumor cells are more sensitive to natural (NK), interferon-activated (IAK) and IL-2-activated (LAK) cytotoxicity than EBV-immortalized lymphoblastoid cell lines (LCL) of normal B-cell origin. All BL cells carry chromosomal translocations which lead to deregulated expression of the c-myc oncogene. LCLs transfected with constitutively active c-myc alleles display changes in growth properties and surface phenotype. In this study, we have examined the effect of c-myc deregulation on the sensitivity of LCLs to NK, IAK and LAK effectors. C-myc-transfected LCLs showed an increased sensitivity to lysis which correlated with the level of c-myc expression. Expression of HLA class I and sensitivity to allospecific and EBV-specific cytotoxic T-lymphocytes (CTL) remained unchanged. Transfection of a constitutively active v-H-ras gene, which also induces changes in growth properties and cell-surface phenotype, did not alter the sensitivity of LCLs to NK or LAK cytotoxicity.