Over‐expression of c‐myc increases the sensitivity of epstein‐barr virus immortalized lymphoblastoid cells to non‐MHC‐restricted cytotoxicity

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Abstract
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), interferonactivated (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‐myctransfected 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.