The same external signal differentially induced the c-myc expression in Burkitt lymphoma and B-lymphoblastoid cell lines.

An extracellular signal, such as phorbol-12-myristate-13-acetate (PMA), was found to reduce the c-myc expression in Burkitt lymphoma (BL) cells but augment the expression of the same gene in a B-lymphoblastoid cell line (B-LCL). Studies with Epstein-Barr virus (EBV)-converted BL cells demonstrated that the differential effect of PMA on c-myc expression was not due to alterations in the structure of the translocated c-myc gene, but to the difference in the intracellular milieu of the B cells. Experiments on the degradation rate in c-myc RNA suggested that this phenomenon in c-myc expression was exerted, at least in part, at the transcriptional level.