Dissociation of thymidine incorporation and transferrin receptor expression from cell growth and c-myc accumulation in alpha-interferon-treated cells.

Alpha-interferon is capable of altering the pattern of growth of both normal and neoplastic cells, but the pathways essential to sensitivity and resistance to alpha-interferon are unknown. To explore the growth inhibition induced by alpha-interferon, we examined the interferon-sensitive cell line Daudi and the resistant cell line HL-60. In Daudi, alpha-interferon induced a fall in c-myc mRNA accumulation at 24 h, inhibited tritiated thymidine ([3H]Thd) uptake at 48-72 h, and inhibited proliferation at 72-96 h. The half-life of c-myc mRNA was shortened from 31 to 13 min by alpha-interferon treatment. In HL-60, no alteration in c-myc accumulation or cell growth was observed, but [3H]Thd uptake was inhibited by 49%. Exogenous thymidine partially reversed the effects of alpha-interferon on [3H]Thd incorporation. The number of transferrin receptors, as measured by immunofluorescence, was unaffected by alpha-interferon in both cell lines. We conclude that the growth inhibitory effects of alpha-interferon are neither dependent upon inhibition of thymidine metabolism nor on expression of the transferrin receptor, but may be linked to control of c-myc.