Effects of interferon on differentiation of normal and tumor cells.

As described in this review, both partially purified and recombinant interferons are potent modulators of differentiation in diverse cell culture systems (Table 2). Depending on the target cell, interferon exerts either an inhibitory or an inductive effect on cell differentiation. In certain myeloid leukemic cells, such as HL-60, interferon by itself is growth suppressive but does not induce cell maturation, whereas in combination with inducers of differentiation, such as DMSO, TPA or retinoic acid, interferon potentiates their ability to stimulate differentiation in both sensitive and resistant cell populations (Grant et al., 1982, 1983; Tomida et al., 1982). Interferon also interacts synergistically with phorbol ester tumor promoters in inhibiting melanogenesis in murine B-16 cells (Fisher et al., 1981a, 1984a) and adipocyte formation in 3T3 cells (Cioe et al., 1980), whereas the combination is synergistic in inducing differentiation in human melanoma cells (Fisher et al., 1984b,c). In contrast, interferon and TPA display antagonistic effects on differentiation in human skeletal muscle cultures, i.e. interferon induces and TPA inhibits myogenesis (Fisher et al., 1982, 1983). Recent studies have demonstrated the presence of high affinity saturable cell membrane receptors for mouse and human interferons (Aguet, 1980; Branca and Baglioni, 1981, 1982; Mogensen et al., 1981; Branca et al., 1982; Anderson et al., 1982; Joshi et al., 1982; Faltynek et al., 1983; Yonehara et al., 1983; Langer and Pestka, in preparation). Similarly, specific membrane receptors have been identified for phorbol esters and mezerein (Driedger and Blumberg, 1980; Shoyab and Todaro, 1980; Horowitz et al., 1981; Fisher et al., 1981b). These findings suggest that the plasma membrane may be a primary target for mediating the biochemical effects induced by both interferon and phorbol esters. Although the mechanism by which interferon and phorbol esters transmit the necessary membrane signal(s) required for altering differentiation are not known, a possible component of this transmembrane signaling process may involve changes in the physical dynamics of the plasma membrane. It is therefore of interest that both interferon and TPA induce early changes in the fluidity of the plasma membrane (Fisher et al., 1979, 1981b, 1984d; Castagna et al., 1979; Kuhry et al., 1983).(ABSTRACT TRUNCATED AT 400 WORDS)