“…Retinoids modulate the growth and dierentiation of both myeloid and epithelial cells in vitro (Breitmann et al, 1980;Drach et al, 1993;Amos et al, 1989;Abemayor et al, 1989). In combination with various cytokines, ATRA shows a synergistic activity for dierentiation of hematopoietic cells (Hemmi et al, 1987;Trincheiri et al, 1987;Tobler et al, 1987;Peck et al, 1991), but the mechanism by which they synergize is not understood. RA have been shown to modulate the receptors for a number of dierent cytokines (Kilian et al, 1988;Sidell et al, 1988;Falk et al, 1991;Jetten et al, 1980;Winzen et al, 1992;Lotan et al, 1992;Sidell et al, 1991;Zheng et al, 1990).…”