THE phorbol diester, 12-0-tetradecanoylphorbol-

other tumour promoters affect cells in culture at various levels and in a variety of ways (Slaga et al., 1978). It is now increasingly appreciated that tumour promoters can affect mononuclear phagocytes at different levels and with opposite consequences: (1) precursors of the mononuclear phagocyte lineage are selectively stimulated to proliferate and differentiate into macrophages, thus mimicking…