INVITRO DIFFERENTIATION OF HUMAN-MELANOMA CELLS ANALYZED WITH MONOCLONAL-ANTIBODIES

Abstract

Many monoclonal antibodies (MAB) have been produced against cell surface molecules of melanoma cells and these reagents might help in the definition of stages of differentiation of the normal and the malignant cells. In an attempt to detect MAB-defined determinants that modulate with differentiation, nonpigmented human melanoma cells were treated with the tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA) at 16 nM. Differentiation could be induced in all 4 cell lines [Mel-Juso, Mel-Im, Mel-Wei and Mel-Ei], as evidenced by growth retardation, development of projections and induction of melanin or of premelanosomes in the projections as detected by transmission electron microscopy. Of the 9 MAB-defined cell surface antigens, 3 were shown to modulate with TPA-induced differentiation, as assessed by fluorescence microscopy and fluorescence-activated cell sorter analysis. Antigens detected by MAB 15.75 and 15.95 decreased in every 1 of the 4 cells after TPA induction of differentiation. The proteoglycan defined by 225.28S increased slightly in 1, showed no change in another and decreased in the remaining 2. These 3 MAB-defined molecules thus are linked to differentiation and might help in designing a scheme of differentiation of the melanocyte lineage.