Figure 2.

Negative control experiments to determine specificity of binding of melanoma cells to melanotropin-conjugated beads. (A) Blockade of binding of human A375P melanoma cells with MSH beads (microspheres) due to pretreatment of cells with an unconjugated (free) MSH ligand, [Nle-4,d-Phe-7]-α-MSH. (Bar = 10 μm.) (B) Naive (no MSH present) microspheres fail to bind to B-16 mouse melanoma cells. (Bar = 10 μm.) (C) Substance P-conjugated beads (macrospheres) do not bind to B16 mouse melanoma cells. (Bar = 100 μm.) (D) MCF-7 breast cancer cells do not bind to MSH-conjugated microspheres. (Bar = 10 μm.)