Unexpectedly, drastic reduction in SP phenotype (5.3%) was observed in ERK2-dn transfected melanoma cells but not in ERK1-dn cells (15.6%) (Fig. 7B, panel I and II) as compared to B16F10 cells treated with CM of B16-WT (19.4%) (Fig. 6E) suggested that ERK2 plays an important role in regulation of SP phenomena in B16F10 cells. The gene discussed is MAPK1; the disease is melanoma.