Figure 4. STAT3 activation is required for the acquisition of the tumorigenic phenotype of melanoma cells.

(A-B) 501mel cells, transfected with a control (siC) or STAT3 siRNA, were left untreated or treated with recombinant IL6 (20 ng/ml) for 48 hrs and next were seeded on the filter of the upper compartment non coated (migration) or coated (invasion) with matrigel. DMEM with 7% serum were added to the lower compartment of Boyden chambers. Cells that had migrated to the underside of the upper compartment were stained 24 hrs later with crystal violet and the number of nuclei was counted using NIH-imageJ analysis software. Values represent mean +SD of three independent experiments, significantly different from the control ***p<0.001 and ** p<0.01. (C) 501mel cells, transfected with control (siC) or STAT3 siRNA were exposed to secretome of control melanoma cells (C), IL6 (20 ng/ml) or to the SSMC for 48 hrs and then subject to a cell viability assay. (D) 501mel melanoma cells treated as in (C) were subcutaneously injected in athymic nude mice. Values are expressed as mean ±SEM.