MKI67 and melanoma: The proliferative activity of the B12F10 melanoma cells, as assessed by Ki-67 staining, significantly decreased after treatment for 48 hours with both ST-91 (about −29%, p < 0.05 vs. CTR) and clonidine (CLO, about −24%, p < 0.05 vs. CTR) compared to control (Figure 2A–C).