A–C, Tumor images, volumes, and weights. B16 melanoma cells (5×105 cells/mouse) were inoculated s.c. into CCR5+/+ mice and CCR5−/− mice (n = 20). Tumor volumes were measured every day and tumor weights were measured at study termination (Day 31). The CCR5−/− mice had a significant reduction in tumor growth and volume as compared to CCR5+/+ mice. The results are expressed as mean ± SD. * indicates significant difference from CCR5+/+ mice (P<0.05). D, The CCR5−/− mice demonstrated significantly higher survival rates compared to CCR5+/+ mice (by Log-rank Test). E. Tumor sections were analyzed by H&E stain and expression of proliferating cell nuclear antigen (PCNA) by immunohistochemistry. Data are means ± S.D. of four experimental animals. * indicates significant difference from CCR5+/+ mice (P<0.05). Scale bar indicates 50 m.