Fig. 1.

B16 melanoma tumor volumes decrease with increasing age in an implantation site and strain-dependent manner. (A) Cohorts of C57BL/6 (B6) mice, with 12 animals in each age group, were implanted with 5×10⁵ cells in the subcutaneous axillary and inguinal areas and terminated 14 days later. Average tumor volume was higher at the inguinal site compared to the axillary site in 8-month-old mice (p≤0.05), and was significantly lower at 32 months at both sites (p≤0.001). (B) The experimental procedures and cohort numbers were the same for C57BL/6×BALB/c F1 (CB6 F1) mice but with lower average tumor volumes than B6 mice at 8 months of age at both implantation sites. An age-related decrease occurred only from 16 to 24 months of age at both sites (p≤0.05). (C) Intradermal melanoma implants, with the same cell number and eight mice in each age group for both mouse strains, resulted in average tumor volumes that were similar for both strains at 8 months of age, but with a significant decrease in average tumor volume at 16 months and again at 24 months for CB6 F1 mice (p≤0.005). Average tumor volumes did not decrease until 32 months for B6 mice (p≤0.01).