Figure 2. Impact of circadian clock on the molecular dynamics of DNA damage response to cisplatin treatment in the B16F10 melanoma mouse model.

(A) Timeline for the study. C57BL/6 wild-type (WT) and Per1/2^−/− mice were maintained under a LD12:12 cycle and injected (s.c.) with 0.2 million B16F10 melanoma cells. When tumor sizes reached an average of 200 mm³, intraperitoneal cisplatin treatments of 5 mg/kg (twice) were administered either in the morning (7 AM, ZT0) or evening (7 PM, ZT12). Total body weights were measured every 2 days and reported as percent change (B) in wild-type and Per1/2^−/− mice. Mice were sacrificed when tumors crossed 4 times the volume at the start of treatment. Protein levels in response to DNA damage in the kidneys were detected by immunoblotting at selected time points post-cisplatin treatment in non-tumor (C) and tumor-bearing (D) mice. “S” indicates saline treatment, “AM, PM” indicate the times of cisplatin treatment, “2, 48, and 96” refer to the hours post-cisplatin treatment of tissue collection, and day 16 tissues in (D) were collected at 7 PM (ZT12). Statistical analysis was done using two-way ANOVA with Tukey's multiple comparison test for post-hoc testing relative to saline. n=5-7 mice per group. ^*=p<0.05, ^**=p<0.01, ^***=p<0.001, ^****=p<0.0001. Error bars = S.E.M.