Chronic jet lag alters growth rate of carcinogen (MCA)-induced tumors and time-dependent anticancer activity of PD-0332991 in mice.

(A) The experimental schedule for chronic jet lag and palbociclib (PD-0332991) drug treatment. Thirty to sixty days after subcutaneous injection of MCA in mice, the mice were separated into Control and Jet-lag groups for a chronic jet-lag schedule, as depicted. Red arrows indicate sampling of the tumor and liver tissues from both groups of mice killed at the time points (ZT3, ZT9, ZT15) as indicated for further western blot analysis (See Fig 4D). Black arrowheads denote times of tumor measurement. Orange and green arrows indicate oral drug administration of mice at ZT3 and ZT15. Treatment started on day 11 after chronic jet lag (CJL). (B) Representative activity records of running wheel activity in Control and Jet-lag mice. (C) Plots depicting tumor growth in Control (grey circle, n = 14) and Jet-lag (brown circle, n = 14) mice during CJL. **p p n = 3 independent experiments. Error bar shown with mean ± SEM. (D) Quantification of relative tumor growth rate calculated from linear regression by fitting a linear equation to observed data in the Control (n = 14; grey circle) and Jet lag (n = 14; brown circle) mice of (C). ***p t test. Data normalized were shown with mean ± SEM; n = 14 in both groups. (E and F) Time-dependent effects of palbociclib on MCA-induced tumor growth in Control (E) or Jet-lag (F) mice. Tumor growth changed as a function of palbociclib administration time: untreated (black circle), treated at ZT3 (orange square), and treated at ZT15 (green triangle). n indicates the number of mice analyzed. Data normalized were shown with mean ± SEM; n = 5–6 per group. The result is representative of two independent experiments. (G and F) Quantification of MCA-induced tumor growth rate calculated from linear regression by fitting a linear equation to observed data in Control (G) or Jet-lag mice (F) under the different drug treatment conditions: untreated (black circle), treated at ZT3 (orange squares), and treated at ZT15 (green triangles). n = 5–6 mice were analyzed in all groups. *p S3 Data. CJL, chronic jet lag; DD, constant darkness; LD, light-dark; MCA, methylcholanthrene; n.s., not significant; ZT, zeitgeber time.