Snapshot of Supplementary Movie 1. The cytotoxicity of 5-FU (5 Fluorouracil), an agent targeting thymidylate synthase (TS), is greatest when TS activity is the lowest. Both message and protein are necessary precursors for TS enzyme activity. Average tumor size is the lowest between 2 and 6 Hours After Lights On (HALO) when TS message and protein are both present. TS activity rises modestly as tumor size increases. TS message then fades as TS protein persists, TS activity declines and tumor size decreases. TS activity then spikes followed by tumor size and TS activity recession with residual TS message and protein. Times of day associated with the lowest tumor cell enzyme activity are the times of day associated with greatest 5-FU tumor cell anticancer activity. Times of day associated with highest tumor cell TS activity correspond to times of day of greatest tumor cell resistance to the cytotoxic effects of 5-FU. Tumors can thereby be expected to be most resistant to 5-FU in the middle of the daily dark/activity span (18 HALO) and most sensitive to 5-FU in the middle of the daily light/sleep span.
