Rhythmic Control of the ARF-MDM2 Pathway by ATF4 Underlies Circadian Accumulation of p53 in Malignant Cells

Michiko Horiguchi,Chikamasa Yamashita,Ahmed M Hamdan,Keisuke Kakimoto,Satoru Koyanagi,Naoya Matsunaga,Shigehiro Ohdo

doi:10.1158/0008-5472.can-12-2492

Michiko Horiguchi, Chikamasa Yamashita + Show 5 more

Open Access

https://doi.org/10.1158/0008-5472.can-12-2492

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Abstract

The sensitivity of cancer cells to chemotherapeutic agents varies according to circadian time. Most chemotherapeutic agents ultimately cause cell death through cell-intrinsic pathways as an indirect consequence of DNA damage. The p53 tumor suppressor gene (TRP53) configures the cell deaths induced by chemotherapeutic agents. In this study, we show that the transcription factor ATF4, a component of the mammalian circadian clock, functions in circadian accumulation of p53 protein in tumor cells. In murine fibroblast tumor cells, ATF4 induced the circadian expression of p19ARF (Cdkn2a). Oscillation of p19ARF interacted in a time-dependent manner with MDM2, a specific ubiquitin ligase of p53, resulting in a rhythmic prevention of its degradation by MDM2. Consequently, the half-life of p53 protein varied in a circadian time-dependent manner without variation in mRNA levels. The p53 protein accumulated during those times when the p19ARF-MDM2 interaction was facilitated. Notably, the ability of the p53 degradation inhibitor nutlin-3 to kill murine fibroblast tumor cells was enhanced when the drug was administered at those times of day during which p53 had accumulated. Taken together, these results suggested that ATF4-mediated regulation of the p19ARF-MDM2 pathway underlies the circadian accumulation of p53 protein in malignant cells. Furthermore, they suggest an explanation for how the sensitivity of cancer cells to chemotherapeutic agents is enhanced at those times of day when p53 protein has accumulated, as a result of circadian processes controlled by ATF4.

Highlights

Rhythmic variations in biological functions are thought to affect the efficacy and/or toxicity of drugs: the potency of a large number of drugs varies depending on the time of day when the drugs are administered [1]
To investigate the possibility that ATF4 regulates the expression of p53 protein at posttranscriptional level, we explored the stability of p53 protein in ATF4-downregulated tumor cells
The half-life of p53 protein in Atf4À/À tumor cells was considerably longer than that from wild-type cells, but the time of preparation did not cause significant differences in the half-life of p53 protein in Atf4À/À tumor cells (Fig. 3B). These results suggest that circadian accumulation of p53 protein in wildtype tumor cells is associated with the time-dependent change in its stability; the circadian change in that stability is caused by ATF4

Summary

Introduction

Rhythmic variations in biological functions are thought to affect the efficacy and/or toxicity of drugs: the potency of a large number of drugs varies depending on the time of day when the drugs are administered [1]. It has been suggested that administering drugs at appropriate times of day can improve the outcome of pharmacotherapy by maximizing potency and minimizing the toxicity of the drug, whereas administering them at inappropriate times of day can induce severe side effects [2]. A chronopharmacological strategy can improve tumor response, overall survival, and dose-limiting toxicity in cancer patients who are subjects in ongoing prospective randomized clinical trials. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/).

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