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 timedependent 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. Cancer Res; 73(8);

During next generation sequencing (NGS) analysis, many missense mutations were found in a well-known oncogene, many of which were variant of uncertain significance mutations. We recently treated an adult patient with pancreatoblastoma by chemotherapy. Using an NGS cancer panel, we found a previously unreported missense mutation in the 1835 codon of the adenomatous polyposis coli (APC) gene. We also found a heterogeneous mutation in the 1835 codon of the APC gene in the patient's germline by Sanger sequencing. Although this patient did not have a history of familial adenomatous polyposis, functional analysis suggested the R1835G mutant APC showed attenuated repression of Wnt/β-catenin signaling activity. This is the first report showing a novel APC missense mutation involved in the onset of adult pancreatoblastoma.

No abstract

No abstract