The pro-longevity gene FoxO3 is a direct target of the p53 tumor suppressor

Department of Genetics, Stanford University, Stanford, CA 94305, USA.
Oncogene (Impact Factor: 8.46). 03/2011; 30(29):3207-21. DOI: 10.1038/onc.2011.35
Source: PubMed


FoxO transcription factors have a conserved role in longevity, and act as tissue-specific tumor suppressors in mammals. Several nodes of interaction have been identified between FoxO transcription factors and p53, a major tumor suppressor in humans and mice. However, the extent and importance of the functional interaction between FoxO and p53 have not been fully explored. Here, we show that p53 regulates the expression of FoxO3, one of the four mammalian FoxO genes, in response to DNA damaging agents in both mouse embryonic fibroblasts and thymocytes. We find that p53 transactivates FoxO3 in cells by binding to a site in the second intron of the FoxO3 gene, a genomic region recently found to be associated with extreme longevity in humans. While FoxO3 is not necessary for p53-dependent cell cycle arrest, FoxO3 appears to modulate p53-dependent apoptosis. We also find that FoxO3 loss does not interact with p53 loss for tumor development in vivo, although the tumor spectrum of p53-deficient mice appears to be affected by FoxO3 loss. Our findings indicate that FoxO3 is a p53 target gene, and suggest that FoxO3 and p53 are part of a regulatory transcriptional network that may have an important role during aging and cancer.

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    • "This result was to some extent expected, as several lines of evidence have shown that the formation of a SMAD-FOXO3a complex is required for the TGFb-mediated antiproliferative effects in epithelial cells (Gomis et al., 2006; Seoane et al., 2004). Moreover, it has been demonstrated that FOXO3a, a direct transcriptional target of p53 (Renault et al., 2011), may be necessary Table 2 Relation of genes differentially expressed in Vero cells after a 24 h exposure to Mix 100 combination and its individual components. Data represent relative expression of test vs. control samples (Log 2 Cy5/Cy3 ratio) after removing background and normalizing with LOWESS upon calibrators. "
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    ABSTRACT: Butylated hydroxyanisole and propylparaben are phenolic preservatives commonly used in food, pharmaceutical and personal care products. Both chemicals have been subjected to extensive toxicological studies, due to the growing concern regarding their possible impacts on environmental and human health. However, the cytotoxicity and underlying mechanisms of co-exposure to these compounds have not been explored. In this study, a set of relevant cytotoxicity endpoints including cell viability and proliferation, oxidative stress, DNA damage and gene expression changes were analyzed to assess whether the antioxidant butylated hydroxyanisole could prevent the pro-oxidant effects caused by propylparaben in Vero cells. We demonstrated that binary mixtures of both chemicals induce greater cytotoxic effects than those reported after single exposureto each compound. Simultaneous treatment with butylated hydroxyanisole and propylparaben caused G0/G1 cell cycle arrest as a result of enhanced generation of oxidative stress and DNA double strand breaks. DNA microarray analysis revealed that a cross-talk between transforming growth factor beta (TGFβ) and ataxia-telangiectasia mutated kinase (ATM) pathways regulates the response of Vero cells to the tested compounds in binary mixture. Our findings indicate that butylated hydroxyanisole potentiates the pro-oxidant effects of propylparaben in cultured mammalian cells and provide useful information for their safety assessment.
    Food and Chemical Toxicology 07/2014; 72. DOI:10.1016/j.fct.2014.07.031 · 2.90 Impact Factor
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    • "Consistent with our report, other studies found that FOXO3a was a p53 target gene and that transcriptional activity of FOXO3a was regulated by p53, while the latter was not affected by FOXO3a (33,34). The p53 and FOXO3a formed part of regulation transcriptional network to control cancer cell growth and apoptosis (33,34). In addition, curcumin induced expression of p53 or/and FOXO3a in inhibition of cancer cell growth and other functions have been shown in other cell systems (27,28,35,36). "
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    ABSTRACT: Curcumin, one of the main bioactive components extracted from a traditional Chinese medicinal herb, exhibits potent anticancer activity against many types of cancer cells including nasopharyngeal carcinoma (NPC). However, the detailed molecular mechanism underlying this is not clearly understood. In this study, we showed that curcumin significantly inhibited the growth of NPC cells in a dose- and time-dependent manner as determined by MTT assays, while increasing apoptosis was also observed as measured by flow cytometry for the FITC-Annexin V and propidium iodide (PI) label and Hoechst 33258 staining. To further explore the potential mechanism, we showed that curcumin increased the phosphorylation of ERK1/2 but not p38 MAPK in a time-dependent manner, and induced protein expression of the tumor suppressors FOXO3a and p53 in a dose‑dependent manner, which were not observed in the presence of PD98059, an inhibitor of ERK1/2. Furthermore, silencing of FOXO3a and p53 genes by siRNAs overcame the inhibitory effect of curcumin on cell proliferation. Silencing or blockade of p53 using siRNA or chemical inhibitor abrogated the effect of curcumin on expression of FOXO3a protein; silencing or overexpression of FOXO3a had no further effect on curcumin-induced p53 protein expression. Furthermore, blockade of ERK1/2 and exogenous expression of FOXO3a restored the effect of curcumin on growth of cells. Together, our studies show that curcumin inhibits growth and induces apoptosis of NPC cells through ERK1/2-mediated increase in the protein expression and interaction of p53 and FOXO3a. p53 is upstream of FOXO3a, which form a regulatory loop that mediates the effect of curcumin. This study unveils a new mechanism by which curcumin inhibits the proliferation and induces apoptosis of human NPC cells.
    International Journal of Oncology 05/2014; 45(1). DOI:10.3892/ijo.2014.2420 · 3.03 Impact Factor
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    • "The cyclin-dependent kinase inhibitors p21 (CIP1/WAF1) has been shown to be involved in the cell cycle control, DNA replication, cell differentiation and apoptosis [14]. Studies demonstrated the link of p53, FOXO3a and p21 signaling in control of cancer cell growth [15-17]. However, the detailed mechanism by these interactions is still inconclusive. "
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    ABSTRACT: Berberine (BBR), a component from traditional Chinese medicine, has been shown to possess anti-tumor activity against a wide spectrum of cancer cells including human lung cancer, but the detailed mechanism underlining this has not been well elucidated. In this study, the effect of berberine on cell growth and apoptosis were assessed by MTT, flow cytometry and Hoechst 33258 staining assays. The phosphorylation of p38 MAPK and ERK1/2, and expressions of p38 MAPK isoforms alpha and beta, total ERK1/2, p53, FOXO3a and p21 protein were evaluated by Western Blot analysis. Silencing of p38 MAPK isoform alpha and beta, p53, FOXO3a and p21 were performed by siRNA methods. Exogenous expression of FOXO3a was carried out by electroporated transfection assays. We showed that BBR significantly inhibited growth and induced cell cycle arrest of non small cell lung cancer (NSCLC) cells in the G0/G1 phase in a dose-dependent manner. Furthermore, we found that BBR increased phosphorylation of p38 MAPK and ERK1/2 in a time-dependent and induced protein expression of tumor suppressor p53 and transcription factor FOXO3a in a dose-dependent fashion. The specific inhibitor of p38 MAPK (SB203580), and silencing of p38alpha MAPK by small interfering RNAs (siRNAs), but not ERK1/2 inhibitor (PD98059) blocked the stimulatory effects of BBR on protein expression of p53 and FOXO3a. Interestingly, inhibition of p53 using one specific inhibitor (Pifithrin-alpha) and silencing of p53 using siRNAs overcome the inhibitory effect of BBR on cell growth. Silencing of FOXO3a appeared to attenuate the effect of BBR on p53 expression, cell proliferation and apoptosis. Furthermore, BBR induces the protein expression of cell cycle inhibitor p21 (CIP1/WAF1), which was not observed in cells silencing of p53 or FOXO3alpha gene. Intriguingly, exogenous expression of FOXO3a enhanced the expression of p21 (CIP1/WAF1) and strengthened BBR-induced apoptosis. Our results show that BBR inhibits proliferation and induces apoptosis of NSCLC cells through activation of p38alpha MAPK signaling pathway, followed by induction of the protein expression of p53 and FOXO3a. The latter contribute to the BBR-increased p21 (CIP1/WAF1) protein expression. The exogenous FOXO3a, interaction and mutually exclusive events of p53 and FOXO3a augment the overall response of BBR.
    Journal of Experimental & Clinical Cancer Research 04/2014; 33(1):36. DOI:10.1186/1756-9966-33-36 · 4.43 Impact Factor
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