Identification of a p53-dependent negative response element in the Bcl-2 gene

La Jolla Cancer Research Foundation, Cancer Research Center, California 92037.
Cancer Research (Impact Factor: 9.33). 07/1994; 54(12):3131-5.
Source: PubMed


Recently, we have shown that the p53 tumor suppressor gene product can inhibit expression of the bcl-2 gene. In this report, we explored the molecular basis for p53-mediated down-regulation of bcl-2 gene expression using a cotransfection approach involving p53 expression plasmids and chloramphenicol acetyltransferase (CAT) reporter gene constructs containing regions from the bcl-2 gene. When transfected into a p53-deficient human lung cancer cell line H358, reporter gene constructs containing only the promoter region of bcl-2 and upstream sequences were not suppressed by p53. Inclusion of bcl-2 gene sequences corresponding to the 5' untranslated region in bcl-2/CAT constructs, however, resulted in p53-dependent down-regulation. A 195-base pair segment from the bcl-2 gene 5' untranslated region was found to be capable of conferring p53-dependent repression on a heterologous expression plasmid containing CAT under the control of an SV40 immediate early-region promoter. This p53-negative response element functioned in an orientation-independent manner when placed either upstream or downstream of the SV40-CAT transcription unit. The results demonstrate the existence of a negative response element in the bcl-2 gene through which p53 may either directly or indirectly transcriptionally down-regulate expression of this gene involved in the regulation of programmed cell death.

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    • "The positive regulation of Bcl-2 transcription is modulated by cAMP responsive element binding protein [54], C/EBP [55], and NF-κB [56]. In addition, Bcl-2 is also negatively regulated by π1 [57], WT1 [58], and p53 [59]. In our study, p53 was involved in the down-regulation of Bcl-2 expression in NVP-BEZ235 plus curcumin-treated cells (Figure 5B–D). "
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    ABSTRACT: The PI3K/Akt and mTOR signaling pathways are important for cell survival and growth, and they are highly activated in cancer cells compared with normal cells. Therefore, these signaling pathways are targets for inducing cancer cell death. The dual PI3K/Akt and mTOR inhibitor NVP-BEZ235 completely inhibited both signaling pathways. However, NVP-BEZ235 had no effect on cell death in human renal carcinoma Caki cells. We tested whether combined treatment with natural compounds and NVP-BEZ235 could induce cell death. Among several chemopreventive agents, curcumin, a natural biologically active compound that is extracted from the rhizomes of Curcuma species, markedly induced apoptosis in NVP-BEZ235-treated cells. Co-treatment with curcumin and NVP-BEZ235 led to the down-regulation of Mcl-1 protein expression but not mRNA expression. Ectopic expression of Mcl-1 completely inhibited curcumin plus NVP-NEZ235-induced apoptosis. Furthermore, the down-regulation of Bcl-2 was involved in curcumin plus NVP-BEZ235-induced apoptosis. Curcumin or NVP-BEZ235 alone did not change Bcl-2 mRNA or protein expression, but co-treatment reduced Bcl-2 mRNA and protein expression. Combined treatment with NVP-BEZ235 and curcumin reduced Bcl-2 expression in wild-type p53 HCT116 human colon carcinoma cells but not p53-null HCT116 cells. Moreover, Bcl-2 expression was completely reversed by treatment with pifithrin-α, a p53-specific inhibitor. Ectopic expression of Bcl-2 also inhibited apoptosis in NVP-BE235 plus curcumin-treated cells. In contrast, NVP-BEZ235 combined with curcumin did not have a synergistic effect on normal human skin fibroblasts and normal human mesangial cells. Taken together, combined treatment with NVP-BEZ235 and curcumin induces apoptosis through p53-dependent Bcl-2 mRNA down-regulation at the transcriptional level and Mcl-1 protein down-regulation at the post-transcriptional level.
    Full-text · Article · Apr 2014 · PLoS ONE
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    • "The Bcl-2 gene is an anti-apoptotic gene that represses initiation steps of apoptosis via inhibition of the pro-apoptotic proteins. Bcl-2 is over expressed in a high percentage of human breast cancer cells (8, 9). "
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    ABSTRACT: Objective(s): Regarding the presence of many active biological constituents in Avicennia marina, the present investigation was carried out to study cytotoxic activity of crude methanol leave extract and column chromatographic fractions of A. marina against MDA-MB 231 cell line (human breast cancer cell) and HEK (Human embryonic kidney cell) line. Materials and Methods: The anticancer activity of crude methanol extract and sub-fractions were evaluated, using MTT assay. The induction of apoptosis was determined by analyzing DNA fragmentation in breast cancer cells treated with active fraction of crude methanol extract using agarose gel electrophoresis. To investigate molecular mechanism of apoptosis, gene expression levels of p53 and Bcl-2 were measured using quantitative real time PCR. Results: Fraction 10 was the most active fraction and was detected with HPLC as luteolin. The 50% cell cytotoxic concentration (CC50) of crude methanol extract and luteolin was 250 and 28 µg/ml, respectively. This fraction was found to be an apoptotic agent against MDA-MB 231 cells, which leads to causing DNA fragmentation. The mRNA expression level of Bcl-2 and p53 was significantly decreased and increased respectively in cancer cells treated by luteolin. Conclusion: The results suggested that Luteolin isolated from Avicennia marina could probably induce apoptosis on breast cancer cell line by the regulation of p53 and Bcl-2 pathways.
    Full-text · Article · Nov 2013 · Iranian Journal of Basic Medical Science
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    • "Despite this point mutation, phosphorylation of P53 at Ser392 results in transactivation of P53 and oncogenic function of P53 mutant [32]. Activated (phosphorylated) P53 trans-represses anti-apoptotic BCL-2 [33,34] and over expresses pro-apoptotic BAX [33], which triggers the caspase cascade. Consistently, P276-00 treatment in FaDu cells showed increased P53 phosphorylation at Ser392 and cleaved CASP-3 expression along with reduced BCL2 to BAX ratio, which was associated with enhanced apoptosis (measured by FACS). "
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    ABSTRACT: Background Tumors of the head and neck present aggressive pathological behavior in patients due to high expression of CDK/CCND1 proteins. P276-00, a novel CDK inhibitor currently being tested in clinic, inhibits growth of several cancers in vitro and in vivo. The pre clinical activity of P276-00 in head and neck cancer and its potential mechanisms of action at molecular level are the focus of the current studies. Method We have investigated the anti-cancer activity of P276-00 in head and neck tumors in vitro and in vivo. Candidate gene expression profiling and cell based proteomic approaches were taken to understand the pathways affected by P276-00 treatment. Results It was observed that P276-00 is cytotoxic across various HNSCC cell lines with an IC50 ranging from 1.0-1.5 μmoles/L and culminated in significant cell-cycle arrest in G1/S phase followed by apoptosis. P276-00 treatment suppressed cell proliferation through inhibition of CCND1 expression, reduced phosphorylation of retinoblastoma protein and abrogative transcription of E2F1 gene targets. Further, we observed that apoptosis was mediated through P53 activation leading to higher BAX/BCL-2 ratio and cleaved caspase-3 levels. It was also seen that P276-00 treatment reduced expression of tumor micro-environment proteins such as IL-6, secreted EGFR and HSPA8. Finally, P276-00 treatment resulted in significant tumor growth inhibition in xenograft tumor models via lowered proliferative activity of E2F1 and aggravated P53 mediated apoptosis. Conclusion In summary, we have observed that P276-00 inhibits cyclin-D/CDK4/P16/pRB/E2F axis and induces apoptosis by increased P53 phosphorylation in HNSCC cells. These results suggest a novel indication for P276-00 in head and neck cancer with a potential role for IL-6 and HSPA8 as candidate serum biomarkers.
    Full-text · Article · Feb 2013 · Journal of Translational Medicine
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