Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although polyamines are well recognized for their critical involvement in cell growth, the cell cycle specificity of this requirement has not yet been characterized with respect to the newly delineated regulatory pathways. We recently reported that polyamine analogues having close structural and functional similarities to the natural polyamines produce a distinct G1 and G2-M cell cycle arrest in MALME-3M human melanoma cells. To determine a molecular basis for this observation, we examined the effects of N1,N11-diethylnorspermine on cell cycle regulatory proteins associated with G1 arrest. The analogue is known to deplete polyamine pools by suppressing biosynthetic enzymes and potently inducing the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase. Treatment of MALME-3M cells with 10 microM N1,N11-diethylnorspermine caused an increase in hypophosphorylated Rb, which correlated temporally with the onset of G1 arrest at 16-24 h. Rb hypophosphorylation was preceded by an increase in wild-type p53 (approximately 100-fold at maximum) and a concomitant increase in the cyclin-dependent kinase inhibitor, p21WAF1/CIP1 (p21; approximately 5-fold at maximum). Another cyclin-dependent kinase inhibitor, p27KIP1, and cyclin D increased slightly, whereas proliferating cell nuclear antigen and p130 remained unchanged. Induction of p21 protein was accompanied by an increase in p21 mRNA, whereas induction of p53 protein was not, suggesting transcriptional activation of the former and posttranscriptional regulation of the latter. SK-MEL-28 human melanoma cells, which contain a mutated p53, failed to induce p53 or p21 and did not arrest in G1. Rather, these cells rapidly underwent programmed cell death within 48 h. Overall, these findings provide the first indication of the cell cycle regulatory pathways by which polyamine antagonists such as analogues might inhibit growth in cells containing wild-type p53 and further suggest a mechanistic basis for differential cellular responses to these agents.
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PMID:Polyamine analogue induction of the p53-p21WAF1/CIP1-Rb pathway and G1 arrest in human melanoma cells. 1009 60

5-fluorouracil (5-FU) is the major chemotherapeutic agent for treatment of colorectal carcinoma, but the molecular mechanisms of response and resistance are not understood completely. We therefore studied the 5-FU dose response and time course of gene expression transcriptome changes in colon carcinoma cell lines that are relatively sensitive to or resistant to 5-FU (RKO and HT29, respectively. We identified cellular pathways and corroborated functions of selected pathways. Expression of genes for polyamine biosynthesis, i.e., ornithine decarboxylase (ODC) and spermine and spermidine synthases, was repressed in the sensitive line, while the biosynthesis-inhibiting gene ODC antizyme was induced in the resistant line. The rate-limiting gene in catabolism, spermine/spermidine acetyltransferase, was induced in both lines. Polyamine levels showed corresponding drastic decreases after 5-FU treatment, and polyamine replenishment interfered with 5-FU-induced apoptosis. In the sensitive cells which have wild-type p53, the p53 gene and its downstream genes including p21/WAF1, mdm2, Fas, mic-1, EphA2, and ferredoxin reductase as well as genes in the tumor necrosis factor (TNF) pathway including TNF receptor 2 (TNFR2) were induced, but not Fas ligand (FasL). Exposure to exogenous FasL increased 5-FU-induced apoptosis, and anti-TNFR2 antibody, but not anti-TNFR1, partially protected the sensitive cells. Our combination of gene expression profiling and corroborative functional studies revealed that reduced polyamine levels, non-autocrine FasL originating exogenous to tumor cells, and induced TNFR2 are all functional mediators of apoptosis caused by 5-FU in colon carcinoma cells.
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PMID:Apoptotic response to 5-fluorouracil treatment is mediated by reduced polyamines, non-autocrine Fas ligand and induced tumor necrosis factor receptor 2. 1461 30

The thymidylate synthase inhibitor 5-fluorouracil (5-FU) is used widely for chemotherapy of colorectal carcinoma. Recent studies showed that 5-FU affects polyamine metabolism in colon carcinoma cells. We therefore examined whether combinations of 5-FU with drugs that specifically target polyamine metabolism, i.e. N1,N11-diethylnorspermine (DENSPM) or alpha-difluoromethylornithine (DFMO), have synergistic effects in killing HCT116 colon carcinoma cells with wild-type or absent p53. Our results showed that simultaneous 5-FU and DENSPM, a spermine analogue, synergistically increased transcript levels of the polyamine catabolism enzyme spermidine/spermine N1-acetyltransferase, depleted spermine and spermidine, increased acetylated spermidine, and produced synergistic tumor cell apoptosis in both p53 wild-type and p53-null variants. By contrast, simultaneous combination of 5-FU with DFMO, an inhibitor of the polyamine biosynthetic enzyme ornithine decarboxylase, depleted putrescine but did not produce synergistic cell killing. Some pre-treatment and post-treatment regimens of DENSPM and DFMO were antagonistic to 5-FU depending on cellular p53 status. Protein and transcriptome expression analysis showed that combined 5-FU and DENSPM treatment activated caspase 9, but not caspase 3, and significantly suppressed NADH dehydrogenases and cytochrome c oxidases, consistent with the observed increase in hydrogen peroxide, loss of mitochondrial membrane potential, and release of cytochrome c. Our findings demonstrate the importance of the polyamine pathway in 5-FU effects and suggest that the combination of 5-FU with DENSPM has potential for development as therapy for colorectal carcinoma.
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PMID:Combination of 5-fluorouracil and N1,N11-diethylnorspermine markedly activates spermidine/spermine N1-acetyltransferase expression, depletes polyamines, and synergistically induces apoptosis in colon carcinoma cells. 1554 79