Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Development of drug resistance is one of the major obstacles in cancer chemotherapy. The molecular mechanism leading to drug resistance is still not fully understood. A10A cells, a doxorubicin-resistant subline of human squamous cell carcinoma A431 cells, showed cross-resistance to methotrexate and also resistance to the drug-induced apoptosis. The cells also showed overexpression of a mutated form of p53, p53-R273H (Arg to His at codon 273), and down-regulation of procaspase-3. Knockdown of p53-R273H by p53 small interfering RNA in A431 cells increased procaspase-3 level and sensitized the cells to drug-induced apoptosis. On the other hand, transfection of p53-R273H into p53 null human osteosarcoma Saos-2 cells down-regulated procaspase-3 level and induced resistance to the drug toxicity and drug-induced apoptosis. The results support the idea that p53-R273H may gain new functions in induction of drug resistance and impairment in drug-induced apoptosis through down-regulation of procaspase-3 level. The study sheds new light on the understanding of the gain of function and drug resistance mechanisms associated with mutant p53.
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PMID:p53-R273H gains new function in induction of drug resistance through down-regulation of procaspase-3. 1736 98

p53 regulates apoptosis and the cell cycle through actions in the nucleus and cytoplasm. Altering the subcellular localization of p53 can alter its biological function. Therefore, small molecules that change the localization of p53 would be useful chemical probes to understand the influence of subcellular localization on the function of p53. To identify such molecules, a high-content screen for compounds that increased the localization of p53 to the nucleus or cytoplasm was developed, automated, and conducted. With this image-based assay, we identified ellipticine that increased the nuclear localization of GFP-mutant p53 protein but not GFP alone in Saos-2 osteosarcoma cells. In addition, ellipticine increased the nuclear localization of endogenous p53 in HCT116 colon cancer cells with a resultant increase in the transactivation of the p21 promoter. Increased nuclear p53 after ellipticine treatment was not associated with an increase in DNA double stranded breaks, indicating that ellipticine shifts p53 to the nucleus through a mechanism independent of DNA damage. Thus, a chemical biology approach has identified a molecule that shifts the localization of p53 and enhances its nuclear activity.
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PMID:A high-content chemical screen identifies ellipticine as a modulator of p53 nuclear localization. 1818 Oct 20

Using short hairpin RNA against p53, transient ectopic expression of wild-type p53 or mutant p53 (R248W or R175H), and a p53- and p21-dependent luciferase reporter assay, we demonstrated that growth arrest and apoptosis of FaDu (human pharyngeal squamous cell carcinoma), Hep3B (hepatoma), and MG-63 (osteosarcoma) cells induced by aloe-emodin (AE) are p53-independent. Co-immunoprecipitation and small interfering RNA (siRNA) studies demonstrated that AE caused S-phase cell cycle arrest by inducing the formation of cyclin A-Cdk2-p21 complexes through extracellular signal-regulated kinase (ERK) activation. Ectopic expression of Bcl-X(L) and siRNA-mediated Bax attenuation significantly inhibited apoptosis induced by AE. Cyclosporin A or the caspase-8 inhibitor Z-IETD-FMK blocked AE-induced loss of mitochondrial membrane potential and prevented increases in reactive oxygen species and Ca(++). Z-IETD-FMK inhibited AE-induced apoptosis, Bax expression, Bid cleavage, translocation of tBid to mitochondria, ERK phosphorylation, caspase-9 activation, and the release of cytochrome c, apoptosis-inducing factor (AIF), and endonuclease G from mitochondria. The stability of the mRNAs encoding caspase-8 and -10-associated RING proteins (CARPs) 1 and 2 was affected by AE, whereas CARP1 or 2 overexpression inhibited caspase-8 activation and apoptosis induced by AE. Collectively, our data indicate AE induces caspase-8-mediated activation of mitochondrial death pathways by decreasing the stability of CARP mRNAs in a p53-independent manner.
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PMID:Destabilization of CARP mRNAs by aloe-emodin contributes to caspase-8-mediated p53-independent apoptosis of human carcinoma cells. 2130 45

The tumour suppressor p53 is the most frequently mutated gene in human cancer. Reactivation of mutant p53 by small molecules is an exciting potential cancer therapy. Although several compounds restore wild-type function to mutant p53, their binding sites and mechanisms of action are elusive. Here computational methods identify a transiently open binding pocket between loop L1 and sheet S3 of the p53 core domain. Mutation of residue Cys124, located at the centre of the pocket, abolishes p53 reactivation of mutant R175H by PRIMA-1, a known reactivation compound. Ensemble-based virtual screening against this newly revealed pocket selects stictic acid as a potential p53 reactivation compound. In human osteosarcoma cells, stictic acid exhibits dose-dependent reactivation of p21 expression for mutant R175H more strongly than does PRIMA-1. These results indicate the L1/S3 pocket as a target for pharmaceutical reactivation of p53 mutants.
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PMID:Computational identification of a transiently open L1/S3 pocket for reactivation of mutant p53. 2336 Sep 98

Osteosarcoma is a highly metastatic tumor affecting adolescents, for which there is no second-line chemotherapy. As suggested for most tumors, its capability to overgrow is probably driven by cancer stem cells (CSCs), and finding new targets to kill CSCs may be critical for improving patient survival. TP53 is the most frequently mutated tumor suppressor gene in cancers and mutant p53 protein (mutp53) can acquire gain of function (GOF) strongly contributing to malignancy. Studies thus far have not shown p53-GOF in osteosarcoma. Here, we investigated TP53 gene status/role in 3AB-OS cells-a highly aggressive CSC line previously selected from human osteosarcoma MG63 cells-to evaluate its involvement in promoting proliferation, invasiveness, resistance to apoptosis and stemness. By RT-PCR, methylation-specific PCR, fluorescent in situ hybridization, DNA sequence, western blot and immunofluorescence analyses, we have shown that-in comparison with parental MG63 cells where TP53 gene is hypermethylated, rearranged and in single copy-in 3AB-OS cells, TP53 is unmethylated, rearranged and in multiple copies, and mutp53 (p53-R248W/P72R) is post-translationally modified and with nuclear localization. p53-R248W/P72R-knockdown by short-interfering RNA reduced the growth and replication rate of 3AB-OS cells, markedly increasing cell cycle inhibitor levels and sensitized 3AB-OS cells to TRAIL-induced apoptosis by DR5 up-regulation; moreover, it strongly decreased the levels of stemness and invasiveness genes. We have also found that the ectopic expression of p53-R248W/P72R in MG63 cells promoted cancer stem-like features, as high proliferation rate, sphere formation, clonogenic growth, high migration and invasive ability; furthermore, it strongly increased the levels of stemness proteins. Overall, the findings suggest the involvement of p53-R248W/P72R at the origin of the aberrant characters of the 3AB-OS cells with the hypothesis that its GOF can be at the root of the dedifferentiation of MG63 cells into CSCs.
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PMID:Mutant p53 gain of function can be at the root of dedifferentiation of human osteosarcoma MG63 cells into 3AB-OS cancer stem cells. 2437 20

p53(R172H/+) mice inherit a p53 mutation found in Li-Fraumeni syndrome and develop metastatic tumors at much higher frequency than p53(+/-) mice. To explore the mutant p53 metastatic phenotype, we used expression arrays to compare primary osteosarcomas from p53(R172H/+) mice with metastasis to osteosarcomas from p53(+/-) mice lacking metastasis. For this study, 213 genes were differentially expressed with a P value <0.05. Of particular interest, Pla2g16, which encodes a phospholipase that catalyzes phosphatidic acid into lysophosphatidic acid and free fatty acid (both implicated in metastasis), was increased in p53(R172H/+) osteosarcomas. Functional analyses showed that Pla2g16 knockdown decreased migration and invasion in mutant p53-expressing cells, and vice versa: overexpression of Pla2g16 increased the invasion of p53-null cells. Furthermore, Pla2g16 levels were increased upon expression of mutant p53 in both mouse and human osteosarcoma cell lines, indicating that Pla2g16 is a downstream target of the mutant p53 protein. ChIP analysis revealed that several mutant p53 proteins bind the Pla2g16 promoter at E26 transformation-specific (ETS) binding motifs and knockdown of ETS2 suppressed mutant p53 induction of Pla2g16. Thus, our study identifies a phospholipase as a transcriptional target of mutant p53 that is required for metastasis.
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PMID:Pla2g16 phospholipase mediates gain-of-function activities of mutant p53. 2502 3

Mutant p53 can exert oncogenic activity by inhibitory interaction with p73. The small-molecule RETRA has been described to disrupt this interaction and to suppress carcinoma cells (Kravchenko et al., 2008). RETRA's anticancer activity was restricted to tumour cells bearing mutant p53; it was not active in p53 negative and in p53 wild-type cells. Here, we explored the responsiveness of Ewing's sarcoma (ES) cells with mutant p53 to RETRA. For comparison, we also tested RETRA in p53 null and in p53 wild-type ES cells. We found RETRA to be effective in the three mutant p53 ES cell lines investigated. Strikingly, however, RETRA was similarly effective in the p53-deficient and in the two p53 wild-type ES cell lines examined. RETRA elicited apoptosis, as assessed by flow cytometric analyses of mitochondrial depolarisation and DNA fragmentation, caspase 3/7 activity assay and PARP-1 cleavage immunodetection, and G2/M cell cycle arrest completely independent of the cellular TP53 status. In contrast, various p53-deficient and -proficient carcinoma, osteosarcoma and leukaemia cells were unresponsive to RETRA. RETRA also induced gene expression of p53 target genes PUMA and p21 in ES cells irrespective of their TP53 status. These in vitro findings provide a rationale for an in vivo exploration of RETRA's potential as an effective therapeutic approach for patients with ES.
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PMID:RETRA exerts anticancer activity in Ewing's sarcoma cells independent of their TP53 status. 2580

In vitro modeling of human disease has recently become feasible with induced pluripotent stem cell (iPSC) technology. Here, we established patient-derived iPSCs from a Li-Fraumeni syndrome (LFS) family and investigated the role of mutant p53 in the development of osteosarcoma (OS). LFS iPSC-derived osteoblasts (OBs) recapitulated OS features including defective osteoblastic differentiation as well as tumorigenic ability. Systematic analyses revealed that the expression of genes enriched in LFS-derived OBs strongly correlated with decreased time to tumor recurrence and poor patient survival. Furthermore, LFS OBs exhibited impaired upregulation of the imprinted gene H19 during osteogenesis. Restoration of H19 expression in LFS OBs facilitated osteoblastic differentiation and repressed tumorigenic potential. By integrating human imprinted gene network (IGN) into functional genomic analyses, we found that H19 mediates suppression of LFS-associated OS through the IGN component DECORIN (DCN). In summary, these findings demonstrate the feasibility of studying inherited human cancer syndromes with iPSCs.
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PMID:Modeling familial cancer with induced pluripotent stem cells. 2586 Jun 7

The transcriptional cofactor Che-1 is an RNA polymerase II (Pol II) which is involved in tumorigenesis, such as breast cancer and multiple myeloma. Che-1 can also regulate mutant p53 expression, which plays roles in many types of cancer. In this study, we aimed to investigate the effects and specific mechanism of Che-1 in the regulation of osteosarcoma (OS) cell growth. We found that Che-1 is highly expressed in several kinds of OS cells compared with osteoblast hFOB1.19 cells. MTT and flow cytometry assays showed that Che-1 depletion by siRNA markedly suppressed MG-63 and U2OS cell proliferation and promoted apoptosis. The chromatin immunoprecipitation (ChIP) assay verified the presence of Che-1 on the p53 promoter in MG-63 and U2OS cells carrying mutant p53. Further studies showed that Che-1 depletion inhibited mutant p53 expression. Notably, our study showed that the loss of Che-1 inhibits proliferation and promotes apoptosis in MG-63 cells by decreasing the level of mutant p53. Therefore, these findings open the possibility that silencing of Che-1 will have therapeutic benefit in OS.
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PMID:Che-1 gene silencing induces osteosarcoma cell apoptosis by inhibiting mutant p53 expression. 2701 5

TP53 is the most frequently mutated gene in human cancer. Many mutant p53 proteins exert oncogenic gain-of-function (GOF) properties that contribute to metastasis, but the mechanisms mediating these functions remain poorly defined in vivo. To elucidate how mutant p53 GOF drives metastasis, we developed a traceable somatic osteosarcoma mouse model that is initiated with either a single p53 mutation (p53R172H) or p53 loss in osteoblasts. Our study confirmed that p53 mutant mice developed osteosarcomas with increased metastasis as compared with p53-null mice. Comprehensive transcriptome RNA sequencing (RNA-seq) analysis of 16 tumors identified a cluster of small nucleolar RNAs (snoRNAs) that are highly up-regulated in p53 mutant tumors. Regulatory element analysis of these deregulated snoRNA genes identified strong enrichment of a common Ets2 transcription factor-binding site. Homozygous deletion of Ets2 in p53 mutant mice resulted in strong down-regulation of snoRNAs and reversed the prometastatic phenotype of mutant p53 but had no effect on osteosarcoma development, which remained 100% penetrant. In summary, our studies identify Ets2 inhibition as a potential therapeutic vulnerability in p53 mutant osteosarcomas.
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PMID:Integrative genome analysis of somatic p53 mutant osteosarcomas identifies Ets2-dependent regulation of small nucleolar RNAs by mutant p53 protein. 2905 86


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