Chemotherapy-induced apoptosis in a transgenic model of neuroblastoma proceeds through p53 induction.

Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143, USA.
Neoplasia (New York, N.Y.) (Impact Factor: 5.4). 12/2008; 10(11):1268-74.
Source: PubMed

ABSTRACT Chemoresistance in neuroblastoma is a significant issue complicating treatment of this common pediatric solid tumor. MYCN-amplified neuroblastomas are infrequently mutated at p53 and are chemosensitive at diagnosis but acquire p53 mutations and chemoresistance with relapse. Paradoxically, Myc-driven transformation is thought to require apoptotic blockade. We used the TH-MYCN transgenic murine model to examine the role of p53-driven apoptosis on neuroblastoma tumorigenesis and the response to chemotherapy. Tumors formed with high penetrance and low latency in p53-haploinsufficient TH-MYCN mice. Cyclophosphamide (CPM) induced a complete remission in p53 wild type TH-MYCN tumors, mirroring the sensitivity of childhood neuroblastoma to this agent. Treated tumors showed a prominent proliferation block, induction of p53 protein, and massive apoptosis proceeding through induction of the Bcl-2 homology domain-3-only proteins PUMA and Bim, leading to the activation of Bax and cleavage of caspase-3 and -9. Apoptosis induced by CPM was reduced in p53-haploinsufficient tumors. Treatment of MYCN-expressing human neuroblastoma cell lines with CPM induced apoptosis that was suppressible by siRNA to p53. Taken together, the results indicate that the p53 pathway plays a significant role in opposing MYCN-driven oncogenesis in a mouse model of neuroblastoma and that basal inactivation of the pathway is achieved in progressing tumors. This, in part, explains the striking sensitivity of such tumors to chemotoxic agents that induce p53-dependent apoptosis and is consistent with clinical observations that therapy-associated mutations in p53 are a likely contributor to the biology of tumors at relapse and secondarily mediate resistance to therapy.

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    ABSTRACT: Neuroblastoma, the most common extracranial solid tumor of childhood, is thought to originate from undifferentiated neural crest cells. Amplification of the MYC family member, MYCN, is found in ∼25% of cases and correlates with high-risk disease and poor prognosis. Currently, amplification of MYCN remains the best-characterized genetic marker of risk in neuroblastoma. This article reviews roles for MYCN in neuroblastoma and highlights recent identification of other driver mutations. Strategies to target MYCN at the level of protein stability and transcription are also reviewed.
    Cold Spring Harbor Perspectives in Medicine 10/2013; 3(10). · 7.56 Impact Factor
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    ABSTRACT: PURPOSE: MYCN amplification and p53 inactivation are two typical characteristics of aggressive neuroblastomas and are strongly associated with cancer progression and treatment failure. In an effort to develop new therapeutic agents to treat the aggressive neuroblastomas, we constructed ZD55-shMYCN, an oncolytic adenovirus ZD55 carrying short hairpin RNA (shRNA) targeting MYCN gene, and investigated the effects on proliferation of the p53-null and MYCN-amplified neuroblastoma cell line LA1-55N in vitro and in vivo by ZD55-shMYCN. METHODS: In this study, we used ZD55-shMYCN to treat p53-null and MYCN-amplified neuroblastoma cells. To confirm the ability of selective replication of the ZD55-shMYCN, we examined the expression of E1A protein by western blotting. We used quantitative real-time PCR analysis and western blotting analysis to determine the inhibitory effect of ZD55-shMYCN on MYCN expression. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] cell proliferation assay and xenograft mouse model were used to test the antigrowth efficacy of ZD55-shMYCN. RESULTS: The results showed that ZD55-shMYCN selectively replicated and significantly downregulated the MYCN expression in LA1-55N cells. ZD55-shMYCN effectively inhibited the proliferation in LA1-55N cells in vitro and significantly inhibited tumor growth in vivo xenograft tumor in nude mice. CONCLUSIONS: ZD55-shMYCN provides a novel agent for treating MYCN-amplified and p53-inactive aggressive neuroblastoma, representing a promising approach for further clinical development.
    Journal of Cancer Research and Clinical Oncology 02/2013; · 2.91 Impact Factor
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    ABSTRACT: Neuroblastoma (NB) is one of the most common malignant solid tumors in childhood, which derives from the sympathoadrenal lineage of the neural crest and exhibits extremely heterogeneous biological and clinical behaviors. The infant patients frequently undergo spontaneous regression even with metastatic disease, whereas the patients of more than one year of age who suffer from disseminated disease have a poor outcome despite intensive multimodal treatment. Spontaneous regression in favorable NBs has been proposed to be triggered by nerve growth factor (NGF) deficiency in the tumor with NGF dependency for survival, while aggressive NBs have defective apoptotic machinery which enables the tumor cells to evade apoptosis and confers the resistance to treatment. This paper reviews the molecules and pathways that have been recently identified to be involved in apoptotic cell death in NB and discusses their potential prospects for developing more effective therapeutic strategies against aggressive NB.
    Cells. 06/2013; 2(2):432-59.


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May 19, 2014