Project description:We knock down MYCN in human neuroblastoma cell line by RNAi. MYCN knock-down caused global epigenome change, including nucleosome gain on key DNA-repair genes and promoter H3K9ac down regulation.
Project description:We knock down MYCN in human neuroblastoma cell line by RNAi. MYCN knock-down caused global epigenome change, including nucleosome gain on key DNA-repair genes and promoter H3K9ac down regulation.
Project description:We knock down MYCN in human neuroblastoma cell line by RNAi. MYCN knock-down caused global epigenome change, including nucleosome gain on key DNA-repair genes and promoter H3K9ac down regulation.
Project description:PURPOSE:MYCN oncogene amplification is an independent predictor of poor prognosis in neuroblastoma. CX-5461 is a small molecular inhibitor that prevents initiation of ribosomal RNA (rRNA) synthesis by RNA Pol I, down-regulating MYCN/MYC proteins. We hypothesize that neuroblastoma tumor growth can be suppressed by CX-5461. METHODS:MYCN-amplified (KELLY, IMR5) and nonamplified (SY5Y, SKNAS) neuroblastoma cells were treated with CX-5461. MYCN/MYC expression after 24-48 h was determined by Western blot. Orthotopic neuroblastoma tumors created in mice using KELLY cells were treated with CX-5461-loaded silk films implanted locally. Tumor growth was monitored using ultrasound. Histologic evaluation of tumors was performed. RESULTS:IC50 for KELLY, IMR5, SY5Y, and SKNAS cells to CX-5461 was 0.75 μM, 0.02 μM, 0.8 μM, and 1.7 μM, respectively. CX-5461 down-regulated MYCN and MYC proteins at 0.25-1.0 μM on Western blot analysis. CX-5461-loaded silk film released 23.7±3 μg of the drug in 24 h and 48.2±3.9 μg at 120 h. KELLY tumors treated with CX-5461-loaded film reached 800 mm3 after 7.8±1.4 days, while those treated with control film reached the same size on 5.1±0.6 days (p=0.03). CX-5461-treated tumors showed collapse of nucleolar hypertrophy and MYCN protein downregulation. CONCLUSION:We demonstrated that local delivery of CX-5461 via sustained release platform can suppress orthotopic neuroblastoma tumor growth, especially those with MYCN/MYC overexpression.
Project description:One of the greatest barriers to curative treatment of neuroblastoma is its frequent metastatic outgrowth prior to diagnosis, especially in cases driven by amplification of the MYCN oncogene. However, only a limited number of regulatory proteins that contribute to this complex MYCN-mediated process have been elucidated. Here we show that the growth arrest-specific 7 (GAS7) gene, located at chromosome band 17p13.1, is preferentially deleted in high-risk MYCN-driven neuroblastoma. GAS7 expression was also suppressed in MYCN-amplified neuroblastoma lacking 17p deletion. GAS7 deficiency led to accelerated metastasis in both zebrafish and mammalian models of neuroblastoma with overexpression or amplification of MYCN. Analysis of expression profiles and the ultrastructure of zebrafish neuroblastoma tumors with MYCN overexpression identified that GAS7 deficiency led to (i) downregulation of genes involved in cell-cell interaction, (ii) loss of contact among tumor cells as critical determinants of accelerated metastasis, and (iii) increased levels of MYCN protein. These results provide the first genetic evidence that GAS7 depletion is a critical early step in the cascade of events culminating in neuroblastoma metastasis in the context of MYCN overexpression. SIGNIFICANCE: Heterozygous deletion or MYCN-mediated repression of GAS7 in neuroblastoma releases an important brake on tumor cell dispersion and migration to distant sites, providing a novel mechanism underlying tumor metastasis in MYCN-driven neuroblastoma.See related commentary by Menard, p. 2815.
