Project description:MYCN amplification in neuroblastoma leads to aberrant expression of MYCN oncoprotein, which binds active genes promoting transcriptional amplification. Yet how MYCN coordinates transcription elongation to meet productive transcriptional amplification and which elongation machinery represents MYCN-driven vulnerability remain to be identified. We conducted a targeted screen of transcription elongation factors and identified the super elongation complex (SEC) as a unique vulnerability in MYCN-amplified neuroblastomas. MYCN directly binds EAF1 and recruits SEC to enhance processive transcription elongation. Depletion of EAF1 or AFF1/AFF4, another core subunit of SEC, leads to a global reduction in transcription elongation and elicits selective apoptosis of MYCN-amplified neuroblastoma cells. A combination screen reveals SEC inhibition synergistically potentiates the therapeutic efficacies of FDA-approved BCL2 antagonist ABT-199, in part due to suppression of MCL1 expression, both in MYCN-amplified neuroblastoma cells and in patient-derived xenografts. These findings identify disruption of the MYCN-SEC regulatory axis as a promising therapeutic strategy in neuroblastoma.
Project description:Neuroblastoma is the third most common pediatric cancer and is responsible for approximately 15% of all childhood cancer deaths (Maris & Matthay, 1999). In our analysis, we found that poor patient survival with increasing mRNA expression level of AURKA and AURKB in Mycn-amplified neuroblastoma. In the light of this evidence, we were able to find possibilities of existing inhibitors for therapy. According to the following experiments, we found that tozasertib, a pan-Aurora kinase inhibitor, has high therapeutic potential in neuroblastoma treatment. First, we performed in vitro experiments to reveal that tozasertib suppressed cell proliferation in multiple Mycn-amplified neuroblastoma cell lines. Next, we evaluated ex vivo not only in Mycn-amplified neuroblastoma xenograft mouse model but also TH-Mycn transgenic mouse model. The results showed that tozasertib significantly inhibited the tumor growth and prolonged the survival probability in both animal models. Finally, we explored the mechanism of tozasertib-treated tissues in two animal models by iTRAQ proteomic.
Project description:Here we sought metabolic alterations specifically associated with amplified MYCN as nodes to indirectly target the MYCN oncogene. Liquid chromatography-mass spectrometry-based proteomics identified 7 proteins consistently correlated with MYCN in proteomes from 49 neuroblastoma biopsies and 13 cell lines. Among these were phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme in de novo serine synthesis. MYCN associated with two regions in the PHGDH promoter, supporting transcriptional PHGDH regulation by MYCN. Pulsed stable isotope-resolved metabolomics utilizing 13C-glucose labeling demonstrated higher de novo serine synthesis in MYCN-amplified cells compared to cells with diploid MYCN. An independence of MYCN-amplified cells from exogenous serine and glycine was demonstrated by serine and glycine starvation, which attenuated nucleotide pools and proliferation only in cells with diploid MYCN but did not diminish these endpoints in MYCN-amplified cells. Proliferation was attenuated in MYCN-amplified cells by CRISPR/Cas9-mediated PHGDH knockout or treatment with PHGDH small molecule inhibitors without affecting cell viability. PHGDH inhibitors administered as single-agent therapy to NMRI-Foxn1nu/nu mice harboring patient-derived MYCN-amplified neuroblastoma xenografts slowed tumor growth. However, combining a PHGDH inhibitor with the standard-of-care chemotherapy drug, cisplatin, revealed antagonism of chemotherapy efficacy in vivo. Emergence of chemotherapy resistance was confirmed in the genetic PHGDH knockout model in vitro. Altogether, PHDGH knockout and inhibition by small molecules consistently slows proliferation, but stops short of killing the cells, which then establish resistance to classical chemotherapy. Although PHGDH inhibition with small molecules has produced encouraging results in other preclinical cancer models, this approach must be considered with caution in patients with neuroblastoma.
Project description:The MYCN locus is amplified in about half of high-risk neuroblastoma tumors. To identify genomic loci occupied by MYCN protein in the MYCN-amplified neuroblastoma cell lines NGP, Kelly and NB-1643, we performed chromatin immunoprecipitation coupled with Next-Generation Sequencing (ChIP-seq) using an anti-MYCN antibody.
Project description:Overexpression of MYC family members is linked to poor clinical outcome in many human cancers. These oncoproteins drive proliferation, alter metabolism, and mediate an antioxidant response to maintain tumor cell redox balance. However, to date, there are no effective inhibitors that specifically target MYC-amplified tumors. We demonstrate that MYCN-amplified, aggressive childhood neuroblastoma cells undergo ferroptotic cell death in vivo in the absence of intracellular cysteine, thus implicating MYCN as a predictive biomarker for ferroptosis sensitivity in neuroblastoma. Although cysteine is provided by both uptake from the microenvironment and MYCN-induced transsulfuration of methionine, glutathione levels remain low in these highly proliferative cancer cells due to concomitant cysteine utilization for protein and nucleotide synthesis. Consequently, MYCN-amplified neuroblastoma cells are highly susceptible to lipid peroxidation and ferroptosis, which must be counteracted by GPX4 activity. Pharmacological inhibition of both cystine uptake and transsulfuration combined with GPX4 inactivation resulted in tumor remission in an orthotopic MYCN-amplified neuroblastoma model. Our data show that MYCN-amplified neuroblastoma is sensitized to ferroptosis, which can be exploited therapeutically, by depleting the intracellular cysteine pool with concomitant GPX4 inactivation. These findings may help to develop novel clinical strategies to target MYCN-amplified tumors by inducing ferroptotic cell death.