Abstract
MYCN drives aggressive behavior and refractoriness to chemotherapy, in several tumors. Since MYCN inactivation in clinical settings is not achievable, alternative vulnerabilities of MYCN-driven tumors need to be explored to identify more effective and less toxic therapies. We previously demonstrated that PARP inhibitors enhance MYCN-induced replication stress and promote mitotic catastrophe, counteracted by CHK1. Here, we showed that PARP and CHK1 inhibitors synergized to induce death in neuroblastoma cells and in primary cultures of SHH-dependent medulloblastoma, their combination being more effective in MYCN amplified and MYCN overexpressing cells compared to MYCN non-amplified cells. Although the MYCN amplified IMR-32 cell line carrying the p.Val2716Ala ATM mutation showed the highest sensitivity to the drug combination, this was not related to ATM status, as indicated by CRISPR/Cas9-based correction of the mutation. Suboptimal doses of the CHK1 inhibitor MK-8776 plus the PARP inhibitor olaparib led to a MYCN-dependent accumulation of DNA damage and cell death in vitro and significantly reduced the growth of four in vivo models of MYCN-driven tumors, without major toxicities. Our data highlight the combination of PARP and CHK1 inhibitors as a new potential chemo-free strategy to treat MYCN-driven tumors, which might be promptly translated into clinical trials.
Highlights
MYCN deregulation is a recognized driver for numerous childhood and adulthood neuronal and nonneuronal tumors including neuroblastoma, medulloblastomas, rhabdomyosarcoma, neuroendocrine prostate cancer, Wilms tumor, lymphoma and AML [1]
PARP inhibitors enhance the sensitivity to CHK1 inhibitors in MYCN-dependent tumor models CHK1 is highly expressed in MYCN amplified (MNA) compared to MYCN nonamplified and in high-risk compared to low risk nonMNA neuroblastoma patients (Fig. 1A, B)
High CHK1 mRNA expression is associated with a reduced survival in neuroblastoma patients, independently from MNA (Fig. 1C, D), with the same trend we previously reported for PARP1 and PARP2 [38]
Summary
MYCN deregulation is a recognized driver for numerous childhood and adulthood neuronal and nonneuronal tumors including neuroblastoma, medulloblastomas, rhabdomyosarcoma, neuroendocrine prostate cancer, Wilms tumor, lymphoma and AML [1]. It is often caused by genetic amplification, as seen in neuroblastoma and type 3 medulloblastoma. MYCN amplification is an independent poor prognosis marker for many tumor types [1]. This is typically the case for MYCN amplified (MNA) neuroblastoma, accounting for about 50% of the high-risk cases sharing a 50% 5-year survival rate [3].The driving role of MYCN in cancer was confirmed in genetically engineered mouse models [4,5,6,7,8]
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