ABSTRACT
MYC proteins are major drivers of cancer yet are considered undruggable because their DNA binding domains are composed of two extended alpha helices with no apparent surfaces for small-molecule binding. Proteolytic degradation of MYCN protein is regulated in part by a kinase-independent function of Aurora A. We describe a class of inhibitors that disrupts the native conformation of Aurora A and drives the degradation of MYCN protein across MYCN-driven cancers. Comparison of cocrystal structures with structure-activity relationships across multiple inhibitors and chemotypes, coupled with mechanistic studies and biochemical assays, delineates an Aurora A conformation-specific effect on proteolytic degradation of MYCN, rather than simple nanomolar-level inhibition of Aurora A kinase activity.
Subject(s)
Antineoplastic Agents/pharmacology , Aurora Kinase A/chemistry , Neuroblastoma/drug therapy , Nuclear Proteins/metabolism , Oncogene Proteins/metabolism , Phenylurea Compounds/pharmacology , Pyrimidines/pharmacology , Allosteric Regulation , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacokinetics , Area Under Curve , Aurora Kinase A/antagonists & inhibitors , Aurora Kinase A/metabolism , Catalytic Domain , Cell Line, Tumor , Cell Survival/drug effects , Crystallography, X-Ray , Humans , Mice , Mice, Inbred NOD , Mice, Nude , Mice, SCID , Models, Molecular , N-Myc Proto-Oncogene Protein , Neuroblastoma/pathology , Nuclear Proteins/chemistry , Oncogene Proteins/chemistry , Phenylurea Compounds/chemistry , Phenylurea Compounds/pharmacokinetics , Phosphorylation , Protein Processing, Post-Translational , Protein Structure, Secondary , Proteolysis , Pyrimidines/chemistry , Pyrimidines/pharmacokinetics , S Phase Cell Cycle Checkpoints/drug effects , Structure-Activity Relationship , Tumor Burden/drug effects , Xenograft Model Antitumor AssaysABSTRACT
Tumor recurrence is a leading cause of cancer mortality. Therapies for recurrent disease may fail, at least in part, because the genomic alterations driving the growth of recurrences are distinct from those in the initial tumor. To explore this hypothesis, we sequenced the exomes of 23 initial low-grade gliomas and recurrent tumors resected from the same patients. In 43% of cases, at least half of the mutations in the initial tumor were undetected at recurrence, including driver mutations in TP53, ATRX, SMARCA4, and BRAF; this suggests that recurrent tumors are often seeded by cells derived from the initial tumor at a very early stage of their evolution. Notably, tumors from 6 of 10 patients treated with the chemotherapeutic drug temozolomide (TMZ) followed an alternative evolutionary path to high-grade glioma. At recurrence, these tumors were hypermutated and harbored driver mutations in the RB (retinoblastoma) and Akt-mTOR (mammalian target of rapamycin) pathways that bore the signature of TMZ-induced mutagenesis.
Subject(s)
Antineoplastic Agents, Alkylating/adverse effects , Brain Neoplasms/drug therapy , Brain Neoplasms/pathology , Dacarbazine/analogs & derivatives , Glioma/drug therapy , Glioma/pathology , Neoplasm Recurrence, Local/chemically induced , Neoplasm Recurrence, Local/genetics , Antineoplastic Agents, Alkylating/therapeutic use , Brain/drug effects , Brain/pathology , Brain Neoplasms/genetics , DNA Helicases/genetics , DNA Mutational Analysis , Dacarbazine/adverse effects , Dacarbazine/therapeutic use , Glioma/genetics , Humans , Mutagenesis/drug effects , Neoplasm Grading , Neoplasm Recurrence, Local/drug therapy , Nuclear Proteins/genetics , Proto-Oncogene Proteins B-raf/genetics , Proto-Oncogene Proteins c-akt/genetics , TOR Serine-Threonine Kinases/genetics , Temozolomide , Transcription Factors/genetics , Tumor Suppressor Protein p53/genetics , X-linked Nuclear ProteinABSTRACT
Neuroblastoma, a tumor of peripheral neural crest origin, numbers among the most common childhood cancers. Both amplification of the proto-oncogene MYCN and increased neoangiogenesis mark high-risk disease. Because angiogenesis is regulated by phosphatidylinositol 3-kinase (PI3K), we tested a clinical PI3K inhibitor, NVP-BEZ235, in MYCN-dependent neuroblastoma. NVP-BEZ235 decreased angiogenesis and improved survival in both primary human (highly pretreated recurrent MYCN-amplified orthotopic xenograft) and transgenic mouse models for MYCN-driven neuroblastoma. Using both gain- and loss-of-function approaches, we demonstrated that the antiangiogenic efficacy of NVP-BEZ235 depended critically on MYCN in vitro and in vivo. Thus, clinical PI3K/mammalian target of rapamycin inhibitors drove degradation of MYCN in tumor cells, with secondary paracrine blockade of angiogenesis. Our data demonstrated significantly improved survival in treated animals and suggest that NVP-BEZ235 should be tested in children with high-risk, MYCN-amplified neuroblastoma.
