Direct Targeting of <i>MYCN</i> Gene Amplification by Site-Specific DNA Alkylation in Neuroblastoma.

Abstract

Amplification of <i>MYCN</i> plays a pivotal role in multiple types of tumors and correlates with poor prognosis in high-risk neuroblastoma. Despite recent advances in the treatment of neuroblastoma, no approaches directly target the master oncogene <i>MYCN</i>. Difficulties in targeting the MYCN protein inspired us to develop a new gene-level-inhibitory strategy using a sequence-specific gene regulator. Here, we generated a <i>MYCN</i>-targeting pyrrole-imidazole (PI) polyamide, MYCN-A3, which directly binds to and alkylates DNA at homing motifs within the <i>MYCN</i> transcript. Pharmacologic suppression of MYCN inhibited the proliferation of cancer cells harboring <i>MYCN</i> amplification compared with <i>MYCN</i> nonamplified cancer cells. In neuroblastoma xenograft mouse models, MYCN-A3 specifically downregulated MYCN expression and suppressed tumor progression with no detectable adverse effects and resulted in prolonged overall survival. Moreover, treatment with MYCN-A3, but not <i>MYCN</i> nontargeting PI polyamide, precipitated a copy number reduction of <i>MYCN</i> in neuroblastoma cells with <i>MYCN</i> amplification. These findings suggest that directly targeting <i>MYCN</i> with MYCN-A3 is a novel therapeutic approach to reduce copy number of the <i>MYCN</i> gene for <i>MYCN</i>-amplified neuroblastoma. SIGNIFICANCE: This study presents a novel approach to drugging an amplified oncogene by showing that targeting gene amplification of <i>MYCN</i> suppresses MYCN expression and neuroblastoma growth.