Orally bioavailable CDK9/2 inhibitor shows mechanism-based therapeutic potential in MYCN-driven neuroblastoma
Evon Poon, … , Charles Y. Lin, Louis Chesler
Evon Poon, … , Charles Y. Lin, Louis Chesler
Published October 5, 2020
Citation Information: J Clin Invest. 2020;130(11):5875-5892. https://doi.org/10.1172/JCI134132.
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Orally bioavailable CDK9/2 inhibitor shows mechanism-based therapeutic potential in MYCN-driven neuroblastoma

Abstract

The undruggable nature of oncogenic Myc transcription factors poses a therapeutic challenge in neuroblastoma, a pediatric cancer in which MYCN amplification is strongly associated with unfavorable outcome. Here, we show that CYC065 (fadraciclib), a clinical inhibitor of CDK9 and CDK2, selectively targeted MYCN-amplified neuroblastoma via multiple mechanisms. CDK9 — a component of the transcription elongation complex P-TEFb — bound to the MYCN-amplicon superenhancer, and its inhibition resulted in selective loss of nascent MYCN transcription. MYCN loss led to growth arrest, sensitizing cells for apoptosis following CDK2 inhibition. In MYCN-amplified neuroblastoma, MYCN invaded active enhancers, driving a transcriptionally encoded adrenergic gene expression program that was selectively reversed by CYC065. MYCN overexpression in mesenchymal neuroblastoma was sufficient to induce adrenergic identity and sensitize cells to CYC065. CYC065, used together with temozolomide, a reference therapy for relapsed neuroblastoma, caused long-term suppression of neuroblastoma growth in vivo, highlighting the clinical potential of CDK9/2 inhibition in the treatment of MYCN-amplified neuroblastoma.

Authors

Evon Poon, Tong Liang, Yann Jamin, Susanne Walz, Colin Kwok, Anne Hakkert, Karen Barker, Zuzanna Urban, Khin Thway, Rhamy Zeid, Albert Hallsworth, Gary Box, Marli E. Ebus, Marco P. Licciardello, Yordan Sbirkov, Glori Lazaro, Elizabeth Calton, Barbara M. Costa, Melanie Valenti, Alexis De Haven Brandon, Hannah Webber, Nicolas Tardif, Gilberto S. Almeida, Rossitza Christova, Gunther Boysen, Mark W. Richards, Giuseppe Barone, Anthony Ford, Richard Bayliss, Paul A. Clarke, Johann De Bono, Nathanael S. Gray, Julian Blagg, Simon P. Robinson, Suzanne A. Eccles, Daniella Zheleva, James E. Bradner, Jan Molenaar, Igor Vivanco, Martin Eilers, Paul Workman, Charles Y. Lin, Louis Chesler

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Figure 6

CYC065 and CCT68127 inhibit MYCN-driven NB in vivo.

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CYC065 and CCT68127 inhibit MYCN-driven NB in vivo. Effects of CYC065 on...
Effects of CYC065 on the growth and survival of Kelly (MYCN amplified) (A) and SK-N-AS (nonamplified) (B) NB xenografts in mice. Data are expressed as mean ± SEM (log-rank Mantel-Cox test with a 5% level of significance). (C) Waterfall plot documenting relative changes in tumor volume at day 7 in the TH-MYCN GEM model. All treatment arms versus control: P < 0.001, 2-tailed, unpaired Student’s t test incorporating Bonferroni’s correction (n = 5) with a 1% level of significance. Kaplan-Meier plot documenting survival of TH-MYCN mice. All treatment arms versus control: P < 0.01; and CYC065 or CCT68127 alone versus combination with temozolomide: P = 0.02 (log-rank Mantel-Cox test with 5% level of significance. (D) Waterfall plot documenting relative changes in tumor volume at day 7 in the TH-ALKF1174L/MYCN GEM model: P < 0.001, 2-tailed unpaired Student’s t test with 5% level of significance. Kaplan-Meier plot documenting survival of TH-ALKF1174L/MYCN mice: P < 0.01, log-rank Mantel-Cox test with a 5% level of significance) (E) Quantitative RT-PCR analyses showing levels of murine and human MYCN RNA in the TH-ALKF1174L/MYCN tumor following treatment with CYC065 for 3 days (n = 3). (F) Representative images and quantitative analysis of H&E and immunohistochemical staining for cleaved capsase-3 and MYCN in the harvested tumors from A and B. Scale bar: 50 μm. (G and H) Immunoblot analyses of individual tumors from TH-MYCN model treated with CYC065 for 1 or 3 days. Data are represented as mean ± SD of 4 independent experiments. Two-tailed unpaired Student’s t test with Benjamini and Hochberg correction for multiple comparisons. *P < 0.05; **P < 0.01. (I) Parametric functional MRI maps showing reduction of tumor spin lattice relaxation time T1 and an increase in ADC 24 hours after treatment with 50 mg/kg CYC065, and their corresponding H&E staining. Scale bar: 100 μm. (J) Correlation between native tumor T1 measured 24 hours after treatment with 50 mg/kg CYC065 or CCT68127 (percentage of pretreatment value) and relative changes in tumor volume following treatment with 50 mg/kg CYC065 or CCT68127.