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. https://doi.org/10.1172/JCI134132.
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Research Article Oncology

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 1

CDK9 and CDK2 are selectively essential for MYCN-amplified NB.

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CDK9 and CDK2 are selectively essential for MYCN-amplified NB. (A) GI50 ...
(A) GI50 of CCT68127 and CYC065 in a panel of NB cells. Cells were treated for 8 hours, washed off, and replaced with normal growth medium. GI50 values (μM) were calculated after 72 hours (n = 3). Significance was calculated using 2-tailed, unpaired Student’s t test. (B) Kelly cells were treated with CYC065 or CCT68127 for 0.5 to 6 hours (1 μM). Immunoblots illustrate expression of PARP cleavage (n = 2). (C) Immunoblots showing expression of p-RNAPII-Ser2 and p-RNAPII-Ser5, MYCN, and MCL-1 at the indicated times after treatment with CYC065 (1–2 μM, 1–8 hours) in Kelly cells (n = 2). (D) Flow cytometry analysis showing sub-G1 level of MYCN-amplified (Kelly, BE(2)C) and nonamplified (SH-EP, SK-N-AS) cells in response to CYC065 (1 μM; 8 hours). Data are represented as mean ± SD of 3 independent experiments. (E) Kelly cells were treated with CYC065 or CCT68127 at the indicated concentrations (0.5–2 μM) for 6 hours. Immunoblots depict expression of cleaved caspase-3 (n = 2).