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Supplementary Figure S7 from Selective CDK7 Inhibition Suppresses Cell Cycle Progression and MYC Signaling While Enhancing Apoptosis in Therapy-resistant Estrogen Receptor–positive Breast Cancer

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posted on 2024-05-01, 07:20 authored by Cristina Guarducci, Agostina Nardone, Douglas Russo, Zsuzsanna Nagy, Capucine Heraud, Albert Grinshpun, Qi Zhang, Allegra Freelander, Mathew Joseph Leventhal, Avery Feit, Gabriella Cohen Feit, Ariel Feiglin, Weihan Liu, Francisco Hermida-Prado, Nikolas Kesten, Wen Ma, Carmine De Angelis, Antonio Morlando, Madison O'Donnell, Sergey Naumenko, Shixia Huang, Quang-Dé Nguyen, Ying Huang, Luca Malorni, Johann S. Bergholz, Jean J. Zhao, Ernest Fraenkel, Elgene Lim, Rachel Schiff, Geoffrey I. Shapiro, Rinath Jeselsohn

Effect of samuraciclib on PalboS and PalboR T47D cells.

Funding

Fondazione AIRC per la ricerca sul cancro ETS (AIRC)

Fondazione Cassa di Risparmio di Firenze (Fondazione CR Firenze)

National Cancer Institute (NCI)

United States Department of Health and Human Services

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Massachusetts Institute of Technology Department of Brain and Cognitive Sciences

Cancer Prevention and Research Institute of Texas (CPRIT)

Dana-Farber Cancer Institute (DFCI)

Duncan Donuts

American-Italian Cancer Foundation (AICF)

History

ARTICLE ABSTRACT

Resistance to endocrine therapy (ET) and CDK4/6 inhibitors (CDK4/6i) is a clinical challenge in estrogen receptor (ER)-positive (ER+) breast cancer. Cyclin-dependent kinase 7 (CDK7) is a candidate target in endocrine-resistant ER+ breast cancer models and selective CDK7 inhibitors (CDK7i) are in clinical development for the treatment of ER+ breast cancer. Nonetheless, the precise mechanisms responsible for the activity of CDK7i in ER+ breast cancer remain elusive. Herein, we sought to unravel these mechanisms. We conducted multi-omic analyses in ER+ breast cancer models in vitro and in vivo, including models with different genetic backgrounds. We also performed genome-wide CRISPR/Cas9 knockout screens to identify potential therapeutic vulnerabilities in CDK4/6i-resistant models. We found that the on-target antitumor effects of CDK7 inhibition in ER+ breast cancer are in part p53 dependent, and involve cell cycle inhibition and suppression of c-Myc. Moreover, CDK7 inhibition exhibited cytotoxic effects, distinctive from the cytostatic nature of ET and CDK4/6i. CDK7 inhibition resulted in suppression of ER phosphorylation at S118; however, long-term CDK7 inhibition resulted in increased ER signaling, supporting the combination of ET with a CDK7i. Finally, genome-wide CRISPR/Cas9 knockout screens identified CDK7 and MYC signaling as putative vulnerabilities in CDK4/6i resistance, and CDK7 inhibition effectively inhibited CDK4/6i-resistant models. Taken together, these findings support the clinical investigation of selective CDK7 inhibition combined with ET to overcome treatment resistance in ER+ breast cancer. In addition, our study highlights the potential of increased c-Myc activity and intact p53 as predictors of sensitivity to CDK7i-based treatments.

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