Data from Inhibition of BET Bromodomain Proteins with GS-5829 and GS-626510 in Uterine Serous Carcinoma, a Biologically Aggressive Variant of Endometrial Cancer

Stefania Bellone,Chanhee Han,Gulden Menderes,Salvatore Lopez,Francesco Riccio,Paola Manara,Masoud Azodi,Serena Wong,Babak Litkouhi,Elena Bonazzoli,Gary Altwerger,Elena Ratner,Peter E Schwartz,Ghanshyam Yadav,Gloria S Huang,Luca Zammataro,Federica Predolini,Emiliano Cocco,Joseph Schlessinger,Alessandro D Santin,Pei Hui,Francesca Pettinella,Anna Maria Bianchi ,Natália Buza ,Aránzazu Manzano ,Dan‐Arin Silasi

doi:10.1158/1078-0432.c.6527471

Abstract

<div>AbstractPurpose: Uterine serous carcinoma (USC) is a rare and aggressive variant of endometrial cancer. Whole-exome sequencing (WES) studies have recently reported c-Myc gene amplification in a large number of USCs, suggesting c-Myc as a potential therapeutic target. We investigated the activity of novel BET bromodomain inhibitors (GS-5829 and GS-626510, Gilead Sciences Inc.) and JQ1 against primary USC cultures and USC xenografts.Experimental Design: We evaluated c-Myc expression by qRT-PCR in a total of 45 USCs including fresh-frozen tumor tissues and primary USC cell lines. We also performed IHC and Western blot experiments in 8 USC tumors. USC cultures were evaluated for sensitivity to GS-5829, GS-626510, and JQ1 in vitro using proliferation, viability, and apoptosis assays. Finally, the in vivo activity of GS-5829, GS-626510, and JQ1 was studied in USC-ARK1 and USC-ARK2 mouse xenografts.Results: Fresh-frozen USC and primary USC cell lines overexpressed c-Myc when compared with normal tissues (P = 0.0009 and 0.0083, respectively). High c-Myc expression was found in 7 of 8 of primary USC cell lines tested by qRT-PCR and 5 of 8 tested by IHC. In vitro experiments demonstrated high sensitivity of USC cell lines to the exposure to GS-5829, GS-626510, and JQ1 with BET inhibitors causing a dose-dependent decrease in the phosphorylated levels of c-Myc and a dose-dependent increase in caspase activation (apoptosis). In comparative in vivo experiments, GS-5829 and/or GS-626510 were found more effective than JQ1 at the concentrations/doses used in decreasing tumor growth in both USC-ARK1 and USC-ARK2 mouse xenograft models.Conclusions: GS-5829 and GS-626510 may represent novel, highly effective therapeutics agents against recurrent/chemotherapy-resistant USC-overexpressing c-Myc. Clinical studies with GS-5829 in patients with USC harboring chemotherapy-resistant disease are warranted. Clin Cancer Res; 24(19); 4845–53. ©2018 AACR.</div>

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