Abstract 5341: Derangements in HUWE1/c-MYC pathway confer sensitivity to the BET bromodomain inhibitor GS-626510 in uterine cervical carcinoma

Purpose: The prognosis for women with advanced or recurrent cervical cancer (CC) no longer responsive to radiation and/or chemotherapy remains poor. Whole-exome-sequencing (WES) studies have recently reported c-MYC gene amplification and HUWE1 gene mutations in a significant number of CC suggesting the HUWE1/c-MYC pathway as potential therapeutic target. We investigated HUWE1 and c-MYC expression in fresh-frozen CC and the potential activity of the novel BET bromodomain inhibitor GS-626510 (Gilead-Science-Inc.) against primary WES CC-cultures and CC-xenografts. Experimental Design: HUWE1 and c-MYC expression were evaluated by qRT-PCR in a total of 23 CC including 12 fresh frozen tumor tissues and 11 primary cell lines. c-MYC expression was also evaluated by Western-Blot (WB) and fluorescence in situ hybridization (FISH) experiments in all 11 fully sequenced primary CC cell lines. Primary tumors were evaluated for sensitivity to GS-626510 in-vitro using proliferation and viability-assays. siRNA experiments were used to evaluate the effect of HUWE1 silencing on primary CC cell line growth and sensitivity to GS-626510. Finally, the in-vivo activity of GS-626510 was studied in CC-CVX8 mouse-xenografts. Results: Fresh-frozen CC and primary CC cell lines overexpressed c-MYC when compared to normal control tissues (mean ± SEM mRNA values = 7.06 ± 1.17 vs a mean ± SEM = 2.96 ± 0.97, p = 0.01). FISH experiments demonstrated amplification of c-MYC in 9 out of 11 (82%) of the primary CC cell lines. Primary CC cell lines with derangements in the HUWE1/c-MYC pathway were highly sensitive to GS-626510, with a dose-response decrease in cell proliferation and IC50 values ranging from 3 to 57 nM. Silencing of HUWE1 by siRNA significantly increased c-MYC expression as well as CC cell proliferation and enhanced the in vitro sensitivity to GS-626510. Twice daily oral doses of GS-626510 (10 mg/kg) were well tolerated in vivo in animals and highly effective in decreasing tumor-growth (p = 0.004) and increasing survival (p value = 0.004) of mice harboring CC-CVX8 xenografts. Conclusions: Downregulation/inactivation of HUWE1 may increase c-MYC expression and proliferation in primary CC cell lines. GS-626510 may represent a novel, potentially highly effective therapeutic agent against CC overexpressing c-MYC and/or harboring HUWE1 mutations. Clinical studies with BET inhibitor in CC-patients harboring radiation/chemotherapy-resistant disease are warranted. Citation Format: Elena Bonazzoli, Stefania Bellone, Luca Zammataro, Barbara Gnutti, Adele Guglielmi, Silvia Pelligra, Paola Manara, Joan Tymon-Rosario, Burak Zeybek, Chanhee Han, Alessandro D. Santin. Derangements in HUWE1/c-MYC pathway confer sensitivity to the BET bromodomain inhibitor GS-626510 in uterine cervical carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5341.