Abstract 2436: The multi-faceted Integrator complex in Notch-driven esophageal cancer
Authors: Shersher Elena , Alvarez-Trotta Annamil , Lahiry Mohini , Diluvio Giulia , Shiekhattar Ramin , Capobianco Anthony J. 
Published: April 2023

Abstract
Esophageal adenocarcinoma (EAC) is an aggressive type of cancer with a 5-year survival rate of less than 20%, which underscores the urgent need for new and effective targeted therapies. Treatment failures are often associated with activated Notch signaling and more than 70% of EAC cases possess aberrantly activated Notch. Recently, we identified the Integrator complex (INT), a multi-subunit assembly, as a new co-activator of Notch. In general transcription, INT is known to regulate RNAPII activity. Our previous study showed that INT is important in EAC. The INT complex initiates Notch-mediated transcription via RNAPII activation, and it is required for cell growth and proliferation in EAC. INT is also involved in cell cycle regulation and apoptosis. However, the functions of various INT subunits in EAC and their importance in Notch signaling remain unknown. Here, we investigate the importance of distinct INT subunits in Notch-mediated transcription as well as EAC tumor cell viability, growth and proliferation. Furthermore, we examine whether INT knockdown sensitizes EAC to the treatments with anti-cancer compounds.
We evaluated the depletion effects of several INT subunits in EAC using RNA interference and various assays. All gene knockdowns were confirmed by western blotting and/or RT-qPCR. When we examined the depletion effects of INT in Notch-driven EAC, we observed that the knockdown of some but not all of the INT subunits decreased the expression of Notch target genes as determined by RT-qPCR. This indicates the importance of these specific INT subunits in Notch signaling. We further evaluated the knockdown effects on cell viability, growth and proliferation utilizing a combination of flow cytometry, western blotting, CCK8 and colony formation assays. We observed a decrease in cell viability and inhibition of cell growth and proliferation in EAC cells with the knockdown of specific but not all INT complex subunits. These results indicate that only specific INT subunits are important in Notch-dependent EAC, and these INT subunits may provide a potential therapeutic axis. Furthermore, we determined that the knockdown of INT sensitized EAC cells to other drug treatments exhibiting synergistic effects.
In conclusion, EAC is an aggressive type of cancer with overactivated Notch and poor clinical outcomes. Here, we determined that several subunits of the INT complex may present a therapeutic opportunity in Notch-driven EAC as these subunits are important in Notch-mediated gene expression, EAC cell viability, and cell growth and proliferation.
Citation Format: Elena Shersher, Annamil Alvarez-Trotta, Mohini Lahiry, Giulia Diluvio, Ramin Shiekhattar, Anthony J. Capobianco. The multi-faceted Integrator complex in Notch-driven esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2436.