Abstract 2033: Rigosertib promotes anti-tumor activity of cancer cells via CETSA revealed novel targets and activates NLRP3-dependent inflammatory responses
Authors: Kechagioglou Petros , Dupont Camille , Yurugi Hajime , Chernobrovkin Alexey , Romero Rossana , Tweedell Rebecca , Kanneganti Thirumala-Devi , Cosenza Stephen , Fruchtman Steven M. , Rajalingam Krishnaraj 
Published: March 2024

Abstract
Background: Rigosertib (ON 01910.Na) is considered a promising anticancer agent due to its ability to inhibit multiple disease signaling pathways, including RAS-MAPK signaling. Rigosertib is in a Phase 2 program in advanced squamous cell carcinoma complicating recessive dystrophic epidermolysis bullosa (RDEB-associated SCC) (NCT03786237, NCT04177498), and a Phase 2 trial in combination with pembrolizumab in patients with metastatic melanoma (NCT05764395). The aim of our study was to further elucidate the mechanism of action and to identify potential novel targets engaged by rigosertib.
Methods: A variety of biochemical, molecular and cell biological assays were performed to characterize the binding of rigosertib to previously proposed targets and its effect on RAS-MAPK signaling and tumor cell survival. A mass spectrometry-based Cellular Thermal Shift Assay (CETSA-MS) was conducted to identify potential new protein targets of rigosertib. Time-lapse microscopy was used for detection of ROS levels and tubulin polymerization in rigosertib treated lung cancer cells. Bone Marrow Derived Macrophages (BMDM) collected from C57/BL6 mice and human lung cancer organoids were treated with rigosertib and the cell death was determined by flow cytometry.
Results: Comparative CETSA profiling of rigosertib and colchicine, a classical tubulin depolymerizing agent, reveals unique targets of rigosertib in multiple tumor cell types. We identify two ROS-related proteins, ERO1A and NQO2 that potentially contribute to the induction of ROS-dependent JNK activation. Fluorescence live-cell imaging confirms the effect of ERO1A and NQO2 on rigosertib induced ROS generation. NEK7, a relevant protein for microtubule organization, is another potential target for rigosertib. NEK7 knock-down reveals reduced microtubule depolymerization in rigosertib treated lung cancer cells. While we confirm that rigosertib might affect microtubules at higher concentrations, the main cellular target(s) responsible for the induction of stress and JNK-mediated inhibition of RAS-RAF-MEK signaling needs to be further characterized. Rigosertib affects the tumor immune environment by activating NLRP3-dependent inflammatory responses and Caspase-1 to trigger IL-1β and IL-18 secretion in THP1 cells, as well as in human cancer organoids, and in wild-type, Casp1/11−/−, Asc−/− and Nlrp3−/− BMDMs.
Conclusion: These findings indicate that rigosertib may represent an effective compound for inhibition of RAS-MAPK signaling through ROS-mediated JNK activation. The rigosertib-dependent mechanism for NLRP3 activation suggests a reprogramming of the tumor immune environment which may contribute to the synergistic effect seen with immune checkpoint inhibitors pre-clinically and clinically. Clinical trials in several difficult-to-treat cancers continue.
Citation Format: Petros Kechagioglou, Camille Dupont, Hajime Yurugi, Alexey Chernobrovkin, Rossana Romero, Rebecca Tweedell, Thirumala-Devi Kanneganti, Stephen Cosenza, Steven M. Fruchtman, Krishnaraj Rajalingam. Rigosertib promotes anti-tumor activity of cancer cells via CETSA revealed novel targets and activates NLRP3-dependent inflammatory responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2033.