Research Professor University of California, San Diego (UCSD) San Diego, California, United States
Abstract: Pre-clinical targeting of cancer stem cells via ADAR1 inhibition with Rebecsinib in TNBC
Wenxue Ma1, Jessica Pham1, Claire Engstrom1, Inge van der Werf1, Emma Klacking1, Neha Katragadda1, Patrick Chang1, Kendale Wirtjes1, Sheldon Morris1, James La Clair2, Anna Khachatrian3, Peggy Wentworth1, Michael Burkart2, Catriona Jamieson1*
1 Department of Medicine, Sanford Stem Cell Institute, UC San Diego, La Jolla, CA 92093, USA. 2 Department of Chemistry and Biochemistry, UC San Diego, La Jolla, CA 92093, USA. 3 Scripps MD Anderson Cancer Center, La Jolla, CA, 92037, USA
Correspondence: cjamieson@health.ucsd.edu
Background: Cancer stem cells (CSCs) promote relapse and therapy resistance in aggressive cancers. ADAR1, an RNA editing enzyme, supports CSC survival and immune evasion through splicing and self-renewal. Rebecsinib (17S-FD-895), a selective splicing modulator, inhibits ADAR1 to block these pathways. We evaluated its effects using xenografts, spaceflight-based models, and single-cell RNA sequencing (scRNA-seq).
Methods: CD34⁺ hematopoietic stem/progenitor cells (HSPCs) were co-cultured with ADAR1-reporter metastatic breast cancer (MBC) cells under spaceflight and ground conditions aboard Axiom Mission 3. ADAR1 activity and CSC clustering were assessed via live-cell imaging. scRNA-seq of six MBC samples (including space-exposed) profiled heterogeneity and ADAR1 expression. Rebecsinib (10 mg/kg IV or 15 mg/kg oral, twice weekly × 2 weeks) was tested in TNBC CDX and PDX models (MBC009, MBC013). CSC burden was evaluated via IVIS imaging and flow cytometry (CD44⁺, ADAR1⁺).
Results: Spaceflight increased ADAR1 activity and CSC clustering, indicating niche reprogramming under microgravity. scRNA-seq showed expansion of myeloid progenitors and CD44⁺CD47⁺ CSC-like cells with elevated ADAR1 linked to immune escape and transcriptomic plasticity. Rebecsinib significantly reduced ADAR1⁺ and CD44⁺ CSCs while sparing normal HSPCs.
Conclusion: Rebecsinib effectively targets CSCs by inhibiting ADAR1-mediated RNA editing. Spaceflight models highlight microgravity-induced CSC plasticity and ADAR1 dynamics, supporting Rebecsinib as a promising CSC-directed therapy. Keywords: Cancer stem cells, ADAR1, Rebecsinib, RNA editing, single-cell RNA sequencing, spaceflight, TNBC.
Funding Source: This work was supported by Research Foundation, and NASA NRA NNJ13ZBG001N.
