Multi-omics analyses identify EZH2 as a central driver in rhabdomyosarcoma radioresistance and highlight Tazemetostat as an effective radiosensitizer in vitro and in vivo PMID: 42225614

ADC Targets in Oncology

2026-04-10

Multi-omics analyses identify EZH2 as a central driver in rhabdomyosarcoma radioresistance and highlight Tazemetostat as an effective radiosensitizer in vitro and in vivo

Cell Death Dis. 2026 Jun 1. doi: 10.1038/s41419-026-08938-0.

Matteo Cassandri ¹ ² , Antonella Porrazzo ³ , Simona Camero ¹ ⁴ , Silvia Pomella ² ⁵ , Valeria Manzi ³ ⁶ , Francesca Vulcano ⁶ , Luisa Milazzo ⁶ , Francesca Pedini ⁶ , Deborah Pajalunga ⁶ , Andrea Casagrande ⁶ , Giada Mele ³ , Valentina Lulli ⁶ , Enrico Romano ⁷ , Michele Signore ⁸ , Massimo Spada ⁹ , Maria Teresa D'Urso ⁹ , Silvia Codenotti ¹⁰ , Alessandro Fanzani ¹⁰ , Annunziata Mauro ¹¹ , Giovanna Marchese ¹² ¹³ , Simone Sidoli ¹⁴ , Giovanni Luca Gravina ¹⁵ , Giovanni Barillari ⁵ , Franco Locatelli ² ¹⁶ , Francesca Megiorni ¹⁷ ¹⁸ , Rossella Rota ² , Francesco Marampon ¹⁹ ²⁰

Affiliations

1. Department of Experimental Medicine, "Sapienza" University of Rome, Rome, Italy.
2. Department of Hematology/Oncology, Cell and Gene Therapy, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
3. Department of Radiological, Oncological and Pathological Sciences, "Sapienza" University of Rome, Policlinico Umberto I, Rome, Italy.
4. Department of Life Sciences, Health and Health Professions, Link Campus University, Rome, Italy.
5. Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Rome, Italy.
6. Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.
7. Department of Sense Organs, Sapienza University of Rome, Rome, Italy.
8. RPPA Unit, Proteomics Area, Core Facilities, Istituto Superiore di Sanità, Rome, Italy.
9. Center of Animal Research and Welfare, Istituto Superiore di Sanità, Rome, Italy.
10. Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
11. Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy.
12. Genomix4Life S.r.l, Baronissi, Italy.
13. Genome Research Center for Health, CRGS, Baronissi, Italy.
14. Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, USA.
15. Department of Biotechnological and Applied Clinical Sciences, Radiation Oncology Unit, Ospedale San Salvatore, University of L'Aquila, L'Aquila, Italy.
16. Department of Life Sciences and Public Health, Catholic University of the Sacred Heart, Rome, Italy.
17. Department of Experimental Medicine, "Sapienza" University of Rome, Rome, Italy. [email protected].
18. Department of Well-being, Health and Environmental Sustainability, Sapienza University of Rome, Rieti, Italy. [email protected].
19. Department of Radiological, Oncological and Pathological Sciences, "Sapienza" University of Rome, Policlinico Umberto I, Rome, Italy. [email protected].
20. Department of Well-being, Health and Environmental Sustainability, Sapienza University of Rome, Rieti, Italy. [email protected].

Abstract

Rhabdomyosarcoma (RMS), a pediatric soft tissue sarcoma, comprises two major subtypes: fusion-positive (FP), driven by PAX3/7-FOXO1 fusions, and fusion-negative (FN), often harboring Ras pathway mutations. High-risk RMS exhibits intrinsic resistance to radiotherapy (RT), posing a significant clinical hurdle. Emerging evidence implicates EZH2, the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2), in promoting RT resistance through gene silencing via H3K27me3. To dissect the molecular basis of RMS radioresistance, we employed an integrative multi-omics approach encompassing phosphoproteomics and transcriptomics. Radioresistant RMS cell models (RMS^CRR) displayed enhanced Cancer stem cell features, evasion of RT-induced G2/M arrest, and reduced Apoptosis compared to their parental counterparts (RMS^PR). Phosphoproteomic profiling revealed activation of prosurvival and proliferative pathways across both FN and FP subtypes. Transcriptomic analysis identified a robust downregulation of EZH2 target genes, with distinct gene sets modulated in FN-RMS^CRR versus FP-RMS^CRR cells, highlighting subtype-specific epigenetic rewiring. These multi-omics findings pointed to hyperactive PRC2/EZH2 signaling as a driver of radioresistance. Therapeutically, combining the EZH2 Inhibitor Tazemetostat (TZM) with RT significantly impaired clonogenic survival, enhanced G2/M arrest, and promoted Apoptosis in both RMS^PR and RMS^CRR cells. In vivo, RT and TZM co-treatment fully suppressed FN-RMS^PR tumor growth and delayed FP-RMS^PR progression. Notably, TZM monotherapy inhibited tumor growth in both FN- and FP-RMS^CRR xenografts, uncovering a therapy-induced vulnerability. Our integrative multi-omics analysis reveals EZH2-dependent molecular programs underpinning radioresistance and supports EZH2 targeting as a rational radiosensitizing and therapeutic strategy in RMS, including recurrent and RT-refractory disease.