A. L. Gustafson, S. Nance, B. Gryder, N. A. M. Shendy, L. Wick, G. McKay-Corkum, K. E. Ritter, S. C. Purdy, A. R. Wolin, S. R. Rosenbaum, S. Mathavarajah, N. A. Demelfi, Y. Wang, Y. Zhang, M. Zimmerman, A. Kavirayani, E. A. Citarella, V. J. Ebegboni, J. W. Hardin, A. LaVeck, X. Wang, N. Dharia, A. L. Hong, G. Kugener, J. S. Boehm, J. A. Roth, J. Khan, F. Vazquez, K. Artinger, R. Zhao, D. M. Langenau, J. Qi, K. Stegmaier, B. Abraham, H. Ford, A. D. Durbin
Rhabdomyosarcoma (RMS) is a multi-subtype, high-risk pediatric sarcoma with a low mutational burden. The mutations found in RMS often alter genes involved in transcriptional control. Approaches to target dysregulated RMS transcription have remained elusive. Here, we develop a novel approach to target RMS transcription comprising simultaneous targeting of two distinctly acting transcriptional co-activators. We discover a common identity-controlling pan-RMS core regulatory circuit (CRC) composed of oncogenic and lineage-specific myogenic master transcription factors (mTFs). Using a super-enhancer-based reporter screen, we identify the EP300/CBP inhibitor A485 as a potent inhibitor of the pan-RMS CRC, though with efficacy-limiting toxicities. To enhance efficacy, we identify the mTF-binding co-activator EYA2 as a co-factor of this pan-RMS CRC and exploit a new second-generation EYA1/2 inhibitor, LG1-34, to disrupt its function. Combined co-activator inhibition inactivates the CRC and synergistically reduces RMS growth. This strategy dually targets CRC-associated co-activators to cooperatively suppress the RMS transcriptome and enforce cell death.