TRIM24 as therapeutic target in endocrine treatment resistant breast cancer (RNA-Seq)

While ERα+ breast cancer treatment is considered effective, resistance to endocrine therapy is common. Since in therapy-resistance tumors, ERα is still the main driver, alternative therapeutic strategies are needed to disrupt ERα transcriptional activity. In this work, we describe TRIM24 as a key player of the ERα transcriptional complex. TRIM24 interacts with ERα and other well-known ERα-cofactors to facilitate ERα chromatin interactions, and allows for maintenance of active histone marks including H3K23ac and H3K27ac. Consequently, genetic perturbation of TRIM24 abrogates ERα-driven transcriptional programs and reduces tumor cell proliferation capacity. Using a recently-developed PROTAC targeting TRIM24, ERα-driven transcriptional output and growth was blocked, effectively treating not only endocrine-responsive cell lines, but also drug resistant derivates thereof as well as cell line models bearing activating ESR1 point mutations. Finally, using human tumor-derived organoid models, we could show efficacy of TRIM24 PROTAC in the endocrine responsive and resistant setting, with no response in ERα-negative organoids. Overall, our study positions TRIM24 as a central component for integrity and activity of the ERα transcriptional complex, with PROTAC-mediated perturbation of TRIM24 as promising therapeutic avenue in the treatment of primary and endocrine resistance breast cancer.