TWIST1 bridges p53 and MDM2 and impairs the efficacy of MDM2 inhibitors

BACKGROUND: Tumors that retain wild-type TP53 and rely on MDM2 overexpression to dampen the p53 response were considered prime candidates for therapies based on MDM2 inhibitors (MDM2i). However, clinical trials to date have been disappointing, with limited improvements in progression-free survival, pointing to the existence of intrinsic resistance mechanisms. Building on our previous work demonstrating that TWIST1 attenuates the p53 response in sarcomas, we hypothesized that TWIST1 plays a role in modulating MDM2i efficacy. METHODS: RNA-sequencing data were integrated with cytotoxicity measurements across a large panel of TP53 wild-type sarcoma cell models. Perturbation experiments were performed using shRNA or CRISPR/Cas9-mediated inhibition, as well as ectopic TWIST1 expression. Cell viability, pathway activation, and transcriptional profile following MDM2i treatment were evaluated in TWIST1-proficient and -deficient models. Co-precipitations, TurboID, molecular docking experiments, and in vitro and in vivo functional assays were employed to characterize the interplay between TWIST1, p53, and MDM2. RESULTS: TWIST1 expression correlated with reduced sensitivity to multiple MDM2i. TWIST1 inhibition enhanced p53 pathway activation and cell death in response to MDM2i, while TWIST1 overexpression conferred resistance. Mechanistically, we found that TWIST1 directly binds both p53 and MDM2, forming a trimeric complex that facilitates p53:MDM2 interaction, thereby promoting p53 degradation and limiting MDM2i efficacy. Notably, harmine, a compound that promotes TWIST1 degradation, phenocopied the effects of TWIST1 genetic inhibition in augmenting MDM2i sensitivity. CONCLUSION: TWIST1 confers resistance to MDM2i in TP53 wild-type sarcomas. Targeting TWIST1 restores p53 pathway activation and sensitizes sarcoma cells to MDM2 blockade, establishing TWIST1 as a promising predictive biomarker and therapeutic vulnerability for improving MDM2i efficacy.