ESR1 and breast carcinoma: Knockdown of MYST3 in HR-positive breast cancer xenografts leads to significant tumor regression and increased progression-free survival (PFS), corroborating in vitro studies that found that the genetic ablation of MYST3 significantly reduces cell growth in HR-positive breast cancer cell lines [70]. These data suggest that further exploration of MYST3-targeting for the treatment of MYST3-high ER-positive/HER2-negative breast cancers is warranted and may benefit endocrine therapy-resistant patients.