p300-mediated histone H3K18 lactylation promotes mitochondrial ROS accumulation via mitophagy inhibition to potentiate dopamine agonists efficacy in prolactinomas.

Prolactinomas are the most common functional pituitary adenomas, and dopamine agonists (DAs) are the first-line therapy; however, approximately 10-30% of patients develop resistance, highlighting the need for effective sensitization strategies. In clinical specimens, we observed reduced p300 expression in tumors with poor DA responsiveness, and p300 levels were inversely associated with DA dosage. In cellular and xenograft models, DAs decreased p300 by suppressing the cAMP/PKA/CREB pathway. We therefore tested whether upregulating or activating p300 could enhance DA efficacy and investigated the underlying mechanism using immunohistochemistry, immunofluorescence, Western blot, genetic manipulations, RNA sequencing, CUT&Tag, ChIP-qPCR, Seahorse metabolic assays, flow cytometry, co-immunoprecipitation, and GST pull-down assays. Augmenting p300 markedly potentiated DA-induced antitumor effects in vitro and in vivo, a process accompanied by the elevated histone H3K18 lactylation (H3K18la). Mechanistically, p300-dependent H3K18la promoted transcriptional upregulation of Ndufs7 and Washc1. NDUFS7 induction was associated with increased mitochondrial ROS, whereas WASH1 bound the ubiquitin-associated domain of p62, impairing recognition and clearance of damaged mitochondria, suppressing mitophagy, and thereby sustaining mitochondrial ROS accumulation and apoptosis. Moreover, YF-2, a p300 HAT-domain activator, synergized with DAs to inhibit tumor growth in MMQ and AtT-20 cells. Together, these data identify a p300-H3K18la-NDUFS7/WASH1 axis that links mitophagy inhibition to mitochondrial ROS accumulation and provide a mechanistic rationale for targeting p300 as an adjuvant approach to improve DAs efficacy in prolactinomas.