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Targeting p300 Reverses Acidic Microenvironment-Induced PARP Inhibitor Resistance
Kaixin Cheng1, Hao Nie1, Wei Zhou2
1The University of Texas MD Anderson Cancer Center Houston, TX United States.
Cancer Research
|July 17, 2026
Summary
Tumor acidosis promotes resistance to Poly(ADP-ribose) polymerase inhibitors (PARPi) in ovarian cancer by activating p300. Inhibiting p300 may overcome this resistance, improving PARPi efficacy.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Poly(ADP-ribose) polymerase inhibitors (PARPi) are crucial for epithelial ovarian cancer (EOC) treatment.
- Therapeutic resistance, potentially linked to tumor acidosis, limits PARPi efficacy.
Purpose of the Study:
- To investigate the role of tumor acidosis in mediating PARPi resistance in EOC.
- To identify molecular targets for overcoming acidosis-induced PARPi resistance.
Main Methods:
- Utilized CRISPR-Cas9 screening to identify mediators of acidosis-induced resistance.
- Investigated the signaling axis (ERK-p300-PARP1) involved in resistance.
- Assessed the therapeutic potential of p300 inhibition in combination with PARPi in EOC models.
Main Results:
- Acidic tumor microenvironment enhances DNA repair and reduces PARP1 trapping, leading to PARPi resistance.
- p300 was identified as a key mediator, acetylating PARP1 (PARP1 K505Ac) and preventing PARP1 trapping.
- Elevated PARP1 K505Ac correlates with clinical PARPi resistance and poor survival.
- Pharmacologic p300 inhibition synergized with PARPi to inhibit tumor growth.
Conclusions:
- The acidic tumor microenvironment drives PARPi resistance in EOC via a p300-dependent mechanism.
- p300 is a druggable target that can enhance PARPi efficacy by overcoming acidosis-induced resistance.
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