High PRMT5 levels, maintained by KEAP1 inhibition, drive chemoresistance in high-grade serous ovarian cancer
Harun Ozturk, … , Sandra Orsulic, Mazhar Adli
Harun Ozturk, … , Sandra Orsulic, Mazhar Adli
Published March 17, 2025
Citation Information: J Clin Invest. 2025;135(6):e184283. https://doi.org/10.1172/JCI184283.
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Research Article Cell biology Genetics Oncology

High PRMT5 levels, maintained by KEAP1 inhibition, drive chemoresistance in high-grade serous ovarian cancer

Abstract

Protein arginine methyl transferases (PRMTs) are generally upregulated in cancers. However, the mechanisms leading to this upregulation and its biological consequences are poorly understood. Here, we identify PRMT5, the main symmetric arginine methyltransferase, as a critical driver of chemoresistance in high-grade serous ovarian cancer (HGSOC). PRMT5 levels and its enzymatic activity are induced in a platinum-resistant (Pt-resistant) state at the protein level. To reveal potential regulators of high PRMT5 protein levels, we optimized intracellular immunostaining conditions and performed unbiased CRISPR screening. We identified Kelch-like ECH-associated protein 1 (KEAP1) as a top-scoring negative regulator of PRMT5. Our mechanistic studies show that KEAP1 directly interacted with PRMT5, leading to its ubiquitin-dependent degradation under normal physiological conditions. At the genomic level, ChIP studies showed that elevated PRMT5 directly interacted with the promoters of stress response genes and positively regulated their transcription. Combined PRMT5 inhibition with Pt resulted in synergistic cellular cytotoxicity in vitro and reduced tumor growth in vivo in Pt-resistant patient-derived xenograft tumors. Overall, the findings from this study identify PRMT5 as a critical therapeutic target in Pt-resistant HGSOC cells and reveal the molecular mechanisms that lead to high PRMT5 levels in Pt-treated and chemo-resistant tumors.

Authors

Harun Ozturk, Fidan Seker-Polat, Neda Abbaszadeh, Yasemin Kingham, Sandra Orsulic, Mazhar Adli

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Figure 5

Combinatorial PRMT5 targeting results in synergistic cytotoxicity and apoptosis through excessive DNA damage accumulation.

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Combinatorial PRMT5 targeting results in synergistic cytotoxicity and ap...
(A) Heatmaps show relative cell viability after 6 days of combined treatments. (B) 3D surface plots show Bliss synergy scores for the combined treatments. (C) Line plots show apoptosis rates acquired by IncuCyte live-cell imaging of cells treated with mock, EPZ015666, carboplatin, or their combination. Data are shown as the mean ± SEM (n = 3). P values were determined by 2-tailed, unpaired Student’s t test. (D) Western blots show γ-H2AX, SDMA, and actin levels in cells treated with mock, EPZ015666 (1 μM), carboplatin (10 μM), or their combination for 72 hours. SDMA staining was used as a marker of PRMT5 enzymatic activity. (E) IF images show γ-H2AX staining in cells treated with mock, 1 μM EPZ015666, 10 μM carboplatin, or their combination for 72 hours (original magnification, ×40). (F) Super plot shows the staining intensity calculated in E. Data are shown as the mean ± SEM (n = 3). P values were determined by 1-way ANOVA with Dunnett’s multiple-comparison test. (G) Representative images show individual cell nuclei of carboplatin-resistant OVCAR4 cells treated with mock, 1 μM EPZ015666 (EPZ), 20 μM carboplatin, and their combination for 3 days (left) (original magnification, ×40). Comet tail lengths were quantified and plotted (right). Data are shown as the mean ± SEM (n = 3). P values were quantified by 1-way ANOVA with Dunnett’s multiple-comparison test. (H) Line plot shows tumor growth upon treatment with vehicle GSK591 (50 mg/kg), carboplatin (10 mg/kg), or their combination for approximately 60 days (n = ~8 mice/group). Statistical significance was determined by 2-way ANOVA. Carbo, carboplatin; Res, resistant.