Qiu Zhaojun, Sigh Deepika, Liu Yujie, Prasad Chandra B, Bean Nichalos, Yan Chunhong, Li Zaibo, Zhang Xiaoli, Narla Goutham, DiFeo Analisa, Wang Qi-En, Zhang Junran
Department of Radiation Oncology, The James Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio-43210, United States.
Georgia Cancer Center, Augusta University Medical College, 1410 Laney Walker Blvd., CN-2134, Augusta, Georgia-30912, United States.
Theranostics. 2024 Nov 4;14(19):7450-7469. doi: 10.7150/thno.96879. eCollection 2024.
High-grade serous ovarian cancer (HGSOC), the most lethal epithelial ovarian cancer subtype, faces persistent challenges despite advances in the therapeutic use of PARP inhibitors. Thus, innovative strategies are urgently needed to improve survival rates for this deadly disease. Checkpoint kinase 1 (CHK1) is pivotal in regulating cell survival during oncogene-induced replication stress (RS). While CHK1 inhibitors (CHK1i's) show promise as monotherapy for ovarian cancer, a crucial biomarker for effective stratification in clinical trials is lacking, hindering efficacy improvement and toxicity reduction. PP2A B55α, encoded by , is a regulatory subunit of the serine/threonine protein phosphatase 2 (PP2A) that influences CHK1 sensitivity in non-small cell lung cancer (NSCLC). Given the complexity of PP2A B55α function in different types of cancer, here we sought to identify whether deficiency enhances the sensitivity of HGSOC to CHK1 inhibition. To determine whether PPP2R2A deficiency affects the sensitivity of HGSOC to CHK1 inhibition, we treated PPP2R2A knockdown (KD) HGSOC cells or HGSOC cells with naturally low PPP2R2A expression with a CHK1 inhibitor, then assessed cell growth in and assays. Additionally, we investigated the mechanisms contributing to the increased RS and the enhanced sensitivity to the CHK1 inhibitor in PPP2R2A-KD or deficient cells using various molecular biology assays, including western blotting, immunofluorescence, and DNA fiber assays. Our study suggests that KD elevates c-Myc-induced RS via upregulation of replication initiation, rendering HGSOC cells reliant on CHK1 for survival, including those resistant to PARP inhibitors. Combined, these results identify /PP2A B55α as a potential predictive biomarker for CHK1i sensitivity in HGSOC, as well as suggesting it as a therapeutic target to overcome PARP resistance.
高级别浆液性卵巢癌（HGSOC）是最致命的上皮性卵巢癌亚型，尽管PARP抑制剂在治疗应用方面取得了进展，但仍面临持续挑战。因此，迫切需要创新策略来提高这种致命疾病的生存率。关卡激酶1（CHK1）在癌基因诱导的复制应激（RS）期间调节细胞存活中起关键作用。虽然CHK1抑制剂（CHK1i）作为卵巢癌单一疗法显示出前景，但缺乏用于临床试验中有效分层的关键生物标志物，这阻碍了疗效的提高和毒性的降低。由PPP2R2A编码的PP2A B55α是丝氨酸/苏氨酸蛋白磷酸酶2（PP2A）的调节亚基，其影响非小细胞肺癌（NSCLC）中CHK1的敏感性。鉴于PP2A B55α在不同类型癌症中的功能复杂性，我们在此试图确定PPP2R2A缺陷是否会增强HGSOC对CHK1抑制的敏感性。为了确定PPP2R2A缺陷是否影响HGSOC对CHK1抑制的敏感性，我们用CHK1抑制剂处理PPP2R2A敲低（KD）的HGSOC细胞或PPP2R2A天然低表达的HGSOC细胞，然后在细胞活力和克隆形成试验中评估细胞生长。此外，我们使用各种分子生物学试验，包括蛋白质印迹、免疫荧光和DNA纤维试验，研究了PPP2R2A-KD或缺陷细胞中导致RS增加和对CHK1抑制剂敏感性增强的机制。我们的研究表明，KD通过上调复制起始来提高c-Myc诱导的RS，使HGSOC细胞依赖CHK1来存活，包括那些对PARP抑制剂耐药的细胞。综合这些结果，确定PPP2R2A/PP2A B55α为HGSOC中CHK1i敏感性的潜在预测生物标志物，并表明其作为克服PARP耐药性的治疗靶点。
