PP2A inhibition causes synthetic lethality in BRCA2-mutated prostate cancer models via spindle assembly checkpoint reactivation
Jian Wang, … , Weibin Wang, Jiadong Wang
Jian Wang, … , Weibin Wang, Jiadong Wang
Published November 7, 2023
Citation Information: J Clin Invest. 2024;134(1):e172137. https://doi.org/10.1172/JCI172137.
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Research Article Cell biology Oncology

PP2A inhibition causes synthetic lethality in BRCA2-mutated prostate cancer models via spindle assembly checkpoint reactivation

Abstract

Mutations in the BRCA2 tumor suppressor gene have been associated with an increased risk of developing prostate cancer. One of the paradoxes concerning BRCA2 is the fact that its inactivation affects genetic stability and is deleterious for cellular and organismal survival, while BRCA2-mutated cancer cells adapt to this detriment and malignantly proliferate. Therapeutic strategies for tumors arising from BRCA2 mutations may be discovered by understanding these adaptive mechanisms. In this study, we conducted forward genetic synthetic viability screenings in Caenorhabditis elegans brc-2 (Cebrc-2) mutants and found that Ceubxn-2 inactivation rescued the viability of Cebrc-2 mutants. Moreover, loss of NSFL1C, the mammalian ortholog of CeUBXN-2, suppressed the spindle assembly checkpoint (SAC) activation and promoted the survival of BRCA2-deficient cells. Mechanistically, NSFL1C recruited USP9X to inhibit the polyubiquitination of AURKB and reduce the removal of AURKB from the centromeres by VCP, which is essential for SAC activation. SAC inactivation is common in BRCA2-deficient prostate cancer patients, but PP2A inhibitors could reactivate the SAC and achieve BRCA2-deficient prostate tumor synthetic lethality. Our research reveals the survival adaptation mechanism of BRCA2-deficient prostate tumor cells and provides different angles for exploring synthetic lethal inhibitors in addition to targeting DNA damage repair pathways.

Authors

Jian Wang, Yuke Chen, Shiwei Li, Wanchang Liu, Xiao Albert Zhou, Yefei Luo, Zhanzhan Xu, Yundong Xiong, Kaiqi Cheng, Mingjian Ruan, Wei Yu, Xiaoman Li, Weibin Wang, Jiadong Wang

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Figure 2

SAC attenuation by NSFL1C depletion promotes growth of BRCA2-deficient cells.

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SAC attenuation by NSFL1C depletion promotes growth of BRCA2-deficient c...
(A) Left: Ratio of IdU versus CldU upon HU treatment (n = 3). Right: Schematic for labeling HeLa cells with CldU and IdU and representative images. (B) Quantification of IR-induced RAD51 foci in cyclin A–positive HeLa cells (left) and representative images (right) (n = 3). Scale bar: 10 μm. (C and D) HeLa cells expressing mRFP-tubulin and GFP-H2B were transfected with control siRNA (see Supplemental Video 1), BRCA2 siRNA (see Supplemental Video 2), NSFL1C siRNA (see Supplemental Video 3), and BRCA2/NSFL1C siRNA (see Supplemental Video 4), respectively. “NEBD” indicates the first frame after NEBD, based on the chromatin marker GFP-H2B. Times are shown in hours:minutes. Percentage of surviving mitotic cells is quantified in C. Representative frames are shown in D, left, and percentages of different fates of cells are shown in D, right. Scale bars: 10 μm. (E) Top: Schematic for synchronization experiments. Bottom: HeLa cells were treated with the indicated siRNA, synchronized by sequential thymidine-CDK1i (RO3306, 9 μM) treatment, and added to fresh medium before CDC20 immunoprecipitation. Middle: Quantitation of BubR1 relative pull-down was performed using ImageJ software. (F) Top: Schematic for synchronization experiments. Bottom: Flow cytometric analysis. HeLa cells were treated with the indicated siRNA, synchronized by nocodazole (Noco) treatment, and subsequently stained with H3Ser10p antibody, which is used as a marker for mitosis and propidium iodide (PI). (G) Left: Schematic for synchronization experiments. Right: HeLa cells were treated with the indicated siRNA and synchronized by sequential thymidine-nocodazole treatment, and cells were collected for H3Ser10p immunoblotting detection, which is used as a marker for mitosis. Data indicate the mean ± SEM. **P < 0.01, ***P < 0.001, and ****P < 0.0001. One-way ANOVA was used in A and B; χ2 test was used in C.