PP2A inhibition causes synthetic lethality in BRCA2-mutated prostate cancer models via spindle assembly checkpoint reactivation
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
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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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 5

NSFL1C promotes USP9X-mediated deubiquitination of AURKB to stabilize centromeric AURKB.

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NSFL1C promotes USP9X-mediated deubiquitination of AURKB to stabilize ce...
(A) Volcano plot illustrating the differentially expressed proteins (DEPs) in SFB-AURKB stable HEK293T cells transfected with Myc-NSFL1C (G97R) or empty vector. DEP analysis in the non-repetitive group used the edgeR package (https://bioconductor.org/packages/edgeR), and the volcano plot was drawn using the ggplot2 package (https://ggplot2.tidyverse.org). See Supplemental Table 3 for details. (B) The NSFL1C protein was required for the USP9X-AURKB interaction. HeLa cells were treated with the indicated siRNA. *Monoubiquitination; **diubiquitination; ***triubiquitination. (C) USP9X regulated ubiquitination of AURKB. HeLa cells were treated with the indicated siRNA. (D) VCPi (NMS-873, 10 μM) rescued the chromatin loading of AURKB in USP9X-knockdown cells. HeLa cells were treated with the indicated siRNA, synchronized by sequential nocodazole-VCPi treatment, and collected for immunoblotting detection. (E) Loss of USP9X restored the kinetochore-microtubule attachments in BRCA2-deficient HeLa cells. (F) Loss of USP9X restabilized cold-stable microtubules in BRCA2-deficient HeLa cells (n = 3). (G) CDK1 regulated ubiquitination of AURKB. HeLa cells were synchronized by CDK1i (RO3306, 9 μM) treatment and collected for immunoblotting detection. (H) Phosphorylation of NSFL1C by CDK1 was necessary for the USP9X-AURKB interaction. *Monoubiquitination; **diubiquitination. (I) Reintroduction of NSFL1C-WT rescued the increase in AURKB polyubiquitination in BRCA2/NSFL1C DKO HeLa cells, but NSFL1C-S140A had no effect. (J) Brood size assay upon treatment with endogenous siRNA directed against the indicated genes in the N2 and C. elegans brc-2 mutants (n = 3). (K) Deletion of air-2 and bub-1 partially restored the viability of C. elegans brc-2 mutants (n = 3). (L) Schematic of the effect of silencing different genes on C. elegans brc-2 mutants. Data indicate the mean ± SEM. **P < 0.01, ***P < 0.001, and ****P < 0.0001. One-way ANOVA was used in E and F.