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 3

Loss of NSFL1C restabilizes kinetochore-microtubule attachments in BRCA2-deficient cells.

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Loss of NSFL1C restabilizes kinetochore-microtubule attachments in BRCA2...
(A) Loss of NSFL1C reduced aberrant chromosome segregation of BRCA2-deficient HeLa cells (n = 3). The white arrow points to the chromosome bridges, and the orange arrow points to the lagging chromosomes. Scale bar: 10 μm. (B) Violin chart of γH2AX foci in metaphase and anaphase plus telophase HeLa cells. See Supplemental Figure 3B for representative images. (C and D) Loss of NSFL1C restabilized cold-stable microtubules in BRCA2-deficient HeLa cells. (C) Representative images of cold-stable microtubules in cells transfected with the indicated siRNA. Cells were costained with α-tubulin and CENPB as markers for centromeres. Insets show one enlargement of the outlined regions. Scale bar: 10 μm. (D) Frequency of K-fiber defects (n = 3). (E–G) Loss of NSFL1C restored the kinetochore-microtubule attachments in BRCA2-deficient cells. HEC1, an inner kinetochore protein, are used as markers for locating centromeres, while CENPB serves as marker for centromeres. Representative images for E can be seen in Supplemental Figure 3E. Representative images for F can be seen in G. Insets show one enlargement of the outlined regions, and “d” represents the distance between centromeres. Scale bar: 10 μm. (H) Measurement of kinetochore-microtubule attachments in BRCA2/NSFL1C DKO HeLa cells expressing the sgRNA-resistant NSFL1C or transfected with control vector or NSFL1C-G97R mutant (95C19 C. elegans homologous mutation). Scale bar: 10 μm. (I) Schematic representation of kinetochore-microtubule attachments. Data indicate the mean ± SEM. *P < 0.05, **P < 0.01, and ****P < 0.0001. Unpaired, 2-tailed Student’s t test was used in B. One-way ANOVA was used in A, D, E, F, and H.