Combinatorial targeting of Hippo-STRIPAK and PARP elicits synthetic lethality in gastrointestinal cancers
Liwei An, … , Shi Jiao, Zhaocai Zhou
Liwei An, … , Shi Jiao, Zhaocai Zhou
Published March 15, 2022
Citation Information: J Clin Invest. 2022;132(9):e155468. https://doi.org/10.1172/JCI155468.
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Research Article Cell biology Gastroenterology

Combinatorial targeting of Hippo-STRIPAK and PARP elicits synthetic lethality in gastrointestinal cancers

Abstract

The striatin-interacting phosphatase and kinase (STRIPAK) complexes integrate extracellular stimuli that result in intracellular activities. Previously, we discovered that STRIPAK is a key machinery responsible for loss of the Hippo tumor suppressor signal in cancer. Here, we identified the Hippo-STRIPAK complex as an essential player in the control of DNA double-stranded break (DSB) repair and genomic stability. Specifically, we found that the mammalian STE20-like protein kinases 1 and 2 (MST1/2), independent of classical Hippo signaling, directly phosphorylated zinc finger MYND type–containing 8 (ZMYND8) and hence resulted in the suppression of DNA repair in the nucleus. In response to genotoxic stress, the cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) pathway was determined to relay nuclear DNA damage signals to the dynamic assembly of Hippo-STRIPAK via TANK-binding kinase 1–induced (TBK1-induced) structural stabilization of the suppressor of IKBKE 1– sarcolemma membrane–associated protein (SIKE1-SLMAP) arm. As such, we found that STRIPAK-mediated MST1/2 inactivation increased the DSB repair capacity of cancer cells and endowed these cells with resistance to radio- and chemotherapy and poly(ADP-ribose)polymerase (PARP) inhibition. Importantly, targeting the STRIPAK assembly with each of 3 distinct peptide inhibitors efficiently recovered the kinase activity of MST1/2 to suppress DNA repair and resensitize cancer cells to PARP inhibitors in both animal- and patient-derived tumor models. Overall, our findings not only uncover what we believe to be a previously unrecognized role for STRIPAK in modulating DSB repair but also provide translational implications of cotargeting STRIPAK and PARP for a new type of synthetic lethality anticancer therapy.

Authors

Liwei An, Zhifa Cao, Pingping Nie, Hui Zhang, Zhenzhu Tong, Fan Chen, Yang Tang, Yi Han, Wenjia Wang, Zhangting Zhao, Qingya Zhao, Yuqin Yang, Yuanzhi Xu, Gemin Fang, Lei Shi, Huixiong Xu, Haiqing Ma, Shi Jiao, Zhaocai Zhou

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Figure 6

MST1/2 kinases phosphorylate ZMYND8 and limit ZMYND8-dependent DSB repair.

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MST1/2 kinases phosphorylate ZMYND8 and limit ZMYND8-dependent DSB repai...
(A) Heatmap demonstration of the relative abundances of phosphopeptides identified using MS analysis. (B) Gels showing attenuation of ZMYND8 phosphorylation in MST1/2-DKO cells. HGC-27 cells (WT and MST1/2-DKO) were treated with etoposide and then harvested 8 hours after treatment. (C) Time-resolved analysis of ZMYND8 phosphorylation upon DNA damage in HGC-27 cells. (D) Gels showing ZMYND8 phosphorylated at Ser486/Ser490. 293FT cells transfected with the indicated constructs were exposed to etoposide and harvested 8 hours later. (E) Gels showing that MST2 phosphorylated ZMYND8 in vitro. Purified Flag-ZMYND8 proteins (WT and 2SA) were incubated with MST2 recombinant protein at 30°C for 15 minutes. (F and G) Images showing that phosphorylation of ZMYND8 by MST1/2 suppressed its recruitment to DSBs. (F) HGC-27 cells (WT and MST1/2-DKO) were transfected with GFP-ZMYND8, or (G) HGC-27 cells were transfected with GFP-tagged ZMYND8 or its 2SA mutant before being subjected to laser-induced live cell imaging (n = 5). Scale bars: 1 μm. (H) Plot showing that depletion of ZMYND8 rescued hyperactive HR repair in MST1/2-deficient cells (n = 3). (I) Results of the HR reporter assay of 293A cells transfected with WT ZMYND8 or its 2SA mutant (n = 3). (J) Gels showing that phosphorylation of ZMYND8 by MST1/2 impaired its recognition of H4K16Ac. ***P < 0.001, by 1-way ANOVA with Dunnett’s post hoc test (H and I). See also Supplemental Figure 7. exp, exposure.