SIK2 inhibition enhances PARP inhibitor activity synergistically in ovarian and triple-negative breast cancers
Zhen Lu, Weiqun Mao, Hailing Yang, Janice M. Santiago-O’Farrill, Philip J. Rask, Jayanta Mondal, Hu Chen, Cristina Ivan, Xiuping Liu, Chang-Gong Liu, Yuanxin Xi, Kenta Masuda, Eli M. Carrami, Meng Chen, Yitao Tang, Lan Pang, David S. Lakomy, George A. Calin, Han Liang, Ahmed A. Ahmed, Hariprasad Vankayalapati, Robert C. Bast Jr.
Zhen Lu, Weiqun Mao, Hailing Yang, Janice M. Santiago-O’Farrill, Philip J. Rask, Jayanta Mondal, Hu Chen, Cristina Ivan, Xiuping Liu, Chang-Gong Liu, Yuanxin Xi, Kenta Masuda, Eli M. Carrami, Meng Chen, Yitao Tang, Lan Pang, David S. Lakomy, George A. Calin, Han Liang, Ahmed A. Ahmed, Hariprasad Vankayalapati, Robert C. Bast Jr.
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Research Article Cell biology

SIK2 inhibition enhances PARP inhibitor activity synergistically in ovarian and triple-negative breast cancers

Abstract

Poly(ADP-ribose) polymerase inhibitors (PARP inhibitors) have had an increasing role in the treatment of ovarian and breast cancers. PARP inhibitors are selectively active in cells with homologous recombination DNA repair deficiency caused by mutations in BRCA1/2 and other DNA repair pathway genes. Cancers with homologous recombination DNA repair proficiency respond poorly to PARP inhibitors. Cancers that initially respond to PARP inhibitors eventually develop drug resistance. We have identified salt-inducible kinase 2 (SIK2) inhibitors, ARN3236 and ARN3261, which decreased DNA double-strand break (DSB) repair functions and produced synthetic lethality with multiple PARP inhibitors in both homologous recombination DNA repair deficiency and proficiency cancer cells. SIK2 is required for centrosome splitting and PI3K activation and regulates cancer cell proliferation, metastasis, and sensitivity to chemotherapy. Here, we showed that SIK2 inhibitors sensitized ovarian and triple-negative breast cancer (TNBC) cells and xenografts to PARP inhibitors. SIK2 inhibitors decreased PARP enzyme activity and phosphorylation of class-IIa histone deacetylases (HDAC4/5/7). Furthermore, SIK2 inhibitors abolished class-IIa HDAC4/5/7–associated transcriptional activity of myocyte enhancer factor-2D (MEF2D), decreasing MEF2D binding to regulatory regions with high chromatin accessibility in FANCD2, EXO1, and XRCC4 genes, resulting in repression of their functions in the DNA DSB repair pathway. The combination of PARP inhibitors and SIK2 inhibitors provides a therapeutic strategy to enhance PARP inhibitor sensitivity for ovarian cancer and TNBC.

Authors

Zhen Lu, Weiqun Mao, Hailing Yang, Janice M. Santiago-O’Farrill, Philip J. Rask, Jayanta Mondal, Hu Chen, Cristina Ivan, Xiuping Liu, Chang-Gong Liu, Yuanxin Xi, Kenta Masuda, Eli M. Carrami, Meng Chen, Yitao Tang, Lan Pang, David S. Lakomy, George A. Calin, Han Liang, Ahmed A. Ahmed, Hariprasad Vankayalapati, Robert C. Bast Jr.

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Figure 7

ARN3236 and ARN3261 decrease promoter activity of MEF2 transcription factors.

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ARN3236 and ARN3261 decrease promoter activity of MEF2 transcription fac...
(A) Detection of HDAC5 localization with or without SIK2 inhibitors. After overnight incubation, cells were treated with ARN3236 (3 μM) or ARN3261 (5 μM) for 24 hours. Cells were stained with anti-HDAC5 and imaged with fluorescence microscopy for HDAC5 (green) and DAPI (blue). The fluorescence intensity was quantified using ImageJ (Supplemental Figure 4). Scale bar: 20 μm. (B) Quantification of MEF2 promoter activity. Cells were transfected with a mixture of a MEF2-responsive luciferase construct and Renilla luciferase construct for 24 hours and then treated with ARN3236 (4 μM) and ARN3261 (4 μM) for different intervals or with different doses of inhibitor for 24 hours as indicated. The columns indicate the mean of MEF2 luciferase activity, and the bars indicate the SD. One-way ANOVA and Tukey’s multiple-comparison test were performed (NS, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001). Representative data were from 1 independent experiment with 3 technical repeats. Experiments were repeated 2 times. (C and D) Quantification of MEF2 promoter activity with and without knockdown of HDAC4 and HDAC5 (C). Cells were transfected with targeting or control siRNA for 24 hours prior to transfection of a mixture of a MEF2-responsive luciferase construct and Renilla luciferase construct. Cells were then treated with ARN3236 (4 μM) or ARN3261 (4 μM) for 24 hours. HDAC4 and HDAC5 siRNA knockdown efficiency was measured by Western blot analysis (D). Representative data are from 1 independent experiment with 3 replicates. Experiments were repeated twice with similar results. Two-way ANOVA and Dunnett’s multiple-comparison test were performed (NS, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001).