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 3

Combined effect of SIK2 inhibitor and olaparib on PARP-1 enzyme activity and DNA DSB repair pathways.

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Combined effect of SIK2 inhibitor and olaparib on PARP-1 enzyme activity...
(A) Dose-response curves for olaparib and combined effect of SIK2 inhibitors with olaparib on PARP-1 enzyme activity. OVCAR8 and MDA-MB-231 cells were treated with SIK2 inhibitors, olaparib alone, or the combination for 26 hours. The concentrations of ARN3236, ARN3261, and olaparib were 6 μM, 4 μM, and 0.05 μM, respectively (also see Supplemental Figure 2C). The columns indicate the mean activity and the bars indicate the SD. The statistical significance was calculated with 1-way ANOVA and Tukey’s multiple-comparison test (*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001). (B) Dose-response curves of ARN3236, ARN3261, and olaparib in DT40 PARP-1–/– cells with and without knockin of human PARP-1 (hPARP). The IC50 indicated on the curves was calculated using GraphPad Prism 8. The expression of exogenous hPARP in DT40 PARP-1–/– was measured by Western blotting. For both A and B, the representative data were from 1 experiment with 3 replicates. Experiments were repeated 3 times with similar results. (C) The heatmap presentation of unsupervised hierarchical clustering of gene expression. The heatmap includes 3587 transcripts (upregulated or downregulated by ≥2-fold) treated with ARN3236, ARN3261, olaparib, ARN3236 plus olaparib, and ARN3261 plus olaparib. The heatmap illustrates changes that are color coded with red corresponding to upregulation and green to downregulation. (D) The Venn representation. Venn diagram analysis represented the number of genes (upregulated or downregulated by ≥2-fold) that were overlapped by the treatment of ARN3236 plus olaparib (yellow) or ARN3261 plus olaparib (green). (E) GO analysis of 1380 differentially expressed genes shared by ARN3236 plus olaparib or ARN3261 plus olaparib treatments. The bar plot shows the log10 P value of the biological process GO terms obtained with differentially expressed genes at P < 0.01.