A Novel Salt Inducible Kinase 2 Inhibitor, ARN-3261, Sensitizes Ovarian Cancer Cell Lines and Xenografts to Carboplatin

A novel SIK2 inhibitor SIC-19 exhibits synthetic lethality with PARP inhibitors in ovarian cancer

PURPOSE

Ovarian cancer patients with HR proficiency (HRP) have had limited benefits from PARP inhibitor treatment, highlighting the need for improved therapeutic strategies. In this study, we developed a novel SIK2 inhibitor, SIC-19, and investigated its potential to enhance the sensitivity and expand the clinical utility of PARP inhibitors in ovarian cancer.

METHODS

The SIK2 protein was modeled using a Molecular Operating Environment (MOE), and the most favorable model was selected based on a GBVI/WSA dG scoring function. The Chembridge Compound Library was screened, and the top 20 candidate compounds were tested for their interaction with SIK2 and downstream substrates, AKT-pS473 and MYLK-pS343. SIC-19 emerged as the most promising drug candidate and was further evaluated using multiple assays.

RESULTS

SIC-19 exhibited selective and potent inhibition of SIK2, leading to its degradation through the ubiquitination pathway. The IC50 of SIC-19 correlated inversely with endogenous SIK2 expression in ovarian cancer cell lines. Treatment with SIC-19 significantly inhibited cancer cell growth and sensitized cells to PARP inhibitors in vitro, as well as in ovarian cancer organoids and xenograft models. Mechanistically, SIK2 knockdown and SIC-19 treatment reduced RAD50 phosphorylation at Ser635, prevented nuclear translocation of RAD50, disrupted nuclear filament assembly, and impaired DNA homologous recombination repair, ultimately inducing apoptosis. These findings highlight the crucial role of SIK2 in the DNA HR repair pathway and demonstrate the significant PARP inhibitor sensitization achieved by SIC-19 in ovarian cancer.

CONCLUSIONS

SIC-19, a novel SIK2 inhibitor, effectively inhibits tumor cell growth in ovarian cancer by interfering with RAD50-mediated DNA HR repair. Furthermore, SIC-19 enhances the efficacy of PARP inhibitors, providing a promising therapeutic strategy to improve outcomes for ovarian cancer patients.

Roles of salt‑inducible kinases in cancer (Review)

Salt inducible kinases (SIKs) with three subtypes SIK1, SIK2 and SIK3, belong to the AMP‑activated protein kinase family. They are expressed ubiquitously in humans. Under normal circumstances, SIK1 regulates adrenocortical function in response to high salt or adrenocorticotropic hormone stimulation, SIK2 is involved in cell metabolism, controlling insulin signaling and gluconeogenesis and SIK3 coordinates with the mTOR complex, promoting cancer. The dysregulation of SIKs has been widely detected in various types of cancers. Based on most of the existing studies, SIK1 is mostly considered a tumor inhibitor, SIK2 and SIK3 are usually associated with tumor promotion. However, the functions of SIKs have shown contradictory in certain tumors, suggesting that SIKs cannot be simply classified as oncogenes or tumor suppressor genes. The present review provided a comprehensive summary of the roles of SIKs in the initiation and progression of different cancers, aiming to elucidate their clinical value and discuss potential strategies for targeting SIKs in cancer therapy.

European trends in ovarian cancer mortality, 1990-2020 and predictions to 2025

INTRODUCTION

Over the last decades, ovarian cancer mortality in Europe has been decreasing, but disparities in trends were observed. In this paper, we analysed ovarian cancer mortality trends in Europe over the period 1990-2020 and predicted the number of deaths and rates by 2025.

METHODS

We extracted population and death certification data from ovarian cancer in women for 31 European countries, between 1990 and 2020 from the World Health Organization database. We computed age-standardised mortality rates (ASMR) per 100,000 women-years, based on the world standard population. We also obtained predictions for 2025 using a joinpoint regression model and calculated the number of avoided deaths over the period 1994-2025.

RESULTS

Over the observed period, mortality from ovarian cancer showed a favourable pattern in most countries. In the EU-27, rates declined by 5.9% from 2010-2014 to 2015-2019, reaching an ASMR of 4.66/100,000. During the same period, the decline in ovarian cancer mortality was more pronounced in the EU-14 countries (-7.0%) compared to Transitional countries (-2.1%). Declines were also observed in the United Kingdom, to reach an ASMR of 5.29. Decreases in mortality from ovarian cancer are predicted until 2025, to 4.17/100,000 for the EU-27.

CONCLUSIONS

Favourable trends in ovarian cancer mortality are expected to persist in Europe and can be mainly attributed to the increased use of oral contraceptives in subsequent generations of European women. Decreased use of menopausal Hormone Replacement Therapy and improved diagnosis and management may also have played a role.

Salt-inducible kinases: new players in pulmonary arterial hypertension?

Salt-inducible kinases (SIKs) are serine/threonine kinases belonging to the AMP-activated protein kinase (AMPK) family. Accumulating evidence indicates that SIKs phosphorylate multiple targets, including histone deacetylases (HDACs) and cAMP response element-binding protein (CREB)-regulated transcriptional coactivators (CRTCs), to coordinate signaling pathways implicated in metabolism, cell growth, proliferation, apoptosis, and inflammation. These pathways downstream of SIKs are altered not only in pathologies like cancer, systemic hypertension, and inflammatory diseases, but also in pulmonary arterial hypertension (PAH), a multifactorial disease characterized by pulmonary vasoconstriction, inflammation and remodeling of pulmonary arteries owing to endothelial dysfunction and aberrant proliferation of smooth muscle cells (SMCs). In this opinion article, we present evidence of SIKs as modulators of key signaling pathways involved in PAH pathophysiology and discuss the potential of SIKs as therapeutic targets for PAH, emphasizing the need for deeper molecular insights on PAH.

Salt inducible kinases and PTH1R action

Parathyroid hormone is a central regulator of calcium homeostasis. PTH protects the organism from hypocalcemia through its actions in bone and kidney. Recent physiologic studies have revealed key target genes for PTH receptor (PTH1R) signaling in these target organs. However, the complete signal transduction cascade used by PTH1R to accomplish these physiologic actions has remained poorly defined. Here we will review recent studies that have defined an important role for salt inducible kinases downstream of PTH1R in bone, cartilage, and kidney. PTH1R signaling inhibits the activity of salt inducible kinases. Therefore, direct SIK inhibitors represent a promising novel strategy to mimic PTH actions using small molecules. Moreover, a detailed understanding of the molecular circuitry used by PTH1R to exert its biologic effects will afford powerful new models to better understand the diverse actions of this important G protein coupled receptor in health and disease.

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

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.

Next steps in the early detection of ovarian cancer

Bast et al. discuss the early detection of ovarian cancer in the context of the recent UKCTOCS screening trial. The authors suggest potential reasons why the trial failed to achieve a reduction in mortality and outline next steps in the development of biomarkers and imaging modalities to detect ovarian cancer.