A Novel Compound ARN-3236 Inhibits Salt-Inducible Kinase 2 and Sensitizes Ovarian Cancer Cell Lines and Xenografts to Paclitaxel.

Purpose: Salt-inducible kinase 2 (SIK2) is a centrosome kinase required for mitotic spindle formation and a potential target for ovarian cancer therapy. Here, we examine the effects of a novel small-molecule SIK2 inhibitor, ARN-3236, on sensitivity to paclitaxel in ovarian cancer.Experimental Design: SIK2 expression was determined in ovarian cancer tissue samples and cell lines. ARN-3236 was tested for its efficiency to inhibit growth and enhance paclitaxel sensitivity in cultures and xenografts of ovarian cancer cell lines. SIK2 siRNA and ARN-3236 were compared for their ability to produce nuclear-centrosome dissociation, inhibit centrosome splitting, block mitotic progression, induce tetraploidy, trigger apoptotic cell death, and reduce AKT/survivin signaling.Results: SIK2 is overexpressed in approximately 30% of high-grade serous ovarian cancers. ARN-3236 inhibited the growth of 10 ovarian cancer cell lines at an IC50 of 0.8 to 2.6 µmol/L, where the IC50 of ARN-3236 was inversely correlated with endogenous SIK2 expression (Pearson r = -0.642, P = 0.03). ARN-3236 enhanced sensitivity to paclitaxel in 8 of 10 cell lines, as well as in SKOv3ip (P = 0.028) and OVCAR8 xenografts. In at least three cell lines, a synergistic interaction was observed. ARN-3236 uncoupled the centrosome from the nucleus in interphase, blocked centrosome separation in mitosis, caused prometaphase arrest, and induced apoptotic cell death and tetraploidy. ARN-3236 also inhibited AKT phosphorylation and attenuated survivin expression.Conclusions: ARN-3236 is the first orally available inhibitor of SIK2 to be evaluated against ovarian cancer in preclinical models and shows promise in inhibiting ovarian cancer growth and enhancing paclitaxel chemosensitivity. Clin Cancer Res; 23(8); 1945-54. ©2016 AACR.

Histone deacetylases as new therapy targets for platinum-resistant epithelial ovarian cancer.

INTRODUCTION: In developed countries, ovarian cancer is the fourth most common cancer in women. Due to the non-specific symptomatology associated with the disease many patients with ovarian cancer are diagnosed late, which leads to significantly poorer prognosis. Apart from surgery and radiotherapy, a substantial number of ovarian cancer patients will undergo chemotherapy and platinum based agents are the mainstream first-line therapy for this disease. Despite the initial efficacy of these therapies, many women relapse; therefore, strategies for second-line therapies are required. Regulation of DNA transcription is crucial for tumour progression, metastasis and chemoresistance which offers potential for novel drug targets. METHODS: We have reviewed the existing literature on the role of histone deacetylases, nuclear enzymes regulating gene transcription. RESULTS AND CONCLUSION: Analysis of available data suggests that a signifant proportion of drug resistance stems from abberant gene expression, therefore HDAC inhibitors are amongst the most promising therapeutic targets for cancer treatment. Together with genetic testing, they may have a potential to serve as base for patient-adapted therapies.

Leptin signalling, obesity and prostate cancer: molecular and clinical perspective on the old dilemma.

The prevalence of global obesity is increasing. Obesity is associated with general cancer-related morbidity and mortality and is a known risk factor for development of specific cancers. A recent large systematic review of 24 studies based on meta-analysis of 11,149 patients with prostate cancer showed a significant correlation between obesity and the risk of advanced prostate cancer. Further, a sustained reduction in BMI correlates with a decreased risk of developing aggressive disease. On the other hand, the correlation between consuming different products and prostate cancer occurrence/risk is limited.Here, we review the role of adipose tissue from an endocrine perspective and outline the effect of adipokines on cancer metabolism, with particular focus on leptin. Leptin exerts its physiological and pathological effects through modification of intracellular signalling, most notably activating the Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 3 pathway and recently shown sphingolipid pathway. Both high levels of leptin in circulation and leptin receptor mutation are associated with prostate cancer risk in human patients; however, the in vivo mechanistic evidence is less conclusive.Given the complexity of metabolic cancer pathways, it is possible that leptin may have varying effects on prostate cancer at different stages of its development, a point that may be addressed by further epidemiological studies.

HDAC4-regulated STAT1 activation mediates platinum resistance in ovarian cancer.

Ovarian cancer frequently acquires resistance to platinum chemotherapy, representing a major challenge for improving patient survival. Recent work suggests that resistant clones exist within a larger drug-sensitive cell population prior to chemotherapy, implying that resistance is selected for rather than generated by treatment. We sought to compare clinically derived, intrapatient paired models of initial platinum response and subsequent resistant relapse to define molecular determinants of evolved resistance. Transcriptional analysis of a matched cell line series from three patients with high-grade serous ovarian cancer before and after development of clinical platinum resistance (PEO1/PEO4/PEO6, PEA1/PEA2, PEO14/PEO23) identified 91 up- and 126 downregulated genes common to acquired resistance. Significantly enhanced apoptotic response to platinum treatment in resistant cells was observed following knockdown of histone deacetylase (HDAC) 4, FOLR2, PIK3R1, or STAT1 (P < 0.05). Interestingly, HDAC4 and STAT1 were found to physically interact. Acetyl-STAT1 was detected in platinum-sensitive cells but not in HDAC4 overexpressing platinum-resistant cells from the same patient. In resistant cells, STAT1 phosphorylation/nuclear translocation was seen following platinum exposure, whereas silencing of HDAC4 increased acetyl-STAT1 levels, prevented platinum-induced STAT1 activation, and restored cisplatin sensitivity. Conversely, matched sensitive cells were refractory to STAT1 phosphorylation on platinum treatment. Analysis of 16 paired tumor biopsies taken before and after development of clinical platinum resistance showed significantly increased HDAC4 expression in resistant tumors [n = 7 of 16 (44%); P = 0.04]. Therefore, clinical selection of HDAC4-overexpressing tumor cells upon exposure to chemotherapy promotes STAT1 deacetylation and cancer cell survival. Together, our findings identify HDAC4 as a novel, therapeutically tractable target to counter platinum resistance in ovarian cancer.