The mechanisms of paraneoplastic thrombocytosis in ovarian cancer and the role that platelets play in abetting cancer growth are unclear. We analyzed clinical data on 619 patients with epithelial ovarian cancer to test associations between platelet counts and disease outcome. Human samples and mouse models of epithelial ovarian cancer were used to explore the underlying mechanisms of paraneoplastic thrombocytosis. The effects of platelets on tumor growth and angiogenesis were ascertained. Thrombocytosis was significantly associated with advanced disease and shortened survival. Plasma levels of thrombopoietin and interleukin-6 were significantly elevated in patients who had thrombocytosis as compared with those who did not. In mouse models, increased hepatic thrombopoietin synthesis in response to tumor-derived interleukin-6 was an underlying mechanism of paraneoplastic thrombocytosis. Tumor-derived interleukin-6 and hepatic thrombopoietin were also linked to thrombocytosis in patients. Silencing thrombopoietin and interleukin-6 abrogated thrombocytosis in tumor-bearing mice. Anti–interleukin-6 antibody treatment significantly reduced platelet counts in tumor-bearing mice and in patients with epithelial ovarian cancer. In addition, neutralizing interleukin-6 significantly enhanced the therapeutic efficacy of paclitaxel in mouse models of epithelial ovarian cancer. The use of an antiplatelet antibody to halve platelet counts in tumor-bearing mice significantly reduced tumor growth and angiogenesis. These findings support the existence of a paracrine circuit wherein increased production of thrombopoietic cytokines in tumor and host tissue leads to paraneoplastic thrombocytosis, which fuels tumor growth. We speculate that countering paraneoplastic thrombocytosis either directly or indirectly by targeting these cytokines may have therapeutic potential. (Funded by the National Cancer Institute and others.)

We studied Dicer and Drosha, components of the RNA-interference machinery, in ovarian cancer. We measured messenger RNA (mRNA) levels of Dicer and Drosha in specimens of invasive epithelial ovarian cancer from 111 patients, using a quantitative reverse-transcriptase–polymerase-chain-reaction assay, and compared the results with clinical outcomes. Validation was performed with the use of published microarray data from cohorts of patients with ovarian, breast, and lung cancer. Mutational analyses of genomic DNA from the Dicer and Drosha genes were performed in a subgroup of ovarian-cancer specimens. Dicer-dependent functional assays were performed by means of in vitro transfection with small interfering RNA (siRNA) and short hairpin RNA (shRNA). Levels of Dicer and Drosha mRNA correlated with the levels of expression of the corresponding protein and were decreased in 60% and 51% of ovarian-cancer specimens, respectively. Low Dicer expression was significantly associated with advanced tumor stage (P=0.007), and low Drosha expression with suboptimal surgical cytoreduction (P=0.02). Cancer specimens with both high Dicer expression and high Drosha expression were associated with increased median survival (>11 years, vs. 2.66 years for other subgroups; P<0.001). We found three independent predictors of reduced disease-specific survival in multivariate analyses: low Dicer expression (hazard ratio, 2.10; P=0.02), high-grade histologic features (hazard ratio, 2.46; P=0.03), and poor response to chemotherapy (hazard ratio, 3.95; P<0.001). Poor clinical outcomes among patients with low Dicer expression were validated in additional cohorts of patients. Rare missense mutations were found in the Dicer and Drosha genes, but their presence or absence did not correlate with the level of expression. Functional assays indicated that gene silencing with shRNA, but not siRNA, may be impaired in cells with low Dicer expression. Our findings indicate that levels of Dicer and Drosha mRNA in ovarian-cancer cells have associations with outcomes in patients with ovarian cancer.

MiRNAs are a key component of the noncoding RNA family. The underlying mechanisms involved in the interplay between the tumor microenvironment and cancer cells involve highly dynamic factors such as hypoxia and cell types such as cancer-associated fibroblasts and macrophages. Although miRNA levels are known to be altered in cancer cells, recent evidence suggests a critical role for the tumor microenvironment in regulating miRNA biogenesis, methylation, and transcriptional changes. Here, we discuss the complex protumorigenic symbiotic role between tumor cells, the tumor microenvironment, and miRNA deregulation. Significance: miRNAs play a central role in cell signaling and homeostasis. In this article, we provide insights into the regulatory mechanisms involved in the deregulation of miRNAs in cancer cells and the tumor microenvironment and discuss therapeutic intervention strategies to overcome this deregulation. Cancer Discov; 6(3); 235–46. ©2016 AACR.

Purpose: There is growing evidence that stress and other behavioral factors may affect cancer progression and patient survival. The underlying mechanisms for this association are poorly understood. The purpose of this study is to determine the effects of stress-associated hormones norepinephrine, epinephrine, and cortisol on the invasive potential of ovarian cancer cells. Experimental Design: The ovarian cancer cells EG, SKOV3, and 222 were exposed to increasing levels of either norepinephrine, epinephrine, or cortisol, and the in vitro invasive potential was determined using the membrane invasion culture system. Additionally, the effects of these stress hormones on matrix metalloproteinase-2 (MMP-2) and MMP-9 were determined by ELISA. The effects of the β-adrenergic agonist isoproterenol on in vivo tumor growth were determined using nude mice. Results: Stress levels of norepinephrine increased the in vitro invasiveness of ovarian cancer cells by 89% to 198%. Epinephrine also induced significant increases in invasion in all three cell lines ranging from 64% to 76%. Cortisol did not significantly affect invasiveness of the EG and 222 cell lines but increased invasion in the SKOV3 cell line (P = 0.01). We have previously shown that ovarian cancer cells express β-adrenergic receptors. The β-adrenergic antagonist propanolol (1 μmol/L) completely blocked the norepinephrine-induced increase in invasiveness. Norepinephrine also increased tumor cell expression of MMP-2 (P = 0.02 for both SKOV3 and EG cells) and MMP-9 (P = 0.01 and 0.04, respectively), and pharmacologic blockade of MMPs abrogated the effects of norepinephrine on tumor cell invasive potential. Isoproterenol treatment resulted in a significant increase in tumor volume and infiltration in the SKOV3ip1 in vivo model, which was blocked by propranolol. Conclusions: These findings provide direct experimental evidence that stress hormones can enhance the invasive potential of ovarian cancer cells. These effects are most likely mediated by stimulation of MMPs.