Chronic Neurobehavioral Stress Promotes Resistance to Chemotherapy in Epithelial Ovarian Carcinoma

While there is growing evidence that chronic stress can promote tumor growth, much less is known about potential effects on response to chemotherapy. Here, we first examined the effects of stress hormones (Glucocorticoids and catecholamine) in vitro on efficacy of various cytotoxic agents in ovarian cancer cells and in vivo using orthotopic mouse models of ovarian carcinoma (HeyA8 and SKOV3ip1). To address possible contributions of the hypothalamic pituitary adrenal (HPA)-axis versus sympathetic nervous system (SNS) to the compromised efficacy of chemotherapy, we examined the in vitro effects of either dexamethasone (DXM) or isoproterenol on tumor apoptosis. DXM substantially reduced chemotherapy induced apoptosis while isoproterenol had no significant effect. While in vivo treatment with either docetaxel or cisplatin was effective in reducing tumor growth, exposure to daily restraint stress reduced the efficacy of cisplatin and docetaxel by > 2-fold without any effect on tumor growth. Treatment with RU-486 or glucocorticoid receptor (GR) specific siRNA completely abrogated the stress induced chemoresistance. Additionally, DXM-induced reduction of apoptosis was readily reversed with either RU-486 or GR siRNA. DXM treatment in vitro also increased Bcl-XL expression and reduced caspase-9 cleavage. Further studies demonstrated DXM-associated upregulation of autophagy related genes (Beclin1, LC3-II, and Atg-5), resulting in decreased efficacy of docetaxel. Taken together, these data indicate that chronic stress may compromise the efficacy of conventional chemotherapy through reduction in apoptosis and modulation of autophagy. These findings may have implications for clinical management of ovarian cancer patients. Additionally, our recent findings suggest that chronic stress is associated with increased IL8 levels. We next examined the molecular and biological significance of IL8 in stress-induced tumor growth. Norepinephrine (NE) treatment of ovarian cancer cells resulted in a 250-300% increase in IL8 protein and 240-320% increase in its mRNA levels. Moreover, NE treatment resulted in a 3.5-4 fold increase in IL8 promoter activity. Promoter deletion analyses suggested that AP1 transcription factors might mediate catecholamine stimulated upregulation of IL8. SiRNA inhibition studies identified FosB as the pivotal component responsible for IL8 regulation by NE. In vivo chronic stress resulted in increased tumor growth (by 221% and 235%; p<0.01) in orthotopic xenograft models involving SKOV3ip1 and HeyA8 ovarian carcinoma cells. This was completely blocked by IL8 or FosB gene silencing using DOPC nanoliposomes. IL8 and FosB silencing reduced microvessel density (based on CD31 staining) by 2.5 and 3.5 fold, respectively (p<0.001). Our findings indicate that neurobehavioral stress leads to FosB driven increases in IL8, which is associated with increased tumor growth and metastases. Lastly, we demonstrate that t10:c12 CLA results in substantial inhibition of ovarian cancer cell proliferation and migration as well as induction of autophagy. These findings also correlate with significant modulation in microRNA profile in ovarian cancer cells.