Abstract 937: Molecular dynamics of SrcS17 activation in chronic stress-induced tumor growth

Abstract

Abstract Clinical studies have demonstrated that chronic stress can influence cancer progression. However, the underlying mechanisms are not fully understood. To determine the molecular drivers of downstream signaling networks activated in response to chronic stress, we performed a phosphoproteomic analysis and determined that the non-receptor tyrosine kinase, Src, was the key regulator of these networks. Since Src plays an important role in cancer biology, we examined the biological and clinical significance of Src in stress-mediated tumor growth. Norepinephrine (NE) rapidly activated SrcY419 in β-adrenergic receptor (ADRB) positive ovarian cancer cell lines, but not in ADRB-null cells. Confocal microscopy showed that Src was rapidly recruited to the cellular membrane after NE exposure in ADRB positive ovarian cancer cells. Furthermore, treatment with different ADRB agonists and blockers determined that ADRB2 is required for SrcY419 phosphorylation. Treatment with a cAMP agonist or PKA agonist/antagonists demonstrated that cAMP/PKA signaling is required for NE-induced Src activation. The unexpected Src activation via cAMP/PKA was found to be mediated by direct phosphorylation of SrcS17 following NE treatment. In Src-/- cells transiently expressing WT Src, NE caused SrcY419 phosphorylation, which was not observed when cells were transfected with a Src S17A construct. In order to investigate how S17 phosphorylation leads to Src activation, we performed molecular dynamic simulations and observed that upon SrcS17 phosphorylation, Src undergoes significant structural changes that expose its Y419 residue. To understand the functional consequences of stress-induced Src activation, we performed migration and invasion assays. Exposure to NE resulted in an increase in ovarian cancer cell migration and invasion that was completely abrogated by Src-targeted siRNA (P < 0.01). In various orthotopic mouse models of ovarian carcinoma, chronic restraint stress significantly increased tumor weights (P < 0.05). Increased tumor growth was completely blocked by Src silencing with Src siRNA-DOPC or by the non-specific beta-blocker, propranolol (P < 0.05). To test the clinical significance of our biological findings, we examined 91 epithelial ovarian cancer samples. Elevated pSrcY419 was associated with worse patient survival (P < 0.001), high tumoral NE levels (P < 0.001) and high scores on the Center for Epidemiologic Studies Depression Scale (P = 0.008). To examine the potential clinical impact of our findings, we investigated whether beta-blocker usage by patients affected cancer-related mortality. This analysis revealed that beta-blockers reduced mortality by 17% across all major cancer types and 14.6% among patients with ovarian and other gynecologic cancers. This work is the first to demonstrate that an ADRB-PKA-Src axis mediates the effect of chronic stress on tumor growth and progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 937. doi:10.1158/1538-7445.AM2011-937