Abstract SY04-01: Behavioral stress protects prostate cancer cells from apoptosis

Abstract

Abstract Behavioral stress has been long implicated in cancer pathogenesis, yet mechanistic aspects of stress/tumor interactions are understudied. Several recent publications described effects of stress hormone epinephrine on tumor stroma components: vasculature and immune cells (Lutgendorf 2010; Sloan 2010; Thaker 2006); however, it was not clear whether epinephrine could influence cancer cells directly. Earlier we reported that epinephrine inhibits apoptosis in prostate cancer cells in tissue culture (Sastry 2007). It was unknown, however, if increase of epinephrine observed during behavioral stress could activate antiapoptotic signaling in prostate tumors and diminish efficacy of anticancer therapies. We will present evidence that subjecting mice to behavioral stress increases resistance of PTEN-deficient C42Luc prostate cancer xenografts to treatments with PI3K inhibitors. PI3K inhibitors induced apoptosis in prostate cancer xenografts; while subjecting mice to stress at the time of administration of PI3K inhibitors significantly reduces tumor cell loss. Effects of behavioral stress are mediated by epinephrine that inhibits apoptosis in prostate cancer xenografts. Antiapoptotic effects of stress/epinephrine are mediated via β2-adrenergic receptor (β2AR) and cAMP-dependent protein kinase (PKA) pathway, which in turn induced phosphorylation of BH3-only protein BAD. This study has following novel aspects: 1) It is a first report on activation of β2AR/PKA/BAD antiapoptotic pathway in tumors in vivo. 2) It is a first report that demonstrates effect of behavioral stress on therapy resistance of prostate tumors in mouse models. Information on antiapoptotic signaling by β2AR/PKA/BAD pathway activated by stress levels of epinephrine establishes a foundation for clinical trials that examine effects of stress reduction and/or administration of β2AR-antagonists on treatment efficacy in prostate cancer patients.