We have demonstrated that epinephrine at concentrations observed during stress induces PKA-dependent phosphorylation of the pro-apoptotic protein BAD and protects prostate cancer cells from apoptosis (JBC2007 in """"""""appendix""""""""). Furthermore, recent in vivo experiments have shown that subjecting mice to stress or injecting with epinephrine protected prostate cancer xenografts from the anti-tumor effects of PI3K inhibitor LY294002. Based on these observations we hypothesize that increased epinephrine levels protect prostate cancer cells from apoptosis via PKA/BAD signaling and, as a result, contribute to the progression of prostate cancer and increase the resistance of cancer cells to therapies.
Aim 1. Examine mechanisms of anti-apoptotic signaling by epinephrine in prostate cancer cells. In this aim we will determine the role of PKA/BAD signaling in the anti-apoptotic effect of epinephrine and examine whether and how epinephrine signaling is modulated by other stress hormones, androgens and stroma.
Aim 2. Determine whether stress activates anti-apoptotic signaling in prostate tumors in vivo, and assess the role of epinephrine in stress-induced effects. In this aim we will test whether PKA/BAD pathway is activated by stress in prostate cancer models in vivo and whether epinephrine signaling is necessary and sufficient for this activation. Experiments will be conducted in mice with C4-2Luc xenografts, in mice with prostate specific deletion of PTEN (PTENp-/- mice), and in mice with prostate-specific expression of c-myc (Lo-Myc mice).
Aim 3. Determine effects of stress/epinephrine on the therapeutic sensitivities and growth of prostate tumors and contribution of PKA/BAD signaling to stress effects. In this aim we will test whether stress negates the anti-tumor effects of PI3K inhibition in PTEN-negative prostate tumors and speeds up the development of prostate tumors driven by c-myc expression. We will also test the role of PKA/BAD signaling in tumor-protecting effects of stress in vivo. The novelty of this proposal lies in: a) the testing of a new concept that epinephrine elevated in response to emotional stress protects prostate cancer cells from apoptosis;and b) characterization of the signaling mechanism responsible for this effect. Significance. If the connection between emotional stress and sensitivity of prostate cancer to apoptosis is established, it will open the long-term possibility that management of stress levels or pharmacological inhibition of stress hormones signaling may improve outcomes of prostate cancer therapy and slow progression of prostate cancer.
Currently information on the mechanisms by which emotional stress affects cancer is limited. The novelty of this proposal lies in: a) the testing of a new concept that epinephrine elevated in response to emotional stress protects prostate cancer cells from apoptosis;and b) characterization of the signaling mechanism responsible for this effect. If the connection between emotional stress and sensitivity of prostate cancer to apoptosis is established, it will open the long-term possibility that management of stress levels or pharmacological inhibition of stress hormones signaling may improve outcomes of prostate cancer therapy and slow progression of prostate cancer.
