Prostate cancer patients have increased levels of stress and anxiety. Conversely, men who take beta blockers, which interfere with signaling from the stress hormones adrenaline and noradrenaline, have a lower incidence of prostate cancer; however, the mechanisms underlying stress-prostate cancer interactions are unknown. Here, we report that stress promotes prostate carcinogenesis in mice in an adrenaline-dependent manner. Behavioral stress inhibited apoptosis and delayed prostate tumor involution both in phosphatase and tensin homolog-deficient (PTEN-deficient) prostate cancer xenografts treated with PI3K inhibitor and in prostate tumors of mice with prostate-restricted expression of c-MYC (Hi-Myc mice) subjected to androgen ablation therapy with bicalutamide. Additionally, stress accelerated prostate cancer development in Hi-Myc mice. The effects of stress were prevented by treatment with the selective β 2 -adrenergic receptor (ADRB2) antagonist ICI118,551 or by inducible expression of PKA inhibitor (PKI) or of BCL2-associated death promoter (BAD) with a mutated PKA phosphorylation site (BAD S112A ) in xenograft tumors. Effects of stress were also blocked in Hi-Myc mice expressing phosphorylation-deficient BAD (BAD 3SA ). These results demonstrate interactions between prostate tumors and the psychosocial environment mediated by activation of an adrenaline/ADRB2/ PKA/BAD antiapoptotic signaling pathway. Our findings could be used to identify prostate cancer patients who could benefit from stress reduction or from pharmacological inhibition of stress-induced signaling.

The stress hormone epinephrine is known to elicit multiple systemic effects that include changes in cardiovascular parameters and immune responses. However, information about its direct action on cancer cells is limited. Here we provide evidence that epinephrine reduces sensitivity of cancer cells to apoptosis through interaction with ␤ 2 -adrenergic receptors. The antiapoptotic mechanism of epinephrine primarily involves phosphorylation and inactivation of the proapoptotic protein BAD by cAMP-dependent protein kinase. Moreover, BAD phosphorylation was observed at epinephrine concentrations found after acute and chronic psychosocial stress. Antiapoptotic signaling by epinephrine could be one of the mechanisms by which stress promotes tumorigenesis and decreases the efficacy of anti-cancer therapies.Epinephrine levels are sharply increased in response to acute stress and can be continuously elevated during persistent stress and depression (1, 2). Sustained increases of epinephrine were implicated in pathogenesis of stress-related immunosuppression proposed as the primary mechanism by which stress and depression may increase tumor incidence and promote metastatic growth (2, 3). However, several reports have questioned whether immunosuppression alone is sufficient to explain stress-induced tumor growth, and some studies have found no correlation between stress and cancer (2, 4). Thus, more information about the mechanisms by which stress hormones affect tumors is necessary to resolve the controversy over the connection between stress and cancer. One potential mechanism may involve direct effects of epinephrine on cancer cells.Cancer cell lines of various origins, including prostate tumors, express ␤ 2 -adrenergic receptors (␤ 2 -ARs) 4 that bind epinephrine and norepinephrine (5-7). ␤ 2 -ARs belong to superfamily A of seven-transmembrane G protein-coupled receptors (GPCRs) (8). Epinephrine binding leads to activation of GTPase and dissociation of ␣ and ␤␥ subunits of heterotrimeric G proteins. Depending on the cell context, this may trigger multiple signaling pathways, including the Ras/extracellular signal-regulated kinase, NFB, and cAMP-dependent protein kinase (PKA) pathways, which regulate diverse cellular responses, such as proliferation, differentiation, secretion, or apoptosis (9).Since resistance to apoptosis has been implicated in cancer pathogenesis (10), we decided to analyze the effects of the ␤ 2 -AR agonist epinephrine on apoptosis in prostate cancer cells. In this paper, we demonstrate that epinephrine reduces sensitivity of prostate cancer cells to apoptosis via ␤ 2 -AR/PKA signaling that triggers BAD phosphorylation at S112. This antiapoptotic mechanism operates in the prostate cancer cell lines LNCaP and C4-2 and in the breast cancer cell line MDA-MB231. Our findings suggest that stress may contribute to cancer etiology and therapeutic resistance by decreasing sensitivity of cancer cells to apoptosis. EXPERIMENTAL PROCEDURESCell Lines and Transfection-LNCaP and C4-2 cells were a gift from Leland C...

It has been demonstrated that vasoactive intestinal polypeptide, epidermal growth factor, and chronic activation of phosphatidylinositol 3-kinase can protect prostate cancer cells from apoptosis; however, the signaling pathways that they use and molecules that they target are unknown. We report that vasoactive intestinal polypeptide, epidermal growth factor, and phosphatidylinositol 3-kinase activate independent signaling pathways that phosphorylate the proapoptotic protein BAD. Vasoactive intestinal polypeptide operated via protein kinase A, epidermal growth factor required Ras activity, and effects of phosphatidylinositol 3-kinase were predominantly mediated by Akt. BAD phosphorylation was critical for the antiapoptotic effects of each signaling pathway. None of these survival signals was able to rescue cells that express BAD with mutations in phosphorylation sites, whereas knockdown of BAD expression with small hairpin RNA rendered cells insensitive to apoptosis. Taken together, these results identify BAD as a convergence point of several antiapoptotic signaling pathways in prostate cells.

Protection from apoptosis by receptor tyrosine kinases, resistant to the inhibition of phosphatidylinositol 3-kinase/Akt and Ras/MEK pathways, has been reported in several cell types, including fibroblasts and epithelial prostate cancer cells; however, mechanisms of this effect were not clear. Here we report that in prostate cancer cells, epidermal growth factor activates two antiapoptotic signaling pathways that impinge on the proapoptotic protein BAD. One signaling cascade operates via the Ras/MEK module and induces BAD phosphorylation on Ser 112 . Another pathway predominantly relies on Rac/ PAK1 signaling that leads to BAD phosphorylation on Ser 136 . Each of these two pathways is sufficient to protect cells from apoptosis, and therefore both have to be inhibited simultaneously to block epidermal growth factor-dependent survival. Redundancy of antiapoptotic signaling pathways should be considered when therapies targeting antiapoptotic mechanisms are designed.

The phosphatidylinositol-3-kinase/Akt (PI3K/Akt) pathway is constitutively activated in a substantial proportion of prostate tumors and is considered a key mechanism supporting progression toward an androgen-independent status, for which no effective therapy is available. Therefore, PI3K inhibitors, alone or in combination with other cytotoxic drugs, could potentially be used to treat cancer with a constitutive activated PI3K/Akt pathway. To selectively target advanced prostate tumors with a constitutive activated PI3K/Akt pathway, we generated a prostate cancer-specific PI3K inhibitor by coupling the chemically modified form of the quercetin analog LY294002 (HO-CH2-LY294002, compound 8) with the peptide Mu-LEHSSKLQL, in which the internal sequence HSSKLQ is a substrate for the prostate-specific antigen (PSA) protease. The result is a water-soluble and latent PI3K inhibitor prodrug (compound 11) which activation is dependent on PSA cleavage. Once activated, the L-O-CH2-LY294002 (compound 10) can specifically inhibit PI3K in PSA-secreting prostate cancer cells and induced apoptosis with a potency comparable to the original LY294002 compound.