phorbol and Prostatic-Neoplasms

Resveratrol is a natural compound that affects cellular Ca(2+) homeostasis and viability in different cells. This study examined the effect of resveratrol on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells. The Ca(2+)-sensitive fluorescent dye fura-2 was used to measure [Ca(2+)]i and WST-1 was used to measure viability. Resveratrol-evoked [Ca(2+)]i rises concentration-dependently. The response was reduced by removing extracellular Ca(2+). Resveratrol-evoked Ca(2+) entry was not inhibited by nifedipine, econazole, SKF96365 and the protein kinase C inhibitor GF109203X, but was nearly abolished by the protein kinase C activator phorbol 12-myristate 13 acetate. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone decreased resveratrol-evoked rise in [Ca(2+)]i. Conversely, treatment with resveratrol inhibited BHQ-evoked rise in [Ca(2+)]i. Inhibition of phospholipase C with U73122 did not alter resveratrol-evoked rise in [Ca(2+)]i. Previous studies showed that resveratrol between 10 and 100 µM induced cell death in various cancer cell types including PC3 cells. However, in this study, resveratrol (1-10 μM) increased cell viability, which was abolished by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-acetoxymethyl ester (BAPTA/AM). Therefore, it is suggested that in PC3 cells, resveratrol had a dual effect on viability: at low concentrations (1-10 µM) it induced proliferation, whereas at higher concentrations it caused cell death. Collectively, our data suggest that in PC3 cells, resveratrol-induced rise in [Ca(2+)]i by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry, via protein kinase C-regulated mechanisms. Resveratrol at 1-10 µM also caused Ca(2+)-dependent cell proliferation.

Topics: Apoptosis; Calcium; Calcium Signaling; Cell Line, Tumor; Cell Proliferation; Cell Survival; Homeostasis; Humans; Male; Phorbols; Prostatic Neoplasms; Protein Kinase C; Protein Kinase Inhibitors; Resveratrol; Stilbenes

Prostate-specific antigen (PSA) is the most sensitive marker available for monitoring the progression of prostate cancer and response to therapy. In a previous study, we demonstrated tissue-specific expression of PSA glycoprotein and mRNA and its regulation through the androgen receptor. In this study, we examine the effects of protein kinase A (PKA) and protein kinase C (PKC) on the androgen regulation of PSA in a human adenocarcinoma cell line, LNCaP. Northern blot analysis demonstrated that forskolin, an activator of PKA, had no effect on the androgen regulation of PSA. However, the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a direct activator of PKC, showed a time- and dose-dependent repression of the androgen regulation of PSA glycoprotein and mRNA. The biologically inactive phorbol ester, 4 alpha-phorbol-12,13-didecanoate, had no effect. Staurosporine, a PKC inhibitor, blocked the TPA-mediated repression of the androgenic stimulation of PSA glycoprotein. In addition, the calcium ionophore, A23187, was able to simulate the actions of TPA, presumably through activation of PKC via calcium mobilization. In summary, the androgenic regulation of PSA protein and mRNA is repressed by tumor-promoting phorbol esters through the PKC pathway. This indicates that the effects of TPA may be secondary to repressed gene transcription or altered mRNA stability. In addition, this study emphasizes that the androgenic regulation of PSA is complex and may involve other extracellular transduction signals.

Topics: Alkaloids; Antigens, Neoplasm; Biomarkers, Tumor; Calcimycin; Colforsin; Dose-Response Relationship, Drug; Down-Regulation; Humans; Male; Nandrolone; Phorbols; Prostate-Specific Antigen; Prostatic Neoplasms; RNA, Messenger; Staurosporine; Testosterone Congeners; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured