cyclic-gmp and Carcinoma--Renal-Cell

Phosphodiesterase type 5 (PDE5) plays a key role in regulating the intracellular cyclic GMP (cGMP) concentration, which influences anti-proliferative and pro-apoptotic mechanisms in multiple carcinomas. PDE5 inhibitors, such as exisulind and its analogs have anticancer activities. In this study, we found that suppressing PDE5 gene expression by PDE5 siRNA inhibited cell proliferation and induced apoptosis in OS-RC-2 human renal cell carcinoma cells. These effects were enhanced by 8-Br-cGMP, a cell membrane permeable cGMP derivative, and were inhibited by KT5823, a protein kinase G (PKG) inhibitor, indicating that PKG was activated by intracellular cyclic GMP. In addition, there was a reduction in both the mRNA and protein expression of cyclin D1, while p21 protein expression was increased; the reduction in cyclin D1 expression was blocked by the proteasome inhibitor, MG132, or c-Jun N-terminal kinase (JNK) inhibitor; both β-catenin and JNK were phosphorylated by activated PKG. Furthermore, p21 protein expression was decreased in Sp1 siRNA transfected-cells treated with 8-Br-cGMP, indicating that p21 may be partly controlled by the PKG activation through Sp1. Furthermore, we found that PKG Iβ was responsible for the anticancer activities. Our findings indicate that the downregulation of PKG-activated genes, such as cyclin D1 partly accounts for the pro-apoptotic effects in PDE5 siRNA-transfected OS-RC-2 cells.

Topics: Antineoplastic Agents; Apoptosis; beta Catenin; Carbazoles; Carcinoma, Renal Cell; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Gene Expression Regulation; Humans; JNK Mitogen-Activated Protein Kinases; Phosphodiesterase 5 Inhibitors; Phosphorylation; Signal Transduction; Sp1 Transcription Factor; Sulindac

Despite increasing use of "targeted therapy," interleukin-2 (IL-2) is unique, because this cytokine can induce long-term remissions in 5% to 7% of patients with metastatic melanoma and renal cancer. Clinical use of IL-2 is limited by severe toxicities, such as hypotension and vascular leak syndrome (VLS). Nitric oxide seems to be involved in the pathogenesis of these toxicities. On the basis of previous studies, we hypothesized that the endothelial nitric oxide synthase (eNOS) is the major source of nitric oxide. Mice with a knockout of the eNOS isoenzyme were treated with IL-2 (800,000 IU twice daily for 5 d). Blood pressure and vascular leak were measured. Inhibitors of superoxide, nitric oxide, and soluble guanylate cyclase were used to probe the mechanism. These experiments showed that IL-2 treatment increased eNOS messenger ribonucleic acid expression and nitric oxide metabolite excretion in eNOS knockout mice. Unlike normal and inducible nitric oxide synthase knockout mice, eNOS knockout mice proved resistant to IL-2-induced hypotension and vascular leak. Although hypotension seems to be mediated by superoxide or peroxynitrite, vascular leak seemed to be mediated by nitric oxide. Inhibition of guanylate cyclase and cyclic guanylate monophosphate formation during IL-2 treatment using methylene blue (MB)-inhibited vascular leak. MB treatment did not interfere with IL-2-induced antitumor mechanisms. Our experiments established that eNOS is a key mediator of IL-2-induced VLS and hypotension. A clinical trial of MB infusion during IL-2 therapy is currently being planned.

Topics: Animals; Blood Pressure; Capillary Leak Syndrome; Carcinoma, Renal Cell; Cyclic GMP; Enzyme Inhibitors; Guanylate Cyclase; Humans; Hypotension; Interleukin-2; Manganese; Melanoma; Methylene Blue; Mice; Mice, Inbred Strains; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase Type III; omega-N-Methylarginine; Organometallic Compounds; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Soluble Guanylyl Cyclase; Superoxides

Therapies that target the vascular endothelial growth factor (VEGF) pathway cause hypertension, but the mechanism remains unknown. This cross-sectional study tested the hypothesis that VEGF inhibition causes hypertension by suppressing VEGF-mediated vasodilatory pathways. Urine was collected from 80 patients with metastatic renal cell carcinoma from 2002 to 2009, 40 at baseline and 40 while on VEGF inhibitors. Measured urinary biomarkers include albumin, metabolites of the nitric oxide (NO) pathway and its downstream effector cGMP, and prostaglandin pathway biomarkers prostaglandin E2, 6-keto prostaglandin F1α, and cAMP, all normalized to urinary creatinine. The mean age in both groups was 61.8 years, 76% were men, and urinary albumin was higher in patients receiving VEGF inhibitors (median: 18.4 versus 4.6 mg/g; P = 0.009). cGMP/creatinine was suppressed in patients on VEGF inhibitors (0.28 versus 0.39 pmol/μg; P = 0.01), with a trend toward suppression of nitrate/creatinine (0.46 versus 0.62 μmol/mg; P = 0.09). Both comparisons were strengthened when patients on bevacizumab were excluded, and only those receiving small molecule tyrosine kinase inhibitors were analyzed (cGMP/creatinine: P = 0.003; nitrate/creatinine: P = 0.01). Prostaglandin E2, 6-keto prostaglandin F1α, and cAMP did not differ between groups. These results suggest that hypertension induced by VEGF inhibitors is mediated by suppression of NO production. Prospective studies are needed to explore whether these biomarkers may be useful predictors of efficacy in patients receiving VEGF-targeted therapies.

Topics: 6-Ketoprostaglandin F1 alpha; Albuminuria; Angiogenesis Inhibitors; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Bevacizumab; Carcinoma, Renal Cell; Cross-Sectional Studies; Cyclic AMP; Cyclic GMP; Dinoprostone; Enzyme Inhibitors; Female; Humans; Hypertension; Kidney Neoplasms; Male; Middle Aged; Nitric Oxide; Protein-Tyrosine Kinases; Vascular Endothelial Growth Factor A

The present studies were undertaken to assess the effects of atrial natriuretic factor (ANF) on erythropoietin (Ep) secretion in Ep-producing renal carcinoma (RC) cells using a sensitive radioimmunoassay for Ep. Human ANF produced a significant dose-related increase in Ep secretion at concentrations of 10(-7) and 10(-6) M when compared with vehicle controls. ANF (greater than or equal to 10(-9) M) also significantly increased the intracellular guanosine 3',5'-cyclic monophosphate (cGMP) concentration after 5-min incubation with the RC cells. Scatchard analysis of the human 125I-labeled ANF binding data indicated that the RC cells contain a single class of binding sites with a dissociation constant (Kd) of 93 +/- 1 pM and a binding capacity of 2,190 +/- 750 sites/cell. Incubation of the RC cells with 8-bromo-cGMP in concentrations of 10(-7)-10(-5) M also produced a significant dose-related enhancement of Ep secretion. These findings suggest that the increase in Ep secretion in response to ANF can be attributed, at least in part, to activation of guanylate cyclase, which is coupled to specific ANF receptors on the RC cell.

Topics: Atrial Natriuretic Factor; Carcinoma, Renal Cell; Cyclic GMP; Erythropoietin; Humans; Kidney Neoplasms; Kinetics; Lung Neoplasms; Tumor Cells, Cultured