Prostaglandin E2 regulates cellular migration via induction of vascular endothelial growth factor receptor-1 in HCA-7 human colon cancer cells

An important event in the development of tumors is angiogenesis, or the formation of new blood vessels. Angiogenesis is also known to be involved in tumor cell metastasis and is dependent upon the activity of the vascular endothelial growth factor (VEGF) signaling pathway. Studies of mice in which the EP3 prostanoid receptors have been genetically deleted have shown a role for these receptors in cancer growth and angiogenesis. In the present study, human colon cancer HCA-7 cells were used as a model system to understand the potential role of EP3 receptors in tumor cell migration. We now show that stimulation of HCA-7 cells with PGE₂ enhanced the up-regulation of VEGF receptor-1 (VEGFR-1) expression by a mechanism involving EP3 receptor-mediated activation of phosphatidylinositol 3-kinase and the extracellular signal-regulated kinases. Moreover, the PGE₂ stimulated increase in VEGFR-1 expression was accompanied by an increase in the cellular migration of HCA-7 cells. Given the known involvement of VEGFR-1 in cellular migration, our results suggest that EP3 receptors may contribute to tumor cell metastasis by increasing cellular migration through the up-regulation of VEGFR-1 signaling.     

Prostaglandin E₂ regulates cellular migration via induction of vascular endothelial growth factor receptor-1 in HCA-7 human colon cancer cells

An important event in the development of tumors is angiogenesis, or the formation of new blood vessels. Angiogenesis is also known to be involved in tumor cell metastasis and is dependent upon the activity of the vascular endothelial growth factor (VEGF) signaling pathway. Studies of mice in which the EP3 prostanoid receptors have been genetically deleted have shown a role for these receptors in cancer growth and angiogenesis. In the present study, human colon cancer HCA-7 cells were used as a model system to understand the potential role of EP3 receptors in tumor cell migration. We now show that stimulation of HCA-7 cells with PGE? enhanced the up-regulation of VEGF receptor-1 (VEGFR-1) expression by a mechanism involving EP3 receptor-mediated activation of phosphatidylinositol 3-kinase and the extracellular signal-regulated kinases. Moreover, the PGE? stimulated increase in VEGFR-1 expression was accompanied by an increase in the cellular migration of HCA-7 cells. Given the known involvement of VEGFR-1 in cellular migration, our results suggest that EP3 receptors may contribute to tumor cell metastasis by increasing cellular migration through the up-regulation of VEGFR-1 signaling.     

Suppressive effects of peptide antibiotics against proliferation and cytokine production in mitogen-activated human peripheral-blood mononuclear cells

Certain kinds of peptide antibiotics are suggested to have immunomodulatory effects; however, few studies have been carried out systemically to evaluate the antiproliferative effects of peptide antibiotics in human lymphoid cells. The suppressive efficacies of nine peptide antibiotics and seven non-antibiotic peptides against proliferation of human peripheral-blood mononuclear cells (PBMCs) stimulated with T cell mitogen were examined in vitro. Nigericin (CAS 28643-80-3), valinomycin (CAS 2001-95-8), gramicidin D (CAS 1405-97-6), and tyrothricin (CAS 1404-88-2) strongly inhibited the proliferation of concanavalin A-stimulated PBMCs with IC50 values of 0.15-11.2 ng/ml, while these antibiotics did not show cytotoxicity at 10 000 ng/ml. The IC50 value of the immunosuppressant cyclosporine (CAS 59865-13-3) was 5.2 ng/ml. Virginiamycin (CAS 11006-76-1) and gramicidin S (CAS 113-73-5) moderately inhibited PBMC-proliferation with IC50 values of 1000 and 1900 ng/ml, respectively. On the other hand, bacitracin (CAS 1405-87-4), capreomycin (CAS 11003-38-6), polymyxin B (1404-26-8), angiotensin II antipeptide (CAS 121379-63-3), angiotensin III antipeptide (CAS 133605-55-7), fibrinogen binding inhibitor peptide (CAS 89105-94-2), LH-RH (CAS 71447-49-9), pepstatin A (CAS 26305-03-3), oxytocin (CAS 50-56-6), and vasopressin (CAS 16679-58-6) showed little or no suppressive effect on PBMC-proliferation. Nigericin and valinomycin decreased the concentrations of interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-10, and IL-17 in the culture medium with IC50 values less than 0.01 ng/ml. Nigericin also decreased the concentrations of IL-4 and IL-6 with IC50 values of less than 1 ng/ml. The results show that peptide antibiotics such as nigericin and valinomycin efficiently suppress the production of several cytokines and proliferation in mitogen-stimulated human PBMCs.     

Antiproliferative and anti-invasive effects of inorganic and organic arsenic compounds on human and murine melanoma cells in vitro

Objectives For patients with advanced melanoma, no treatment options are available at present that provide either sufficient response rates or a significant prolongation of overall survival. The present study examines the effects of two inorganic and six organic arsenic compounds on cell proliferation and cell invasion of melanoma cells in vitro. Methods The effects of arsenic compounds on proliferation of human melanoma A375 cells and murine melanoma B16F10 cells were examined by MTT assay and 5‐bromo‐2′‐deoxyuridine (BrdU) incorporation assay, and the effects of the compounds on cell invasion were examined by the Boyden chamber invasion assay. The amounts of active matrix metalloproteinase (MMP)‐2 and pro‐MMP‐2 in the culture supernatant of A375 cells were determined by an MMP‐2 activity assay system. Key findings Arsenate and arsenic trioxide (As₂O₃) inhibited the proliferation of A375 and B16F10 cells significantly at concentration ranges of 0.1–20 µg/ml (P < 0.001), while the organic compounds arsenobetaine, arsenocholine, dimethylarsinic acid, methylarsonic acid, tetramethylarsonium and trimethylarsine oxide did not show any inhibitory effects even at 20 µg/ml. Cell invasion of A375 and B16F10 cells through a layer of collagen IV was significantly inhibited by 0.1–20 µg/ml of arsenate or As₂O₃ (P < 0.05), while the organic compounds did not inhibit cell invasion. Arsenate or As₂O₃ at 0.2–10 µg/ml significantly inhibited the amount of active MMP‐2 and pro‐MMP‐2 secreted into the A375 cell culture supernatant (P < 0.05). Conclusions Our findings show that the inorganic arsenic compounds arsenate and As₂O₃ inhibit cell proliferation and prevent the invasive properties of melanoma cells, possibly by decreasing MMP‐2 production from the cells.     

Involvement of different human glutathione transferase isoforms in the glutathione conjugation of reactive metabolites of troglitazone

Null mutation of glutathione transferase (GST) M1 and GSTT1 was reported to correlate statistically with an abnormal increase in the plasma levels of alanine aminotransferase or aspartate aminotransferase caused by troglitazone in diabetic patients (Clin Pharmacol Ther, 73:435-455, 2003). This clinical evidence leads to the hypothesis that GSH conjugation catalyzed by GSTT1 and GSTM1 has a role in the elimination of reactive metabolites of troglitazone. However, the contribution of GST isoforms expressed in human liver to the detoxification of reactive metabolites of troglitazone has not yet been clarified. We investigated the involvement of human GST isoforms in the GSH conjugation of reactive metabolites of troglitazone using recombinant GST enzymes. Five reported GSH conjugates of reactive metabolites were produced from troglitazone after incubation with liver microsomes, NADPH, and GSH in a GSH concentration-dependent manner. Addition of human recombinant GSTA1, GSTA2, GSTM1, or GSTP1 protein to the incubation mixture further increased the GSH conjugates. However, the addition of GSTT1 did not show any catalytic effect. It is of interest that one of the reactive metabolites with a quinone structure was predominantly conjugated with GSH by GSTM1. Thus, we demonstrated that the GST isoforms contributed differently to the GSH conjugation of individual reactive metabolites of troglitazone, and GSTM1 is the most important GST isoform in the GSH conjugation of a specific reactive metabolite produced from the cytotoxic, quinone-form metabolite of troglitazone.     

Decrease of guanylyl cyclase β1 subunit and nitric oxide (NO)-induced relaxation in mouse rectum with colitis and its reproduction on long-term NO treatment

Nitric oxide (NO) influences motility in the colon in patients with ulcerative colitis, but the exact mechanism involved remains unknown. Colitis was induced in mice by the oral administration of 2.5% dextran sodium sulfate (DSS), and the motility in longitudinal preparations from rectum and distal colon and expression of β1 subunit of soluble guanylyl cyclase (sGCβ1) were analyzed. Electrical stimulation (ES) caused a transient relaxation via the NO pathway in both rectum and colon from control mice. Stimulation with sodium nitroprusside (SNP) caused relaxation in the two regions, and the half-time (T _1/2) of the maximal relaxation induced by 100 μM SNP was 8.1 ± 1.0 s in rectum. DSS treatment (1) abolished the ES-induced relaxation, but not dibutyryl cyclic GMP-induced response, in both regions, (2) decreased the maximal response to SNP accompanied by a loss of immunoreactive sGCβ1 protein in rectum, but did not affect the amplitude of the relaxant response or the protein in distal colon, and (3) caused an increase in the T _1/2 value in response to SNP in both regions. Pretreatment of both preparations from control mice with 600 μM SNP for 30 min decreased both ES- and SNP-induced relaxation, SNP-induced cyclic GMP formation, and immunoreactive sGCβ1 levels. NO-mediated relaxation was impaired by a dysfunctional sGC with and without a loss of immunoreactivity to sGCβ1 in rectum and colon from DSS-treated mice, respectively. Long-term exposure of the tissues with an excess amount of NO changes the sGC-mediated relaxation.     

Comparison of speedy PCR-ssp method and serological typing of HLA-A24 for Japanese cancer patients

Human leukocyte antigen (HLA) typing is essential to carry out HLA-class I restricted antigenic peptide-based cancer immunotherapy. To establish a one-step polymerase chain reaction-sequence-specific primer (PCR-SSP) method, we designed two novel HLA-A24-specific primer sets and determined the optimal conditions for specific amplification. Then, we performed HLA-A24 typing of two healthy donors' and 17 cancer patients' peripheral blood with serological typing and PCR-SSP typing. Eleven of the 19 cases were determined HLA-A24-positive by the PCR-SSP method precisely; however, five cases showed false positive with serological analysis. Thus, for HLA-A24 typing in the Japanese population, the PCR-SSP method is faster and more accurate than serological typing.