Cyclooxygenase 2 rescues LNCaP prostate cancer cells from sanguinarine-induced apoptosis by a mechanism involving inhibition of nitric oxide synthase activity

Expression of cyclooxygenase-2 (Cox-2), an inducible enzyme responsible for the production of prostaglandins from arachidonic acid, is elevated in human prostate tumor samples. The aim of this study was to investigate whether expression of Cox-2 is effective against prostate cancer cell apoptosis triggered by sanguinarine, the quaternary benzophenanthridine alkaloid with antineoplastic properties. Sanguinarine effectively induced apoptosis in LNCaP human prostate cancer epithelial cells as assessed by caspase-3 activation assay, Annexin V staining assay, or by visual analysis for the apoptotic morphology changes. Sanguinarine-mediated apoptosis was associated with the increase of nitric oxide (NO) formation in prostate cancer cells as assessed by measurements of nitrites with Sievers nitric oxide analyzer as well as flow cytometry analysis using NO fluorescent sensor. Activation of NO synthase (NOS) activity was crucial for sanguinarine-induced cell death because NOS inhibitor L-NMMA efficiently protected cells from apoptosis. Adenovirus-mediated transfer of Cox-2 into LNCaP cells inhibited sanguinarine-induced apoptosis and prevented an increase in NO production. Surprisingly, NO donors failed to induce apoptosis in LNCaP cells, suggesting that constitutive NO generation is not sufficient for triggering apoptosis in these cells. Besides NO generation, NOS is also capable of producing superoxide radicals. Sanguinarine-induced production of superoxide radicals, and the addition of MnTBAP, a scavenger of superoxide radicals, efficiently inhibited sanguinarine-mediated apoptosis. These results suggest that Cox-2 expression rescues prostate cancer cells from sanguinarine-induced apoptosis by a mechanism involving inhibition of NOS activity, and that coadministration of Cox-2 inhibitors with sanguinarine may be developed as a strategy for the management of prostate cancer.     

Human T-cell leukemia virus (HTLV-I) p24 antibody in New York City blood product recipients

Human T-cell leukemia virus (HTLV-I) is known to be associated with certain hematologic malignancies, and a related virus, HTLV-III/LAV, might be the cause of AIDS. Some persons with AIDS have had evidence of HTLV-I infection. Unrelated to these findings, it has been suggested that HTLV-I is transmitted via blood products. We therefore evaluated the serologic status to the HTLV-I core antigen p24 of 48 persons with hemophilia (Hem A) receiving factor concentrate therapy (a group at risk for AIDS), 49 persons with beta-thalassemia major (Thal) receiving frozen packed red blood cells therapy (FPRC), 26 patients with sickle cell anemia (SCA) receiving FPRC, and 18 persons not receiving any blood products. All participants were clinically well; only one had a risk factor other than hemophilia for AIDS, and all were from New York City, an area with a high incidence of AIDS. No Hem A or nontransfused persons had serum antibody to HTLV core p24 antigen; three with Thal and one with SCA were antibody-positive. These results were confirmed by both radioimmunoprecipitation and Western blot techniques. Positive serology did not correlate with any immune findings or quantity of blood products used. These data support that HTLV-I is preferentially transmitted through cellular blood products and that it is an infection for which cellular blood product recipients in at least some areas of the United States are at risk. Concentrate products appear free of transmission risk relative to cellular blood products, but we cannot be certain that this safety is absolute. The public health implications of blood product transmission of HTLV-I merit active, long-term investigation.     

4-Amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1): a cytotoxic agent towards cancer cells and a probe for tubulin-microtubule system

Microtubule binding drugs are of special interest as they have important roles in the modulation of cellular functions and many of them act as anticancer agents. 4-Amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1) was identified as one of the active compounds from a series of diaminoketothiazoles in a cell-based screening assay to discover cytotoxic compounds. DAT1 shows cytotoxicity with GI(50) values ranging from 0.05 to 1 microM in different malignant cell lines with an average value of 0.35 microM. It blocks mitosis in the prometaphase and metaphase stages. In HeLa cells, DAT1 blocks the spindle function by disturbing spindle microtubule and chromosome organization. The drug also inhibits assembly of brain microtubules and binds tubulin specifically at a single site with induction of fluorescence. The dissociation constant of DAT1 binding to tubulin was determined as 2.9+/-1 microM at 24 degrees C. The binding site of DAT1 on tubulin overlaps with that of the conventional colchicine-binding site. DAT1 can thus be considered as a lead compound of a new class of small molecules and this study can be used as a step to develop potent antimitotic agents for the control of cytoskeletal functions and cell proliferation. It would also be an interesting probe for the structure-function studies of tubulin-microtubule system.