ucn-1028-c and hypericin

Hypericin and tamoxifen are experimental agents for the adjuvant chemotherapy of malignant glioma. We report that hypericin and tamoxifen induce apoptosis of 7 human malignant glioma cell lines in a concentration- and time-dependent manner. Illumination is essential for the cytotoxicity of hypericin but not tamoxifen. Apoptosis is unaffected by inhibitors of RNA and protein synthesis or free radical scavengers, does not require wild-type p53 activity, and occurs in glioma cells expressing high levels of bcl-2. There is no correlation between hypericin and tamoxifen-induced cytotoxicity and inhibition of protein kinase C (PKC). Ectopic expression of a murine bcl-2 transgene provides modest protection from tamoxifen but does not affect hypericin toxicity. Hypericin and tamoxifen do not modulate glioma cell killing induced by tumor necrosis factor-alpha (TNF-alpha) or CD95 ligand. Both drugs augment the acute cytotoxicity of various cancer chemotherapy drugs but fail to shift their EC50 values in modified colony formation assays. These data do not provide further supportive evidence how to enhance the limited efficacy of tamoxifen treatment for human malignant glioma. However, hypericin is a promising agent for the treatment of malignant glioma if local photodynamic activation of hypericin in the glioma tissue can be achieved.

Topics: Anthracenes; Antibiotics, Antineoplastic; Antineoplastic Agents; Antineoplastic Agents, Hormonal; Apoptosis; bcl-2-Associated X Protein; Cell Division; Drug Resistance; fas Receptor; Glioma; Humans; Light; Naphthalenes; Perylene; Protein Kinase C; Protein Synthesis Inhibitors; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; RNA; Tamoxifen; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Topics: Alkaloids; Alkylating Agents; Anthracenes; Benzophenanthridines; Binding Sites; Carcinogens; Cysteine; Enzyme Inhibitors; Hydrogen Peroxide; Isoenzymes; Isoquinolines; Naphthalenes; Nitric Oxide; Oxidants; Periodic Acid; Perylene; Phenanthridines; Phorbol Esters; Phosphotransferases; Protein Kinase C

The present studies were undertaken to characterize further the potential role of protein kinase C (PKC) in the regulation of apoptosis in HL-60 promyelocytic leukemia cells. The capacity of acute exposure to specific and nonspecific pharmacological inhibitors of PKC to promote apoptotic DNA fragmentation was examined both quantitatively and qualitatively and correlated with effects on cellular differentiation and proliferation. Incubation of HL-60 cells for 6 h with chelerythrine and calphostin C (highly specific inhibitors that act at the regulatory domain) or H7 and gossypol (nonspecific inhibitors that act at the PKC catalytic domain) produced concentration-dependent increases in DNA fragmentation. Induction of DNA fragmentation by chelerythrine, calphostin C, and gossypol was biphasic, resulting in a sharp decline in effect at concentrations above 5 microM, 0.1 microM, and 100 microM, respectively, whereas maximal and more stable effects were observed in response to H7 (100 microM). A 6-h exposure to staurosporine, a nonspecific but potent PKC inhibitor, failed to induce DNA fragmentation at concentrations generally used to achieve maximal inhibition of enzyme activity (e.g., 50 nM) but promoted fragmentation at considerably higher concentrations (e.g., > or = 200 nM). In contrast, 6-h exposures to the nonspecific protein kinase inhibitor hypericin (0.1 to 100 microM) or to the nonspecific inhibitor of protein kinase A, HA1004 (50 microM), were without effect on DNA fragmentation. DNA obtained from cells exposed to chelerythrine (5 microM), calphostin C (100 nM), H7 (50 microM), gossypol (50 microM), and staurosporine (200 nM)--but not hypericin (25 microM)--exhibited clear evidence of internucleosomal DNA cleavage on agarose gel electrophoresis; moreover, these cells exhibited the classical morphological features of apoptosis (cell shrinkage, nuclear condensation, and the formation of apoptotic bodies). All of the PKC inhibitors that induced apoptosis, and one of the inhibitors that did not (hypericin), substantially inhibited HL-60 cell clonogenicity at the concentrations evaluated. None of the agents tested induced cellular maturation as assessed by nonspecific esterase and nitro-blue tetrazolium positivity. DNA fragments obtained from cells exposed to specific and nonspecific PKC inhibitors possessed predominantly 5'-phosphate termini, consistent with the action of a Ca(2+)-/Mg(2+)-dependent endonuclease. Finally, Northern blot analysis revealed

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Alkaloids; Anthracenes; Antineoplastic Agents; Apoptosis; Benzophenanthridines; Cell Differentiation; Cell Line; Cyclic AMP-Dependent Protein Kinases; DNA Damage; DNA, Neoplasm; Enzyme Inhibitors; Gossypol; Humans; Isoquinolines; Leukemia, Promyelocytic, Acute; Naphthalenes; Perylene; Phenanthridines; Piperazines; Polycyclic Compounds; Protein Kinase C; Staurosporine; Time Factors; Tumor Cells, Cultured