ascorbic-acid and zilascorb

Zilascorb(2H) is a benzaldehyde derivative giving rise to strong protein synthesis inhibition. It has shown antitumor activity against human malignant melanoma grown as xenografts in nude mice. The effect was manifest only after prolonged daily treatment and was quickly reversible when treatment was stopped. Drug-induced fever was the dose-limiting toxicity observed during clinical phase I studies of zilascorb(2H). The object of the present study was to assess antitumor activity, safety and tolerability of the drug in melanoma patients. Sixteen patients with disseminated malignant melanoma were included, all presenting with WHO performance status 0-2 and adequate organ functions. Previous chemo- or radiotherapy was accepted, while patients with known CNS metastases were excluded. Due to its low solubility and quickly reversible activity, zilascorb(2H) 1400 mg was infused by the patients twice daily through a venous access port for up to 12 weeks. Induction of tumor regression was demonstrated in one patient, who was, however, withdrawn from treatment after 2 weeks because of recurrent fever and fatigue. All the 12 patients evaluable for antitumor activity had progressive disease. Zilascorb(2H) was well tolerated, except for fever reactions and reversible liver toxicity. Most patients learned quickly how to handle a venous access port, but daily self-administration of i.v. infusions became too cumbersome to justify further patient inclusion despite the tumor regression observed. We conclude that zilascorb(2H) seems to have the potential for antitumor activity in metastatic malignant melanoma and is well tolerated. Daily self-administration of drug infusions is not desirable for long periods and zilascorb(2H) tablets have been developed. Because of its favorable toxicity profile, especially compared to other protein synthesis inhibitors, zilascorb(2H) may be particularly interesting for combinations with other anticancer drugs.

Topics: Adult; Aged; Antineoplastic Agents; Ascorbic Acid; Benzylidene Compounds; Drug Administration Schedule; Female; Humans; Male; Melanoma; Middle Aged; Protein Synthesis Inhibitors

The new anti-cancer drug zilascorb(2H) has shown promising activity in preclinical models. Its putative mechanism of action is reversible protein synthesis inhibition and long-term treatment is required. As a clinical treatment modality, long-term daily zilascorb(2H) infusions, as used in previous studies, are not regarded feasible. Therefore, an oral formulation of the drug was developed, and pharmacokinetic profile, toxicity and antitumor activity of zilascorb(2H) tablets were studied. Thirteen patients with advanced solid cancer not amenable to established therapy, but with adequate performance status and organ functions, were included. The treatment was given as a daily i.v. zilascorb(2H) infusion for 5 days, followed by zilascorb(2H) tablets twice daily for 3 months. Blood and urine sampling was performed when estimated plasma steady-state level was reached for each formulation, respectively. Analyses of drug concentrations in plasma and urine were performed by high performance liquid chromatography. Zilascorb(2H) in tablet formulation had a bioavailability of 32%, was quickly absorbed and slowly eliminated. Concomitant use of the H2-blocker ranitidine possibly enhanced bioavailability. Zilascorb(2H) was well tolerated. Two patients experienced drug-related fever, disturbing the treatment schedule for one of them. Moderate nausea was reported. One objective response was obtained. The bioavailability of zilascorb(2H) tablets was satisfactory. The principle of oral administration of zilascorb(2H) is feasible for long-term treatment and the side effects are acceptable. The mechanisms of action and the very low toxicity of the drug makes it a candidate for combination with other anticancer agents.

Topics: Adolescent; Adult; Aged; Antineoplastic Agents; Area Under Curve; Ascorbic Acid; Benzylidene Compounds; Biological Availability; Chromatography, High Pressure Liquid; Female; Humans; Male; Middle Aged; Neoplasms

Our previous studies have demonstrated the oxidative stress properties of sodium ascorbate (SAA) and its benzaldehyde derivative (SBA) on cancer cell lines, but the molecular mechanisms mediating their cytotoxicity remain unclear. In this study, we treated human colon cancer HT-29 cells with SAA and SBA, and found a significant exposure time-dependent increase of cytotoxicity in both treatments, with a higher cytotoxicity for 24 h with SAA (IC(50) = 5 mM) than SBA (IC(50) = 10 mM). A short-term treatment of cells with 10 mM SAA for 2 h revealed a destabilization of the lysosomes and subsequent induction of cell death, whereas 10 mM SBA triggered a remarkable production of reactive oxidative species, phosphorylation of survival kinase AKT, expression of cyclin kinase-dependent inhibitor p21, and induction of transient growth arrest. The crucial role of p21 mediating this cytotoxicity was confirmed by isogenic derivatives of the human colon carcinoma HCT116 cell lines (p21(+/+) and p21(-/-)), and immunoprecipitation studies with p21 antibody. The SAA cytotoxicity was blocked by co-incubation with catalase, whereas the SBA cytotoxicity and its subsequent growth arrest were abolished by N-acetyl-L-cysteine (NAC), but was not affected by PI3K phosphorylation inhibitor LY294002, or catalase, suggesting two separated oxidative stress pathways were mediated by these two ascorbates. In addition, neither active caspase 3 nor apoptotic bodies but autophagic vacuoles associated with increased LC3-II were found in SBA-treated HT-29 cells; implicating that SBA induced AKT phosphorylation-autophagy and p21-growth arrest in colon cancer HT-29 cells through an NAC-inhibitable oxidative stress pathway.

Topics: Antineoplastic Agents; Antioxidants; Ascorbic Acid; Autophagy; Benzylidene Compounds; Cell Cycle; Cell Cycle Proteins; Cell Line, Tumor; Colonic Neoplasms; Cyclin-Dependent Kinase Inhibitor p21; Humans; Oxidative Stress; Proto-Oncogene Proteins c-akt; Time Factors

Sodium 5,6-benzylidene ascorbate (SBA) is a conjugate of ascorbic acid (Asc) with benzyaldehyde. It has been found that the antioxidant activity of SBA is more stable and has a longer lifetime in living cells and organs than Asc. In this study, we investigated the effect of SBA on the induction of melanin in cultured melanoma (B-16) cells irradiated by UV-A. Melanin content of B-16 cells was significantly increased by UV-A irradiation. The induction was abolished by mannitol and particularly by superoxide dismutase, suggesting the involvement of O2- in the biosynthesis of melanin in cultured melanoma cells. This was theorized by the fact that the induction was also observed in B-16 cells treated with superoxide anion radicals chemically generated in the hypoxanthine/xanthine oxidase-reaction system, instead of UV-A irradiation. The induction of melanin caused by UV-A irradiation was suppressed by SBA in a dose-dependent manner. To elucidate the mechanism of this suppressive effect, the scavenging activity against O2-, and the inhibitory effect of SBA on tyrosinase activity were examined. ESR spectrometric analysis showed that SBA strongly scavenged O2-, and the presence of SBA in the medium remarkably inhibited the tyrosinase activity in cultured B-16 melanoma cells. It can be concluded that SBA effectively inhibits the melanin biosynthesis in B-16 melanoma cells induced by reactive oxygen species (ROS) generated by UV-A irradiation via tyrosinase.

Topics: Antioxidants; Ascorbic Acid; Benzylidene Compounds; Free Radical Scavengers; Melanins; Melanoma, Experimental; Reactive Oxygen Species; Tumor Cells, Cultured; Ultraviolet Rays

U1 cells, a subclone of U937 cells chronically infected with human immunodeficiency virus type 1 (HIV-1), produced HIV-1 only in the presence of inducers such as 12-O-tetradecanoxylphorbol 13-acetate (TPA) or tumor necrosis factor (TNF)-alpha. The expression of HIV-antigen on U1 cells induced by TPA or TNF-alpha was found to be prevented by sodium 5,6-benzylidene-L-ascorbate (SBA) in a concentration-dependent manner. Treatment of U1 cells with SBA in the presence of inducers resulted in cell death with cell shrinkage, chromatin condensation and DNA fragmentation into nucleosomal oligomers, characteristics of apoptosis. In contrast, SBA had scarcely any apoptotic effect on U1 cells in the absence of inducers. SBA did not also induce apoptosis in parental U937 cells in the presence or absence of inducers. These results suggest that HIV-replicating U1 cells selectively undergo apoptosis on treatment with SBA.

Topics: Antiviral Agents; Apoptosis; Ascorbic Acid; Benzylidene Compounds; HIV Antigens; HIV-1; Humans; Molecular Structure; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha; Virus Replication

Sodium 5,6-benzylideneascorbate (SBA), which is known to be an antitumor substance, was found to induce apoptotic cell death of L929 tumor cells directly in a concentration- and time-dependent manner. The dying cells exhibited cell shrinkage, disappearance of cell surface microvilli, chromatin condensation and DNA fragmentation into nucleosomal oligomers characteristic of apoptosis. These results indicate a possible mechanism by which SBA induces tumor regression in vivo.

Topics: Animals; Antineoplastic Agents; Apoptosis; Ascorbic Acid; Benzylidene Compounds; DNA Damage; DNA, Neoplasm; Electrophoresis, Agar Gel; Fibrosarcoma; Kinetics; Mice; Microscopy, Electron; Molecular Structure; Tumor Cells, Cultured

The deuterated benzaldehyde derivative zilascorb(2H), 5,6-O-benzylidene-d-L-ascorbic acid, was administered once daily by i.v. injection in nude mice with grafted tumours of a human malignant melanoma (E.E.) and ovarian carcinoma (OVCAR-3) origins. Like benzaldehyde, zilascorb(2H) has been shown to induce protein synthesis inhibition at otherwise non-toxic doses in cells grown in vitro, and acts reversibly in the sense that protein synthesis returns to normal shortly after removal of the drug. The present data indicate that daily injections with zilascorb(2H) induce a tumour volume growth inhibitory effect in both tumour xenografts studied. Furthermore, from histological examinations of each single tumour it was found that tumours of drug-treated animals, although smaller than those of placebo-treated (i.e. control) animals, had, on average, a higher necrotic fraction than control tumours. Thus, it is concluded that zilascorb(2H) induces tumour necrotisation and not just inhibition of the rate of tumour cell production. Continued measurement of tumour volume after ended treatment with zilascorb(2H) indicated that surviving tumour cells resumed their normal growth rate immediately. The reversibility of the effect induced by this compound, earlier observed in vitro only, is therefore here confirmed to be valid also in two different tumour xenografts in vivo. The present data accords well with the assumption that protein synthesis inhibition is the primary cellular effect of zilascorb(2H) in vivo. We therefore conclude that zilascorb(2H)-induced cancer cell lethality in tumour xenografts probably comes as a secondary consequence of prolonged protein synthesis inhibition.

Topics: Animals; Antineoplastic Agents; Ascorbic Acid; Benzylidene Compounds; Cell Division; Deuterium; Dose-Response Relationship, Drug; Female; Humans; Male; Melanoma; Mice; Mice, Inbred BALB C; Mice, Nude; Middle Aged; Necrosis; Neoplasm Proteins; Neoplasm Transplantation; Ovarian Neoplasms; Transplantation, Heterologous