The antitumour agent 5,6-dimethylxanthenone-4-acetic acid acts in vitro on human mononuclear cells as a co-stimulator with other inducers of tumour necrosis factor

• Published in: European journal of cancer (1990) 2001-10, Vol.37 (15), p.1930-1937
• Main Authors: Philpott, M., Ching, L.-M., Baguley, B.C.
• Format: Article
• Language: English
• Subjects: Antineoplastic agents; Antineoplastic Agents - pharmacology; Biological and medical sciences; CD14; Cell Culture Techniques; Chemotherapy; Cytokines - immunology; Dose-Response Relationship, Drug; Drug Synergism; Enzyme Inhibitors - pharmacology; Enzyme-Linked Immunosorbent Assay; Humans; Interleukin-1; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - immunology; Lipopolysaccharide; Lipopolysaccharide Receptors - immunology; Lipopolysaccharides - pharmacology; Medical sciences; NF-kappa B - metabolism; NF-kappaB; Okadaic acid; Okadaic Acid - pharmacology; Pharmacology. Drug treatments; Phorbol ester; Salicylic Acid - pharmacology; Tetradecanoylphorbol Acetate - pharmacology; Tumor Necrosis Factor-alpha - biosynthesis; Xanthenes - pharmacology; Xanthones
• ISSN: 0959-8049; 1879-0852
• DOI: 10.1016/S0959-8049(01)00210-6

5,6-Dimethylxanthenone-4-acetic acid (DMXAA), currently in phase I trials, demonstrates excellent activity against transplantable murine tumours with established vasculature. The induction of cytokines, particularly of tumour necrosis factor (TNF), appears to be critical to its action. We investigated TNF induction by DMXAA in cultured human peripheral blood leucocytes (HPBL). TNF was measured by an enzyme-linked immunosorbent assay after 8 h, and NF-κB induction by electrophoretic mobility shift assays (EMSA) after 2 h. DMXAA (800 μg/ml) had no effect alone on TNF production but augmented, by up to 4-fold, the ability of bacterial lipopolysaccharide (LPS) to induce TNF. Previously reported results showing TNF production by DMXAA alone were traced to the presence in an earlier batch of DMXAA of a small amount of LPS, the action of which could be blocked by polymyxin B. DMXAA stimulated TNF production by deacylated LPS, which alone had little effect. An antibody (MEM-18) to the CD14 receptor, while blocking the induction of TNF by LPS, enabled DMXAA to both synthesise TNF and induce NF-κB. The structurally related drug, flavone acetic acid (FAA), did not induce TNF or synergise with anti-CD14 antibody. DMXAA strongly augmented the ability of suboptimal concentrations of interleukin-1 (IL-1) (25 ng/ml), okadaic acid (OA) (20 ng/ml) and phorbol-12-myristate-13-acetate (PMA) (5 ng/ml) to induce TNF production, suggesting that it affects multiple pathways converging on NF-κB activation. Sodium salicylate, a drug reported to inhibit the β-subunit of IκB kinase (IKK), appeared to competitively inhibit TNF production by DMXAA in the presence of anti-CD14 antibody. Taken together, the results indicate DMXAA acts in vitro on HPBL to co-stimulate TNF production by a wide variety of agents, and suggests that IKK is the target that mediates this action.