title: Interactions of vitamin D analogue CB1093, TNFalpha and ceramide on breast cancer cell apoptosis.
abstract: Mechanisms by which vitamin D analogues promote apoptosis in tumour cells are unclear. In this study we have examined possible interactions between the synthetic vitamin D analogue CB1093 and two other known mediators of apoptosis, TNFalpha and ceramide, in MCF-7, T47D and Hs578T breast cancer cells. These studies indicated that cytosolic phospholipase A(2) (cPLA(2)) is involved in CB1093 as well as TNFalpha-mediated cell death. CB1093 promoted both TNFalpha and ceramide-induced c-PLA(2) activation, which was inversely related to loss of cell viability in MCF-7 and Hs578T cells. TNFalpha alone (5-20 ng/ml) failed to induce cytotoxicity and activation of cPLA(2) in T47D cells. However, pretreatment of these cells with CB1093 potentiated C(2)-ceramide-induced cPLA(2) activation and cell death. Treatment with CB1093 alone induced loss of cell viability and DNA fragmentation in all three cell lines by 5 days and these effects were accompanied by activation of cPLA(2). Furthermore, co-treatment with the cPLA(2) inhibitor AACOCF(3) led to partial protection against loss of cell viability induced by CB1093 in Hs578T and T47D cells as well as MCF-7 cells. The broad-spectrum caspase inhibitor z-VAD-fmk prevented TNFalpha but not C(2)-ceramide and CB1093-mediated release of arachidonic acid and cell death in MCF-7 cells. These results indicate that CB1093 potentiates responsiveness of breast cancer cells to TNFalpha and suggest that ceramide and/or cPLA(2) might be involved as downstream effectors in vitamin D-mediated caspase-independent cell death.
authors.affiliation: Department of Oncology, Gastroenterology, Endocrinology and Metabolism, St George's Hospital Medical School, Cranmer Terrace, Tooting, SW17 ORE, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Pirianov
authors.forename: K W
authors.initials: KW
authors.lastname: Colston
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000473:pathology*; D002117:Calcitriol / Q000031:analogs & derivatives / Q000494:pharmacology*; D002518:Ceramides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D010741:Phospholipases A / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; C103436:CB 1093; D002518:Ceramides; D014409:Tumor Necrosis Factor-alpha; D010741:Phospholipases A; D002117:Calcitriol