title: Tocilizumab unmasks a stage-dependent interleukin-6 component in statin-induced apoptosis of metastatic melanoma cells.
abstract: The interleukin (IL)-6 inhibits the growth of early-stage melanoma cells, but not metastatic cells. Metastatic melanoma cells are susceptible to statin-induced apoptosis, but this is not clear for early-stage melanoma cells. This study aimed to investigate the IL-6 susceptibility of melanoma cells from different stages in the presence of simvastatin to overcome loss of growth arrest. ELISA was used to detect secreted IL-6 in human melanoma cells. The effects of IL-6 were measured by western blots for STAT3 and Bcl-2 family proteins. Apoptosis and proliferation were measured by caspase 3 activity, Annexin V staining, cell cycle analysis, and a wound-healing assay. Human metastatic melanoma cells A375 and 518A2 secrete high amounts of IL-6, in contrast to early-stage WM35 cells. Canonical IL-6 signaling is intact in these cells, documented by transient phosphorylation of STAT3. Although WM35 cells are highly resistant to simvastatin-induced apoptosis, coadministration with IL-6 enhanced the susceptibility to undergo apoptosis. This proapoptotic effect of IL-6 might be explained by a downregulation of Bcl-XL, observed only in WM35 cells. Furthermore, the IL-6 receptor blocking antibody tocilizumab was coadministered and unmasked an IL-6-sensitive proportion in the simvastatin-induced caspase 3 activity of metastatic melanoma cells. These results confirm that simvastatin facilitates apoptosis in combination with IL-6. Although endogenous IL-6 secretion is sufficient in metastatic melanoma cells, exogenously added IL-6 is needed for WM35 cells. This effect may explain the failure of simvastatin to reduce melanoma incidence in clinical trials and meta-analyses.
authors.affiliation: aDepartment of Oncology, Medicine I bCenter for Physiology and Pharmacology, Comprehensive Cancer Center, Institute of Pharmacology cDepartment of Neurology, Medical University of Vienna, Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Minichsdorfer
authors.forename: Christine
authors.initials: C
authors.lastname: Wasinger
authors.forename: Evelyn
authors.initials: E
authors.lastname: Sieczkowski
authors.forename: Bihter
authors.initials: B
authors.lastname: Atil
authors.forename: Martin
authors.initials: M
authors.lastname: Hohenegger
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001665:Binding Sites / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism*; D008545:Melanoma / Q000188:drug therapy / Q000473:pathology*; D009362:Neoplasm Metastasis / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D019821:Simvastatin / Q000494:pharmacology*; D012878:Skin Neoplasms / Q000188:drug therapy / Q000473:pathology; D014945:Wound Healing / Q000187:drug effects; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; C508600:IL6 protein, human; D015850:Interleukin-6; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D051020:bcl-X Protein; D019821:Simvastatin; D053148:Caspase 3; C502936:tocilizumab