title: Interferon gamma induction in human melanoma cell/allogeneic leukocyte co-cultures is enhanced by interleukin 18 but drug resistant melanoma cells are poorer inducers of IFN-gamma.
abstract: Human melanoma Colo 679 cells were made resistant to doxorubicin (adriamycin, ADM) by continuous exposure to ascending concentrations of the drug and Colo/ADM80; a variant which grew continuously in the presence of 80 ng/ml of ADM was thus established. Human peripheral blood mononuclear cells (PBMC) produced interferon gamma (IFN-gamma) when cultured with mitomycin C (MMC)-treated parental Colo 679 cells. The synthesis of IFN-gamma was synergistically enhanced by adding interleukin-18 (IL-18) and this was IL-12-dependent because a neutralizing antibody against IL-12 almost completely inhibited IFN-gamma production while control antibodies (Abs) were inactive. The cellular sources of IFN-gamma were found to be B cells, CD8+ T cells and CD4+ T cells as revealed by flow cytometry after double staining for surface antigens and staining for intracellular IFN-gamma. Interestingly, the resistant cell line induced much less IFN-gamma production than the parental cell line under the same co-culture conditions; however, IL-18 could still enhance the production of IFN-gamma. In conclusion, our study shows that acquired resistance to anti-cancer agents can also reduce immune responses to cancer cells. However, the immunostimulatory cytokine IL-18 could still enhance IFN-gamma production in drug resistant tumor cell-PBMC cultures indicating that such immunostimulatory agents could still be beneficial in immunotherapy for patients with recurrent drug resistant tumors.
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Faculty of Medicine and Surgery, University of Malta, Msida. fujisaki@hayashibara.co.jp
authors.forename: M J
authors.initials: MJ
authors.lastname: Micallef
authors.forename: S
authors.initials: S
authors.lastname: Darmanin
authors.forename: J A
authors.initials: JA
authors.lastname: Buhagiar
authors.forename: M T
authors.initials: MT
authors.lastname: Camilleri-Podesta
authors.forename: H
authors.initials: H
authors.lastname: Yamauchi
authors.forename: M
authors.initials: M
authors.lastname: Kurimoto
authors.forename: A S
authors.initials: AS
authors.lastname: Inglott
authors.forename: R
authors.initials: R
authors.lastname: Ellul-Micallef
mesh_terms: D018920:Coculture Techniques; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000502:physiology; D020382:Interleukin-18 / Q000494:pharmacology*; D007962:Leukocytes / Q000378:metabolism*; D008545:Melanoma / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D020382:Interleukin-18; D018664:Interleukin-12; D004317:Doxorubicin; D007371:Interferon-gamma