title: Tumour-mediated disruption of dendritic cell function: inhibiting the MEK1/2-p44/42 axis restores IL-12 production and Th1-generation.
abstract: Dysfunctional dendritic cells (DC) are common in cancer patients; however, the underlying molecular targets are poorly understood. Nevertheless, adoptive-transfer and in situ vaccination protocols continue, largely without addressing immune-suppression. Understanding tumour-mediated DC suppression would assist rational design of next generation immunotherapy. This study used a tumour-lysate loaded DC model of adoptive immunotherapy and also necrotic cells common in many tumours. Patient-derived and healthy-donor monocyte-derived DC were examined for disruptions in mitogen-activated protein kinase (MAPK) signalling pathways associated with their capacity to generate Type-1 helper-T cell populations (Th1). Melanoma-lysate markedly suppressed TLR4-dependent IL-12p40 and p70 production. Suppression of IL-12p70 occurred independently of maturation markers (e.g., CD40, CD80, CD83) and correlated with depressed p35 and p40 transcription. Decreased IL-12 secretion was not associated with IL-10, TGFbeta, VEGF, PGE(2) or ganglioside in tumour lysates or attributable to endogenous PGE(2) release from DC. In contrast to HUVEC lysate, melanoma-lysate-treated DC were less able to generate Th1-responses from naïve T-cells. The p44/42 MAPK was hyper-activated by melanoma lysate, but not that of HUVEC. Blockade of MEK1/2, the upstream kinase for p44/42, with U0126 prevented p44/42 activation, restored IL-12p70, and permitted effective generation of Th1-responses. Therefore the p44/42 MAPK is a target for tumour-mediated immune suppression of DC resulting in transcriptional down-regulation of IL-12 p35 and p40 genes, reduced IL-12 secretion and suppressed Th1-responses. Pharmacological intervention in the MEK-p44/42 axis may be applicable to render DC resistant to the suppressive effects of tumour lysates and may form part of a combination immunotherapy.
authors.affiliation: Academic Unit of Clinical Oncology, University of Nottingham, City Hospital, Nottingham, United Kingdom. andrew.jackson@nottingham.ac.uk
authors.forename: Andrew Mark
authors.initials: AM
authors.lastname: Jackson
authors.forename: Lori Ann
authors.initials: LA
authors.lastname: Mulcahy
authors.forename: Xing Wu
authors.initials: XW
authors.lastname: Zhu
authors.forename: Dearbhaile
authors.initials: D
authors.lastname: O'Donnell
authors.forename: Poulam M
authors.initials: PM
authors.lastname: Patel
mesh_terms: D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D003713:Dendritic Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D016219:Immunotherapy, Adoptive; D018664:Interleukin-12 / Q000096:biosynthesis*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008545:Melanoma / Q000201:enzymology / Q000276:immunology / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009336:Necrosis; D009570:Nitriles / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology; D014158:Transcription, Genetic
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; C113580:U 0126; D018664:Interleukin-12; C482128:MAP2K2 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human