title: KIT receptor activation by autocrine and paracrine stem cell factor stimulates growth of merkel cell carcinoma in vitro.
abstract: The co-expression of KIT receptor and its ligand stem cell factor (SCF) has been reported in biopsy specimens of Merkel cell carcinoma (MCC). However, the functional role of SCF/KIT in the pathogenesis of this aggressive tumor has not been elucidated. The present study reports expression and effects of SCF and KIT in the Merkel cell carcinoma cell line MCC-1 in vitro. SCF and KIT were endogenously co-expressed in MCC-1 cells. Exogenous soluble SCF modulated KIT receptor mRNA and protein expression, stimulated growth of MCC-1 cells, upregulated endogenous activation of KIT, AKT, and of extracellular signal-regulated kinase (ERK) 1/2 signaling pathway. On the contrary, an inhibitory antibody that neutralized the KIT ligand binding site, reduced growth of MCC-1 cells, as did high doses of the KIT kinase inhibitors imatinib and nilotinib. Also, inhibitors of KIT downstream effectors, U0126 that blocks MEK1/2 as well as wortmannin and LY294002 that inhibit phosphatidylinositol 3-kinase-dependent AKT phosphorylation, inhibited the proliferation of MCC-1 cells. These data support the hypothesis that KIT is activatable by paracrine or autocrine tumor cell-derived SCF and stimulates growth of Merkel cell carcinoma in vitro. Blockade of KIT and the downstream signaling cascade at various levels results in inhibition of Merkel cell carcinoma growth in vitro, suggesting targets for therapy of this cancer.
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Crete, Heraklion, Greece. krasagak@med.uoc.gr
authors.forename: Konstantin
authors.initials: K
authors.lastname: Krasagakis
authors.forename: Irene
authors.initials: I
authors.lastname: Fragiadaki
authors.forename: Maria
authors.initials: M
authors.lastname: Metaxari
authors.forename: Sabine
authors.initials: S
authors.lastname: Krüger-Krasagakis
authors.forename: George N
authors.initials: GN
authors.lastname: Tzanakakis
authors.forename: Efstathios N
authors.initials: EN
authors.lastname: Stathopoulos
authors.forename: Jürgen
authors.initials: J
authors.lastname: Eberle
authors.forename: Nektarios
authors.initials: N
authors.lastname: Tavernarakis
authors.forename: Androniki D
authors.initials: AD
authors.lastname: Tosca
mesh_terms: D057134:Antibodies, Neutralizing / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects; D001549:Benzamides; D015266:Carcinoma, Merkel Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000068877:Imatinib Mesylate; D019899:Paracrine Communication / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility / Q000187:drug effects; D019089:Stem Cell Factor / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D057134:Antibodies, Neutralizing; D001549:Benzamides; D048049:Extracellular Signal-Regulated MAP Kinases; D000068877:Imatinib Mesylate; D019869:Phosphatidylinositol 3-Kinases; D010879:Piperazines; D051057:Proto-Oncogene Proteins c-akt; D019009:Proto-Oncogene Proteins c-kit; D011743:Pyrimidines; D012333:RNA, Messenger; D019089:Stem Cell Factor; C498826:nilotinib