Carcinogenesis Advance Access originally published online on April 21, 2007
Carcinogenesis 2007 28(10):2172-2183; doi:10.1093/carcin/bgm096
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Identification of distinct changes in gene expression after modulation of melanoma tumor antigen p97 (melanotransferrin) in multiple models in vitro and in vivo
Iron Metabolism and Chelation Program, Department of Pathology, Blackburn Building D06, University of Sydney, Sydney, New South Wales, 2006 Australia
* To whom correspondence should be addressed. Tel: +61 2 9036 6548; Fax: +61 2 9036 6549; Email: d.richardson{at}pathology.usyd.edu.au
Melanoma tumor antigen p97 or melanotransferrin (MTf) is an iron (Fe)-binding protein with high homology to serum transferrin. MTf is expressed at very low levels in normal tissues and in high amounts in melanoma cells although its function remains elusive. To understand the function of MTf, we utilized whole-genome microarray analysis to examine the gene expression profile of five models after modulating MTf expression. These models included two new stably transfected MTf hyper-expression models (SK-N-MC neuroepithelioma and LMTK– fibroblasts) and one cell type (SK-Mel-28 melanoma) where MTf was down-regulated by post-transcriptional gene silencing. These findings were compared with alterations in gene expression identified using the MTf–/– mice. In addition, the changes identified from the microarray data were also assessed in a new model of MTf down-regulation in SK-Mel-2 melanoma cells. In the cell line models, MTf hyper-expression led to increased proliferation, whereas MTf down-regulation resulted in decreased proliferation. Across all five models of MTf down- and up-regulation, we identified three genes modulated by MTf. These included ATP-binding cassette subfamily B member 5, whose change in expression mirrored MTf down- or up-regulation. In addition, thiamine triphosphatase and transcription factor 4 were inversely expressed relative to MTf levels across all five models. The products of these three genes are involved in membrane transport, thiamine phosphorylation and proliferation/survival, respectively. This study identifies novel molecular targets directly or indirectly regulated by MTf and the potential pathways involved in its function, including modulation of proliferation.
Abbreviations: Abcb5, ATP-binding cassette subfamily B member 5; Apod, apolipoprotein D; Mef2a, myocyte enhancer factor 2a; MTf, melanotransferrin; PTGS, post-transcriptional gene silencing; RT-PCR, reverse transcription–polymerase chain reaction; Tcf4, transcription factor 4; Tf, transferrin; TfR1, transferrin receptor 1; Thtpa, thiamine triphosphatase
Received January 23, 2007; revised March 17, 2007; accepted April 11, 2007.