Carcinogenesis Advance Access published online on September 3, 2007
Carcinogenesis, doi:10.1093/carcin/bgm197
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Identification and functional characterization of ASK/Dbf4, a novel cell survival gene in cutaneous melanoma with prognostic relevance
1 Department of Dermatology Heinrich-Heine-University Duesseldorf, Germany
2 Institute of Pathology, Ruhr-University, Bochum, Germany
3 Institute of Functional Genomics for Microorganisms, Heinrich-Heine-University Duesseldorf, Germany
Corresponding author: Prof. Dr. Ulrich R. Hengge, Department of Dermatology, Heinrich-Heine-University, Moorenstrasse 5, D-40225 Duesseldorf, Germany. Phone: 49-211-811-8066; Fax: 49-211-811-8830; E-mail: ulrich.hengge{at}uni-duesseldorf.de
Malignant melanoma is one of the most aggressive and invasive metastatic tumors derived from melanocytes that have undergone malignant transformation by acquisition of genetic and epigenetic alterations. Oligonucleotide microarray-based screening of distinct stages in the tumor progression model of cutaneous melanoma identified ASK/Dbf4, as a novel determinant for melanoma development. qReal-time-PCR based confirmation of ASK/Dbf4 on a series of benign nevi, dysplastic nevi, primary cutaneous melanomas, and cutaneous melanoma metastases and a number of other controls using normal human melanocytes (NHM) as calibrator not only revealed a melanoma-specific overexpression but also revealed that higher ASK/Dbf4 expressing melanomas were associated with lower relapse-free survival. Additionally, we also confirmed the observed overexpression of ASK/Dbf4 in melanoma using Western blot analysis and immunohistochemistry. As ASK/Dbf4 is known to be a cyclin-like regulatory subunit of mammalian Cdc7 from studies in yeast, the present study investigated its role in melanoma cells. In keeping with its expected role, our data suggest that upregulated ASK/Dbf4 is localized in the nucleus and binds to human Cdc7 to form Cdc7-ASK/Dbf4 complexes in several analyzed melanoma cell lines. Further, we demonstrate that siRNA-mediated depletion of ASK/Dbf4 retarded melanoma cell survival and proliferation. In summary, we report the differential regulation of a novel gene, namely ASK/Dbf4, in melanoma and suggest that upregulation of ASK/Dbf4 is a novel molecular determinant with prognostic relevance that confers a proliferative advantage in cutaneous melanoma.
Key Words: ASK/Dbf4 • gene expression • cutaneous melanoma • oligonucleotide microarray • Cdc7 • prognosis
Received July 17, 2007; revised August 21, 2007; accepted August 21, 2007.