A ubiquitin ligase, skeletrophin, is a negative regulator of melanoma invasion.
Skeletrophin (mindbomb homolog 2 (MIB2)) is a RING (Really Interesting New Gene) finger-dependent ubiquitin ligase, which targets the intracellular region of Notch ligands. A previous immunohistochemical study demonstrated that skeletrophin was downregulated in many melanomas. In the present study, we have identified a promoter region of skeletrophin on a CpG island and detected aberrant methylation of this region in six of 31 invasive melanomas, but in none of 25 benign nevi or five non-invasive superficial spreading melanomas. Subsequently, we found that a zinc-finger transcriptional factor Snail, which is overexpressed in many melanoma cells, repressed the skeletrophin promoter activity via an E-box-related element and was involved in downregulation of skeletrophin. An activator protein-2, which has a tumor suppressor-like role in melanoma, increased skeletrophin expression. Interestingly, exogenously expressed skeletrophin reduced melanoma cell invasion in vitro and in vivo. Colony formation in soft agar was also reduced in a RING motif-dependent manner, without affecting cell growth. We also found that skeletrophin downregulated transcription of the Met oncogene, which encodes the hepatocyte growth factor receptor and plays a role in the determination of the invasive phenotype of many malignant tumors. Finally, exogenously expressed skeletrophin, but not its RING mutant, increased transcription of Hes1 gene, a downstream effector of Notch pathway in melanoma cells. The present findings indicate that skeletrophin might be a novel suppressor factor for melanoma invasion.
Takeuchi
T
T
Department of Pathology, Kochi Medical School, Kochi, Japan. takeutit@med.kochi-ms.ac.jp
Adachi
Y
Y
Sonobe
H
H
Furihata
M
M
Ohtsuki
Y
Y
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D018899:CpG Islands; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D008545:Melanoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D008745:Methylation; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000473:pathology; D014411:Neoplastic Stem Cells; D011401:Promoter Regions, Genetic; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D000071250:Snail Family Transcription Factors; D050656:Transcription Factor AP-2 / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D018398:Homeodomain Proteins; D012333:RNA, Messenger; D000071250:Snail Family Transcription Factors; D050656:Transcription Factor AP-2; D014157:Transcription Factors; C478156:MIB2 protein, human; D044767:Ubiquitin-Protein Ligases; D019859:Proto-Oncogene Proteins c-met