Wnt antagonist DKK1 acts as a tumor suppressor gene that induces apoptosis and inhibits proliferation in human renal cell carcinoma.
The functional significance of Wnt antagonist DKK1 has not been investigated in renal cell carcinoma (RCC). Therefore, we hypothesized that DKK1 may be a tumor suppressor gene and is epigenetically silenced, thus decreased DKK1 may cause progression of RCC. To assess the function of DKK1, we established stable DKK1 transfected cells and monitored them regarding cell viability, colony formation, apoptosis, cell cycle, and invasive capability. RCC cell lines had decreased levels of DKK1, which were increased after treatment with 5-Aza-2'-deoxycytidine and trichostatin A. In chromatin immunoprecipitation assay, the level of dimethyl H3K9 and trimethyl H3K27 was decreased after 5-Aza-2'-deoxycytidine/trichostatin A treatment in RCC cell lines. Increased methylation was also associated with higher pathological stages in primary RCC tissues. T-cell factor/lymphoid enhancer factor activity and nuclear beta-catenin expression were not changed in DKK1 transfectants. Also the expression of cyclinD1 and c-Myc was not changed in DKK1 transfectants. These results suggest that DKK1 may not be involved in the beta-catenin dependent pathway. We also evaluated the expression of various related genes. Cleaved caspase3, p53, p21 and puma expression were significantly upregulated in the DKK1 transfected cells. The population of apoptotic cells was increased in stable DKK1 cells and tumor growth suppression was also observed in nude mice with DKK1 transfected cells. In conclusion, this is the first report to show that DKK1 expression is epigenetically silenced in kidney cancer and its reexpression induces apoptosis and cell cycle arrest in RCC.
Hirata
Hiroshi
H
Department of Urology, San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
Hinoda
Yuji
Y
Nakajima
Koichi
K
Kawamoto
Ken
K
Kikuno
Nobuyuki
N
Ueno
Koji
K
Yamamura
Soichiro
S
Zaman
Mohd S
MS
Khatri
Gaurav
G
Chen
Yi
Y
Saini
Sharanjot
S
Majid
Shahana
S
Deng
Guoren
G
Ishii
Nobuhisa
N
Dahiya
Rajvir
R
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D000077209:Decitabine; D044127:Epigenesis, Genetic; D005260:Female; D016147:Genes, Tumor Suppressor; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D007680:Kidney Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051153:Wnt Proteins / Q000037:antagonists & inhibitors*
D000964:Antimetabolites, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C501126:DKK1 protein, human; D006877:Hydroxamic Acids; D036341:Intercellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051153:Wnt Proteins; C012589:trichostatin A; D000077209:Decitabine; D053148:Caspase 3; D001374:Azacitidine