Promoter hypermethylation: a common cause of reduced p16(INK4a) expression in uveal melanoma.
Tumors often display unrestricted cell cycling attributable to a dysfunctional G(1)-S checkpoint. One of the mechanisms leading to such a defect is the inactivation of the cyclin-dependent kinase inhibitor p16(INK4a). Although inactivation of p16(INK4a) is observed in a wide range of tumors, including cutaneous melanoma, genetic alteration of p16(INK4a) is reportedly uncommon in uveal melanoma. Here we show that the p16(INK4a) promoter is hypermethylated in 6 of 12 uveal melanoma cell lines and in 7 of 22 primary uveal melanomas analyzed. Five of seven patients with a methylated primary tumor died of metastatic disease compared with 2 of 15 patients with a nonmethylated primary tumor. We also show that all uveal melanoma cell lines with a hypermethylated p16(INK4a) promoter have lost p16(INK4a) expression but have maintained the expression of p14(ARF). Treatment of uveal melanoma cell lines with 5-aza-2'-deoxycytidine results in demethylation of p16(INK4a) and in reexpression of p16(INK4a) mRNA, which is maintained upon withdrawal of the 5-aza-2'-deoxycytidine. In conclusion, p16(INK4a) promoter methylation appears to be a common event in uveal melanoma and is accompanied by the loss of p16(INK4a) expression.
van der Velden
P A
PA
Section Human Genetics, Center for Human and Clinical Genetics, Leiden University Medical Center, 2333 AL Leiden, the Netherlands.
Metzelaar-Blok
J A
JA
Bergman
W
W
Monique
H
H
Hurks
H
H
Frants
R R
RR
Gruis
N A
NA
Jager
M J
MJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018899:CpG Islands / Q000502:physiology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis / Q000235:genetics*; D019175:DNA Methylation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D000077209:Decitabine; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014604:Uveal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology
D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D012333:RNA, Messenger; D000077209:Decitabine; D001374:Azacitidine