Defective expression of HRK is associated with promoter methylation in primary central nervous system lymphomas.
OBJECTIVE
Recently, it has been reported that expression of the HRK gene was significantly reduced by hypermethylation in astrocytic tumors. Our aim is to verify the alterations in the HRK gene in primary central nervous system lymphomas (PCNSLs).


METHODS
We analyzed the hypermethylation status and expression of the gene and 12q13.1 loss of heterozygosity in 31 PCNSLs.


RESULTS
A total of 13 PCNSLs (31%) demonstrated hypermethylation in either the promoter or exon 1; loss of HRK expression was immunohistochemically observed in 9 tumors and was significantly associated with promoter methylation. In addition, higher apoptotic counts were associated with HRK positivity. PCNSLs with HRK methylation also showed methylation of multiple genes, such as p14ARF, p16INK4a, RB1, p27Kip1 and O6-MGMT. Patients with tumors demonstrating concurrent methylation of more than half of their genes demonstrated significantly poorer survival and earlier recurrence. Hypermethylation of the HRK promoter alone was not associated with overall outcome, but relapse-free survival was significantly shorter.


CONCLUSIONS
Our findings suggest that transcriptional repression of HRK is caused by promoter hypermethylation in PCNSL, and that the loss of HRK associated with the methylation profile of other genes is a potential step in the modulation of cellular death by apoptosis during PCNSL tumorigenesis.
Nakamura
Mitsutoshi
M
Department of Pathology , Nara Medical University School of Medicine, Nara, Japan.
Ishida
Eiwa
E
Shimada
Keiji
K
Nakase
Hiroyuki
H
Sakaki
Toshisuke
T
Konishi
Noboru
N
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D016543:Central Nervous System Neoplasms / Q000235:genetics* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019175:DNA Methylation; D018572:Disease-Free Survival; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D019656:Loss of Heterozygosity; D008223:Lymphoma / Q000235:genetics* / Q000473:pathology; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics; D011401:Promoter Regions, Genetic; D016160:Retinoblastoma Protein / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016019:Survival Analysis; D014158:Transcription, Genetic; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics
D051017:Apoptosis Regulatory Proteins; C436291:CDKN1B protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; C484586:HRK protein, human; D047908:Intracellular Signaling Peptides and Proteins; D016160:Retinoblastoma Protein; D025803:Tumor Suppressor Protein p14ARF; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019853:O(6)-Methylguanine-DNA Methyltransferase