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Germline and somatic DNA methylation and epigenetic regulation of KILLIN in renal cell carcinoma
Author(s) -
Bennett Kristi L.,
Campbell Rebecca,
Ganapathi Shireen,
Zhou Ming,
Rini Brian,
Ganapathi Ram,
Neumann Hartmut P.H.,
Eng Charis
Publication year - 2011
Publication title -
genes, chromosomes and cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.754
H-Index - 119
eISSN - 1098-2264
pISSN - 1045-2257
DOI - 10.1002/gcc.20887
Subject(s) - dna methylation , methylation , germline , epigenetics , pten , cpg site , cancer research , biology , germline mutation , somatic cell , demethylating agent , bisulfite sequencing , microbiology and biotechnology , genetics , mutation , gene , gene expression , pi3k/akt/mtor pathway , signal transduction
We recently identified germline methylation of KILLIN , a novel p53‐regulated tumor suppressor proximal to PTEN , in >1/3 Cowden or Cowden syndrome‐like (CS/CSL) individuals who are PTEN mutation negative. Individuals with germline KILLIN methylation had increased risks of renal cell carcinoma (RCC) over those with PTEN mutations. Therefore, we tested the hypothesis that KILLIN may be a RCC susceptibility gene, silenced by germline methylation. We found germline hypermethylation by combined bisulfite restriction analysis in at least one of the four CpG‐rich regions in 23/41 (56%) RCC patients compared to 0/50 controls ( P < 0.0001). Of the 23, 11 (48%) demonstrated methylation in the −598 to −890 bp region in respect to the KILLIN transcription start site. Furthermore, 19 of 20 advanced RCC showed somatic hypermethylation upstream of KILLIN , with the majority hypermethylated at more than one CpG island (13/19 vs. 3/23 with germline methylation, P < 0.0001). qRT‐PCR revealed that methylation significantly downregulates KILLIN expression ( P = 0.05), and demethylation treatment by 5‐aza‐2′deoxycytidine significantly increased KILLIN expression in all RCC cell lines while only increasing PTEN expression in one line. Furthermore, targeted in vitro methylation revealed a significant decrease in KILLIN promoter activity only. These data reveal differential epigenetic regulation by DNA promoter methylation of this bidirectional promoter. In summary, we have identified KILLIN as a potential novel cancer predisposition gene for nonsyndromic clear‐cell RCC, and the epigenetic mechanism of KILLIN inactivation in both the germline and somatic setting suggests the potential for treatment with demethylating agents. © 2011 Wiley‐Liss, Inc.