Aberrant promoter methylation of DLEC1, a critical 3p22 tumor suppressor for renal cell carcinoma, is associated with more advanced tumor stage.
OBJECTIVE
Identifying tumor suppressor genes silenced by promoter CpG methylation uncovers mechanisms of tumorigenesis and identifies new epigenetic biomarkers for early cancer detection. DLEC1 is located at 3p22.3, a critical tumor suppressor gene locus for renal cell carcinoma. We explored its epigenetic alteration in renal cell carcinoma and possible clinicopathological association.


METHODS
We examined DLEC1 expression and methylation by semiquantitative reverse transcriptase and methylation specific polymerase chain reaction in 9 renal cell carcinoma cell lines and 81 primary tumors. We also analyzed the relationship between DLEC1 methylation and clinicopathological features in patients with renal cell carcinoma. We assessed DLEC1 inhibition of renal cell carcinoma cell growth by colony formation assay.


RESULTS
DLEC1 methylation and down-regulation were detected in all renal cell carcinoma cell lines. Treatment with 5-aza-2'-deoxycytidine (Sigma) and/or trichostatin A (Cayman Chemical, Ann Arbor, Michigan) reversed methylation and restored DLEC1 expression, indicating that methylation directly mediates its silencing. Aberrant methylation was further detected in 25 of 81 primary tumors (31%) but only 1 of 53 nonmalignant renal tissues (2%) showed methylation. DLEC1 methylation status was significantly associated with TNM classification and grade in patients with renal cell carcinoma (chi-square test p = 0.01 and 0.04, respectively). DLEC1 ectopic expression in silenced renal cell carcinoma cells resulted in substantial tumor cell clonogenicity inhibition.


CONCLUSIONS
To our knowledge we report for the first time that DLEC1 is often down-regulated by CpG methylation and shows tumor inhibitory function in renal cell carcinoma cells, indicating its role as a tumor suppressor. DLEC1 tumor specific methylation may serve as a biomarker for early detection and prognosis prediction of this tumor.
Zhang
Qian
Q
Department of Urology, Peking University First Hospital and Institute of Urology, Peking University, Beijing, China.
Ying
Jianming
J
Li
Jisheng
J
Fan
Yichao
Y
Poon
Fan Fong
FF
Ng
Ka Man
KM
Tao
Qian
Q
Jin
Jie
J
D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008745:Methylation; D008875:Middle Aged; D009367:Neoplasm Staging; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D055815:Young Adult
C119064:DLEC1 protein, human; D025521:Tumor Suppressor Proteins