The tumor suppressor gene DLEC1 is frequently silenced by DNA methylation in hepatocellular carcinoma and induces G1 arrest in cell cycle

Background/Aims: The chromosome locus 3p21.3 is a "hot-spot" for chromosomal aberrations and loss of heterozygosity in cancers. The 35 genes mapped to the AP20 subregion of this locus were screened for their expression to identify candidate tumor suppressor genes. DLEC1 was selected for further characterization in primary hepatocellular carcinomas and cell lines.

Methods:RT-PCR and methylation-specific PCR were performed to examine the expression and methylation. Stable clones with DLEC1 overexpression were established to analyze cell proliferation and cell cycle.

Results:DLEC1 was silenced and hypermethylated in 9 of 11 cell lines examined. Treatment with 5-aza-2'-deoxycytidine reversed the methylation and restored DLEC1 expression. The correlation between hypermethylation and expression was also demonstrated in 10 pairs of hepatocellular carcinoma and adjacent normal tissues (t-test, p < 0.05). Hypermethylation of DLEC1 was detected in 70.6% of tumors, compared to 10.3% in normal tissues (n = 68, p < 0.001, chi(2)). Of interest, DLEC1 methylation was associated with the AJCC staging of the tumors (p = 0.036, chi(2)). DLEC1 over-expression in cell lines decreased colony formation, cell growth and cell size, and induced a G1 arrest in cell cycle.

Conclusions: Our data indicate that DLECI is a candidate tumor suppressor gene that plays an important role in the development and progression of hepatocellular carcinoma. (C) 2008 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.