9940

DLEC1

CFAP81|DLC1|F56;deleted in lung and esophageal cancer 1;DLEC1;deleted in lung and esophageal cancer 1

DLC-1|cilia and flagella associated protein 81|deleted in lung and esophageal cancer 1 transcript varient 2|deleted in lung and esophageal cancer protein 1

3p21.3

protein-coding

The short arm of chromosome 3 is thought to contain multiple tumor suppressor genes, because one copy of this chromosomal arm frequently is missing in carcinomas that have arisen in a variety of tissues. We have isolated a novel gene encoding a 1755-amino acid polypeptide, through large-scale sequencing of genomic DNA at 3p21.3. mutational analysis of this gene by reverse transcription-PCR revealed the lack of functional transcripts and an increase of nonfunctional RNA transcripts in a significant proportion (33%) of cancer cell lines and primary cancers (4 of 14 esophageal cancer cell lines, 2 of 2 renal cancer cell lines, 11 of 30 primary non-small cell lung cancers, and 3 of 10 primary squamous cell carcinomas of the esophagus). However, no alterations of the gene itself were detected in any of the cancers examined. Introduction of the cDNA significantly suppressed the growth of four different cancer cell lines, two of which produced no normal transcript on their own. No such effect occurred when antisense cDNA, cDNA corresponding to an aberrant transcript, or the vector DNA alone were transfected. These data suggest that aberrant transcription of this gene, designated DLC1 (deleted in lung cancer 1), may be involved in carcinogenesis of the lung, esophagus, and kidney.

suppression of ovarian tumor growth by chromosome 3p was demonstrated in a previous study. Deleted in Lung and Esophageal cancer 1 (DLEC1) on 3p22.3 is a candidate tumor suppressor in lung, esophageal, and renal cancers. The potential involvement of DLEC1 in epithelial ovarian cancer remains unknown. In the present study, DLEC1 downregulation was found in ovarian cancer cell lines and primary ovarian tumors. Focus-expressed DLEC1 in two ovarian cancer cell lines resulted in 41% to 52% inhibition of colony formation. No chromosomal loss of chromosome 3p22.3 in any ovarian cancer cell line or tissue was found. Promoter hypermethylation of DLEC1 was detected in ovarian cancer cell lines with reduced DLEC1 transcripts, whereas methylation was not detected in normal ovarian epithelium and DLEC1-expressing ovarian cancer cell lines. Treatment with demethylating agent enhanced DLEC1 expression in 90% (9 of 10) of ovarian cancer cell lines. DLEC1 promoter methylation was examined in 13 high-grade ovarian tumor tissues with DLEC1 downregulation, in which 54% of the tumors showed DLEC1 methylation. In addition, 80% of ovarian cancer cell lines significantly upregulated DLEC1 transcripts after histone deacetylase inhibitor treatment. Therefore, our results suggested that DLEC1 suppressed the growth of ovarian cancer cells and that its downregulation was closely associated with promoter hypermethylation and histone hypoacetylation.

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 DLEC1 is a candidate tumor suppressor gene that plays an important role in the development and progression of hepatocellular carcinoma.

PURPOSE: 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. MATERIALS AND 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.