Aberrant promoter methylation and tumor suppressive activity of the DFNA5 gene in colorectal carcinoma

Abstract

To identify novel methylated gene promoters, we compared differential RNA expression profiles of colorectal cancer (CRC) cell lines with or without treatment of 5-aza-2 0 -deoxycytidine (5-aza-dC). Out of 1776 genes that were initially 'absent (that is, silenced)' by gene expression array analysis, we selected 163 genes that were increased after 5-aza-dC treatment in at least two of three CRC cell lines. The microarray results were confirmed by Reverse Transcription-PCR, and CpG island of the gene promoters were amplified and sequenced for examination of cancer-specific methylation. Among the genes identified, the deafness, autosomal dominant 5 gene, DFNA5, promoter was found to be methylated in primary tumor tissues with high frequency (65%, 65/100). Quantitative methylation-specific PCR of DFNA5 clearly discriminated primary CRC tissues from normal colon tissues (3%, 3/100). The mRNA expression of DFNA5 in four of five colon cancer tissues was significantly downregulated as compared to normal tissues. Moreover, forced expression of full-length DFNA5 in CRC cell lines markedly decreased the cell growth and colony-forming ability whereas knockdown of DFNA5 increased cell growth in culture. Our data implicate DFNA5 as a novel tumor suppressor gene in CRC and a valuable molecular marker for human cancer.

The DFNA5 gene, responsible for hearing loss and involved in cancer, encodes a novel apoptosis-inducing protein

“…Methylation of the 5¢-flanking region of DFNA5, as frequently observed in gastric, colorectal and breast carcinoma, [13][14][15][16] may be a way to prevent the apoptotic actions of DFNA5. We believe that our description of the apoptosis-inducing mechanism of DFNA5 contributes to the growing evidence that DFNA5 may be a tumor suppressor gene.…”

“…We previously assumed that transfection of mutant DFNA5 causes necrotic cell death. 7 As increasing evidence of tumor suppressor gene characteristics of DFNA5 has been provided, 11,12,14 we re-evaluated the nature of mutant DFNA5-induced cell death. In this report, we used annexin V as well as TUNEL staining.…”

“…However, since its identification, the small number of papers published on DFNA5 almost all point to a possible involvement in cancer biology. [10][11][12][13][14][15][16] Especially during the last 3 years, DFNA5 emerged from several genomic screens identifying new tumor suppressor genes. Further analysis showed that the DFNA5 gene is epigenetically inactivated in several types of cancer, including gastric, colorectal and breast cancer.…”

“…Further analysis showed that the DFNA5 gene is epigenetically inactivated in several types of cancer, including gastric, colorectal and breast cancer. [13][14][15][16] Epigenetic silencing through methylation was found in 52-65% of primary tumors. In addition, in vitro studies showed that cell invasion, colony numbers, colony size and cell growth increased in cell lines after DFNA5 knockdown.…”

Proteomic Analysis of Differentially Expressed Proteins in Peripheral Cholangiocarcinoma

“…Lamin-A/C was elevated in sera of patients with a hepatocellular carcinoma [35]. Other proteins have been shown to be associated with different tumor types such as L-lactate dehydrogenase B chain which is elevated in lung cancer [36], niban which is overexpressed in renal tumors [37], and non-syndromic hearing impairment protein 5 which shows altered expression in colorectal cancer [38].…”