Abstract A8: Role of the WWOX gene in non-small cell lung cancer

Abstract

Abstract Lung cancer is the most common cause of cancer-related deaths worldwide and like many other cancers is affected by different genetic, epigenetic and environmental factors. The WWOX gene is a tumor supressor gene located on 16q23.3–24.1. It has been shown that it loses its function due to differences in genetic and epigenetic mechanisms. In this study we investigated whether the presence of WWOX gene mutations in lung cancer. The entire coding exons and flanking intronic sequences of the gene were analysed by PCR amplification from the genomic DNA and direct sequencing in 50 patients with non-small cell lung cancer (NSCLC). WWOX gene mutations were detected in five out of 50 primary tumors (10%). One of these mutations was an insertion in exon 4 at the third nucleotide of codon 120. This mutation was observed in 2 patients and leads to a frameshift creating a stop codon at codon 133. The second mutation was an insertion at position 2583 which also causes a shift in the reading frame. Finally, heterozygous C→G transitions on position 2807 at the first nucleotide of codon 282 (exon 8) were identified in 2 patients. This mutation affecting codon 282 leads to the substitution of alanine instead of proline. We also observed a previously defined G to A polymorphism at the nucleotide 2196 in homozygous and heterozygous form in 20 and 5 patients, respectively. Additionally we detected 12 different intronic substitutions. In addition to inactivating mutations target genes may also be silenced epigenetically. Therefore, besides mutation screening we also analyzed the methylation profile of the promoter region of the WWOX gene in tumor tissue and adjacent non-cancerous tissue samples by bisulphite modification and methylation-specific PCR. Promoter methylation was detected in 76% of the tumor tissue samples. While 20% of the samples displayed partial methylation 56% were completely methylated. In the adjacent normal tissue samples partial and complete methylation frequencies were 6% and 58%, respectively. Methylation frequency was significantly higher in the tumor tissue samples than in normal tissue samples (p=0.014). The high frequency of mutations and epigenetic modifications suggest that the WWOX gene may play a significant role in the etiology of NSCLC. Citation Information: Cancer Res 2009;69(23 Suppl):A8.