Loss of heterozygosity at 9q33 and hypermethylation of the DBCCR1 gene in oral squamous cell carcinoma

Abstract

The DBCCR1 gene at chromosome 9q33 has been identified as a candidate tumour suppressor, which is frequently targeted by promoter hypermethylation in bladder cancer. Here, we studied the possible involvement of DBCCR1 in the development of oral squamous cell carcinoma. DNA from 34 tumours was examined for loss of heterozygosity (LOH) at three markers surrounding DBCCR1 and for hypermethylation of the DBCCR1 promoter, using methylation-specific PCR and methylation-specific melting-curve analysis. LOH was found in 10 of 31 cases (32%), and DBCCR1 hypermethylation was present in 15 of 34 cases (44%). Hypermethylation of DBCCR1 was also present in three of seven epithelial tissues adjacent to the tumours, including two hyperplastic and one histologically normal epithelia. Furthermore, of four oral leukoplakias with dysplasia, one showed LOH at 9q33 and two showed DBCCR1 hypermethylation. These data suggest that LOH at 9q33 and hypermethylation of the DBCCR1 promoter are frequent and possibly early events in oral malignant development. Oral cancer comprises about 3% of all newly diagnosed cancer cases in the Western countries. Despite advances in therapy, the 5-year survival rate after diagnosis is still poor and remains B50% (Landis et al, 1999;Silverman, 2001). Clinically, oral carcinomas often develop in a two-step process. The first step is characterised by the appearance of potentially malignant lesions such as leukoplakias and erythroplakias, and the second step is characterised by the development of carcinomas. However, clinical and histopathological features are insufficient measures for predicting the prognosis of potentially malignant lesions (Warnakulasuriya, 2000(Warnakulasuriya, , 2001. Furthermore, a recent study indicated that clinically and histologically normal mucosa adjacent to tumours may harbour patches of genetically altered cells (Braakhuis et al, 2003). It is, therefore, important to find molecular markers for identifying the minor fraction of oral lesions that will develop into carcinoma.Loss of heterozygosity (LOH) at multiple chromosome regions and genetic and epigenetic alterations of several proto-oncogenes and tumour suppressor genes have been demonstrated in oral carcinomas, including alterations of the TP53, p16, p15, MGMT, Ecadherin genes and RAS (Califano et al, 1996;Partridge et al, 1999;Williams, 2000;Ogi et al, 2002;Viswanathan et al, 2003). In addition, our previous study showed that hypermethylation of the ABO gene promoter was associated with loss of expression of A/B antigen in approximately one-third of oral squamous cell carcinomas (Gao et al, 2004). LOH at 9q34, in which the ABO gene is located, was also a frequent event in these tumours. However, a number of tumours from AO and BO heterozygotes showed deletion of the O allele, which does not encode a functional glycosyltransferase, suggesting the existence of an additional tumour suppressor gene on chromosome 9q. The DBCCR1 (deleted in bladder cancer chromosomal region candidate 1) gene at chromosome 9q33 was identified as...

Tumorigenic Heterogeneity in Cancer Stem Cells Evolved from Long-term Cultures of Telomerase-Immortalized Human Mesenchymal Stem Cells

“…AF027734) was examined by methylation-specific PCR (32). Genomic DNA was treated with sodium bisulfite (33), and primer sequences and conditions for methylation-specific PCR analysis of the DBCCR1 gene promoter were as described (34). Amplification products were resolved in a 2% agarose gel.…”

Expression of the FAM5C in tongue squamous cell carcinoma

“…The DBCCR1 gene has been reported as the gene functionally affected by frequent loss of 9q32-33 in transitional cell carcinomas of the urinary bladder and identified as a candidate tumor suppressor, which is frequently targeted by promoter hypermethylation in bladder cancer (25). It has been reported that LOH at 9q33 and hypermethylation of the DBCCR1 promoter are frequent and possibly early events in oral SCC development (26), however, Gao et al did not perform DNA mapping array analysis. In our whole-genome analysis of LOH, loss of CNA (one copy) was observed in the 9q33 region.…”

Frequent hypermethylation of DBC1 in malignant lymphoproliferative neoplasms

“…26 MS-PCR was performed using previously described primers and conditions. 15 For MS-MCA, two primer sets were used. The first set (5 0 -GTGGGAATTTGGGAGAGTTTT-3 0 and 5 0 -AA TATAAACCAAACTACTAAAAACCAAATA-3 0 ) amplifies a 100-bp region (including 7 CpG sites) of the DBC1 5 0 CpG island (nt.…”

“…12 Fine mapping analysis in bladder cancer led to the identification of a putative tumor suppressor gene at 9q33.1, which has been designated as DBC1 (deleted in bladder cancer 1). 13 The 5 0 region of DBC1 contains a CpG island that is aberrantly hypermethylated in approximately 50% of bladder cancer cell lines and tumors, 13,14 40% of oral squamous cell carcinomas, 15 80% of non-small cell lung cancer cell lines, and a proportion of primary non-small cell lung cancer tumors. 16 In bladder cancer, lowdensity DBC1 promoter methylation was shown to occur in an age-related manner in the matched normal tissue, indicating that DBC1 promoter methylation may constitute an early event in carcinogenesis.…”