Original ResearchAberrant expression of the ZDHHC14 gene in squamous cell carcinoma of the human tongue
Introduction
Oral cancer is a challenging clinical problem and a leading cause of cancer deaths in men and women, with an estimated 300,000 new cases annually worldwide [1]. Tongue cancer, the most common oral cancer, is an aggressive tumor that particularly affects chronic smokers, drinkers, and those who chew betel squid [2]. The most important prognostic indicator for patients with tongue squamous cell carcinoma (TSCC) is metastasis to the cervical lymph nodes or distant organs. Most patients with TSCC who have either suspected or proven metastases to the regional lymph nodes are candidates for composite resection in which the lesion, surrounding tissues, and lymph nodes of the neck are removed. This procedure often produces grievous deformities and defects of the jaw and extensive loss of soft tissue, making functional and esthetic rehabilitation a long, involved process. Molecular alterations in a number of oncogenes and tumor suppressor genes associated with metastasis of TSCC could be important clues to predicting and suppressing metastasis.
It is certain that genetic aberrations play an important role in TSCC, but it is still unclear which genetic events are involved in tumor metastasis and progression. There are obviously many unknown small mutations that could be important for carcinogenesis and progression in TSCC. Historically, two key techniques were used to detect DNA copy number variations in DNA samples: comparative genomic hybridization (CGH) and loss of heterozygosity (LOH) analysis. The CGH technique can use bacterial artificial chromosome, cDNA, and oligonucleotides, and it is more sensitive because its higher resolution can be studied. Hybridization to single nucleotide polymorphism (SNP) arrays is an efficient method to simultaneously detect genome-wide LOH and DNA-copy number aberrations [3], [4] (DNA–CNA). Several recent studies have successfully used this array to identify consistent LOH regions and DNA–CNA in breast cancer [5], [6], [7], [8], [9], bladder cancer [10], [11], prostate cancer [12], [13], osteosarcoma [14], lung cancer [15], [16], and oral SCC-derived cell lines [17], [18]. However, only a limited number of studies have used this assay to identify consistent LOH regions and DNA–CNA in human TSCCs.
In the current study, we analyzed consistent DNA–CNA among lymph node-positive (pN+) cases and lymph node-negative (pN−) cases in TSCC using the Affymetrix® 10K SNP Mapping Array. In the chromosomal region identified by the DNA–CNA, we then reconfirmed the presence of novel oncogenes. The mRNA expression levels of the genes in this region were examined to identify the role of the gene.
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Cells
The six human TSCC-derived cell lines used in this study were HSC-3, HSC-4, SAS, SCC-4, OSC-19, and OSC-20 (Human Science Research Resources Bank, Osaka, Japan). All cell lines were maintained at 37 °C (humidified atmosphere 5% CO2/95% air) on 150 × 20-mm tissue culture dishes (Nunc, Roskilde, Denmark) and cultured in Dulbecco's modified Eagle's medium F-12 HAM (Sigma, St. Louis, MO, USA) with 10% fetal bovine serum (Sigma) plus 50 units/ml penicillin and streptomycin [19].
Two normal oral
Analysis of DNA mapping array using Affymetrix 10K SNP Mapping Array
We applied whole-genome analysis of CNA in the specimens from the five TSCC cases using Affymetrix 10K SNP Mapping Array. When we compared the DNA copy numbers from three pN+ cases with the two pN− cases, we found that 16 regions common to both showed gains and 23 regions common to both showed losses. Copy numbers with a greater than two-fold change in expression were considered significant. These detected regions that may be associated with the lymph node metastasis of TSCCs were chromosome
Discussion
Several studies have successfully used the Affymetrix 10K SNP Mapping Array to identify consistent CNA regions [3], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]. However, to the best of our knowledge no previous reports have identified CNA in the 6q25.3 region as we observed in the current study.
Recently, CNA in whole-genome analyses of TSCCs have been reported using the Affymetrix 10K SNP Mapping Array [21]. In that study, Zhou et al. detected genome-wide CNA
Acknowledgements
We thank Lynda C. Charters for editing this manuscript. This work was supported by a Research Grant from the Ministry of Education, Science and Culture, Japan (No. 21792033).
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