Hypermethylation of a cluster of Krüppel-type zinc finger protein genes on chromosome 19q13 in oropharyngeal squamous cell carcinoma.

Identification of epigenetically affected genes has become an important tool for understanding both normal and aberrant gene expression in cancer. Here we report a whole-genome analysis of DNA methylation profiles in fresh-frozen oropharyngeal squamous cell carcinoma (OPSCC) tissues and normal mucosa samples using microarray technology with patient genomic DNA. We initially compared whole-genome patterns of DNA methylation among 24 OPSCC primary tumors and 24 matched normal mucosal samples. From a survey of 27,578 CpG dinucleotide loci spanning more than 14,000 genes, we identified 958 CpG loci in which measurements of DNA methylation were altered in the primary tumors relative to the normal mucosal samples. These alterations were validated in an independent set of 21 OPSCC patients. A survey of these loci by chromosomal location revealed an abnormally high number of differentially methylated loci on chromosome 19. Many of the loci on chromosome 19 are associated with genes belonging to the Krüppel-type zinc finger protein genes. Hypermethylation was accompanied by a significant decrease in expression of these genes in OPSCC primary tumors relative to adjacent mucosa. This study reports the epigenetic silencing of Krüppel-type zinc finger protein genes on chromosome 19q13 in oropharyngeal cancer. The aberrant methylation of these genes represents a new avenue of exploration for pathways affected in this disease.

Unique DNA methylation loci distinguish anatomic site and HPV status in head and neck squamous cell carcinoma.

PURPOSE: We have used a genome-wide approach to identify novel differentially methylated CpG dinucleotides that are seen in different anatomic sites of head and neck squamous cell carcinoma (HNSCC), as well as those that might be related to HPV status in the oropharynx. EXPERIMENTAL DESIGN: We conducted genome-wide DNA methylation profiling of primary tumor samples and corresponding adjacent mucosa from 118 HNSCC patients undergoing treatment at Montefiore Medical Center, Bronx, NY, using the Illumina HumanMethylation27 beadchip. For each matched tissue set, we measured differentially methylated CpG loci using a change in methylation level (M-value). RESULTS: When datasets were individually analyzed by anatomic site of the primary tumor, we identified 293 differentially methylated CpG loci in oral cavity squamous cell carcinoma (SCC), 219 differentially methylated CpG loci in laryngeal SCC, and 460 differentially methylated in oropharyngeal SCC. A subset of these differentially methylated CpG loci was common across all anatomic sites of HNSCC. Stratification by HPV status revealed a significantly higher number of differentially methylated CpG loci in HPV+ patients. CONCLUSION: Novel epigenetic biomarkers derived from clinical HNSCC specimens can be used as molecular classifiers of this disease, revealing many new avenues of investigation for this disease.

Site-specific molecular signatures predict aggressive disease in HNSCC.

It is known that head and neck squamous cell carcinomas (HNSCC) originating from different anatomic locations can exhibit varying behavior that is not predictable by histopathology of the primary tumor. Using a microarray containing 27,323 cDNA clones, we generated sets of gene expression profiles for 36 HNSCC primary tumors (12 oral cavity, 12 oropharynx, and 12 larynx/hypopharynx). From these datasets, we ranked genes according to their ability to differentiate between patients whose disease progressed within a 24 month period (aggressive phenotype) and those that did not (non-aggressive phenotype) based on levels of gene expression. A merging of datasets from the three sites revealed that only a fraction of identified genes were shared between any two sites. This contrasted greatly with the significant overlap (approximately 50%) in down-regulated genes identified in tumor/normal comparisons using cases both from oropharynx and larynx/hypopharynx. From these data, we conclude that HNSCC tumors originating from different anatomic sites share consistent changes in gene expression when comparing primary tumors to normal adjacent mucosa; these common changes most likely reflect alterations required for tumor development. In contrast, once a tumor has developed, tumor-host interactions at the different anatomic sites are likely responsible for the site-specific signatures associated with aggressive versus non-aggressive disease. Predictions of outcome based on gene expression profiling are therefore heavily influenced by the anatomic site of the primary tumor.

D1S80 single-locus discrimination among African populations.

The highly polymorphic D1S80 locus has no known genetic function. However, this variable number of tandem repeats (VNTR) locus has been highly valuable in forensic identification. In this study we report the allele and genotype frequencies of five African populations (Benin, Cameroon, Egypt, Kenya, and Rwanda), which can be used as databases to help characterize populations and identify individuals. The allele frequencies were used to infer genetic associations through phylogenetic, principal component, and G test statistical analyses. Compliance with Hardy-Weinberg equilibrium expectations was determined as were F(ST) estimates, theta p values, and power of discrimination assessment for each population. Our analyses of 28 additional populations demonstrate that the D1S80 locus alone can be used to discriminate geographic and ethnic groups. We have generated databases useful for human identification and phylogenetic studies.