Methylation in head and neck squamous cell carcinoma. (2007)

In order to improve treatment and facilitate timely detection in Head and Neck Squamous Cell Carcinoma (HNSCC), elucidation of early detection markers is crucial.DNA methylation markers are advantageous, because DNA methylation is an early event.Following an overview on methylation in HNSCC in Chapter 1, we describe a genomewide screen using Restriction Landmark Genomic Scanning (RLGS) in Chapter 2. This analysis found a set of potential tumor suppressor genes that are commonly methylated and downregulated in HNSCC.Not all relevant candidates are detected by RLGS because of limitations of the assay.In Chapter 3, a candidate gene approach identified C/CAAT enhancer binding protein alpha (C/EBP), a gene previously shown to exhibit tumor suppressor activity in acute myeloid leukemia (AML) and lung cancer, as a gene of interest.C/EBP tumor suppressor activity in lung cancer has previously been shown to be downregulated by epigenetic mechanisms.More recently, this gene has been found to be downregulated in HNSCC.This prompted investigation into the involvement of epigenetics in downregulating C/EBP in HNSCC.It was revealed that C/EBP is downregulated in HNSCC by loss of heterozygosity (LOH) and upstream DNA methylation.Also, C/EBP C/EBP expression analysis for methylated HNSCC patients and cell lines.. 18 Quantitative RT-PCR analysis on HNSCC patients.19 Analysis of C/EBP tumor suppressor activity in a HNSCC cell line.20 C/EBP overexpression in vivo 21 Analysis of C/EBP increasing involucrin expression in HNSCC.. 22 C/EBP methylation and promoter analyses in cell lines.23 USF1 and SP1 binding and transcriptional activation in SCC22B cell line.24 C/EBP promoter activity with dominant negative NFkB present.. 25 AP2 suppresses C/EBP promoter activity 26 AP2 downregulation relieves C/EBP upstream methylation... 27 AP2 expression in HNSCC patient tumor samples and cell lines.. 28 C/EBP silencing and p30 C/EBP overexpression in SCC22B cells.29 Working model depicting AP2 initiation of C/EBP silencing in HNSCC.CHAPTER 1 PROMOTER DNA METHYLATION IN HEAD AND NECK SQUAMOUS CELL CARCINOMA (HNSCC) 1.1 HNSCC Risk Factors Head and neck squamous cell carcinoma (HNSCC) is the 6 th most common cancer in the world (1).According to the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) cancer statistics review for 2007, 34,360 individuals will be diagnosed with HNSCC, and 7,550 men and women will die of this cancer.Incidence rose significantly in the 20 th century, particularly in people under 60 years of age (2).In the 1980's, two US cancer centers reported an increase in oral tongue cancers (OTCs) in men less than 40 years old.Following this, there was a two-fold increase in OTC mortality rates for men less than 30 years of age, suggesting a strong effect of year of birth on incidence, such that men born after 1920 have increased HNSCC risk (2).HNSCC, as its name suggests, affects different anatomical sites within the head and neck (Figure 1).Studies indicate that incidence is influenced by age, sex, race, primary site, date of birth after 1915, genetic factors, and geographic region.Furthermore, lifestyle choices (i.e.alcohol and tobacco use, oral hygiene, and sexual behavior) greatly influence risk for HNSCC.