**7. Challenges in epigenetic cancer therapy**

Epigenetic mechanisms regulate the interpretation of genetic information. As such, our knowledge of these mechanisms is essential for understanding the phenotypic plasticity of cells, both in the context of normal cellular differentiation and in human disease (Freinberg, 2007). Research over the past two decades has identified two major levels of epigenetic modification: DNA methylation and covalent histone modifications (Strahl & Allis, 2000 and Klose & Bird, 2006). DNA methylation is mediated by a family of enzymes termed DNA methyltransferases (DNMTs) (Goll & Bestor, 2005), while histone modification patterns are established and maintained by a diverse set of enzymes that add or subtract acetyl-, methyl-, and other modifications to various amino acids of histone proteins (Kouzarides, 2007). Both regulatory mechanisms cooperate to determine the expression potential of individual genes.

For detection of cancel cells in body fluids, a high-sensitivity method is necessary. One way is mutation detection in cells because the exact location of a mutation within a gene is usually unknown, many primer sets are necessary for complete analysis. In contrast, aberrant methylation of DNA molecule of cancer cells, even in very few in number, can be sensitively detected by using Methylation-Specific PCR method (MSP), only with one set of PCR primer can be performed on chemically stable DNA, not on RNA (Herman et al,1996 and Laird, 2003).

Considering that some aberrant DNA methylation is present in early stages of carcinogenesis, there is a possibility that such demethylating agents may protect against some cancers (Laird et al, 1995). Demethylating agents are including DNMT1 inhibitors group (Azacitadine, Decitabine, Zebularine and MG98), procainamide, procain and EGCG (epigallocatechin-3-gallate) (Fang et al, 2003 and Villar-Garea et al, 2003). Inhibitors of DNMTs have been widely used in cell culture systems to reverse abnormal DNA hypermethylation and restore silenced gene expression. However, only limited success has been achieved in clinical trials with these drugs (Thibault et al, 1998 and Goffin & Eisenhouer, 2002). Also, nucleosides analog inhibitors of DNMTs may promote genomic instability and increase the risk of cancer in other tissues, because have many potential side effects such as myelotoxicity, mutagenesis and tumorigenesis (Jones &Taylor, 1980 and Gaudet et al, 2003). There is an attractive alternative for possible clinical use of nonnucleoside analog DNMT inhibitors.

The use of these drugs raises questions regarding their potential to affect non-cancerous cells epigenetically. However, normal cells divide at a slower rate than malignant cells and incorporate less of these drugs into their DNA resulting in less of an effect on DNA methylation. Azacitadine and decitabine are labil and have acute hematological toxicities. Zebularine, a next generation DNA methylation inhibitor, might possibly overcome these

Epigenetics in Head and Neck Squamous Cell Carcinoma 191

I would like to thank **Dr. Richard A. Stein**, from Department of Molecular Biology, Lewis Thomas Lab, Princeton University, Princeton, NJ, USA, for his help and for my initiation in

Ali AH, Kondo K, Namura T, Senba Y, Takizawa H, Nakagawa Y, Toba H, Kenzaki K,

Araki D, Uzawa K, Watanabe T, et al. (2002) Frequent allelic losses on the short arm of

Arita A, Costa M. Epigenetics in metal carconogenesis: nickel, arsenic, chromium and

Ariza M, Llorente JL et al. (2004) Comparative genomic hybridization in primary sinonasal

Ashby, J., Tennant, R.W. (1991) Definitive relationships among chemical structure,

Baert-Desurmont S, Buisine MP, Bessenay E, et al. (2007) Partial duplications of the MSH2

Balderas-Loaeza A, Anaya-Saavedra G, Ramirez-Amador VA et al. (2007) Human

Baylin SB, Herman JG. (2000) DNA Hypermethylation in tumorigenesis: epigenetics joins

Bollati V, Baccarelli A, Hou L et al. (2007) Changes in DNA methylation patterns in subjects

Bornholdt J, Hansen J et al. (2008) KRAS mutation in sinonasal cancer in relation to wood

Bornholdt J, Saber AT. (2007) Inflammatory response and genotoxicity of seven wood dust

Chang HW, Ling GS, Wei WI, Yuen AP. (2004) Smoking and drinking can induce p15

Chen H, Ke Q, Kluz T, Yan Y, Costa M. (2006) Nickel ions increase histone H3 lysine 9 dimethylation and induce transgene silencing. *Mol Cell Biol*:26;3728-3737.

with head and neck squamous cell carcinoma. *Cancer*; 101: 125–132.

methylation in the upper aerodigestive tract of healthy individuals and patients

virus with oral squamous cell carcinomas. *Int J Cancer*; 120:2165-2169. Batsakis JG, Suarez P. (2001) Schneiderian papillomas and carcinomas: a review. *Adv Anat* 

carcinoma of the oral cavity. *Int J Oncol*; 20: 355– 360.

cadmium. *Metallomics* 2009:1; 222-228.

adenocarcinomas. *Cancer*; 100 :335-341.

*Mutation Research*; 257:229-306.

genetics. *Trends Genet;* 16: 168–174.

dust exposure. *BMC Cancer*; 8, 53.

exposed to low-dose benzene. *Cancer Res*:67;876-880.

in the human epithelial cell line A594. *Mutat Res*; 632:78-88.

Sakiyama S, Tangoku A. (2011) Aberrant DNA methylation of some tumor suppressor genes in lung cancers from workers with chromate exposure. *Mol* 

chromosome 1 and decreased expression of the p73 gene at 1p36.3 in squamous cell

carcinogenicity and mutagenicity for 301 chemicals tested by the U.S. NTP.

and MLH1 genes in hereditary nonpolyposis colorectal cancer. *Eur J Hum Genet*; 15:

papillomavirus-16 DNA methylation patterns support a causal association of the

**8. Acknowledgements** 

the mystery of epigenetics.

383–386.

*Pathol*;8:53–64.

*Carcinog*:50;89-99.

**9. References** 

problems (Marquez et al, 2005 and Yoo et al, 2008). The non-nucleoside analogue inhibitors are not as potent as the nucleoside analogues and therefore this issue needs for improvement (Chuang et al, 2005).

Another prominent example for an epigenetic drug is the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza), which has been approved for the treatment of cutaneous T cell lymphoma (Marks & Breslow, 2007). Another HDAC inhibitor (Romidepsin, Istodax) has very recently been approved for the same indication. As of today, there are at least 20 structurally different HDAC inhibitors in clinical trials, either in monotherapy or in combination therapy trials for hematological and solid tumors. It should be noted that combination therapies of HDAC inhibitors with other anticancer drugs or with radiation therapy have shown a wide range of synergistic effects, both in preclinical models and in early clinical trials (Marks & Xu, 2009). The identification of tumor-specific epigenetic pathways represents a critically important step toward the establishment of targeted epigenetic cancer therapies. One possibility is the targeting of defined DNMTs with specific oncogenic functions (Linhart et al, 2007). Another possibility is the discovery of tumor-specific functions for enzymes with specific histone modification activities. A third option is the identification of tumor-specific interactions between epigenetic pathways, like interaction between DNMTs and HDACs through methyl-CpG binding proteins.

While the clinical application potential of the interaction between DNA methylation and histone hypoacetylation remains to be established, the results from preclinical experiments clearly suggest crosstalk between epigenetic silencing systems that warrants further investigation. A particular interesting finding in this context is the interaction between histone lysine methylation and DNA hypermethylation. Several independent studies have shown that genes that are marked by bivalent chromatin structures (i.e. the presence of both H3K4 and H3K27 methylation marks) in embryonic stem cells have a high probability of becoming de novo methylated in cancer (Schlesinger et al, 2007; Ohm et al, 2007; Widschwendter et al, 2007). The mechanistic details of these interactions are only beginning to be elucidated. The available data, however, raise the intriguing possibility that cancerspecific epigenetic mutations reflect the stem cell origin of tumors. As such, targeting of the interaction between bivalent chromatin structures and DNA hypermethylation might represent a highly specific approach toward erasing cancer-specific epigenetic mutations.

 "Cancer has been the tip of the iceberg, but knowledge in cancer epigenetics is going to translate to other diseases. It is clear to me that there is no disease that is pure genetics, and there is no disease that is pure epigenetics. All diseases, from cancer to neurological disorders to cardiovascular conditions, are mixtures of genetics, epigenetics, and the environment" says Manuel Esteller, M.D., Ph.D., director of the Cancer Epigenetics and Biology Program in Barcelona.

Epigenomics-based diagnostic tools for early cancer detection represent an exciting development. Tumors shed their DNA into the blood, and epigenetic changes that occur early during tumorigenesis, sometimes even in premalignant lesions, can provide valuable biomarkers. More than ever, it is imperative to focus on understanding the mechanistic details of malignant transformation initiated by human pathogens, an area that promises exciting prophylactic, diagnostic, and therapeutic applications.

#### **8. Acknowledgements**

I would like to thank **Dr. Richard A. Stein**, from Department of Molecular Biology, Lewis Thomas Lab, Princeton University, Princeton, NJ, USA, for his help and for my initiation in the mystery of epigenetics.

#### **9. References**

190 Otolaryngology

problems (Marquez et al, 2005 and Yoo et al, 2008). The non-nucleoside analogue inhibitors are not as potent as the nucleoside analogues and therefore this issue needs for

Another prominent example for an epigenetic drug is the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza), which has been approved for the treatment of cutaneous T cell lymphoma (Marks & Breslow, 2007). Another HDAC inhibitor (Romidepsin, Istodax) has very recently been approved for the same indication. As of today, there are at least 20 structurally different HDAC inhibitors in clinical trials, either in monotherapy or in combination therapy trials for hematological and solid tumors. It should be noted that combination therapies of HDAC inhibitors with other anticancer drugs or with radiation therapy have shown a wide range of synergistic effects, both in preclinical models and in early clinical trials (Marks & Xu, 2009). The identification of tumor-specific epigenetic pathways represents a critically important step toward the establishment of targeted epigenetic cancer therapies. One possibility is the targeting of defined DNMTs with specific oncogenic functions (Linhart et al, 2007). Another possibility is the discovery of tumor-specific functions for enzymes with specific histone modification activities. A third option is the identification of tumor-specific interactions between epigenetic pathways, like interaction between DNMTs and HDACs through methyl-CpG

While the clinical application potential of the interaction between DNA methylation and histone hypoacetylation remains to be established, the results from preclinical experiments clearly suggest crosstalk between epigenetic silencing systems that warrants further investigation. A particular interesting finding in this context is the interaction between histone lysine methylation and DNA hypermethylation. Several independent studies have shown that genes that are marked by bivalent chromatin structures (i.e. the presence of both H3K4 and H3K27 methylation marks) in embryonic stem cells have a high probability of becoming de novo methylated in cancer (Schlesinger et al, 2007; Ohm et al, 2007; Widschwendter et al, 2007). The mechanistic details of these interactions are only beginning to be elucidated. The available data, however, raise the intriguing possibility that cancerspecific epigenetic mutations reflect the stem cell origin of tumors. As such, targeting of the interaction between bivalent chromatin structures and DNA hypermethylation might represent a highly specific approach toward erasing cancer-specific epigenetic mutations.

 "Cancer has been the tip of the iceberg, but knowledge in cancer epigenetics is going to translate to other diseases. It is clear to me that there is no disease that is pure genetics, and there is no disease that is pure epigenetics. All diseases, from cancer to neurological disorders to cardiovascular conditions, are mixtures of genetics, epigenetics, and the environment" says Manuel Esteller, M.D., Ph.D., director of the Cancer Epigenetics and

Epigenomics-based diagnostic tools for early cancer detection represent an exciting development. Tumors shed their DNA into the blood, and epigenetic changes that occur early during tumorigenesis, sometimes even in premalignant lesions, can provide valuable biomarkers. More than ever, it is imperative to focus on understanding the mechanistic details of malignant transformation initiated by human pathogens, an area that promises

exciting prophylactic, diagnostic, and therapeutic applications.

improvement (Chuang et al, 2005).

binding proteins.

Biology Program in Barcelona.


Epigenetics in Head and Neck Squamous Cell Carcinoma 193

Hasegawa M, Nelson HH, Peters E, Ringstrom E, Posner M, Kelsey KT. (2002) Patterns of

Herman JG, Graff S, Myohanen BD, Nelkin and Baylin SB. (1996) Methylation specific PCR:

Iliopoulos D, Hirsch HA, Struhl K. (2009) An epigenetic switch involving NF-kappaB, Lin28,

Iliopoulos D, Jaeger SA, Hirsch HA, Bulyk ML, Struhl K. (2010) STAT3 activation of miR-21

Jones PA. (2003) Epigenetics in Carcinogenesis and cancer prevention. *Ann N Y Ac Sci* ; 983:

Jones PA, Taylor SM. (1980) Cellular differentiation, cytidine analogs and DNA methylation.

Kalathas D, Theocharis DA, Bounias D et al. (2009) Alterations of glycosaminoglycan

Kalathas D, Triantaphyllidou IE, Mastronikolis NS et al. (2010) The chondroitin/dermatan

Kang J, Zhang D, Chen J, Lin C, Liu Q. (2004) Involvement of histone hypoacetylation in

Kato K, Hara A, Kuno T, et al. (2006) Aberrant promoter hypermethylation of p16 and

Kauppinen T, Vincent R et al. (2006) Occupational exposure to inhalable wood dust in member states of the European Union. *Ann Occup Hyg*; 50(6):549-561. Kasprzak KS, Sunderman FW Jr, Salnikow K. (2003) Nickel carcinogenesis. *Mutat Res*:533;67-

Ke Q, Davidson T, Chen H, Kluz T, Costa M. (2006) Alterations of histone modifications and

Kim JS, Kim H, Shim YM, Han J, Park J, Kim DH. (2004) Aberrant methylation of the FHIT

Klein CB, Su L, Bowser D, Leszczynska J. (2002) Chromate-induced epimutations in

Klose RJ, Bird AP. (2006) Genomic DNA methylation: the mark and its mediators. *Trends* 

Korinth D, Pacyna-Gengelbach M et al. (2005) Chromosomal imbalances in wood dust-

mammalian cells. Environ Health Perspect. Oct;110 Suppl 5:739-43.

gene in chronic smokers with early stage squamous cell carcinoma of the lung.

related adenocarcinomas of the inner nose and their associations with pathological

transgene silencing by nickel chloride. *Carcinogenesis*:27;1481-8.

inflammation to cancer. *Mol Cell*; 39(4):493-506.

expressional studies. *Oncol Rep.*; 22:369–375.

epigenetic studies. *Head Neck Oncol*; 2:27.

mucosa. *J Cancer Res Clin Oncol*; 132: 735–743.

*Oncogene*; 21: 4231–4236.

93:9821-9826.

139(4):693-706.

213–219.

97.

*Cell*; 20:85-93.

*Inorg Chem*:9(6);713-23.

*Carcinogenesis*; 25: 2165–2171.

parameters. *J Pathol*; 207:207-215.

*Biochem Sci*; 31: 89–97.

gene promoter methylation in squamous cell cancer of the head and neck.

a novel PCR assay for methylation status of CpG islands. *Proc Natl Acad Sci*;

Let-7 microRNA, and IL6 links inflammation to cell transformation. *Cell*.;

and miR-181b-1 via PTEN and CYLD are part of the epigenetic switch linking

disaccharide content and composition in colorectal cancer: Structural and

sulfate synthesizing and modifying enzymes in laryngeal cancer: expressional and

Ni2+-induced bcl- 2 down-regulation and human hepatoma cell apoptosis. *J Biol* 

MGMT genes in oral squamous cell carcinomas and the surrounding normal


Chuang JC, Yoo CB, Kwan JM, Li TW et al. (2005) Camparison of biological effects of non-

Demers, PA, Teschke K, Kennedy SM. (1997) What to do about softwood ? A review of

el-Deiry WS. (1998) p21/p53, cellular growth control and genomic integrity. *Curr Top* 

Ellen TP, Kluz T, Harder ME, Xiong J, Costa M. (2009) Heterochromatinization as a potential mechanism of nickel-induced carcinogenesis. *Biochemistry*:48;4626-32. Fang MZ, Wang Y, Ai N, Hou Z, Sun Y et al. (2003) Tea polyphenol(-)epigallocatechin-3-

Feinberg AP. (2007) Phenotypic plasticity and the epigenetics of human disease. *Nature*; 447:

Fernandez AF, Esteller M. (2010) Viral epigenomes in human tumorigenesis. *Oncogene;*

Frattini M, Perrone F et al. (2006) Phenotype-genotype correlation: challenge of intestinal-

Gao S, Eiberg H, Krogdahl A, Liu CJ, Sørensen JA. (2005) Cytoplasmic expression of E-

Gaudet F, Hodgson JG, Eden A, Jackson-Grusby L, Dausman J. (2003) Induction of tumors

Gillison ML, Koch WM, Capone RB, Spafford M, Westra WH, Wu L, et al. (2000) Evidence

Goffin J, Eisenhauer E. (2002) DNA methyltransferase inhibitors-state of the art. *Ann Oncol*,

Goll MG, Bestor TH. (2005) Eukaryotic cytosine methyltransferases. *Annu Rev Biochem*; 74:

Golebiowski F, Kasprzak KS. (2005) Inhibition of core histones acetylation by carcinogenic

Gujrathi C, Pathak I, Freeman J, *et al*. (2003) Expression of p53 in inverted papilloma and malignancy associated with inverted papilloma. *J Otolaryngol*;32:48–50. Guo M, House MG, Hooker C, Han Y, Heath E, Gabrielson E, et al. (2004) Promoter

hypermethylation of resected bronchial margins: a field defect of changes? *Clin* 

gene in oral squamous cell carcinomas. *J Oral Pathol Med*; 34: 116–119. Gasco M, Bell AK, Heath V, et al. (2002) Epigenetic inactivation of 14-3-3 sigma in oral

in mice by genomic hypomethylation. *Science*; 300:489-492.

Hanahan D, Weinberg RA. (2000) The hallmarks of cancer. *Cell*; 100:57-70.

*Ther*; 4:1515-1520.

31(4): 385-398.

433–40.

909-915.

29:1405-1420.

*Microbiol Immunol*; 227:121–137.

in cancer cell lines. *Cancer Rec*; 63: 7563-7570.

negativity. *Cancer Res*; 62: 2072–2076.

nickel (II). *Mol Cell Biochem*:279;133-139.

*Inst*.; 92(9): 709–720.

*Cancer Res*; 10:5131–6.

13:1699-1716.

481–514.

nucleotide DNA methylation inhibitors versus 5-aza-2deoxycytidine. *Mol Cancer* 

respiratory effects and recommendations regarding exposure limits. *Am J Ind Med*;

gallate inhibits DNA methyltransferase and reactivates methylation-silenced genes

type adenocarcinoma of the nasal cavity and paranasal sinuses. *Head Neck*; 28(6):

cadherin and beta-Catenin correlated with LOH and hypermethylation of the APC

carcinoma: association with p16(INK4a) silencing and human papillomavirus

for a causal association between human papillomavirus and a subset*. J Natl Cancer* 


Epigenetics in Head and Neck Squamous Cell Carcinoma 195

Munoz N, Bosch FX, de Sanjosé S, Herrero R, Castellsagué X, Shah KV, Snijders PJF, Meijer

Murray PG, Young LS. (2002) The role of the Epstein-Barr virus in human disease. Front

Murakami J, Asaumi J, Maki Y, et al. (2004) Influence of CpG island methylation status in

Nakahara Y, Shintani S, Mihara M, Ueyama Y, Matsumura T. (2001) High frequency of

Nakajima T, Shimooka H, Weixa P, et al. (2003) Immunohistochemical demonstration of 14-

Nakayama S, Sasaki A, Mese H, Alcalde RE, Tsuji T, Matsumura T. (2001) The E-cadherin

Ng IO, Lam KY, Ng M, *et al*. (1999) Expression of p21/waf1 in oral squamous cell

Nobeyama Y, Okochi-Takada E, Furuta J, et al. (2007) Silencing of tissue factor pathway

Ohm JE, McGarvey KM, Yu X, Cheng L, et al. (2007) A stem cell-like chromatin pattern may

Oka D, Yamashita S, Tomioka T, Nakanishi Y, Kato H, Kaminishi M, et al. (2009) The

Oshiro MM, Futscher BW, Lisberg A, et al. (2005) Epigenetic regulation of the cell type-

Qiu GH, Tan LKS, Loh KS et al. (2004) The candidate tumor suppressor gene BLU, located at

Paluszczak J, Misiak P, Wierzbicka M, Wozniak A, Baer-Dubowska W. (2011) Frequent

inhibitor-2 gene in malignant melanomas. *Int J Cancer*:121;301-307.

associated with cervical cancer. *N Engl J Med*; 348:518–527.

Biosci; 7:519-540.

*Oncol Rep*; 12: 339–345.

*Pathol Int*; 53: 353–360.

*Cancer*; 93: 667–673.

*Oncol*;35:63–69.

carcinomas. *Cancer Lett*; 163: 221–228.

silencing. *Nat Genet* ; 39: 237–242.

esophageal cancers. *Cancer*; 115:3412–26.

carcinoma. *Oncogene*; 23:4793-4806.

specific gene 14-3-3 sigma. *Neoplasia*; 7: 799–808.

pathogenesis. *Trends in Microbiology*; 18(10): 439-447.

CJLM. (2003) Epidemiological classification of human papillomavirus types

O6-methylguanine-DNA methyltransferase expression of oral cancer cell lines.

homozygous deletion and methylation of p16(INK4A) gene in oral squamous cell

3-3 sigma protein in normal human tissues and lung cancers, and the preponderance of its strong expression in epithelial cells of squamous cell lineage.

gene is silenced by CpG methylation in human oral squamous cell carcinomas. *Int J* 

carcinomas—correlation with p53 and mdm2 and cellular proliferation index. *Oral* 

predispose tumor suppressor genes to DNA hypermethylation and heritable

presence of aberrant DNA methylation in noncancerous esophageal mucosae in association with smoking history: a target for risk diagnosis and prevention of

the commonly deleted region 3p21.3, is an E2F-regulated, stress-responsive gene and inactivated by both epigenetic and genetic mechanisms in nasopharyngeal

hypermethylation of DAPK, RARbeta, MGMT, RASSF1A and FHIT in laryngeal squamous cell carcinomas and adjacent normal mucosa. *Oral Oncol*; 47:104-107. Paradiso A, Ranieri G, Stea B, et al. (2004) Altered p16INK4a and FHIT expression in carcinogenesis and progression of human oral cancer. *Int J Oncol*; 24: 249–255. Paschos K, Allday M. (2010) Epigenetic reprogramming of host genes in viral and microbial

Kouzarides T. (2007) Chromatin modifications and their function. *Cell*; 128: 693–705.


Laird, PW. (2003) The power and the promise of DNA methylation markers. *Nat Rev Cancer*;

Laird PW, Jackson-Grusby L, Fazeli A, Dickinson S, Jung W, Weinberg R, Jaenisch R. (1995) Suppression of intestinal neoplasia by DNA hypomethylation. *Cell*; 81:197-205. Lee JK, Kim MJ, Hong SP, Hong SD. (2004) Inactivation patterns of p16 INK4A in oral

Li LL, Shu XS, Wang ZH, Cao Y, Tao Q. (2011) Epigenetic disruption of cell signaling in

Licitra L, Suardi S et al. (2004) Prediction of TP53 status for primary cisplatic, fluorouracil,

Liebowitz D. (1994) Nasopharyngeal carcinoma: the Epstein-Barr virus association. *Seminars* 

Linhart HG, Lin H, Yamada Y et al. (2007) DNMT3b promotes tumorigenesis in vivo by

Lopez M, Aguirre JM, Cuevas N, et al. (2003) Gene promoter hypermethylation in oral

Luce D, Leclerc A. (2002) Sinonasal cancer and occupational exposures: a pooled analysis of

Marks PA, Xu WS. (2009) Histone deacetylase inhibitors: potential in cancer therapy. *J Cell* 

Marquez VE, Barchi JJ, kelley JA, Rao KV, Agbaria R et al. (2005) Zebularine: a unique

its chemistry and biology. *Nucleosides Nucleotides Necleic Acids*; 24:305-318. Martone T, Gillio-Tos A, De Marco L, Fiano V, Maule M, Cavalot A, et al. (2007) Association

McGregor F, Muntoni A, Fleming J, et al. (2002) Molecular changes associated with oral

Mikami T, Yoshida T, Numata Y, et al. (2007) Low frequency of promoter methylation of

Mork J, Lie AK, Glattre E, Hallmans G, Jellum E, Koskela P, et al. (2001) Human

molecule for an epigenetically based strategy in cancer chemotherapy. The magic of

between hypermethylated tumor and paired surgical margins in head and neck

dysplasia progression and acquisition of immortality: potential for its reversal by 5-

O6-methylguanine DNA methyltransferase and hMLH1 in ulcerative colitisassociated tumors: comparison with sporadic colonic tumors. *Am J Clin Pathol*; 127:

papillomavirus infection as a risk factor for squamous cell carcinoma of the head

12 case-control studies. *Cancer Causes Control*; 13(2):147-157.

squamous cell carcinomas. *Clin Cancer Res*; 13:5089–94.

Mhawech P. (2005) 14-3-3 proteins-an update. *Cell Res*; 15: 228–236.

azacytidine. *Cancer Res*; 62: 4757–4766.

and neck. *N Eng J Med*.; 344:1125–1131.

and leucovirin chemotherapy in ethmoid sinus intestinal-type adenocarcinoma. *J* 

gene-specific de novo methylation and transcriptional silencing. *Genes Dev*; 21:3110-

rinses of leukoplakia patients – a diagnostic and or prognostic tool? *Eur J Cancer*; 39: 2306–2309. Marks PA, Breslow R. Dimethyl sulfoxide to vorinostat: development of this histone deacetylase inhibitor as an anticancer drug. Nat

Kouzarides T. (2007) Chromatin modifications and their function. *Cell*; 128: 693–705.

squamous cell carcinomas. *Exp Mol Med*; 36: 165–171.

nasopharyngeal carcinoma. *Chin J Cancer*; 30(4):230-239.

3:253-266.

*Clin Oncol*; 22(24):4901-4906.

Biotechnol 2007; 25: 84–90.

*Biochem*; 107: 600–608.

366–373.

*oncol*; 21:376-381.

3122.


Epigenetics in Head and Neck Squamous Cell Carcinoma 197

Sun H, Zhou X, Chen H, Li Q, Costa M. (2009) Modulation of histone methylation

Syrjanen S. (2005) Human papillomavirus (HPV) in head and neck cancer. *J Clin Virol*; 32:

Toner M, O'Regan EM. (2009) Head and Neck squamous cell carcinoma in the young: a

Tanemura A, Terando AM, Sim MS, van Hoesel AQ, de Maat MF, Morton DL, Hoon DS.

Uesugi H, Uzawa K, Kawasaki K, et al. (2005) Status of reduced expression and

Upham BL, Weis LM, Trosko JE. (1998) Modulated gap junctional intercellular

van Engeland M, Weijenberg MP, Roemen GMJM, Brink M, de Bruine AP, Goldbohm RA, et

Villar-Garea A, Fraga MF, Espada J, Esteller M. (2003) Procaine is a DNA demethylating

von Zeidler SV, Miracca EC, Nagai MA, Birman EG. (2004) Hypermethylation of the p16

Vuillemenot BR, Pulling LC, Palmisano WA, Hutt JA, Belinsky SA. (2004) Carcinogen

and frequent event in mouse lung carcinogenesis. *Carcinogenesis*; 25:623–629. Westra WH. (2009) The changing face of head and neck cancer in the 21st century: the

Wensing B, Farrel PJ. (2000) Regulation of cell growth and death by Epstein-Barr virus.

Widschwendter M, Fiegl H, Egle D, Mueller-Holzner E, et al. (2007) Epigenetic stem cell

Yom SS, Rashid A et al. (2005) Genetic analysis of sinonasal adenocarcinoma phenotypes : distinct alterations of histogenetic significance. *Mod pathol*; 18(3):315-319. Yoo CB, Chuang JC, Byun H, Egger G, Yang AS et al. (2008) Long-term epigenetic therapy

spectrum or a distinct group? Part 2. *Head Neck Pathol*; 3:249-251.

Ushijima T. (2007) Epigenetic field for cancerization. *J Biochem Mol Biol* ; 40:142–50.

melanoma. *Clin Cancer Res*:15;1801-1807.

carcinoma. *Int J Mol Med*; 15: 597–602.

relationship. *Environ Health Perspect*:Suppl 4;975-981.

258-66.

S59-S66.

*Res*; 63:3133–7.

4989.

84:87-89.

*Pathol*.; 3(1):78-81.

*Microbes Infect*; 2:77-84.

signature in cancer. *Nat Genet*; 39: 157–58.

mice. *Cancer Prev Res*; 4:233-240.

and MLH1 gene silencing by hexavalent chromium. *Toxicol Appl Pharmacol*: 237;

(2009) CpG island methylator phenotype predicts progression of malignant

hypermethylation of the APC tumor suppressor gene in human oral squamous cell

communication as a biomarker of PAH epigenetic toxicity: structure-function

al. (2003) Effects of dietary folate and alcohol intake on promoter methylation in sporadic colorectal cancer: The Netherlands cohort study on diet and cancer. *Cancer* 

agent with growth-inhibitory effects in human cancer cells. *Cancer Res*; 63:4984-

gene in normal oral mucosa of smokers. *Int J Mol Med*: 14: 807–811. Thibault A, Figg WD, Bergan RC, Lush RM, Myers CE. A phase II study of 5-aza-2deoxycytidine (decitabine) in hormone independent metastatic (D2) prostate cancer. Tumori 1998;

exposure differentially modulates RAR-beta promoter hypermethylation, an early

impact of HPV on the epidemiology and pathology of oral cancer. *Head Neck* 

with oral zebularine has minimal side effects and prevents intestinal tumors in


Perrone F, Oggionni M et al. (2003) TP53, p14ARF, p16INK4a and HRAS gene molecular

Ragin CC, Reshmi SC, Gollin SM. (2004) Mapping and analysis of HPV16 integration sites in

Righini CA, de Fraipont F, Timsit JF, et al. (2007) Tumor-specific methylation in saliva: a

Rodriguez MJ, Acha A, Ruesga MT, Rodriguez C, Rivera JM, Aguirre JM. (2007) Loss of

Sadikovic B, Andrews J, Carter D, Robinson J, Rodenhiser DI. (2008) Genome-wide H3K9

Sanchez-Cespedes M, Esteller M, Wu L, et al. (2000) Gene promoter hypermethylation in tumors and serum of head and neck cancer patients. *Cancer Res*; 60: 892–895. Scherer, G., Frank, S., Riedel, K., Meger-Kossien, I., and Renner, T. (2000) Biomonitoring of

Schembri F, Sridhar S, Perdomo C, Gustafson AM, Zhang X, Ergun A, Lu J, Liu G, Zhang X,

Scully C, Field JK, Tonkawa H. (2000) Genetic aberrations in oral or head and neck

Silverman S. (1998). Epidemiology. In *Oral cancer. 5th edition*. Silverman S Jr. (Ed), 1-6, BC

Soni S, Kaur J, Kumar A, et al. (2005) Alterations of Rb pathway components are frequent

Stein RA. (2011) Epigenetics-the link between infectious diseases and cancer. JAMA;

Stephen JK, Vaught LE, Chen KM et al. (2007) Epigenetic events underlie the pathogenesis

Strahl BD, Allis CD. (2000) The language of covalent histone modifications. *Nature*; 403: 41–

Decker Inc, ISBN 1-55089-215-4. Hamilton, Ontario, USA.

of sinonasal papillomas. *Modern Pathol*; 20:1019-1027.

patients with squamous cell carcinoma. *Oncology*; 68: 314–325.

squamous cell carcinoma. A prognostic tool? *Cancer Lett*; 245: 263–268. Rohatgi N, Kaur J, Srivastava A, Ralhan R. (2005) Smokeless tobacco (khaini) extracts

a head and neck cancer cell line. *Int J Cancer*; 110:701–709.

sinuses. *Int J Cancer*; 105(2):196-203.

*Cancer Res*; 13: 1179–85.

*Oncol*; 41: 806–820.

cells. *J Biol Chem*:283;4051-60.

cancer. *Nat Genet*; 39: 232–36.

305(14):1484-1485.

5.

cycle control. *Oral Oncol*; 36: 256–263.

Persons. *Cancer Epidemiol. Biomark.*, 9:373-380

analysis in intestinal-type adenocarcinoma of the nasal cavity and paranasal

promising biomarker for early detection of head and neck cancer recurrence. *Clin* 

expression of DNA repair enzyme MGMT in oral leukoplakia and early oral

modulate gene expression in epithelial cell culture from an oral hyperplasia. *Oral* 

histone acetylation profiles are altered in benzopyrene-treated MCF7 breast cancer

Exposure to Polycyclic Aromatic Hydrocarbons of Nonoccupationally Exposed

Bowers J, Vaziri C, Ott K, Sensinger K, Collins JJ, Brody JS, Getts R, Lenburg ME, Spira A. (2009) MicroRNAs as modulators of smoking-induced gene expression changes in human airway epithelium. *Proc Natl Acad Sci U S A*:106(7);2319-24. Schlesinger Y, Straussman R, Keshet I, Farkash S, et al. (2007) Polycomb-mediated

methylation on Lys27 of histone H3 pre-marks genes for de novo methylation in

squamous cell carcinoma (SCCHN). I. Carcinogen metabolism, DNA repair and cell

events in patients with oral epithelial dysplasia and predict clinical outcome in


Yook JI, Kim J. (1998) Expression of p21WAF1/CIP1 is unrelated to p53 tumour suppressor gene status in oral squamous cell carcinomas. *Oral Oncol*;34:198–203.

Young LS, Rickinson AB. (2004) Epstein-Barr virus: 40 years on. *Nature reviews*; 4:757-768.


Yook JI, Kim J. (1998) Expression of p21WAF1/CIP1 is unrelated to p53 tumour suppressor gene status in oral squamous cell carcinomas. *Oral Oncol*;34:198–203. Young LS, Rickinson AB. (2004) Epstein-Barr virus: 40 years on. *Nature reviews*; 4:757-768. Zur Hausen H. (2009) The search for infectious causes of human cancers: where and why.

Xi S, Yang M, Tao Y, Xu H, Shan J, Inchauste S, Zhang M, Mercedes L, Hong JA, Rao M,

Schrump DS. (2010) Cigarette smoke induces C/EBP-β-mediated activation of miR-31 in normal human respiratory epithelia and lung cancer cells. *PLoS One*:5;

*Virology* 392(1):1-10.

e13764.
