Preface

Nasopharyngeal carcinoma (NPC) is different from other pharyngeal cancers because it has a higher prevalence rate among populations living in South-Eastern Asia. The development of NPC is complex and could be induced by many factors, such as genetic susceptibility, Epstein-Barr virus infection, and environmental exposure to carcinogens. Patients with early-stage cancer have the best chance for long-term survival; therefore, early detection is crucial to the successful treatment of cancer. The sensitivity of magnetic resonance imaging or computer tomography for the detection of cancer is extremely high, but because of the small areas of abnormality, early-stage cancer is frequently not detected on these images. Although NPC is extremely radiosensitive, patients also experience spreading to the lymph node and distant metastasis, which makes the disease difficult to control and results in poor prognosis. Radiation can also damage the hypothalamic-pituitary, the thyroid gland, and the ear, which can result in neuro-endocrine abnormalities and ear-related complications after radiotherapy. Improving NPC detection and diagnosis, developing new cancer therapies, and designing better strategies for NPC are all important practical efforts.

The aim of this book is to provide an overview of the etiologic factors associated with NPC development, to learn more about the effects of radiotherapy and chemotherapy in NPC patients, to provide vital tools for the diagnosis and detection of NPC, and to understand the molecular mechanism of carcinogenesis, which contributes to the development of targeted treatment for NPC.

As the editor, I would like to thank the authors for the high quality of their chapters and for accepting the peer review procedure established for the manual. Finally, I would especially like to thank Oliver Kurelic of the InTech-Open Access Publisher for enabling this project to be realized. I also acknowledge the efforts of the entire staff of the Press who contributed to the editing and production process. I sincerely hope that this book is able to provide valuable advice on professional pursuits.

> **Shih-Shun Chen**  Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taiwan

**1** 

**Epigenetics of Nasopharyngeal Carcinoma** 

*2Dept. Radiation Oncology, Eye Ear Nose & Throat Hospital of Fudan University* 

Cancer has been previously viewed as a disease exclusively driven by genetic changes, including mutations in tumor suppressor genes and oncogenes, and chromosomal abnormalities. However, recent data have demonstrated that the complexity of human carcinogenesis cannot be accounted for by only genetic machineries, but also involves extensive epigenetic abnormalities. The term "epigenetics" refers to the study of heritable changes in gene regulation that do not involve a change in the DNA sequence or the sequence of the proteins associated with DNA (Egger et al. 2004). Epigenetic machineries plays a fundamental role in several biological processes, such as embryogenesis, imprinting, and X chromosome inactivation, and in disease states such as cancer. Several mechanisms were included in the epigenetic machinery, the most studied of which are DNA methylation; histone modifications; and small, noncoding RNAs (Kargul and Laurent 2009; Jeltsch and Fischle 2011). The molecular mechanisms underlie the epigenetic changes in cancer cells are complicate and only began to be elucidated. The best understood component among which is the transcriptional repression of a growing list of tumor suppressor and candidate tumor suppressor genes (Jones and Laird 1999; Esteller 2007). This suppression is associated with abnormal methylation of DNA at certain CpG islands that often lie in the

Nasopharyngeal carcinoma (NPC) is a unique head and neck cancer with remarkably distinctive ethnic and geographic distribution among the world. The three major etiologic factors of NPC were well defined as genetic susceptibility, environmental factors and latent infection of the Epstein-Barr Virus (EBV) (Tao and Chan 2007; Lo, To, and Huang 2004). During the passing decade, much attention has been paid to the role of epigenetic alternations occurred in the procedure of tumorigenesis of NPC (Li, Shu, et al. 2011; Tao and

In this chapter, we will first describe the general mechanisms through which the epigenetic alternations in cancer, then focus on the epigenetic alterations taking place in NPC, with an

**1. Introduction** 

Chan 2007).

emphasis on DNA methylation.

promoter regions of these genes (Esteller 2006, 2007).

Zhe Zhang1, Fu Chen2, Hai Kuang3 and Guangwu Huang1

*1Dept.Otolaryngology-Head & Neck Surgery,* 

*Guangxi Medical University* 

*P.R. China* 

*First Affiliated Hospital of Guangxi Medical University* 

*3Dept. Oral & Maxillofacial Surgery, College of Stomatology,* 
