chapter  30
Biologically targeted agents in head and neck cancers
ByKevin J. Harrington, Magnus T. Dillon
Pages 16

INTRODUCTION Cancer is a genetic disease that develops when the information in cellular DNA is corrupted or wrongly decoded. This leads to altered patterns of gene expression and derangement of normal protein function. Simply stated, genetic changes leading to cancer mediate two general effects: (i) overactivity of genes that stimulate cell growth, survival and spread; and (ii)  underactivity of genes that repress these processes. Through these changes, cancer cells acquire properties that allow them to grow in an uncontrolled fashion, invade adjacent normal tissues, recruit their own blood supply, avoid immune detection and destruction, spread to distant sites and develop resistance to anticancer treatments. By understanding these processes, we have an opportunity to design and implement new classes of so-called targeted therapies that will exploit the fundamental biological differences between malignant and normal cells.