Cancer stem cells in colorectal cancer

Abstract

Colorectal cancer is the second most common cause of cancer death in the Western world. Due to the high prevalence of colorectal cancer and precancerous lesions, many colonoscopies, and the resulting wide availability of tissue samples, extensive knowledge is available on the stepwise process that leads to colorectal cancer. Most colorectal cancers develop from slowly growing non-invasive adenomas that take many years to grow from a single mutant crypt to an adenoma that can reach several centimeters in size before acquiring invasive characteristics. In this chapter we will discuss some of the early histopathological events in the development of colorectal cancer and try to reconcile these data with the concept of the tumor-initiating or cancer stem cell. We will show that there are many similarities between the mechanism of stem cell expansion during intestinal growth and repair and deregulated clonal expansion of stem cells in an adenoma. We argue that it is important to realize the fact that most known genetic alterations in colorectal cancer development are involved in adenoma formation and are therefore involved in clonal growth and not invasiveness. It would therefore be helpful to distinguish adenoma stem cells from carcinoma stem cells. We will then discuss the available data on the isolation and behavior of colorectal cancer stem cells. © Springer Science+Business Media, LLC 2009. All rights reserved.