**5. Epithelial cell adhesion molecule (EpCAM)**

Epithelial cell adhesion molecule (EpCAM) is a Ca2+ independent, type I transmembrane glycoprotein with a molecular weight of 40 kDa [48] located on

**13**

*Stem Cell Markers in Colon Cancer*

*DOI: http://dx.doi.org/10.5772/intechopen.84315*

tively, and 242 amino acids [48, 51].

entiation and progression was also confirmed [50].

parenchyma does not express EpCAM [54].

patients was difficult to establish [58].

anti-EpCAM antibodies [59, 60].

**6. CD166 or ALCAM**

breast cancers [63].

them to form a solid metastatic mass [59].

the basolateral surface of epithelial tissues [49]. EpCAM expression was not seen in mesenchymal or lymphoid tissues [50]. EpCAM presents with two main domains: EpICD, an intracellular domain, and EpEx, an extracellular domain of 26, respec-

EpCAM was found to be overexpressed in various digestive (stomach, colon, pancreas, and esophagus) and non-digestive (prostate, ovary, breast) cancers [49]. EpCAM is principally involved in adhesion processes, but its role in cellular differ-

A high percentage of colon cancer cases (79–99.7%) is characterized by overexpression of EpCAM molecule at tumor level [52, 53]. Moreover, EpCAM was found to be expressed also in liver metastases secondary to colon cancer, a situation that confirmed its involvement in cancer progression as well [50, 52]. Normal liver

Overexpression of EpCAM in colon cancer correlates in some studies with advanced stages of the disease [50, 55, 56], with a higher risk of metastases [55, 56], with poor differentiated (G3) patterns [54–57], with the number of lymph nodes involved (N) [48, 54], and with perilymphatic (L) and perivenous (V) invasion [54, 57] but also with worse overall survival [55, 56]. The results were not, however, confirmed by other study groups, so the predictive value of EpCAM in colon cancer

EpCAM is also involved in epithelial-mesenchymal transition (EMT) process [56]. During EMT, neoplastic cell detaches from the primary tumor (due to loss of EpCAM expression and less intercellular adhesions) to enter the lymphatic and vascular system and initiate the carcinogenesis process [56]. Detached cells, also called circulating tumor cells (CTCs), can be identified from blood samples through "liquid biopsy" technique that is based also on EpCAM detection using specific

In order to achieve distant metastasis formation, circulating tumor cells have to undergo a second, reversed process called mesenchymal-epithelial transition (MET) during which an upregulation of EpCAM expression at the cellular surface has been observed [59]. Secondary to it, cells acquire adhesion properties that allow

Despite constant research in the field of cancer stem cell biomarkers in colon cancer, specific factors or local conditions that initiate and promote EMT or MET

CD166, also called activated leukocyte cell adhesion molecule (ALCAM), is a 110 kDa, transmembrane type-1 glycoprotein used for colon cancer stem cell (CCSC) identification [3, 61, 62]. Providing the leukocyte receptor function, CD166 expression was identified in both normal and colonic tissue, in the latter cases the expression being superior [3, 63]. CD166 expression in colon cancer varies between 58.6 and 76% [64, 65] and is higher in colonic adenomas [66], suggesting its involvement in colon carcinogenesis. Due to its adhesive properties, CD166 is considered to be involved in colon cancer tumor growth [62]. CD166 expression was also confirmed in pancreatic, esophageal and gastric, prostate, melanoma, and

Expression of CD166 in colon cancer was studied in relation to tumor stage [61, 64, 65], lymph node involvement [61, 64], or degree of cellular differentiation (G) [61], but even if overexpression was confirmed, no statistic significant correlation was found. Regarding overall survival of colon cancer patients,

are insufficiently known, and further research have to be performed.
