ABSTRACT
A key question concerning the biological and medical importance of the human CEA family is whether the observed changes in expression of its members in various types of cancer are adventitious or contributory to the development of malignancy. The denomination “marker” as in “tumor marker” has the unfortunate connotation of a label rather than a contributor and this, combined with evidence that CEA and NCA expression are positively correlated with differentiation in colonocytes, has perhaps led to a perception that tumor cell CEA levels are merely passive indicators of the state of differentiation of the tumor from which they derive. A priori, it would seem unlikely that a family showing such radical changes in expression in so many different cancers, especially in view of the discovery that these molecules mediate intercellular adhesion (see below), would have nothing to do with malignancy. Elsewhere in this volume (see Chapter 10 by Jessup and Thomas), the involvement of CEA in metastasis is reviewed in detail. Although positive effects of CEA expression on metastasis might be expected to confer selective advantage on metastatic cells themselves, the observed over-expression in primary tumors raises the possibility of a direct role in the initial tumorigenic process as well.
