As a conserved actin-regulating
protein, CAP (
adenylyl Cyclase-Associated
Protein) functions to facilitate the rearrangement of the actin cytoskeleton. The ubiquitously expressed
isoform CAP1 drives mammalian cell migration, and accordingly, most studies on the involvement of
CAP1 in human
cancers have largely been based on the rationale that up-regulated
CAP1 will stimulate
cancer cell migration and invasiveness. While findings from some studies reported so far support this case, lines of evidence largely from our recent studies point to a more complex and profound role for
CAP1 in the invasiveness of
cancer cells, where the potential activation of cell adhesion signaling is believed to play a key role. Moreover,
CAP1 was also found to control proliferation in
breast cancer cells, through the regulation of ERK (External signal-Regulated
Kinase). Alterations in the activities of FAK (
Focal Adhesion Kinase) and ERK from
CAP1 depletion that are consistent to the opposite adhesion and proliferation phenotypes were detected in the metastatic and non-metastatic
breast cancer cells. In this review, we begin with the overview of the literature on CAP, by highlighting the molecular functions of mammalian
CAP1 in regulating the actin cytoskeleton and cell adhesion. We will next discuss the role of the FAK/ERK axis, and possibly Rap1, in mediating
CAP1 signals to control
breast cancer cell adhesion, invasiveness, and proliferation, largely based on our latest findings. Finally, we will discuss the relevance of these novel mechanistic insights to ultimately realizing the translational potential of
CAP1 in targeted
therapeutics for
breast cancer.