L1CAM and neoplasm: Other integrin-mediated tumor cell adhesion includes αVβ1 or αVβ3 on tumor cells with L1 cell adhesion molecular (L1CAM) on the endothelium and α4β1 on tumor cells with vascular cell adhesion molecule-1 (VCAM1) on the endothelium, further allowing CTCs to extravasate and form distant metastases (Figure 2).