To further understand the role of METCAM in these processes, it is essential to diligently identify the cofactors and the METCAM-cognate heterophilic ligand(s), which modulate the biological functions of METCAM. The endeavor in this direction appears to be promising from our preliminary attempts that we may have successfully found a possible candidate of METCAM's heterophilic ligand in METCAM-expressing human prostate cancer cells [7]. This evidence concerns the gene MCAM and prostate cancer.