We further suggested that the one most likely reason was that the different co-factors present in the different cancer cell lines may modulate the role of huMETCAM/MUC18 in these processes via homophilic interactions with endothelial cells and immune cells and via heterophilic interactions with other cells and also with the extra-cellular matrix in the tumor microenvironment [10,15,41]. The gene discussed is MCAM; the disease is cancer.