Mediates homophilic cell-cell adhesion in a Ca2+-independent manner. Also mediates heterophilic cell-cell adhesion with CADM3 and NECTIN3 in a Ca2+-independent manner. Acts as a tumor suppressor in non-small-cell lung cancer (NSCLC) cells. Interaction with CRTAM promotes natural killer (NK) cell cytotoxicity and interferon-gamma (IFN-gamma) secretion by CD8+ cells in vitro as well as NK cell-mediated rejection of tumors expressing CADM3 in vivo. May contribute to the less invasive phenotypes of lepidic growth tumor cells. In mast cells; may mediate attachment to and promote communication with nerves. CADM1; together with MITF; is essential for development and survival of mast cells in vivo. Acts as a synaptic cell adhesion molecule and plays a role in the formation of dendritic spines and in synapse assembly (By similarity). May be involved in neuronal migration; axon growth; pathfinding; and fasciculation on the axons of differentiating neurons. May play diverse roles in the spermatogenesis including in the