Melanocytes are highly motile cells that play an integral role in basic skin physiological processes such as wound healing and proper skin pigmentation. It has been postulated that surrounding keratinocytes contribute to melanocyte migration, but underlying mechanisms remain rather vague so far. In this study, we set out to analyze the specific potential contribution of keratinocyte components to melanocytes and melanoma cell migration-related processes. Our studies revealed that A375 human melanoma cell attachment, spreading, and migration are interestingly better supported by HaCaT keratinocyte extracellular matrix (ECM) than by self-derived A375 ECM. Moreover, HaCaT ECM caused increased integrin ␣6 expression, adhesion-mediated focal adhesion kinase phosphorylation, and focal adhesion formations. Similar effects were confirmed in human melanocytes. Furthermore, we found that keratinocyte-derived soluble factors did not appear to significantly contribute to these processes. Specific extrinsic factors that promoted melanoma migration were attributed to keratinocyte-derived laminin-332, whereas alternative ECM component such as laminin-111 and fibronectin functions appeared to have insignificant contributions. Taken together, these studies implicate extrinsic laminin-332 in promoting the high mobility property and perhaps invasiveness inherently characteristic of, and that are the menace of, melanocytes and melanomas, respectively.Melanocytes, which are present in the skin, hair, eyes, and ears, synthesize melanin via a process known as melanogenesis (1), and thus play a key role in the pigmentary system of the skin in the body. These cells are located in the bottom layer of the skin (basal epidermis), where they comprise 5-10% of the total cells. The major cells comprising the epidermis are keratinocytes, which are organized into the basal cell layer, spinous cell layer, granular cell layer, and keratinized squames (2). The keratinocytes in the basal cell layer gradually differentiate, proliferate, and migrate upward to form the primary protection of the body from the outside environment.There is a close and important functional association between melanocytes and keratinocytes. Melanocytes transfer mature melanosomes to neighboring keratinocytes, resulting in visible skin pigmentation (3) and protecting the keratinocytes from the deleterious effects of UV light (4). Therefore, melanocytes play an important role in keratinocyte functions. Reciprocally, keratinocytes mediate melanocyte functions via several pathways, including cell-cell adhesion, cell-matrix adhesion, and paracrine signaling (5). Normal melanocytes maintain cellcell adhesion with keratinocytes by expressing cell-cell adhesion proteins such as E-cadherin, desmoglein 1, and connexins (6). In turn, keratinocytes secrete many paracrine factors to melanocytes, including ␣-melanocyte-stimulating hormone (␣-MSH), 2 adrenocorticotrophic hormone, endothelin-1, -2, and -3, FGF-2, and hepatocyte growth factor, all of which regulate the proliferation and di...