Cancer cells can invade as a population in various cancer tissues. This phenomenon is called collective invasion, which is associated with the metastatic potential and prognosis of cancer patients. The collectiveness of cancer cells is necessary for collective invasion. However, the mechanism underlying the generation of collectiveness by cancer cells is not well known. In this study, the phenomenon of contact following, where neighboring cells move in the same direction via intercellular adhesion, was investigated. An experimental system was created to observe the two-dimensional invasion using a collagen gel overlay to study contact following in collective invasion. The role of integrin-beta 1, one of the major extracellular matrix (ECM) receptors, in contact following was examined through the experimental system. Integrin-beta 1 was localized to the intercellular site in squamous carcinoma cells. Moreover, the intercellular adhesion and contact following were suppressed by treatment of an integrin-beta 1 inhibitory antibody. ECM proteins such as laminin-332 and type-XVII collagen were also localized to the intercellular site and critical for contact following. Collectively, it was demonstrated that the activity of integrin-beta 1 and expression of ECM proteins in the intercellular site promote contact following in the collective invasion of a cancer cell population. (C) 2019 Elsevier Inc. All rights reserved.