Expression of laminin-5 in ameloblastomas and human fetal teeth

Extracellular matrix proteins have been shown to play important roles in th e cell migration and differentiation in both normal and pathological condit ions. In the present study, we used immunohistochemistry and in situ hybrid ization to determine the distribution of laminin-5 in ameloblastomas and de veloping human teeth. In ameloblastomas, the immunoreaction for the laminin -5 gamma 2 chain was confined to the tumor cells of the peripheral area. Th e staining reaction was variable, being mostly weak and fragmented in the b asement membrane structures surrounding the neoplastic islands. Some periph eral epithelial cells and some invading small ameloblastoma cell islands sh owed intense intracellular staining for the gamma 2 chain. Tumor cells in t he proliferating areas of ameloblastomas expressed gamma 2 chain mRNA. The laminin-5 gamma 2 chain was located beneath the dental lamina and in the ou ter, but not in the inner, enamel epithelium of the developing teeth. Durin g the early hard tissue apposition stage, intense staining for the gamma 2 chain was confined to ameloblasts, which also gave a strong signal for gamm a 2 chain mRNA. These results suggest that laminin-5 may contribute to the infiltrative and progressive growing potential of ameloblastomas. During hu man tooth development, however, laminin-5 may participate in the terminal d ifferentiation of ameloblasts and in enamel matrix formation.