4NQO-Induced Rat Tongue Carcinoma: An Ultrastructural Study

The 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue carcinoma, in which the carcinogen is administered systemically in drinking water, is the most comparable animal model to the development of human oral carcinoma. This is the first study to report the ultrastructural changes in this model. The most significant changes were observed in the carcinoma cells at the invasion front and included unique modifications in the basal lamina, presence of micropinocytotic vesicles (plasmalemmal caveolae), and emergence of cytoplasmic microfilaments featuring a parallel arrangement. The microfilaments, in both appearance and organization, were consistent with contractile microfilaments. These observations may be the morphological reflection of the phenotypic modifications occurring within the carcinoma cells, approaching smooth muscle differentiation.