HSC-3 co-cultures: intact myoma, normoxia. HSC-3 cells were cocultured with gingival fibroblasts (GFs) or with fibroblasts isolated from a human tongue tumor (called CaDEC12 cells). A few caveolin-1-positive cells are seen in the upper region tumor cells (a, d). Caveolin-1-positive cells are spindle-shaped and concentrically arranged around the invading tumor islands in the lower regions (b, e). Serial sections of d & e (g & h, respectively) of the lower region also show peri-HSC-3 spindle cells positive for alpha-smooth muscle actin (αSMA). Double immunostaining with pan-cytokeratin (AE1/AE3, grey color) and caveolin-1 (brown color) in co-cultures of HSC-3 + GF (c) and HSC-3 + CaDEC12 (f) shows that the spindle-shaped cells surrounding the invading tumor islands are only caveolin-1-positive (black arrows). Some of the cells within the tumor islands are positive for both cytokeratin and caveolin-1 (c, f, red arrows).