Level of Rap1 activity affects invasiveness and tumorigenic potential of T4-2 cells. A, invasiveness of T4-vector, T4-DA-Rap1, and T4-DN-Rap1 cells was examined using Matrigel-coated transwell filters. Quantification at 48 h after plating. B, the transfectants were s.c. injected into nude mice to examine tumorigenic potential. Tumor size measured at 8 wks after injection and mice bearing tumors larger than 10 mm3 were scored. C, histology of tumors derived from T4-vector and T4-DA-Rap1 cells.