Fig. 1. Epithelial tumors stimulated by senescent human fibroblasts progress to full malignancy. (A) (i and ii) Morphology (40xmagnification), and (iii and iv) cytokeratin (red) and vimentin (green) immunostaining (400xmagnification), of SCp2-P (i and iii) and SCp2-T (ii and iv) cells in 3D Matrigel culture. (B) Invasion and migration of SCp2-P, SCp2-T and MDA-MB-231 (positive control) cells through basement membrane components (Matrigel) in Boyden chamber assays. Error bars indicate the s.e.m. from three fields. (C) Tumorigenicity of SCp2-T cells injected alone (solid black lines) into immunocompromised mice. Tumor cells were injected and tumor size was measured at the indicated intervals after injection. Tumors formed by SCp2-P cells co-injected with senescent fibroblasts (gray lines) is shown for comparison (Krtolica et al., 2001).