Figure 6. Caveolin-1 mediates senescent fibroblast-induced tumorigenesis in vivo.

(A) and (B) Tumor xenografts studies in nude mice. MDA-231 cells were subcutaneously injected alone or with either hydrogen peroxide-treated wild type or caveolin-1 null MEFs into the dorsal flap of nude (nu / nu) mice. Mice were sacrificed four weeks later and tumor size measured. Representative images are shown in (A); quantification of tumor size is shown in (B). Values in (B) represent means ± SEM. *, #P<0.001.

(C) Schematic diagram summarizing the role of caveolin-1 as a key mediator of the antagonistic pleiotropic properties of cellular senescence. Anti-tumorigenic effect of caveolin-1-mediated cellular senescence: by inducing cellular senescence of cancer cells, including breast cancer epithelial cells, caveolin-1 expression inhibits cancer cell growth. Pro-tumorigenic effect of caveolin-1-mediated cellular senescence: caveolin-1 indirectly promotes tumor cell growth by inducing senescence of fibroblasts, which release secreted factors that stimulate proliferation of cancer cells.