As an example, orthotopical implantation of mammary tumor cells in caveolin (Cav)-1 knockout mice, a model of accelerated host aging, had increased stromal content relative to those cells implanted into control microenvironments [Cav-1(+/+) versus Cav-1(−/−) age-matched young female mice] (57). The gene discussed is CAV1; the disease is breast cancer.