Evolutionary aspects of cancer resistance.

Humans are relatively cancer resistant, as judged by the absence of cancer in two thirds of the population. The susceptibility/resistance of other mammalians varies but shows no relationship to body size. Selection for longevity and cancer resistance may occur in parallel, as indicated by the extremely long lived and cancer free mole rat species. Microenvironmental control may play a major role in the defense against potential neoplastic cells. Our work confirms that normal fibroblasts inhibit the growth of tumor cells in vitro, largely by a contact dependent mechanism. The inhibitory capacity of the fibroblast differs depending on the site of origin, and is also different between normal and cancer derived stroma cells. Preliminary gene analysis points to major differences in gene expression in between inhibitory and non-inhibitory fibroblasts.