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Athymic-nude (nu/nu) mice and normal (nu/+) mice showed no differences in either latent period or incidence of local sarcomas or lung adenomas within 120 days after administration of 3-methylcholanthrene at birth. However, nu/nu mice were incapable of rejecting allogeneic skin grafts for the duration of the experiment. These results argue against an active role of thymus-dependent immunity as a surveillance mechanism preventing tumor development.

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A heritable propensity to develop malignant lesions is found in individuals with familial adenomatosis of the colon an rectum (ACR) and the Gardner's syndrome variant, an autosomal dominant trait. In the present study, the growth characteristics of cultured skin fibroblasts (SF) derived from normal-appearing flat skin biopsies of ACR families, representing all phenotypes, and appropriate controls were investigated. SF were obtained from stocks between the second and fifth passages and growth to confluency in Eagle's Minimal Essential Medium (EMEM) supplemented with 15% fetal calf serum (FCS). Following trypsinization, cells were replanted in EMEM supplemented with either 1% or 15% FCS at an initial density of 4 x 10(3) cells/cm2 and counted daily for five days. Normal SF representing several age groups (both sexes) and those obtained from non-afflicted individuals of ACR families grew only in 15% FCS. In contrast, SF from ACR subjects and from embryonal skin grew both in 1% and 15% FCS. SF from several clinically asymptomatic adults, children or ACR patients, grew in 1% FCS as well. Cell cultures from ACR individuals showed regions of criss-crossed arrays and multilayered pattern. These growth properties were not observed in normal cell cultures. The SF from ACR individuals did not grow in methocel, nor did they form tumors in athymic mice. These results suggest the occurrence of previously undetected biochemical alterations in SF taken from ACR genotypes.