Long-live euthymic BALB/c-nu mice. II: spontaneous tumors and other pathologies

This paper is the second of a series aimed to show the main physiological and pathological characteristics of male euthymic BALB/c-nu mice, a long-live strain of BALB/c mice bred in our own Institute. The previous paired paper Piantanelli (Mech. Ageing Dev. (2001)) has been devoted to a survival study up to advanced ages highly interesting for studies on successful aging. In the present paper we report first data of a cross-sectional study on 4,15,22,28 and 34 months-old mice, dealing with tumors and other relevant pathologies. Results have shown that tumors or other pathologies can hardly be detected up to the age of 22 months. At 34 months of age about 40% of mice revealed a variety of neoplasia and other diseases are clearly detectable. These results suggest that a significant increase in longevity could be a factor increasing the risk of tumor development; thus, caution has to be paid in studies on mice utilized for long term carcinogenicity assay, where animals are sacrificed at the age of 18 months, according to the International Program. Finally, animals of the same chronological age have been subdivided in clusters according to their presumptive longevity, estimated taking advantage of the relationship between body weight and age-at-death found in the paired longitudinal study. This subdivision will be helpful in interpreting inter-individual variability of the biological parameters checked in these animals.