Comparative studies between nude and scid mice on the growth and metastatic behavior of xenografted human tumors

The growth and metastatic behavior of three human tumor cell lines and a human colon carcinoma previously passagedin vivo were compared between nude mice and scid mice after xenotransplantation. The three human tumor lines included a bladder carcinoma (T24B), a melanoma (RPMI 7931) and alacZ gene-transduced breast cancer (MDA-MB-435 BAG). ThelacZ gene codes for -galactosidase, which can be stained blue with chromogenic substrate X-gal, thus allowing the highly sensitive detection and quantitative examination of human cancer metastasis in host mice. Adult (7–14 weeks) NMRI nude and C.B-17 SCID mice were inoculated with 0.5–5 × 10⁶ tumor cells s.c. Comparable take rate, latent period and growth rate of implanted tumors were observed in nude and scid mice for each of the cell lines tested. At the time of autopsy, which varied from 6 to 11 weeks after inoculation, a significantly higher incidence of spontaneous lung metastasis was discovered in scid mice (96%) than in age-matched nude mice (27%, totalP < 0.001).In vitro assays for NK cell-mediated cytotoxicity revealed no significant differences between the two strains of mice. Our results suggest that nude and scid mice are equally suitable for propagating human tumors. However, the metastatic capacity of human tumor cells appears to be better expressed in scid mice. Scid mice may therefore provide an advantageous model for the study of human tumor metastasis.