Development of leiomyosarcoma of the uterus in MMTV‐CR‐1 transgenic mice

Abstract Overexpression of Cripto‐1 (CR‐1) in FVB/N mice using the MMTV‐LTR promoter results in increased mammary tumourigenesis in these female transgenic mice (MMTV‐CR‐1). Here, we characterize uterine tumours that developed in 15/76 (19.7%) of MMTV‐CR‐1 female nulliparous or multiparous mice during 24 months of observation compared with 0/33 (0%) of FVB/N normal control mice observed during the same time period ( p < 0.01). The uterine tumours collected from the MMTV‐CR‐1 mice were classified as leiomyosarcomas and found to express the CR‐1 transgene by polymerase chain reaction analysis and immunohistochemistry. Detection by western blot analysis showed higher levels of phosphorylated (P) forms of c‐src, Akt, GSK‐3β, and dephosphorylated (DP)‐β‐catenin in lysates from MMTV‐CR‐1 uterine leiomyosarcomas in comparison with lysates from normal control FVB/N uteri. Immunostaining showed increased nuclear localization of β‐catenin in the MMTV‐CR‐1 uterine leiomyosarcomas. Increased immunostaining for CR‐1 was detected in 9/13 (69.2%) cases of human leiomyosarcoma compared with staining in 3/15 (20%) human leiomyoma sections. Stronger immunostaining for P‐src, P‐Akt, P‐GSK‐3β and increased nuclear localization of β‐catenin was also seen in human leiomyosarcomas in comparison with leiomyomas. Normal human uterine smooth muscle (UtSM) cells treated with exogenous soluble rhCR‐1 showed increased levels of P‐src, P‐Akt, P‐GSK‐3β and dephosphorylated (DP)‐β‐catenin and increased proliferation ( p < 0.05) and migration ( p < 0.01) in comparison with untreated control UtSM cells. Inhibitors against c‐src, Akt or β‐catenin, individually or in combination, significantly reduced CR‐1‐induced migration. These results suggest a role for CR‐1 during uterine tumourigenesis either directly by activating c‐src and Akt and/or via cross‐talk with the canonical Wnt signalling pathway, as suggested by the increased expression of P‐GSK‐3β, DP‐β‐catenin, and increased nuclear localization of β‐catenin in human and MMTV‐CR‐1 mice leiomyosarcomas. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.