A slight change of topic, but yes, most mice used in cancer research are predisposed to get cancer:
http://emice.nci.nih.gov/aam/mouse/carcinogen-induced-and-spontaneous-mouse-models
And there definitely are limitations to murine (mouse) cancer models, but they are still very necessary in the study of any new treatment:
http://vectorblog.org/2012/05/the-problem-with-modeling-metastatic-cancers-is-it-the-mouses-fault/