Experimental models for carcinogenesis in the house musk shrew, Suncus murinus, Insectivora

Animal carcinogenicity studies have mainly been performed on rodents. From the phylogenetic point of view, animals closer to humans must be included in these studies. Insectivora are considered to be the most primitive placental mammals and much closer to the early primates than rodents. Among the insectivora, the house musk shrew (Suncus murinus, family Soracidae), has been bred under laboratory condition. This animal is small having a short life span, and a comparatively low incidence of spontaneous tumor provides a useful animal model for tumor induction studies. We have examined the carcinogenicity of several chemicals known to produce tumors in rodents and found shrews, in general, to be sensitive to these chemicals but often showed different targets compared to rodents, and some chemicals tested were demonstrated not to be carcinogenic. Here we describe the carcinogenic studies performed in our laboratory and review other works including the occurrence of spontaneous tumors in shrews. Shrew carcinogenesis may fill up the gap of knowledge existing between the rodents and human beings.