Mendelian analysis of a metastasis-prone substrain of BALB/c nude mice using a subcutaneously inoculated human tumour.

Most nude mice do not allow the formation of metastases after heterotransplantation of human malignant tumours. Here we describe a substrain of BALB/c nude mice (BALB/c/AnNCr) that reproducibly allows some human cancers to metastasize. By Mendelian analysis of hybrids between this substrain and C57BL/6J +/+ mice we found that the ability to allow a human tumour (MDA-MB-435 BAG) to express its metastatic phenotype is determined by a recessively inheritable trait in the mouse host. We are presently working to identify the genetics responsible for development of metastases. The study also includes immunohistochemical and electron microscopic analysis of the test tumour, originally assumed to be a human mammary carcinoma, but shown to possess characteristics of a malignant melanoma (1). The ultimate aim of our ongoing study is to establish a substrain of nude mice that will allow metastasis in all recipients.