A DNA microarray was then performed on wild type mammary tissue, mammary tumors induced by high levels of the IGF-IR transgene (also called primary mammary tumors or PMTs) and mammary tumors that resumed growth following IGF-IR transgene downregulation that only expressed low levels of IGF-IR (also called IGF-IR-independent recurrent spindle tumors or RSTs). This evidence concerns the gene IGF1R and breast cancer.