For these reasons, we generated the first animal models for Shc1-isoform-specific knockout of the p52SHC (p52SHCKO) isoform and first rat knockout of p66SHC (p66SHCKO) isoform [19] in the SS/JrHsdMcwi (SS) genetic background, which is a well-studied rat parental background for breast cancer risk [20, 21]. This evidence concerns the gene SHC1 and breast cancer.