SNAI1 and neoplasm: As previously shown5, the reduced tumor growth was not due to impaired development of the mammary gland, as the mammary epithelium in 4 week and 5 week old MMTV-Cre, Snail1fl/fl females (SNAIL1 KO) was not different than the epithelium of age-matched wild type females (WT) (Fig S1F with an example shown in Fig S1G) as assessed by whole mount staining.