ERBB2 and neoplasm: Therefore, the unchanged levels of blood fatty acids observed in the FASN∆/∆; PyMT mice compared with FASN+/+; PyMT mice (Supplementary Fig. 7a) and the absence of tumor formation in wild-type animals grafted with FASN-negative KRAS-, HER2-, or PyMT-expressing cells (Supplementary Fig. 7b–e) show that the observed abrogation of breast epithelium transformation is not secondary to systemic effects of FASN deletion, and the availability in blood of the product that FASN synthesizes does not rescue the transforming phenotype.