S14 (Thyroid Hormone Inducible Hepatic Protein) is a nuclear protein communicates the status of dietary fuels and fuel-related hormones to genes required for long-chain fatty acid synthesis. In mammary glands S14 is important for both epithelial proliferation and milk fat production. High expression of S14 in primary invasive breast cancer is predicative of recurrence. S14 also medicates the induction of lipogenesis by protestin in breast cancer cells and accelerates their growth.