The expression of dominant negative Tgfbr211 or Tgfbr2 deletion12 lead to alveolar hyperplasia in an epithelium-specific manner13 and accelerated MMTV-PyMT-induced tumor development12, while exogenous administration of TGFβ1 reversibly inhibits mammary epithelial cell proliferation14. The gene discussed is TGFB1; the disease is neoplasm.