TGFB1 and neoplasm: In vivo studies with murine mammary gland directed overexpression of MMTV-ErbB2/Neu and MMTV-TGFβ or constitutive active mutant TGFβR show that activation of TGFβ signaling pathway enhances ErbB2-induced tumor growth and metastasis to lungs, which can otherwise be a rather slow process [91].