This suggests that while free TGF-β1 and exosomal TGF-β1 might play parallel roles in driving tumor metastasis, only exosomal TGF-β1 can significantly drive pulmonary vascular niche remodeling at lower dosages, eventually bolstering the extravasation and colonization of TNBC cells in the lungs. The gene discussed is TGFB1; the disease is neoplasm.