ESR1 and neoplasm: In vivo inhibition of microenvironmental TGFβ decreased ER+ tumor osteolytic progression and tumor burden, an effect unlikely to be due to changes in tumor cell dissemination, as treatment began 24 h post tumor inoculation after ER+ 43-4M cells had already disseminated to bone [12]; nor was the lower tumor burden upon TGFβ neutralization likely attributable to a loss of direct effects of TGFβ on tumor cell proliferation given TGFβ’s in vitro growth suppressive effects on luminal ER+ 43-4M cells, which are also consistent with anti-proliferative effects of TGFβ in bone-tropic ER- cells [22].