MST1 and neoplasm: Thus, tumor cell produced HGFL acts in an autocrine fashion to promote macrophage recruitment to the tumor via MAPK-dependent alterations to the secretome (and autonomously promote mammosphere formation), and in a paracrine fashion to elicit HGFL-RON-dependent alterations to the macrophage secretome that promote mammosphere formation of RON/HGFL expressing tumor cells.