It was previously reported that cancer cells recruit BMDCs through secretion of soluble factors, including SDF-1 [24–26], VEGF [22, 27], MMP-9 [26], placental growth factor (PIGF) [22, 28], IL-1 beta [29], and granulocyte macrophage colony stimulating factor (GM-CSF) [30]. Here, PIGF is linked to cancer.