Apart from recruiting and directing leukocyte movement, MCP-1 also exhibits anti-tumor activity, in promoting Fas cell surface death receptor-ligand-mediated apoptosis in cultured endometrial stromal cells.19 MCP-1 is secreted by both AML blasts and stromal cells, and serum levels are increased in AML patients and appear to vary depending on AML subtype.20 Our data show that MCP-1, GM-CSF, stem cell factor and TNF-α levels produced by AML BM-MSCs are vastly different depending on oxygen levels and are much lower in hypoxic conditions similar to the sinusoidal regions of the BM. Here, TNF is linked to acute myeloid leukemia.