Bone marrow stroma cells regulate TIEG1 expression in acute lymphoblastic leukemia cells: Role of TGFβ/BMP‐6 and TIEG1 in chemotherapy escape

The bone marrow microenvironment regulates early B lymphopoiesis and protects leukemia cells against chemotherapy treatment, thus the microenvironment may serve as a sanctuary site for these cells. Yet, few factors that contribute to this process are known. We have explored the role of transforming growth factor β (TGFβ) and bone morphogenetic protein‐6 (BMP‐6) and one target gene, TGFβ inducible early gene 1 (TIEG1), in the communication between stroma cells and acute lymphoblastic leukemia (ALL) cell lines and their escape from chemotherapy. Here, we have demonstrated TIEG1 expression in both normal B progenitor cells and ALL cells, which increased rapidly upon TGFβ and BMP‐6 treatment. Stimulation with TGFβ or BMP‐6, as well as overexpression of TIEG1 inhibited proliferation. Furthermore, interaction with stroma cells induced TIEG1 expression in ALL cells, inhibited their proliferation and protected the cells against chemotherapeutic treatment. Similarly, treatment with TGFβ or BMP‐6, as well as overexpression of TIEG1, protected ALL cells against chemotherapy‐induced cell death. These data suggest that TGFβ and BMP‐6 in the bone marrow microenvironment allow leukemia cells to escape therapy. Further, the data indicate that TIEG1 might be involved in mediating this effect from the microenvironment onto the leukemia cells. © 2008 Wiley‐Liss, Inc.