Constitutive expression of leukemia inhibitory factor RNA by human bone marrow stromal cells and modulation by IL-1, TNF-alpha, and TGF-beta.

Recent in vitro studies indicate that bone marrow mesenchymal elements, residing in close proximity to hematopoietic cell populations, elaborate a network of cytokines that are, at least partially, responsible for modulating the growth and maturation of the latter compartment. Leukemia inhibitory factor (LIF), a molecule with both positive and negative regulatory activities, has been implicated in murine embryogenesis and hematopoiesis. We demonstrate that cultured normal human bone marrow stromal cells constitutively express LIF message. Further, exposure of these cells to other hematopoietic modulators including interleukin 1 alpha (IL-1 alpha), interleukin 1 beta (IL-1 beta), transforming growth factor-beta (TGF-beta), and tumor necrosis factor-alpha (TNF-alpha) (but not interferon-alpha [IFN alpha]) increases the level of LIF RNA. Interestingly, cultured stromal cells derived from three of four patients with chronic myelogenous leukemia showed enhanced LIF expression. These observations suggest that LIF may participate, either alone or through interaction with other cytokines, in the bone marrow microenvironment-mediated influence on both normal and malignant hematopoietic processes.