Description
In the marrow and lymphatic tissues, chronic lymphocytic leukemia (CLL) cells interact with accessory cells that constitute the leukemia microenvironment. In lymphatic tissues, CLL cells are interspersed with CD68+ nurselike cells (NLC) and T cells. However, the mechanism regulating co-localization of CLL cells and these accessory cells are largely unknown. To dissect the molecular cross-talk between CLL and NLC, we profiled the gene expression of CD19-purified CLL cells before and after co-culture with NLC. NLC co-culture induced high-level expression of B cell maturation antigen (BCMA) and two chemoattractants (CCL3, CCL4) by CLL cells. Supernatants from CLL-NLC co-cultures revealed high CCL3/CCL4 protein levels. B cell receptor triggering also induced a robust induction of CCL3 and CCL4 expression by CLL cells, which was almost completely abrogated by a specific Syc inhibitor, R406. High CCL3 and CCL4 plasma levels in CLL patients suggest that activation of this pathway plays a role in vivo. These studies reveal a novel mechanism of cross-talk between CLL cells and their microenvironment, namely the secretion of two T cell chemokines by CLL-NLC interaction and in response to BCR stimulation. Through these chemokines, CLL cells can recruit accessory cells, and thereby actively create a microenvironment that favors their growth and survival.