The role of hyaluronan and interleukin 8 in the migration of chronic lymphocytic leukemia cells within lymphoreticular tissues.

Malignant lymphocyte migration into and within lymphoreticular tissue is an important aspect of chronic lymphocytic leukemia (CLL), yet little is known about the processes involved. Our previous studies of integrin expression and function in CLL have shown that the abnormal cells are relatively nonadhesive and nonmotile on the protein ligands of these receptors. Here we show that CLL cells adhere to a non-protein ligand, hyaluronan (HA), and become motile (as assessed by both Boyden chamber migration and time-lapse video microscopy) on this ligand when stimulated with interleukin (IL) 8. The combined presence of HA and IL-8 was essential for this motility because IL-8 did not stimulate movement on other surfaces. Blocking antibodies showed that this motility is mediated by the receptor for HA-mediated motility (RHAMM), without the involvement of CD44. Moreover, confocal microscopy showed a polarized distribution of RHAMM and F-actin, but not CD44, in cells which had become motile on HA in the presence of IL-8. Immunohistochemical studies of nodes and spleen demonstrated an abundant reticular network of HA-containing fibers throughout diseased nodes and in splenic white pulp. The splenic red pulp and the luminal surface of high endothelial venules lacked HA. IL-8 was ubiquitously present in these tissues. CLL cells were shown to move spontaneously on fibroblast monolayers derived from lymphoid tissue; this movement was largely blocked by hyaluronidase or anti-RHAMM or anti-IL-8 antibodies. These studies indicate that IL-8-induced motility on HA is likely to be important for CLL cell migration through lymphoid tissue.