Expression of an adhesion molecule and homing in B-cell chronic lymphocytic leukaemia: I. Application of the HEV-binding assay to a clinical series

CD44: physiological expression of distinct isoforms as evidence for organ-specific metastasis formation

Continuous progress has been achieved during recent decades in the therapy of metastasizing malignancies by improving chemotherapeutic strategies and new approaches in radiation therapy. Genetic manipulation of tumor cells and of the tumor fighting immune system is hoped to add significant contributions to curative interventions in disseminated tumors. That we are still far from eradicating death by malignant growth is due ultimately to our limited understanding of the cascade of events resulting in metastasis formation, which until recently was believed to rely on multiple rounds of mutation and selection processes. This implies an individually specific history of each metastatic tumor, which would rule out uniform diagnostic and therapeutic concepts. When it was noted in a rat tumor model that the transfer of cDNA of a single gene, a CD44 variant isoform (CD44v) covering the exons v4-v7, sufficed to initiate metastasis formation of a locally growing tumor, hope was created that a "metastogene" may have been identified. Although the idea of CD44v expression as a unifying concept for tumor progression was not sustained, the discovery of CD44v-initiated metastatic spread allowed a conceptually new hypothesis on tumor progression as a consequence of the reactivation of genetic programs of ontogeny, stem cell differentiation, and/or lymphocyte activation. Since distinct CD44 isoforms play an important role in these processes, unraveling the functions of this family of molecules can indeed provide a cornerstone in the understanding of tumor progression. This article summarizes briefly the present knowledge on known functions of CD44 isoforms with particular focus on parallels between physiological programs and tumor progression.

Changes in adhesion molecule expression and function in B-cell chronic lymphocytic leukaemia after in vitro interferon-alpha stimulation

Peripheral blood mononuclear cells (PBMCs) from 10 B-CLL patients were investigated after 24 hours of in vitro interferon-alpha (IFN-alpha) stimulation. The constitutional expression of the L-selectins (LECAM-1), LFA-1/CD11a, VLA alpha-4/CDw49d and ICAM-1/CD54 adhesion molecules was detected, and changes in their density after IFN-alpha stimulation were compared to results obtained by the high endothelial venule (HEV)-binding assay and a carbohydrate (phosphonomannan core polysaccharide: PPME and fucoidin) immobilization test. The LECAM-1 and ICAM-1 molecules were expressed on the great majority of CLL cells, while the LFA-1 and VLA-4 alpha-chains were expressed by only a small number of cells. Statistically significant changes (p < 0.001) were observed in LECAM-1 antigen density (changes in mean cell fluorescence), as well as in functional tests (HEV-, PPME- and fucoidin-binding; p < 0.01) after in vitro IFN-alpha stimulation. Based on a prior study (Jewell et al., Leukemia 1992: 6: 400-404) and on the present findings, not only an increased expression but also an enhanced function of the L-selectins seem to be well substantiated after IFN-alpha stimulation, which may explain the therapeutic effect of IFN-alpha in reducing the accumulation of leukaemic B cells in the blood. The remarkably high expression of ICAM-1 in this series necessitates further studies to clarify the exact expression rate and role of this molecule.

Expression of an adhesion molecule and homing in B-cell chronic lymphocytic leukaemia: II. L-selectin expression mediated cell adhesion revealed by immobilized analogue carbohydrates in B-cell chronic lymphocytic leukaemia and monoclonal lymphocytosis of undetermined significance

The L-selectin mediated adhesion of freshly isolated peripheral blood mononuclear cells (PBMCs) to phosphonomonoester core polysaccharide (PPME) and fucoidin derivatized gels was investigated in seven cases of monoclonal lymphocytosis of undetermined significance (B-MLUS) and 12 cases of chronic lymphocytic leukaemia: B-CLL, patients with peripheral lymphocytosis (LY-patients), lymph node enlargement (LN-patients) and splenomegaly (SM-patients). PBMCs isolated from the peripheral blood of 10 healthy donors served as controls. The binding to PPME and fucoidin correlated well (n = 19, P = 0.01). Adhesion of PBMCs from B-MLUS and B-CLL showed a greater variability than controls. A higher number of cells, on average, bound to PPME and fucoidin derivatized polyacrylamide gels in B-MLUS than in B-CLL. However, the differences observed were not statistically significant. In four cases with B-CLL, the stimulatory effect of interferon-alpha on the function of L-selectin and some other accessory molecules was also studied. The increased binding of PBMCs to immobilized analogue molecules (PPME, fucoidin) and to high endothelial venules (HEVs) in the in vitro HEV-binding assay supports the notion that interferon-alpha not only increases the expression of the adhesion molecules, but also results in an enhanced adhesive function.