2.51 CD38, CD44 and β1 Integrins - CD49d, CD49c and CD29 in Different Microenvironment Have Different Pattern of Expression and Relationship to Survival

Abstract

Background: B-cell chronic lymphocytic leukemia (B-CLL) is characterized by variable clinical presentations with different involvement of various lymphoid compartments, including peripheral blood, bone marrow and lymphoid organs such as lymph nodes and spleen. This variable distribution of tumor mass has strong association with prognosis. There is also well documented intraclonal and interclonal variability in B-CLL cells within different microenvironments regarding a number of surface and intracellular molecules (including molecules with adhesion properties, for example CD38). Aims: 1) to evaluate in peripheral blood (PB), bone marrow (BM) and lymph nodes (LN) the pattern of expression of receptors with known adhesion properties and their influence on survival (notably CD38 and CD49d), and to identify adhesion molecules that reportedly co-localize with them forming macromolecular complexes (CD38, CD49d, CD44 and MMP9); 2) to evaluate the mutual relationship between these patterns and 3) to assess their relation to other clinical parameters, including survival. Methods: peripheral blood, bone marrow and lymph node samples were taken by conventional techniques (venepuncture and fine needle aspiration) on the same day. The expression levels of CD38, CD49d, CD49c, CD29 and CD44 on B-CLL cells were analyzed by flow cytometry. Results were expressed as ratio of mean fluorescence intensity (MFI) of specific antibody and negative control (MFI-R) and percentage of positive cells and analyzed by paired tests. Differences between compartments were also quantified by logarithmic ratios of MFI. Results: We analyzed samples taken from 33 typical B-CLL patients with median age of 65 years. There were 18 males and 15 females. Mean TTM size was 10.4 and mean TD was 0.62. There were 11, 14 and 8 patients in Binet stages A, B and C, respectively. Median follow-up of patients was 48 months and maximum 91 months. There was a significantly higher expression of CD38 in LN compared to BM and PB (p 0.05), CD44 expression was lower in LN compared to PB (p 0.05) and CD44v4 higher in LN than in PB and BM (p 0.05). For CD29, CD49d and CD49c there was no significant differences between compartments. We then analyzed statistically significant correlations between these receptors within each lymphoid compartment. In PB correlation was very high between CD29 and CD49d, high between CD38 and CD49d, CD38 and CD29, and CD49d and CD49c, and moderate between CD49c and CD29, CD49c and CD38 (p 0.05). There was a moderate correlation between CD44 and CD29, and low correlation between CD44 and CD49d, and CD44v4 and CD49c (p 0.05). In BM we observed the same pattern of correlations, although to a lesser degree, between CD29, CD49c, CD49d and CD38, and CD44 and CD29 (p 0.05). However, CD44v4 showed moderate correlation with CD44, and low correlation with CD49c, CD49d and CD29 (p 0.05). In LN as in BM there was the same pattern of correlations between CD29, CD49c, CD49d and CD38, and CD44 and CD29 (p 0.05). Higher CD38 expression in all lymphoid compartments, even in this small group of patients, showed a relationship with shorter survival (p 0.05). However, patients with higher expression of CD49d in BM and LN than in PB showed superior survival compared to patients with the opposite pattern of expression (p 0.05). Conclusions: There is a correlation of expression levels between analyzed molecules, although lower than between CD29 and CD49d, which form an obligate heterodimer. Also, these molecules show different level and pattern of expression between lymphoid compartments and show different relationships with survival. These results call into question the extent to which these molecules form macromolecular complex as opposed to standalone molecules, and determining the biological relevance of this putative macromolecular complex warrants further studies.