engleski

Lymph node B-CLL lymphocytes show the highest expression of CD52 and the lowest of CD20 compared to those from peripheral blood and bone marrow – implications for therapy?

Background: B-cell chronic lymphocytic leukemia (B-CLL) is characterized by variable clinical presentation with different involvement of various lymphoid compartments ie peripheral blood, bone marrow and lymphoid organs such as lymph nodes and spleen. Also there is a well documented intraclonal and interclonal variability of B-CLL cells in different microenvironments regarding a number of surface and intracellular molecules (for example CD38 and ZAP-70). This variable distribution of tumor mass has strong association with prognosis and a well documented influence on response to novel immunotherapeutics like rituximab and alemtuzumab. There is a well documented efficacy of rituximab in cases with with 11q deletion (associated with significant lymphadenopathy), and known resistance to alemtuzumab in pateints with bulky lymphadenopaty (>5cm). Aim of this study was to evaluate level of expression of CD20 and CD52 on B-CLL lymphocytes and intra and interclonal differences dependent on different microenvironment, ie peripheral blood, bone marrow and lymph nodes. Methods: peripheral blood, (PB), bone marrow (BM) and lymph node (LN) samples were taken by conventional techniques (venepuncture and fine needle aspiration) on the same day. The expression level of CD20 and CD52 molecules on CD19+CD5+ B-CLL cells was analyzed by flow cytometry. Results were expressed as mean fluorescence intensity (MFI) and percentage of positive cells and analyzed by paired tests. Results: we have analyzed samples taken from 12 typical B-CLL patients with median age of 70.5 years. There were 7 males and 5 females. Mean beta-2 microglobuin was 5.5mg/l, mean TTM size was 9.8 and mean TD was 0.75. There were 7, 3 and 2 patients in Binet stage A, B and C, respectively. There were 4 previously treated patients (patients were not treated 3 months before sampling) of whom one patient was previously treated with both rituximab and alemtuzumab. Among included patients there were patients with 11q deletion and with 17p deletion. Median expression level (MFI) of CD52 was 115.5, 140, and 179 for PB, BM and LN respectively (p<0.05). Median expression level (MFI) of CD20 was 4.82, 2.89 and 1.81 for PB, BM and LN respectively (p<0.05). Results were very consistent in this clinically and cytogenetically heterogenous group of B-CLL patients, with lowest expression of CD20 in LN in all patients and highest in PB in 10 out of 12 patients, and with lowest expressio! n of CD52 in PB in 10 out of 12 patients and highest in LN in 11 out of 12 patients. Conclusions: relatively unexpected results demonstrating the lowest level of expression of CD20 in lymph nodes compared to PB and BM and the highest expression of CD52 in LN compared to PB and BM is inversely related to known efficacy of agents (i.e. rituximab and alemtuzumab) targeting these molecules in these lymphoid compartments. These results indicate that other factors in selected microenvironment (beside number of molecules on cell surface) regulate sensitivity of B-CLL cells on rituximab and alemtuzumab in vivo. These results warrant further studies to indentify these factors which may evantually uncover novel therapeutic targets.

B-cell chronic lymphocytic leukemia; CD52; CD20

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