Lenalidomide Abrogates the Protective Influence of Nurse-Like Cells on Primary Chronic Lymphocytic Leukemia Cells In Vitro.

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Blood (ASH Annual Meeting Abstracts) 2007 110: Abstract 3116

Lenalidomide Abrogates the Protective Influence of Nurse-Like Cells on Primary

Chronic Lymphocytic Leukemia Cells In Vitro.

Danelle F. , MD1,2, ann R. Betty, B.S.1,*, Ruzbeh Mosadeghi1,* and

J. Kipps, M.D.,Ph.D1,2

1 University of California San Diego, and s Cancer Center, La

Jolla, CA, USA and 2 Chronic Lymphocytic Leukemia Research Consortium.

Abstract

Lenalidomide (3-(4-amino-1-oxo-3H-isoindol-2-yl)piperidine-2,6-dione)) is an

agent approved for treatment of patients with del 5q myelodysplastic syndromes

and previously treated multiple myeloma. Lenalidomide has been found in early

clinical trials to have potential therapeutic activity in patients with relapsed

chronic lymphocytic leukemia (CLL). The mechanism(s) whereby this drug is active

in CLL is unknown. In particular, studies to date have not found lenalidomide to

have any direct cytotoxic activity on CLL cells in vitro. This has stimulated

speculation that this agent might adversely affect the positive influence of the

microenvironment on leukemia-cell survival. We and others have observed that

cells found in the leukemia microenvironment can support CLL-cell survival in

vitro. One such type of cells are nurse-like cells (NLC), which can

differentiate from the CD14-positive blood mononuclear cells of CLL patients

into large, round adherent cells that can attract and support CLL cell survival

in vitro for weeks, if not longer. We evaluated the effects of lenalidomide on

primary leukemia-cell survival in vitro when the CLL cells from different

patients (N=21) were cultured alone or together with NLC generated as previously

described [Tsukada Blood 2002]. We assessed the in-vitro activity of

lenalidomide on primary CLL cells from 21 patients, in duplicate in a series of

6 experiments. Lenalidomide at concentrations of 0.1µM-200µM did not

significantly impact the survival of CLL cells that were cultured alone for up

to 12 days. Analysis of cell surface markers revealed increased expression of

CD38 at 36 hours in 5/5 lenalidomide treated CLL samples compared with untreated

cells (MFIR 5.7 +/- .86 vs. 3.4 +/- .83 p=.003). We observed sustained

upregualtion of CD40 and regulation of CXCR4 in the majority of cells treated

with lenalidomide. When cultured with NLC, the survival of CLL cells was

comparable to or significantly higher than that of CLL cells cultured alone

62.4% vs. 51% (+/-3% SEM n=21 p [<] 0.0005). The addition of lenalidomide at

concentrations of 0.1µM and greater to co-cultures of NLC and CLL cells caused

specific reductions in CLL cell survival to levels similar to or lower than that

of CLL cells cultured without NLC. In the presence of NLC, lenalidomide at 1µM

reduced CLL cell viability compared to control (41.5% vs. 56% +/-4% p [<] 0.0005

paired student t test n=13). For most patients the levels of CLL cell viability

on days 4 through 8 in the co-cultures with lenalidomide was significantly lower

than those of CLL cells co-cultured with NLC in the absence of lenalidomide. As

such, this study reveals that physiologic concentrations of lenalidomide might

abrogate the protective influence of NLC on CLL cell survival in vitro and

potentially in vivo. Conceivably, those patients who have leukemia cells

displaying a high dependency on NLC for survival in vitro also might be most

likely to experience a favorable clinical response to treatment with

lenalidomide. This hypothesis will be tested in a prospective manner with a

planned clinical trial evaluating lenalidomide for treatment of CLL through the

CLL Research Consortium.

Footnotes

Disclosure: No relevant conflicts of interest to declare.