Volumen: 19 # Number : 3
Publication Date : Septiembre - Diciembre Year: 2015
Chronic Lymphocytic Leukemia (CLL): effect of the Syk
kinase-inhibitors, Fostamatinib (R406) and Entospletinib
(GS-9973), on T cell function and rituximab activity.
Authors: Colado A; Almejún M; Podaza E; Risnik D;
Fernandez Grecco H; Cabrejo M; Cranco S; Burgos RA;
Sánchez Ávalos JC; Bezares FR; Giordano M;
Gamberale R; Borge M
Abstract: Leukemic cells from chronic lymphocytic leukemia
(CLL) patients proliferate within lymphoid tissues
in particular areas called proliferation centers,
where they are in close contact with non-leukemic
cells including activated CD4+ T cells, stroma and
myeloid cells(1, 2). There, CLL cell proliferation,
survival and resistance to cytotoxic agents is
driven by molecules such as CD40L, expressed by
activated T cells(3), the chemokines CCL19, CCL21
and CXCL12 secreted by stromal and myeloid
cells(4,5), and stimulation throw the B-cell antigenic
receptor (BCR)(6) favoring disease progression. At
the present CLL is an incurable disease. Current
therapies are effective in inducing initial remission in
most patients but they are not curative and relapse is
inevitable(7). In the past few years several inhibitors
targeting kinases involved in the BCR-signaling
have been developed, such as the Syk inhibitors R406 and GS-9973, the Btk inhibitor ibrutinib and
the PI3Kδ inhibitor idelalisib. Results obtained in
clinical trials with these agents have generated
great excitement because of their clinical efficacy
and excellent tolerability(7). We(8) and others(9-11)
have recently reported that BCR-associated kinases
inhibitors have immunomodulatory effects on the
tumor microenvironment from CLL patients. Thus,
we found that ibrutinib impaired the phagocytosis
of rituximab-coated leukemic cells from CLL
patients by human macrophages(8) and others found
that ibrutinib inhibits the activation of Th2 cells
after TCR stimulation(12), reducing the signals that
drive leukemic cell expansion. Here, we aimed to
evaluate the effect of R406 and GS-9973 on:
1) the physiology of CD4+ T from CLL patients and
2) macrophage mediated phagocytosis of rituximabcoated
CLL cells. We first asked whether R406 and
GS-9973 were able to inhibit T cell activation and
proliferation. We used clinically relevant doses of
the drugs and confirmed that these doses (between
0.1 and 5 μM) did not induce T cell apoptosis
(not shown). In order to induce T cell activation,
peripheral blood mononuclear cells from CLL
patients were cultured in the presence of anti-CD3
antibodies with R406, GS-9973 or the vehicle of the drugs as a control (DMSO). We found that both
inhibitors impaired the expression of the activation
markers CD25, CD69 and CD40L on CD4+ T cells,
evaluated by flow cytometry at 24 hs (p˂0.05)
and the T-cell proliferation evaluated by the CFSE
dilution assay at 5 days (p˂0.05). We also observed,
by using the Transwell system assay, that both
drugs inhibited T cell migration towards CCL19
and CCL21 (p˂0.05), key molecules involved in
T cell homing to lymph nodes. Finally, we found
that R406 and GS-9973 inhibited macrophagemediated
phagocytosis of CLL cells coated with the
anti-CD20 antibody rituximab as evaluated by flow
cytometry (p˂0.05).
Our results suggest that R406 and GS-9973 affect
the tumor microenvironment, by inhibiting CD4+
T cell activation and thus reducing the supportive
signals given to the malignant clone. Nevertheless,
these results also suggest that in patients treated for
long periods with these agents, the T cell-mediated
immune response might be affected. We also
found that both R406 or GS-9973 interfere with
the macrophage-mediated anti-tumor activity of
rituximab suggesting that the sequential and not the
concurrent administration might enhance their antitumor
activity in vivo and improve CLL therapy.
Key words: Chronic Lymphocytic Leukemia,
Syk,
GS-9973,
R406,
Entospletinib,
Fostamatinib,
kinase inhibitors,
BCR,
rituximab.
Pages :
|
