Enhancement of natural killer cell effector functions against selected lymphoma and leukemia cell lines by dasatinib

Abstract

As NK cell immunotherapy is still poorly successful, combinations with drugs enhancing NK cell activity are of major interest. NK large granular lymphocyte expansions associated with improved survival have been described under monotherapy with the Bcr-Abl/Src inhibitor dasatinib, which inhibits NK cell functions in vitro. As Src kinases play a major role in inhibitory and activating signaling pathways of NK cells, both outcomes appear plausible. To clarify these contradictory observations and potentially enable the use of dasatinib as adjuvant, we analyzed how clinically relevant doses promote NK cell effector functions. Polyclonal human NK cells were studied ex vivo. Functional outcomes assessed included conjugate formation, calcium flux, receptor regulation, cytokine production, degranulation, cytotoxicity, apoptosis induction and signal transduction. While dasatinib inhibits NK cell effector functions during functional assays, 24 hr pretreatment of NK cells followed by washout of dasatinib, led to dose-dependent enhancement of cytokine production, degranulation marker expression and cytotoxicity against selected lymphoma and leukemia cell lines. Mechanistically, this was neither due to an altered viability of NK cells nor increased NKG2D, LFA-1 or conjugate formation with target cells. Receptor proximal signaling events were inhibited. However, a slight time dependent enhancement of Vav phosphorylation was observed under certain circumstances. The shift in Vav phosphorylation level may be one major mechanism for NK cell activity enhancement induced by dasatinib. Our findings argue for a careful timing and dosing of dasatinib application during leukemia/lymphoma treatment to enhance NK cell immunotherapeutic efforts.Increasing evidence suggests that natural killer (NK) cell activity is essential for leukemia and lymphoma elimination. However, initial trials infusing autologous NK cells did not show significant clinical effects. Pharmacotherapeutical approaches to enhance NK cell activity in vivo might thus be the better option. This could potentially be achieved by fast and short-acting tyrosine kinase inhibitors (TKIs) such as the Bcr-Abl/Src inhibitor dasatinib (SprycelV R , Bristol-MyersSquibb). These drugs target specific molecular changes responsible for lymphoma and leukemia, but have also demonstrated modulatory effects on the immunological microenvironment, which is caused by the tyrosine kinase-dependent activation and inhibition of signal transduction pathways in different immune cell subsets. 1,2 Dasatinib has been shown to suppress NK cell cytotoxicity in vitro and in mouse models in vivo. [3][4][5] In contrast, about one third of dasatinib-treated patients with chronic myeloid leukemia or Philadelphia Chromosome positive acute lymphocytic leukemia display oligoclonal NK or CD8 þ T large granular lymphocyte (LGL) expansions of unknown origin which are associated with enhanced leukemic control and sustained therapeutic responses. 6-9 These contradictory findings may be due to the complicated balance...

Dasatinib promotes Th1-type responses in granzyme B expressing T-cells

“…The results, however, are still controversial as recently reviewed by us 29 . In vitro studies have pointed out that the effects on the immune cells are merely suppressive or inhibitory, 19 , 20 , 30 - 38 whereas we and others have reported opposite immunostimulatory effects in vivo 22 , 23 , 25 , 27 , 37 , 39 - 43 . The results presented in this paper support the immunostimulatory role of dasatinib and show that dasatinib therapy not only increases the amount of cytotoxic memory GrB+CD8+ T-cells, but also increases the amount of highly active GrB+CD4+ T-cells in opposite to the other TKIs (imatinib, nilotinib).…”

Nilotinib combined with interleukin-2 mediates antitumor and immunological effects in a B16 melanoma model

“…In our model, oral application may have led to a more physiologically relevant plasma concentration of nilotinib. It is notable that Hassold et al (18) found that dasatinib inhibited NK cell function during functional assays but was even able to enhance cytokine secretion and cytotoxicity after a 24-h wash-out period of dasatinib.…”

Large granular lymphocytosis during dasatinib therapy

“…18 When NK cells were pretreated for 24 h and the functional assays were performed after dasatinib was washed out, an amplification of cytokine production, degranulation, and partial kill rates against different target cell lines were observed. 30 Another possible hypothesis to account for the favorable responses is that dasatinib has potential to reduce the number of CD4 + CD25 + FOXP3 + regulatory T cells (Tregs) in both PB and BM, which are negatively regulating other immune cells, and that this reduction of Tregs were more substantially observed in LGL + patients as compared with LGLpatients. 15,31 Third, in LGL + patients the level of IP-10, IL-6, MIG, and IL-2R were increased, and these cytokines/chemokines could contribute to improved therapeutic responses because they direct the chemotaxis of monocytes, T cells, NK cells, and dendritic cells.…”