Farnesyltransferase inhibition: a novel method of immunomodulation

Abstract

Farnesyltransferase inhibitors (FTIs) are anticancer compounds that inhibit Ras GTPases. Since Ras GTPases play key roles in T cell activation and function, we hypothesized that FTIs have immunomodulatory properties and are potential antirejection agents. An investigation was performed on a potent FTI to evaluate this hypothesis in the in vitro setting.The in vitro effects of the FTI A-228839 were evaluated. Lectin-or antigen presenting cell (APC)-induced lymphocyte proliferation in the presence of A-228839 was measured. The effects of A-228839 on 1E5 T cell polarity were assessed by microscopy. Intracellular calcium ([Ca 2 + ] i ) kinetics of lectin-activated lymphocytes was monitored by flow cytometry. The effects of A-228839 on peripheral blood mononuclear cell (PBMC) cytokine production was assessed by a cytometric bead array method. Activation-induced apoptosis was measured with an annexin V staining assay.A-228839 inhibited lectin-induced proliferation (IC 50 = 0.24 F 0.11 AM). The inhibitory effects of A-228839 on lectin induced lymphocyte proliferation were additive to those of CsA. A-228839 was more effective in inhibiting APC-induced T cell proliferation (IC 50 = 0.10 F 0.09 AM). A-228839 significantly disrupted the polarized shape of 1E5 T cells at physiologic concentrations. A-228839 altered PBMC baseline [Ca 2 + ] i but did not affect [Ca 2 + ] i kinetics during lectin-induced lymphocyte activation. A-228839 inhibited lymphocyte Th1 cytokine production at submicromolar levels and promoted apoptosis in lectinactivated lymphocytes.A-228839 potently inhibits lymphocyte activation and function. Our results suggest that FTIs may represent a new class of clinically useful immunomodulatory agents. A-228839 has potent in vitro immunomodulatory properties that warrant in vivo evaluation as an antirejection agent. D

Potent Farnesyltransferase Inhibitor ABT-100 Abrogates Acute Allograft Rejection

“…We found that A-228839 potently inhibited lymphocyte proliferation and cytokine production, interfered with intracellular calcium homeostasis, and promoted activation-induced apoptosis. 16 Here we confirmed that ABT-100, another selective farnesyltransferase inhibitor, also potently inhibits human PBMC proliferation. Like A-228839, ABT-100 has potent activity against lymphocyte proliferation at concentrations near 1 mol/liter yet fails to completely suppress lymphocyte proliferation even at high concentrations.…”

“…However, in our in vitro studies with A-228839, additive (not synergistic) activity against lymphocyte proliferation was seen when it was combined with constant exposure to CsA. 16 Defects in Ras activation have also been proposed to be an underlying mechanism of T-cell anergy. 30,31 T-cell anergy is a strategy for obtaining tolerance.…”

“…Indeed, we were able to show that A-228839, a potent farnesyltransferase inhibitor, inhibited lymphocyte activation and cytokine production in vitro. 16 In light of the results of our in vitro studies, we describe here our efforts to determine the potential anti-rejection properties of ABT-100, an orally available farnesyltransferase inhibitor. It has an inhibitory concentration of 50% (IC 50 ) of 0.13 nmol/liter toward bovine farnesyltransferase and selectivity vs geranylgeranyltransferase (IC 50 Ͼ 10,000 nmol/liter).…”

Inhibition of protein geranylgeranylation and farnesylation protects against graft-versus-host disease via effects on CD4 effector T cells

“…4 Mechanistically it was shown in vitro that FTI can modulate T-cell differentiation and proliferation. [6][7][8] In particular the study by Gaylo et al, 4 showing that FTI can significantly delay the rejection of skin allografts in mice, provides strong evidence that FTI have potent immunmodulary properties. In their studies the authors showed that FTI affected both CD4 + and CD8 + T cells.…”

Effects of the kinase inhibitor CGP41251 (PKC 412) on lymphocyte activation and TNF-α production

“…To determine if CGP41251 affected the early events of lymphocyte activation, the intracellular calcium kinetics in CGP41251-treated PBMC's were measured during PHA activation as described [29]. Briefly, incremental concentrations of CGP41251 and the calcium indicator dyes fluo-4 (3 AM) and Fura-red (3 AM) were added to PBMC's in PBS and incubated for 1 h at room temperature protected from light.…”