David Pelloso

Impaired development of human Th1 cells in patients with deficient expression of STAT4.

IL-12 activates STAT4, which is a critical regulator of inflammation and T helper type I (Th1) lineage development in murine systems. The requirement for STAT4 in the generation of human Th1 cells has not been examined thoroughly. Compared with control Th1 cultures, expression of the Th1 genes IFNgamma, IL-12Rbeta2, and TNFalpha is greatly reduced in Th1 cultures of CD4 T cells isolated from lymphoma patients after autologous stem cell transplantation who have acquired STAT4 deficiency. Moreover, IL-4 and IL-5 production is increased in patient Th1 cultures though there are no defects in the development of Th2 cells. Reconstitution of STAT4 in patient T cells allowed recovery of IFNgamma and IL-12Rbeta2 expression, whereas ectopic expression of IL-12Rbeta2 did not rescue STAT4 expression, and increased IFNgamma production only to levels intermediate between control and patient samples. These results demonstrate that, as in murine systems, STAT4 is required for optimal human Th1 lineage development.

Effects of interleukin-18 on natural killer cells: Costimulation of activation through Fc receptors for immunoglobulin

The antitumor activity of monoclonal antibodies is mediated by effector cells, such as natural killer (NK) cells, that express Fc receptors for immunoglobulin. Efficacy of monoclonal antibodies, including the CD20 antibody rituximab, could be improved by agents that augment the function of NK cells. Interleukin (IL)-18 is an immunostimulatory cytokine that has antitumor activity in preclinical models. The effects of IL-18 on NK cell function mediated through Fcγ receptors were examined. Human NK cells stimulated with immobilized IgG in vitro secreted IFN-γ as expected; such IFN-γ production was partially inhibited by blocking CD16 with monoclonal antibodies. IL-18 augmented IFN-γ production by NK cells stimulated with immobilized IgG or CD16 antibodies. NK cell IFN-γ production in response to immobilized IgG and/or IL-18 was inhibited by chemical inhibitors of Syk and several other kinases involved in CD16 signaling pathways. IL-18 augmented antibody-dependent cellular cytotoxicity (ADCC) of human NK cells against rituximab-coated Raji cells in vitro. IL-18 and rituximab acted synergistically to promote regression of human lymphoma xenografts in SCID mice. Inasmuch as IL-18 costimulates IFN-γ production and ADCC of NK cells activated through Fc receptors in vitro and augments antitumor activity of rituximab in vivo, it is an attractive cytokine to combine with monoclonal antibodies for treatment of human cancer.

Soypeptide lunasin in cytokine immunotherapy for lymphoma.

Immunostimulatory cytokines can enhance anti-tumor immunity and are part of the therapeutic armamentarium for cancer treatment. We have previously reported that post-transplant lymphoma patients have an acquired deficiency of signal transducer and activator of transcription 4, which results in defective IFNγ production during clinical immunotherapy. With the goal of further improving cytokine-based immunotherapy, we examined the effects of a soybean peptide called lunasin that synergistically works with cytokines on natural killer (NK) cells. Peripheral blood mononuclear cells of healthy donors and post-transplant lymphoma patients were stimulated with or without lunasin in the presence of IL-12 or IL-2. NK activation was evaluated, and its tumoricidal activity was assessed using in vitro and in vivo tumor models. Chromatin immunoprecipitation assay was performed to evaluate the histone modification of gene loci that are regulated by lunasin and cytokine. Adding lunasin to IL-12- or IL-2-stimulated NK cells demonstrated synergistic effects in the induction of IFNG and GZMB involved in cytotoxicity. The combination of lunasin and cytokines (IL-12 plus IL-2) was capable of restoring IFNγ production by NK cells from post-transplant lymphoma patients. In addition, NK cells stimulated with lunasin plus cytokines displayed higher tumoricidal activity than those stimulated with cytokines alone using in vitro and in vivo tumor models. The underlying mechanism responsible for the effects of lunasin on NK cells is likely due to epigenetic modulation on target gene loci. Lunasin represents a different class of immune modulating agent that may augment the therapeutic responses mediated by cytokine-based immunotherapy.

Immunological Consequences of Interleukin 12 Administration after Autologous Stem Cell Transplantation

Purpose: The purpose is to determine the immunological effects of recombinant human interleukin (rhIL)-12 therapy after autologous stem cell transplantation. Experimental Design: Twelve patients (8 non-Hodgkin’s lymphoma, 2 Hodgkin’s disease, and 2 plasma cell myeloma) were treated with rhIL-12 by bolus i.v. injection in doses of 30, 100, or 250 ng/kg starting at a median of 66 days posttransplant. Immunological assays were performed using serum and peripheral blood mononuclear cell (PBMC) samples obtained on study. Results: Dose-dependent increases in the total lymphocyte count occurred during rhIL-12 therapy. The absolute number of peripheral blood CD4 T cells increased up to 16.3-fold, CD8 T cells up to 20.5-fold, B cells up to 11-fold, and natural killer (NK) cells up to 12.3-fold during rhIL-12 administration and returned to pretreatment baseline levels after discontinuation of rhIL-12. CD56bright NK cells expanded dramatically in the blood of a patient with baseline lymphopenia before rhIL-12 therapy. In vitro proliferation of patient PBMCs in response to IL-12 was indistinguishable from that of PBMCs obtained from healthy control sub-jects. Moreover, spontaneous in vitro proliferation of patient PBMCs increased significantly during rhIL-12 therapy. Increased levels of IFN-γ and IL-18 were detected in the serum of patients treated in the 100 and 250 ng/kg dose cohorts during the first multiple dose cycle. Conclusions: Expansion of T, B, and NK cells occurs in vivo during rhIL-12 therapy after autologous stem cell transplantation for hematological malignancies. In contrast to their striking defect in IL-12-induced IFN-γ production, posttransplant patient PBMCs exhibit normal proliferative responses to IL-12 in vitro. Additional investigation of rhIL-12 for posttransplantation immunotherapy is warranted.