3558

IL2

IL-2|TCGF|lymphokine;interleukin 2;IL2;interleukin 2

T cell growth factor|aldesleukin|interleukin-2|involved in regulation of T-cell clonal expansion

4q26-q27

protein-coding

Proliferation and differentiation of hematopoietic progenitor cells are regulated by a network of stimulatory and inhibitory cytokines. An understanding of the molecular mechanisms of growth control may provide a physiologic basis for the innovative therapy of bone marrow disorders. Among various accessory cells, bonemarrow T lymphocytes are capable of stimulating, as well as inhibiting, hematopoietic progenitor cells. We have now elucidated molecular mechanisms regulating the differential expression of T cell genes encoding for the stimulatory and inhibitory hematopoietic programs. Stimulation of hematopoiesis requires granulocyte-macrophage colony stimulating factor (GM-CSF), whereas inhibition requires interferon-gamma (IF gamma). Both cytokines can be induced by interleukin-2 (IL2). The T cell IL2 receptor consists of a 75 kD chain (p75) mainly expressed on a subset of resting T cells and a 55 kD chain (p55) which isstrongly expressed upon T cell activation. P55 and p75 associate on activated T cells to form a dimeric receptor molecule exhibiting high affinity for IL2. The p75 monomer has an intermediate affinity for IL2. expression of p55 in the context of the high affinity IL2 receptor constitutes a requirement for T cell IFg release. In contrast, p75 alone is capable of mediating the production of GM-CSF. Thus, T cells may be capable of selective production of cytokines with specific effects in hematopoietic growth control. Utilizing a human peripheral blood leukocyte genomic library, we identified various clones containing the entire GM-CSF gene, including coding and regulatory regions. Cloning of the GM-CSF gene allowed clinical studies utilizing recombinant DNA-derived GM-CSF. Chemotherapy-induced neutropenia contributes to both complications of cytotoxic therapy as well as increased relapse incidence of underlying disease. In a prospective randomized study, we have demonstrated that GM-CSF abrogates neutropenia following aplasiogenic chemotherapy in children and adolescents withsolid tumors, and that GM-CSF may reduce the duration of infectious episodes after cytotoxic therapy. Next, we escalated the cumulative doses of cytotoxic therapy in an ablative regimen followed by hematopoietic stem cell transplantation to treat patients with poor prognosis pediatric tumors. Morbidity of this highly toxic ablative regimen depends on the duration of myeloid aplasia. Median duration of aplasia following hyper-VAMP was 13 days with CM-CSF and 29 days without GM-CSF. In addition, we have employed p55 blocking monoclonal antibody for prevention of graft vs. host disease in bone marrow transplantation. The understanding of specific molecular mechanisms of hematopoietic immuno-regulation can thus be utilized to provide novel approaches to the treatment of bone marrow failure and cancer.

Neuroblastoma is one of the commonest solid tumors in children. Conventional therapeutic approaches, such as surgery, chemotherapy and radiotherapy, fail to control tumor progression in stage III and IV patients. The search for novel therapeutic strategies should necessarily take into account immunotherapy and gene therapy. Here the theoretical bases for the development of such approaches are discussed. Studies carried out with neuroblastoma (NB) cell lines have shownthat neoplastic cells express a wide array of potential tumor associated antigens (TAA) but are devoid of HLA molecules which are necessary for TAA presentation to the host immune system. Transfection of NB cells with the interferon gamma gene appears a promising approach, since this cytokine up-regulates the expression ofclass I HLA molecules in NB cells. Other cytokines of potential interest for gene transfer studies are interleukin 2 (IL2) and interleukin 12 (IL12).

BACKGROUND: Adjuvant interleukin-2 (IL-2) therapy after stem cell transplantation can improve the prognosis of patients with Ewing tumors. This has been attributed to stimulation of the immune system and its antineoplastic activity, thus eliminating minimal residual disease. As the side effects of systemic IL-2 limitthe dosage, attempts have been made to locally augment the concentration of IL-2in the proximity of the tumor. To achieve this, fibroblasts and/or tumor cells can be genetically modified to secrete IL-2 and then be injected to generate tumor immunogen. PROCEDURE: In a preliminary clinical trial we assessed whether the administration of transgenic IL-2-secreting fibroblasts was feasible withoutmajor toxicity and whether it had any effect regarding the activation of the immune system. We treated an 11-year-old boy with a peripheral neuroectodermal tumor of the left neck in fourth relapse, who was refractory to ALL available therapy. We transfected fibroblasts of the patient with an IL-2 gene expression vector using a cationic liposome reagent. In 51Cr cytotoxicity assays we obtained lysis of this patient's tumor cells by IL-2-stimulated mononuclear cells (MNCs).Under CT-guidance we intratumorally injected IL-2 transgenic autologous fibroblasts. RESULTS: We observed no local or systemic toxicity. In addition, wefound a rise in the CD3+CD56+ lymphocyte population, previously described as cytokine-induced killer cells. No other hematological parameter changed significantly. CONCLUSIONS: Our data suggest that the intratumoral injection of transgenic IL-2-secreting fibroblasts is feasible without major toxicity and maylead to an increase in CD3+CD56+ cells.