Proliferation of acute myelogenous leukemia (AML) derived blast cells requires the presence in culture of one or more growth factors. In the majority of cases Interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulate clonogenicity of AML blasts, which can be synergised by Interleukin-6 (IL-6), Interleukin-1 (IL-1) and granulocyte colony-stimulating factor (G-CSF). In contrast, macrophage colony-stimulating factor (M-CSF) favors deterministic divisions. A substantial part of AML samples have clonogenic cells which, however, proliferate autonomously in vitro. The production by leukemic cells of a variety of growth or synergizing factors including GM-CSF, G-CSF, IL-1, IL-6, and Tumor Necrosis Factor (TNF) has been demonstrated and a fraction of cases will use these molecules to support clonogenic growth in an autocrine or paracrine fashion. However, unlike the situation with retrovirus-induced murine or avian leukemias, the role of production of CSFs and other cytokines by human leukemic cells in the transformational process remains uncertain.

Biological Factors↗

PubMedDate not supplied

In vivo administration of recombinant human interleukin-3 elicits an acute phase response involving endogenous synthesis of interleukin-6.

Interleukin-6 has been shown to stimulate in vitro synthesis of C-reactive protein (CCRP) in hepatocytes by enhancing the transcriptional rate of the CRP gene. It has also been demonstrated that IL-6 spurs the terminal differentiation of B-cells into immunoglobulin secreting cells when synergizing with IL-3. IL-6 may therefore act as a prime molecule in the acute phase and immune response. We have administered rh IL-3 to cancer patients in a phase I/II clinical trial. Endogenous IL-6 levels increased in a dose-dependent fashion upon i.v. bolus injection of rh IL-3 and continued to be significantly elevated above pretreatment levels when IL-3 was further administered by the s.c. route. Increases of IL-6 levels were associated with enhanced production of CRP in vivo detected after 24 h of injection. At day 14 of rh IL-3 treatment plasma immunoglobulin concentrations were measured and IgM was found to be increased by greater than 2.5 fold above starting levels. These results indicate that rh IL-3 also augments the acute phase response in vivo and contributes to increased synthesis of IgM and that induction of endogenous IL-6 is involved in these events.

Acute-Phase Proteins↗