piperidines and Leukemia--Monocytic--Acute

The Bruton's tyrosine kinase (Btk) inhibitor ibrutinib has demonstrated promising efficacy in a variety of hematologic malignancies. However, the precise mechanism of action of the drug remains to be fully elucidated. Tumor-infiltrating macrophages presented in the tumor microenvironment have been shown to promote development and progression of B-cell lymphomas through crosstalk mediated by secreted cytokines and chemokines. Because Btk has been implicated in Toll-like receptor (TLR) signaling pathways that regulate macrophage activation and production of proinflammatory cytokines, we investigated the immunomodulatory effects of Btk inhibitor on macrophages. Our results demonstrate that Btk inhibition efficiently suppresses production of CXCL12, CXCL13, CCL19, and VEGF by macrophages. Furthermore, attenuated secretion of homeostatic chemokines from Btk inhibitor-treated macrophages significantly compromise adhesion, invasion, and migration of lymphoid malignant cells and even those not driven by Btk expression. The supernatants from Btk inhibitor-treated macrophages also impair the ability of endothelial cells to undergo angiogenic tube formation. Mechanistic analysis revealed that Btk inhibitors treatment downregulates secretion of homeostatic chemokines and cytokines through inactivation of Btk signaling and the downstream transcription factors, NF-κB, STAT3, and AP-1. Taken together, these results suggest that the encouraging therapeutic efficacy of Btk inhibitor may be due to both direct cytotoxic effects on malignant B cells and immunomodulatory effects on macrophages present in the tumor microenvironment. This novel mechanism of action suggests that, in addition to B-cell lymphomas, Btk inhibitor may also have therapeutic value in lymphatic malignancies and solid tumors lacking Btk expression.

Topics: Adenine; Agammaglobulinaemia Tyrosine Kinase; Apoptosis; Biomarkers, Tumor; Cell Proliferation; Chemokines; Cytokines; Humans; Leukemia, Monocytic, Acute; Lymphoma, B-Cell; Lymphoma, T-Cell; Macrophages; Piperidines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Pyrazoles; Pyrimidines; Signal Transduction; Tumor Cells, Cultured

The effect of thrombin receptor activation on monocyte conformation was evaluated using the human monocyte cell line, THP-1, and the thrombin mimetic peptide, Trap-14. Treatment of THP-1 cells with Trap-14 induced rapid rounding of ameboid cells adherent to fibronectin-coated slides, whereas cell rounding was abrogated in the presence of the nitric oxide synthase inhibitor, NG-nitro-L-arginine or the endothelin B receptor antagonist, BQ-788. Endothelin-1 (ET-1) levels in the culture supernatant increased markedly within minutes of Trap-14 exposure with a concomitant loss in cellular ET-1 immunoreactivity. Importantly, loss of ET-1 immunoreactivity was blocked by pretreatment with the vesicle translocation inhibitor, nocodazole. Trap-14 potently induced the release of NO from THP-1 cells, whereas NO release was ablated by preincubation with BQ-788. These data demonstrate that thrombin receptor activation may inhibit cellular spreading as a result of autocrine ET-1 release and subsequent endothelin B receptor-dependent NO production, and suggest that initial exposure of inflammatory cells to thrombin may limit cellular activation and recruitment.

Topics: Cell Adhesion; Cell Size; Endothelin Receptor Antagonists; Endothelin-1; Humans; Leukemia, Monocytic, Acute; Monocytes; Nitric Oxide; Nocodazole; Oligopeptides; Peptide Fragments; Piperidines; Receptor, Endothelin B; Receptors, Endothelin; Receptors, Thrombin; Thrombin; Tumor Cells, Cultured

The benzothiophene divarative raloxifene is known to mimic estrogen in human bone remodeling. To investigate the "in vitro" properties of raloxifene on osteoclast precursors, the human leukemic cell line FLG 29.1, which differentiates toward the osteoclastic phenotype, was examined for raloxifene binding and for evidence of its bioeffects. Scatchard and Hill analysis of binding data with the tritiated raloxifene demonstrated the presence of two classes of binding sites in both nuclear and cytosol fractions with Kd values of approximately 1 nM and approximately 5 nM, respectively. In addition, analysis of binding data using tritiated 17 beta E2 as ligand at high concentrations (10-40 nM) and either unlabeled 17 beta E2 or raloxifene as competitors gave similar results demonstrating the presence of type II EBS in these cells. Picomolar concentrations of raloxifene significantly (p < 0.05) inhibited cell proliferation. Moreover, the compound at nanomolar concentrations induced a significant dose- and time-dependent increase of progesterone receptor, and activated apoptotic cell death. These findings clearly demonstrate that raloxifene acts as an estrogen agonist in FLG 29.1 cells, acting through the estrogen receptor and, possibly, via multiple cooperative binding component(s).

Topics: Apoptosis; Binding Sites; Binding, Competitive; Cell Division; Cell Nucleus; Cytosol; Dithiothreitol; DNA Fragmentation; Electrophoresis, Agar Gel; Estradiol; Filaggrin Proteins; Humans; Leukemia, Monocytic, Acute; Microscopy, Electron; Osteoclasts; Piperidines; Promegestone; Raloxifene Hydrochloride; Receptors, Estrogen; Receptors, Progesterone; Tumor Cells, Cultured