title: Pentoxifylline synergizes with all-trans retinoic acid to induce differentiation of HL-60 myelocytic cells, but suppresses tRA-augmented clonal growth of normal CFU-GM.
abstract: All-trans retinoic acid (tRA) has been shown to promote terminal differentiation of promyelocytic leukemia cells, but frequently induce hyperleukocytosis and pulmonary leakage syndrome. Employing pentoxifylline (PTX), a phosphodiesterase inhibitor which could raise intracellular cAMP and modulate leukocyte activation, we sought to investigate if PTX could enhance tRA-induced promyelocytic leukemic cell differentiation but suppress tRA-augmented growth and activation of human granulocytes. tRA could significantly suppress clonal growth of U937 and HL-60 leukemic cells but enhanced the CFU-GM formation of normal bone marrow cells (22 +/- 6 vs. 90 +/- 16 CFU/well). PTX significantly augmented tRA suppression of clonal growth of U937 and HL-60 leukemic cells but suppressed tRA-augmented CFU-GM formation of normal bone marrow cells (90 +/- 16 vs. 25 +/- 9 CFU/well). In addition, PTX enhanced tRA-induced growth inhibition and differentiation of promyelocytic HL-60 leukemic cells, but suppressed respiratory burst activation by the immature granulocytic HL-60 cells and suppressed CD11b adhesion molecule expression by mature granulocytes. PTX similar to dibutyric cAMP promoted HL-60 myelocytic leukemic cell differentiation and growth inhibition, whereas PTX, in contrast to dibutyric cAMP which could augment phorbol myristate acetate (PMA)-elicited respiratory burst activity by immature granulocytes, suppressed the PMA-elicited respiratory burst activity by immature and mature granulocytes. PTX did not raise the intracellular cAMP level of HL-60 cells, but partly suppressed the dibutyric cAMP-elicited elevation of intracellular cAMP level. Results from these studies suggest that PTX might act through different signaling pathways to enhance tRA-induced myelocytic leukemic cell differentiation but prevent from hyperreactive normal granulopoiesis and granulocyte activation.
authors.affiliation: Chang Gung Children's Hospital at Kaohsiung, Taiwan.
authors.forename: K D
authors.initials: KD
authors.lastname: Yang
authors.forename: C Y
authors.initials: CY
authors.lastname: Chao
authors.forename: M F
authors.initials: MF
authors.lastname: Shaio
mesh_terms: D001854:Bone Marrow Cells / Q000166:cytology; D018845:CD11 Antigens / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002999:Clone Cells / Q000166:cytology; D000242:Cyclic AMP / Q000378:metabolism; D004357:Drug Synergism; D006098:Granulocytes / Q000166:cytology*; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D008264:Macrophages / Q000166:cytology*; D010431:Pentoxifylline / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D016897:Respiratory Burst / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D018845:CD11 Antigens; D010726:Phosphodiesterase Inhibitors; D014212:Tretinoin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D010431:Pentoxifylline