Different mechanisms of inhibition by alkyl-lysophospholipid and phorbol ester of granulocyte-macrophage colony-stimulating factor binding to human leukemic cell lines.
We investigated the effects of rac-1-O-octadecyl-2-O-methyl-glycero-3-phosphocholine (ET-18-OCH3) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on granulocyte-macrophage colony-stimulating factor (GM-CSF) binding to human leukemic cell lines HL60, U937, KG-1, KG-1a, and K562. HL60, U937, and KG-1 exhibited the high-affinity receptors, but KG-1a and K562 revealed no demonstrable receptors. ET-18-OCH3 inhibited GM-CSF binding to HL60, U937, and KG-1 cells with a half-maximal inhibitory concentration of 16, 10, and 78 microM, respectively. ET-18-OCH3 at 10 microM reduced GM-CSF binding sites on HL60, U937, and KG-1, but had little effect on the dissociation constant (Kd). ET-18-OCH3 at 10 and 30 microM significantly (p < 0.01) decreased, in a dose-dependent manner, the total uptake, surface binding, and internalization of GM-CSF. The internalization of GM-CSF was more profoundly inhibited than its surface binding. TPA at 1 and 10 nM inhibited GM-CSF binding. Inhibition of GM-CSF binding by a combination of ET-18-OCH3 (10 microM) and TPA (1 or 10 nM) was less than additive, and ET-18-OCH3 partially inhibited TPA-induced protein kinase C (PKC) depletion in the cytosol and translocation to the particulate fractions. It is suggested that the inhibition of GM-CSF binding by ET-18-OCH3 is due in part to disruption of the plasma membrane and that the inhibition of GM-CSF binding by TPA is due to activation of PKC.
Shoji
M
M
Department of Medicine (Hematology/Oncology), Emory University School of Medicine, Atlanta, GA 30322.
Fukuhara
T
T
Winton
E F
EF
Berdel
W E
WE
Vogler
W R
WR
D000970:Antineoplastic Agents / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007938:Leukemia / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D007942:Leukemia, Experimental / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D010742:Phospholipid Ethers / Q000494:pharmacology*; D011485:Protein Binding; D011493:Protein Kinase C / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D007457:Iodine Radioisotopes; D010742:Phospholipid Ethers; C026659:edelfosine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate