lucifer-yellow and Leukemia--Erythroblastic--Acute

Phorbol ester tumor promoters bind to specific cellular receptors (probably protein kinase C) and modulate membrane structure and function and gene expression of target cells. Using cell culture systems, we are studying the interaction of phorbol esters with the cellular membrane and subsequent modulation of gene expression. Our recent results can be summarized as follows: 1) specific binding of phorbol esters to mammalian cells can be inhibited by a human placental factor, which we have partially purified and characterized. 2) Phorbol ester tumor promoters reversibly inhibit intercellular communication, as measured by electrical coupling and dye transfer between cultured cells, suggesting that they inhibit both ionic and molecular transfer between cells. 3) In vitro transformation of Balb/c 3T3 cells results in blockage of intercellular communication between normal and transformed cells, indicating that blocked intercellular communication may play a role in cell transformation. 4) 12-O-Tetradecanoylphorbol-13-acetate (TPA) can continuously inhibit differentiation and globin gene expression in Friend erythroleukemia cells, without affecting their growth rate, for about 3 years. Both globin gene expression and terminal differentiation of Friend cells occur again upon removal of TPA from culture medium during such long-term culture.

Topics: Animals; Caenorhabditis elegans Proteins; Carrier Proteins; Cell Communication; Cell Differentiation; Cell Line; Cell Membrane; Cell Transformation, Neoplastic; Female; Gene Expression Regulation; Humans; Isoquinolines; Leukemia, Erythroblastic, Acute; Mice; Phorbol Esters; Phorbols; Pregnancy; Protein Kinase C; Protein Kinases; Receptors, Drug; Receptors, Immunologic

Myeloid dendritic cells (DC) are representatives of a rare and phenotypically diverse population of professional antigen presenting cells possessing high functional heterogeneity and flexibility. Here we studied the phenotypic, functional and electrophysiological characteristics of KG-1 cells, an erythroleukemia model cell line, which shares morphological and physiological similarities with immature and mature myeloid DC. We compared the expression of internalizing receptors and other cell surface molecules, antigen uptake and migration of unstimulated and activated KG-1 cells with the characteristics of immature and mature DC. Unstimulated KG-1 cells were less potent in capturing extracellular materials than immature DC. In contrast to monocyte-derived DC KG-1 cells stimulated by PMA and ionomycin ceased to migrate along the MIP-3beta chemokine gradient despite their high expression of CCR7 chemokine receptor and MDR, a transporter implicated in DC migration. Moreover, we determined the ion channel repertoire of KG-1 cells before and after treatment with PMA and ionomycin by using the patch-clamp technique. We found that both unstimulated and activated KG-1 cells expressed time- and voltage-independent, ChTx sensitive intracellular Ca(2+)-gated potassium conductance suggesting the presence of K(Ca) channels in their membranes. Based on our results we propose that KG-1 cells resemble myeloid DC but also possess unique phenotypic, functional and electrophysiological characteristics.

Topics: Animals; Calcium; Cell Movement; Dendritic Cells; Dextrans; Fluorescein-5-isothiocyanate; Humans; Isoquinolines; Leukemia, Erythroblastic, Acute; Patch-Clamp Techniques; Tumor Cells, Cultured