Discovery of a human erythroid differentiation factor (EDF) and its large-scale production

"Differentiation Induction" culture of human leukemic myeloid cells stimulates high production of macrophage differentiation inducing factor

A suitable procedure for the production of human monokines was defined as 'differentiation-induction' culture. Human monocytic leukemia THP-1 cells were well-differentiated from nonfunctional promonocytes into macrophage-like cells by the induction with a combination of mezerein, retinoic acid, and aMycoplasma fermentans extract. The differentiated THP-1 cells secreted a high amount of macrophage differentiation-inducing factor (DIF) activity and concomitantly produced other known monokines, such as tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α) and interleukin-1β (IL-1β), into the medium. These results suggest that other novel human monokines may also be found in the conditioned medium of THP-1 cells induced by the 'differentiation-induction' culture conditions defined in this study. Macrophage DIF was purified to homogeneity and NH(2)-terminal amino acid sequence analysis revealed that macrophage DIF is very similar or identical to human leukemia inhibitory factor (LIF). The cDNA encoding human LIF was isolated using the polymerase chain reaction, and a clone producing 3.7 μg/10(6) cells day recombinant LIF was selected from Chinese hamster ovary (CHO) cells which were transfected with the LIF cDNA. The recombinant LIF production in CHO cells was quantified using MTT reduction assay with M1 cells.

Co-ordinate expression of activin A and its type I receptor mRNAs during phorbol ester-induced differentiation of human K562 erythroleukemia cells

Activins were originally isolated based on their ability to stimulate follicle-stimulating hormone secretion but later they have been shown to regulate a number of different cellular functions such as nerve cell survival, mesoderm induction during early embryogenesis as well as hematopoiesis. We studied the regulation of activin A, a homodimer of betaA-subunits, mRNA and protein in K562 erythroleukemia cells, which are known to be induced toward the erythroid lineage in response to activin or TGF-beta or toward the megakaryocytic lineage by the phorbol ester protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA). Here we show by Northern blot analysis as well as by Western and ligand blotting that TPA strongly promotes activin betaA-subunit mRNA and activin A protein expression in K562 cells in time- and concentration dependent manner. In contrast, neither activin A nor TGF-beta induced betaA-subunit mRNA expression during erythroid differentiation in K562 cells. Interestingly, whereas activin type II receptors are not regulated during K562 cell differentiation (Hilden et al. (1994) Blood 83, 2163-2170), we now show that the activin type I and IB receptor mRNAs are clearly induced by TPA but not by activin or TGF-beta. We also show that the inducing effect of TPA on expression of activin betaA-subunit mRNA is potentiated by the protein kinase A activator 8-bromo-cAMP. We conclude that activin A and its type I receptors appear to be co-ordinately up-regulated during megakaryocytic differentiation of K562 cells.

Human activin betaA gene. Identification of novel 5' exon, functional promoter, and enhancers

On the basis of cDNA cloning, primer extension, and transfection experiments, we identified a novel 5' exon of the human activin betaA subunit gene, and found its enhancer and promoter regions as well as multiple transcription start sites. A series of deletion and mutation analyses of the enhancer sequences defined the 45-base pair core region (DR-1 core) containing two short elements with similarity to AP-1 (12-O-tetradecanoylphorbol-13-acetate response element; TRE) and CREB/ATF (cyclic AMP response element; CRE) binding sites, both of which were necessary for full enhancer activity. Gel shift and antibody supershift assays using DR-1 core region revealed the formation of two specific DNA-protein complexes, one of which could be partially dissociated by a competing oligonucleotide containing a single copy of the consensus TRE, but the other of which contained neither CREB/ATF nor AP-1 as major components. Although 12-O-tetradecanoylphorbol-13-acetate and cAMP induced the activin enhancer/promoter-driven CAT activity, such drug induction was obscured when either the TRE- or CRE-like elements were mutated in the native promoter context. Our results demonstrate that the promoter and enhancer regions identified here are essential for maintaining the efficient promoter activity of the human activin betaA subunit gene.

Follistatin inhibits activin-induced differentiation of rat follicular granulosa cells in vitro

The effect of follistatin on activin-induced granulosa cell differentiation was investigated in freshly harvested granulosa cells from diethylstilbestrol (DES)-treated rats. Activin induced a remarkable change in granulosa cellular morphology from elongated fibroblast-like to round cells, which follistatin prevented. Follistatin itself had no influence on the cellular morphology. We studied the action of follistatin on activin-induced differentiation of granulosa cells cultured in a chemically defined medium. Addition of activin (30 ng/ml) to the culture increased the FSH binding site approximately 2-fold compared with the control (spontaneous expression) level, whereas follistatin reduced the activin-induced expression level to the control level in a concentration-dependent manner. Activin (30 ng/ml) markedly augmented FSH-induced hCG binding and progesterone production by approximately 20-fold, and these effects were suppressed by follistatin in a concentration-dependent manner. Similarly, addition of follistatin to the culture induced a concentration-dependent decrease of activin-enhanced inhibin-producing activity, but had no effect on FSH-induced inhibin production. These results suggest that follistatin/activin-binding protein binds to activin stoichiometrically to suppress the activin-induced differentiation of rat granulosa cell in vitro, but follistatin itself has no direct effect on activin-independent reactions.

Regulation of activin βA mRNA level by cAMP

We demonstrated the presence of five species of the activin beta A mRNA in human placenta and one major RNA associated with two minor RNAs of the activin in the fetal membrane. We investigated the effect of 8-bromo-cAMP (8-Br-cAMP) on accumulation of activin beta A subunit mRNA in human fibrosarcoma HT1080 cells. Although low levels of the activin mRNA were detectable in the untreated cells, the one main RNA species was predominantly accumulated by 8-Br-cAMP. We propose that generation of multiple activin mRNAs in the fetal membrane and cAMP-treated HT1080 cells is presumably due to a cell-specific alternative polyadenylation.

Effects of activin A on anterior pituitary cells fractionated by centrifugal elutriation

We have shown previously that activin A increases the number of immunoreactive follicle-stimulating hormone (FSH) cells. To further investigate the action of activin A, we examined its effects on anterior pituitary cells fractionated by centrifugal elutriation. Before activin A treatment, FSH cells were widely distributed among various fractions; a higher proportion of FSH cells was found in larger cell fractions (fractions 5-9), and a lower proportion in smaller cell fractions (fractions 2-4). After culture of the cells in each fraction with activin A (10 ng/ml) for 72 h, the number of FSH cells in fraction 4 only was significantly (P less than 0.05) higher by 225% than that in cells cultured without activin A. The amount of FSH secreted into the medium was minimal or undetectable in fractions 1-4. However, FSH secretion tended to be, or was significantly (P less than 0.01 in fraction 9), stimulated by activin A in fractions 5-9, in which the numbers of FSH cells were not significantly affected. These results suggest a dual mode of action of activin A on FSH: activin A increases the number of FSH cells in a specific type(s) of middle-sized cell fraction, and stimulates FSH secretion at least from larger cells without affecting the number of FSH cells.

Phorbol ester-treated human acute myeloid leukemia cells secrete G-CSF, GM-CSF and erythroid differentiation factor into serum-free media in primary culture

Upon treatment with the phorbol ester, tetradecanoylphorbol 13-acetate (PMA), peripheral mononuclear blood cells from patients with acute myeloid leukemia secrete into serum-free cell-conditioned media (PMA-CCM) at least three distinct nondialysable 'hematopoietic' factors: granulocyte-colony-stimulating factor (G-CSF), granulocyte/macrophage-colony-stimulating factor (GM-CSF) and erythroid differentiation factor (EDF, activin A). G-CSF was identified by its stimulation of [3H]thymidine incorporation into a G-CSF-responsive cell line, NSF-60, and the inhibition of its stimulation by a G-CSF-specific monoclonal antibody (MAB). GM-CSF was identified by its stimulation of [3H]thymidine incorporation into a GM-CSF-responsive line, TALL-101, and the inhibition of its stimulation by a GM-CSF-specific MAB. EDF was identified by its ability to stimulate erythroid differentiation in mouse erythroleukemia cell lines, its identical retention times to those of authentic EDF on three successive reverse-phase HPLC columns and characterization of its penultimate N-terminal residue as leucine which is the same as that of authentic EDF. Both authentic EDF and the erythroid-stimulating activity in PMA-CCM were found to act synergistically with a suboptimal inducing concentration of a well-studied inducing agent, dimethyl sulfoxide, in inducing erythroid differentiation. In addition, a fourth activity was observed in PMA-CCM: normal human fetal bone marrow cell-proliferation stimulating activity (FBMC-PSA). FBMC-PSA was identified by its ability to stimulate the growth of granulocytes and macrophages in FBMC suspension cultures, which neither recombinant G-CSF or GM-CSF were found to do.

Effect of erythroid differentiation factor on erythroid differentiation and proliferation of K-562 cells

The effects of erythroid differentiation factor (EDF) on the levels of zeta-globin and several proto-oncogene mRNAs and transferrin receptors (Tf-R) of K-562 cells were examined. EDF decreased Tf-R expression and increased the level of zeta-globin mRNA. The mRNA level of c-fos began to rise within 3 hours and continued to increase up to 72 hours, but the levels of c-myb and c-abl decreased to 23 and 19%, respectively, of their initial levels after 48 hours. In contrast, the mRNA levels of c-myc and c-fms decreased transiently, but recovered within 48 hours. The modulation of several proto-oncogene mRNA levels was observed much earlier than the differentiation induction and the growth inhibition of K-562 cells by EDF.

Inducible gene expression of activin A/erythroid differentiation factor in HL-60 cells

Treatment of HL-60 cells with 12-O-tetradecanoyl-phorbol 13-acetate (TPA) for 48 h induced expression of mRNA of beta A chain of activin A/erythroid differentiation factor. Under the same condition, interferon-gamma caused a slight increase in beta A chain mRNA, whereas 1 alpha, 25-dihydroxyvitamin D3, dimethylsulfoxide and all-trans-retinoic acid failed to induce this mRNA in HL-60 cells. Furthermore, 4 h-treatment with TPA or lipopolysaccharide (LPS) induced a marked increase in beta A chain mRNA levels in interferon-gamma-pretreated HL-60 cells. In the cells pretreated with 1 alpha, 25-dihydroxyvitamin D3, TPA and LPS induced as little increase in beta A chain mRNA as in the control cells. Neither alpha nor beta B chain mRNA was detected in any sample. These results indicate that interferon-gamma has a priming effect on the activation of activin A/erythroid differentiation factor gene by TPA or LPS in HL-60 cells.

Identification of the two types of specific receptor for activin/EDF expressed on Friend leukemia and embryonal carcinoma cells

Activin and inhibin are polypeptide factors which control the release of follicle stimulating hormone(FSH) from pituitary cells. The recent finding that erythroid differentiation factor(EDF) is identical to activin showed the multifunctional feature of this protein. To identify the specific receptor for activin, the binding of 125I-labeled activinA was investigated for a number of culture cell lines. Friends leukemia cell, which can be differentiated by activin, and embryonal carcinoma(EC) cells(PCC3, P19 and F9), were found to express 3500-20,000 per cell of activin receptors. Scatchard plot analysis of the binding data shows that the receptors on those cells could be divided into two groups with different Kd values. The Kd values of high and low affinity receptors are 0.15-0.4 nM and 1.5-3.0 nM respectively. The proportion of the number of the high and low affinity receptors was varied in each cell. Inhibin was able to compete for activin binding to both types of receptors, although the binding affinity was about 50-200 fold lower than that of activinA. Transforming growth factor-beta had no binding ability to the activin receptors.