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Background: Dose and injection times have not previously been determined for subcutaneously administered recombinant human erythropoietin that would allow sufficient deposition of blood for autologous use in cardiac surgery., Study Design and Methods: A double-blind, multicenter trial of placebo (Group 1) and recombinant human erythropoietin at 12,000 IU (Group 2) and at 24,000 IU (Group 3) was performed on 114 patients at 26 institutions to determine the dosage that would permit an 800-g preoperative deposit of blood for autologous use. The test drug was administered subcutaneously on Days 21, 14, and 7 prior to operation, and oral iron preparations at 200 mg per day were given for 21 days. There were 28 patients in Group 1, 28 in Group 2, and 30 in Group 3, with 28 excluded for a violation of the protocol., Results: Blood was safely drawn 14 and 7 days before operation from 22 patients in Group 1 (78.6%), from 26 in Group 2 (92.9%), and from all patients in Group 3 (p = 0.018). The hemoglobin level on the day before operation decreased by 1.1 +/- 1.1 g per dL (11 +/- 11 g/L) in Group 1 and by 0.9 +/- 0.9 g per dL (9 +/- 9 g/L) in Group 2 and rose by 0.1 +/- 0.8 g per dL (1 +/- 8 g/L) in Group 3, compared to initial levels. Allogeneic blood transfusion could be avoided in 62, 89, and 90 percent of Group 1, 2, and 3 patients, respectively (p = 0.013)., Conclusion: The present study shows that subcutaneously administered recombinant human erythropoietin at a dose of 24,000 IU per week for 3 weeks is effective and sufficient to allow the safe deposition of 800 g of blood for autologous use in cardiac surgery.

Preoperative blood reservation for autologous blood transfusion generally causes anemia. We performed a double blind controlled study to determine the optimal dose of subcutaneous rHuEPO (recombinant human erythropoietin, KRN5702) for preventing preoperative anemia due to blood reservation. Patients received KRN5702 subcutaneously once a week in a doses of 12000, 24000 or 36000 IU by a double blind technique. After storage of 1200 ml of their own blood right before surgery, their hemoglobin (Hb) averaged about 1 and was about 0.5 g/dl lower than the level before administration of KRN5702 in doses of 12000 and 24000 IU, respectively. This fall was significant. In patients receiving KRN5702 in a dose of 36000 IU, the level of Hb rose instead of a fall; Hb immediately before surgery was 1.1% higher than that before administration which, however, was not significant. This elevation indicates a possibility of abnormal elevation of Hb at this dose. The mean Hb value right before surgery was significantly lower in patients receiving 12000 IU KRN5702 than in patients of the other two groups. The recovery rate of Hb was an indicator to reflect improvement of anemic conditions, and increased as the dose increased after the blood reservation. The rate in the 12000 IU group was significantly lower than that in the other two groups; there was not much difference between the other two rates. We estimated that to reserve 1200 ml of autologous blood, 24000 IU of KRN5702 is adequate but not excessive. One patient receiving 24000 IU showed side effects including an elevation of body temperature, rash, and edema.

The safety and efficacy of recombinant human erythropoietin (epoetin alpha) were investigated in adult aplastic anemia patients whose hemoglobin (Hb) concentration was less than 10g/dl. Epoetin alpha was given subcutaneously every day at a dose of 3,000IU/body for two weeks, and the dosage was increased to 6,000IU, 12,000IU and 24,000IU every two weeks when the increment of Hb was insufficient. In cases in whom Hb concentration increased by more than 1g/dl or whose transfusion requirements reduced to less than 50%, treatment was judged to be effective. The whole rate of efficacy was 34.5% (10/29). Response to epoetin alpha treatment was better in patients whose symptoms were relatively mild. Mild cases responded to the treatment with 6,000IU/body/day, although a dosage of 24,000IU/body/day was required in moderate or severe cases. Neither serious adverse effect nor abnormal laboratory findings were observed. These results suggest that high dose subcutaneous epoetin alpha treatment is effective for the aplastic anemia in terms of increasing Hb concentration and reducing blood transfusions.

The safety and efficacy of recombinant human erythropoietin (epoetin alpha) were investigated in anemic patients with myelodysplastic syndrome (MDS) whose hemoglobin (Hb) concentration was less than 10g/dl. Epoetin alpha was given subcutaneously daily at a dose of 3,000IU/body for two weeks and the dosage was increased to 6,000IU, 12,000IU, and 24,000IU at two week interval when the increment of Hb was insufficient. Patients in whom the Hb concentration increased by more than 1g/dl or whose blood transfusion requirement reduced to below 50% were considered to be cases of effective treatment. The overall rate of effectiveness was 20.6% (7/34). Response to epoetin alpha treatment was better in patients with refractory anemia (RA) or RA with ringed sideroblasts (RARS). The high dose epoetin alpha (12,000-24,000IU/body/day) was required for the patients to respond. These results suggest that the high dose subcutaneous epoetin alpha treatment is effective for the anemia associated with MDS in terms of increasing Hb concentration and reducing blood transfusion.

Safety and efficacy of recombinant human erythropoietin (epoetin alpha) were investigated in anemic patients with multiple myeloma whose hemoglobin (Hb) concentration was less than 10g/dl. Epoetin alpha (3,000IU/body) was given subcutaneously daily for two weeks and the dosage was increased to 6,000IU, 12,000IU and 24,000IU every two weeks when the increment of Hb was insufficient. Cases in which Hb concentration increased by more than 1g/dl or in which blood transfusion requirements decreased by more than 50% were judged to be effective. The overall rate of efficacy was 52.6% (10/19). Response to epoetin alpha treatment was better in patients whose blood erythropoietin level was relatively low. The majority of patients responded to the treatment with up to 6,000IU/body/day but a dosage of more than 12,000IU/body/day was required in some cases. No serious adverse effects or abnormal laboratory findings were observed. These results suggest that high-dose subcutaneous epoetin alpha treatment is effective for anemia associated with multiple myeloma in terms of increasing Hb concentration and reducing blood transfusion.

Clinical usefulness of cytokines in cancer treatment has been described. Cytokines presently used in clinical practice are IFNs, IL-2, and hematopoietic growth factors. IFNs and IL-2 used with an expectation of direct antitumor effect of these cytokines have been proven to be specifically effective against certain types of tumors. Hematopoietic growth factors have been used as the adjuvant drugs in cancer treatment and proven to be effective against neutropenia and associated infections after chemotherapy and bone marrow transplantation. Future development of new cytokines and trials on the combination among cytokines and cytokines with chemotherapeutic agents, will promote the usefulness of cytokines in cancer treatment.

Serum erythropoietin (Epo) titers in patients with various hematological malignancies and related diseases were determined by radioimmunoassay. Serum Epo titer was inversely correlated with hemoglobin concentration in iron deficiency anemia, aplastic anemia, myelodysplastic syndromes (MDS), acute leukemia, malignant lymphoma, multiple myeloma and myelofibrosis, but there was no correlation between serum Epo titer and hemoglobin concentration in chronic myelogenous leukemia or polycythemias. Serum Epo titers in aplastic anemia were much higher than those in iron deficiency anemia. Serum Epo titers in MDS, malignant lymphoma and multiple myeloma differed considerably among patients. Serum Epo titers in untreated polycythemia vera were significantly lower than in treated polycythemia vera or secondary polycythemia.

In a phase II clinical trial to test the ability of recombinant human erythropoietin (r-HuEPO) to reverse the anemia of patients undergoing hemodialysis, the changes of enzyme activity in red blood cells were evaluated in 5 hemodialysis anemic patients who were treated with r-HuEPO. Concerning the activity levels measured, the following conclusions are drawn. 1) HK, ALD, TPI, G6PD and 6PGD were statistically significantly increased at the time when the hematocrit has risen by 8% with the use of r-HuEPO. 2) The enzyme activity levels of PFK, GA3PD, MPGM, ENOL, PK, GR and ADA were higher than normal already before the r-HuEPO treatment. 3) The increases of HK and G6PD by r-HuEPO, as age dependent enzymes, may reflect the generation of young red blood cells. 4) In view of the fact that they are related to ATP production in the glycolysis cycle, we infer that increases of red blood cell enzymes by r-HuEPO may play at least some part in bringing a sensation of "well-being" to severely anemic patients undergoing hemodialysis.

We have established a new nonlymphoid leukemic cell ine from a patient with myelodysplastic syndrome (MDS), which progressed to overt leukemia. The parental cell line and a subline derived from this line have absolute dependency on several cytokines for their long-term survival and growth. The parental line designated F-36P requires granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) for continuous growth, while a subline designated F-36E can be maintained in the presence of erythropoietin (Epo) alone. When these cytokines are depleted, both the parental and the subline cells die within several days, even in medium supplemented with fetal calf serum (FCS). F-36E, maintained in the presence of Epo, constitutively synthesizes hemoglobin at a significant level. F-36P, which is usually maintained in the presence of GM-CSF or IL-3, can be induced to synthesize hemoglobin when GM-CSF or IL-3 is substituted by Epo. The surface marker profile shows that the F-36P cells are positive for the leukocyte common antigen (CD45) and some common multilineage markers such as CD13, CD33, and CD34, and negative for T- and B-cell antigens and mature myelomonocytic antigens. However, some monoclonal antibodies recognizing erythroid and platelet glycoproteins react with these cells. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in a multipotent stem cell. It is also evident that the F-36 cells can be induced to differentiate into the erythroid lineage in the presence of Epo. This, to our knowledge, is the first description of a human leukemic cell line that can be stimulated to synthesize hemoglobin by Epo.

We described a radioimmunoassay system for measuring blood erythropoietin (Epo) levels using recombinant human Epo and evaluated the regulatory mechanisms of Epo in dialysis patients. A satisfactory dose-response relationship for Epo levels was observed within the wide range of 3-250 mU/ml with a sensitivity of approximately 5 mU/ml. The Epo levels were found to be 16.1 +/- 8.6 mU/ml (m +/- SD) in 422 uremic patients on maintenance dialysis and 17.1 +/- 7.2 mU/ml in 86 normal subjects. The Epo levels were not statistically different between the two groups, although the hematocrit was significantly lower in the dialysis patients. No correlation was observed between the Epo levels and hematocrit in the dialysis patients. Patients with polycystic kidneys had higher hematocrits and Epo levels than patients with chronic nephritis. No changes in Epo levels were observed with age and with the period of dialysis. Diurnal variations in the Epo levels revealed a significant increase after hemodialysis, and an acute reduction in hematocrit following massive hemorrhage raised the Epo levels up to 3,180 mU/ml. These findings indicate that the Epo levels in dialysis patients are inappropriately low for the severity of anemia and suggest that a negative feedback mechanism of the hematocrit on the Epo secretion may exist in uremic patients as well as in normal subjects and that the threshold for Epo secretion might be 'reset' at a low hematocrit level.

In order to evaluate the possibility of using recombinant human erythropoietin (rhEpo) for the prevention and correction of anemia due to blood loss and as an adjuvant for autologous blood transfusion, its preventive and therapeutic effects were evaluated in beagles in which anemia was induced by repeated phlebotomies. Two hundred U/kg of rhEpo were administered i.v. four or nine times every two weeks for six weeks. Phlebotomies (25 ml/kg of body weight) were conducted three times at two-week intervals. rhEpo was found to successfully prevent and correct anemia caused by the phlebotomies. Concurrent administration of iron increased efficacy. The findings obtained in the present study suggest that rhEpo is useful both for the treatment of anemia caused by blood loss due to surgery and as an adjuvant therapy for pre-deposit autologous blood transfusion.

Erythropoietin (Epo) titers in various hematological states were determined by a radioimmunoassay. Epo titers in patients with uremic anemia and iron deficiency anemia were inversely correlated with their respective hemoglobin concentrations. Epo titers in patients with uremic anemia were significantly lower than those in patients with iron deficiency anemia with comparable hemoglobin concentrations.

Specific binding sites for erythropoietin (Epo) were shown in normal and anemic rat bone marrow cells using [125I]labeled human recombinant Epo. When rats were treated once or several times with phenylhydrazine or malotilate, or by phlebotomy, the serum Epo level determined by RIA began to increase rapidly. Thereafter, both the number of erythroid colony-forming unit (CFU-E)-derived colonies and the Epo binding capacity of bone marrow cells increased almost simultaneously in response to induced anemic states, suggesting that the amount of Epo binding in bone marrow cells may reflect in vivo erythropoiesis. Scatchard analysis of the binding data from normal rats revealed the presence of a single class of binding sites (Kd = 0.18 +/- 0.04 nM, 38 +/- 5 sites/cell). In anemic states, the apparent average receptor number per cell increased (52-62 sites/cell) without changing in binding affinity toward Epo. Furthermore, [125I]Epo was cross-linked to the cell surface molecule of approximately 165 kd in nonreducing conditions and 75 kd in reducing conditions. Autoradiographic analysis indicated that Epo receptors were distributed on immature erythroid cells. Proerythroblasts were the most heavily labeled, whereas orthochromatic erythroblasts and cells of myeloid and lymphoid lineages were not labeled. Calculations based on Scatchard and autoradiographic analysis showed that proerythroblasts have 390 receptor sites per cell, twice as many as basophilic or polychromatophilic erythroblasts have. These results are consistent with the stage-specific action of Epo in physiological differentiation of erythroid cells.

Erythroid progenitors were assayed in 20 chronic hemodialysis patients before and after administration of recombinant human erythropoietin (rhEpo) using a methylcellulose culture method. Hemoglobin concentrations, hematocrit values and the proportion of marrow erythroblasts increased significantly during rhEpo treatment. The numbers of erythroid progenitors (CFU-e and BFU-e) in the patients' marrow also increased following rhEpo administration. Our data suggest that rhEpo is an effective drug for treating anemia caused by chronic renal failure and the administration of rhEpo results in an increase in the numbers of erythroid progenitors.

Biologically active 125I-labeled human recombinant erythropoietin (EPO) was used to demonstrate specific receptors for this erythroid-specific hemopoietic growth factor on the cell surface of murine erythroleukemia cell clone B8. The binding of radioiodinated EPO to these cells was time and temperature dependent, specific, saturable, and reversible. During erythroid differentiation by dimethyl sulfoxide, B8 cells displayed a rapid and marked increase in the amount of specific 125I-EPO binding before the appearance of hemoglobin-containing cells. Scatchard analysis of the saturation binding data revealed that B8 cells had a single class and low number (350 to 650) of EPO receptors per cell with an apparent Kd of 1.2 to 1.4 nM. In addition, the number of EPO receptors on B8 cells was increased twice by induction with DMSO for 1 day, but the binding affinity of EPO toward its receptors did not change significantly. Affinity cross-linking experiments with disuccinimidyl suberate demonstrated two radiolabeled components with apparent molecular weights of 145,000 and 130,000 under both reducing and nonreducing conditions. Labeling of the two components was inhibited by incubation of cells with unlabeled EPO. These results suggest that some murine erythroleukemia cells potentially express EPO receptors as a differentiation marker of erythroid lineage, which contain two polypeptides with molecular weights of 109,000 and 94,000.

Erythropoietin (EPO) has a central role in the growth and development of erythroid cells. Using a biologically active radioiodinated derivative, EPO receptors were identified on fetal mouse liver cells mostly consisting of erythroid cells. 125I-EPO was cross-linked to two receptors forms with apparent molecular masses of 110 and 95 kilodaltons, respectively and both having similar affinity toward EPO.

Erythropoietin (Epo) titers in the aged (from 70 to 89 years) were determined by a radioimmunoassay. Epo levels in normal elderly subjects were not different from levels in the young volunteers. The serum Epo levels in elderly patients with anemia were inversely related to hemoglobin levels; their regression coefficient was not worse than that found in young patients. It is suggested that the reactivity of Epo production to anemia in the aged may not be worse than that reactivity in the young.

The effects of tunicamycin and neuraminidase treatment on the specific binding of 125I-erythropoietin to a murine erythroleukemia cell clone, B8, were investigated. Neuraminidase treatment of B8 cells did not affect the specific binding of erythropoietin, but tunicamycin treatment caused a 2.5 to 4-fold increase in the amount of 125I-erythropoietin binding. Scatchard analysis of the binding data showed that the increase in the amount of binding resulted from increased affinity of the receptor. These results suggest that N-linked sugars of the erythropoietin receptor protein are involved in the interaction of erythropoietin with the cell-surface receptors on B8 cells.

In vitro culture technique of bone marrow cells has been applied to study the cause of anemia in uraemic patients on maintenance haemodialysis. Incorporation of 59Fe into haem in bone marrow cells of the patients in the presence of erythropoietin, as well as the inhibitory effect of their plasma on the response of normal bone marrow cells to erythropoietin, was examined. Increase in haem synthesis rate by erythropoietin in the bone marrow cells of uraemic patients (n 14; 7.9 +/- 1.4) wasnot significantly different from that in normal bone marrow cells (n 9; 5.9 +/- 1.4,p greater than 0.05), thus indicating the presence of erythroid precursor cells with normal responsiveness to erythropoetin in uraemic patients. All the plasma from uraemic patients inhibited, in dose-dependent way, the response of normal bone marrow cells to erythropoietin. Levels of erythropoietin in the plasma samples of uraemic patients were much lower than those of the patients with iron deficiency anaemia with comparable Hb concentrations. On the basis of these results, the humoral inhibitory factor appears to play a significant role in the pathogenesis of renal anaemia, in addition to the low level of circulating erythropoietin.

The binding of recombinant erythropoietin (EPO) to fetal mouse liver cells (FMLC) was investigated using a radioiodinated derivative which retained full biological activity. FMLC were fractionated using a preformed Percoll density gradient. Using the fractionated FMLC, the ability to form CFU-E colonies in a semisolid culture was examined, and the binding of [125I]EPO was measured. The highest specific binding of [125I]EPO was observed in a fraction with a density between 1.062 and 1.076 g/ml. The same fraction showed the highest ability to form CFU-E-derived colonies. After suspension culture of FMLC with EPO for 2 days, differentiated erythroid cells with higher density markedly increased. The specific binding of [125I]EPO to these cells almost disappeared with differentiation. Scatchard analysis with cells of the CFU-E-enriched fraction showed a nonlinear curve, suggesting the existence of two classes of binding sites. One binding site was high-affinity (Kd1 = 0.41 nM), and the other low-affinity (Kd2 = 3.13 nM). These results suggest that the expression of EPO receptors on the erythroid cells is highest in CFU-E.

We have studied the internalization of 125I-erythropoietin (Epo) and regulation of Epo receptors by the ligand in a murine erythroleukemia cell clone, TSA8. To determine internalization, a high-salt acid wash was performed. Internalization of 125I-Epo was found in TSA8 cells as well as in fetal mouse liver cells (FMLC), although the percentage of internalized radioactivity reached 40% after incubation at 37 degrees C for 150 min and was lower than that in FMLC. Exposure of TSA8 cells to unlabeled Epo resulted in a rapid, time-dependent reduction in 125I-Epo binding activity. The net loss of the activity was related to the ambient Epo concentration and 5 X 10(-8)M Epo induced approximately 80% loss of total binding capacity. Scatchard analysis of the binding data revealed that the high-affinity receptor number was decreased but the affinity was increased in the Epo-treated cells. In low-affinity receptors, however, the receptor affinity was decreased and the receptor number was not changed much by preincubation with Epo. These results suggest that the decrease in 125I-Epo binding activity after preincubation with unlabeled Epo is mainly accounted for by a decrease in the number of high-affinity receptors, and the high-affinity receptors play an important role in the biological response to Epo.

Erythropoietin (EPO) titres in the serum of premature infants were determined by an in vitro method using radioiron incorporation into haem in fetal mouse liver cells in culture. The serum EPO titres in 12 premature infants at birth were significantly lower than those of normal adults. In those premature infants who developed anaemia the serum EPO titres increased significantly by 4-6 weeks after birth, confirming that EPO production increases in premature infants in early days of life.

Phase I and Phase II studies of recombinant human erythropoietin (rhEpo) were conducted in normal volunteers and in anemic patients with chronic renal failure on maintenance hemodialysis. Three hundred U/person of rhEpo was administered intravenously to healthy normal volunteers in the Phase I study, resulting in no subjective or objective changes. In the Phase II study, 66 patients with chronic renal failure on maintenance hemodialysis with less than 20% hematocrit values were treated with rhEpo in doses of 50 U/kg to 200 U/kg two or three times a week. Hematocrit values increased significantly during the 12 weeks, and the patients' conditions improved. Patients previously requiring blood transfusions became transfusion-independent during our study. There were no obvious side effects, thus indicating the safety and efficacy of rhEpo in the anemia of chronic renal failure.

We have established a novel cell line, designated as TF-1, from a patient with erythroleukemia, which showed complete growth dependency on granulocyte-macrophage colony-stimulating factor (GM-CSF) or on interleukin-3 (IL-3) and carried a homogeneous chromosomal abnormality (54X). Erythropoietin (EPO) also sustained the short-term growth of TF-1, but did not induce erythroid differentiation. These three hematopoietic growth factors acted on TF-1 synergistically. Transforming growth factor-beta and interferons inhibited the factor-dependent growth of TF-1 cells in a dose-dependent fashion, and monocyte-colony stimulating factor and interkeukin-1 enhanced the GM-CSF-dependent growth of TF-1. Ultrastructural studies revealed some very immature features in this cell line. Although TF-1 cells do not express glycophorin A or carbonyl anhydrase I, the morphological and cytochemical features, and the constitutive expression of globin genes, indicate the commitment of TF-1 to erythroid lineage. When induced to differentiate, TF-1 entered two different pathways. Specifically, hemin and delta-aminolevulinic acid induced hemoglobin synthesis, whereas TPA induced dramatic differentiation of TF-1 into macrophage-like cells. In summary, TF-1 is a cell line of immature erythroid origin that requires GM-CSF, IL-3, or EPO for its growth and that has the ability to undergo differentiation into either more mature erythroid cells or into macrophage-like cells. TF-1 is a useful tool for analyzing the human receptors for IL-3, GM-CSF, and EPO or the signal transduction of these hemopoietic growth factors.

Two distinct hemopoietic growth factors, interleukin 3 (IL-3) and erythropoietin (EPO), support the growth and development of erythroid cells in a sequential manner in vitro. Stimulation of multipotential stem cells by IL-3 appears to develop committed erythroid progenitor cells that respond to EPO. When several murine IL-3-dependent cell lines were assayed for their ability to respond to EPO, the growth and survival of the three cell lines showing the profiles of either myeloid or mast cell lineage (IC-2, DA-1, FDC-P2) were stimulated by EPO in a dose-dependent fashion. To determine whether the biologic effects were mediated through the specific receptors for EPO, we performed binding experiments on these cells with radioiodinated EPO. All of these cells displayed significant levels of specific binding for EPO. Among a family of hemopoietic growth factors, only unlabeled EPO was able to compete for the binding of radioiodinated EPO to the cells. Analysis of the binding data revealed the existence of a single case of binding sites in extremely low abundance. IC-2 cells were used to study the effects of IL-3 on the regulation of expression of EPO receptors. It was demonstrated that a decrease in IL-3 concentration in the culture medium increased the responsiveness to EPO and the amount in specific binding of EPO as well. These results suggest that some IL-3-dependent cell lines have functional EPO receptors and their expression may be modulated by IL-3.

This report describes the case of a 50-year-old male with end-stage renal failure accompanied with congenital heart disease and polycythemia. After he had received continuous ambulatory peritoneal dialysis for 1 year, he still remained polycythemic and his serum erythropoietin titer, assayed using fetal mouse liver cells, was markedly increased. An inhibitory effect on erythropoiesis was not detected by this method. Bone marrow examination showed erythroid hyperplasia. These phenomena could be explained by an overproduction of erythropoietin by the remnant kidneys or extrarenal organs, such as the liver, in response to persisting hypoxia. The patient's bone marrow was still responsive to erythropoietin.

Two types of human cancers, a renal cell carcinoma and a hepatocellular carcinoma, were investigated in vitro; both produced a marked erythrocytosis in each patient. These tumors, when transplanted into athymic nude mice, produced a remarkable erythrocytosis in the host mice. To analyze this phenomenon, the primary cultures from these xenotransplanted tumors were performed. To obtain pure tumor cell cultures, cells derived from host nude mice were eliminated by the treatment with the antiserum raised against nude mouse cells. Epithelial cells derived from each tumor attached and grew in the cultures. The conditioned media from both tumor cells revealed high erythropoietic stimulatory activities. We have characterized these erythropoietin-like activities by size-exclusion high-performance liquid chromatography. Three peaks of erythropoietin-like activities were noted after bovine serum albumin region. The molecular weights were estimated at about 55,000, 40,000, and 33,000, respectively. The results suggested that the human renal cell and hepatocellular carcinomas produced erythropoietin-like activities in vitro in culture and that erythrocytosis found in patients with cancer and in nude mice transplanted with the tumors was attributable to production of the erythropoietin-like activities by the tumor cells themselves.

An in vitro method for the determination of erythropoietin (EPO) titres in human serum samples was developed to detect low levels of EPO titres in various haematological states. Fetal mouse liver cells (FMLC) were incubated in methylcellulose-containing media, and radioiron incorporation into haem was estimated in cultured FMLC. We could determine the concentrations of EPO from around 20 to 600 mU per ml of a very small amount of serum samples from patients and normal adults. Using this method, EPO titres of normal adults (54 +/- 31 mU/ml), chronic renal failure patients (29 +/- 23 mU/ml), aplastic anaemia patients (545 +/- 74 mU/ml), and polycythaemia vera patients (16 +/- 7 mU/ml) were determined.

We have recently established a novel cell line, TF-1, from bone marrow cells of a patient with erythroleukemia, that showed an absolute growth dependency on each of three hematopoietic growth factors: erythropoietin (EPO) granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin 3 (IL-3). EPO stimulated the proliferation of TF-1 cells even at the physiologic concentration (0.03 U/mL). We performed binding experiments on TF-1 cells using radioiodinated EPO. The binding of radioiodinated EPO to TF-1 was specific, time- and temperature-dependent, and saturable. Scatchard analysis of the saturation binding data suggested the existence of a single class of binding sites (kd = 0.40 nmol/L; number of binding sites = 1,630 per cell). TF-1 cells were usually maintained in RPMI 1640 containing 10% fetal bovine serum and 5 ng/mL GM-CSF. The kd and the number of the EPO receptors were not changed by incubating the cells with IL-3, although culturing the cells in the presence of EPO resulted in down-modulation of EPO receptors. The chemical cross-linking study demonstrated that two molecules with apparent molecular weights of 105 kilodalton (Kd) and 90 Kd were the binding components of EPO. Present data suggest that human EPO receptors are very similar to the previously reported murine EPO receptors.

Clinical effect and safety of recombinant human erythropoietin (r-HuEPO) were evaluated in 66 hemodialysis patients with intractable anemia. Initially, 50U/kg dry weight (DW) of r-HuEPO was administered intravenously at the end of every hemodialysis procedure for 4 weeks, then the dosage was increased to 100 and 200U/kg DW for poor responders. The patients' hematocrits rose from 19.8 +/- 2.3% (pretreatment) to 30.2 +/- 4.9% after 12 weeks. From 206 U of blood transfusion requirement in the 3-month period before the study, only 34 U were needed after treatment. Serum iron and ferritin levels fell significantly during the study, and iron storage was considered to be one of the decisive factors in the response to r-HuEPO. Blood pressure rose in the course of r-HuEPO administration, but uncontrollable hypertension was rarely observed. There was no significant adverse effect of r-HuEPO except for this mild hypertension. These results indicate that r-HuEPO is an excellent therapeutic aid for the anemia associated with chronic renal failure.