Phytohemagglutinin-stimulated Leukocyte-conditioned Medium Research Articles

Hypoxia alters progression of the erythroid program

Hypoxia can induce erythropoiesis through regulated increase of erythropoietin (Epo) production. We investigated the direct influence of oxygen tension (pO(2)) in the physiologic range (2-8%) on erythroid progenitor cell differentiation using cultures of adult human hematopoietic progenitor cells exposed to decreasing (20% to 2%) pO(2) and independent of variation in Epo levels. Decreases in hemoglobin (Hb)-containing cells were observed at the end of the culture period with decreasing pO(2). This is due, in part, to a reduction in cell growth and, at 2% O(2), a marked increase in cell toxicity. Analysis of the kinetics of cell differentiation showed an increase in the proportion of cells with glycophorin-A expression and Hb accumulation at physiologic pO(2). Cells were characterized by an early induction of gamma-globin expression and a delay and reduction in peak levels of beta-globin expression. Overall, fetal Hb and gamma-globin expression were increased at physiologic pO(2), but these increases were reduced at 2% O(2) as cultures become cytotoxic. At reduced pO(2), induction of Epo-receptor (Epo-R) by Epo was decreased and delayed, analogous to the delay in beta-globin induction. The oxygen-dependent reduction of Epo-R can account for the associated cytotoxicity at 2% O(2). Epo induction of erythroid transcription factors, EKLF, GATA-1, and SCL/Tal-1, was also delayed and decreased at reduced pO(2), consistent with lower levels of Epo-R and resultant Epo signaling. These changes in Epo-R and globin gene expression raise the possibility that the early increase of gamma-globin is a consequence of reduced Epo signaling and a delay in induction of erythroid transcription factors.

Effect of myelopoietic and pleiotropic cytokines on colony formation by blast cells of children with acute lymphoblastic leukemia.

The aim of this study was to see whether pleiotropic or myeloid hematopoietic growth factors, which do not stimulate normal lymphoid cells, can induce proliferation of blast cells of the acute lymphoid leukemia (ALL) of childhood. Bone marrow cells of 13 children with untreated ALL (nine common ALL, two myeloid antigen positive ALL and two early T-cell ALL) formed colonies of leukemic blast cells in primary methylcellulose cultures. Spontaneous growth was observed in three of 13 cases, whereas phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM), a conventional source of various natural human cytokines, induced colony formation in ten of 13 cases. A similar rate of responsiveness was seen with recombinant human granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF); a combination of these three cytokines induced colony formation in all cases studied. The effect of these growth factors on colony formation seemed to be dose-dependent in some cases. Of the stimuli studied, GM-CSF induced the smallest number of colonies, whereas the effects of G-CSF, SCF and PHA-LCM were similar in this respect. Combination of cytokines proved to be even more efficient in inducing clonal proliferation of leukemic lymphoblasts. In double combinations, G-CSF and GM-CSF as well as G-CSF and SCF were able to potentiate each other's effects. Triple combination of these cytokines mediated the most potent growth stimulus. Our results demonstrate that myeloid and pleiotropic cytokines are able to stimulate clonal proliferation of pediatric leukemic lymphoblasts. This may present a potential hazard to children with ALL while on adjuvant therapy with hematopoietic growth factors. In vitro colony assays performed prior to or in parallel with the administration of hematopoietic growth factors to ALL patients may help to forecast their possible effects on leukemic cells in vivo.

Expression of major blood group antigens on human erythroid cells in a two phase liquid culture system

In order to examine the sequential expression of major blood group antigens on human erythroblasts, a selective two phase liquid culture system for erythroid progenitors was established. After mononuclear cells obtained from peripheral blood were cultured in the presence of phytohemagglutinin stimulated-leukocyte conditioned medium (PHA-LCM) for 7 days (the first phase), nonphagocytic cells were recultured under hypoxic culture conditions containing 30% fetal calf serum, 1% bovine serum albumin, 300 micrograms/mL transferrin and 2 U/mL recombinant erythropoietin (the second phase). Mature (orthochromatic) erythroblasts were observed on day 4 of the second phase, and reached 57.1 +/- 3.1% of total cells on day 8, followed by the appearance of denucleated red cells, equivalent to mature red cells in peripheral blood. Hemoglobin contents reached the level of 16.8 +/- 0.7 micrograms/10(6) cells on day 8. Flow cytometric analyses revealed that, on day 3 of the second phase, cells became blood type M-positive, corresponding to the maturation of erythroid cells. Regarding the expression of ABH blood group antigens, a small number of blood type H- positive cells were initially detected on day 0 of the second phase, while blood type A-positive cells, which essentially were not observed on day 0, increased gradually corresponding to the extent of erythroid maturation. In the present system, Lewis and P1 blood group antigens were expressed at day 5 of the second phase, although autologous plasma was required to determine the expression of Lewis blood group antigens. This culture system is beneficial for studies on normal and abnormal human red cell membranes, because the erythroid progenitors in human peripheral blood were used, and a reasonable number of erythroid cells (0.5 to 1.5 x 10(7] was obtained with good maturation.

Expression of Major Blood Group Antigens on Human Erythroid Cells in a Two Phase Liquid Culture System

In order to examine the sequential expression of major blood group antigens on human erythroblasts, a selective two phase liquid culture system for erythroid progenitors was established. After mononuclear cells obtained from peripheral blood were cultured in the presence of phytohemagglutinin stimulated-leukocyte conditioned medium (PHA-LCM) for 7 days (the first phase), nonphagocytic cells were recultured under hypoxic culture conditions containing 30% fetal calf serum, 1% bovine serum albumin, 300 micrograms/mL transferrin and 2 U/mL recombinant erythropoietin (the second phase). Mature (orthochromatic) erythroblasts were observed on day 4 of the second phase, and reached 57.1 +/- 3.1% of total cells on day 8, followed by the appearance of denucleated red cells, equivalent to mature red cells in peripheral blood. Hemoglobin contents reached the level of 16.8 +/- 0.7 micrograms/10(6) cells on day 8. Flow cytometric analyses revealed that, on day 3 of the second phase, cells became blood type M-positive, corresponding to the maturation of erythroid cells. Regarding the expression of ABH blood group antigens, a small number of blood type H-positive cells were initially detected on day 0 of the second phase, while blood type A-positive cells, which essentially were not observed on day 0, increased gradually corresponding to the extent of erythroid maturation. In the present system, Lewis and P1 blood group antigens were expressed at day 5 of the second phase, although autologous plasma was required to determine the expression of Lewis blood group antigens. This culture system is beneficial for studies on normal and abnormal human red cell membranes, because the erythroid progenitors in human peripheral blood were used, and a reasonable number of erythroid cells (0.5 to 1.5 x 10(7] was obtained with good maturation.

Colony Stimulating Activities of GM-CSF, G-CSF and IL-3 on Blast Progenitors from Acute Myeloblastic Leukemia.

The colony stimulating activities (CSAs) of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), recombinant granulocyte colony-stimulating factor (rG-CSF) and recombinant interleukin-3 (rIL-3) on blast cells from various types of acute myeloblastic leukemia (AML) patients were studied using an in vitro blast colony assay. The stimulatory magnitude of rGM-CSF was highest in type M4 blasts but almost non-existent in type M1 blasts. Some preferential stimulatory action of rG-CSF was observed in type M2, M4 blasts and in overt leukemia in patients with refractory anemia with excess of blasts. On the other hand, the stimulatory activity of rIL-3 did not differ much with the AML subtype. Exposure to rGM-CSF, rG-CSF or rIL-3 did not alter the cellular phenotype or morphology of the leukemic blasts or the self-renewal capacity of blast progenitors. Simultaneous addition of rGM-CSF, rG-CSF and rIL-3, in various combinations, produced variable results and a simple additive effect was seen in 40% of the cases studied and either a significantly larger or smaller value in the remaining cases. Recombinant GM-CSF, rG-CSF and rIL-3 when added together did not reconstitute CSA of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM).

Cryopreservation of human megakaryocytic progenitor cells (CFU-MK): Influence of culture conditions

The survival of human megakaryocytic progenitor cells (CFU-MK) after freezing using a two-step cooling technique was studied in a methylcellulose culture system, using different stimulating activities and their combinations. The best growth stimulating activity for CFU-MK was found in plasma from aplastic patients (PAP). PAP was roughly three times more potent than optimal doses of human recombinant interleukin 3 (IL3), itself two times more active than our batch of phytohemagglutinin stimulated leukocyte conditioned medium (PHA-LCM). The addition of erythropoietin (EPO) to PHA-LCM doubled the number of megakaryocytic colonies, but had no effect on the number of CFU-MK stimulated by IL3. Of the two batches of PAP used, one was optimal and the other was significantly improved by the addition of PHA-LCM. The percentage recovery of CFU-MK after freezing reached 70 to 80% in cultures stimulated by PHA-LCM and IL3 ± EPO, and 58% in PAP-supplemented cultures. However, this last value was not significantly different from the previous ones. The percentage recovery of CFU-MK in each condition tested was similar to that obtained with the other myeloid progenitors, CFU-GM and BFU-E. However, the high CFU-MK stimulating activity of PAP is hindered by its high variability and shortage in supply. Thus it seems more appropriate to recommend the use of recombinant human IL3 because of its easily standardizable and consistent CFU-MK Stimulating activity.

Cytogenetic evidence of clonal proliferation of leukemic progenitor cells from patients with acute promyelocytic leukemia (APL)

We have studied in-vitro growth of leukemic progenitor cells (L-CFU) in ten patients with acute promyelocytic leukemia (APL). All patients showed consistently an extraordinarily high incidence of cluster formation under the stimulation of human placental conditioned medium (HPCM) and/or phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM). Cytogenetic analyses of clusters or colonies disclosed the presence of a 15;17 translocation. These findings may represent the close relationship between specific chromosomal aberration, t(15;17), and the growth pattern of L-CFU of APL in vitro.

Megakaryocytopoiesis in polycythemia vera: characterization by megakaryocytic progenitors (CFU-Meg) in vitro and quantitation of marrow megakaryocytes.

Megakaryocytopoiesis in polycythemia vera (PV) was characterized by in vitro growth of marrow megakaryocytic progenitors (CFU-Meg) and quantitation of megakaryocyte numbers in marrow biopsy specimens in 14 patients with PV. Megakaryocyte numbers and CFU-Meg numbers in the 14 patients were variable, with values from the control range to markedly increased numbers. Nine of the 14 patients showed spontaneous CFU-Meg growth, and the presence or absence of spontaneous CFU-Meg growth was found to be related to the degree of marrow megakaryocyte increase, i.e., those with spontaneous CFU-Meg had higher megakaryocyte numbers. None of the plasmas from the PV patients contained detectable levels of megakaryocyte colony-stimulating activity (Meg-CSA), assayed using the culture with nonadherent normal marrow cells and tested plasma without phytohemagglutinin-stimulated leukocyte-conditioned medium as an exogenous source of Meg-CSA. Increased megakaryocyte numbers and resultant thrombocytosis in PV are likely based on the abnormal population of CFU-Meg.

Phytohemagglutinin-stimulated leukocyte-conditioned medium induces differentiation in acute promyelocytic leukemia cells in vitro

Six-day cultures of FCS and PHA-LCM-stimulated whole blood from a patient with acute promyelocytic leukemia (APL) were examined for differential cell count and chromosome karyotypes. It was found that both FCS and PHA-LCM could induce partial leukemic cell differentiation and maturation to macrophage in vitro, while PHA-LCM caused lymphocyte proliferation too. The absolute number of atypical blasts and neutrophils decreased in all 6-day cultures. The majority of the dividing cells (81.4%) contained the characteristic translocation for APL, t(15; 17) (q22; q11). Thus, these were members of the leukemic myeloid lineage, whereas some cells contained normal karyotypes, which could be lymphocytes.

Differentiation of Blast Cells From a Down’s Syndrome Patient With Transient Myeloproliferative Disorder

A male neonate with Down's syndrome and congenital myeloproliferative disorder was studied. His blood picture showed the unique coexistence of leukocytosis with matured cells and a large number of blast cells. The in vitro proliferation and differentiation of blast cells into various lineages in the presence of phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM) was examined by using a liquid culture and a methylcellulose culture system. The differentiation of blast cells into myeloid cells was confirmed by specific cytochemical stainings, electron microscopy, and an immunologic study. No specific factors in the plasma of the patient promoted the proliferation or differentiation of blast cells. The cellular composition of colonies grown in methylcellulose culture from single blast cells was studied by a micromanipulation technique. High plating efficiency was observed. Of 136 cultures, 78 showed colony growth. Half of the blast cells were colony-forming cells that could proliferate and differentiate into basophils, neutrophils, eosinophils, macrophages, and erythrocytes in the presence of PHA-LCM. Using the blast cells with a high differentiation capacity to the basophil pathway, we studied the effect of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF). Recombinant GM-CSF support neutrophils, eosinophils, and macrophages but not typical basophils. These findings of the cell differentiation of blast cells into various kinds of cells in vitro were in agreement with the finding of neutrophilia, eosinophilia, basophilia, and thrombocythemia in this patient.

Differentiation of blast cells from a Down's syndrome patient with transient myeloproliferative disorder

A male neonate with Down's syndrome and congenital myeloproliferative disorder was studied. His blood picture showed the unique coexistence of leukocytosis with matured cells and a large number of blast cells. The in vitro proliferation and differentiation of blast cells into various lineages in the presence of phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM) was examined by using a liquid culture and a methylcellulose culture system. The differentiation of blast cells into myeloid cells was confirmed by specific cytochemical stainings, electron microscopy, and an immunologic study. No specific factors in the plasma of the patient promoted the proliferation or differentiation of blast cells. The cellular composition of colonies grown in methylcellulose culture from single blast cells was studied by a micromanipulation technique. High plating efficiency was observed. Of 136 cultures, 78 showed colony growth. Half of the blast cells were colony-forming cells that could proliferate and differentiate into basophils, neutrophils, eosinophils, macrophages, and erythrocytes in the presence of PHA-LCM. Using the blast cells with a high differentiation capacity to the basophil pathway, we studied the effect of recombinant granulocyte-macrophage colony-stimulating factor (GM- CSF). Recombinant GM-CSF support neutrophils, eosinophils, and macrophages but not typical basophils. These findings of the cell differentiation of blast cells into various kinds of cells in vitro were in agreement with the finding of neutrophilia, eosinophilia, basophilia, and thrombocythemia in this patient.

Leukemic Blast Cell Colony Formation in Semisolid Culture With Erythropoietin: A Case Report of Acute Poorly Differentiated Erythroid Leukemia

The bone marrow of a patient with acute undifferentiated leukemia developed unique colonies after a 14-day culture in erythropoietin (EPO)-containing methylcellulose. The colonies consisted of 20 to 200 nonhemoglobinized large blast cells. Cytogenetic analysis of single colonies revealed hypotetraploid karyotypes with several marker chromosomes that were identical to those found in directly sampled bone marrow. The concurrently formed erythroid bursts showed only normal karyotypes. No leukemic colony formation was observed in other culture systems with either colony-stimulating activity (CSA) or phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). The leukemic colonies exhibited a complete EPO-dose dependency similar to that of the patient's normal BFU-E. Although cytochemical and immunologic marker studies of the bone marrow cells failed to clarify the cell lineage of the leukemic cells with extraordinarily large cell size, ultrastructural study revealed erythroid differentiation such as siderosome formation in the cytoplasm and ferritin particles in the rhophecytosis invaginations. These findings indicate that the patient had poorly differentiated erythroid leukemia and that some of the clonogenic cells might respond to EPO in vitro. Corresponding to this biological feature, the leukemic cells were markedly decreased in number in response to repeated RBC transfusions, and partial remission was obtained. These observations suggest that erythroid leukemia distinct from erythroleukemia (M6) with a myeloblastic component, can develop as a minor entity of human acute leukemia.

Leukemic blast cell colony formation in semisolid culture with erythropoietin: a case report of acute poorly differentiated erythroid leukemia

The bone marrow of a patient with acute undifferentiated leukemia developed unique colonies after a 14-day culture in erythropoietin (EPO)-containing methylcellulose. The colonies consisted of 20 to 200 nonhemoglobinized large blast cells. Cytogenetic analysis of single colonies revealed hypotetraploid karyotypes with several marker chromosomes that were identical to those found in directly sampled bone marrow. The concurrently formed erythroid bursts showed only normal karyotypes. No leukemic colony formation was observed in other culture systems with either colony-stimulating activity (CSA) or phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). The leukemic colonies exhibited a complete EPO-dose dependency similar to that of the patient's normal BFU-E. Although cytochemical and immunologic marker studies of the bone marrow cells failed to clarify the cell lineage of the leukemic cells with extraordinarily large cell size, ultrastructural study revealed erythroid differentiation such as siderosome formation in the cytoplasm and ferritin particles in the rhophecytosis invaginations. These findings indicate that the patient had poorly differentiated erythroid leukemia and that some of the clonogenic cells might respond to EPO in vitro. Corresponding to this biological feature, the leukemic cells were markedly decreased in number in response to repeated RBC transfusions, and partial remission was obtained. These observations suggest that erythroid leukemia distinct from erythroleukemia (M6) with a myeloblastic component, can develop as a minor entity of human acute leukemia.

Megakaryocytic colony formation (CFU-Meg) in essential thrombocythemia: quantitative and qualitative abnormalities of bone marrow CFU-Meg.

For the purpose of examining the mechanisms for the overproduction of megakaryocytes and platelets in essential thrombocythemia (ET), marrow megakaryocytic colony-forming units (CFU-Meg) were characterized using a methylcellulose culture system in nine patients with ET, and they were compared with those of 16 control subjects and four patients with secondary thrombocytosis (ST). The number of CFU-Meg per 10(5) cells in ET was significantly higher (p less than .001) than that in the controls (5.8 times of the controls) or that in ST. ET showed endogenous CFU-Meg (58 +/- 16% of the total CFU-Meg) that could form megakaryocytic colonies without phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM) as a source of Meg-CSA. The controls and the patients with St revealed no endogenous CFU-Meg. The dose-response studies with PHA-LCM revealed that CFU-Meg from ET are highly sensitive to low concentrations of PHA-LCM compared to CFU-Meg from the control and ST. Erythropoietic burst-forming units (BFU-E) were monitored as a control progenitor, because the patients with ET studied did not have erythrocytosis. Although five out of nine patients with ET had endogenous BFU-E, the percentages of endogenous BFU-E were small (4-10%). The number of BFU-E in ET was not different from the control value. Thus, ET is associated with an enlarged CFU-Meg compartment that shows abnormal growth patterns when cultured in vitro, while the growth abnormality of BFU-E is small, which may underlie the hematological features of ET. The culture of CFU-Meg should be clinically useful for differentiating ET from ST.

Studies of human megakaryocytopoiesis using an anti-megakaryocyte colony-stimulating factor antiserum.

We produced an antiserum by immunizing rabbits with purified human megakaryocyte colony stimulating factor (Meg-CSF). With the use of an anti-Meg-CSF IgG fraction (AM-IgG), we detected immunoreactive Meg-CSF both in human aplastic anemia serum (AAS) and normal serum. Based on our immunological and biological analyses, Meg-CSF appeared to be antigenically as well as functionally distinct from human urinary erythropoietin (EPO) and thrombopoietic stimulating factor. The AM-IgG fraction was able to suppress the ability of both aplastic anemia serum and purified Meg-CSF to promote megakaryocyte colony formation. In addition, the supernatant formed after immune precipitation of the AAS with AM-IgG no longer possessed Meg-CSF-like activity. The AM-IgG did not suppress the ability of EPO, phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM), or PHA-LCM + EPO to promote erythroid, granulocyte-macrophage, or mixed colony formation, respectively. The use of this antibody has further defined the dependency of human megakaryocytopoiesis on Meg-CSF.

Characterization of reticulofibroblastoid colonies (CFU-RF) derived from bone marrow and long-term marrow culture monolayers.

The maintenance of hemopoietic precursors in long-term liquid bone marrow cultures (LTBMC) is associated with the presence of an adherent stromal layer composed of heterogeneous cell populations. We have used a culture assay to promote the growth of one of its cellular components and characterize its properties. Freshly obtained bone marrow cells and cells derived from the adherent layer of LTBMC were grown in methylcellulose-clotted plasma in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM), hydrocortisone (HC), and citrated normal human plasma. Both sources contained cells (CFU-RF) that gave rise to colonies of cells with a reticulofibroblastoid appearance. In the presence of HC, most colonies contained lipid-laden cells. Colonies could be further propagated as adherent layers when transferred into liquid cultures. These cells produced laminin, fibronectin, and collagen types I, III, IV, and V. They were negative for Von Willebrand factor VIII. The ability to synthesize laminin and collagen type IV distinguished these cells from a population of previously described bone marrow fibroblasts (CFU-F). The relationship of CFU-RF to hemopoietic precursors was investigated using patients with chronic myeloid leukemia and bone marrow transplant recipients. Cells within CFU-RF-derived colonies were uniformly negative for the Philadelphia chromosome, thus making it unlikely that they belonged to the malignant hemopoietic clone. CFU-RF-derived colonies in bone marrow transplant recipients were found to be exclusively of host origin. Both observations support the view that CFU-RF is not part of the repertoire of hemopoietic stem cells.

Clonal analysis of basophil differentiation in bone marrow cultures from a Down's syndrome patient with megakaryoblastic leukemia

We present the in vitro differentiation of marrow cells from a patient with Down's syndrome accompanied by megakaryoblastic leukemia into basophils in the presence of phytohemagglutinin-stimulated leukocyte conditioned medium, using a liquid culture and methylcellulose culture system. Identification of basophils was established by metachromatic staining with toluidine blue, transmission electron microscopy, and the presence of histamine. However, these basophils did not release histamine in response to calcium ionophore or chemotactic peptide. Samples from suspension cultures that contained 90% basophils showed chromosomal markers characteristic of leukemic cells (48, XY, +11, +21, t(1;15)) in all examined mitoses. The cellular composition of leukemic colonies grown in methylcellulose culture from single cells was studied using the micromanipulation technique. High plating efficiency and extreme predominance of basophil colonies were observed. In a total 137 cultures, 79 revealed colony growth. Of 59 colonies that were analyzed by cytologic examination, 46 were pure basophil colonies. These basophil colonies showed disperse morphology, similar to that of a normal basophil colony. The clonality of the basophil colonies and skewing of lineage expression were documented from leukemic single-cell cultures. These data showed that leukemic cells have the capacity for differentiation into some lineages that are not expressed in vivo.

Clonal Analysis of Basophil Differentiation in Bone Marrow Cultures From a Down’s Syndrome Patient With Megakaryoblastic Leukemia

We present the in vitro differentiation of marrow cells from a patient with Down's syndrome accompanied by megakaryoblastic leukemia into basophils in the presence of phytohemagglutinin-stimulated leukocyte conditioned medium, using a liquid culture and methylcellulose culture system. Identification of basophils was established by metachromatic staining with toluidine blue, transmission electron microscopy, and the presence of histamine. However, these basophils did not release histamine in response to calcium ionophore or chemotactic peptide. Samples from suspension cultures that contained 90% basophils showed chromosomal markers characteristic of leukemic cells (48, XY, +11, +21, t(1;15)) in all examined mitoses. The cellular composition of leukemic colonies grown in methylcellulose culture from single cells was studied using the micromanipulation technique. High plating efficiency and extreme predominance of basophil colonies were observed. In a total 137 cultures, 79 revealed colony growth. Of 59 colonies that were analyzed by cytologic examination, 46 were pure basophil colonies. These basophil colonies showed disperse morphology, similar to that of a normal basophil colony. The clonality of the basophil colonies and skewing of lineage expression were documented from leukemic single-cell cultures. These data showed that leukemic cells have the capacity for differentiation into some lineages that are not expressed in vivo.

Production of Leukemic Blast Growth Factor by a Human Bladder Carcinoma Cell Line

AbstractCirculating blast cells from the peripheral blood of acute myeloblastic leukemia patients include a subpopulation capable of colony formation in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). We describe the complete replacement in the blast assay of PHA-LCM by conditioned medium from a human bladder carcinoma cell line, HTB9. Both conditioned media contain a stimulator of blast cell growth that elutes as a single peak from a Sephadex G100 column with an apparent molecular weight of 30,000. It is shown that this leukemic blast growth factor is distinct from erythroid-potentiating activity (EPA) and possibly granulocyte macrophage colony-stimulating factor.

Production of leukemic blast growth factor by a human bladder carcinoma cell line

Circulating blast cells from the peripheral blood of acute myeloblastic leukemia patients include a subpopulation capable of colony formation in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). We describe the complete replacement in the blast assay of PHA-LCM by conditioned medium from a human bladder carcinoma cell line, HTB9. Both conditioned media contain a stimulator of blast cell growth that elutes as a single peak from a Sephadex G100 column with an apparent molecular weight of 30,000. It is shown that this leukemic blast growth factor is distinct from erythroid-potentiating activity (EPA) and possibly granulocyte macrophage colony-stimulating factor.