Low concentrations of cytosine arabinoside, 6-thioguanine, actinomycin-D and aclacinomycin A stimulates the differentiation of normal human marrow myeloid progenitor cells

Myelosuppression is the major side effect of most anticancer cytotoxic drugs. Low concentrations of cytosine arabinoside (Ara-C), 6-thioguanine (6-Th), actinomycin-D (Act-D) and aclacinomycin A (ACM) have been reported to induce differentiation of leukaemic cell lines. With the proposed clinical trials of low-dosage of these four drugs, their effect on the differentiation of normal human myeloid progenitor marrow cells was studied. The four cytotoxic anticancer drugs at low concentrations stimulated normal human myeloid differentiation. Low dosage Ara-C has been used with great success in several clinical trials. The results suggest a similar therapeutic role for the other three anticancer drugs.     

Triple combination of retinoic acid + low concentration of cytosine arabinoside + hexamethylene bisacetamide induces differentiation of human AML blasts in primary culture

Differentiation induction therapy provides an alternative therapeutic approach for patients with acute myeloid leukemia (AML) who are either unsuitable for or unresponsive to conventional cytotoxic chemotherapy. The effect of a triple combination of retinoic acid (RA) + low concentration of cytosine arabinoside (Ara-C) + hexamethylene bisacetamide (HMBA) on differentiation of blasts from 24 AML patients was studied. Non-adherent mononuclear cells were seeded at a concentration of 5 x 10(5) cells per ml in 24-well tissue culture plates containing RPMI 1640 culture medium with 20 per cent fetal calf serum and 10 per cent 5637-conditioned medium and incubated with 10(-6) M retinoic acid, 10(-6) M cytosine arabinoside and/or 2 mM hexamethylene bisacetamide for six days at 37 degrees C in a humidified incubator under 5 per cent CO2. Morphological, cytochemical and functional differentiation into mature cells were induced in blasts from 22 out of the 24 AML patients following exposure to the triple combination of 10(-6) M RA + 10(-6)M Ara-C + 2 mM HMBA in primary culture. These effective results justify a clinical trial of such triple combination for AML patients who are either unsuitable for or unresponsive to conventional cytotoxic chemotherapy.     

The effects of busulphan,hydroxyurea and cytosine arabinoside on the colony forming cells in chronic granulocytic leukaemic and non leukaemic marrow

This study investigated the effects of drugs on the colony forming cells in normal marrow and in the marrow and peripheral blood of patients with CGL. Normal and CGL cells showed similar sensitivities to single doses of busulphan, but CGL cells were more sensitive than normal to hydroxyurea and did not show the characteristic plateau on the dose-response curve. The studies using ara-C indicate that, in CGL, the circulating colony forming cells are proliferating more slowly than those in the marrow.     

Retinoic acid alone and in combination with cytosine arabinoside induces differentiation of human myelomonocytic and monoblastic leukaemic cells

The effect of retinoic acid (RA) alone and in combination with cytosine arabinoside (Ara-C) on differentiation of fresh human myeloid leukaemic cells from patients with AML was studied. Cells from six patients: three with acute myelomonocytic leukaemia AMMoL and three with acute monoblastic leukaemia AMoL with a percentage of blasts greater than 70, were treated in an in vitro primary suspension culture with retinoic acid (10(-7) M), cytosine arabinoside (100 ng/ml) or both in combination. Non-adherent mononuclear cells were seeded at a concentration of 5 x 10(5) cells/ml in RPMI 1640 culture medium supplemented with 20 per cent fetal bovine serum and 10 per cent (PHA-LCM) phytohaemagglutinin leucocyte conditioned medium and incubated for 6 days at 37 degrees C in a humidified incubator containing 5 per cent CO2 in air. Morphological and functional differentiation into terminal mature elements was induced in all leukaemia cells of the six patients following exposure to the combination of both agents. These results suggest the potential usefulness of the combination of a differentiating agent (retinoic acid) and an antileukaemic drug (cytosine arabinoside) in the treatment of acute myeloid leukaemias: AMMoL and AMoL. This combination warrants a clinical trial.     

Cell differentiation and therapeutic effect of low doses of cytosine arabinoside in human myeloid leukemia

Bone marrow cells from 2 patients over 60 years of age with acute myeloblastic (AML) of monoblastic (AMoL) leukemia were cultured in the presence of a low dose of cytosine arabinoside. In the cells from the AML patient this treatment induced differentiation to metamyelocytes and a decrease in the number of blasts, so that there was an 11 -fold increase in the ratio of differentiated myeloid cells to blasts. In the patient with AMoL there was differentiation to monocytes and macrophages and only a 3-fold increase in the ratio of differentiated myeloid cells to blasts. In the latter patient actinomycin D was a more potent inducer of differentiation than cytosine arabinoside, daunomycin was similar to cytosine arabinoside and adriamycin showed the lowest response. Four courses of low dose treatment with cytosine arabinoside produced remission in the patient with AML and in another patient with AMoL whose cells were not tested in culture. No remission was induced by this low dose treatment in the patient with AMoL whose cells showed only a small decrease in blast cells in culture with cytosine arabinoside. It is suggested that prescreening for effective compounds in patients with myeloid leukemias and the use of low dose therapy can be of help in obtaining remission without serious side effects. This could be especially useful in patients where there may be severe toxic effects after high dose chemotherapy.     

Intracellular pharmacodynamic studies of the synergistic combination of 6-mercaptopurine and cytosine arabinoside in human leukemia cell lines

Selective combinations of purine and pyrimidine analogs increase remission rates in pediatric patients with relapsed leukemias. The combination of 6-mercaptopurine (6-MP) and cytosine arabinoside (ara-C) may exhibit synergism similar to that observed for fludarabine and ara-C and may diminish the potential for development of resistance since the two drugs are activated by separate enzymatic pathways. To determine the efficacy of the combination against human leukemia cells, we investigated the time-concentration relationships of the drugs given alone or in combination to the resultant cytotoxicity. To determine whether the combination leads to enhanced activity of deoxycytidine kinase (dCk), the ratelimiting enzyme in ara-C activation, we characterized the cellular dCk in CCRF/CEM/0, CCRF/CEM/ara-C/7A, and CCRF/CEM/ara-C/3A monoclonal cells before and after treatment with 6-MP. CCRF/CEM/0 (wild type), CCRF/CEM/ara-C/7A (50% ara-C-resistant as determined by ara-C sensitivity assay and dCk characterization), and CCRF/CEM/ara-C/3A (90% resistant to ara-C) human leukemia cells were incubated with various concentrations of 6-MP and ara-C given alone or in combination. Cell survival, inhibition of DNA synthetic capacity (DSC), ara-CTP anabolism, and dCk enzymatic characteristics were studied. Incubation of CEM/0 cells with 6-MP for 24 h, followed by ara-C for 48 h, increased cell-growth inhibition by approximately 0.5–1 log₁₀, corresponding to 5- to 10-fold synergism, as compared with ara-C alone after identical drug incubation in all cell lines. Simultaneous administration showed no synergism, whereas reversal of the sequence produced an antagonistic effect. The ara-CTP levels were 2-to 3.5-fold and 3- to 5-fold higher in CEM/0 and CEM/ara-C/7A cells, respectively, in cells exposed to 6-MP followed by ara-C than in those exposed to ara-C alone at the same concentrations. Furthermore, a progressive increase in ara-CTP levels was noted in CEM/0 cells exposed to increasing concentrations of 6-MP followed by 10 or 20 M ara-C. A significant decrease in DSC was observed upon treatment of wild-type and ara-Cresistant cells with 6-MP and ara-C. The combination of 6-MP and ara-C exhibits significant sequence-specific synergism in both wild-type and partially ara-C-resistant leukemia cell lines. The combination also exerts collateral sensitivity in the ara-C-resistant cell lines. 6-MP pretreatment may play a role in enhancing ara-C activation, thus producing drug synergism in sensitive and resistant leukemia cell lines.Abbreviations 6-MP 6-mercaptopurine - ara-C cytosine arabinoside - ara-CMP cytosine arabinoside monophosphate - ara-CTP cytosine arabinoside triphosphate - TIMP thioinosine monophosphate - HGPRT hypoxanthine-guanine phosphoribosyl transferase - PRPP 5-phosphoribosyl-1-pyrophosphate - AMP adenylic acid - SAMP adenylosuccinate - XMP xanthylate - TGMP thioguanylic acidDSC DNA synthetic capacity - dCk deoxycytidine kinaseRR ribonucleotide reductase - AUC area under the curvePCA perchloric acid This work was supported by the Clinical Fellowship Program, Division of Hematology/Oncology, CHLA and by the Neil Bogart Memorial Laboratories and the T.J. Martell Foundation of Cancer, Leukemia and AIDS Research     

Effect of 4-hydroperoxycyclophosphamide on leukemic and normal human myeloid progenitor cells

The sensitivity of myeloid progenitor cells from normal subjects (N-CFU-GM) and from leukemic patients in complete remission (LR-CFU-GM) to 4-hydroperoxycyclophosphamide (4-HC) were compared to the sensitivity of leukemic progenitor cells (L-CFU) to this drug. The results were expressed as the dose of 4-HC needed to kill 90% (TD 90) of the progenitor cells. The mean TD 90 were respectively for N-CFU-GM : 59 (+/- 11 S.E.M.) nM ml-1 and for L-CFU 79 (+/- 6 S.E.M.) nM ml-1. Thus, L-CFU were equally sensitive to 4-HC as N-CFU-GM. Moreover, the mean TD 90 for LR-CFU-GM was 87 (+/- 5 S.E.M.) nM ml-1. Thus, the sensitivity of N-CFU-GM and LR-CFU-GM did not differ significantly from that of L-CFU. These results are not encouraging for the use of 4-HC in vitro to eliminate the residual leukemic cells from autologous bone marrow of AML patients in complete remission. The sensitivity of L-CFU was modified neither by previous cytoreductive therapy (different from cyclophosphamide) nor by the time elapsed since diagnosis of AML.     

骨髓基质干细胞趋瘤性及神经分化潜能

目的:观察骨髓基质干细胞(bone marrow stromal cells,BMSCs)向脑胶质瘤的趋向性及在荷瘤大鼠脑内的分化,初步探讨其机制。方法:培养BMSCs后,在体外应用显微镜直接观察及Transwell试验检测BMSCs向胶质瘤细胞及血管内皮细胞生长因子(VEGF)、表皮生长因子(EGF)、碱性成纤维细胞生长因子(b-FGF)、血小板源性生长因子(PDGF)等的迁移特性,免疫荧光方法检测其在颅内向脑胶质瘤迁移的情况。在体外诱导条件下,观察BMSCs的分化;BMSCs移植到脑荷瘤大鼠脑内15 d后,免疫荧光方法检测其在体内的分化。结果:骨髓基质干细胞在体外表现出明显的向胶质瘤细胞及PDGF、EGF的迁移特性,在体内表现了明显的向脑内胶质瘤迁移的特性,并可迁移到肿瘤卫星灶周围。在体外诱导条件下BMSCs可分化为神经前体细胞(8.4%±3.5%)、神经元(53.7%±7.4%)及胶质细胞(22.3%±5.2%);在移植到荷瘤鼠脑内后,也可分化为神经前体细胞(8.3%±3.6%)、神经元(15.7%±4.3%)及胶质细胞(32.5%±7.2%),两者向神经元分化的比例存在差异(P<0.05),向神经前体细胞及胶质细胞的分化比例相似(P>0.05)。结论:骨髓基质干细胞有明显的胶质瘤趋瘤性,其向神经细胞分化的方向可能与其局部微环境有关。     

Drug resistance to 5-aza-2′-deoxycytidine, 2′,2′-difluorodeoxycytidine, and cytosine arabinoside conferred by retroviral-mediated transfer of human cytidine deaminase cDNA into murine cells

Purpose: The hematopoietic toxicity produced by the cytosine nucleoside analogs is a critical problem that limits their effectiveness in cancer therapy. One strategy to prevent this dose-limiting toxicity would be to insert a gene for drug resistance to these analogs into normal bone marrow cells. Cytidine (CR) deaminase can deaminate and thus inactivate 5-aza-2^′-deoxycytidine (5-AZA-CdR), 2^′,2^′-difluorodeoxycytidine (dFdC) and cytosine arabinoside (ARA-C). The aim of this study was to determine if gene transfer of CR deaminase into murine fibroblast cells confers drug resistance to these cytosine nucleoside analogs and if this resistance can be prevented by the CR deaminase inhibitor, 3,4,5,6-tetrahydrouridine (THU). Methods: NIH 3T3 murine fibroblast cells were transduced with retroviral particles containing the human CR deaminase cDNA. Assays measuring CR deaminase activity as well as the inhibitory action of 5-AZA-CdR, dFdC and ARA-C on colony formation, were performed in the presence of different concentrations of THU. Results: Retroviral-mediated transfer of the CR deaminase gene into 3T3 fibroblasts produced a considerable increase in CR deaminase activity. The transduced cells also showed significant drug resistance to 5-AZA-CdR, dFdC and ARA-C, as demonstrated by a clonogenic assay. This drug resistance phenotype and elevated CR deaminase activity were reversed by THU. Conclusions: These findings indicate that the CR deaminase gene can potentially be used in cancer gene therapy for protecting normal cells against the cytotoxic actions of different cytosine nucleoside analogs. In addition, the CR deaminase-transduced cells can be used as a model for screening different CR deaminase inhibitors in an intact cellular system. Received: 30 September 1997 / Accepted: 16 January 1998     

Daunorubicin, cytosine arabinoside and 6-thioguanine (DAT) combination chemotherapy for the treatment of acute non-lymphocytic leukemia.

One hundred and eight unselected patients with acute nonlymphocytic leukemia (ANLL) were treated with a combination of daunorubicin, cytosine arabinoside and 6-thioguanine (DAT). The complete remission rate was 54.6% and was achieved after an average of 2.3 courses of therapy. Among the initial variables, erythroleukemia morphology was the single most important prognostic factor, being associated with a poorer response rate (14.2%). Median remission duration was 48 weeks and median survival was 75 weeks; the estimated proportions of responders alive at 1 and 2 y from diagnosis were 71 and 35% respectively. Severe myelosuppression was the most common toxic effect observed during induction. DAT combination is an effective remission induction regimen for ANLL patients of all age groups.     

水通道蛋白1基因过表达对K562细胞红系分化和增殖的影响

目的:探讨水通道蛋白1(aquaporin-1,AQP1)过表达对人慢性髓细胞白血病(chronic myeloidleukemia,CML) K562细胞红系分化和增殖的影响.方法:以人脑cDNA文库为模板,通过PCR扩增出AQP1基因的编码序列,构建pBABE-puro-AQP1真核表达载体;感染K562细胞,筛选建立稳定过表达AQP1基因的K562细胞株(命名为K562-AQP1);实时荧光定量PCR法、细胞免疫荧光染色法及蛋白质印迹法分别检测AQP1转录和蛋白表达水平.通过MTT法检测细胞生长增殖、实时荧光定量PCR法检测γ珠蛋白表达和分光光度法检测血红蛋白含量,研究AQP1过表达对K562细胞红系分化和增殖的影响.结果:与空载体对照组相比,pBABE-puro-AQP1转染入K562细胞后AQP1 mRNA和蛋白表达水平皆有显著升高(P＜0.01),K562-AQP1细胞中红系分化指标γ珠蛋白和血红蛋白表达水平明显增加,同时细胞生长速度明显降低(P＜0.05).结论:AQP1过表达可以显著促进K562细胞向红系分化,同时抑制细胞增殖.推测AQP1可能成为临床诱导分化治疗CML的基因靶点之一.     

Effect of a combined exposure to cytosine arabinoside, bryostatin 1, and recombinant granulocyte-macrophage colony-stimulating factor on the clonogenic growth in vitro of normal and leukemic human hematopoietic progenitor cells.

We have examined the effect of a combined 24 h exposure to cytosine arabinoside (ara-C) and the protein kinase C activator bryostatin 1, either alone or in conjunction with recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), on the clonogenic growth of 14 primary samples from acute myelogenous leukemia (AML) patients, as well as normal human committed and early hematopoietic progenitors. Incubation of blasts with 1 microM ara-C and 12.5 nM bryostatin 1(+/- 1.25 ng/ml rGM-CSF) resulted in a heterogeneous pattern of inhibitory effects toward primary leukemic colonies, ranging from 32-98%, and subadditive to synergistic drug interactions. However, exposure of blasts to ara-C and bryostatin 1, either with or without rGM-CSF, eliminated leukemic cell self-renewal in 80-93% of samples, and very substantially reduced growth in the remainder. Exposure of normal human bone marrow mononuclear cells to identical concentrations of ara-C and byostatin 1 permitted the survival of 23% of committed myeloid progenitors (granulocyte-macrophage colony-forming units), and greater than 50% when rGM-CSF was included. Finally, exposure of bone marrow populations highly enriched for progenitor cells (CD34+, DR-, CD71-) to ara-C and bryostatin 1 +/- rGM-CSF for 24 h led to minimal reductions (e.g. 10-15%) in the survival of early hematopoietic progenitors (high proliferative potential colony-forming cells). Together, these findings indicate that combined exposure in vitro to ara-C and bryostatin 1, both with and without rGM-CSF, effectively inhibits the growth of leukemic cells with self-renewal capacity, while sparing a significant fraction of normal committed and primitive hematopoietic progenitors.     

Screening for induction of differentiation and toxicity to blast cells by chemotherapeutic compounds in human myeloid leukemia

Bone marrow cells from 9 patients with acute myeloid leukemia and 1 patient with a blast crisis of chronic myeloid leukemia were cultured to determine their ability to be induced to differentiate by different chemotherapeutic compounds. Five of these 10 patients showed differentiation to granulocytic and/or monocytic cells by culture with medium containing the myeloid cell differentiation-inducing protein MGI-2. Actinomycin D induced differentiation in cells from 2 of the patients who did not show differentiation with MGI-2 containing medium. In these 7 patients there was an increase in the ratio of differentiated myeloid cells to blasts. None of these 10 patients showed induction of differentiation by cytosine arabinoside, adriamycin, or daunomycin, but treatment with these compounds showed in some patients an increase in the ratio of differentiated myeloid cells to blasts. The results indicate that this ratio can be increased by differentiation and also in some patients by toxicity to blast cells. With dexamethasone or vinblastine there was no induction of differentiation and no increase in this ratio in any of the 10 patients tested. After in vivo chemotherapy with low dose cytosine arabinoside, cells from one patient showed a similar response in culture to actinomycin D as cells before chemotherapy, whereas in another patient the cells had acquired the ability to respond to actinomycin D. In contrast, after high-dose in vivo chemotherapy with cytosine arabinoside and daunomycin, cells from a third patient seemed to have lost the ability to differentiate in vitro by MGI-2 containing medium or actinomycin D. The results indicate that pre-screening for differentiation-inducing compounds and compounds that show toxicity to blast cells should be useful to select the appropriate compounds to be used for therapy, and that it is advisable to screen the cells both before and after initiation of therapy.     

A novel approach to the identification and enrichment of cancer stem cells from a cultured human glioma cell line

Enrichment of cancer stem cells for studies of carcinogenesis remains a difficult issue. We hypothesized that the unique features of cancer stem cells (CSCs) may allow formation of their colonies in vitro with distinct morphology. We therefore investigated the possibility to use morphological diversity of colonies to identify and enrich CSCs from cultured malignant human glioma cells. We found that a small proportion of the cells from a human glioma cell line U251 formed tight and round-shaped colonies in culture. Most cells in such colonies were capable of self-renewal, generating tumor spheres and differentiating into lineages with markers for neurons, astrocytes and oligodendrocytes. In addition, several neural stem cell-related genes were highly expressed by tumor cells in those tight colonies. Our results thus demonstrate a novel approach to the identification and enrichment of CSCs based on unique morphology of their colonies formed in vitro.     

骨髓成纤维样基质细胞系对急性髓细胞白血病细胞系增殖与分化影响的研究

目的：以急性髓细胞白血病（acute myeloid leukaemia,AML）细胞系为研究对象,观察正常人骨髓成纤维样细胞系（human bone marrow fibro—blastoid stromal cell line,HFCL）对急性单核细胞白血病细胞系U937、急性粒细胞白血病敏感细胞HL-60和多药耐药细胞HL-60／VCR增殖和分化的影响。方法：建立U937、HL-60和HL-60／VCR细胞与HFCL细胞的共培养模型,实验分对照组、直接接触组和transwell组。采用台盼蓝拒染法测定生长曲线;硝基四氮唑蓝（NBT）确定细胞分化;流式细胞仪检测细胞周期和CD11b、CD13、CD14和CD33细胞表面抗原进一步鉴定细胞分化;west-ernblot检测增殖细胞核抗原（PCNA）和P-糖蛋白（P-gP）的表达。结果：与HFCL细胞共培养96h后,U937、HL-60和HL-60／VCR细胞的生长受抑,且与HFCL细胞直接接触组的抑制作用大于用tr-answell组,P〈0．01。同时发现AML细胞系与HFCL细胞共培养后,G0／G1期细胞比例均增高,而S期细胞均减少,P〈0．01;尤其是直接接触组CD11b和CD14表达也均增高（P〈0．01）,CD13和CD33变化不大,NBT阳性细胞轻度增高,且差异有统计学意义。Western blot检测结果显示,3种AML细胞系PCNA表达下调;以直接接触组为甚。提示介导着白血病细胞和骨髓基质细胞间的相互作用的整合素p1（VLA-4）和p2（LFA-1）,在HFCL细胞对AML细胞生长作用影响中起着不可忽视的作用。结论：HFCL对3种具有代表性的AML细胞系U937、HL-60和HL-60／VCR有增殖抑制和诱导分化作用,除了能抑制AML细胞的生长,抑制PCNA的表达,出现G0／G1期阻滞外,还能诱导其部分向单核细胞分化。     

正常人骨髓成纤维样基质细胞对HL-60/VCR耐药细胞增殖的影响

目的观察正常人骨髓成纤维样细胞系HFCL对白血病多药耐药细胞HL-60/VCR增殖和分化的影响.方法采用四唑氮蓝(MTT)法进行HL-60/VCR细胞药物敏感实验.建立HL-60/VCR细胞和HFCL细胞共培养体系,苔盼蓝拒染法测定生长曲线;硝基四氮唑蓝(NBT)确定细胞分化;流式细胞仪检测细胞周期和CD11b、CD13、CD14、CD33细胞表面抗原进一步鉴定细胞分化;Western blot检测增殖细胞核抗原(Proliferating Cell Nuclear Antigen,PCNA)和P糖蛋白(P-glycoprotein,P-gp).结果HL-60/VCR细胞对多种药物耐药.与HFCL细胞共培养后,HL-60/VCR细胞生长受抑,且与HFCL细胞直接接触组的抑制作用＞用transwell组.同时发现HL-60/VCR细胞与HFCL细胞共培养后,G1期细胞增多,S期细胞减少;同时CD11b和CD14表达增高,CD13和CD33变化不大;且NBT阳性细胞轻度增多.Western blot检测结果显示,PCNA表达下调,以直接接触组为甚.但是P-gp表达无变化.结论正常人骨髓成纤维样细胞HFCL能抑制白血病MDR细胞HL-60/VCR的增殖,抑制PCNA的表达,出现G1期阻滞,并部分向单核细胞分化.     

ATPR对ECA-109、PANC-1、HeLa细胞增殖及分化的影响

背景与目的:由于全反式维甲酸(all-trans retinoic acid,ATRA)治疗急性早幼粒细胞白血病(acute promyelocytic leukemia,APL)存在一些不良反应,使得其进一步的临床应用受到了限制。目前,寻找具有更好疗效的维甲酸衍生物已成为研究热点。该研究旨在观察新型维甲酸衍生物4-氨基-2-三氟甲基苯基维甲酸酯(4-amino-2-trifluoromethyl-phenyl retinate,ATPR)对食管癌细胞株ECA-109、胰腺癌细胞株PANC-1、宫颈癌细胞株HeLa生长和分化的影响。方法:采用MTT法检测细胞的生长抑制率;流式细胞仪测定细胞周期的变化;酶联免疫吸符实验(ELISA)检测食管癌细胞分化指标鳞状上皮癌相关抗原SCC-Ag活性、胰腺癌细胞标志物CA199和宫颈癌细胞标志物CA125水平。结果:ATPR能够抑制肿瘤细胞增殖;并使G0/G1期细胞表达量增加,S期细胞表达量减少,细胞阻滞在G0/G1期;ECA-109中SCC-Ag活性下降,PANC-1中CA199和HeLa中CA125水平下降。结论:ATPR对上述3种实体瘤细胞株具有不同程度的诱导分化作用。     

Proliferative response of human acute myeloid leukemia cells and normal marrow enriched progenitor cells to human recombinant growth factors IL-3, GM-CSF and G-CSF alone and in combination.

The effects of human recombinant colony-stimulating factors (r-CSFs), interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) on inducing the growth of colonies derived from patients with acute myeloid leukemia (AML) (CFU-L) were investigated and compared to the proliferative response of CFU-GM derived from highly enriched normal blast cell populations. The effects of GM-CSF and IL-3 alone were similar. Both only minimally stimulated normal colonies derived from CFU-GM when compared to stimulation with MoCM (a mean of 28% of the total colonies and 17% of the colonies greater than 100 cells obtained with MoCM). Similarly, the number of leukemic colonies was substantially less than with MoCM (less than 30% of MoCM) in all but 3/10 AML patients and both were only able to significantly stimulate CFU-L derived colonies greater than 50 cells from 2/10 patients. G-CSF alone stimulated some CFU-L derived colony growth in 9/10 patients but the number stimulated was minimal relative to MoCM in five of the patients and significant stimulation of colonies greater than 50 cells occurred in only one patient. The mean number of normal CFU-GM derived colonies stimulated by G-CSF was 41% of the total colonies and 34% of the colonies greater than 100 cells generated by MoCM. The combination of G-CSF with GM-CSF and G-CSF with IL-3 resulted in a synergistic or additive increase in the number of CFU-L in 5/10 and 7/10 patients, respectively, and a synergistic increase in the size of CFU-L in 5/10. The same combinations resulted in a significant synergistic effect on size of normal CFU-GM derived colonies. There was no evidence of a synergistic increase in the number or size of CFU-L and CFU-GM derived colonies stimulated with GM-CSF in combination with IL-3. In addition, a combination of all three (G-CSF + GM-CSF + IL-3) did not enhance the effect of G-CSF + GM-CSF or G-CSF + IL-3. These results suggest that there is significant heterogeneity among AML patients in the pattern of responsiveness of the leukemic cells to the recombinant growth factors. In addition, their responsiveness does not significantly differ from that of normal progenitors. In view of the current clinical trials with r-CSFs and cytotoxic drugs in AML patients, this issue is important and worthy of further investigation.(ABSTRACT TRUNCATED AT 400 WORDS)