IL-6诱导小鼠骨髓中性粒细胞中MMP-9的生成与释放的实验

目的 探讨IL-6诱导小鼠骨髓中性粒细胞（PMN）生成和释放基质金属蛋白酶-9（MMP-9）的作用及激活途径。方法 分离小鼠骨髓PMN,将其分为空白对照组、IL-6刺激组、IL-6+DMSO组、IL-6+STAT3抑制剂Ⅷ组。实时荧光定量聚合酶链式反应检测细胞内MMP-9 mRNA表达,明胶酶谱检测PMN释放的MMP-9活性,Western blot检测PMN中STAT3蛋白磷酸化改变。结果 IL-6刺激后,PMN中MMP-9 mRNA水平明显升高（P=0.0050）,明胶酶谱检测的释放到胞外MMP-9活性明显高于对照组（P=0.0087）,IL-6刺激后PMN中STAT3磷酸化水平明显升高（P=0.0089）。在IL-6作用时加入特异性STAT3抑制剂Ⅷ后,MMP-9 mRNA水平、培养上清液中MMP-9活性以及PMN中磷酸化STAT3蛋白水平与IL-6刺激组相比均明显下降（P=0.0067, 0.048和0.0098）。结论 IL-6刺激骨髓PMN中MMP-9的生成和释放,该作用可能是通过诱导STAT3信号通路磷酸化实现的。     

NLRP3 Promotes Glioma Cell Proliferation and Invasion via the Interleukin-1b/NF-kB p65 Signals

Because of the characteristics of high invasiveness, relapse, and poor prognosis, the management of malignant gliomas has always been a great challenge. Nod-like receptor (NLR) family pyrin domain containing 3 (NLRP3) is a crucial component of the NLRP3 inflammasome, a multiprotein complex that can trigger caspase 1/interleukin-1 (IL-1)-mediated inflammatory response once activated and participates in the pathogeny of diverse inflammatory diseases as well as cancers. We examined the function of NLRP3 in the development of glioma. Glioma cells were treated with NLRP3 interference or overexpression vectors, recombinant IL-1 , IL-1 antibody, and NF- B inhibitor. Cell proliferation and invasion were assessed by CCK-8 and Transwell assays. Gene expression was detected by PCR, Western blot, and ELISA. NLRP3 and NF- B p65 increased and were positively correlated in glioma tissues. NLRP3 knockdown suppressed glioma cell growth and invasion with the decrease of IL-1 and NF- B p65. Conversely, forced expression of NLRP3 promoted cell growth. NLRP3 silencing suppressed ectogenous IL-1 -elevated cell proliferation and invasion, whereas IL-1 elimination impaired the proproliferation effect of NLRP3 hyperexpression. Furthermore, NF- B blockage abrogated IL-1 and NLRP3 hyperexpression increased cell growth and invasion. NLRP3 promoted the growth and invasion of gliomas via the IL-1 /NF- B p65 signals.     

In vivo DNA cross-linking by cyclophosphamide: comparison of human chronic lymphatic leukemia cells with mouse L1210 leukemia and normal bone marrow cells

Alkaline elution was done on a variety of cells following cyclophosphamide (CY) treatment in vivo. Cells used were L1210 leukemia, normal mouse bone marrow, and peripheral blood cells obtained from a patient with chronic lymphatic leukemia (CLL). Endpoints used were determination of single strand breaks, DNA-DNA interstrand and DNA-protein cross-links. After treatment of mice with CY (4 mg/mouse), low levels of single strand breaks were observed in both L1210 leukemia and CDF1 normal bone marrow. When a patient with CLL was treated with CY (750 mg/m2), no evidence of single strand breaks could be demonstrated. Maximum levels of DNA-DNA interstrand cross-links were observed in mice 2 h after injection of CY for the L1210 leukemia cells [175 +/- 25 rad-equivalents (req)] and at 4 h for the CDF1 normal bone marrow cells (47 +/- 9 req). In human CLL, maximum levels were observed 12 h after injection of CY. Peak levels of DNA-DNA interstrand cross-links were approximately 4-fold lower in CDF1 normal bone marrow cells than in L1210 leukemia. The frequencies measured in human CLL cells were relatively low at any timepoint (mean at 12 h = 36 req). Maximum levels of DNA-protein cross-links were observed 4 h after injection of CY (4 mg/mouse) for both L1210 leukemia [123 req (mean)] and normal bone marrow cells [50 req (mean)]. DNA-protein cross-links were measurable in CLL at timepoints later than 4 h after the start of injection of CY. In order to obtain equitoxicity between L1210 leukemia and CDF1 normal bone marrow cells, about 18-fold higher doses of CY had to be given than in the case of the normal bone marrow cells. In contrast, only 4-fold higher doses had to be given to the normal bone marrow to obtain equivalent peak levels of DNA-DNA interstrand cross-links.     

Suppression of mast cell colony formation by a low molecular weight fraction of fetal calf bone marrow extract

A semi-purified fraction extracted from fetal calf bone marrow was previously shown to contain a tetrapeptide N-Ac-Ser-Asp-Lys-Pro which inhibits in mice, hematopoietic stem cell entry into the cell cycle. This peptide however, did not exhibit any effect on either IL-3 nor GM-CSF dependent cell growth. We report herein that a semi-purified fraction also contains another activity which is antagonistic to IL-3. Addition of the fraction in vitro decreased IL-3 dependent mast cell colony formation. Growth of IL-3 dependent cell lines (DA-1 and FDC-P2) was also suppressed. No effect was observed in the same dose range on granulocyte-macrophage colony formation nor on IL-3 independent cell growth.     

Suppression of marrow stromal cells and microenvironmental damage following sequential radiation and cyclophosphamide

Persistent defects in marrow stroma may contribute to hemopoietic insufficiency in patients treated with combined modality therapy for malignancy. To assess the bone marrow failure following combined therapy, mice received intraperitoneal administration of four weekly doses of cyclophosphamide, 160 mg/kg (CY) one week after 1500 rad leg irradiation (LI). This treatment inhibited repopulation of endogenous nucleated cells to less than 60% of normal at one, two, four and six months post-irradiation. Leg irradiation alone suppressed the repopulation to about 75% of normal and cyclophosphamide alone suppressed to 80% of normal. Normal body weight and recovery of peripheral leukocytes and hematocrit to normal levels demonstrated the localized nature of the lesion. Differential marrow counts revealed that 1500 rad LI + CY suppressed erythroblasts, myeloid, and lymphoid cells more than either modality alone. To directly assess the damage of sequential 1500 rad LI + CY on the microenvironment, marrow stromal cells were flushed from the femoral marrow and cultured as adherent cell colonies. They were suppressed to less than 30% of normal for three months following combined modality treatment. Other progenitors, granulocyte-macrophage and spleen colony forming units (CFU-C and CFU-S respectively), were suppressed but exhibited different patterns of partial recovery. We conclude that multiple courses of cyclophosphamide starting one week after 1500 rad LI produced persistent damage to the microenvironment reflected by decreased marrow stromal cells and failure of hemopoietic cells and their progenitors to completely repopulate femoral marrow.     

Hierarchical regulation of interleukin production: Induction of interleukin 6 (IL-6) production from bone marrow cells and marrow stromal cells by interleukin 3 (IL-3)

IL-3 stimulated the production of IL-6 from a bone marrow-adherent cell population, macrophages and from hemopoietic supportive stromal cell lines. It also induced IL-6 production from a stem cell-enriched population of bone marrow cells which did not produce IL-6 without stimulation. In contrast, stimulation with IL-6 of all the cell populations studied in the present experiments did not induce IL-3 production. These results indicate a hierarchical network in the regulation of interleukin production, and existence of a positive feedback mechanism; IL-3 induces IL-6 production which in turn stimulates stem cells into cycle and induces stem cells to respond to IL-3.     

STAT3 activation by IL-6 from mesenchymal stem cells promotes the proliferation and metastasis of osteosarcoma

We previously demonstrated that human mesenchymal stem cells (MSCs) promote the growth of osteosarcoma in the bone microenvironment. The aim of the present study was to further determine the effect of IL-6/STAT3 signaling on the progression of osteosarcoma. First, conditioned medium from MSCs was used to stimulate the growth of osteosarcoma cells (Saos-2) in vitro. We found that STAT3 was activated and that the activation could be blocked by an IL-6-neutralizing antibody. The inhibition of STAT3 in Saos-2 cells by siRNA or AG490 decreased cell proliferation, migration and invasion, down-regulated the mRNA expression of Cyclin D, Bcl-xL and Survivin and enhanced the apoptotic response. Furthermore, a nude mouse osteosarcoma model was established by injecting luciferase-labeled Saos-2 cells into the tibia, and the effect of STAT3 on tumor growth was determined by treating the mice with AG490. In vivo bioluminescence images showed that tumor growth was dramatically reduced in the AG490 group. In addition, STAT3 inhibition decreased the lung metastasis rate and prolonged the survival of these mice. After treatment with AG490, the protein levels of IL-6, p-STAT3 and PCNA were decreased, and the level of apoptosis in the tumor was increased. Altogether, these data indicate that MSCs in the bone microenvironment might promote the progression of osteosarcoma and protect tumor cells from drug-induced apoptosis through IL-6/STAT3 signaling.     

EGF-IL-18 fusion protein as a potential anti-tumor reagent by induction of immune response and apoptosis in cancer cells

We report here the generation and characterization of EGF-IL-18 fusion protein as an anti-tumor reagent. The epidermal growth factor (EGF) and interleukin-18 (IL-18) fusion protein was shown to induce interferon-γ (IFNγ) expression and secretion in KG-1 cells, and to promote PBMNC proliferation. It also stimulated activation of CD4⁺ T cells, and increased other immune responses. Moreover, EGF-IL-18 could induce significant tumor regression in SMMC-7721-xenografted Balb/c nude mice when administered together with peritumoral injection of X-ray-irradiated NK-92 cells, and this regression is associated with arresting of the tumor cells in G1 phase and induction of apoptosis.     

Effects of a Combination of Cyclophosphamide and Human Recombinant Interleukin 2 on Pulmonary Metastasis after the Surgical Removal of a 3-Methylcholanthrene-induced Primary Tumor in Autochthonous Mice

We have investigated the therapeutic effects of a combination of cyclophosphamide (CY, 150 mg/kg, iv) and human recombinant interleukin 2 (IL-2, 5 × 10⁴ JU/day, ip for 5 days) on autochthonous tumors induced in mice by 3-methylcholanthrene. The initial treatment was carried out when the tumor had reached 8 to 10 mm in diameter. Twenty-eight out of 35 mice (80%) died of local recurrence and pulmonary metastasis of tumor cells within 53 × 40 days (mean survival time, MST × SD) after the surgical removal of the primary tumor. When these mice were treated with both CY and IL-2 following the operation (Op), only 10 out of 20 mice (50%) died of recurrence and metastasis. The survival rate, however, was not improved by CY chemotherapy alone or IL-2 immnnotherapy alone, although each provided a prolongation of the MST. Natural killer cell and LAK precursor cell activities in the spleen cells from the treated mice were found to be restored by IL-2 alone or CY + IL-2, whereas they were suppressed by CY alone. These findings reveal that the restoration of the antitumor activity of spleen cells does not provide an improved therapeutic effect by itself and that IL-2 immunotherapy requires the associated effect of CY chemotherapy to achieve an improved therapeutic effect.     

IL-3基因修饰的骨髓基质细胞辅助大剂量化疗后造血功能恢复

为研究基因治疗在造血功能损伤后恢复中的应用,本课题以携带小鼠IL-3基因的复制缺陷型重组腺病毒载体转染骨髓基质细胞,对大剂量化疗后的小鼠进行脾内移植观察造血功能的恢复情况.结果表明,缺陷型腺病毒载体能有效地转染小鼠原代骨髓基质细胞,转染效率在80%以上(MOI=10);基因修饰的骨髓基质细胞体外分泌IL-3的水平可达110U/ml/10~6细胞/24小时;在大剂量环磷酰胺治疗后脾内移植IL-3基因修饰的基质细胞能有效地升高实验小鼠外周血白细胞总数;病理检测发现IL-3基因修饰的基质细胞治疗组小鼠脾脏和骨髓中细胞增生较其它组明显活跃;经IL-3基因修饰的基质细胞治疗组小鼠脾淋巴细胞对ConA反应明显增强.结果提示IL-3基因修饰的骨髓基质细胞体内移植对大剂量化疗后机体造血与免疫功能的恢复都有较好的促进作用.     

Autocrine production of interleukin-6 confers cisplatin and paclitaxel resistance in ovarian cancer cells

It has been shown that IL-6 is elevated in the serum and ascites of ovarian cancer patients, and increased IL-6 concentration correlates with poor prognosis and chemoresistance. However, the role of IL-6 expression in the acquisition of the chemoresistance phenotype and the underlining mechanisms of drug resistance in ovarian cancer cells remain unclear. Here we demonstrate that both exogenous (a relatively short period of treatment with recombination IL-6) and endogenous IL-6 (by transfecting with plasmid encoding for sense IL-6) induce cisplatin and paclitaxel resistance in non-IL-6-expressing A2780 cells, while deleting of endogenous IL-6 expression in IL-6-overexpressing SKOV3 cells (by transfecting with plasmid encoding for antisense IL-6) promotes the sensitivity of these cells to anticancer drugs. IL-6-mediated resistance of ovarian cancer cells exhibits decreased proteolytic activation of caspase-3. Meanwhile, the further study demonstrates that the chemoresistance caused by IL-6 is associated with increased expression of both multidrug resistance-related genes (MDR1 and GSTpi) and apoptosis inhibitory proteins (Bcl-2, Bcl-xL and XIAP), as well as activation of Ras/MEK/ERK and PI3K/Akt signaling. Therefore, modulation of IL-6 expression or its related signaling pathway may be a promising strategy of treatment for drug-resistant ovarian cancer.     

Effect of IL-1 on experimental bone/bone-marrow metastases.

Bone metastasis is a common event and a major cause of morbidity in cancer patients. The hematopoietic marrow of the bones, rather than the bone tissue per se, is the target organ in bone metastasis. In the bone marrow, IL-1 induces the release of hematopoietic growth factors that may affect tumor-cell growth. We treated groups of mice with rhuIL-1 alpha to examine its role in the establishment of experimental bone/bone-marrow metastasis. We found that injection of 2 micrograms of rhuIL-1 alpha 24 hr prior to, simultaneously with or 24 hr after the injection of 10(4) B16 melanoma cells into the left cardiac ventricle of mice resulted in a 2-fold increase in the average number of colonized bones per mouse. GM-CSF is produced by bone-marrow stromal cells in response to IL-1, and its receptor has been found on tumor cells, including melanoma cells. However, the administration of rmuGM-CSF to mice by either multiple injections or continuous infusion did not affect the number of colonized bones. Many of the biologic effects of IL-1 are mediated by prostaglandins. Treatment of mice with 100 micrograms of indomethacin, a potent inhibitor of prostaglandin synthesis, prior to the injection of rhuIL-1 alpha, prevented the increase in number of bone metastases. To determine whether constitutive productions of IL-1 and/or prostaglandins are involved in the pathogenesis of bone/bone marrow metastasis, we treated mice with antimouse IL-1 alpha neutralizing antibodies, rhuIRAP (an inhibitor of IL-1 activity) or indomethacin. We found no difference in the average number of colonized bones per mouse between treated and control mice. We conclude that exogenous administration of IL-1 enhances experimental bone/bone-marrow metastases, and that this phenomenon is mediated through prostaglandins. However, neither the constitutive production of IL-1 nor that of prostaglandins appear to play a role in the pathogenesis of bone/bone-marrow metastasis in our murine model system.     

CY15, a malignant histiocytic tumor that is phenotypically similar to immature dendritic cells

The origin and pathogenesis of histiocytic malignancies and the biology of the tumor cells are poorly understood. We have isolated a murine histiocytic tumor cell line (CY15) from a BALB/c IFNgamma(-/-) mouse and characterized it in terms of phenotype and function. The morphology, as judged by electron microscopy, and the surface marker phenotype suggests that CY15 cells are similar to immature dendritic cells (CD11c (low), MHC II (low), CD11b(+), B7.1(+), B7.2(+), and CD40(+)). The cells form tumors in BALB/c mice and metastasize to spleen, liver, lung, kidney, and to a lesser extend to lymph nodes and bone marrow, as judged by the growth of green fluorescent protein transfected tumor cells in mice. CY15 cells are capable of actively taking up antigen (FITC-ovalbumin) and can stimulate T lymphocytes in an allogenic mixed lymphocyte reaction but less effectively than their normal counterparts (immature dendritic cells). They respond to interleukin 4 (IL-4) with up-regulation of CD11c. If stimulated with IFNgamma the cells up-regulate MHC II, CD40 B7.1, and B7.2. Lipopolysaccharide induces the cells to up-regulate B7.1 and B7.2 and to secrete tumor necrosis factor alpha and IL-12. Based on these data, CY15 is a dendritic cell-like tumor cell line and may serve as a transplantable tumor model for histiocytosis in humans.     

应用激活骨髓净化肿瘤细胞的研究

应用国产白介素２（ＩＬ－２）与骨髓细胞共同孵育１或３天，产生激活骨髓（分别记为ＡＢＭ１或ＡＢＭ３）。用３Ｈ－ＴｄＲ释放法测定，表明ＡＢＭ对肿瘤细胞株ＡＧＺＹ－８３ａ和ＣＥＭ具有明显杀伤活性。ＡＢＭ３抗瘤活性明显高于ＡＢＭ１，而新鲜骨髓或单用ＩＬ－２不具有明显抗肿瘤活性。ＡＢＭ可以净化自身骨髓中的ＣＥＭ细胞（效／靶为５０／１），而ＡＢＭ与对照组骨髓比较粒单集落形成率无统计学差别，提示ＡＢＭ仍然保持其造血活性。本文结果初步提示ＡＢＭ可用于净化骨髓中肿瘤细胞之目的。     

EFFECTS OF IFN-a COMBINED WITH IL-6 ON GROWTH AND EXPRESSION OF THE GENES RELATED TO CELL-GROWTH AND APOPTOSIS OF BONE MARROW CELLS FROM PATIENTS WITH CML

CML is a clonal myeloproliferative disorder. The Philadelphia chromosome (ph) is the cytogenetic hall-mark of this disease.[1] The ph chromosome translocation [t(9; 22) (q34; qll)] results in the creation of a hybrid bcr-abl fusion gene and forms an abnormal 210-kD protein (p210bcr-abl) with increased tyrosine kinase activity.[2,3] These molecular changes were thought to play a significant role in leukemogenesis. p210bcr-abl confers a growth advantage on ph-positive CML cells over normal he…     

白介素6在雌激素促进小鼠肺腺癌进展中的作用及其机制

目的 探讨白介素6（interleukin 6, IL-6）在雌激素（estrogen, E2）促进小鼠肺腺癌进展中的作用及其可能的机制。方法 采用乌拉坦诱导雌性昆明小鼠建立肺腺癌模型,进行如下分组处理（每组9只）：空白对照组、E2组、雌激素抑制剂（E2 inhibitor, E2I）组、E2+E2I组、IL-6组、E2+IL-6组。小鼠饲养16周后处死检测小鼠体重变化、成瘤情况、肿瘤分级、肺脏器指数等指标,酶联免疫法（ELISA）检测对照组血清标本中E2/IL-6的含量,实时荧光定量PCR（Real-Time PCR, RT-PCR）检测对照组肿瘤标本中ERβ/IL-6的mRNA表达水平,采用免疫印迹法检测各组ERβ、Akt、MAPK,p-ERβ、p-Akt、p-MAPK表达水平。结果 肺部出现结节的昆明小鼠占小鼠总数的比例（即称为成瘤率）为87.04%（47/54）,小鼠肺部结节做病理切片后证实为肺腺癌的小鼠数目占小鼠总数的比例（即成癌率）为70.37%（38/54）,肺结节数、肿瘤指数、肺脏器指数等统计指标在E2组显著高于E2+E2I组、E2I组、E2+IL-6组、IL-6组及空白对照组（P均<0.05）;对照组小鼠血清中E2与IL-6呈高度相关性（P均<0.05）,各组小鼠肺癌组织中Akt、MAPK、ERβ、p-AKt、p-MAPK、p-ERβ的表达水平及ERβ的mRNA表达水平与肿瘤统计指标表达的趋势相一致（P均<0.05）。结论 在E2促进小鼠肺腺癌进展过程中IL-6具有下调ERβ信号通路作用,提示IL-6可能抑制E2促进肺腺癌进展。     

In vivo modulation of myelopoiesis and immune functions by maleic anhydride divinyl ether copolymer (MVE-2) in tumor-free and MBL-2 tumor-bearing mice treated with cyclophosphamide

Treatment of normal or MBL-2 tumor-bearing mice with cyclophosphamide (CY) caused severe suppression of myelopoiesis and macrophage (M phi) functions, both of which may limit further use of chemotherapy. Additional treatment with the chemically defined biological response modifier maleic anhydride divinyl ether copolymer (MVE-2) was able to ameliorate the myelosuppressive effects of CY and to restore normal bone marrow cellularity. The stimulatory effects on myelopoiesis, however, could only be obtained by administering MVE-2 at greater than or equal to 3 days after CY, which correlated with an MVE-2-induced simultaneous increase in granulocyte and/or macrophage colony-stimulating factor secretion by bone marrow cells or M phi. Injection of MBL-2 tumor-bearing mice with MVE-2, at 3 days after Cy treatment, caused a decrease in tumor burden and a significant increase in median survival time as compared to treatment with CY alone. At the same time, MVE-2 induced an increase in the number of cytotoxic M phi and a complete restoration within the myelopoietic lineage, which might prevent delayed side effects of CY, such as secondary infections, and might permit more intensive chemotherapeutic treatment. Treatment of MBL-2 tumor-bearing mice with MVE-2, at 6 days after CY, induced a significant increase in M phi cytotoxicity but did not prolong median survival time, probably due to a rapid regrowth of tumor after treatment with CY. Our studies thus show that successful combined therapy with the primary cytotoxic agent CY and the biological response modifier MVE-2 depends on precise timing of the drug regimen and is influenced by the extent and reversibility of CY-induced immunosuppression, as well as by the kinetics of recruitment of new effector cells from bone marrow and by the tumor burden present at the time of treatment.     

反馈激活STAT3调控HER2阳性乳腺癌细胞拉帕替尼耐药的机制

 目的 探讨白介素-6（IL-6）在HER2阳性BT-474 乳腺癌细胞拉帕替尼耐药中的作用及其相关分子机制。方法 建立BT-474耐拉帕替尼细胞株（BT-474R）。Western blot检测耐药标志蛋白P-gp的表达，MTT法检测BT-474R细胞的IC50。Caspase-Glo? 3/7法检测拉帕替尼BT-474R与BT-474细胞的Caspase3/7酶活性的变化。Western blot法检测IL-6、p-STAT3、STAT3、Cleaved Caspase 3的蛋白表达水平；RNAi法沉默STAT3基因表达；Caspase-Glo? 3/7法和Annexin V-FITC/PI染色检测沉默后细胞凋亡程度。结果 BT-474R组P-gp表达水平显著高于BT-474组（P<0.05）。 拉帕替尼增强STAT3活性，沉默STAT3基因可恢复BT-474R细胞对拉帕替尼的敏感度、增加cleaved caspase 3蛋白表达水平和Caspase3/7 酶的活性（P<0.01）。沉默STAT3增强了拉帕替尼诱导的耐药细胞凋亡（P<0.01）。拉帕替尼诱导的IL-6表达和分泌激活STAT3，用IL-6抗体抑制拉帕替尼诱导的IL-6，可以阻止拉帕替尼刺激STAT3活性。结论 拉帕替尼通过诱导BT-474细胞分泌IL-6激活STAT3信号通路，增加HER2阳性乳腺癌细胞对拉帕替尼的耐药性。     

Effects of Interleukin-6 and Granulocyte Colony-stimulating Factor on the Proliferation of Leukemic Blast Progenitors from Acute Myeloblastic Leukemia Patients

The effects of recombinant human interleukin-6 (rh IL-6), which has homology with rh granulocyte colony-stimulating factor (rh G-CSF) at the amino acid sequence level, and rh G-CSF on normal human bone marrow cells, fresh leukemic blast progenitors from 16 acute myeloblastic leukemia (AML) patients, and G-CSF-dependent human AML cell line (OCI/AML 1a) were investigated. rh G-CSF stimulated the proliferation of leukemic blast progenitors from 13 out of 16 AML patients tested. rh IL-6 stimulated the proliferation of blasts from eight AML patients and enhanced the G-CSF-dependent proliferation of the fresh AML blasts from two out of eight patients tested. On the other hand, rh IL-6 suppressed the blast colony formation from two AML patients and OCI/AML 1a cells and also reduced the G-CSF-dependent proliferation of the blast progenitors from one of the two patients and the cell line. rh IL-6 had no effect on the colony formation of normal granulocyte-macrophage colony-forming units (CFU-GM) with or without rh G-CSF. Differentiation-induction by rh IL-6 was not observed in the fresh AML blasts but was observed in OCI/AML 1a. The effect of IL-6 on the blast colony formation and G-CSF-dependent blast cell growth was complicated and heterogenous among the AML cases; IL-6 stimulated blast colony formation in some cases and suppressed it in others. The heterogeneity of the response was supposed to be derived from the heterogeneity of the characteristics of AML cells. Although G-CSF simply stimulated the blast colony formation, IL-6 had a bimodulatory effect on the proliferation of leukemic blast progenitors from AML patients. IL-6 might be involved in the regulation of the proliferation of AML cells in vivo as well as in vitro.