Tumor necrosis factor alpha stimulates the growth of the clonogenic cells of acute myeloblastic leukemia in synergy with granulocyte/macrophage colony-stimulating factor

Furosemide‑induced eradication of myeloblasts via the inhibition of tumor necrosis factor‑α expression in a patient with acute biphenotypic leukemia: A case report

The present study reports the potential of furosemide therapeutic activity in acute myeloid leukemia. A 26-year-old man with acute biphenotypic leukemia was treated with furosemide for suspected pulmonary edema, which was later deemed to be an infiltration of leukemia cells. Notably, the myeloblast population was rapidly eliminated during furosemide therapy. Bone marrow specimens biopsied at different time points were used for immunohistochemical analysis of the expression levels of tumor necrosis factor-α (TNF-α) and its two receptors, TNF-α receptors 1 and 2. The expression of TNF-α and its receptors in the bone marrow was markedly suppressed by furosemide, along with the elimination of the myeloblasts. Thus, it was hypothesized that the growth of myeloblasts in the patient depended on autocrine and/or paracrine TNF-α stimulation, whereas furosemide disrupted this positive feedback loop. Therefore, furosemide is suggested as an effective therapeutic agent for acute myeloid leukemia, at least as an adjunct to standard chemotherapy and gene-targeted therapy.

IL-6 blockade reverses bone marrow failure induced by human acute myeloid leukemia

Most patients with acute myeloid leukemia (AML) die from complications arising from cytopenias resulting from bone marrow (BM) failure. The common presumption among physicians is that AML-induced BM failure is primarily due to overcrowding, yet BM failure is observed even with low burden of disease. Here, we use large clinical datasets to show the lack of correlation between BM blast burden and degree of cytopenias at the time of diagnosis. We develop a splenectomized xenograft model to demonstrate that transplantation of human primary AML into immunocompromised mice recapitulates the human disease course by induction of BM failure via depletion of mouse hematopoietic stem and progenitor populations. Using unbiased approaches, we show that AML-elaborated IL-6 acts to block erythroid differentiation at the proerythroblast stage and that blocking antibodies against human IL-6 can improve AML-induced anemia and prolong overall survival, suggesting a potential therapeutic approach.

Synergistic effects of tumor necrosis factor-α and insulin-like growth factor-I on survival of human trophoblast-derived BeWo cell line

OBJECTIVE

Trophoblast survival is regulated by cytokines and growth factors. While the pharmacological levels (10-100 ng/mL) of tumor necrosis factor (TNF)- α affect trophoblasts survival in vitro, the effects of the physiological levels (1-10 pg/mL) of TNF-α remain unknown. We investigated the effects of the physiological levels of TNF-α on proliferation and apoptosis of human trophoblast cells by using BeWo cells. Insulin-like growth factor (IGF)-I is also a potent regulator of trophoblast survival and has been known to exert synergistic effects with other hormones. The interaction of IGF-I and TNF-α on BeWo cells survival was also examined.

METHODS

After incubating BeWo under the presence of TNF-α (10-10⁵ pg/mL) and IGF-I (10² ng/mL), we assessed cell number by WST-1 assay and cell proliferation by BrdU uptake assay and immunocytochemistry with anti-Ki67 antibody. Apoptosis was evaluated by TUNEL assay and caspase-3, 8 activity assays.

RESULTS

Under the presence of IGF-I, cell number, BrdU uptake, and Ki-67 expression of BeWo were dose-dependently enhanced by low TNF-α (10-10² pg/mL), while no such effects were detected without IGF-I. Higher levels of TNF-α (10⁴-10⁵ pg/mL) showed inhibiting effects on cell number and cell proliferation. The number of TUNEL positive cells were decreased and caspase activities were suppressed by lower levels (10-10² pg/mL) of TNF-α and IGF-I independently. Higher levels of TNF-α (10⁴-10⁵ pg/mL) showed promoting effects on apoptosis irrespective of IGF-I.

CONCLUSION

The physiological levels of TNF-α and IGF-I had synergetic effects on enhancing cell proliferation and also independently inhibited apoptosis of Bewo cells.

Regulation of hematopoietic and leukemic stem cells by the immune system

Hematopoietic stem cells (HSCs) are rare, multipotent cells that generate via progenitor and precursor cells of all blood lineages. Similar to normal hematopoiesis, leukemia is also hierarchically organized and a subpopulation of leukemic cells, the leukemic stem cells (LSCs), is responsible for disease initiation and maintenance and gives rise to more differentiated malignant cells. Although genetically abnormal, LSCs share many characteristics with normal HSCs, including quiescence, multipotency and self-renewal. Normal HSCs reside in a specialized microenvironment in the bone marrow (BM), the so-called HSC niche that crucially regulates HSC survival and function. Many cell types including osteoblastic, perivascular, endothelial and mesenchymal cells contribute to the HSC niche. In addition, the BM functions as primary and secondary lymphoid organ and hosts various mature immune cell types, including T and B cells, dendritic cells and macrophages that contribute to the HSC niche. Signals derived from the HSC niche are necessary to regulate demand-adapted responses of HSCs and progenitor cells after BM stress or during infection. LSCs occupy similar niches and depend on signals from the BM microenvironment. However, in addition to the cell types that constitute the HSC niche during homeostasis, in leukemia the BM is infiltrated by activated leukemia-specific immune cells. Leukemic cells express different antigens that are able to activate CD4⁺ and CD8⁺ T cells. It is well documented that activated T cells can contribute to the control of leukemic cells and it was hoped that these cells may be able to target and eliminate the therapy-resistant LSCs. However, the actual interaction of leukemia-specific T cells with LSCs remains ill-defined. Paradoxically, many immune mechanisms that evolved to activate emergency hematopoiesis during infection may actually contribute to the expansion and differentiation of LSCs, promoting leukemia progression. In this review, we summarize mechanisms by which the immune system regulates HSCs and LSCs.

Positive feedback between NF-κB and TNF-α promotes leukemia-initiating cell capacity

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy that originates from leukemia-initiating cells (LICs). The identification of common mechanisms underlying LIC development will be important in establishing broadly effective therapeutics for AML. Constitutive NF-κB pathway activation has been reported in different types of AML; however, the mechanism of NF-κB activation and its importance in leukemia progression are poorly understood. Here, we analyzed myeloid leukemia mouse models to assess NF-κB activity in AML LICs. We found that LICs, but not normal hematopoietic stem cells or non-LIC fractions within leukemia cells, exhibited constitutive NF-κB activity. This activity was maintained through autocrine TNF-α secretion, which formed an NF-κB/TNF-α positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of IκBα and further supported NF-κB activity. Pharmacological inhibition of the proteasome complex markedly suppressed leukemia progression in vivo. Conversely, enhanced activation of NF-κB signaling expanded LIC frequency within leukemia cell populations. We also demonstrated a strong correlation between NF-κB activity and TNF-α secretion in human AML samples. Our findings indicate that NF-κB/TNF-α signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.

Low expression of stem cell antigen-1 on mouse haematopoietic precursors is associated with erythroid differentiation

Sca1 is a surface marker of haematopoietic stem cell but its role in erythropoiesis is still largely unknown. In this work we evaluated the ability of Sca1⁺ cells to differentiate into cells of the erythrocytic lineage. We performed FACS analysis of complete and purified Sca1⁺ bone marrow cells from C3H/HeNHsd mice and measured the expression of CD71 and Terr119 to evaluate the stages in erythroid development. Definitive erythropoiesis was evident within the complete bone marrow, while only proerythroblasts were found in Sca1⁺ cells, suggesting that Sca1 is a negative regulator of erythropoiesis. We also used FDCP-mix cells and their PU.1 and SCL transfectants. The PU.1 transfectant showed significantly increased expression of Sca1 and was not induced to differentiate into red blood cells, while the SCL transfectant showed significantly lower expression of Sca1 and produced red blood cells. The results of this study suggest that increased Sca1 expression on erythropoietic precursors inhibits erythroid differentiation.

Long-term colchicine therapy in a patient with Behçet’s disease and acute promyelocytic leukemia

Behçet's disease causes a continuous T-lymphocytic mediated inflammatory reaction in the small arterioles, which results in gradual destruction of any human organ or system. The benefit of treatment with colchicine in patients with Behçet's disease has been reported in literature. Acute leukemia has seldom been associated with Behçet's disease, although acute promyelocytic leukemia is a particular subtype of leukemia that is often characterized by special cytogenetic abnormalities. We report a male patient with acute promyelocytic leukemia and Behçet's disease who had received long-term treatment with colchicine. To our knowledge, this is the first report of the concomitant occurrence of acute promyelocytic leukemia and Behçet's disease, which suggests that long-term colchicine therapy has a role in the pathogenesis of acute promyelocytic leukemia. The patient described has been treated with retinoic acid and idarubicin (the ATRA-IDA protocol). At the time of this writing, his disease is in clinical remission.

Inflammation and cancer: How hot is the link?

Although inflammation has long been known as a localized protective reaction of tissue to irritation, injury, or infection, characterized by pain, redness, swelling, and sometimes loss of function, there has been a new realization about its role in a wide variety of diseases, including cancer. While acute inflammation is a part of the defense response, chronic inflammation can lead to cancer, diabetes, cardiovascular, pulmonary, and neurological diseases. Several pro-inflammatory gene products have been identified that mediate a critical role in suppression of apoptosis, proliferation, angiogenesis, invasion, and metastasis. Among these gene products are TNF and members of its superfamily, IL-1alpha, IL-1beta, IL-6, IL-8, IL-18, chemokines, MMP-9, VEGF, COX-2, and 5-LOX. The expression of all these genes are mainly regulated by the transcription factor NF-kappaB, which is constitutively active in most tumors and is induced by carcinogens (such as cigarette smoke), tumor promoters, carcinogenic viral proteins (HIV-tat, HIV-nef, HIV-vpr, KHSV, EBV-LMP1, HTLV1-tax, HPV, HCV, and HBV), chemotherapeutic agents, and gamma-irradiation. These observations imply that anti-inflammatory agents that suppress NF-kappaB or NF-kappaB-regulated products should have a potential in both the prevention and treatment of cancer. The current review describes in detail the critical link between inflammation and cancer.

Effect of ICAM-1 and LFA-1 in hyperleukocytic acute myeloid leukaemia

Acute hyperleukocytic leukemia [AHL; WBC count >100 x 10(9)/l] is associated with a life-threatening complication. The mechanisms of hyperleukocytosis in acute myeloid leukaemia (AML) remain unclear. However, the interaction of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) plays an important role in the adhesion and migration of normal leukocytes and AML cells. Therefore, effects of ICAM-1 and LFA-1 were studied in hyperleukocytic AML. The adhesion of hyperleukocytic AML blasts and human umbilical vein endothelial cells (HUVECs) was significantly increased compared with that of blasts from non-hyperleukocytic AML (WBC < 100 x 10(9)/l). The adhesion of normal neutrophils and HUVECs treated with hyperleukocytic AML blast supernatant was increased significantly. Finally, we determined the ICAM-1 on the surface of HUVECs treated with the supernatant of hyperleukocytic AML blasts and LFA-1 on hyperleukocytic AML blasts by flow cytometry. It showed that the ICAM-1 expression on the surface of the HUVECs treated with hyperleukocytic AML blast supernatant for 24 h could be increased, and the expression of LFA-1 on hyperleukocytic AML was also increased significantly. Our data show that hyperleukocytic AML blasts stimulate the endothelium to secrete more ICAM-1 and promote their own adhesion to vascular endothelium, suggesting that ICAM-1 and LFA-1 may have a role in hyperleukocytic AML.

Effects of TNFalpha on the growth and sensitivity to cytosine arabinoside of blast progenitors in acute myelogenous leukemia with special reference to the role of NF-kappaB

Leukemic blasts in acute myelogenous leukemia (AML) are derived from a minor population of cells called blast progenitors. Hematopoietic growth factors (HGFs) stimulate their growth and simultaneously sensitize them to cytosine arabinoside (Ara-C), a cell-cycle-specific cytotoxic drug. Since tumor necrosis factor alpha (TNFalpha) modifies HGF activities, we examined the effects of TNFalpha in combination with HGFs on in vitro growth and Ara-C sensitivity of AML blast progenitors in patient samples. TNFalpha variably affected HGF-supported colony formation and the self-renewal of blast progenitors. However, the combination of TNFalpha with IL-3 uniformly rendered blast progenitors more resistant to Ara-C irrespective of whether TNFalpha suppressed or augmented IL-3-supported growth, indicating that TNFalpha regulates the Ara-C sensitivity of leukemic progenitors independently of their cell cycle status. Since nuclear factor-kappaB (NF-kappaB) is activated by TNFalpha and induces expression of prosurvival genes, effects of the antisense oligodeoxynucleotides to NF-kappaB subunits, p65 and p50, were examined. Antisense oligodeoxynucleotides sensitized HL60 cells to Ara-C but rendered leukemic progenitors in patient samples even more resistant to Ara-C in the presence of TNFalpha and IL-3 in combination, indicating that NF-kappaB is involved in the Ara-C sensitivity of leukemic blast progenitors but may exert opposite dual functions, namely protection from and induction of apoptosis, under different conditions.

Clinical significance of IL-18 gene over-expression in AML

Little is known about the clinical significance of interleukin (IL)-18, a novel immunoregulatory cytokine, in acute myeloid leukemia (AML). Using reverse transcriptase polymerase chain reaction (RT-PCR) analysis, levels of IL-18 mRNA were assessed in bone marrow mononuclear cells (BMMC) from 47 adult patients with de novo or CR AML in order to explore the clinical significance of IL-18. The relationship between expression levels and the established prognostic factors such as age, cytogenetic aberrations, CD34 expression and FAB subtypes was investigated. Either disease status, age or CD34 expression were found to significantly correlate with the expression of IL-18. With respect to FAB cytotypes, expression of IL-18 gene in M4/M5 (n=15) was statistically higher than that in other subtypes (n=32, P<0.001). Moreover, a significant difference in IL-18 gene expression was obtained between the high risk group and the intermediate risk group (0.5627 versus 0.3111, P=0.038). In addition, a relationship between IL-18 expression of BMMC and initial white blood cell (WBC) was clearly demonstrated by a statistical analysis (r=0.806, P<0.001). These observations suggest that IL-18 gene over-expression might reflect the convergence of several important unfavorable prognostic factors in AML.

Potential roles of extracellular signal-regulated kinase but not p38 during myeloid differentiation of U937 cells stimulated by cytokines: augmentation of differentiation via prolonged activation of extracellular signal-regulated kinase

OBJECTIVE

To clarify the signaling mechanism of human myeloid differentiation by hematopoietic growth factors and cytokines, we investigated the role of extracellular signal-regulated kinase (ERK) during the differentiation of human monoblastic U937 cells stimulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF).

MATERIALS AND METHODS

Myeloid differentiation was evaluated by morphology, function (respiratory burst activity), and cell surface expression of adhesion molecule (CD11b), and activation of ERK and/or p38 was determined by Western blotting and/or in vitro kinase assay. Inhibition of the ERK pathway was performed using PD98059, a specific inhibitor of this pathway.

RESULTS

U937 cells were induced to be differentiated by the combination of GM-CSF and TNF, but only minimally by either cytokine alone. Transient phosphorylation and activation of ERK was induced by both GM-CSF alone and combination of the two cytokines, whereas sustained phosphorylation and activation was induced only by the combination. In addition, PD98059, a specific inhibitor of ERK pathway, almost completely abolished this prolonged phosphorylation of ERK and completely blocked differentiation. In contrast, both TNF alone and cytokine combination equivalently phosphorylated p38 in U937 cells, which was dissociated from differentiation, and a specific inhibitor of p38 (SB203580) did not inhibit differentiation.

CONCLUSIONS

The results indicate potential roles of sustained activation of ERK but not of p38 in the signaling pathways for human myeloid differentiation in U937 cells synergistically stimulated by the two physiologic cytokines GM-CSF and TNF.

Differential response to stem cell factor and Flt3 ligand by the FAB subtype in acute myeloid leukemia clonogenic cells

Proliferative response of blast clonogenic cells to various hematopoietic growth factors (HGF), including stem cell factor (SCF) and flt3 ligand (FL) was investigated in 100 patients with acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML) in myeloid crisis (MC). The frequency of spontaneous colony formation was significantly high in CML in MC (55%) and AML French-American-British (FAB) subtype M4 (48%) compared with M2 (16%). No spontaneous colony was formed in any of the patients with M1 and M3. The frequency of proliferative response to various HGF alone and in combination according to FAB subtype and CML in MC was as follows: that to granulocyte colony-stimulating factor (G-CSF) was lowest in M1 and CML in MC (50%) compared with other FAB subtypes (>or=86%), that to granulocyte-macrophage CSF (GM-CSF) was lowest in CML in MC (44%) compared with FAB subtypes (>or=74%), and that to interleukin-3 (IL-3) was lowest in CML in MC (30%) compared with FAB subtypes (>or=78%). SCF and FL stimulated blast colony formation in 11% and 17% of patients with M3, respectively, but there was no response to both, and in 60% and 57% of patients with CML in MC, respectively, with 14% showing a response to both. The frequency of proliferative response to both SCF and FL increased in the order of M1 (33%), M2 (63%), M4-5 (95%), and M6 (100%). The results are summarized as follows: absence of spontaneous colony formation and response to HGF other than SCF and FL, designated as HGF-dependent growth (M3); spontaneous colony formation and lowest response to HGF, designated as autonomous growth (CML in MC); and spontaneous colony formation and highest response to HGF including SCF and FL, designated as autocrine growth (M4-6). M1 and M2 were intermediate between CML in MC and M4-6. The relation between in vitro growth pattern of blast clonogenic cells and prognosis in AML FAB subtype and CML in MC is discussed.

Endothelial cell activation by myeloblasts: molecular mechanisms of leukostasis and leukemic cell dissemination

Leukostasis and tissue infiltration by leukemic cells are poorly understood life-threatening complications of acute leukemia. This study has tested the hypothesis that adhesion receptors and cytokines secreted by blast cells play central roles in these reactions. Immunophenotypic studies showed that acute myeloid leukemia (AML) cells (n = 78) of the M0 to M5 subtypes of the French-American-British Cooperative Group expressed various amounts of adhesion receptors, including CD11a, b, c/CD18, CD49d, e, f/CD29, CD54, sCD15, and L-selectin. The presence of functional adhesion receptors was evaluated using a nonstatic adhesion assay. The number of blast cells attached to unactivated endothelium increased by 7 to 31 times after a 6-hour exposure of endothelium to tumor necrosis factor (TNF)-alpha. Inhibition studies showed that multiple adhesion receptors--including L-selectin, E-selectin, VCAM-1, and CD11/CD18--were involved in blast cell adhesion to TNF-alpha-activated endothelium. Leukemic cells were then cocultured at 37 degrees C on unactivated endothelial cell monolayers for time periods up to 24 hours. A time-dependent increase in the number of blasts attached to the endothelium and a concomitant induction of ICAM-1, VCAM-1, and E-selectin were observed. Additional experiments revealed that endothelial cell activation by leukemic myeloblasts was caused by cytokine secretion by blast cells, in particular TNF-alpha and IL-1 beta, and direct contacts between adhesion receptors expressed by blast cells and endothelial cells. Thus, leukemic cells have the ability to generate conditions that promote their own adhesion to vascular endothelium, a property that may have important implications for the pathophysiology of leukostasis and tissue infiltration by leukemic blast cells. (Blood. 2001;97:2121-2129)

In vivo effects of IL-4, IL-10, and amifostine on cytokine production in patients with acute myelogenous leukemia

Both IL-4 and IL-10 have been shown in vitro to inhibit leukemia cell secretion of IL-1beta, GM-CSF, and TNFalpha, and increase leukemia cell release of IL-1ra. In this study, we have investigated the in vivo effects of IL-4, IL-10, and amifostine on cytokine production in patients with acute myelogenous leukemia (AML). Serum IL-1ra, IL-1beta, TNFalpha, GM-CSF, and SCF levels were measured in AML patients who received IL-4, IL-10, or amifostine. No significant changes in the serum levels of IL-1ra, IL-1beta, TNFalpha, GM-CSF, and SCF were found in AML patients who received amifostine. Both IL-4 and IL-10 were found to increase serum IL-1ra. This data is in accord with the in vitro studies. However, IL-4 increased serum GM-CSF levels and IL-10 increased serum IL-1beta and TNFalpha levels. These in vivo effects of the two cytokines differ from their in vitro effects. Despite the similar effects of IL-4 and IL-10 on cytokine production by AML cells in vitro, different effects were observed in AML patients in vivo. IL-4 increased serum SCF levels, whereas IL-10 decreased serum SCF levels. IL-4 increased serum GM-CSF levels, whereas IL-10 had no effect on them. Although IL-10 increased serum IL-1beta and TNFalpha levels, IL-4 had no effect on them. These findings indicate that the in vitro effects of IL-4 and IL-10 do not necessarily reflect their in vivo effects, and that the complex effects of the two cytokines on serum cytokine levels make it difficult to predict their therapeutic potential.

Phosphatidylcholine-specific phospholipase C and phospholipase D are respectively implicated in mitogen-activated protein kinase and nuclear factor kappaB activation in tumour-necrosis-factor-alpha-treated immature acute-myeloid-leukaemia cells

Tumour necrosis factor-alpha (TNFalpha) has been reported to induce potent growth inhibition of committed myeloid progenitor cells, whereas it is a potential growth stimulator of human CD34(+)CD38(-) multipotent haematopoietic cells. The present study was aimed at evaluating the respective role of two phospholipases, phosphatidylcholine-specific phospholipase C (PC-PLC) and phospholipase D (PLD) in the response of the CD34(+) CD38(-) KG1a cells to TNFalpha. In these cells TNFalpha triggered phosphoinositide 3-kinase (PI3K)-dependent PC hydrolysis within 4-8 min with concomitant production of both diacylglycerol (DAG) and phosphocholine (P-chol). DAG and P-chol production was accompanied by extracellular-signal-related protein kinase-1 ('ERK-1') activation and DNA-synthesis stimulation. PC-PLC stimulation was followed by PI3K-independent PLD activation with concomitant phosphatidic acid (PA) production followed by PA-derived DAG accumulation and sustained nuclear factor kappaB (NF-kappaB) activation. PLD/NF-kappaB signalling activation played no role in the TNFalpha proliferative effect and conferred no consistent protection of KG1a cells towards antileukaemic agents. Altogether these results suggest that, in KG1a cells, TNFalpha can stimulate in parallel PC-PLC and PLD, whose lipid products activate in turn mitogen-activated protein kinase (MAP kinase) and NF-kappaB signalling respectively. Finally, our study suggests that PC-PLC, but not PLD, plays a role in the TNFalpha proliferative effect in immature myeloid cells.

Characterization of a newly established human acinic cell adenocarcinoma cell line (HACC) originating from the salivary gland: morphological features and role of various growth factors on the growth of the HACC cell line

Human acinic cell adenocarcinoma cell (HACC) line was established from the pleural effusion that contains metastatic tumor cells of acinic cell adenocarcinoma of papillary and microcystic type originating from the parotid gland. The HACC cells grew in an adherent monolayer with a doubling time of 66 h. Implanted tumor of SCID mice revealed similar histological findings to that of the primary tumor. The HACC cells produced mucin and expressed epithelial markers as well as alpha1-antitrypsin and lysozyme, whereas salivary peptide P-C was expressed in cultured HACC cells but not in the primary and implanted HACC cell tumors. S-100 protein was also expressed in both the primary tumor and HACC cell line. Neither amplification of common oncogenes nor expression of p53 was observed. The receptor for epidermal growth factor (EGF) was expressed, indicating EGF and transforming growth factor-alpha (TGF-alpha) enhanced the growth of the HACC line. Unexpectedly, tumor necrosis factor-a (TNF-alpha) also enhanced the growth of the HACC line significantly. However, there was no evidence of autocrine growth using these growth factors. In contrast, TGF-beta1 inhibited the growth of the HACC cell line through apoptosis. The HACC cell line has features similar to both acinar and intercalated ductal cells of the salivary gland. Epidermal growth factor, TGF-alpha and TNF-alpha are potential growth factors for the HACC cell line. The HACC cell line may be a good model for studying the biological behavior of salivary gland neoplasms.

Serum levels of p55 and p75 soluble TNF receptors in adult acute leukaemia at diagnosis: correlation with clinical and biological features and outcome

The tumour necrosis factor (TNF)/TNF-receptor (TNFR) complex plays a role in the growth of leukaemic cells. We retrospectively investigated the relationship between pretreatment serum concentration of soluble TNFR (p55- and p75-sTNFRs) and outcome in adult acute myeloid (AML 82 cases) and lymphoid (ALL 44 cases) leukaemia. Both sTNFRs were significantly higher in AML (p55-sTNFR 4.53 +/- 3.7, median 3.75; p75-sTNFR 6.51 +/- 5.25 ng/ml, median 4.72) and ALL sera (3.31 +/- 1.5, median 2.95; 5.30 +/- 2.3 ng/ml, median 4.56, respectively) than in controls (1.89 +/- 0.5, median 1.98; 2.22 +/- 0.8 ng/ml, median 2.37) (P < 0.01 for both sTNFRs). Fresh leukaemic cells expressed p55- and p75-sTNFRs, which were modulated and released into the supernatant (SN) following short-term in vitro culture, suggesting that in vivo sTNFRs were also leukaemia-derived. Whereas no correlation was observed between sTNFRs and outcome in ALL, in AML higher p55-sTNFR levels (> 3.75 ng/ml) were associated with shorter disease-free survival (DFS) (P = 0.006) and overall survival (OS) (P = 0.0004). At multivariate analysis p55-sTNFR was the most significant predictor of DFS (P = 0.006) and OS (P < 0.001). Our data suggest that the prognostic significance of p55-sTNFR in AML could be related to relevant biological features of AML blasts.

The hairy cell leukemia cell line Eskol spontaneously synthesizes tumor necrosis factor-alpha and nitric oxide

Tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) exert a wide array of immunoregulatory, partly related effects. We examined the production of these two mediators by the human hairy cell leukemia cell line Eskol. Combined cell lysate and supernatant of Eskol cells (0.5 x 10(6) cells ml(-1)) incubated for 18 h, contained a mean of 1.5 ng ml(-1) TNF-alpha. This spontaneous TNF-alpha synthesis was enhanced by phorbol ester (PMA) and phytohemagglutinin (PHA) and decreased by dexamethasone. Nitrite, the stable product of NO, accumulated in the supernatant of Eskol cells after prolonged incubation. Maximal nitrite concentrations (range: 0.8-3.5 microM at 2 x 10(6) cells ml(-1)) were detected after 7 days of incubation. NO production was augmented by PHA and reduced by PMA. The inhibitors of NO synthase N(G)-monomethyl-L-arginine (L-NMMA) and aminoguanidine decreased NO synthesis. Simultaneous activation with the proinflammatory cytokines, interferon-gamma, interleukin-1beta and TNF-alpha, increased NO synthesis. These results suggest that NO production in Eskol cells results from inducible NO synthase activity. This is the first direct demonstration of NO formation in human lymphoid cells. The cell line, Eskol, may serve as a model to study regulation of TNF-alpha and NO synthesis in human B-cell leukemia.

Cytokine modulation of interleukin 1 and tumour necrosis factor-alpha secretion from acute myelogenous leukaemia blast cells in vitro

Spontaneous secretion of interleukin 1 (IL-1) alpha, IL-1 beta and tumour necrosis factor-alpha (TNF-alpha) from acute myelogenous leukaemia (AML) blasts showed significant correlation, and detectable levels of all cytokines were seen for a majority of patients. IL-3 and granulocyte/macrophage colony-stimulating factor increased secretion of IL-1 alpha, IL-1 beta and TNF-alpha for a majority of AML patients, whereas IL-4 decreased cytokine secretion. The effect of IL-6 and stem cell factor on cytokine secretion varied between different patients. A wide variation in IL-1 alpha, IL-1 beta and TNF-alpha secretion between different patients was seen both for spontaneous secretion and in the presence of all cytokines.

Cytokines and cytokine receptors in acute lymphoblastic leukemia expressing myeloid markers--role in growth regulation

There is no evidence that cancer cells including leukemic cells are immortal. It has been clearly indicated that certain cytokines can significantly stimulate leukemic cell proliferation in vitro, and sustain the circuit of autocrine or paracrine stimulation. The biological roles of cytokines and cytokine receptors have been intensively investigated in acute leukemia. Recently coexpression of both lymphoid and myeloid features on a single leukemic cell has been well recognized using a flowcytometric technique. Studies of ALL cells expressing myeloid markers (My+ ALL) have indicated that the profiles of cytokines and cytokine receptors expressed by My+ ALL show both similarities and differences to those in My- ALL or acute myelogenous leukemia (AML), suggesting that My+ ALL cells may originate from uncommitted hematopoietic precursor cells coexpressing features of both lymphoid and myeloid lineages. The exact assessment of cytokine response of leukemic cells would provide an important tool for phenotyping acute leukemia based on the growth properties of the cells (cytokine phenotyping), in addition to the morphologic classification and immunological surface phenotyping. Additionally alteration of sensitivity to cytotoxic anticancer drugs by cytokine stimulation may be the new strategy for biologic therapy of acute leukemia.

Effects of soluble interleukin-1 receptor and tumor-necrosis factor receptor, respectively, on the IL-1- and TNF-alpha-induced DNA synthesis of acute myeloblastic leukemia blasts in vitro

This study demonstrates that soluble interleukin-1 receptor and tumor necrosis factor receptor modulate their corresponding cytokine-induced DNA synthesis of acute myeloblastic leukemia (AML) blasts in a dose-dependent, bimodal fashion; at lower concentrations they enhanced, while at high concentrations they inhibited, the cytokine-mediated effects. Furthermore, the concentrations of endogenously produced IL-1 beta and TNF-alpha were found to be significantly (p < 0.01) higher in supernatants of AML cells cultured in the presence of corresponding soluble receptors compared to their levels in supernatants of cells growing in the absence of these molecules. Our data might suggest that the attenuation of the spontaneous decay of IL-1 beta as well as TNF-alpha activities by soluble receptors may account for their ability to augment some of their effects.

IL-1 alpha and TNF alpha act synergistically to stimulate production of myeloid colony-stimulating factors by cultured human bone marrow stromal cells and cloned stromal cell strains

Human bone marrow stromal cells respond to stimulation by the monokines IL-1 and TNF by producing colony-stimulating factors such as GM-CSF and G-CSF. In this study we show that IL-1 alpha and TNF alpha act synergistically to stimulate GM-CSF and G-CSF production by cultured marrow stromal cells. We further show that IL-1 alpha and TNF alpha synergistically stimulate production of GM-CSF and G-CSF by a clonal stroma-derived cell strain. Although IL-1 and TNF share many of the same biological activities, we show that IL-1 alpha and TNF alpha have an unequal ability to induce myeloid-CSF production by both cultures, with IL-1 alpha being the more potent inducer. We found that induction by IL-1 alpha and TNF alpha was independent of cell proliferation. The effect of IL-1 alpha and TNF alpha on production of the two myeloid-CSFs by the clonal cells was significantly greater than the unfractionated passaged stromal cultures, having the greater effect on G-CSF production. The clonally derived stromal cells constitutively produced colony-stimulating activity, in particular GM-CSF, at levels easily detected by ELISA. These findings show that, in addition to the overlapping and additive activities of IL-1 alpha and TNF alpha, they can interact synergistically. Our findings further suggest that a small subpopulation of stroma cells may be the major producer of G-CSF in the marrow microenvironment during immune response.

IFN-gamma and TNF-alpha secretion by CD4+ and CD8+ TCR alpha beta + T-cell clones derived early after allogeneic bone marrow transplantation

Secretion of the potentially antileukaemic cytokines IFN-gamma and TNF-alpha was investigated for CD4+ and CD8+ TCR alpha beta + T-cell clones derived from 4 leukaemia patients 3-6 weeks after allogeneic BMT. We investigated cytokine secretion in response to the activation signal accessory cells+phytohaemagglutinin+Interleukin 2. All clones derived after BMT were capable of IFN-gamma and TNF-alpha secretion, and both for CD4+ (n = 96) and CD8+ (n = 8) T cells quantities of IFN-gamma and TNF-alpha were significantly correlated with one another. When comparing the overall results for posttransplant and normal T-cell clones derived from 2 bone marrow donors (n = 65), both CD4+ and CD8+ TCR alpha beta + T-cell clones showed increased IFN-gamma production, and CD4+ but not CD8+ clones showed a decreased TNF-alpha secretion. The results suggest that noncytotoxic T cells derived after allogeneic BMT can produce IFN-gamma and TNF-alpha and may thus be capable of mediating antileukaemic effects.

The mitogenic response to tumor necrosis factor alpha requires c-Jun/AP-1

In the present study, we addressed the role of the c-jun proto-oncogene in the mitogenic response of human fibroblasts and primary acute myelogenous leukemia blasts to tumor necrosis factor alpha (TNF-alpha). Our data indicate that TNF-alpha treatment of these cells is associated with transcriptional activation of c-jun, resulting in accumulation of c-jun mRNA and protein expression. In order to elucidate the role of c-Jun/AP-1 in TNF-mediated growth stimulation, the antisense (AS) technique was used. Uptake studies of oligonucleotides were performed with fibroblasts, demonstrating that incorporation of oligomers was maximal at 4 h. Oligodeoxynucleotides remained stable in these cells for up to 24 h. Treatment of fibroblasts with the AS oligonucleotide resulted in intracellular duplex formation followed by an efficient translation blockade of c-Jun/AP-1. In contrast, sense (S) and nonsense (NS) oligodeoxynucleotides failed to form intracellular duplexes and also did not interfere with translation of c-Jun/AP-1, suggesting specific elimination of c-Jun/AP-1 by the AS oligomer. Fibroblasts cultured in the presence of the AS oligonucleotide but not those cultured in the presence of the S or NS oligonucleotide failed to respond proliferatively to TNF-alpha. These findings could be confirmed by experiments with primary acute myelogenous leukemia blasts, which also demonstrated that TNF-induced growth stimulation required c-Jun/AP-1 function. Taken together, our results indicate that activation of c-Jun/AP-1 plays a pivotal role in the signaling cascade initiated by TNF, which leads to a proliferative response of its target cells.

Thymosin beta 4 synergizes with human granulocyte-macrophage colony-stimulating factor in maintaining bone marrow proliferation

Recent evidence supports a role for thymosin beta 4 (T beta 4) in the inhibition of murine hematopoietic stem cell proliferation. This supposition results from studies in which the N-terminal tetrapeptide derived from native T beta 4 was administered to mice and appeared to prevent CFU-S recruitment into DNA synthesis. The importance of this observation was the concomitant ability of the tetrapeptide to prevent cytosine arabinoside (ara-C) toxicity in mice given LD50 doses of this drug. In the present study, we have extended these observations by demonstrating that whole synthetic T beta 4 is more effective than the N-terminal tetrapeptide in protecting mice from the toxicity of ara-C. This observation supports the hypothesis that T beta 4 is the biologically important parent molecule for this activity. To determine if inhibition of cell cycle progression also occurs in committed human bone marrow progenitors treated with T beta 4, we have investigated the effects of synthetic T beta 4 on proliferating and unstimulated enriched human bone marrow. In short-term liquid cultures studied sequentially over 1-7 days, T beta 4 failed to inhibit cell proliferation, but maintained the proliferative effect of granulocyte-macrophage colony stimulating factor (GM-CSF) on days following maximum stimulation (days 5-7). No effect was noted before the fifth day in culture, nor did T beta 4 exert any demonstrable effect in the absence of added GM-CSF. Any observable effect of T beta 4 required that it be present in the cultures on or before day 3 of GM-CSF stimulation. These results suggest that an additional effect of T beta 4 is the stimulation of a subpopulation of committed human bone marrow precursor cells to become more sensitive to the growth-promoting activity of GM-CSF, thereby enhancing myelopoiesis. It is of interest that the N-terminal peptide of T beta 4 is a shared sequence with tumor necrosis factor alpha, which is also known to have a similar stimulatory capacity. We, therefore, postulate that the growth enhancement noted in short-term cultures is mediated by the region containing these shared sequences.

Secretion of IL-2, IL-3, IL-4, IL-6 and GM-CSF by CD4+ and CD8+ TCR alpha beta+ T-cell clones derived early after allogeneic bone marrow transplantation

Secretion of different cytokines may be an important T-cell effector mechanism for bone marrow engraftment, graft versus host disease and graft versus leukaemia effects after allogeneic bone marrow transplantation (BMT). Cytokine secretion and autocrine proliferative capacity of T-cell clones derived from leukaemia patients 3-6 weeks after allogeneic bone marrow transplantation were investigated. Only a minority of post-transplant T-cell clones (23/120; 19%) was capable of undergoing autocrine proliferation. By contrast, 21/65 (32%) normal control clones from the marrow donors derived under the same conditions were autocrine proliferative. All clones were interleukin-2 (IL-2) responsive. A majority (12/17; 71%) of autocrine proliferating post-transplant clones secreted detectable IL-2. Compared with control clones, CD4+ T-cell clones derived early after BMT produced decreased levels of interleukin-4 (IL-4) and interleukin-6 (IL-6), whereas secretion of interleukin-3 (IL-3) and granulocyte/macrophage colony-stimulating factor (GM-CSF) showed no significant difference. The small number (n = 8) of posttransplant CD8+ clones showed decreased production of IL-3, IL-4 and IL-6 compared with control clones, but normal secretion of GM-CSF. Neither CD4+ nor CD8+ T-cell clones secreted interleukin-7 (IL-7).

The mitogenic response to tumor necrosis factor alpha requires c-Jun/AP-1

In the present study, we addressed the role of the c-jun proto-oncogene in the mitogenic response of human fibroblasts and primary acute myelogenous leukemia blasts to tumor necrosis factor alpha (TNF-alpha). Our data indicate that TNF-alpha treatment of these cells is associated with transcriptional activation of c-jun, resulting in accumulation of c-jun mRNA and protein expression. In order to elucidate the role of c-Jun/AP-1 in TNF-mediated growth stimulation, the antisense (AS) technique was used. Uptake studies of oligonucleotides were performed with fibroblasts, demonstrating that incorporation of oligomers was maximal at 4 h. Oligodeoxynucleotides remained stable in these cells for up to 24 h. Treatment of fibroblasts with the AS oligonucleotide resulted in intracellular duplex formation followed by an efficient translation blockade of c-Jun/AP-1. In contrast, sense (S) and nonsense (NS) oligodeoxynucleotides failed to form intracellular duplexes and also did not interfere with translation of c-Jun/AP-1, suggesting specific elimination of c-Jun/AP-1 by the AS oligomer. Fibroblasts cultured in the presence of the AS oligonucleotide but not those cultured in the presence of the S or NS oligonucleotide failed to respond proliferatively to TNF-alpha. These findings could be confirmed by experiments with primary acute myelogenous leukemia blasts, which also demonstrated that TNF-induced growth stimulation required c-Jun/AP-1 function. Taken together, our results indicate that activation of c-Jun/AP-1 plays a pivotal role in the signaling cascade initiated by TNF, which leads to a proliferative response of its target cells.

Effects of dipyridamole and R-verapamil on in vitro proliferation of blast cells from patients with acute myelogenous leukaemia

Cytokine-dependent AML cell proliferation was investigated in 16 patients. Dipyridamole and R-verapamil caused a dose-dependent inhibition of AML cell proliferation, and for both drugs the degree of inhibition was similar when testing various haematopoietic growth factors or growth factor combinations (IL3, G-CSF, GM-CSF, G-CSF + GM-CSF, TNF-alpha + GM-CSF). TNF-alpha alone increased AML cell proliferation for five patients, whereas four patients showed unaltered or decreased proliferation. Independent of this TNF-alpha effect, R-verapamil inhibited proliferation for all AML patients in the presence of TNF-alpha, whereas dipyridamole caused only a weak inhibition.

Autonomous proliferation of leukemic cells in vitro as a determinant of prognosis in adult acute myeloid leukemia

BACKGROUND AND METHODS

A characteristic of acute myeloid leukemia is the frequent ability of the leukemic cells to sustain their own proliferation in vitro. To determine the clinical importance of this property, we measured the uptake of tritiated thymidine by leukemic cells in serum-free and cytokine-free cultures as a means of determining the rate of spontaneous proliferation in 114 patients with newly diagnosed acute myeloid leukemia. Proliferation was then classified according to three quantitative levels of activity and related to overall survival and to treatment outcome (the response to treatment, the actuarial probability of relapse, and disease-free survival) in 91 patients who were treated with chemotherapy to induce remission.

RESULTS

Of the 114 patients, 37 had low, 39 had intermediate, and 38 had high levels of proliferation. The probability of survival at three years was 36 percent among patients with low levels of proliferative activity and 3 percent among those with high levels (P < 0.001). Among the patients treated with chemotherapy, those with low rates of proliferative activity had a 68 percent rate of complete remission and a 49 percent probability of remaining free of relapse, whereas those with high rates of proliferative activity had only a 39 percent rate of complete remission (P = 0.04) and an 11 percent probability of remaining in complete remission (P = 0.009). The probability of disease-free survival at three years among the patients in complete remission after chemotherapy was 49 percent among those with low rates of proliferative activity and 9 percent among those with high rates (P = 0.004). Accordingly, patients with low rates of proliferative activity also had a significantly higher rate of overall survival (44 percent vs. 4 percent; P = 0.002). Patients whose cells had intermediate levels of proliferation in vitro had intermediate rates of survival, relapse, and disease-free survival.

CONCLUSIONS

The capacity of leukemic blasts for autonomous proliferation is associated with highly aggressive acute myeloid leukemia.

Autocrine growth factors and leukaemic haemopoiesis

Studies on the structure of haemopoiesis in acute myeloblastic leukaemia (AML) has shown the presence of a small population of malignant cells with extensive proliferative and self-renewal properties which are features of stem cells. The requirements of these cells for proliferation have been studied both in clonogenic assays in semi-solid media and in liquid suspension culture. These have demonstrated that AML clonogenic cells from the majority of patients, can be stimulated to proliferate by colony-stimulating factors (GM-CSF, G-CSF and IL-3) as well as other cytokines including interleukin-1 and interleukin-6, all of which are known to stimulate normal haemopoietic progenitors. Unlike normal haemopoietic cells, leukaemic blasts from many patients with AML express transcripts for haemopoietic growth factors including GM-CSF, G-CSF and IL-1 but not IL-3, and secrete growth factor protein. When leukaemic cells are cultured at sufficiently high density to permit cell-cell interactions, autonomous growth of clonogenic cells can be seen. Autonomous growth is related to the autocrine secretion of haemopoietic growth factors including GM-CSF, G-CSF and IL-6. The degree of autonomous colony growth is variable but approximately 70% of AML samples exhibit either partial or totally autonomous growth; the remaining cells being absolutely dependent on exogenous CSF or fail to grow in the culture systems employed. Similar patterns of growth have been found in murine haemopoietic cells lines which have been transformed as the result of the retroviral insertion of genes for GM-CSF or IL-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of interleukin-1, tumor necrosis factor-alpha, and interferon-alpha on the blast cells of acute myeloblastic leukemia

In this study, we further established the role of interleukin-1 alpha (IL-1 alpha), interleukin-1 beta, tumor necrosis factor-alpha (TNF-alpha), and interferon-alpha (IFN-alpha) as regulators of proliferation of acute myeloid leukemia (AML) cells. AML cells from 8 of 15 patients incorporated high levels of 3H-thymidine (3H-TdR) in the absence of exogenous growth factors. The spontaneous DNA synthesis could be abrogated with monospecific antibodies directed toward IL-1 alpha, IL-1 beta, or TNF-alpha, as well as with antigranulocyte-macrophage colony-stimulating factor (GM-CSF). Human recombinant GM-CSF reversed the inhibitory action of each of these antibodies and reinduced DNA synthesis in AML cells. Thus, in these cases, constitutively produced IL-1 or TNF-alpha had stimulated the synthesis of GM-CSF, which resulted in GM-CSF-dependent proliferation of AML blasts. Exogenous IL-1 up-regulated the endogenous production of GM-CSF, suggesting a positive regulation of autocrine growth factor production. We also present evidence that TNF-alpha may exert both stimulative as well as inhibitory effects on DNA synthesis in AML cells. The enhancing effect of TNF-alpha was mediated through the induction of GM-CSF production, as stimulation of DNA synthesis in AML blasts could be abrogated with anti-GM-CSF antibody. A concentration-dependent inhibitory effect of TNF-alpha on 3H-TdR incorporation into AML blasts was observed only when these cells were grown in the absence of GM-CSF. Finally, we show that human recombinant IFN-alpha is a potent inhibitor of AML cell proliferation in vitro.

Haemopoietic growth factors in acute myeloblastic and lymphoblastic leukaemia

Acute leukaemia blast cells fail to mature into terminally differentiated cells and accumulate in the haemopoietic tissues. In analogy with normal haemopoiesis, the leukaemic mass is largely non-dividing and descends from a small pool of leukaemic progenitor cells with high proliferative activity. In vitro culture methods have become powerful instruments to analyse human leukaemia progenitor cells. These techniques have in recent years been considerably improved as the result of the availability of the recombinant HGFs. Here we have summarized the current insights in the growth properties of acute leukaemia progenitor cells, derived from the application of fully defined in vitro assays. We have discussed the proliferation and maturation abilities in relation to cytogenetic abnormalities, status of growth factor receptors and the property of autocrine growth stimulation and evaluated the significance of these findings for the understanding of the pathogenesis of acute myeloblastic leukaemia and acute lymphoblastic leukaemia.

Cytokine enhancement of complement-dependent phagocytosis by macrophages: synergy of tumor necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor for phagocytosis of Cryptococcus neoformans

We have examined the regulation of complement dependent phagocytosis by macrophage-activating cytokines. Tumor necrosis factor (TNF)-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF), but not interferon-gamma, interleukin-4 or macrophage-CSF, stimulated ingestion of the encapsulated fungal pathogen Cryptococcus neoformans by resident peritoneal macrophages in vitro. This was dependent upon opsonization of the yeasts with complement, 72 h of incubation with the cytokines for maximum effect, and the obligate involvement of the macrophage CR3 receptor. TNF-alpha and GM-CSF synergized at low concentrations, resulting in dramatic up-regulation of phagocytosis when compared to either cytokine alone. Supernatants from C. neoformans-specific T cells also increased macrophage phagocytic efficiency. Finally, the administration of neutralizing mAb specific for TNF-alpha and GM-CSF increased mortality in C. neoformans-infected mice, and induced the rapid progression of disease with involvement of the brain and meninges. We conclude that TNF-alpha and GM-CSF are potent regulators of complement-dependent phagocytosis by murine macrophages. Macrophage activation with these two cytokines can completely overcome the anti-phagocytic properties of the virulent yeasts. Our results, therefore, implicate TNF-alpha and GM-CSF as important mediators of resistance to encapsulated pathogens such as C. neoformans where ingestion of the organism is a critical process in host resistance.

Biochemical events accompanying macrophage activation and the inhibition of colony-stimulating factor-1-induced macrophage proliferation by tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide

Agents that can arrest cellular proliferation are now providing insights into mechanisms of growth factor action and how this action may be controlled. It is shown here that the macrophage activating agents tumor necrosis factor-alpha (TNF alpha), interferon-gamma (IFN gamma), and lipopolysaccharide (LPS) can maximally inhibit colony stimulating factor-1 (CSF-1)-induced, murine bone marrow-derived macrophage (BMM) DNA synthesis even when added 8-12 h after the growth factor, a period coinciding with the G1/S-phase border of the BMM cell cycle. This inhibition was independent of autocrine PGE2 production or increased cAMP levels. In order to compare the mode of action of these agents, their effects on a number of other BMM responses in the absence or presence of CSF-1 were examined. All three agents stimulated BMM protein synthesis; TNF alpha and LPS, but not IFN gamma, stimulated BMM Na+/H+ exchange and Na+,K(+)-ATPase activities, as well as c-fos mRNA levels. IFN gamma did not inhibit the CSF-1-induced Na+,K(+)-ATPase activity. TNF alpha and LPS inhibited both CSF-1-stimulated urokinase-type plasminogen activator (u-PA) mRNA levels and u-PA activity in BMM, whereas IFN gamma lowered only the u-PA activity. In contrast, LPS and IFN gamma, but not TNF alpha, inhibited CSF-1-induced BMM c-myc mRNA levels, the lack of effect of TNF alpha dissociating the inhibition of DNA synthesis and decreased c-myc mRNA expression for this cytokine. These results indicate that certain biochemical responses are common to both growth factors and inhibitors of BMM DNA synthesis and that TNF alpha, IFN gamma, and LPS, even though they all have a common action in suppressing DNA synthesis, activate multiple signaling pathways in BMM, only some of which overlap or converge.

High levels of circulating soluble receptors for tumor necrosis factor in hairy cell leukemia and type B chronic lymphocytic leukemia

The presence of soluble tumor necrosis factor (TNF) binding proteins (BP) was investigated in the sera of healthy volunteer blood donors and cancer patients. Two distinct types of TNFBP, types A and B, which are immunologically related to the cellular 75-kD TNF receptor (TNFR) and the cellular 55-kD TNFR, respectively, were assessed by immunoassays using nonblocking anti-receptor antibodies and 125I-recombinant human TNF alpha. As compared to the titers observed in 25 healthy controls, TNFBP types A and B titers were found to be elevated in almost all sera obtained from patients with underlying malignant disease. The highest amounts of TNFBP were seen in the sera of patients with B cell malignancies including hairy cell leukemia (HCL) and type B chronic lymphocytic leukemia. Treatment of HCL patients with recombinant human interferon-alpha was associated with decrease of circulating TNFBP.

Effects of granulocyte-macrophage colony-stimulating factor and interleukin 6 on the growth of leukemic blasts in suspension culture

We examined the stimulatory effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 6 (IL)-6 on the in vitro proliferation of leukemic blast cells from patients with acute leukemia. Bone marrow or peripheral blood leukemic blast cells were obtained from 21 patients, including 14 cases of acute myeloblastic leukemia (AML), four cases of acute lymphoblastic leukemia (ALL), two cases of acute undifferentiated leukemia, and one case of acute mixed-lineage leukemia. The proliferation of leukemic blast cells was evaluated by measuring the incorporation of 3H-thymidine into cells incubated with various concentrations of cytokines for 3 days. GM-CSF stimulated the DNA synthesis (with greater than 2.0 stimulation index) of blast cells in 9 of 14 (64%) AML cases, two cases of acute undifferentiated leukemia and one case of acute mixed-lineage leukemia. Only two cases of AML blasts responded to IL-6 to grow in the short-term suspension cultures. GM-CSF and IL-6 did not display a synergistic effect on the growth of leukemic cells. Moreover, GM-CSF and IL-6 did not stimulate the proliferation of ALL blast cells. Binding study also revealed the specific binding of GM-CSF on the blast cells of acute undifferentiated leukemia and acute mixed-lineage leukemia. Our results indicated that leukemic blast cells of acute undifferentiated leukemia and acute mixed-lineage leukemia possessed functional GM-CSF receptors.

Stimulatory effect of tumor necrosis factor-alpha on the growth of CMK, a human megakaryoblastic leukemia cell line

Recombinant human tumor necrosis factor-alpha (TNF-alpha) was found to stimulate the growth of CMK, a human megakaryoblastic leukemia cell line. This stimulatory effect of TNF-alpha was blocked by anti-TNF-alpha antibody, but antibodies to recombinant human interleukin 3, granulocyte-macrophage colony-stimulating factor and interleukin 6 (all growth factors for CMK cells) did not reduce the stimulatory effect of TNF-alpha. Scatchard analysis showed that CMK cells expressed TNF-alpha receptors on the cell surface. The growth of CMK cells was also stimulated by lymphotoxin, which shares the same receptor as TNF-alpha. These results suggest that TNF-alpha stimulated the growth of CMK cells directly via its specific receptor.

Enhancement by transforming growth factor-beta 1 (TGF-beta 1) of the proliferation of leukemic blast progenitors stimulated with IL-3

We studied the effect of transforming growth factor-beta 1 (TGF-beta 1) on colony formation of leukemic blast progenitors from ten acute myeloblastic leukemia (AML) patients stimulated with granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), interleukin-6 (IL-6), or interleukin-1 beta (IL-1 beta). These CSFs and interleukins by themselves stimulated the proliferation of leukemic blast progenitors without adding TGF-beta 1. G-CSF, GM-CSF, and IL-3 stimulated blast colony formation in nine patients, IL-6 stimulated it in five, and IL-1 beta stimulated in four. TGF-beta 1 significantly reduced blast colony formation stimulated by G-CSF, GM-CSF, or IL-6 in all patients. In contrast, TGF-beta 1 enhanced the stimulatory effect of IL-3 on blast progenitors from three cases, while in the other seven patients TGF-beta 1 reduced blast colony formation in the presence of IL-3. To study the mechanism by which TGF-beta 1 enhanced the stimulatory effect of IL-3 on blast progenitors, we carried out the following experiments in the three patients in which it occurred. First, the media conditioned by leukemic cells in the presence of TGF-beta 1 stimulated the growth of leukemic blast progenitors, but such effect was completely abolished by anti-IL-1 beta antibody. Second, the addition of IL-1 beta in the culture significantly enhanced the growth of blast progenitors stimulated with IL-3. Third, leukemic cells of the two patients studied were revealed to secrete IL-1 beta and tumor necrosis factor-alpha (TNF-alpha) constitutively; the production by leukemic cells of IL-1 beta and TNF-alpha was significantly promoted by TGF-beta 1. Furthermore, the growth enhancing effect of TGF-beta 1 in the presence of IL-3 was fully neutralized by anti-IL-1 beta antibody. These findings suggest that TGF-beta 1 stimulated the growth of blast progenitors through the production and secretion of IL-1 beta by leukemic cells.

Practical aspects and diagnostic significance of in vitro manipulation of progenitors in human acute myeloid and lymphoid leukaemia

Since their introduction in the early seventies, in vitro culture techniques for human acute leukaemia cells have been modified and improved considerably. Primarily, this is the result of the availability of the recombinant haematopoietic growth factors (HGFs). It is now possible to evaluate HGF responses of acute leukaemia cells in colony and DNA synthesis assays under fully defined conditions. In this chapter we summarize the current insights into the growth properties of human acute leukaemia progenitor cells and evaluate the potential significance of the application of in vitro clonogenic assays for refining the diagnosis of acute leukaemia, for detecting minimal residual disease and for monitoring therapy.

Tumor necrosis factor downregulates granulocyte-colony-stimulating factor receptor expression on human acute myeloid leukemia cells and granulocytes

Tumor necrosis factor (TNF) inhibits granulocyte-colony-stimulating factor (G-CSF)-induced human acute myeloid leukemia (AML) growth in vitro. Incubation of blasts from three patients with AML in serum-free medium with TNF (10(3) U/ml), and subsequent binding studies using 125I-G-CSF reveal that TNF downregulates the numbers of G-CSF receptors by approximately 70%. G-CSF receptor numbers on purified blood granulocytes are also downmodulated by TNF. Downregulation of G-CSF receptor expression becomes evident within 10 min after incubation of the cells with TNF at 37 degrees C and is not associated with an apparent change of the dissociation constant (Kd). The TNF effect does not occur at 0 degrees C and cannot be induced by IL-2, IL-6, or GM-CSF. TNF probably exerts its effect through activation of protein kinase C (PKC) as the TNF effect on G-CSF receptor levels can be mimicked by 12-O-tetradecanoylphorbol-13- acetate. The PKC inhibitor Staurosporine (Sigma Chemical Co., St. Louis, MO) as well as protease inhibitors can completely prevent G-CSF receptor downmodulation. Thus, it appears TNF may act as a regulator of G-CSF receptor expression in myeloid cells and shut off G-CSF dependent hematopoiesis. The regulatory ability of TNF may explain the antagonism between TNF and G-CSF stimulation.