Biomedical subjects

E R Savolainen

Publications and source records attributed to E R Savolainen.

At least 19 recordsLinked to original sources

PubMed2005

The -1C to T polymorphism in the annexin A5 gene is not associated with the risk of acute myocardial infarction or sudden cardiac death in middle-aged Finnish males.

OBJECTIVE: A common polymorphism (-1C to T) in the translation initiation sequence of annexin A5 (ANV) gene has recently been associated with a decreased risk of acute myocardial infarction (AMI). The aim of the present study was to analyze the association between the ANV genepolymorphism and the risk of AMI and ischemic sudden cardiac death (SCD) in middle-aged Finnish males. MATERIAL AND METHODS: A case-control study involving three distinct groups of subjects was carried out: (1) victims of SCD (n=98), (2) survivors of AMI (n=212), and (3) randomly selected control subjects without any history of coronary heart disease (n=243). The ANV polymorphism was genotyped in each study group. RESULTS: Among the control group of healthy Finnish males the prevalence rates of the CC, CT, and TT genotypes were 83.1%, 15.2%, and 1.6%, respectively. Among the survivors of AMI, the prevalence rates of CC, CT, and TT were 79.7%, 20.3%, and 0%, respectively, and among the victims of SCD 83.7%, 16.3%, and 0%, respectively. No significant differences in the genotype or allele distributions were observed between the study groups. CONCLUSION: The -1C to T polymorphism in the ANV gene is not associated with the risk of AMI or SCD in middle-aged Finnish males.

5' Untranslated Regions↗

PubMed2001

MMP-2 and MMP-9 expression in adult and childhood acute lymphatic leukemia (ALL).

In the present study the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in acute lymphatic leukemia (ALL) is studied with immunocytochemical staining in bone marrow aspirate smears from 75 patients. The material included 20 adult and 55 pediatric ALL patients. In 65% of the adult ALL cases the immunoreactive protein for either MMP-2 or MMP-9 or for both the enzymes was seen. A statistically significant correlation (P 0.027) with MMP-2 positivity and appearance of extramedullary infiltrates was found in adult ALL, suggesting that the gelatinase activity could be related with increased extravasation of the leukemic cells in ALL. This has to be confirmed in a larger patient population. In pediatric patients there were only seven cases (12.7%) out of 55 with positive immunostaining for either of these metalloproteinases. MMP expression correlated with L2 FAB class, high-risk tumor group and T-cell immunophenotype, but not with extramedullary presentation in pediatric patients with ALL indicating basic biological differences between adult and childhood ALL.

Adolescent↗

PubMed2001

p53 and redox state in etoposide-induced acute myeloblastic leukemia cell death.

We investigated whether p53, being a redox-sensitive protein, has a role in the responsiveness of AML cells to etoposide. Two subclones of the OCI/AML-2 cell line, the etoposide-sensitive (ES) and the etoposide-resistant (ER), were used as models. Sensitivity to etoposide was measured by trypan blue and annexin V assays. Etoposide-induced peroxide formation was associated with the induction of cell death. Evident expression of mutated p53 was observed in both subclones in basal growth conditions as analysed by Western blotting and flow cytometry. After etoposide exposure for up to 24 hours, some nuclear accumulation of p53 was observed in the ER subclone, as analysed by Western blotting. The conformation of p53, however, was not changed from mutated toward wild-type during exposure in either of the subclones as analysed by flow cytometry. In conclusion, etoposide-induced change in cellular redox state was associated with apoptosis, but was not a sufficient stimulus for p53 to make its conformation active. Thus, mutated p53 seems to have no role in etoposide-induced apoptosis.

Antineoplastic Agents, Phytogenic↗

PubMed2001

c-erbB-2 positivity is a factor for poor prognosis in breast cancer and poor response to hormonal or chemotherapy treatment in advanced disease.

The aim of this work was to evaluate the prognostic and predictive values of c-erbB-2 in breast cancer. 650 patients were enrolled. The amplification/overexpression of c-erbB-2 from fresh frozen or paraffin-embedded breast tumour tissue samples was analysed by polymerase chain reaction (PCR) technique (75%), immunohistochemically (17%) or by Southern blot analysis (8%). 126 patients (19%) were positive for c-erbB-2. 148 patients developed metastatic disease, but only 35 were positive for c-erbB-2. Positivity for c-erbB-2 was significantly associated with node positivity, large tumour size, high grade of malignancy, low receptor status, postmenopausal status, and with a shorter overall survival. In multivariate regression analysis, only tumour size and nodal involvement were risk factors for poor survival when analysed separately together with c-erbB-2 and receptor status. Metastatic patients with c-erbB-2 positivity had a significantly shorter survival and disease-free survival (DFS) than the c-erbB-2-negative patients. 29 advanced patients with c-erbB-2 positivity showed a poor response rate to hormonal, non-anthracycline-based and anthracycline-based therapies. Positivity for the c-erbB-2 is a poor prognostic factor in breast cancer, but it also emerges as predictive of the response to hormonal or chemotherapy treatment once the disease has recurred.

Antineoplastic Agents, Hormonal↗

PubMed2001

Regulation of the acute myeloid leukemia cell line OCI/AML-2 by endothelial nitric oxide synthase under the control of a vascular endothelial growth factor signaling system.

It is generally accepted that the vascular endothelial growth factor (VEGF) signal system has no role in the maintenance of normal blood cell formation, although it obviously regulates the development of primitive hematopoiesis during an early stage of embryogenesis. The VEGF signaling pathway, however, might have some role in malignant hematopoiesis, since malignant hematopoietic cells, including acute myeloid leukemia (AML) cells, have been shown to express VEGF and its receptors. In endothelial cells, the VEGF/Flk-1/KDR signal system is a very important generator of nitric oxide (NO) through the activation of its downstream effectors phosphatidylinositol-3-OH-kinase (PI3-K), Akt kinase and endothelial NO synthase (eNOS). It is known that NO regulates hematopoiesis and modulates AML cell growth. The role of the VEGF signaling pathway in the control of AML cell growth through eNOS, however, has not been studied. By using the OCI/AML-2 cell line, which expresses VEGF receptor-2, ie Flk-1/KDR, eNOS and VEGF, as analyzed by flow cytometry, and produces VEGF into growth medium, as analyzed by ELISA, we showed that the Akt kinase and NOS activities in these cells were decreased by the inhibitors of VEGF, Flk-1/KDR and PI3-K, and NOS activity also by the direct inhibitor of NOS. The decreased NOS activity led to inhibition of clonogenic cell growth and, to some extent, induction of apoptosis. We also found that blast cells of bone marrow samples randomly taken from 14 AML patients uniformly expressed Flk-1/KDR and to varying degrees eNOS and VEGF, as analyzed by immunohistochemistry. We conclude that autocrine VEGF through Flk-1/KDR, by activating eNOS to produce NO through PI3-K/Akt kinase, maintains clonogenic cell growth in the OCI/AML-2 cell line. Since the patient samples did not express VEGF in all cases, it is possible that in vivo the regulatory connection between these two signal systems is also mediated via endocrine VEGF in addition to autocrine or paracrine VEGF.

Acute Disease↗

PubMed2001

HFE mutations do not account for transfusional iron overload in patients with acute myeloid leukemia.

BACKGROUND: Hereditary hemochromatosis (HH) is a HFE gene-linked disorder affecting 1 of 200 to 400 persons in white populations. It has been proposed that patients with a hematologic malignancy who are receiving frequent RBC transfusions should be screened for HFE mutations. This would identify C282Y homozygotes, who have a high risk of developing severe iron overload. STUDY DESIGN AND METHODS: DNA samples from 128 controls and 23 adult long-term survivors of acute myeloid leukemia (AML) treated at the Oulu University Hospital (Oulu, Finland) from 1987 to 2000 were examined for the presence of the C282Y and H63D mutations in HFE. All the patients were severely iron-overloaded, as determined from high serum ferritin values and/or increased storage iron in bone marrow. Phlebotomies were performed in five patients because of the symptoms of iron overload. DNA extracted from the blood was used to amplify HFE gene fragments by the PCR method, after which the amplification products were digested with restriction endonucleases SnaB I and Bcl I, and the restriction fragments were analyzed on agarose gels. RESULTS: No chromosomes with the C282Y mutation were found among the AML patients, and 5 patients (21.7%) were heterozygous for the H63D mutation. In the control group, 13 persons (10.2%) were heterozygous for the C282Y mutation and 26 (20.3%) for the H63D mutation, including 3 C282Y/H63D double heterozygotes. CONCLUSION: HFE mutations do not account for the harmful iron overload that develops in AML patients who receive large quantities of RBC concentrates after intensive chemotherapy.

Acute Disease↗

PubMed2000

Induction of mitochondrial manganese superoxide dismutase confers resistance to apoptosis in acute myeloblastic leukaemia cells exposed to etoposide.

We investigated the possible roles of mitochondrial manganese superoxide dismutase (MnSOD) and bcl-2 in etoposide-induced cell death in acute myeloblastic leukaemia (AML) using two subclones of the OCI/AML-2 cell line, the etoposide-sensitive (ES) and the etoposide-resistant (ER), as models. Cell death after 24 h exposure to 10 micromol/l etoposide was about 60% and 70% in the ES subclone and about 20% and 25% in the ER subclone, when analysed by trypan blue and annexin V respectively. Cytochrome c efflux from mitochondria to cytosol was observed after 4 h of exposure in both subclones, whereas the activation of caspase-3 was not detectable until after 12 h of exposure in the ES subclone and 24 h of exposure in the ER subclone, using Western blotting. The decrease in mitochondrial membrane potential, when analysed by the JC-1 probe fluorocytometrically, also appeared to take place later in the ER than in the ES subclone. Both subclones showed evident basal expression of MnSOD and bcl-2 by Western blotting. Etoposide caused a potent induction of MnSOD, more than 400% at 12 h, in the ER but not in the ES subclone. No significant change in bcl-2 expression could be observed in either of the subclones during exposure to etoposide when analysed by Western blotting or flow cytometry. In conclusion, we suggest that MnSOD might have a special role in the protection of AML cells against etoposide-induced cell death. Although unable to influence the cytochrome c efflux to cytosol, MnSOD might prevent the disruption of mitochondrial membrane potential, which evidently leads to cell death by releasing various activators of apoptosis.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Cellular redox state and its relationship to the inhibition of clonal cell growth and the induction of apoptosis during all-trans retinoic acid exposure in acute myeloblastic leukemia cells.

BACKGROUND AND OBJECTIVE: All-trans retinoic acid (ATRA) induces growth arrest and apoptosis in acute myeloblastic leukemia (AML) cells. Since cellular redox state regulates these events, we were interested in studying whether it has any role in the responsiveness of AML cells to ATRA. DESIGN AND METHODS: Two human AML cell lines, the ATRA-sensitive OU-AML-3, and the ATRA-resistant OU-AML-7, were used as models. Clonogenic cell culture assay, annexin V method, and measurement of mitochondrial membrane potential were used for the determination of cell growth and apoptosis. Peroxide formation was analyzed by flow cytometry, glutathione and g-glutamylcysteine synthetase (g-GCS) activity was determined spectrophotometrically, and the expression of manganese superoxide dismutase (MnSOD) by Western blotting. RESULTS: ATRA inhibited clonogenic cell growth and induced apoptosis particularly in OU-AML-3 cells. The OU-AML-7 cells had a higher basal level of glutathione and g-GCS activity than the OU-AML-3 cells. ATRA enhanced the generation of peroxides after 24h exposure, which was more prominent in the sensitive than the resistant cell line and was not preventable by N-acetyl-L-cysteine. ATRA also increased the activity of g-GCS, which was associated with increased intracellular glutathione in the resistant cell line, while the glutathione level was maintained in the sensitive cell line. During ATRA exposure, MnSOD was induced in the sensitive cell line, but not until after 72 h. Buthionine sulfoximine significantly increased the inhibitory effect of ATRA on colony formation in both cell lines, but only marginally enhanced the effect of ATRA on the induction of apoptosis. INTERPRETATION AND CONCLUSIONS: The balance between oxidative and antioxidative actions of ATRA, as well as the basal redox state of the cells seem to have a definite influence on the responsiveness of AML cells to ATRA.

Apoptosis↗

PubMed1999

The soluble form of interleukin-6 receptor modulates cell proliferation by acute myeloblastic leukemia blast cells.

As interleukin-6 (IL-6) has been shown to have diverse effects on blast cell growth in acute myeloblastic leukemia (AML), and as a soluble (s) form of IL-6 receptor (IL-6R) agonizes IL-6 effects in many cell types, we investigated whether sIL-6R was able to modulate clonogenic blast cell growth in AML. The proliferation responses of eight autonomously growing AML cell lines and eight primary AML blast cell samples were compared with their IL-6 and sIL-6R expression. Only three of the 16 AML samples were influenced by IL-6, two of them being stimulated and one inhibited by it. The sIL-6R-induced responses were more frequent, however, and, in contrast to those by IL-6, always stimulatory: clonogenic cell growth in six of the 16 AML samples was stimulated by sIL-6R treatment. All the cell lines and four of the seven primary blast cell samples analyzed expressed IL-6, and the expression was associated with unresponsiveness to exogenous IL-6. sIL-6R was also frequently expressed by AML cells: only one of the samples was negative for it. However, there was no correlation between sIL-6R expression and the responsiveness of cells to exogenous sIL-6R. The work presented here shows that sIL-6R is able to stimulate blast cell growth in AML. As AML blast cells are provided by exogenous IL-6 and sIL-6R in a bone marrow environment, and as many of them also express IL-6 and sIL-6R themselves in vitro, it is possible that signaling through the IL-6/sIL-6R system plays a role in maintaining their growth also in vivo.

Adolescent↗

PubMed1999

Protection of acute myeloblastic leukemia cells against apoptotic cell death by high glutathione and gamma-glutamylcysteine synthetase levels during etoposide-induced oxidative stress.

BACKGROUND: Etoposide mediates its cytotoxicity by inducing apoptosis. Thus, mechanisms which regulate apoptosis should also affect drug resistance. Oxidants and antioxidants have been shown to participate in the regulation of apoptosis. We were interested in studying whether responsiveness of acute myeloblastic leukemia (AML) cells to etoposide is mediated by oxidative stress and glutathione levels. PATIENTS AND METHODS: Two subclones of the OCI/AML-2 cell line which are etoposide-sensitive (ES), and etoposide-resistant (ER), were established by the authors at the University of Oulu, and used as models. Assays for apoptosis included externalization of phosphatidylserine (as evidenced by annexin V binding), and caspase activation as indicated by cleavage of poly(ADP-ribose)polymerase (Western blotting). Peroxide formation was analyzed by flow cytometry. Glutathione and gamma-glutamylcysteine synthetase (gamma-GCS) levels were determined spectrophotometrically and by Western blotting, respectively. RESULTS: Etoposide-induced apoptosis was evident 12 hours after treatment in the ES subclone, but was apparent in the ER subclone only after 24 hours. The basal glutathione and gamma-GCS levels were higher in the ER than the ES subclone. Etoposide increased peroxide formation in both subclones after 12-hour exposure. Significant depletion of glutathione was observed in the ES subclone during etoposide exposure, while glutathione levels were maintained in the ER subclone. In neither of the subclones was induction of gamma-GCS observed during 24-hour exposure to etoposide. Furthermore, the catalytic subunit of gamma-GCS was cleaved during apoptosis, concurrent with depletion of intracellular glutathione. When glutathione was depleted by treatment with buthionine sulfoximine, a direct inhibitor of gamma-GCS, the sensitivity to etoposide was increased, particularly in the ER subclone. CONCLUSIONS: The results underline the significance of glutathione biosynthesis in the responsiveness of AML cells to etoposide. The molecular mechanisms mediating glutathione depletion during etoposide exposure might include the cleavage of the catalytic subunit of gamma-GCS.

Antineoplastic Agents, Phytogenic↗

PubMed1999

p53 status of newly established acute myeloid leukaemia cell lines.

We analysed the status of the p53 gene and protein in eight newly established acute myeloid leukaemia (AML) cell lines representing blast cells of either de novo leukaemia patients in first remission or patients with relapsed and chemotherapy-resistant disease causing their death. There were no mutations in the p53 gene in any of the cell lines as analysed by single-strand conformation polymorphism of amplified exons 5-8. However, the p53 protein was clearly and consistently expressed in all of these cell lines, as shown by immunohistochemistry, Western blotting and flow cytometry. The consistently expressed p53 protein was located in both the nucleus and the cytoplasm of all the cell lines and, as shown by flow cytometry, it was mostly in a conformation typical of the mutated protein. These AML cell lines offer a tool for studying the production and function of the p53 protein and its possible role in cell cycle regulation and chemoresistance as well as in the regulation of apoptosis in AML.

Adult↗

PubMed1999

Flt-3 ligand does not induce the growth of peripheral blood granulocyte-macrophage colony-forming cells in myeloproliferative disorders.

Flt-3 ligand (FL) is a growth factor (GF) which might have clinical use as a mobilizer of stem and progenitor cells into peripheral blood (PB) in autologous transplantations of various malignant haematological diseases, unless FL stimulates the growth of malignant cells in these diseases. The present study evaluated the effects of FL on the proliferation of granulocytemacrophage (GM) progenitor cells collected from PB of 24 patients with chronic myeloproliferative disorders (MPDs) by using a methylcellulose assay in serum-free culture conditions. It was shown that FL as a single factor had no stimulatory effect on GM colony formation either in the whole MPD group or in the MPD subgroups, which comprised 9 patients with essential thrombocythaemia, 7 with polycythaemia vera and 8 with chronic myelogenous leukaemia. No increase in GM colony formation was observed, either, when FL was used in combination with other GFs, such as mast cell growth factor (MGF), granulocyte-colony stimulating factor (G-CSF), GM-CSF or interleukin-3 (IL-3). GM-CSF and IL-3 were the only single GFs which significantly increased GM colony formation in the whole MPD group. As a conclusion, FL does not seem to induce GM colony formation of MPDs alone or in combination with G-CSF in in vitro colony assays.

Adult↗

PubMed1999

Human Emt tyrosine kinase is specifically expressed both in mature T-lymphocytes and T-cell associated hematopoietic malignancies.

The pattern of expression of the human Emt tyrosine kinase was established in healthy individuals and hematological malignancies by RT-PCR from bone marrow and blood samples, fractionated into T-cells, B-cells, monocytes, granulocytes and thrombocytes. Previously studied mostly in murine samples or established human cell lines, the in vivo correlation was here further clarified. In hematopoietic cells, expression of the EMT gene was associated with T-cell fractions, but Emt was not detected in cord blood CD34+ cells. In fetal tissues, Emt mRNA was strongly expressed in thymus, no expression could be detected in non-hematopoietic tissues. The expression pattern of the 48 malignant bone marrow samples (23 ALL, 1 PLL, 9 AML, 7 CLL and 8 CML cases) paralleled the findings from normal hematopoietic cells: 9/11 T cell associated ALLs, as well as one T-PLL sample, but only 1/12 samples of B-ALL expressed Emt markedly. Only minor signs of Emt expression could be shown in the AML samples, while CML and CLL samples were totally devoid of expression. In addition the Emt protein could be detected by Western blotting from T-lymphocytes and T-cell associated ALL, corresponding to mRNA expression. In conclusion, Emt (Itk) is T-cell associated both in normal and leukemic cells, but is not expressed in cord blood CD34+ cells, suggesting that Emt expression is switched on only later in T-cell development. In addition, an association between Emt and CD2 expression remains even in malignancies.

Adolescent↗

PubMed1999

An association between mitochondrial function and all-trans retinoic acid-induced apoptosis in acute myeloblastic leukaemia cells.

The present study investigated whether all-trans retinoic acid (ATRA)-induced apoptosis in acute myeloblastic leukaemia (AML) is related to changes in mitochondrial function. Two human AML cell lines, OU-AML-3 and OU-AML-7, known to be inducible to time-dependent apoptosis of varying degrees by ATRA, were used. Apoptosis induced by ATRA was shown to be a slow event. It was detected by the DNA electrophoretic method and cytofluorimetrical annexin V assay after 48 h exposure, and by morphology and polyADPribose polymerase (PARP) cleavage after 72 h exposure of AML cells to ATRA. The efflux of mitochondrial cytochrome c to cytosol was notable in Western blotting after 48 h exposure of the cells to ATRA and was observed before the drop in the mitochondrial membrane potential, which only took place after 72 h exposure, when measured by flow cytometry and a JC-1 probe. The apoptotic events in mitochondria were more evident in the OU-AML-3 than the OU-AML-7 cell line. This might relate to the different bcl-2 contents of the cell lines: the basic bcl-2 levels of the OU-AML-7 cell line were almost twofold compared to that of the OU-AML-3 cell line, as analysed by the ELISA method. However, both of the cell lines showed progressive down-regulation of bcl-2, which began after 12-24 h exposure of the cells to ATRA as determined by ELISA, Western blotting and flow cytometry. The present results show that mitochondria have a role in ATRA-induced apoptosis in AML cells and down-regulation of bcl-2 is related to it. In view of the previously published studies, the present results underline the fact that the timing of apoptotic events, such as fragmentation of DNA, externalization of phosphatidylserine, cytochrome c efflux, change in mitochondrial membrane potential and cleavage of PARP, are, to a notable extent, cell type and inducer-dependent.

Apoptosis↗

PubMed1998

Acute myeloblastic leukaemia cells produce soluble interleukin 6 receptor by a mechanism of alternative splicing.

The aim of the present work was to investigate whether acute myeloblastic leukaemia (AML) blast cells express a soluble (s) form of interleukin 6 (IL-6) receptor (R), and if they do, what is the mechanism of production. Eight AML patient cell lines and 25 primary AML blast cell samples were investigated. The cell lines secreted high quantities of sIL-6R into their culture medium when examined by enzyme-linked immunosorbent assay (ELISA). To determine whether sIL-6R is synthesized by a mechanism of alternative splicing, RNA was analysed from all the AML blast cell samples by using reverse transcription polymerase chain reaction. In this method, primer sites flanking the transmembrane domain were utilized and the alternatively spliced IL-6R mRNA was distinguished from the non-spliced transcript form by size. All the cell lines and 64% of the primary blast cell samples expressed the alternatively spliced IL-6R mRNA. To confirm the phenomenon of alternative splicing at protein level, cytoplasmic protein fractions of the cell lines were investigated by using a sensitive adaptation of the Western blot method. All the cell lines expressed two IL-6R proteins sized 80 and 50 kDa and corresponding to the membraneous and soluble forms of IL-6R, respectively. In conclusion, the results obtained at both mRNA and protein levels strongly support alternative splicing as a mechanism of sIL-6R production in AML. Because sIL-6R modulates the effects of IL-6 on target cells, differences in sIL-6R expression levels may partially explain the previously observed diversity in IL-6-induced growth responses in AML

Adolescent↗

PubMed1998

Signaling through interleukin-6 receptor supports blast cell proliferation in acute myeloblastic leukemia.

The role of the interleukin-6/interleukin-6 receptor (IL-6/IL-6R) system in regulating blast cell growth in 8 acute myeloblastic leukemia (AML) patient-derived cell lines was investigated. As they all expressed IL-6R and as none of them responded to exogenous IL-6 under conventional serum-supplemented culture conditions, we investigated whether signaling through IL-6R plays any role in maintaining their spontaneous colony growth. This was done by treating the cells with monoclonal antibodies made against the ligand-specific IL-6R alpha-chain or the signal transducer gp130. In serum-supplemented cultures inhibition of gp130 function did not affect the cell line growth, whereas anti-IL-6R alpha-chain antibody reduced colony growth. While some of the cell lines also showed similar growth characteristics in a serum-free environment, some others changed their growth pattern and stopped responding to anti-IL-6R alpha-chain treatment. At the same time, these cell lines also began to respond to exogenously added IL-6 and, interestingly, were stimulated by anti-gp130 antibody. Hence, in some of the blast cells, clonogenic cell growth seemed to be also negatively controlled by an endogenously produced growth-depressing cytokine or cytokines that utilize gp130. All the cell lines, whether cultured in the presence or absence of serum expressed IL-6 both at mRNA and protein level. The current results indicate that AML cells can use IL-6 as a growth stimulating factor, supplied either paracrinely or autocrinely. This could implicate the use of anti-IL-6R alpha-chain antagonists in AML treatment, not IL-6.

Adult↗

PubMed1998

Expression of interleukin-6 (IL-6) receptor gene in acute myeloblastic leukemia and response of leukemic cells to exogenous IL-6. A comparative study between cell line cells and corresponding native cells.

As interleukin (IL-6) ahs been reported to have diverse effects on acute myeloblastic leukemia (AML) blast cell growth, we investigated whether the level of IL-6 receptor (IL-6R) expression by blast cells is associated with their susceptibility to proliferate in response to exogenous IL-6. For absolute quantification of IL-6R transcript numbers, we established a quantitative IL-6R reverse transcription polymerase chain reaction (RT-PCR) method with an internal RNA standard. In the present work, two types of AML blast cells were investigated, namely autonomously growing cell line cells (n = 8) and non cultured native blast cells (n = 20), including those from which the cell lines originate. The native blast cells expressed an average of 2.8 x 10(7) +/- 1.9 x 10(7) IL-6R transcripts in one microgram of total cellular RNA, whereas the expression by the cell line cells was significantly more abundant, the value being 8.3 x 10(7) +/- 2.8 X 10(7) (P < 0.001). The proliferation responses were evaluated by exposing the cells to IL-6 (1000 U/ml) in a clonogenic cell culture assay and, in the case of the cell line cells, in a long-term suspension culture assay as well. None of the autonomously growing cell lines responded to exogenous IL-6, whereas the native blast cell showed either stimulatory, inhibitory or neutral responses. Thus, the IL-6R expression level did not predict whether the cells proliferated in response to exogenous IL-6, which shows that IL-6R quantification cannot be used as a screening test prior to possibly applying this cytokine to clinical use in AML therapy.

Adolescent↗

PubMed1997

All-trans retinoic acid induces apoptosis in acute myeloblastic leukaemia cells.

The effect of all-trans retinoic acid (ATRA) on leukaemia cell differentiation, proliferation and induction of apoptosis was studied by using autonomously growing blast cells isolated from eight patients with acute myeloblastic leukaemia (AML) either at diagnosis (n=4) or at relapse (n=4). No morphological or functional differentiation induced by ATRA was observed in any of the cases studied. In cell cultures, inhibition of leukaemia cell growth by ATRA was obvious, especially in the case of clonogenic cells, and it was both time- and concentration-dependent. Induction of apoptosis was more difficult to achieve. The cells retained over 90% viability in suspension when the ATRA exposure at any of the concentrations studied was 48 h or less. When the time of exposure to ATRA was longer than 48 h, the viability of the cells decreased in a concentration-dependent manner. Apoptosis was observed morphologically in each of the AML cases with 10(-5) to 10(-8) M ATRA, if the incubation time of cells in ATRA was 72 h. The percentage of apoptotic cells increased with increasing ATRA concentrations from 12+/- 9% of 10(-8) M ATRA to 78+/-12% of 10(-5) M ATRA. The DNA electrophoretic method was able to detect apoptosis in all the AML samples exposed to 10(-7) and 10(-6) ATRA for 48 h and occasionally in cases where lower concentrations and longer exposure time were used. In conclusion, the present study shows that it is possible to induce apoptotic leukaemia cell death in vitro with ATRA in AML, and this effect is dependent on both concentration and exposure time.

Journal Article↗