Expression and release of adhesion molecules by human acute myelogenous leukemia blasts

Monocytic Differentiation in Acute Myeloid Leukemia Cells: Diagnostic Criteria, Biological Heterogeneity, Mitochondrial Metabolism, Resistance to and Induction by Targeted Therapies

We review the importance of monocytic differentiation and differentiation induction in non-APL (acute promyelocytic leukemia) variants of acute myeloid leukemia (AML), a malignancy characterized by proliferation of immature myeloid cells. Even though the cellular differentiation block is a fundamental characteristic, the AML cells can show limited signs of differentiation. According to the French-American-British (FAB-M4/M5 subset) and the World Health Organization (WHO) 2016 classifications, monocytic differentiation is characterized by morphological signs and the expression of specific molecular markers involved in cellular communication and adhesion. Furthermore, monocytic FAB-M4/M5 patients are heterogeneous with regards to cytogenetic and molecular genetic abnormalities, and monocytic differentiation does not have any major prognostic impact for these patients when receiving conventional intensive cytotoxic therapy. In contrast, FAB-M4/M5 patients have decreased susceptibility to the Bcl-2 inhibitor venetoclax, and this seems to be due to common molecular characteristics involving mitochondrial regulation of the cellular metabolism and survival, including decreased dependency on Bcl-2 compared to other AML patients. Thus, the susceptibility to Bcl-2 inhibition does not only depend on general resistance/susceptibility mechanisms known from conventional AML therapy but also specific mechanisms involving the molecular target itself or the molecular context of the target. AML cell differentiation status is also associated with susceptibility to other targeted therapies (e.g., CDK2/4/6 and bromodomain inhibition), and differentiation induction seems to be a part of the antileukemic effect for several targeted anti-AML therapies. Differentiation-associated molecular mechanisms may thus become important in the future implementation of targeted therapies in human AML.

Endocan, a putative endothelial cell marker, is elevated in preeclampsia, decreased in acute pyelonephritis, and unchanged in other obstetrical syndromes

Objective: Endocan, a dermatan sulphate proteoglycan produced by endothelial cells, is considered a biomarker for endothelial cell activation/dysfunction. Preeclampsia is characterized by systemic vascular inflammation, and endothelial cell activation/dysfunction. Therefore, the objectives of this study were to determine whether: (1) plasma endocan concentrations in preeclampsia differ from those in uncomplicated pregnancies; (2) changes in plasma endocan concentration relate to the severity of preeclampsia, and whether these changes are specific or observed in other obstetrical syndromes such as small-for-gestational age (SGA), fetal death (FD), preterm labor (PTL) or preterm prelabor rupture of membranes (PROM); (3) a correlation exists between plasma concentration of endocan and angiogenic (placental growth factor or PlGF)/anti-angiogenic factors (soluble vascular endothelial growth factor receptor or sVEGFR-1, and soluble endoglin or sEng) among pregnancies complicated by preeclampsia; and (4) plasma endocan concentrations in patients with preeclampsia and acute pyelonephritis (both conditions in which there is endothelial cell activation) differ.

Method: This cross-sectional study included the following groups: (1) uncomplicated pregnancy (n = 130); (2) preeclampsia (n = 102); (3) pregnant women without preeclampsia who delivered an SGA neonate (n = 51); (4) FD (n = 49); (5) acute pyelonephritis (AP; n = 35); (6) spontaneous PTL (n = 75); and (7) preterm PROM (n = 64). Plasma endocan concentrations were determined in all groups, and PIGF, sEng and VEGFR-1 plasma concentrations were measured by ELISA in the preeclampsia group.

Results: (1) Women with preeclampsia had a significantly higher median plasma endocan concentration than those with uncomplicated pregnancies (p = 0.004); (2) among women with preeclampsia, the median plasma endocan concentration did not differ significantly according to disease severity (p = 0.1), abnormal uterine artery Doppler velocimetry (p = 0.7) or whether diagnosis was made before or after 34 weeks gestational age (p = 0.3); (3) plasma endocan concentration in women with preeclampsia correlated positively with plasma anti-angiogenic factor concentrations [sVEGFR-1: Spearman rho 0.34, p = 0.001 and sEng: Spearman rho 0.30, p = 0.003]; (4) pregnancies complicated by acute pyelonephritis with bacteremia had a lower median plasma endocan concentration than pregnancies complicated by acute pyelonephritis without bacteremia (p = 0.004), as well as uncomplicated pregnancies (p = 0.001); and (5) there was no significant difference in the median plasma endocan concentration between uncomplicated pregnancies and those complicated by FD, delivery of an SGA neonate, PTL or preterm PROM (other members of the “great obstetrical syndromes”; each p > 0.05).

Conclusion: Median maternal plasma endocan concentrations were higher preeclampsia and lower in acute pyelonephritis with bacteremia than in uncomplicated pregnancy. No significant difference was observed in the median plasma endocan concentration between other great obstetrical syndromes and uncomplicated pregnancies. The difference in the direction of change of endocan in preeclampsia and acute pyelonephritis with bacteremia may be consistent with the view that both disease entities differ in pathogenic mechanisms, despite their associations with systemic vascular inflammation and endothelial cell activation/dysfunction.

Shear stress-mediated adhesion of acute myeloid leukemia and KG-1 cells to endothelial cells involves functional P-selectin

Acute myeloid leukemia (AML) shows malignant behavior through the ability of immature cells to circulate in blood and to invade peripheral tissues. Whereas binding of human AML cells to endothelial cells (ECs) through E-selectin has been shown to occur using classical adhesion assays, little is known about the ability of endothelial P-selectin to support this process. We therefore characterized the ability of AML blasts and KG-1 cells to bind to endothelial selectin type ligands. Flow cytometry revealed that, in addition to various integrin adhesion receptors, AML cells regularly express the P-selectin glycoprotein ligand (PSGL)-1, a ligand for P- and E-selectin on ECs. In parallel flow chambers, AML cells both rolled and adhered to TNF-alpha pretreated human umbilical vein endothelial cells (HUVECs). Pretreatment of HUVECs with anti-P- or anti-E-selectin function blocking antibodies significantly reduced both, rolling and subsequent arrest of primary AML cells. Intravital microscopy of i.v. injected fluorescence-labeled KG-1 cells into P-selectin deficient or wild type mice confirmed a significant role of endothelial P-selectin in the binding of human primary AML cells to ECs also in vivo. Thus, the currently available data suggest a role of P- and E-selectin in coordinated circulation of AML cells. Thus, P- or E-selectin mediated adhesion of AML cells may provide a target for the development anti-leukemic therapies.

beta2 Integrins are characteristically absent in acute promyelocytic leukemia and rapidly upregulated in vivo upon differentiation with all-trans retinoic acid

Although little is known about migration of hematopoietic stem cells and their neoplastic counterparts into tissues and peripheral blood, adhesion proteins likely play an important role. We studied 339 patients with acute myelogenous leukemia (AML) to discern the relationship between adhesion protein expression, circulating blasts, and white blood cell (WBC) count. Expression levels of CD11b and CD11c strongly correlated with increased WBC count, independent of FAB subtype (p<0.0001). However, 93% (25/27) of cases of AML-M3 completely lacked beta2 integrin expression, compared to 11% (35/312) of the non-M3 cases (p<0.0001). Seven of the 27 patients with AML-M3 were followed during standard induction therapy with ATRA. Within 3 days, weak CD11c became detectable, followed by CD11b and CD11a. Our data suggest an important link between beta2 integrin expression and the level of circulating leukemic cells in AML. We demonstrate the clinical usefulness of a panel of beta2 integrins (CD11a, CD11b and CD11c) in accurate prediction of AML-M3, and recommend inclusion of this immunophenotypic analysis to identify patients who require ATRA therapy. Finally, we illustrate the rapidity at which AML-M3 blasts up-regulate beta2 integrins, and suggest a possible association between this finding and the tissue infiltration that characterizes the "ATRA syndrome".

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.

Low l -selectin (CD62L) expression in acute myeloid leukemia correlates with a bad cytogenetic risk

OBJECTIVES

Interactions between hemopoietic cells and the stromal microenvironment or immunoreactive cells are mediated by specific cell surface receptors. The expression of those molecules may alter the adhesive qualities (mobility and homing) as well as immune response behavior of leukemic blasts. L-Selectin (CD62L) is suggested to play a role in the redistribution and homing of hemopoietic progenitor cells to the bone marrow (BM). Down-regulation of L-selectin is responsible for mobilization of blasts from the BM into the circulation and ligation of L-selectin stimulates proliferation of progenitor cells. This could have an influence on the process of leukemia.

METHOD

We have studied the expression of L-selectin on mononuclear BM cells of 36 acute myeloid leukemia (AML) patients at first diagnosis by FACS analysis using a directly fluorescein isothiocyanate conjugated antibody (clone DRE G56).

RESULTS

On average the patients presented with 88% blasts in the BM. The expression tended to be higher in primary (p) AML compared with secondary (s) AML. L-Selectin was very heterogenously expressed in all FAB groups. Highest expression was found in cases with AML-M4 with four of nine cases presenting with an inv(16) karyotype. Separating our patient cohort in cytogenetic risk groups we could detect a significantly higher expression of L-selectin in cases with a 'good risk' karyotype and a very low expression in cases with a 'bad risk' karyotype (P = 0.037). Comparing patients who achieved remission after double induction therapy (responders) with patients who showed persisting disease (non-responders) we found a higher percentage of L-selectin+ cases or cells in the responder group than in the non-responder group, although the differences were not significant because of only five cases in the 'non-responder' group. Evaluating cut-off points greatest differences in relapse-free survival probabilities were found in patients who presented with > or = 30% L-selectin+ BM cells compared with cases with < 30%: 86% of cases with > or = 30% L-selectin+ cells were still in remission after a mean follow up time of only 8 months compared with only 46% in the group with < 30% L-selectin+ cells.

CONCLUSIONS

We can conclude that (i) expression of L-selectin on AML blasts is variable. This reveals the great diversitiy of immunophenotypes in AML and might contribute to identify individual blast phenotypes in order to detect minimal residual disease in remission. (ii) Low L-selectin expression correlates with a bad cytogenetic risk, with a lower probability to achieve remission and with a shorter relapse-free survival time. This might reflect a decreased homing of the blasts to the BM as well as an impaired cytotoxic T-cell reaction against leukemic cells. The expression of L-selectin on leukemic blasts might be influenced by different cytokine therapies (e.g. with interferon alpha) and this might result in an altered hematologic reconstitution after cytotoxic therapies as well as in an altered immunologic recognition of blasts.

Soluble l-selectin (sCD62L) in relapsed childhood acute lymphoblastic leukaemia

Soluble l-selectin (sCD62L) plasma concentrations at diagnosis and outcome were investigated in 193 children at first relapse of acute lymphoblastic leukaemia (ALL) after treatment according to the Berlin-Frankfurt-Münster relapsed ALL multicentre trials, ALL-REZ BFM 95 and 96. sCD62L was low (< fifth paediatric reference percentile) in 63 (33%) and high (> 95th percentile) in 36 (19%) children, and was independent of remission duration, sex, BCR-ABL fusion or extramedullary disease. High sCD62L was associated with circulating blasts and T-cell phenotype. More initial adverse events occurred in children with high and low levels of sCD62L (23 out of 99) than in those with normal levels (9 out of 94, P = 0.018). Among 75 worst-prognosis patients (risk groups S3/S4, isolated bone marrow relapse occurring less than 6 months after elective cessation of front-line therapy, or T-cell phenotype with bone marrow involvement), 27 had low sCD62L and decreased event-free survival (EFS) probability (PEFS5 = 0.09 at 5 years) and duration (219 d) compared with normal sCD62L (29 out of 75, PEFS5 = 0.24, 640 d, P = 0.01). Low (44 out of 118), normal (72 out of 118), and high (19 out of 118) sCD62L non-S3/S4 patients fared similarly (average PEFS5 = 0.45, 1369 d; P = 0.5). Low sCD62L may be a marker of malignant blasts replacing normal sCD62L-producing haematopoietic cells. In children with first relapse of ALL and worst prognosis, plasma sCD62L may be useful for risk-adapted stratification.

Serum levels of angiogenin, basic fibroblast growth factor and endostatin in patients receiving intensive chemotherapy for acute myelogenous leukemia

Angiogenesis seems to be important both in the pathogenesis of acute myelogenous leukemia (AML) and for the susceptibility of AML blasts to chemotherapy. Recent clinical studies even suggest that antiangiogenic therapy can induce disease control in patients with AML relapse. In this context we have investigated the profile of the systemic component of angiogenic regulation in AML by characterizing the serum levels of (i) the angiogenic regulators angiogenin, basic fibroblast growth factor (bFGF) and endostatin; (ii) the endothelial cell marker soluble (s) E-selectin. Patients with untreated AML had increased levels of angiogenin, endostatin and sE-selectin, whereas the levels of bFGF were not significantly altered. The systemic levels of the proangiogenic bFGF, the antiangiogenic endostatin and the endothelial cell marker sE-selectin showed significant correlations, whereas angiogenin and sE-selectin levels were not correlated. Furthermore, intensive chemotherapy resulted in decreased systemic levels of the 2 proangiogenic mediators angiogenin and bFGF, whereas endostatin levels remained high after treatment. Although angiogenin normally is a part of the acute phase reaction, its systemic levels were not altered when patients with chemotherapy-induced cytopenia developed complicating bacterial infections. Our results suggest that intensive chemotherapy can modulate the systemic component of angiogenic regulation in AML patients.

L and E selectins in acute myeloid leukemia: expression, clinical relevance and relation to patient outcome

The aim of this study was to assess circulating soluble L (sL) and soluble E (sE) selectins adhesion molecules in acute myeloid leukemia (AML) blasts in order to evaluate their clinical significance. Fifty patients with AML (4 M0, 8 M1, 16 M2, 5 M3, 7 M4, 6 M5, 4 M6) were included in this study. sL and sE selectins were evaluated at diagnosis, remission and in relapsed patients; whole membrane expression of L and E selectins by AML blast was investigated only at diagnosis. In addition, 15 normal persons were studied as a control group. sL and sE selectins were significantly higher in AML patients at diagnosis when compared to controls (P<0.01), but less at remission (P<0.01). Furthermore, elevated sL and sE selectin levels were detected in patients with AML at relapse. sE and sL selectins were significantly higher in AML patients with extramedullary infiltration as compared to patients without extramedullary disease (P<0.001). Membrane expression of L selectin was positive in 20% of AML patients. However, none of the patients showed significant E selectin expression. Patients with higher sE and sL selectins at diagnosis have high probability of relapse compared to those with normal levels (P<0.01 and <0.001, respectively). The overall relapse predictability of sE and sL selectins was 84%. Moreover, patients with higher sE and sL selectins levels had shorter event free survival than patients with lower levels (P<0.001 for both). The overall mortality prediction using sE, sL, and cellular L selectin was 96%.

IN CONCLUSION

(1) AML blast cell express and release sL selectins but not sE selectin, (2) sE and sL selectins and cellular L selectin may be useful prognostic markers in evaluating AML patients at diagnosis.

Expression of co-stimulatory and adhesion molecules and chemokine or apoptosis receptors on acute myeloid leukaemia: high CD40 and CD11a expression correlates with poor prognosis

The expression of adhesion and co-stimulatory molecules, and chemokine and death receptors such as tumour necrosis factor (TNF) and FAS on acute myeloid leukaemia (AML) may influence the biology of the disease and response to chemotherapy and immunotherapy. In this study, we analysed the expression of these molecules in 99 AML patients using monoclonal antibodies and flow cytometry, and correlated the expression with French-American-British (FAB) classification and survival. The following molecules were studied: the co-stimulatory molecules CD80, CD86 and CD40; the adhesion molecules CD11a-c, CD31, CD43, CD50, CD54, CD102, CD58 and CD62L; the chemokine receptor CXCR4; and the death receptors TNFR1 and TNFR2 and FAS. The expression of all molecules was significantly higher in the M4/M5 FAB subgroups except for CD80, CD43, CD54 and CD62L. The AML M3 subgroup had a significant lower expression of CD11a (P = 0.02) and CD11c (P = 0.03). Five-year survival was significantly shorter in cases of high CD40 expression [> 20% positive cells, relative risk (RR) 2.56, P = 0.02] or high CD11a expression (> 80% positive cells, RR 2.6, P = 0.03). This effect was most prominently present in the AML M4/M5 FAB subgroups. We conclude that the expression levels of adhesion and co-stimulatory molecules, CXCR4 and apoptosis-receptors are predominantly FAB subtype-related with high CD40 and CD11a expression as poor prognostic factors.

Stromal-mediated down-regulation of CD13 in bone marrow cells originating from acute myeloid leukemia patients

The metallopeptidase CD13 is expressed on normal myeloid cells of monocytic and granulocytic origin and on the surface of leukemic blasts in most acute myeloid leukemias (AML). To study the mechanisms regulating lineage restricted CD13 expression in AML we determined normalised CD13 mRNA levels in bone marrow cells and peripheral blood cells of 27 AML patients. Cells of bone marrow origin had lower levels of normalised CD13 mRNA than cells of peripheral blood origin, even though fluorescence intensity and fraction of cells expressing CD13 on the surface was unchanged. In particular, AML patients with very low levels of normalised CD13 mRNA in bone marrow cells showed an increase in CD13 mRNA expression in peripheral blood. To evaluate the effects of bone marrow microenvironment on CD13 mRNA expression, we cultured leukemic myeloid cells with and without murine stromal cells. Bone marrow cells with high and low CD13 surface expression that entered the stromal layers all down-regulated CD13 mRNA expression as compared to cells in suspension above. For peripheral blood cells within stromal layers, CD13 mRNA expression was diminished in only 3 out of 6 cases. The ambiguous effect of stromal cells on peripheral blood cells may illustrate a differentiation-dependent response towards stroma. We determined the polyadenylation status of CD13 mRNA for 9 bone marrow aspirates and 7 peripheral blood samples. Polyadenylation was diminished in bone marrow cells from AML patients with low levels of normalised CD13 mRNA, raising the possibility of involvement of mRNA instability in regulation of CD13 mRNA expression in this subgroup of patients.

Intercellular adhesion molecule-1 in extravasation of normal mononuclear and leukaemia cells

Interaction of intercellular adhesion molecules (ICAMs) with their receptors has a key role in normal leucocyte adhesion and migration, whereas in leukaemia this has not been well established. In this study, we have evaluated the roles of different adhesion molecules in normal and leukaemia cell extravasation in a novel organotypic model for vessel wall and measured plasma ICAM-1 and -2 levels in acute leukaemia patients at diagnosis and during chemotherapy. We found that both normal mononuclear cells and blast cells from acute leukaemia patients, as well as retinoic acid-treated promyelocytic leukaemia cells, rapidly extravasated through endothelial cell layers into the underlying collagen matrix. ICAM-1 antibody prevented the extravasation, while antibodies to other adhesion molecules showed little (CD18, ICAM-2) or no inhibition (CD11a and ICAM-3). Soluble ICAM-1 (sICAM-1) protein had no effect. We also observed increased plasma sICAM-1 and -2 levels in leukaemia patients and found that they correlated only weakly with the white blood cell count. No correlation was found between sICAM-1 or -2 levels and the response to therapy. Although elevated sICAM-2 levels decreased rapidly during chemotherapy, sICAM-1 levels did not. Because sICAM-1 protein had no effect on leukaemia cell extravasation in vitro, it is probable that the increased plasma sICAM-1 levels in leukaemia patients may not play a role in leukaemia cell infiltration. However, as we showed that ICAM-1 mediated leukaemia cell extravasation on the cell surface, it is possible that cellular ICAM-1 has an important role in disease progression.

Increased soluble P-selectin in patients with haematological and breast cancer: a comparison with fibrinogen, plasminogen activator inhibitor and von Willebrand factor

Abnormal platelet activation and an increased risk of thrombosis are frequent findings in cancer. As soluble adhesion molecule P-selectin is being increasingly recognized as reflecting increased platelet activation, we hypothesized raised levels in patients with cancer, obtaining plasma from 24 patients with a cross-section of haematological cancers, 41 with breast cancer, and from an equal number of healthy controls for each patient group. Levels of soluble P-selectin were compared with those of von Willebrand factor (vWf), plasminogen activator inhibitor-1 (PAI-1) activity and fibrinogen (markers of endothelial integrity, fibrinolysis and coagulation, respectively). We found raised soluble P-selectin, fibrinogen and vWf in both patient groups compared with their controls (P < 0.01). vWf and soluble P-selectin were higher in the haematological cancers than in breast cancer patients (by 30 and 74%, respectively; both P < 0.01). There was no significant difference in levels of PAI-1 between any group. There were no differences in soluble P-selectin or vWf when the data from the women with breast cancer were classified according to tumour size, lymph node involvement or presence of vascular invasion. We conclude that the platelet marker soluble P-selectin is raised in both haematological and breast cancer, and is higher in the former, but is unrelated to the type or stage of breast cancer.

Cytokine responsiveness of mitogen-activated T cells derived from acute leukemia patients with chemotherapy-induced leukopenia

The aim of the study was to characterize effects of exogenous cytokines on T lymphocytes derived from acute leukemia patients with chemotherapy-induced leukopenia. We investigated the cytokine responsiveness of long-term expanded CD4+ and CD8+ T cell clones and the effects of exogenous cytokines on anti-CD3-stimulated polyclonal T cell responses. After mitogenic activation in the presence of acute myelogenous leukemia (AML) blasts, most CD4+ and CD8+ clones proliferated in response to interleukin-2 (IL-2). Although a majority of the IL-2-responsive clones could also proliferate in the presence of exogenous IL-4, IL-7, IL-9, IL-10, IL-12, and IL-15, only IL-15 responses were equal to or exceeded the corresponding IL-2 responses. Exogenous cytokines were also added during T cell activation with phytohemagglutinin (PHA) + accessory leukemia cells derived from different AML patients, and all the cytokines then had divergent effects that depended on both differences between clones and differences between AML patients. However, for most of these T cell clone/AML blast combinations, IL-2 and IL-15 caused enhanced T cell proliferation. IL-2 and IL-15 also enhanced anti-CD3-stimulated polyclonal responses of nonexpanded T cells derived from cytopenic patients, whereas other cytokines had only minor effects. Our results demonstrate that cytokine-responsive T cells remain in the circulation during chemotherapy-induced cytopenia, and combination therapy including intensive chemotherapy and T cell-targeting cytokine therapy should, therefore, be possible in AML.