Astrid Marta Olsnes

Antiangiogenic therapy in acute myelogenous leukemia: targeting of vascular endothelial growth factor and interleukin 8 as possible antileukemic strategies.

Acute myelogenous leukemia (AML) is an aggressive disorder with an overall disease-free survival of 40-50% even for the younger patients under 60 years of age who can receive the most intensive treatment. The median age at the time of diagnosis is 60-65 years, and the large majority of elderly patients usually receive less intensive chemotherapy or only supportive therapy due to the high treatment-related mortality when using intensive therapy for elderly individuals. Thus, there is a need for new therapeutic approaches to improve the treatment in younger patients and to make AML-directed therapy with acceptable toxicity possible in elderly individuals. Angiogenesis seems to be important both for leukemogenesis and susceptibility to intensive chemotherapy, and antiangiogenic strategies are therefore considered for the treatment of AML. The two proangiogenic mediators vascular endothelial growth factor (VEGF) and interleukin 8, (IL-8, also referred to as CXCL8) seem to be important in human AML: VEGF is released at increased levels due to interactions between AML cells and neighboring nonleukemic cells, whereas IL-8 is released at high levels by native human AML cells. Thus, VEGF as a therapeutic target in AML is suggested both by experimental and clinical observations, whereas IL-8 as a target is mainly suggested by experimental evidence. In the present review we describe and discuss (i) the angioregulatory network of soluble mediators in AML, including both the systemic levels and local release by native human AML cells; and (ii) various therapeutic approaches to target VEGF and IL-8. Although single angioregulatory mediators can be targeted, it should be emphasized that the final effect of soluble mediators on angioregulation is determined by a complex angioregulatory network that varies between AML patients, and the final effect of targeting single mediators may therefore differ between patient subsets.

T lymphocyte chemotactic chemokines in acute myelogenous leukemia (AML): local release by native human AML blasts and systemic levels of CXCL10 (IP-10), CCL5 (RANTES) and CCL17 (TARC)

T cell targeting immunotherapy is now considered in acute myelogenous leukemia (AML), and local recruitment of antileukemic T cells to the AML microcompartment will then be essential. This process is probably influenced by both intravascular as well as extravascular levels of T cell chemotactic chemokines. We observed that native human AML cells usually showed constitutive secretion of the chemotactic chemokines CXCL10 and CCL5, whereas CCL17 was only released for a subset of patients and at relatively low levels. Coculture of AML cells with nonleukemic stromal cells (i.e., fibroblasts, osteoblasts) increased CXCL10 and CCL17 levels whereas CCL5 levels were not altered. However, a wide variation between patients in both CXCL10 and CCL5 levels persisted even in the presence of the stromal cells. Neutralization of CXCL10 and CCL5 inhibited T cell migration in the presence of native human AML cells. Furthermore, serum CCL17 and CXCL10 levels varied between AML patients and were determined by disease status (both chemokines) as well as patient age, chemotherapy and complicating infections (only CCL17). Thus, extravascular as well as intravascular levels of T cell chemotactic chemokines show a considerable variation between patients that may be important for T cell recruitment and the effects of antileukemic T cell reactivity in local AML compartments.

Cyclin B1 is commonly expressed in the cytoplasm of primary human acute myelogenous leukemia cells and serves as a leukemia-associated antigen associated with autoantibody response in a subset of patients

Objectives:  Aberrant expression of cyclin B1, a cell cycle regulator, is related to prognosis in various human malignancies. Additionally, cytoplasmic expression of cyclin B1 in epithelial malignancies is associated with a specific T‐cell response and presumably also a humoral immune response. We therefore investigated (i) whether a similar expression pattern could be detected in native human acute myelogenous leukemia (AML) cells and (ii) whether cyclin B1 specific antibodies could be detected in AML.

The protein kinase C agonist PEP005 increases NF-κB expression, induces differentiation and increases constitutive chemokine release by primary acute myeloid leukaemia cells

Acute myeloid leukaemia (AML) cells show constitutive release of several chemokines that occurs in three major clusters: (I) chemokine (C‐C motif) ligand (CCL)2–4/chemokine (C‐X‐C motif) ligand (CXCL)1/8, (II) CCL5/CXCL9–11 and (III) CCL13/17/22/24/CXCL5. Ingenol‐3‐angelate (PEP005) is an activator of protein kinase C and has antileukaemic and immunostimulatory effects in AML. We investigated primary AML cells derived from 35 unselected patients and determined that PEP005 caused a dose‐dependent increase in the release of chemokines from clusters I and II, including several T cell chemotactic chemokines. The release of granulocyte‐macrophage colony‐stimulating factor and hepatocyte growth factor was also increased. CCL2–4/CXCL1/8 release correlated with nuclear factor (NF)‐κB expression in untreated AML cells, and PEP005‐induced chemokine production was associated with further increases in the expression of the NF‐κB subunits p50, p52 and p65. Increased DNA binding of NF‐κB was observed during exposure to PEP005, and the specific NF‐κB inhibitor BMS‐345541 reduced constitutive chemokine release even in the presence of PEP005. Finally, PEP005 decreased expression of stem cell markers (CD117, CXCR4) and increased lineage‐associated CD11b and CD14 expression. To conclude, PEP005 has a unique functional pharmacological profile in human AML. Previous studies have described proapoptotic and T cell stimulatory effects and the present study describes additional T cell chemotactic and differentiation‐inducing effects.

Anticancer Immunotherapy in Combination with Proapoptotic Therapy

Induction of immune responses against cancer-associated antigens is possible, but the optimal use of this strategy remains to be established and especially the combination of T cell therapy and the use of new targeted therapeutic agents should be investigated. The design of future clinical studies then has to consider several issues. Firstly, induction of anticancer T cell reactivity seems most effective in patients with low disease burden. Initial disease-reducing therapy including surgery, irradiation and conventional or new targeted chemotherapy should therefore be used, preferably through induction of immunogenic cancer cell death. Secondly, after the induction phase effector T cells will induce cancer cell apoptosis mainly through the intrinsic apoptosis-regulating pathway. The effect of this anticancer immune reactivity should be strengthened by the administration of chemotherapy that mediates additional proapoptotic signalling through the external apoptosis-initiating pathway, blocking of anti-apoptotic signalling or inhibition of survival signalling. Thirdly, conventional chemotherapy and new targeted therapy have direct immunosuppressive effects on the T cell system, but even patients with severe chemotherapy-induced lymphopenia have an operative T cell system and immunotherapy may therefore be initiated immediately or early after disease-reducing therapy when the cancer cell burden is expected to be lowest. Finally, chemotherapy toxicity on human T cells is not a random process, and one should especially focus on the possibility to strengthen anticancer immune reactivity through chemotherapy-induced elimination or inhibition of immunosuppressive regulatory T cells. All these issues need to be considered in the design of future clinical studies combining chemotherapy and immunotherapy.

In Vitro Induction of a Dendritic Cell Phenotype in Primary Human Acute Myelogenous Leukemia (AML) Blasts Alters the Chemokine Release Profile and Increases the Levels of T Cell Chemotactic CCL17 and CCL22

Immunotherapy is now considered in acute myelogenous leukemia (AML). A dendritic cell (DC) phenotype can be induced in primary human AML cells by in vitro culture in the presence of various cytokine combinations. The aim was to investigate whether this phenotypic alteration is associated with altered chemokine release. AML cells were cultured according to four protocols that have been characterized in detail for AML-DC induction: (1) granulocyte-macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) days 1-14 and tumor necrosis factor-alpha (TNF-alpha) for days 6-14, (2) GM-CSF + IL-4 + TNF-alpha + FMS-like tyrosine kinase 3-ligand (Fl3-L) for 8 days, (3) GM-CSF + IL-4 + TNF-alpha + Flt3-L + stem cell factor (SCF) + transforming growth factor-beta1 (TGF-beta1) for 8 days, and (4) 25 Gy gamma-irradiation combined with culture in the presence of GM-CSF + SCF + IL-3 for 4 days. Significantly increased AML-DC release of CCL17 and CCL22 was observed for protocols 1, 2, and 3, whereas effects on CCL2-5, CXCL8, and CXCL10 differed in all protocols. Neutralization studies using a transwell migration assay demonstrated the increased level of CCL17 and CCL22 release was important for AML-DC chemotaxis of normal T cells. Induction of a dendritic AML cell phenotype is associated with an altered chemokine release profile. Detailed characterization of chemokine release should be included in future studies of AML-DC vaccination.

Circulating T cells derived from acute leukemia patients with severe therapy-induced cytopenia express a wide range of chemokine receptors

Abstract Normal T cells can mediate antileukemic reactivity after allogeneic stem cell transplantation and T cell targeting immunotherapy is now considered for patients receiving conventional chemotherapy. This antileukemic reactivity is most effective in patients with a low leukemia cell burden, and this burden is expected to be lowest early after transplantation/chemotherapy when patients are cytopenic. Local T cell recruitment will then be essential for the efficiency of the antileukemic response. In this context, the authors compared the chemokine receptor expression for T cells derived from healthy individuals and acute myelogenous leukemia patients with therapy-induced cytopenia after conventional chemotherapy or allogeneic stem cell transplantation. Circulating CD3+ T cells showed the same chemokine receptor expression for all three groups: CCR1low, CCR2low, CCR3low, CCR4intermediate, CCR5intermediate, CCR7low/intermediate, CXCR2low, CXCR3intermediate, and CXCR4high. Thus, only minor differences between the groups were observed when comparing individual receptors, and we therefore conclude that the chemokine receptor profiles of circulating CD3+ T cells show no qualitative and only minor quantitative differences for these three groups.

The immunological dilemma: Cellular innate and adaptive immune response versus human acute myeloid leukemia

It is generally accepted that acute myelogenous leukemia (AML) patients are immunocompromized. On the other hand, antileukemic immune reactivity is important for the improved survival of AML patients treated with alloge- neic stem cell transplantation and antileukemic immunotherapy is also considered for patients treated with conventional chemotherapy. In this article, we review the available studies of disease- and therapy- induced immune dysfunctions in AML patients, including the function of the cellular innate and adaptive immune system of AML patients (i) with newly diagnosed disease before treatment, (ii) immunological functions of AML patients with severe therapy induced cytopenia before hematopoietic reconstitution; and (iii) the immune reconstitution following the initial period of hematopoietic re- constitution after autologous and allogeneic stem cell transplantation. A more detailed knowledge about the immune sys- tems of these patients is essential for an optimal design of future clinical immunotherapy studies in AML.