Serum Chemokine-release Profiles in AML-patients Might Contribute to Predict the Clinical Course of the Disease

In cancer or hematologic disorders, chemokines act as growth- or survival factors, regulating hematopoiesis and angiogenesis, determining metastatic spread and controlling leukocyte infiltration into tumors to inhibit antitumor immune responses. The aim was to quantify the release of CXCL8, -9, -10, CCL2, -5, and IL-12 in AML/MDS-pts' serum by cytometric bead array and to correlate data with clinical subtypes and courses. Minimal differences in serum-levels subdivided into various groups (e.g. age groups, FAB-types, blast-proportions, cytogenetic-risk-groups) were seen, but higher release of CXCL8, -9, -10 and lower release of CCL2 and -5 tendentially correlated with more favorable subtypes (<50 years of age, <80% blasts in PB). Comparing different stages of the disease higher CCL5-release in persisting disease and a significantly higher CCL2-release at relapse were found compared to first diagnosis - pointing to a change of 'disease activity' on a chemokine level. Correlations with later on achieved response to immunotherapy and occurrence of GVHD were seen: Higher values of CXCL8, -9, -10 and CCL2 and lower CCL5-values correlated with achieved response to immunotherapy. Predictive cut-off-values were evaluated separating the groups in 'responders' and 'non-responders'. Higher levels of CCL2 and -5 but lower levels of CXCL8, -9, -10 correlated with occurrence of GVHD. We conclude, that in AML-pts' serum higher values of CXCL8, -9, -10 and lower values of CCL5 and in part of CCL2 correlate with more favorable subtypes and improved antitumor'-reactive function. This knowledge can contribute to develop immune-modifying strategies that promote antileukemic adaptive immune responses.

In vitro-induced response patterns of antileukemic T cells: characterization by spectratyping and immunophenotyping

Myeloid leukemic cells can be induced to differentiate into leukemia-derived dendritic cells (DCleu) regaining the stimulatory capacity of professional DCs while presenting the leukemic antigen repertoire. But so far, the induced antileukemic T-cell responses are variable both in specificity and in efficacy. In an attempt to elucidate the underlying causes of different T-cell response patterns, T-cell receptor (TR) Vβ chain rearrangements were correlated with the T cells corresponding immunophenotypic profile, as well as their proliferative response and cytolytic capacities. In three different settings, donor T cells, either human leukocyte antigen matched or mismatched (haploidentical), or autologous T cells were repeatedly stimulated with myeloid blasts or leukemia-derived DC/DCleus from the corresponding patients diseased from acute myeloid leukemia (AML). Although no significant differences in T-cell proliferation were observed, the T-cell-mediated cytolytic response pattern varied considerably and even caused blast proliferation in two cases. Spectratyping revealed a remarkable restriction (>75% of normal level) of the CD4+ or CD8+-TR repertoire of blast- or DC/DCleu-stimulated T cells. Although in absolute terms, DC/DCleu stimulation induced the highest grade of restriction in the CD8+ T-cell subset, the CD4+ T-cell compartment seemed to be relatively more affected. But most importantly, in vitro stimulation with DC/DCleu resulted into an identical TR restriction pattern (β chain) that could be identified in vivo in a patient sample 3 months after allo-SCT. Thus, in vitro tests combining functional flow cytometry with spectratyping might provide predictive information about T cellular response patterns in vivo.

Various ‘dendritic cell antigens’ are already expressed on uncultured blasts in acute myeloid leukemia and myelodysplastic syndromes

Aim and methods: Leukemia-derived dendritic cells (DCleu) potentially present the whole leukemic antigen repertoire. We studied antigen-expression profiles of blasts/dendritic cells (DCs) generated from 137 acute myeloid leukemia (AML)/49 myelodysplastic syndromes (MDS) patients with six different DC-generating media by flow-cytometry combining expression of blast/maturation and DC antigens (DCA:CD1a,b,c, CD25, CD40, CD80, CD83, CD86, CD137-L and CD206). Results: First, DCA are regularly and variably expressed on uncultured blasts/mononuclear cells (MNCs). Individual patients’ DCA profiles must be evaluated before DC-culture to find suitable DCA to estimate quality/quantity of DC after culture. Second, after culture in every patient, at least one marker fulfilled these criteria. Third, different DC-generating methods showed varying efficiency to generate DC: not every method was always successful. Fourth, individual FACS-DCA profiles showed a successful DC/DCleu generation with at least one of three previously tested methods in every given AML/MDS case. Fifth, pooling results of all selected best methods in every given case, 28/30% DC were generated from AML/MDS samples: >60% viable DC, on average 49/56% mature DC and on average 36% of blasts were convertible to DCleu resulting in on average 49% DCleu of AML-DC. Conclusions: Individual DCA-expression profiles should be evaluated before culture to evaluate DC counts/subtypes (mature/viableDC, DCleu) in individual patients.

Quality of T-cells after stimulation with leukemia-derived dendritic cells (DC) from patients with acute myeloid leukemia (AML) or myeloid dysplastic syndrome (MDS) is predictive for their leukemia cytotoxic potential

Myeloid leukemic cells can differentiate into leukemia-derived dendritic cells (DC(leu)), presenting known/unknown leukemic-antigens. Induced anti-leukemic T-cell-responses are variable. To further elicit DC/DC(leu)-induced T-cell-response-patterns we performed (functional)flow-cytometry/fluorolysis-assays before/after mixed lymphocyte cultures (MLC) of matched (allogeneic) donor-T-cells (n=6), T-cells prepared at relapse after stem cell transplantation (n=4) or (autologous) patients'-T-cells (n=7) with blast-containing-mononuclear-cells ('MNC') or DC(leu)-containing DC ('DC'). Compared to 'MNC' 'DC' were better mediators of anti-leukaemic T-cell-activity, although not in every case effective. We could define cut-off proportions of mature DC, DC(leu), proliferating, CD4(+), CD8(+) and non-naive T-cells after 'MNC'- or 'DC'-stimulation, that were predictive for an anti-leukemic-activity of stimulated T-cells as well as a response to immunotherapy. Interestingly especially ratios >1 of CD4:CD8 or CD45RO:CD45RA T-cells were predictive for anti-leukemic function after DC-stimulation. In summary the composition and quality of DC and T-cells after a MLC-stimulating-phase is predictive for a successful ex-vivo and in-vivo anti-leukemic response, especially with respect to proportions of proliferating, CD4(+) and CD45RO(+) T-cells. Successful cytotoxicity and the development of a T-cell-memory after 'DC'-stimulation could be predictive for the clinical course of the disease and may pave the way to develop adoptive immunotherapy, especially for patients at relapse after SCT.

The role of soluble and cell-surface expressed 4-1BB ligand in patients with malignant hemopoietic disorders

The TNFR family member 4-1BB and its ligand 4-1BBL are involved in the costimulation of T-cells and tumor-derived soluble (s)4-1BBL may influence the interaction of malignant cells with the immune system. Here, we report that cell-surface-expressed (c)4-1BBL can be expressed on mononuclear blood cells from patients with acute myeloid leukemia (AML) (n = 35), myelodysplasia (n = 5) or non-Hodgkin lymphoma (n = 11) and can be coexpressed on varying proportions of lymphoid or myeloid malignant cells and on dendritic cells differentiated from AML-blasts. Direct correlations between c- and s4-1BBL were not found in the investigated cases. Up to now expression of 4-1BBL has not been described on primary myeloid malignant cells, but only on malignant cells of lymphoid or solid tumor origin or on tumor cell lines. With our work we further contribute to the understanding of the potential role of c/s4-1BBL in immune reactions and its influence on the interaction of tumor and immunoreactive cells.

Improved effector function of leukemia-specific T-lymphocyte clones trained with AML-derived dendritic cells

Recently it was shown that myeloid leukemic cells can be induced to differentiate into leukemia-derived dendritic cells (DCleu), regaining the stimulatory capacity of professional DCs while presenting the leukemic antigen repertoire. But so far, the induced antileukemic T-cell responses have varied in specificity and efficacy, or have even mediated opposite effects. In an attempt to further characterize the DC/DCleu induced T-cell response pattern, immunoscope spectratyping, a novel and powerful tool to detect T-cell receptor (TCR) rearrangements was used in combination with functional flow cytometry and non-radioactive fluorolysis assays. Human leucocyte antigen (HLA) matched donor T-cells were repeatedly stimulated, either with leukemic blasts (French-American-British, FAB M4eo) or the corresponding blast-derived DCs. Functional comparison revealed no significant difference in their T-cell stimulatory capacity, while the DC/DCleu fraction favored T-cells with a higher lytic activity, comprising a higher proportion of T-memory CD45R0+ cells. Stimulation with blasts and DC/DCleu induced a similar TCR restriction pattern, while stimulation with DC/DCleu favored the CD4 T-cell subset and seemed to cause a higher grade of restriction. In conclusion, a combined strategy using spectratyping with functional tests might not only provide useful information about the specificity and efficacy of the induced T-cell response, but also pave the way to gain effective T-cell clones for therapeutic use.