A Step towards Reconstitution or Maintenance of Remission before or after Stem Cell Transplantation in AML/MDS by Ex Vivo Generation of Leukaemia-Derived DC (DCleu) and DC-Activated T-Cells: Role of the Quality and Quantity of DC/DCleu and Anti-Leukemia-Directed T-Cells To Predict the Course and Success of Immunotherapy.

Abstract The presentation of leukemic antigens can be improved in AML and MDS by in vitro conversion of leukemic cells in leukemia-derived DC (DCleu), thereby forming a platform for the generation of leukemia-specific cytotoxic lymphocytes (CTL). In preliminary analyses with 140 AML and 60 MDS-cases we could already define optimal serum-free culture conditions to generate DC/DCleu.(Kufner 2005 I–III). Now we want to predict or correlate the clinical response to a DC/CTL-based immunotherapy by detailed analyses of the ex vivo generated/activated DC/DCleu and T-cells: 1)By a combination of 3 different DC-generating methods (‘MCM-mimic’, Lee 2003; ‘Ca-Ionophore’, Houtenbos 2003; ‘Picibanil’, Sato 2003) we can generate DC/DCleu in every case of AML/MDS, independently from FAB-type or karyotype. DC/DCleu are quantified according to their surface DC/blast-marker profiles. On average 42–45%/39–66% DC in AML/MDS could be generated with 48–54%/39–51% mature (CD83+) and 31–34%/23–31% migratory (CCR7+) DC. 45–65% of DC were ‘DCleu’; on average 47% of blasts are convertible to DCleu.. 2) In AML-patients who had presented with a relapse after SCT we could correlate a better ex vivo convertibility of blasts to DCleu with the patients’ in vivo response to a GM-CSF/Donor-lymphocyte Infusion (DLI)-therapy of their relapse after SCT (33% vs 7% to DCleu convertible blasts in ‘non-responders’). 3) A ‘Mixed lymphocyte culture’ (MLC) of autologous AML-patients’ or allogeneic donor-T-cells showed an on average higher proliferation and stimulation of DC-primed compared to MNC-primed T-cells: Upregulation of CD80/CD86-CD28;CD40-CD154;CD137L-CD137; moreover DC-priming yielded higher proportions of CD4+ cells, CD3+CD45RO+ memory cells CCR4+ T-cells (+59%, +52%, +91%) compared to MNC-primed T-cells (+35%, +13%, +44%) and a higher leukaemia-cytolytic activity (average 62%) compared to MNC-stimulated CTL (average 26%). 4) A detailed analysis of data showed great individual variations depending on the quality and composition of DC and T-cells: a) non-DC-primed autologous or allogeneic T-cells an lead to an increase of naive blasts after 3h incubation with blasts b) in cases with an ineffective DC-mediated ex vivo lysis of naïve blasts lower proportions of mature DC (29% vs 63%), DCleu (41% vs 68%) or a reduced T-cell proliferation or even loss of CD4/CD8/memory T-cells were seen. In summary our data show 1. that DC/DCleu can be generated in every single AML/MDS-case. 2. Grade of ex-vivo generability of DC/DCleu correlates with the in vivo response to a GM-CSF/DLI-relapse therapy. 3. Composition and quality of DC and autologous or donor T-cells after DC-priming provides informations about the activability and quality of CTLs in individual patients. We conclude, that ex vivo analysis of the DC/anti-leukemic T-cell-activability is necessary to develop and select promising anti-leukemia-directed T-cells for the immunotherapy of AML and MDS.

Topic: CAR-T cell therapy research
Subfield: Oncology
Field: Medicine
Domain: Health Sciences