Maya André

University of Tuebingen, Tübingen, Baden-Württemberg, Germany

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Publications (3)9.45 Total impact

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    ABSTRACT: Cytotoxic T cells are important effectors for robust antitumor immune responses. However, tumor-infiltrating CD8 T cells are often functionally impaired. Insufficient antitumor activity of CD8 T cells can be due to a lack of costimulatory signals. NKG2D is such a costimulatory receptor on CD8 T cells that facilitates immunorecognition of stressed and malignant cells, promotes tumor rejection by NK and CD8 T cells and contributes to immunosurveillance of spontaneous malignancies. Previous reports suggested an involvement of NKG2D in establishing CD8 T cell-mediated antitumor memory. However, the significance of NKG2D for the generation and effector phase of memory CD8 T cell responses is largely unknown. To address these issues, we made use of a transgenic mouse model (H2-K(b)-MICA mice) where the human NKG2D ligand MICA is ubiquitously and constitutively expressed resulting in a severe dysfunction of NKG2D. Both, ovalbumin (OVA)-specific (H2-K(b)/OVA(257-264)) memory CD8 T cells arisen from the endogenous T cell pool and adoptively transferred OVA-specific OT-I memory cells were unable to control growth of an OVA-expressing lymphoma in H2-K(b)-MICA mice. While expansion of memory T cells in these mice on antigen challenge was not different from controls, CD8 memory T cells of H2-K(b)-MICA mice did not effectively eliminate tumor cells in vivo. Altogether, our data suggest that NKG2D has no major role in the generation and expansion of memory CD8 T cells, but rather substantially enhances the cytolytic effector responses of reactivated memory T cells and thereby contributes to an efficacious tumor rejection.
    International Journal of Cancer 05/2011; 131(7):1601-10. · 6.20 Impact Factor
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    ABSTRACT: In acute myeloid leukemia (AML), the leukemia-initiating cell is found within the CD34(+)/CD38(-) cell compartment. Over the last years evidence grew that AML is initiated and propagated by leukemic stem cells (LSCs). Conceivably, these most immature leukemia cells are more resistant to therapy and subsequently initiate relapse. The authors studied 17 patients with childhood AML treated according to the AML-BFM 98/04 protocol. At diagnosis, the authors determined the characteristic immunophenotype of the leukemic cells by flow cytometry and investigated the expression of CD34, CD38, and CD45 to define a population of immunophenotypically immature cells (CD34(+)/CD38(-)/CD45(-/low)) enriched for LSCs in many cases of AML. The authors compared the fraction of this population of all myeloid cells at diagnosis with event-free survival. Kaplan-Meier analysis revealed significant higher event free survival of patients with low CD34(+)/CD38(-)/CD45(-/low) cell proportion (<0.68%) compared to patients with high burden of this population (>0.83%; log-rank P < .04). This correlation was not found for the total number of CD34(+) cells. This is the first study to show that a higher proportion of immature CD34(+)/CD38(-)/CD45(-/low) blasts at diagnosis correlates with unfavorable prognosis in childhood AML. The results suggest that a large CD34(+)/CD38(-)/CD45(-/low) population reflects a higher fraction of LSCs, leading to increased chemotherapy resistance and elevated relapse rate. Thus the initial frequency of CD34(+)/CD38(-)/CD45(-/low) cells may serve as a prognostic marker in pediatric AML. Future treatment in childhood AML should specifically target this immature population as well as the mature blast population.
    Pediatric Hematology and Oncology 03/2011; 28(2):91-9. · 0.90 Impact Factor
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    ABSTRACT: Prognosis for children with acute lymphoblastic leukemia (ALL) has considerably improved, yet relapse still occurs in a significant proportion of patients. Conceivably, the most immature leukemia cells may be more resistant to therapy and initiate relapse. We studied 42 patients with childhood ALL treated according to the ALL-BFM 2000 protocol. At diagnosis, we determined the characteristic immunophenotype of the leukemic cells by flow cytometry and also investigated the expression of CD34 and CD38 to define a population of immunophenotypically immature cells (CD34(+)/CD38(-)). We then studied levels of minimal residual disease (MRD) after induction therapy (day 33) and after consolidation therapy (week 12). We found a significant, increasing correlation between the prevalence of CD34(+)/CD38(-) cells at diagnosis and MRD levels at day 33 and week 12. Our results suggest that the initial frequency of CD34(+)/CD38(-) cells may serve as a prognostic marker in pediatric ALL.
    Leukemia research 04/2010; 34(9):1139-42. · 2.36 Impact Factor