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Final Report Summary - STEMTARGET (Targeting Leukemia Stem Cells)

Successful establishment as an independent researcher at Lund University.

As a Marie Curie career integration grant (CIG) holder, I have established myself as an independent researcher at Lund University, Sweden. My research group currently consists of two postdoc, three graduate students and one research engineer. All equipment, including advanced cell sorters, a platform allowing for in vivo shRNA and CRISPR/Cas9-based screens has been established, and several mouse experimental models have been generated. Moreover, within my group, we have made multiple scientific discoveries published in international journals. In addition, I have received the highly competitive Senior investigator award (2018) by the Swedish Cancer Society.

My research is focused on the disorder acute myeloid leukemia (AML), which is a fatal disease. Current therapies are ineffective at defeating the disease and associated with severe side effects. Hence, there is a strong medical need for new types of therapeutic approaches targeting this disorder. More specifically, my research is based on the hypothesis that for maximum effect, novel treatments for AML should target all leukemia cells with the ability to self-renew and maintain the disease indefinitely, a population termed leukemia stem cells (LSCs). Critical to developing new therapies targeting LSCs is identifying new therapeutic targets for novel treatment approaches.


RNAi-screening identified several cell surface receptors critical for leukemia stem cells
We have performed several shRNA screens designed to generate a prioritized list of cell surface proteins that are highly expressed in primitive acute myeloid leukemia (AML) cells and that are essential for the survival of leukemia-initiating cells in mice, also termed leukemia stem cells (LSCs). From the screen, we selected two cell surface proteins that scored highly, CD97 and Tlr1. In validation experiments, the findings from the screens could be recapitulated demonstrating strong depletion of leukemia cells with multiple shRNAs targeting CD97 or Tlr1. Whereas both CD97 and TLR1 were expressed on AML stem and progenitor cells, TLR1 was not expressed on normal hematopoietic stem cells. We further studied the mechanistic basis for the selective importance of TLR1-signaling for maintenance of LSCs and linked it to NfkB-signaling. Overall, these studies demonstrate that TLR1 and CD97 are critical for LSCs and highlight these molecules as potential therapeutic targets. The TLR1 project entititled “Agonistic targeting of TLR1/TLR2 induces p38 MAPK-dependent apoptosis and NFκB-dependent differentiation of AML cells” was recently published open access (Eriksson et al, Blood Advances, 2017, Oct:1(23):2046-2057), and a manuscript summarizing the CD97 project is in preparation.

Cytokine screening identifies IL-4 as a negative regulator of leukemia stem cells
To identify cytokines selectively regulating LSCs, we developed an in-house cytokine screen using primitive leukemia and normal bone marrow cells. IL-4 emerged as the top hit causing the strongest depletion of leukemia cells. Validation experiments confirmed that IL-4 stimulation dramatically reduced the number of leukemia-initiating cells, whereas IL-4 stimulation of normal hematopoietic stem cells resulted in increased numbers of long-term bone marrow repopulating cells. In proof of concept experiments, IL-4 treatment of leukemic mice resulted in reduced leukemia burden and increased survival, demonstrating that IL-4 treatment shows therapeutic efficacy also in an in vivo treatment setting. In addition, we performed CRISPR-mediated silencing of Stat6 and demonstrated that IL-4 kill the leukemia cells through apoptosis in a Stat6-dependent manner. Finally, we found that a subfraction of primary AML patient samples go into apoptosis when exposed to IL-4 treatment, suggesting that our findings have relevance for human disease. In aggregate, these findings demonstrate that IL-4 negatively regulates AML stem cells in a Stat6-dependent manner. This project was selected for presentation at the American Society of Hematology meeting in San Fransisco, 2014, and was recently published open access: “Interleukin 4 has Stat6-dependent therapeutic efficacy in acute myeloid leukemia” Leukemia, 2018 Mar;32(3):588-596.

Summary
During the grant period, we have completed two major studies described above. Based on this work, I have as senior author published two open access articles with acknowledgement of grant support from FP7 Marie Curie. These findings might be translated into new therapeutic opportunities in AML, a disease with dismal outcome.

Reported by

LUNDS UNIVERSITET
Sweden

Subjects

Life Sciences
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