- Protective leukemia-niche interactions
- Immune evasion of leukemia via macrophages
- Liquid biopsy for high-risk leukemia
- Zebrafish xenograft model
Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy and although treatment has improved over the last several decades, a substantial fraction of children still relapse, with poor outcomes. It is imperative that we develop better strategies to define high risk patients upfront and to identify novel therapies to prevent relapse. There is growing evidence that leukemic cells (LC) “reprogram” their surrounding niche cells to protect themselves from cytotoxic chemotherapy, but little is known about the molecular signaling pathways that are involved.
We hypothesize that LCs from early-relapse patients (ER-LCs) utilize the microenvironment more efficiently and via different molecular mechanisms when compared with LCs from patients who did not relapse (NR-LCs).
To study the complex microenvironment of leukemic cells, we use the zebrafish (Danio rerio) as a model organism. About 82% of disease associated genes have a counterpart in zebrafish and especially the hematopoietic system is highly conserved to humans. This makes the zebrafish an excellent model to study leukemia. In parallel to hematopoietic development in mammals, there are different hematopoietic niches throughout zebrafish development, that are highly conserved in their cellular composition. During the larval stage, the caudal hematopoietic tissue (CHT) serves as the site of hematopoiesis. This vessel bed is located in the caudal part of the fish and highly suitable for in vivo microscopy due to the transparency of zebrafish larvae.
We established xenografts of primary pediatric leukemia patient samples into zebrafish larvae. Fluorescently labeled cells are transplanted into different niche-transgenic reporter larvae and the leukemic niche is analyzed over time by multidimensional confocal microscopy. Thereby, we aim to develop a biological score representing differences in localization patterns, migration behavior and specific cell interactions, which we correlate to their underlying molecular pathways by applying next generation sequencing. With this approach, we directly translate biological observations into a microenvironmental gene signature. Ultimately the goal is to identify novel therapeutic targets in protective leukemia-niche interactions that may improve outcomes in these children.
Crosstalk between leukemic cells and niche cells can happen by cell-to-cell contact, but also via circulating vesicles, e.g. exosomes. Various nucleic acids have been identified in the exosomal lumen, including DNA, mRNAs, microRNAs (miRNAs), and other non-coding RNAs (lncRNAs). These exosomal RNAs can be taken up by neighboring or distant cells and subsequently modulate recipient cells.
Therefore, in this project, we focus our research on the leukemia-niche interaction via exosomes. We hypothesize, that the exosomal cargo from leukemic cells, e.g. microRNA, taken up by niche cells, switches their function towards a pro-tumoral microenvironment and leads to protection from chemotherapy, later resulting in relapse. Little is known what exact exosomal compounds are essential for the reprogramming of the niche, and whether highly aggressive leukemia uses this protection more efficiently.
Tumor derived exosomes are distributed in the peripheral blood and allow gathering of information about the tumor without getting more invasive than a simple venipuncture for a liquid biopsy.
The goal of this project is to establish a liquid biopsy by identifying exosomal markers for niche exploitation, to detect leukemias with a higher risk of relapse as early as at diagnosis. The identified markers will influence the risk stratification of patients and prevent relapses by an early adjustment of therapy.
To discover exosomal cargo differentially expressed in patients prone to relapse, we analyze both primary serum samples as well as patient derived xenograft (PDX) models.
For the PDX approach, we established a liquid biopsy based assay of isolating tumor specific, human exosomes. We are analyzing the isolated exosomal cargo by next generation sequencing, looking for expression differences as well as mutations and novel microRNAs in high risk samples.
Hereby, we will identify biomarkers for high risk leukemia as well as new druggable targets.
The genotype of the original Wiskott phenotype. Binder V, Albert MH, Kabus M, Bertone M, Meindl A, and Belohradsky BH (2006). N Engl J Med 355, 1790-1793.
Hsa-mir-125b-2 is highly expressed in childhood ETV6/RUNX1 (TEL/AML1) leukemias and confers survival advantage to growth inhibitory signals independent of p53. Gefen N*, Binder V*, Zaliova M, Linka Y, Morrow M, Novosel A, Edry L, Hertzberg L, Shomron N, Williams O, Trka J, Borkhardt A, and Izraeli S (2010). Leukemia 24, 89-96. * Both authors contributed equally to this work
High throughput in vivo phenotyping: The zebrafish as tool for drug discovery for hematopoietic stem cells and cancer. Binder V, and Zon LI (2012). Drug Discovery Today: Disease Models.
A new workflow for whole-genome sequencing of single human cells. Binder V*, Bartenhagen C*, Okpanyi V, Gombert M, Moehlendick B, Behrens B, Klein HU, Rieder H, Ida Krell PF, Dugas M, Stoecklein NH, and Borkhardt A (2014). Hum Mutat 35, 1260-1270. * Both authors contributed equally to this work
Epoxyeicosatrienoic acids enhance embryonic haematopoiesis and adult marrow engraftment. Li P*, Lahvic JL*, Binder V*, Pugach EK, Riley EB, Tamplin OJ, Panigrahy D, Bowman TV, Barrett FG, Heffner GC, McKinney-Freeman S, Schlaeger TM, Daley GQ, Zeldin DC, and Zon LI (2015). Nature 523, 468-471.* These authors contributed equally to this work