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Group Kovarik

Collaboration of Jak-Stat pathway mutations and haploinsufficiency of tumor suppressor genes in hematological malignancies


Myeloproliferative neoplasms (MPN) are a group of chronic hyperproliferative myeloid malignancies frequently initiated by oncogenic mutations in the Jak-Stat pathway, such as Jak2V617F, Jak2exon12 or MPLW515L/K. Activation of Stat5 has been shown to mediate the hyperproliferative effect of the Jak2 and MPL mutations. MPNs thus represent an important model disease to study the Jak-Stat pathway. Appropriate MPN mouse models are available, providing a good link to the work on Jak-Stat signaling in the development and progression of hematopoietic cancer. Besides oncogenic activations of the Jak-Stat pathway, our genetic studies of MPN have identified frequent focal deletions of genes with an unclear role in hematopoietic cancer. In our clinical studies, these deletions are found to be associated with leukemic transformation of chronic phase MPN patients. Deletions frequently occur in transcription factors such as CUX1, FOXP1, ETV6, and IKZF1. We hypothesize that deletions in these candidate tumor suppressor genes (TSG) collaborate with oncogenes in the Jak-Stat pathway, thereby resulting in hyperactivation of tyrosine phosphorylated Stat5 (pYStat5).
We are aiming to understand whether specific TSG loss and hyperactivity of the Jak-Stat pathway causes progression to acute myeloid leukemia (AML). We will functionally validate the genetic lesions detected in MPN-patients with respect to their effects on hematopoiesis in transgenic mice. We will attempt to simulate the clinical observation that deletions of these TSG in the presence of Jak2V617F triggers leukemic transformation and follow this up with an extensive phenotypic comparative analysis. We will investigate gene expression data for signatures associated with activation of the Jak-Stat pathway and other core cancer pathways. Furthermore, we will explore the synergies and specific effects of cancer-associated defects to delineate the regulatory networks associated with the mutations in primary murine hematopoietic cells. Finally, we will explore the preclinical question of how murine models of MPN or AML respond to specific drugs targeting the Jak-Stat pathway.
The proposed project part will start with a characterization of the hematopoietic phenotype of mice carrying hemizygous deletions of CUX1, FOXP1, ETV6, and IKZF1 on a wild-type or Jak2V617F knock-in background. The primary hematopoietic cells with various combinations of oncogenes and TSG mutations will also be characterized for cellular functions in ex vivo cultures. Furthermore, we will use RNA-Seq to profile the changes in gene expression associated with the Jak2V617F driver mutation, TSG haploinsufficiency and their combinations.

Goals and Key Hypotheses:
Our research is based on the following hypotheses:
(1) IKZF1, CUX1, ETV6 and FOXP1 display a distinct hematopoietic phenotype and modify the MPN model expressing the Jak2V617F oncoprotein.
(2) Mice with combined activation of Jak-Stat and haploinsufficient loss of TSG-MPN display MPN phenotypes with shortened disease latency and more severe progression.
(3) Loss of TSG-MPN increases the activity of the Jak-Stat signalling axis.

Our specific goals are as follows:
(1) Characterize the hematopoietic phenotype of mice carrying hemizygous deletions of CUX, FOXP1, ETV6 and IKZF1 on a (a) wild-type and (b) Jak2V617F knock-in background.
(2) Validate the clinical observations that deletions of TSG in the presence of Jak2V617F trigger leukemic transformation in primary hematopoietic cells for cellular functions in ex vivo cultures and for clonal outgrowth as well as drug sensitivity; and examine engraftment and drug sensitivity in vivo.
(3) Study the changes in gene expression and expression signatures associated with activation of the Jak-Stat pathway in primary murine hematopoietic cells as a result of the Jak2V617F oncogene, TSG haploisufficiency and their combinations.

Antwort auf/zuklappen Report on funding period 1 (03/2006-03/2010)

Antwort auf/zuklappen Proposal for funding period 2 (03/2010-03/2013)


CeMM Research Center for Molecular Medicine
Austrian Academy of Sciences
Lazarettgasse 14, AKH BT 25.3
A-1090 Vienna, Austria


phone: +43(0)1 40160-70 027