Abstract #LB-127: JAK/STAT signaling in Ewing's sarcoma
Authors: Barbara Sax, Wolfgang Mikulits, Gerhard Müller-Newen, Christopher Poremba, Heinrich Kovar, Richard Moriggl
Journal: Cancer Research (2009)

Ewing\#8217;s sarcoma family of tumors (ESFT) comprises pediatric cancers of bone and soft tissue which presumably originate from mesenchymal stem cells (MSC). One hallmark of ESFT is the presence of a chromosomal translocation. In 90% of the cases the translocation occurs between chromosome 11 and chromosome 22 and generates the EWS/FLI-1 fusion which acts as an aberrant transcription factor deregulating many genes involved in tumor development. Cytokines either produced in the tumor microenvironment or released by tumor cells are important regulators of signaling networks controlling many functions necessary for a tumor cell such as proliferation, differentiation, survival or tumor surveillance. Among others, the Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathway regulates these entities and components of the pathway are often deregulated in human cancers. It has been previously demonstrated that JAK1 was upregulated and STAT3 was activated to variable degrees in patient samples. Thus, the role of the JAK/STAT pathway in ESFT was investigated. Three ESFT cell lines (SK-N-MC; STA-ET-7.2; TC71) with a differential profile of p53 mutation, EWS/FLI-1 fusion type, endogenous EWS expression and alteration of p16INK4A were analyzed. In plain monolayer culture activation of STAT1/3/5 was not observed (DNA binding analyzed by mobility shift assay). However, upon subcutaneous injection into immunocompromised mice ESFT cells had profound activation of STAT1/3. A selection of cytokines was tested and the three analyzed cell lines were highly responsive to Interferon (IFN)-\#945;, IFN-\#947;, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF) and onocstatin M (OSM) but surprisingly not to the wide-range cytokine Interleukin-6 (IL-6). Flow cytometric analysis demonstrated very little expression of the IL-6 receptor \#945; chain on these cells but gp130, LIF-R and OSM-R were highly expressed on the cell surface. Analysis of JAK/STAT specific target genes indicated that STAT1 targets were clearly upregulated in Interferon stimulated cells. Some STAT1 targets were also expressed in response to CNTF, LIF or OSM but STAT3 induced genes did not change their expression. A profound reduction in cell number was observed when cells were stimulated with IFN-\#947;. IFN-\#945; stimulation demonstrated a similar effect, but to a lesser extent. Proliferation in response to gp130-cytokines was not changed dramatically; LIF stimulation was able to enhance cell growth to some extent but only at high concentrations. In summary, components of the JAK/STAT signaling pathway were observed to be active in ESFT cell line xenografts and upon cytokine stimulation. Further analysis is needed to understand the biological function of STAT activation in ESFT. Currently, experiments are underway to compare the cytokine response and target gene expression profile of MSC to ESFT cells.  Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr LB-127.