Investigation of STAT2 Signaling in the tumor microenvironment

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SUMMARY Intercellular communication between tumor cells and stromal cells of which major components are fibroblasts play a significant role in tumor growth, cancer progression and metastasis. This proposal aims to investigate the role of STAT2 signaling in the exchange of communication between colorectal cancer (CRC) cells and stromal cancer-associated fibroblasts (CAFs) in the tumor microenvironment. Our preliminary show that a clinical correlation between high STAT2 expression and poor survival as well as a positive correlation between STAT2 and markers of CAFs. Analysis of tumor biopsies of CRC patients showed elevated STAT2 protein in the tumor and surrounding stroma. Studies in two animal models of CRC reveal that STAT2 is tumorigenic. RNA-Seq analysis exposed a transcriptional signature associated with tumor associated fibroblasts. Furthermore, we found that STAT2 facilitates the proliferation and invasion of tumor cells. In parallel, we found that induction of EGF expression in normal fibroblasts was poorly induced after incubation with conditioned medium from STAT2 deficient tumor cells. Given these observations, we postulate that STAT2 mediates the crosstalk between the tumor and CAFs leading to CRC disease progression. The objective is to: (1) Determine whether intrinsic tumor STAT2 signaling leads to reprogramming of normal fibroblasts to CAFs to promote tumor growth and (2) Determine whether STAT2 signaling in normal fibroblasts leads to their conversion to CAFs to enhance tumor growth. Completion of this study will reveal the importance of STAT2 signaling in the tumor microenvironment as the communication axis (unidirectional vs. bidirectional) between tumor cells and CAFs to enhance tumor growth, migration, and invasion. Significance: Treatment of advanced CRC by combining targeted therapies with chemotherapy has produced modest success. Delineating the oncogenic role of STAT2 signaling in the tumor microenvironment may lead to the development of novel therapeutic strategies. If results from our study reveal that STAT2 plays a dynamic role in the establishment of cell-to-cell communication in the tumor microenvironment, our findings will support a rationale to inhibit STAT2 signaling as a therapeutic intervention for the treatment of metastatic CRC.