IL-6 mediates cross-talk between activated fibroblasts and tumor cells in the tumor microenvironment

The tumor microenvironment (TME) plays a major role in the pathogenesis of multiple cancer types, including upper-gastrointestinal (GI) cancers that currently lack effective therapeutic options. Cancer-associated fibroblasts (CAF) are an essential component of the TME, contributing to tumorigenesis by secreting growth factors, modifying the extracellular matrix, supporting angiogenesis, and suppressing anti-tumor immune responses. Through an unbiased approach, we have established that IL-6 mediates crosstalk between tumor cells and CAF not only by supporting tumor cell growth, but also by promoting fibroblast activation. As a result, IL-6 receptor (IL-6Rα) and downstream effectors offer opportunities for targeted therapy in upper-GI cancers. IL-6 loss suppressed tumorigenesis in physiologically relevant 3D organotypic and 3D tumoroid models and murine models of esophageal cancer. Tocilizumab, an anti-IL-6Rα antibody, suppressed tumor growth in vivo in part via inhibition of STAT3 and MEK/ERK signaling. Analysis of a pan-cancer TCGA dataset revealed an inverse correlation between IL-6 and IL-6Rα overexpression and patient survival. Therefore, we expanded evaluation of tocilizumab to head-and-neck squamous cell carcinoma patient-derived xenografts and gastric adenocarcinoma xenografts, demonstrating suppression of tumor growth and altered STAT3 and ERK1/2 gene signatures. We used small molecule inhibitors of STAT3 and MEK1/2 signaling to suppress tumorigenesis in the 3D organotypic model of esophageal cancer. We demonstrate that IL-6 is a major contributor to the dynamic crosstalk between tumor cells and CAF in the TME. Our findings provide a translational rationale for inhibition of IL-6Rα and downstream signaling pathways as a novel targeted therapy in oral-upper-GI cancers.

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