RNA sequencing of cancer-associated fibroblasts (CAFs) and normal fibroblasts from a triple-transgenic gastric cancer mouse model

Gastric cancer is the 3rd most lethal cancer worldwide, and the genomic status of its cancer cells has not translated into effective prognostic or therapeutic strategies. We therefore hypothesize that outcomes may depend on the tumor microenvironment (TME), and in particular cancer-associated fibroblasts (CAFs). However, very little is known about the role of CAFs in gastric cancer. To address this, we map the transcriptional landscape of human gastric cancer stroma by microdissection and RNA sequencing of CAFs from gastric cancer patients. We find a stromal gene signature associated with poor disease outcome. This signature is regulated by the transcription factor Heat Shock Factor 1 (HSF1), that activates CAF-derived extracellular vesicles (EVs) that transfer components including Inhibin Subunit Beta A (INHBA) and Thrombospondin 2 (THBS2), to the TME to promote cancer. Together, our work provides the first transcriptional map of human gastric cancer stroma, and highlights HSF1 and its transcriptional targets as potential diagnostic and therapeutic targets in the genomically stable tumor microenvironment. Gastric cancer was induced in the triple-transgenic iLgr5;GLI2A mice as described in Syu et al, 2016. Mice which developed gastric cancer and control mice were sacrificed, CAFs were isolated from their stomachs and sequenced.