Differential expression of small bowel TGFß1 and TGFß3 characterizes intestinal strictures in patients with fibrostenotic Crohn's disease.

Small bowel strictures remain a debilitating consequence of Crohn's disease and contribute to poor outcomes for patients. Recently, TGFß has been identified as an important driver of intestinal fibrosis. We studied the localization of TGFß isoforms in ileal strictures of patients with Crohn's disease using in situ hybridization to understand TGFß's role in stricture formation. The mucosa of strictures was characterized by higher TGFß1 while the stricture submucosa showed higher TGFß3 compared to normal ileum from patients without Crohn's disease (p = 0.02 and p = 0.044, respectively). We correlated these findings with single-cell transcriptomics which demonstrated that TGFß3 transcripts overall are very rare, which may partially explain why its role in intestinal fibrosis has remained unclear to date. There were no significant differences in fibroblast or B cell TGFß1 and/or TGFß3 expression in inflamed vs. noninflamed ileum. We discuss the implications of these findings for therapeutic development strategies to treat patients with fibrostenotic Crohn's disease.

Oncogenic RAS pathway activation promotes resistance to anti-VEGF therapy through G-CSF-induced neutrophil recruitment.

Granulocyte-colony stimulating factor (G-CSF) promotes mobilization of CD11b(+)Gr1(+) myeloid cells and has been implicated in resistance to anti-VEGF therapy in mouse models. High G-CSF production has been associated with a poor prognosis in cancer patients. Here we show that activation of the RAS/MEK/ERK pathway regulates G-CSF expression through the Ets transcription factor. Several growth factors induced G-CSF expression by a MEK-dependent mechanism. Inhibition of G-CSF release with a MEK inhibitor markedly reduced G-CSF production in vitro and synergized with anti-VEGF antibodies to reduce CD11b(+)Ly6G(+) neutrophil mobilization and tumor growth and led to increased survival in animal models of cancer, including a genetically engineered mouse model of pancreatic adenocarcinoma. Analysis of biopsies from pancreatic cancer patients revealed increased phospho-MEK, G-CSF, and Ets expression and enhanced neutrophil recruitment compared with normal pancreata. These results provide insights into G-CSF regulation and on the mechanism of action of MEK inhibitors and point to unique anticancer strategies.