Figure 2.

Interaction between Hedgehog (HH) signaling and the tumor microenvironment in gastrointestinal tumor cells. Red arrow: upregulation; black arrow: downregulation; green dashed arrow: secretion; solid line: direct interaction; dashed line: indirect interaction. CAFs, cancer-associated fibroblasts; DHH, Desert Hedgehog; IHH, Indian Hedgehog; SHH, Sonic Hedgehog; NK cells, natural killer cells; PTCH, Patched; SMO, Smoothened; TGF-β, Transforming growth factor β; IL-6, interleukin 6; IFN-γ, interferon γ; HIF-1α, hypoxia-inducible factor 1α; RNA, ribonucleic acid; STAT3, signal transducer and activator of transcription 3; SMAD, Drosophila mothers against decapentaplegic protein; GLI, glioma-associated oncogene homologue.