The Hedgehog Signaling Networks in Lung Cancer: The Mechanisms and Roles in Tumor Progression and Implications for Cancer Therapy

Figure 3

Modes of HH-GLI signaling pathway activation in cancer. (a) HH ligands constitutively activate the HH pathway in HH ligand-producing cancer cells by autocrine signaling. Cancer cells produce HH ligand, and secreted HH ligands activate the HH signaling pathway in these cancer cells. (b) Cancer cell-mediated production of HH ligands also activates the HH pathway in stroma cells (e.g., CAFs) to maintain cancer cells by paracrine signaling. (c) GLI family transcription factors are activated in a SMO-independent manner, called the noncanonical pathway. (d) SMO can also activate other signaling molecules in cancer cells.

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