Non-Canonical Hedgehog Signaling Is a Positive Regulator of the WNT Pathway and Is Required for the Survival of Colon Cancer Stem Cells

Cell Rep. 2017 Dec 5;21(10):2813-2828. doi: 10.1016/j.celrep.2017.11.025.

Abstract

Colon cancer is a heterogeneous tumor driven by a subpopulation of cancer stem cells (CSCs). To study CSCs in colon cancer, we used limiting dilution spheroid and serial xenotransplantation assays to functionally define the frequency of CSCs in a panel of patient-derived cancer organoids. These studies demonstrated cancer organoids to be enriched for CSCs, which varied in frequency between tumors. Whole-transcriptome analysis identified WNT and Hedgehog signaling components to be enhanced in CSC-enriched tumors and in aldehyde dehydrogenase (ALDH)-positive CSCs. Canonical GLI-dependent Hedgehog signaling is a negative regulator of WNT signaling in normal intestine and intestinal tumors. Here, we show that Hedgehog signaling in colon CSCs is autocrine SHH-dependent, non-canonical PTCH1 dependent, and GLI independent. In addition, using small-molecule inhibitors and RNAi against SHH-palmitoylating Hedgehog acyltransferase (HHAT), we demonstrate that non-canonical Hedgehog signaling is a positive regulator of WNT signaling and required for colon CSC survival.

Keywords: HHAT; PTCH1; SHH; WNT pathway; cancer organoid; cancer stem cell; colon cancer; non-canonical Hedgehog signaling.

MeSH terms

  • Animals
  • Colonic Neoplasms / metabolism*
  • Female
  • Hedgehog Proteins / metabolism*
  • Humans
  • Mice
  • Mice, Nude
  • Neoplastic Stem Cells / metabolism*
  • Patched-1 Receptor / genetics
  • Patched-1 Receptor / metabolism
  • Wnt Signaling Pathway / physiology

Substances

  • Hedgehog Proteins
  • Patched-1 Receptor