The G-protein coupled receptor 56, expressed in colonic stem and cancer cells, binds progastrin to promote proliferation and carcinogenesis

Oncotarget. 2017 Jun 20;8(25):40606-40619. doi: 10.18632/oncotarget.16506.


Overexpression of human progastrin increases colonic mucosal proliferation and colorectal cancer progression in mice. The G-protein coupled receptor 56 (GPR56) is known to regulate cell adhesion, migration, proliferation and stem cell biology, but its expression in the gut has not been studied. We hypothesized that the promotion of colorectal cancer by progastrin may be mediated in part through GPR56. Here, we found that GPR56 expresses in rare colonic crypt cells that lineage trace colonic glands consistent with GPR56 marking long-lived colonic stem-progenitor cells. GPR56 was upregulated in transgenic mice overexpressing human progastrin. While recombinant human progastrin promoted the growth and survival of wild-type colonic organoids in vitro, colonic organoids cultured from GPR56-/- mice were resistant to progastrin. We found that progastrin directly bound to, and increased the proliferation of, GPR56-expressing colon cancer cells in vitro, and proliferation was increased in cells that expressed both GPR56 and the cholecystokinin-2 receptor (CCK2R). In vivo, deletion of GPR56 in the mouse germline abrogated progastrin-dependent colonic mucosal proliferation and increased apoptosis. Loss of GPR56 also inhibited progastrin-dependent colonic crypt fission and colorectal carcinogenesis in the azoxymethane (AOM) mouse model of colorectal cancer. Overall, we found that progastrin binds to GPR56 expressing colonic stem cells, which in turn promotes their expansion, and that this GPR56-dependent pathway is an important driver and potential new target in colorectal carcinogenesis.

Keywords: GPR56; colorectal cancer; progastrin; proliferation; stem cell.

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Carcinogenesis / drug effects
  • Carcinogenesis / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Proliferation / genetics
  • Colon / metabolism
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / pathology
  • Gastrins / genetics
  • Gastrins / metabolism*
  • Gastrins / pharmacology
  • Humans
  • Intestinal Mucosa / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Protein Binding
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Protein Precursors / pharmacology
  • Receptor, Cholecystokinin B / genetics
  • Receptor, Cholecystokinin B / metabolism
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Stem Cells / metabolism*


  • GPR56 protein, mouse
  • Gastrins
  • Protein Precursors
  • Receptor, Cholecystokinin B
  • Receptors, G-Protein-Coupled
  • big gastrin