Progastrin Stimulates Colonic Cell Proliferation via CCK2R- and β-Arrestin–Dependent Suppression of BMP2

Abstract

Background & Aims Progastrin stimulates colonic mucosal proliferation and carcinogenesis through the cholecystokinin 2 receptor (CCK2R)—partly by increasing numbers of colonic progenitor cells. However, little is known about the mechanisms by which progastrin stimulates colonic cell proliferation. We investigated the role of bone morphogenetic proteins (BMPs) in progastrin induction of colonic cell proliferation via CCK2R. Methods We performed microarray analysis to compare changes in gene expression in the colonic mucosa of mice that express a human progastrin transgene (hGAS), gastrin knockout (GAS−/−) mice, and C57BL/6 mice (controls); the effects of progastrin were also determined on in vitro colonic crypt cultures from cholecystokinin 2 receptor knockout (CCK2R−/−) and wild-type mice. Human colorectal and gastric cancer cells that expressed CCK2R were incubated with progastrin or Bmp2 protein; levels of β-arrestin-1 and -2 (ARRB1 and ARRB2) were knocked down using small interfering RNAs. Cells were analyzed for progastrin binding, proliferation, changes in gene expression, and symmetric cell division. Results The BMP pathway was downregulated in the colons of hGAS mice, compared with controls. Progastrin suppressed transcription of Bmp2 through a pathway that required CCK2R and was mediated by ARRB1 and ARRB2. In mouse colonic epithelial cells, downregulation of Bmp2 led to decreased phosphorylation of Smads1/5/8 and suppression of Id4. In human gastric and colorectal cancer cell lines, CCK2R was necessary and sufficient for progastrin binding and induction of proliferation; these effects were blocked when cells were incubated with recombinant Bmp2. Incubation with progastrin increased the number of CD44+, bromodeoxyuridine+, and NUMB+ cells, indicating an increase in symmetric divisions of putative cancer stem cells. Conclusions Progastrin stimulates proliferation in colons of mice and cultured human cells via CCK2R- and ARRB1- and 2-dependent suppression of Bmp2 signaling. This process promotes symmetric cell division.

Autocrine Secretion of Progastrin Promotes the Survival and Self-Renewal of Colon Cancer Stem–like Cells

“…The size of remaining colonospheres was smaller in progastrin-depleted cells than in controls ( Supplementary Fig. S2B), corroborating other studies demonstrating proproliferative and antiapoptotic effects of progastrin (19,31). Similar results were obtained upon neutralization of progastrin using selective polyclonal antibodies (Fig.…”

“…We previously demonstrated that progastrin regulates the Wnt and Notch pathways in colorectal cancer (12,14), suggesting that it could affect the phenotype of colon CSCs, which rely on these pathways for their survival (15). Progastrin was shown to promote the proliferation of progenitor cells in the mouse colonic epithelium (16) and a link has been suggested between progastrin expression and populations of cells expressing CD133 (17), DCAMKL1 (18), or CD44 (19) in mouse colonic crypts and human cancer cell lines. Yet, expression of these markers is not restricted to CSCs (20)(21)(22)(23), and the functional role of progastrin on CSC self-renewal and tumor-initiating potential has not been documented.…”

Novel, isoform-selective, cholecystokinin A receptor antagonist inhibits colon and pancreatic cancers in preclinical models through novel mechanism of action

“…Due to failure to diagnose at an early stage, the 5-year survival rate of these cancer patients is much less than that of many other cancers (1,5). Colon and pancreatic cancers lack targeted therapeutics due to heterogeneity of the disease and diverse causative factors, including Helicobacter pylori (H. Pylori) bacteria (6,7), gut hormones such as gastrin and cholecystokinin (CCK) (8,9), and activation of cyclooxygenase (10,11) and NF-κB pathways (12).…”

“…In addition, gastrin also plays important roles in cell proliferation and maturation of the GI tract. Gastrin is also produced in excess in gastrinoma or gastric cancers (6,8). Blocking gastrin action by antagonizing CCK receptors will reduce gastric cancer incidence and growth.…”

Gastrin attenuates ischemia-reperfusion-induced intestinal injury in rats

“…5 Gastrin has also been proved to stimulate enterochromaffin-like cells to produce histamine which contributes to the healing of experimentally induced ulcers in rat stomach. 6 Although precursor forms of gastrin, such as progastrin and glycine-extended gastrin have been found to encourage cell growth, division and hyperproliferation in normal murine colon, [7][8][9] few report that whether gastrin has effects upon small intestinal epithelial cells as the Cholecystokinin-2 (CCK-2) receptor is lowly expressed in the tissue. 10,11 Some researches have demonstrated that gastrin is often used as potential protein for facilitating proliferation in intestinal mucosa following ionizing radiation or chemical carcinogen.…”