Inactivating cholecystokinin-2 receptor inhibits progastrin-dependent colonic crypt fission, proliferation, and colorectal cancer in mice

Abstract

Hyperproliferation of the colonic epithelium, leading to expansion of colonic crypt progenitors, is a recognized risk factor for colorectal cancer. Overexpression of progastrin, a nonamidated and incompletely processed product of the gastrin gene, has been shown to induce colonic hyperproliferation and promote colorectal cancer in mice, but the mechanism of pathogenesis has not been defined. Cholecystokinin-2 receptor (CCK2R) is the primary receptor for cholecystokinin (CCK) and amidated gastrin. Here, we show that Cck2r was expressed in murine colonic crypts and upregulated in the transgenic mice that overexpress human progastrin. Murine deletion of Cck2r abrogated progastrin-dependent increases in colonic proliferation, mucosal thickness, and β-catenin and CD44 expression in the colon tumor. In addition, either deletion or antagonism of Cck2r resulted in the inhibition of progastrin-dependent increases in progenitors expressing doublecortin and CaM kinase-like-1 (DCAMKL1), stem cells expressing leucine rich repeat-containing G protein-coupled receptor 5 (LgR5), and colonic crypt fission. Furthermore, in the azoxymethane mouse model of colorectal carcinogenesis, Cck2r deletion in human progastrin-overexpressing mice resulted in markedly decreased aberrant crypt foci formation and substantially reduced tumor size and multiplicity. Taken together, these observations indicate that progastrin induces proliferative effects, primarily in colonic progenitor cells, through a CCK2R-dependent pathway. Moreover, our data suggest that CCK2R may be a potential target in the treatment or prevention of colorectal cancer.

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

“…S1M and S1N) when compared with controls. In addition, convincing data from Jin and colleagues suggested that progastrin can act at least partly in vivo via activation of CCK2 receptors (16). Yet, we were not able to detect CCK2 receptor mRNA in the colorectal cancer cells used to characterize the effects of progastrin in this study (data not shown), suggesting that progastrin may display both direct and indirect effects and/or that the progastrin signaling networks in mice and human are somewhat different.…”

“…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.…”

In vivo analysis of mouse gastrin gene regulation in enhanced GFP-BAC transgenic mice

“…Separated serum was stored in Ϫ80°C until usage. Amidated gastrin levels were measured with antiserum 1296 as previously described (8,15).…”

Gastrin attenuates ischemia-reperfusion-induced intestinal injury in rats

“…The antiapoptotic effect of gastrin might be associated with CCK-2 signaling activity. It has been reported that CCK-2 pathway could enhance cell proliferation in intestinal epithelium, 25 which could counteract apoptotic pathway such as Bax expression.…”