Activation of NF-κB is required for mediating proliferative and antiapoptotic effects of progastrin on proximal colonic crypts of mice, in vivo

Abstract

Mice overexpressing progastrin (PG) in intestinal mucosa (fatty acid-binding protein (Fabp)-PG mice) are at an increased risk of proximal colon carcinogenesis in response to azoxymethane. Here, we report a significant increase in the length of proximal colonic crypts in Fabp-PG mice, associated with potent antiapoptotic effects of PG, which likely contributed to the previously reported increase in colon carcinogenesis in Fabp-PG mice. Phosphorylation of kinase of IjBa (IKKa/b), inhibitor of jB (IjB)a and p65NF-jB was significantly elevated in proximal colonic crypts of Fabp-PG versus wild-type mice, which was associated with degradation of IjBa and nuclear translocation/activation of p65. Surprisingly, distal colonic crypt cells were not as responsive to elevated levels of PG in Fabp-PG mice. Annexin II, recently described as a high-affinity receptor for PG, strongly colocalized with PG intracellularly and on basolateral membranes of proximal crypt cells, providing evidence that annexin-II binds PG in situ in colonic crypt cells. Proliferative and antiapoptotic effects of PG on proximal crypts of Fabp-PG mice were attenuated to wild-type levels, on treatment with NEMO peptide (an inhibitor of nuclear factor-jB (NF-jB) activation), demonstrating for the first time a critical role of NF-jB in mediating hyperproliferative affects of PG on colonic crypts of Fabp-PG mice, in vivo. Thus, downregulation of NF-jB may significantly reduce the increased risk of colon carcinogenesis in response to PG.

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.…”

A New Biomarker That Predicts Colonic Neoplasia Outcome in Patients with Hyperplastic Colonic Polyps

“…They also have an increased risk of developing preneoplastic lesions and adenocarcinomas in colonic epithelium when treated with a carcinogen, azoxymethane (13,14). The role of progastrin in proliferation, survival, and migration of human colon cancer cells has also been clearly established (15)(16)(17)(18)(19)(20). Progastrin growth-promoting effects are mediated through the activation of several key signal transduction pathways (21,22).…”

Insulin-like growth factors are more effective than progastrin in reversing proapoptotic effects of curcumin: critical role of p38MAPK

“…Activation of NF-B was determined by using the TransAM p65 NF-B transcription factor assay kit, as per instructions of the manufacturer, as recently described (32,44). Briefly, 10 g of nuclear extract samples were incubated in binding buffer with oligos containing NF-B consensus binding sites, immobilized in the wells, for 2 h at room temperature.…”

“…4B). To confirm functional relevance of the observed changes in phosphorylation status of p65, activation of NF-B was measured in a DNA binding assay, as described previously (32,44). Change in NF-B activity was calculated as a percent change from control (nonstimulated) values, wherein NF-B activity in control samples was assigned a 100% value.…”