Plecanatide-mediated activation of guanylate cyclase-C suppresses inflammation-induced colorectal carcinogenesis in Apc+/Min-FCCC mice

AIM To evaluate the effect of orally administered plecanatide on colorectal dysplasia in Apc^(+/Min-FCCC) mice with dextran sodium sulfate(DSS)-induced inflammation. METHODS Inflammation driven colorectal carcinogenesis was induced in Apc^(+/Min-FCCC) mice by administering DSS in their drinking water. Mice were fed a diet supplemented with plecanatide(0-20 ppm) and its effect on the multiplicity of histopathologically confirmed polypoid,flat and indeterminate dysplasia was evaluated. Plecanatide-mediated activation of guanylate cyclase-C(GC-C) signaling was assessed in colon tissues by measuring cyclic guanosine monophosphate(cG MP) by ELISA, protein kinase G-II and vasodilator stimulated phosphoprotein by immunoblotting. Ki-67, c-myc and cyclin D1 were used as markers of proliferation. Cellular levels and localization of b-catenin in colon tissues were assessed by immunoblotting and immunohistochemistry, respectively. Uroguanylin(UG) and GC-C transcript levels were measured by quantitative reverse transcription polymerase chain reaction(RT-PCR). A mouse cytokine array panel was used to detect cytokines in the supernatant of colon explant cultures. RESULTS Oral treatment of Apc^(+/Min-FCCC) mice with plecanatide produced a statistically significant reduction in the formation of inflammation-driven polypoid, flat and indeterminate dysplasias. This anti-carcinogenic activity of plecanatide was accompanied by activation of cG MP/GC-C signaling mediated inhibition of Wnt/b-catenin signaling and reduced proliferation. Plecanatide also decreased secretion of pro-inflammatory cytokines(IL-6, IL-1 TNF), chemokines(MIP-1, IP-10) and growth factors(GCSF and GMCSF) from colon explants derived from mice with acute DSS-induced inflammation. The effect of plecanatidemediated inhibition of inflammation/dysplasia on endogenous expression of UG and GC-C transcripts was measured in intestinal tissues. Although GC-C expression was not altered appreciably, a statistically significant increase in the level of UG transcripts was detected in the proximal small intestine and colon, potentially due to a reduction in intestinal inflammation and/or neoplasia. Taken together, these results suggest that reductions in endogenous UG, accompanied by dysregulation in GC-C signaling, may be an early event in inflammation-promoted colorectal neoplasia; an event that can potentially be ameliorated by prophylactic intervention with plecanatide.CONCLUSION This study provides the first evidence that orally administered plecanatide reduces the multiplicity of inflammation-driven colonic dysplasia in mice, demonstrating the utility for developing GC-C agonists as chemopreventive agents.