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What GUCY2C Is

GUCY2C (guanylyl cyclase C, GC-C) is a single-pass transmembrane receptor abundantly expressed on intestinal epithelial cells. It is the receptor for the endocrine peptides guanylin and uroguanylin and for heat-stable bacterial enterotoxins; ligand binding activates its intracellular cyclase domain, raising intracellular cGMP. This cGMP signal drives chloride/water secretion, regulates gut transit, and — through AKT-dependent mechanisms — maintains tight-junction integrity, with 74 canonical tight-junction genes altered in GUCY2C-knockout miceGUCY2C knockout colitis and barrier study. A recent JCI review positions GUCY2C agonists among the emerging therapeutic levers of gut–brain signaling, alongside GLP-1 receptor agonistsGut-brain axis therapeutic review.

Human Evidence: the Activating Mutation

Familial Gastric Dysmotility Syndrome (FGDS) — a gain-of-function GUCY2C mutation — provides natural human evidence of GC-C physiology. In 21 FGDS patients vs 24 controls, median colonic transit time was prolonged (39.5 h vs 21.5 h, p=0.01), whole-gut transit nearly doubled (55.4 h vs 28.5 h, p<0.01), and luminal pH was higher in duodenum, small bowel, and colonFGDS GUCY2C activating-mutation motility study.

Cancer: Target and Biomarker

GUCY2C's near-restricted expression on intestinal epithelial cells and its persistence on colorectal tumors make it a leading CRC immunotherapy antigen; expert review lists GUCY2C alongside EGFR, HER2, and CEA among key precision-therapy targets, though no CRC immunotherapy has FDA approval to dateCRC immunotherapy precision-medicine review. Novel dual-antigen strategies exploit co-expression: a bispecific CDH17×GUCY2C ADC delivering the ferroptosis inducer RSL3 caused significant xenograft tumor regression in NU/NU mice (n=5/group) with limited hepatotoxicity in preclinical modelsCDH17-GUCY2C bispecific RSL3 ADC study. Anti-GUCY2C antibodies are also being computationally engineered: a structure-guided scFv analysis of four linkers (docking against GUCY2C-ECD, PDB 8GHP) found linker L1 predicted to be most favorable (ΔG_bind −55.75 kcal/mol)Anti-GUCY2C scFv linker computational study. As a liquid biopsy, serum GUCY2C mRNA distinguished metastatic CRC from controls (AUC 0.896) and correlated with antiangiogenic therapy response (p=0.047), though no marker predicted survivalSerum GUCY2C diagnostic AUC study.

Context and Blind Spots

In Apc1638N/+ mice exposed to high-LET 28Si radiation, GUCY2C IHC intensity increased at 60 and 150 days, interpreted by the authors as a metaplasia/proliferation marker alongside rising 8-OxodG and tumorsSpace-radiation intestinal tumorigenesis study. Key uncertainties: the scFv linker findings are purely computational and unvalidated; the biomarker cohort (n=59) is small, single-center, and lacks external validation; the r=+1.0 radiation correlations rest on only two timepoints and are near-circular by construction; and most mechanistic data derive from mouse models whose relevance to human GUCY2C physiology remains incompletely established. Evidence falsifying the therapeutic-antigen role would include failed GUCY2C-targeted efficacy in randomized CRC trials or off-target binding to normal intestinal epithelium in dose-ranging safety studies.

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Updated: September 21, 2026

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