Region-specific Wnt signaling responses promote gastric polyp formation in patients with familial adenomatous polyposis
Kevin P. McGowan, Elizabeth Delgado, Theresa M. Keeley, Elise S. Hibdon, D. Kim Turgeon, Elena M. Stoffel, Linda C. Samuelson
Kevin P. McGowan, Elizabeth Delgado, Theresa M. Keeley, Elise S. Hibdon, D. Kim Turgeon, Elena M. Stoffel, Linda C. Samuelson
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Research Article Gastroenterology

Region-specific Wnt signaling responses promote gastric polyp formation in patients with familial adenomatous polyposis

Abstract

Germline adenomatous polyposis coli (APC) mutation in patients with familial adenomatous polyposis (FAP) promotes gastrointestinal polyposis, including the formation of frequent gastric fundic gland polyps (FGPs). In this study, we investigated how dysregulated Wnt signaling promotes FGPs and why they localize to the corpus region of the stomach. We developed a biobank of FGP and surrounding nonpolyp corpus biopsies and organoids from patients with FAP for comparative studies. Polyp biopsies and polyp-derived organoids exhibited enhanced Wnt target gene expression. Polyp-derived organoids with intrinsically upregulated Wnt signaling showed poor tolerance to further induction, suggesting that high Wnt restricts growth. Targeted genomic sequencing revealed that most gastric polyps did not arise via APC loss of heterozygosity. Studies in genetic mouse models demonstrated that heterozygous Apc loss increased epithelial cell proliferation in the corpus but not the antrum, while homozygous Apc loss was not maintained in the corpus yet induced hyperproliferation in the antrum. Our findings suggest that heterozygous APC mutation in patients with FAP may be sufficient to drive polyp formation in the corpus region while subsequent loss of heterozygosity to further enhance Wnt signaling is not tolerated. This finding contextualizes the abundant yet benign nature of gastric polyps in FAP patient corpus compared with the rare, yet adenomatous polyps in the antrum.

Authors

Kevin P. McGowan, Elizabeth Delgado, Theresa M. Keeley, Elise S. Hibdon, D. Kim Turgeon, Elena M. Stoffel, Linda C. Samuelson

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Figure 3

Intrinsic Wnt tone patterns intrapatient FGP variability.

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Intrinsic Wnt tone patterns intrapatient FGP variability. (A) Polyp (P) ...
(A) Polyp (P) and nonpolyp (NP) biopsies were obtained to establish multiple polyp-derived organoids from each patient with FAP. (B) Organoids were grown in CN media with varying concentrations of CHIR, and growth was measured through ATP-dependent luminescence on day 5. (C) Representative images of H102NPα and H102Pγ following culture in 0–3 μM CHIR (scale bars = 100 μm). (D) Relative growth of H102 organoid lines as a function of CHIR concentration. Growth was normalized to the maximal growth observed for each line, with data shown as mean ± SD of triplicate wells. (E–G) Relative growth of organoid lines from 12 patients with FAP plotted as a function of CHIR concentration. Individual organoid lines are shown in gray, and the average of all lines is shown in color. (E) Nonpolyp organoid lines (blue, n = 23 lines). (F) Polyp organoid lines demonstrating normal-like growth (pink, n = 14 lines). (G) Polyp organoid lines demonstrating enhanced Wnt-independent growth (purple, n = 21 lines). (H) Relative growth of H102 organoid lines after 5 days of growth in 0 μM CHIR (WR-free media) versus LGR5 mRNA abundance after 6 days of growth in 60% WR. The trend line was calculated via linear regression analysis. (I) Relative mRNA abundance of Wnt target genes in FAP organoids after 6 days’ growth in 60% WR. Data shown as mean ± SD fold-change relative to patient-matched nonpolyp. NP: n = 19; P-N: n = 11; P-E: n = 13 (*P < 0.05, **P < 0.005 by 1-way ANOVA with Tukey’s multiple-comparison test). (J) Average NP, P-N, or P-E organoid thickness after 6 days’ growth in 60% WR (***P < 0.001). (K) Representative images of nonpolyp, normal-like polyp, and enhanced polyp organoids after 6 days’ growth in 60% WR (scale bars = 50 μm).