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The non-steroidal anti-inflammatory drug sulindac decreases size and number of adenomas after 4-6 months of treatment for familial adenomatous polyposis (FAP) patients. However, the underlying mechanism remains unknown. As stem cells are thought to be the tumor precursor cells, visualizing their behavior is crucial for monitoring tumor progression. Increased tag diversity in inactive genes is indicative of a protracted clonal evolution and consequently, increased risk for tumor formation. Therefore, the effect of sulindac on stem cell dynamics was studied. Normal appearing single crypts were laser microdissected in placebo- and sulindac- treated FAP patient tissue after which the methylation patterns were visualized by Next Generation Sequencing. A significant difference in tag diversity over time was found in the sulindac group compared to the placebo group (*p = 0.018), indicative of a shortened clonal evolution treated sulindac. The rate of change in tag diversity over time was correlated with polyp number change over time. No significant difference over time was observed in the percent methylation when comparing placebo vs sulindac. In conclusion, daily sulindac administration in FAP patients significantly altered colorectal stem cell dynamics, which might explain the chemopreventive action of this drug indicating that tag diversity may be used as a predictive biomarker.

Objective: Genetic predisposition to cancer in Peutz-Jeghers syndrome (PJS) and the role of germline serine-threonine kinase (LKB1) mutations are poorly understood. The authors studied the effect of germline LKB1 mutations on intestinal stem cell dynamics in unaffected flat PJS mucosa. Recent research has documented that the intestinal crypt houses multiple equipotent stem cell lineages. Lineages continuously compete through random drifts, while somatically inherited methylation patterns record clonal diversity., Design: To study the effect of germline LKB1 mutations on clonal expansion, the authors performed quantitative analyses of cardiac-specific homeobox methylation pattern diversity in crypts isolated from unaffected colonic mucosa obtained from archival PJS patient material. The authors compared methylation density and methylation pattern diversity in patients with PJS to those in patients with familial adenomatous polyposis and age-matched controls., Results: The percentage of total methylation is comparable between groups, but the number of unique methylation patterns is significantly increased for patients with familial adenomatous polyposis and patients with PJS compared to control subjects., Conclusions: Monoallelic LKB1 loss is not silent and provokes a protracted clonal evolution in the crypt. The increased methylation pattern diversity observed in unaffected PJS mucosa predicts that premalignant lesions will arise at an accelerated pace compared to the general population.

Background: Juvenile polyps are distinct hamartomatous malformations of the gastrointestinal tract that may occur in the heritable juvenile polyposis syndrome (JPS) or sporadically. Histologically, juvenile polyps are characterized by a marked increase of the stromal cell compartment, but an epithelial phenotype has also been reported. JPS has an increased risk of colorectal cancer but sporadic juvenile polyps do not. In 50% to 60% of patients with JPS, a germline mutation of the transforming growth factor-β/bone morphogenetic protein (BMP) pathway genes SMAD4 or BMPR1A is found. This study compares the histologic phenotype of juvenile polyps with a SMAD4 or BMPR1A germline mutation and sporadic juvenile polyps., Methods: Hematoxylin and Eosin-stained slides of 65 JPS polyps and 25 sporadic juvenile polyps were reviewed for histologic features and dysplasia. Systematic random crypt and stroma counts were obtained by count stereology, and a crypt-stroma ratio was determined. All polyps were subsequently categorized as type A (crypt-stroma ratio <1.00) or type B (crypt-stroma ratio ≥1.00), the latter referring to the epithelial phenotype. Cell cycle activity was assessed using immunohistochemistry ofthe proliferation marker Ki67, and mutation analysis was carried out for KRAS and APC to determine the involvement of the adenoma-carcinoma sequence., Results: Juvenile polyps with a SMAD4 germline mutation were predominantly type B, whereas type A was more common among juvenile polyps with a BMPR1A germline mutation. However, this distinction could not be ascribed to differences in cell cycle activity. Dysplasia was equally common in JPS polyps with either a SMAD4 or BMPR1A germline mutation, in which the involvement of the adenoma-carcinoma sequence does not seem to play a distinct role., Conclusion: Juvenile polyps in the setting of JPS exhibit distinct phenotypes correlating with the underlying genetic defect.

Purpose: Juvenile polyposis syndrome (JPS) can be caused by a germline defect of the SMAD4 gene. Somatic inactivation of SMAD4 occurs in pancreatic and colorectal cancers and is reflected by loss of SMAD4 immunohistochemistry. Here, SMAD4 immunohistochemistry as a marker of SMAD4 gene status and the role of SMAD4 in the adenoma-carcinoma sequence in neoplastic progression in JPS are studied., Experimental Design: Twenty polyps with a SMAD4 germline defect and 38 control polyps were studied by SMAD4 immunohistochemistry. Inactivation of the SMAD4 wild-type allele was studied in dysplastic epithelium and in areas with aberrant SMAD4 expression. APC, beta-catenin, p53, and K-ras were studied to evaluate the adenoma-carcinoma sequence., Results: Nine of 20 polyps with a SMAD4 germline defect showed loss of epithelial SMAD4 expression. Loss of heterozygosity of SMAD4 was found in five polyps and a somatic stop codon mutation was found in two polyps without loss of heterozygosity. Remarkably, somatic inactivation of epithelial SMAD4 did not always coincide with dysplasia and aberrant p53 staining was found in four of six dysplastic polyps with normal SMAD4 staining. One K-ras mutation was found in nine juvenile polyps with dysplasia. No evidence for Wnt activation was found., Conclusions: SMAD4 immunohistochemistry mirrors genetic status and provides a specific adjunct in the molecular diagnosis of JPS. However, epithelial SMAD4 inactivation is not required for polyp formation and is not obligatory for neoplastic progression in JPS. Instead, different routes to neoplasia in JPS caused by germline SMAD4 mutation seem to be operative, including somatic loss of SMAD4 and p53 inactivation without somatic loss of SMAD4.

Colorectal cancer is one of the leading causes of cancer-related death in the Western society, and the incidence is rising. Rare hereditary gastrointestinal polyposis syndromes that predispose to colorectal cancer have provided a model for the investigation of cancer initiation and progression in the general population. Many insights in the molecular genetic basis of cancer have emerged from the study of these syndromes. This review discusses the genetics and clinical manifestations of the three most common syndromes with gastrointestinal polyposis and an increased risk of colorectal cancer: familial adenomatous polyposis (FAP), juvenile polyposis (JP) and Peutz-Jeghers syndrome (PJS).