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Significance of gene mutations in the Wnt signaling pathway in traditional serrated adenomas of the colon and rectum.

ABSTRACT: Recent studies have shown that colorectal serrated lesions, which include sessile serrated adenomas (SSAs) and traditional serrated adenomas (TSAs), are precursors of colorectal cancer. However, the molecular mechanisms underlying the carcinogenesis, particularly in TSAs, remain largely uncharacterized. To clarify their molecular and clinicopathological characteristics, we performed mutation and methylation analyses of cancer-associated genes in 78 serrated lesions, including TSAs, SSAs and microvesicular hyperplastic polyps. Target exon sequence analysis was performed with 39 genes, including genes known to be frequently mutated in colorectal cancers and/or serrated lesions. We also used bisulfite pyrosequencing to assess the methylation status of various cancer-associated genes and marker genes of the CpG island methylator phenotype (CIMP). The prevalence of mutations in genes associated with Wnt signaling was significantly higher in TSAs than SSAs (65% vs. 28%, p < 0.01). Among those, RNF43 mutations were observed in 38% of TSAs and 17% of SSAs. In immunohistochemical studies of 39 serrated lesions, the prevalence of abnormal nuclear ?-catenin accumulation was significantly higher in TSAs (57%) than SSAs (8%) (P = 0.01). SMOC1 methylation was detected in 54% of TSAs but in no SSAs (p < 0.01). Additionally, SMOC1 methylation was more prevalent among TSAs with KRAS mutation (82%) than with BRAF mutation (38%, p = 0.03). Lesions with CIMP-high or RNF43 mutations were detected only in TSAs with BRAF mutation, suggesting two distinct carcinogenic pathways in TSAs. Mutations in genes associated with Wnt signaling play a greater role in the carcinogenesis of TSAs than SSAs.

SUBMITTER: Nakanishi H

PROVIDER: S-EPMC7039454 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Significance of gene mutations in the Wnt signaling pathway in traditional serrated adenomas of the colon and rectum.

Nakanishi Hiroyoshi H Sawada Takeshi T Kaizaki Yasuharu Y Ota Ryosuke R Suzuki Hiromu H Yamamoto Eiichiro E Aoki Hironori H Eizuka Makoto M Hasatani Kenkei K Takahashi Naoki N Inagaki Satoko S Ebi Masahide M Kato Hiroyuki H Kubota Eiji E Kataoka Hiromi H Takahashi Satoru S Tokino Takashi T Minamoto Toshinari T Sugai Tamotsu T Sasaki Yasushi Y

PloS one 20200224 2

Recent studies have shown that colorectal serrated lesions, which include sessile serrated adenomas (SSAs) and traditional serrated adenomas (TSAs), are precursors of colorectal cancer. However, the molecular mechanisms underlying the carcinogenesis, particularly in TSAs, remain largely uncharacterized. To clarify their molecular and clinicopathological characteristics, we performed mutation and methylation analyses of cancer-associated genes in 78 serrated lesions, including TSAs, SSAs and micr ...[more]

PMID: 32092099

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Project description:Sessile serrated adenomas are now recognized as precursor lesions of a substantial subset of colorectal cancers arising via a so-called “serrated pathway”. However, their biological markers remain to be defined. The aim of our study was to identify differentially expressed genes in sessile serrated adenomas, hyperplastic polyps and tubular adenomas. Gene expression analysis demonstrated molecular differences between polyp types. Further studies using QRT-PCR on Cathepsin E demonstrated a significantly (p< 0.05) higher expression in sessile serrated adenomas as compared to both other polyp types. Trefoil Factor 1, showed the same trend of expression for sessile serrated adenomas as compared to hyperplastic polyps, and was significantly higher in both polyps compared to tubular adenomas. Immunohistochemistry for both proteins demonstrated strong cytoplasmic staining of abnormal crypts in all sessile serrated adenomas while staining in tubular adenomas and hyperplastic polyps was weak and focal. BRAF and KRAS mutation analysis were employed to further validate polyp discrimination. The findings demonstrated the positive association of the BRAF mutation, V600E, with sessile serrated adenomas and KRAS mutations with tubular adenomas (P<0.05). This study demonstrates CTSE and TFF1 over-expression in sessile serrated adenomas compared to both hyperplastic polyps and tubular adenomas. Keywords: colonic polyp tissue comparison, linear modelling, SSA Microarray analysis was performed on 13 SSAs and 11 TAs. SSAs were from 4 males and 9 females (mean age of 75) and TAs were from 5 males and 6 females (mean age of 72). Samples were directly hybridised to each other (SSA versus TA) or to a pooled normal control (SSA versus control). A linear model (Smyth 2004) was fitted to the data bringing together the three contrasts: SSA versus control, TA versus control and SSA versus TA. Human OligoLibrary (Compugen Human Oligo Library (v1) containing 18861 60-mer oligonucleotides, representing approximately 16,000 unique genes) by the Adelaide Microarray Centre (Australia) was used. Slides were scanned using a GenePix 3000B scanner (Axon Instruments, Sunnydale, CA), and the Spot package (CSIRO, Australia) was used to identify spots and estimate fore- and background intensities (using a morphological opening background estimator) (Yang, Buckley et al. 2001; Ritchie 2004). Data analysis was performed in R (www.r-project.org) using the Limma package of Bioconductor (Gentleman, Carey et al. 2004; Smyth 2004). Loess print tip method was used to correct for dye-bias and intensity within each group of adjacent spots printed by one pin (Yang, Dudoit et al. 2002). Linear modelling was performed with the Limma package of Bioconductor (Smyth 2004).

Project description:Studies have revealed that genetic and functional aberrations of oncogenes, tumor?suppressor genes, signaling pathways and receptors are among the most prominent events in pituitary tumorigenesis, and a potent biomarker would be helpful for early diagnosis, subsequent treatment and disease control. The present study investigated the expression signatures of solute carrier family 20 member 1, also known as phosphate transporter 1 (SLC20A1) and the Wnt/??catenin signaling pathway in 52 patients with somatotroph adenomas. According to immunohistochemistry analysis, the H?score of SLC20A1 was 222.6±15.2 in invasive tumor samples and 144.5±30.4 in non?invasive tumor samples (P<0.01), while the H?scores of ??catenin were 210.1±21.4 and 134.9±32.7, respectively (P<0.05). The H?scores of Wnt inhibitory factor 1 (Wif1) exhibited the opposite trend, with scores of 134.5±22.7 and 253.6±14.8, respectively (P<0.01). The H?scores of SLC20A1 were negatively associated with those of Wif1 in somatotroph adenomas (correlation coefficient r=?0.367). The mean progression?free survival in the low SLC20A1 group was longer than that in the group with high SLC20A1 H?scores (P=0.024). Reverse transcription?quantitative PCR (RT?qPCR) and western blotting confirmed the interference efficiency of the segments short hairpin (Sh)?B?SLC20A1 and Sh?C?SLC20A1. Cell proliferation experiments revealed that the cell viability of the Sh?B?SLC20A1 group was 76.3±4.5, 65.7±3.7 and 53.1±3.2% of that of control GH3 cells after 24, 48 and 72 h of transfection, respectively, while the cell viability of the Sh?C?SLC20A1 group was 86.4±5.7, 75.6±4.4 and 67.5±3.8%, respectively (P<0.05). ELISA analysis demonstrated the growth hormone (GH) levels in the Sh?B?SLC20A1 and Sh?C?SLC20A1 groups to be 34.7±10.4 and 54.6±14.4%, respectively, of that of control GH3 cells (P<0.05). The transmembrane invasion assay revealed that knocking down SLC20A1 signi?cantly suppressed cell invasion in the Sh?B?SLC20A1 and Sh?C?SLC20A1 groups. RT?qPCR and western blotting demonstrated that Sh?B?SLC20A1 and Sh?C?SLC20A1 evidently increased the levels of Wif1 and secreted frizzled?related protein 4. The present data suggested that SLC20A1 levels are positively associated with tumor size, invasive behavior and tumor recurrence in somatotroph adenomas. Furthermore, SLC20A1 may be associated with the activation of the Wnt/??catenin signaling pathway.

Project description:Many cancers in the proximal colon develop via from sessile serrated adenomas (SSAs), which have flat, subtle features that are difficult to detect with conventional white-light colonoscopy. Many SSA cells have the V600E mutation in BRAF. We investigated whether this feature could be used with imaging methods to detect SSAs in patients.We used phage display to identify a peptide that binds specifically to SSAs, using subtractive hybridization with HT29 colorectal cancer cells containing the V600E mutation in BRAF and Hs738.St/Int cells as a control. Binding of fluorescently labeled peptide to colorectal cancer cells was evaluated with confocal fluorescence microscopy. Rats received intra-colonic 0.0086 mg/kg, 0.026 mg/kg, or 0.86 mg/kg peptide or vehicle and morbidity, mortality, and injury were monitored twice daily to assess toxicity. In the clinical safety study, fluorescently labeled peptide was topically administered, using a spray catheter, to the proximal colon of 25 subjects undergoing routine outpatient colonoscopies (3 subjects were given 2.25 ?mol/L and 22 patients were given 76.4 ?mol/L). We performed blood cell count, chemistry, liver function, and urine analyses approximately 24 hours after peptide administration. In the clinical imaging study, 38 subjects undergoing routine outpatient colonoscopies, at high risk for colorectal cancer, or with a suspected unresected proximal colonic polyp, were first evaluated by white-light endoscopy to identify suspicious regions. The fluorescently labeled peptide (76.4 ?mol/L) was administered topically to proximal colon, unbound peptide was washed away, and white-light, reflectance, and fluorescence videos were recorded digitally. Fluorescence intensities of SSAs were compared with those of normal colonic mucosa. Endoscopists resected identified lesions, which were analyzed histologically by gastrointestinal pathologists (reference standard). We also analyzed the ability of the peptide to identify SSAs vs adenomas, hyperplastic polyps, and normal colonic mucosa in specimens obtained from the tissue bank at the University of Michigan.We identified the peptide sequence KCCFPAQ and measured an apparent dissociation constant of Kd = 72 nM and an apparent association time constant of K = 0.174 min-1 (5.76 minutes). During fluorescence imaging of patients during endoscopy, regions of SSA had 2.43-fold higher mean fluorescence intensity than that for normal colonic mucosa. Fluorescence labeling distinguished SSAs from normal colonic mucosa with 89% sensitivity and 92% specificity. The peptide had no observed toxic effects in animals or patients. In the analysis of ex vivo specimens, peptide bound to SSAs had significantly higher mean fluorescence intensity than to hyperplastic polyps.We have identified a fluorescently labeled peptide that has no observed toxic effects in animals or humans and can be used for wide-field imaging of lesions in the proximal colon. It distinguishes SSAs from normal colonic mucosa with 89% sensitivity and 92% specificity. This targeted imaging method might be used in early detection of premalignant serrated lesions during routine colonoscopies. ClinicalTrials.gov ID: NCT02156557.

Project description:BackgroundRecent work led to recognize sessile serrated adenomas (SSA) as precursor to many of the sporadic colorectal cancers with microsatellite instability (MSI). However, comprehensive analyses of DNA methylation in SSA and MSI cancer have not been conducted.MethodsWith an array-based methylation sensitive amplified fragment length polymorphism (MS-AFLP) method we analyzed 8 tubular (TA) and 19 serrated (SSA) adenomas, and 14 carcinomas with (MSI) and 12 without (MSS) microsatellite instability. MS-AFLP array can survey relative differences in methylation between normal and tumor tissues of 9,654 DNA fragments containing all NotI sequences in the human genome.ResultsUnsupervised clustering analysis of the genome-wide hypermethylation alterations revealed no major differences between or within these groups of benign and malignant tumors regardless of their location in intergenic, intragenic, promoter, or 3' end regions. Hypomethylation was less frequent in SSAs compared with MSI or MSS carcinomas. Analysis of variance of DNA methylation between these four subgroups identified 56 probes differentially altered. The hierarchical tree of this subset of probes revealed two distinct clusters: Group 1, mostly composed by TAs and MSS cancers with KRAS mutations; and Group 2 with BRAF mutations, which consisted of cancers with MSI and MLH1 methylation (Group 2A), and SSAs without MLH1 methylation (Group 2B). AXIN2, which cooperates with APC and ?-catenin in Wnt signaling, had more methylation alterations in Group 2, and its expression levels negatively correlated with methylation determined by bisulfite sequencing. Within group 2B, low and high AXIN2 expression levels correlated significantly with differences in size (P = 0.01) location (P = 0.05) and crypt architecture (P = 0.01).ConclusionsSomatic methylation alterations of AXIN2, associated with changes in its expression, stratify SSAs according to some clinico-pathological differences. We conclude that hypermethylation of MLH1, when occurs in an adenoma cell with BRAF oncogenic mutational activation, drives the pathway for MSI cancer by providing the cells with a mutator phenotype. AXIN2 inactivation may contribute to this tumorigenic pathway either by mutator phenotype driven frameshift mutations or by epigenetic deregulation contemporary with the unfolding of the mutator phenotype.

Dataset Information

Significance of gene mutations in the Wnt signaling pathway in traditional serrated adenomas of the colon and rectum.

Publications

Significance of gene mutations in the Wnt signaling pathway in traditional serrated adenomas of the colon and rectum.

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