Gene Signature in Sessile Serrated Polyps Identifies Colon Cancer Subtype

FAK loss reduces BRAFV600E-induced ERK phosphorylation to promote intestinal stemness and cecal tumor formation

BRAFV600E mutation is a driver mutation in the serrated pathway to colorectal cancers. BRAFV600E drives tumorigenesis through constitutive downstream extracellular signal-regulated kinase (ERK) activation, but high-intensity ERK activation can also trigger tumor suppression. Whether and how oncogenic ERK signaling can be intrinsically adjusted to a 'just-right' level optimal for tumorigenesis remains undetermined. In this study, we found that FAK (Focal adhesion kinase) expression was reduced in BRAFV600E-mutant adenomas/polyps in mice and patients. In Vil1-Cre;BRAFLSL-V600E/+;Ptk2fl/fl mice, Fak deletion maximized BRAFV600E's oncogenic activity and increased cecal tumor incidence to 100%. Mechanistically, our results showed that Fak loss, without jeopardizing BRAFV600E-induced ERK pathway transcriptional output, reduced EGFR (epidermal growth factor receptor)-dependent ERK phosphorylation. Reduction in ERK phosphorylation increased the level of Lgr4, promoting intestinal stemness and cecal tumor formation. Our findings show that a 'just-right' ERK signaling optimal for BRAFV600E-induced cecal tumor formation can be achieved via Fak loss-mediated downregulation of ERK phosphorylation.

Evaluation of EGFR and COX pathway inhibition in human colon organoids of serrated polyposis and other hereditary cancer syndromes

Serrated polyposis syndrome (SPS) presents with multiple sessile serrated lesions (SSL) in the large intestine and confers increased colorectal cancer (CRC) risk. However, the etiology of SPS is not known. SSL-derived organoids have not been previously studied but may help provide insights into SPS pathogenesis and identify novel biomarkers and chemopreventive strategies. This study examined effects of EGFR and COX pathway inhibition in organoid cultures derived from uninvolved colon and polyps of SPS patients. We also compared with organoids representing the hereditary gastrointestinal syndromes, Familial Adenomatous Polyposis (FAP) and Lynch syndrome (LS). Eighteen total organoid colon cultures were generated from uninvolved colon and polyps in SPS, FAP, LS, and non-syndromic screening colonoscopy patients. BRAF and KRAS mutation status was determined for each culture. Erlotinib (EGFR inhibitor) and sulindac (COX inhibitor) were applied individually and in combination. A 44-target gene custom mRNA panel (including WNT and COX pathway genes) and a 798-gene microRNA gene panel were used to quantitate organoid RNA expression by NanoString analysis. Erlotinib treatment significantly decreased levels of mRNAs associated with WNT and MAPK kinase signaling in organoids from uninvolved colon from all four patient categories and from all SSL and adenomatous polyps. Sulindac did not change the mRNA profile in any culture. Our findings suggest that EGFR inhibitors may contribute to the chemopreventive treatment of SSLs. These findings may also facilitate clinical trial design using these agents in SPS patients. Differentially expressed genes identified in our study (MYC, FOSL1, EGR1, IL33, LGR5 and FOXQ1) may be used to identify other new molecular targets for chemoprevention of SSLs.

FAK loss reduces BRAFV600E-induced ERK phosphorylation to promote intestinal stemness and cecal tumor formation

BRAF V600E mutation is a driver mutation in the serrated pathway to colorectal cancers. BRAFV600E drives tumorigenesis through constitutive downstream extracellular signal-regulated kinase (ERK) activation, but high-intensity ERK activation can also trigger tumor suppression. Whether and how oncogenic ERK signaling can be intrinsically adjusted to a "just-right" level optimal for tumorigenesis remains undetermined. In this study, we found that FAK (Focal adhesion kinase) expression was reduced in BRAFV600E-mutant adenomas/polyps in mice and patients. In Vill-Cre;BRAFV600E/+;Fakfl/fl mice, Fak deletion maximized BRAFV600E's oncogenic activity and increased cecal tumor incidence to 100%. Mechanistically, our results showed that Fak loss, without jeopardizing BRAFV600E-induced ERK pathway transcriptional output, reduced EGFR (epidermal growth factor receptor)-dependent ERK phosphorylation. Reduction in ERK phosphorylation increased the level of Lgr4, promoting intestinal stemness and cecal tumor formation. Our findings show that a "just-right" ERK signaling optimal for BRAFV600E-induced cecal tumor formation can be achieved via Fak loss-mediated downregulation of ERK phosphorylation.

Enhanced SREBP2-driven cholesterol biosynthesis by PKCλ/ι deficiency in intestinal epithelial cells promotes aggressive serrated tumorigenesis

The metabolic and signaling pathways regulating aggressive mesenchymal colorectal cancer (CRC) initiation and progression through the serrated route are largely unknown. Although relatively well characterized as BRAF mutant cancers, their poor response to current targeted therapy, difficult preneoplastic detection, and challenging endoscopic resection make the identification of their metabolic requirements a priority. Here, we demonstrate that the phosphorylation of SCAP by the atypical PKC (aPKC), PKCλ/ι promotes its degradation and inhibits the processing and activation of SREBP2, the master regulator of cholesterol biosynthesis. We show that the upregulation of SREBP2 and cholesterol by reduced aPKC levels is essential for controlling metaplasia and generating the most aggressive cell subpopulation in serrated tumors in mice and humans. Since these alterations are also detected prior to neoplastic transformation, together with the sensitivity of these tumors to cholesterol metabolism inhibitors, our data indicate that targeting cholesterol biosynthesis is a potential mechanism for serrated chemoprevention.

Three Pathologic Criteria for Reproducible Diagnosis of Colonic Sessile Serrated Lesion Versus Hyperplastic Polyp

BACKGROUND

Colonic sessile serrated lesions are thought to predispose to ∼30% of colonic adenocarcinomas. This increased risk, compared to benign hyperplastic polyps, makes their distinction vitally important. However, no gold standard exists to differentiate them, and wide observer variability is reported.

METHODS

To better distinguish these polyps, we investigated 94 serrated polyps (53 sessile serrated lesions and 41 hyperplastic polyps), using an easy-to-apply pathologic scoring system that combines, for the first time, three established distinguishing features: polyp morphology, location, and size. As an additional novel approach, polyp size was assessed by serrated biopsy number compared to endoscopic size. RNA expression profiling served as an additional biomarker. The considerable morphologic overlap across serrated polyps was quantitated for the first time. Interobserver variability was assessed by eight expert gastrointestinal pathologists.

RESULTS

By ROC analysis, polyp size by biopsy number performed best, followed by polyp location and morphology (areas under the curves [AUC] 85.9%, 81.2%, 65.9%, respectively). Optimal discrimination combined all three features (AUC 92.9%). For polyp size, biopsy number proved superior to endoscopic size (AUC 85.9% versus 55.2%, p=0.001). Interobserver variability analysis yielded the highest reported Fleiss and Kappa statistics (0.879) and percent agreement (96.8%), showing great promise toward improved diagnosis.

CONCLUSIONS

The proposed three-criteria pathologic system, combining size by biopsy number, location, and morphology, yields an improved, easy to use, and highly reproducible diagnostic approach for differentiating sessile serrated lesions and hyperplastic polyps.

Transcriptome of sessile serrated adenoma/polyps is associated with MSI-high colorectal cancer and decreased expression of CDX2

The objective of this study was to elucidate the molecular background of sessile serrated adenoma/polyp (SSA/P) endoscopically resected with comprehensive gene expression analysis. Gene expression profiling was performed for 10 tumor-normal pairs of SSA/P. Cluster analysis, gene set enrichment analysis (GSEA), and consensus molecular subtype (CMS) classification of colorectal cancer (CRC) were applied to our transcriptome analysis. Unsupervised cluster analysis showed that the gene expression profile of SSA/Ps is different from that of adjacent normal epithelial cells, even in the very early stage of tumorigenesis. According to the CMS classification, our microarray data indicated that SSA/Ps were classified as CMS1. GSEA demonstrated a strong association between SSA/P and microsatellite instability-high (MSI-H) CRC (p < 10^-5 ). Transcriptome analysis of five MSI-related genes (MSH2, MSH6, MLH1, PMS1, and PMS2) and five CRC-related genes (BRAF, KRAS, APC, TP53, and CDX2) showed that CDX2 expression was most severely decreased in SSA/P. Immunohistochemical staining confirmed that CDX2 protein was reduced compared with the surrounding mucosa. Direct sequencing of the BRAF gene showed that the BRAF V600E mutation was detected in only nine of 36 cases. In a mouse model, BRAF, APC, or CDX2 deficiency indicated that the gene expression pattern with loss of CDX2 is more similar to our SSA/Ps compared with those induced by BRAF or APC mutation. Transcriptome analysis of SSA/Ps showed characteristic gene expression with a strong resemblance to MSI-H CRC. Downregulation of CDX2 expression is an essential molecular mechanism involved in the initial stage of SSA/P tumorigenesis. (UMIN000027365).

Chemoprevention for Colorectal Cancers: Are Chemopreventive Effects Different Between Left and Right Sided Colorectal Cancers?

BACKGROUND AND AIMS

Recent studies have suggested that right- and left-sided colorectal cancers (CRCs) are molecularly distinct. In this study, we examined the association between the risk of right- and left-sided CRC and drug use to estimate their chemopreventive effects METHODS: This multicenter retrospective cohort study was conducted using the data of hospitalized patients between 2014 and 2019 from nine hospital databases. The primary outcomes were right- and left-sided CRC. We evaluated the association of CRCs with drug use and clinical factors. Odds ratios adjusted for age, sex, Charlson Comorbidity Index scores, and smoking status were calculated. We also compared the transcriptional profiling in precancerous lesions, including sessile serrated lesions (SSLs) RESULTS: A total of 307,938 patients, including 2745 with right-sided CRC and 4819 with left-sided CRC, were analyzed. The use of nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, cyclooxygenase-2 inhibitors, and steroids was associated with a lower risk of both right- and left-sided CRCs. In contrast, statins, other lipid-lowering agents, and metformin were associated with a lower risk of left-sided CRC. Transcriptomic analysis showed that SSL, which predominantly develops in the right colon, was associated with a lower expression of lipid metabolism-related genes.

CONCLUSIONS

Targeting lipid metabolism may be useful for chemoprevention of left-sided CRCs, while development of right-sided CRCs may be independent of this pathway.

Bioinformatics Analysis of RNA-seq Data Reveals Genes Related to Cancer Stem Cells in Colorectal Cancerogenesis

Cancer stem cells (CSC) play one of the crucial roles in the pathogenesis of various cancers, including colorectal cancer (CRC). Although great efforts have been made regarding our understanding of the cancerogenesis of CRC, CSC involvement in CRC development is still poorly understood. Using bioinformatics and RNA-seq data of normal mucosa, colorectal adenoma, and carcinoma (n = 106) from GEO and TCGA, we identified candidate CSC genes and analyzed pathway enrichment analysis (PEI) and protein–protein interaction analysis (PPI). Identified CSC-related genes were validated using qPCR and tissue samples from 47 patients with adenoma, adenoma with early carcinoma, and carcinoma without and with lymph node metastasis and were compared to normal mucosa. Six CSC-related genes were identified: ANLN, CDK1, ECT2, PDGFD, TNC, and TNXB. ANLN, CDK1, ECT2, and TNC were differentially expressed between adenoma and adenoma with early carcinoma. TNC was differentially expressed in CRC without lymph node metastases whereas ANLN, CDK1, and PDGFD were differentially expressed in CRC with lymph node metastases compared to normal mucosa. ANLN and PDGFD were differentially expressed between carcinoma without and with lymph node metastasis. Our study identified and validated CSC-related genes that might be involved in early stages of CRC development (ANLN, CDK1, ECT2, TNC) and in development of metastasis (ANLN, PDGFD).

miRNome Profiling and Functional Analysis Reveal Involvement of hsa-miR-1246 in Colon Adenoma-Carcinoma Transition by Targeting AXIN2 and CFTR

Regulatory changes occurring early in colorectal cancer development remain poorly investigated. Since the majority of cases develop from polyps in the adenoma-carcinoma transition, a search of early molecular features, such as aberrations in miRNA expression occurring prior to cancer development, would enable identification of potentially causal, rather than consequential, candidates in the progression of polyp to cancer. In the current study, by employing small RNA-seq profiling of colon biopsy samples, we described differentially expressed miRNAs and their isoforms in the adenoma-carcinoma transition. Analysis of healthy-adenoma-carcinoma sequence in an independent validation group enabled us to identify early deregulated miRNAs including hsa-miR-1246 and hsa-miR-215-5p, the expressions of which are, respectively, gradually increasing and decreasing. Loss-of-function experiments revealed that inhibition of hsa-miR-1246 lead to reduced cell viability, colony formation, and migration rate, thereby indicating an oncogenic effect of this miRNA in vitro. Subsequent western blot and luciferase reporter assay provided evidence of hsa-miR-1246 being involved in the regulation of target AXIN2 and CFTR genes’ expression. To conclude, the present study revealed possible involvement of hsa-miR-1246 in early colorectal cancer development and regulation of tumor suppressors AXIN2 and CFTR.

Molecular drivers of tumor progression in microsatellite stable APC mutation-negative colorectal cancers

The tumor suppressor gene adenomatous polyposis coli (APC) is the initiating mutation in approximately 80% of all colorectal cancers (CRC), underscoring the importance of aberrant regulation of intracellular WNT signaling in CRC development. Recent studies have found that early-onset CRC exhibits an increased proportion of tumors lacking an APC mutation. We set out to identify mechanisms underlying APC mutation-negative (APC^mut-) CRCs. We analyzed data from The Cancer Genome Atlas to compare clinical phenotypes, somatic mutations, copy number variations, gene fusions, RNA expression, and DNA methylation profiles between APC^mut- and APC mutation-positive (APC^mut+) microsatellite stable CRCs. Transcriptionally, APC^mut- CRCs clustered into two approximately equal groups. Cluster One was associated with enhanced mitochondrial activation. Cluster Two was strikingly associated with genetic inactivation or decreased RNA expression of the WNT antagonist RNF43, increased expression of the WNT agonist RSPO3, activating mutation of BRAF, or increased methylation and decreased expression of AXIN2. APC^mut- CRCs exhibited evidence of increased immune cell infiltration, with significant correlation between M2 macrophages and RSPO3. APC^mut- CRCs comprise two groups of tumors characterized by enhanced mitochondrial activation or increased sensitivity to extracellular WNT, suggesting that they could be respectively susceptible to inhibition of these pathways.

Distinguishing colorectal adenoma from hyperplastic polyp by WNT2 expression

BACKGROUND

Colorectal adenoma (CRA) is a classical premalignant lesion, with high incidence and mainly coexisting with hyperplastic polyp (HPP). Hence, this study aimed to distinguish CRA from HPP by molecular expression profiling and advance the prevention of CRA and its malignance.

METHODS

CRA and paired HPP biopsies were collected by endoscopy. Through RNA-sequencing (RNA-seq), the differentially expressed genes (DEGs) were obtained. Functional enrichment analysis was performed based on the DEGs. The STRING database and Cytoscape were used to construct the protein-protein interaction (PPI) network and perform module analysis. Hub genes were validated by real-time quantitative PCR (RT-qPCR) and immunohistochemistry. The ROC curve was drawn to establish the specificity of the hub genes.

RESULTS

485 significant DEGs were identified including 133 up-regulated and 352 down-regulated. The top 10 up-regulated genes were DLX5, MMP10, TAC1, ACAN, TAS2R38, WNT2, PHYHIPL, DKK4, DUSP27, and ABCA12. The top 10 down-regulated genes were SFRP2, CHRDL1, KBTBD12, RERGL, DPP10, CLCA4, GREM2, TMIGD1, FEV, and OTOP3. Wnt signaling pathway and extracellular matrix (ECM) were up-regulated in CRA. Three hub genes including WNT2, WNT5A, and SFRP1 were filtered out via Cytoscape. Further RT-qPCR and immunohistochemistry confirmed that WNT2 was highly expressed in CRA. The area under the ROC curve (AUC) at 0.98 indicated the expression level of WNT2 as a candidate to differ CRA from HPP.

CONCLUSION

Our study suggests Wnt signaling pathway and ECM are enriched in CRA, and WNT2 may be used as a novel biomarker for distinguishing CRA from HPP and preventing the malignance of CRA.

The Frontiers of Serrated Polyps

The serrated pathway of carcinogenesis has been the subject of intense investigation over the past 2 decades, but many gaps in our understanding still need to be resolved. Serrated polyp precursors include hyperplastic polyps, sessile serrated polyps, and traditional serrated adenomas. These are considered discrete entities, but there is emerging molecular data to suggest that they may be more closely related to each other than currently believed. The recent US Multi-Society Task Force surveillance guidelines for patients with serrated polyps are admittedly based on low quality evidence. In this brief review, we discuss the limitations in endoscopic detection and pathologic interpretation of serrated polyps and the implications of these diagnostic difficulties on risk prediction and postpolypectomy surveillance recommendations.

The tweety Gene Family: From Embryo to Disease

The tweety genes encode gated chloride channels that are found in animals, plants, and even simple eukaryotes, signifying their deep evolutionary origin. In vertebrates, the tweety gene family is highly conserved and consists of three members—ttyh1, ttyh2, and ttyh3—that are important for the regulation of cell volume. While research has elucidated potential physiological functions of ttyh1 in neural stem cell maintenance, proliferation, and filopodia formation during neural development, the roles of ttyh2 and ttyh3 are less characterized, though their expression patterns during embryonic and fetal development suggest potential roles in the development of a wide range of tissues including a role in the immune system in response to pathogen-associated molecules. Additionally, members of the tweety gene family have been implicated in various pathologies including cancers, particularly pediatric brain tumors, and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Here, we review the current state of research using information from published articles and open-source databases on the tweety gene family with regard to its structure, evolution, expression during development and adulthood, biochemical and cellular functions, and role in human disease. We also identify promising areas for further research to advance our understanding of this important, yet still understudied, family of genes.

An "expressionistic" look at serrated precancerous colorectal lesions

Background

Approximately 60% of colorectal cancer (CRC) precursor lesions are the genuinely-dysplastic conventional adenomas (cADNs). The others include hyperplastic polyps (HPs), sessile serrated lesions (SSL), and traditional serrated adenomas (TSAs), subtypes of a class of lesions collectively referred to as “serrated.” Endoscopic and histologic differentiation between cADNs and serrated lesions, and between serrated lesion subtypes can be difficult.

Methods

We used in situ hybridization to verify the expression patterns in CRC precursors of 21 RNA molecules that appear to be promising differentiation markers on the basis of previous RNA sequencing studies.

Results

SSLs could be clearly differentiated from cADNs by the expression patterns of 9 of the 12 RNAs tested for this purpose (VSIG1, ANXA10, ACHE, SEMG1, AQP5, LINC00520, ZIC5/2, FOXD1, NKD1). Expression patterns of all 9 in HPs were similar to those in SSLs. Nine putatively HP-specific RNAs were also investigated, but none could be confirmed as such: most (e.g., HOXD13 and HOXB13), proved instead to be markers of the normal mucosa in the distal colon and rectum, where most HPs arise. TSAs displayed mixed staining patterns reflecting the presence of serrated and dysplastic glands in the same lesion.

Conclusions

Using a robust in situ hybridization protocol, we identified promising tissue-staining markers that, if validated in larger series of lesions, could facilitate more precise histologic classification of CRC precursors and, consequently, more tailored clinical follow-up of their carriers. Our findings should also fuel functional studies on the pathogenic significance of specific gene expression alterations in the initiation and evolution of CRC precursor subtypes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-020-01064-1.

Identification of an alternative splicing signature as an independent factor in colon cancer

BACKGROUND

Colon cancer is a common malignant tumor with a poor prognosis. Abnormal alternative splicing (AS) events played a part in the occurrence and metastasis of the tumor. We aimed to develop a survival-associated AS signature in colon cancer.

METHODS

The Percent Spliced In values of AS events were available in The Cancer Genome Atlas (TCGA) SpliceSeq database. Univariate Cox analysis was carried out to detect the prognosis-related AS events. We created a predictive model on account of the survival-associated AS events, which was further validated with a training-testing group design. Kaplan-Meier analysis was applied to assess patient survival. The area under curve (AUC) of receiver operating characteristic (ROC) was performed to evaluate the predictive values of this model. Meanwhile, the clinical relevance of the signature and its regulatory relationship with splicing factors (SFs) were also evaluated.

RESULTS

In total, 2132 survival-related AS events were identified from colon cancer samples. We developed an eleven-AS signature, in which the 5-year AUC value was 0.911. Meanwhile, the AUC values at five years were 0.782 and 0.855 in the testing and entire cohort, respectively. Multivariate Cox regression displayed that the T category and the risk score of the signature were independent risk factors of colon cancer survival. Also, we constructed an SFs-AS network based on 11 SFs and 48 AS events.

CONCLUSIONS

We identified an eleven-AS signature of colon cancer. This signature could be treated as an independent prognostic factor.

Molecular Biomarkers of Sessile Serrated Adenoma/Polyps

OBJECTIVES:

Sessile serrated adenoma/polyps (SSA/Ps) contribute up to 30% of all colon cancers. There is considerable histological overlap between SSA/Ps and hyperplastic polyps. Inadequate consensus exists among pathologists, and no molecular biomarkers exist to differentiate these lesions with high accuracy. Lack of reliable diagnosis adversely affects clinical care. We previously defined a novel 7-gene panel by RNA sequencing that differentiates SSA/Ps from hyperplastic polyps. Here, we use the 7-gene panel as a molecular approach to differentiate SSA/Ps and HPs with higher sensitivity and specificity in a large sample set from a tertiary health care center.

METHODS:

Reverse transcription quantitative polymerase chain reaction of the 7-gene panel was performed on 223 formalin-fixed, paraffin-embedded serrated polyp and normal colon samples. We compare the sensitivity and specificity of the 7-gene panel with the BRAF and KRAS mutation incidence in differentiating SSA/Ps and HPs. We also evaluate the clinical data of patients with SSA/Ps showing high and low expression of the gene panel.

RESULTS:

The 7-gene RNA expression panel differentiates SSA/Ps and HPs with 89.2% sensitivity and 88.4% specificity. The gene panel outperforms BRAF mutation in identification of SSA/Ps. Clinical data suggest that expression of the 7-gene panel correlates with the development of SSA/Ps in the future.

DISCUSSION:

This study describes a novel 7-gene panel that identifies SSA/Ps with improved accuracy. Our data show that RNA markers of SSA/Ps advance the distinction of serrated lesions and contribute to the study of the serrated pathway to colon cancer.

Agrin in the Muscularis Mucosa Serves as a Biomarker Distinguishing Hyperplastic Polyps from Sessile Serrated Lesions

PURPOSE

Sessile serrated lesions (SSL) are precursors to colon carcinoma, and their distinction from other polyps, in particular hyperplastic polyps (HP), presents significant diagnostic challenges. We evaluated expression patterns in colonic polyps of previously identified colon carcinoma-associated extracellular matrix (ECM) proteins to identify markers distinguishing SSLs from other polyps.

EXPERIMENTAL DESIGN

Gene-expression analyses of ECM proteins were performed using publicly available data on preneoplastic colonic polyps. In parallel, we evaluated by IHC the expression of agrin (AGRN) in over 400 colonic polyps, including HP, SSL with and without dysplasia, traditional serrated adenomas (TSA), and tubular adenomas (TA), and compared the consistency of standard histologic diagnosis of SSLs by experienced gastrointestinal pathologists with that of AGRN IHC.

RESULTS

Differential gene expression analysis and IHC identified AGRN, serine peptidase inhibitor (SERPINE2), and TIMP metallopeptidase inhibitor 1 (TIMP1) elevated in SSLs and HPs but decreased in TAs and absent in normal colon. AGRN-positive basal laminae were noted in all TA, TSA, HP, and SSL in distinguishable patterns, whereas other polyps and normal mucosa were negative. SSL with or without dysplasia consistently showed IHC staining for AGRN in the muscularis mucosae, which was absent in HP, TSA, TA, and other polyps. In contrast, histologic evaluation showed only weak interobserver agreement (kappa value = 0.493) in distinguishing SSLs.

CONCLUSIONS

Muscularis mucosae-based AGRN immunostaining is a novel biomarker to distinguish SSL from HP, TSA, and TA, with a specificity of 97.1% and sensitivity of 98.9% and can assist in diagnosis of morphologically challenging colonic polyps.

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

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 β-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.

Proteome analysis of formalin-fixed paraffin-embedded colorectal adenomas reveals the heterogeneous nature of traditional serrated adenomas compared to other colorectal adenomas

Traditional serrated adenoma (TSA) remains the least understood of all the colorectal adenomas, although these lesions have been associated with a significant cancer risk, twice that of the conventional adenoma (CAD) and of the sessile serrated adenoma (SSA/P). This study was performed to investigate the proteomic profiles of the different colorectal adenomas to better understand the pathogenesis of TSA. We performed a global quantitative proteome analysis using the label-free quantification (LFQ) method on 44 colorectal adenoma (12 TSAs, 15 CADs, and 17 SSA/Ps) and 17 normal colonic mucosa samples, archived as formalin-fixed paraffin-embedded blocks. Unsupervised consensus hierarchical clustering applied to the whole proteomic profile of the 44 colorectal adenomas identified four subtypes: C1 and C2 were well-individualized clusters composed of all the CADs (15/15) and most of the SSA/Ps (13/17), respectively. This is consistent with the fact that CADs and SSA/Ps are homogeneous and distinct colorectal adenoma entities. In contrast, TSAs were subdivided into C3 and C4 clusters, consistent with the more heterogeneous entity of TSA at the morphologic and molecular levels. Comparison of the proteome expression profile between the adenoma subtypes and normal colonic mucosa further confirmed the heterogeneous nature of TSAs, which overlapped either on CADs or SSA/Ps, whereas CADs and SSAs formed homogeneous and distinct entities. Furthermore, we identified LEFTY1 a new potential marker for TSAs that may be relevant for the pathogenesis of TSA. LEFTY1 is an inhibitor of the Nodal/TGFβ pathway, which we found to be one of the most overexpressed proteins specifically in TSAs. This finding was confirmed by immunohistochemistry. Our study confirms that CADs and SSA/Ps form homogeneous and distinct colorectal adenoma entities, whereas TSAs are a heterogeneous entity and may arise from either SSA/Ps or from normal mucosa evolving through a process related to the CAD pathway. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Molecular Hallmarks of the Serrated Pathway in Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. It includes different subtypes that differ in their clinical and prognostic features. In the past decade, in addition to the conventional adenoma-carcinoma model, an alternative multistep mechanism of carcinogenesis, namely the “serrated pathway”, has been described. Approximately, 15 to 30% of all CRCs arise from neoplastic serrated polyps, a heterogeneous group of lesions that are histologically classified into three morphologic categories: hyperplastic polyps, sessile serrated adenomas/polyps, and the traditional serrated adenomas/polyps. Serrated polyps are characterized by genetic (BRAF or KRAS mutations) and epigenetic (CpG island methylator phenotype (CIMP)) alterations that cooperate to initiate and drive malignant transformation from normal colon mucosa to polyps, and then to CRC. The high heterogeneity of the serrated lesions renders their diagnostic and pathological interpretation difficult. Hence, novel genetic and epigenetic biomarkers are required for better classification and management of CRCs. To date, several molecular alterations have been associated with the serrated polyp-CRC sequence. In addition, the gut microbiota is emerging as a contributor to/modulator of the serrated pathway. This review summarizes the state of the art of the genetic, epigenetic and microbiota signatures associated with serrated CRCs, together with their clinical implications.

Can the rate and location of sessile serrated polyps be part of colorectal Cancer disparity in African Americans?

BACKGROUND

Up to 30% of colorectal cancers develop through the serrated pathway. African Americans (AAs) suffer a disproportionate burden of colorectal cancer. The aim of this study was to evaluate clinicopathological features of AA patients diagnosed with sessile serrated polyps (SSPs).

METHODS

We conducted a retrospective study of all colonoscopies (n = 12,085) performed at Howard University Hospital, from January 1st, 2010 to December 31st, 2015, of which 83% were in AA patients, (n = 10,027). Among AAs, pathology reports confirmed 4070 patients with polyps including 252 with SSPs. Demographic and clinical variables (i.e. sex, age, BMI, anatomic location, clinical symptoms, polyp size, and clinical indications were collected at colonoscopy.

RESULTS

In the AA population, the median age was 56 with interquartile range (IQR) of 51 to 62 years, 54% were female, and 48% had a BMI > 30. The most common reason for colonoscopy was screening (53%), whereas the prevalent reasons for diagnostic colonoscopies were changes in bowel habits (18%) and gastrointestinal bleeding (17%). The total number of SSPs among the 252 AA (diagnosed with SSPs) was 338. Of these, 9% (n = 29/338) had some degree of cytological dysplasia, primarily in the ascending colon (n = 6/42, 14%), Transverse colon (n = 2/16, 13%) and rectosigmoid (n = 19/233, 8%). About 24% of patients had more than 2 polyps. Most patients (76%) had distal SSPs (rectal and rectosigmoid), in comparison to 14% of proximal polyps and 10% of bilateral locations. Median SSA/P size for all locations was 0.6 cm.

CONCLUSION

The prevalence of SSPs accounts for 6% of all polyps in AA patients and was diagnosed in 2.5% of all colonoscopies (n = 252/10,027), which is higher than Caucasians in the US. SSPs were predominantly located in the left side, as compared to published literature showing the predominance in the right side of the colon. Screening of CRC will have the chance to detect high risk SSA/P in this population.

Diagnostic Accuracy of FOBT and Colorectal Cancer Genetic Testing: A Systematic Review & Meta-Analysis

Introduction:

Colorectal cancer (CRC) is the second leading cause of cancer related death in the world after lung cancer. Early detection of CRC leads to improvement in cancer survival rate. In recent years, efforts have been made to discover a non-invasive screening marker of higher sensitivity and specificity. Fecal occult blood testing (FOBT) and genetic testing become alternative modalities to screen CRC in the population other than colonoscopy. The aim of this systematic review and meta-analysis is to determine the diagnostic accuracy, sensitivity and specificity of FOBT and genetic testing as screening tools in colorectal cancer.

Methods:

A literature search of PubMed, ScienceDirect, and Scopus was carried out. The search strategy was restricted to human subjects and studies are published in English. Data on sensitivity and specificity were extracted and pooled. Heterogeneity was assumed at significance level of p < 0.10 and was tested by chi squared. Degree of heterogeneity was quantified using the I² statistic, and values of less than 25% is considered as homogenous. All analyses were performed using the software Meta-Disc.

Results:

A total of eleven studies were suitable for data synthesis and analysis. Five studies were analyzed for the accuracy of genetic testing, the pooled estimate for sensitivity and specificity were 71% (95% CI: 66, 75%) and 95% (95% CI: 93, 97%) respectively. Another group of studies which had been evaluated for the accuracy of FOBT, the pooled sensitivity was 31% (95% CI: 25, 38%) while the pooled specificity was 87% (95% CI: 86, 89%).

Conclusions:

FOBTs is recommended to use as population-based screening tools for colorectal cancer while genetic testing should be focusing on patients with moderate and high risk individuals.

Degree of Tissue Differentiation Dictates Susceptibility to BRAF-Driven Colorectal Cancer

Oncogenic mutations in BRAF are believed to initiate serrated colorectal cancers; however, the mechanisms of BRAF-driven colon cancer are unclear. We find that oncogenic BRAF paradoxically suppresses stem cell renewal and instead promotes differentiation. Correspondingly, tumor formation is inefficient in BRAF-driven mouse models of colon cancer. By reducing levels of differentiation via genetic manipulation of either of two distinct differentiation-promoting factors (Smad4 or Cdx2), stem cell activity is restored in BRAF^V600E intestines, and the oncogenic capacity of BRAF^V600E is amplified. In human patients, we observe that reduced levels of differentiation in normal tissue is associated with increased susceptibility to serrated colon tumors. Together, these findings help resolve the conditions necessary for BRAF-driven colon cancer initiation. Additionally, our results predict that genetic and/or environmental factors that reduce tissue differentiation will increase susceptibility to serrated colon cancer. These findings offer an opportunity to identify susceptible individuals by assessing their tissue-differentiation status.

The proto CpG island methylator phenotype of sessile serrated adenomas/polyps

Sessile serrated adenomas/polyps (SSA/Ps) are the putative precursors of the ~20% of colon cancers with the CpG island methylator phenotype (CIMP). To investigate the epigenetic phenotype of these precancers, we prospectively collected fresh-tissue samples of 17 SSA/Ps and 15 conventional adenomas (cADNs), each with a matched sample of normal mucosa. Their DNA was subjected to bisulfite next-generation sequencing to assess methylation levels at ~2.7 million CpGs located predominantly in gene regulatory regions and spanning 80.5Mb; RNA was sequenced to define the samples' transcriptomes. Compared with normal mucosa, SSA/Ps and cADNs exhibited markedly remodeled methylomes. In cADNs, hypomethylated regions were far more numerous (18,417 vs 4288 in SSA/Ps) and rarely affected CpG islands/shores. SSA/Ps seemed to have escaped this wave of demethylation. Cytosine hypermethylation in SSA/Ps was more pervasive (hypermethylated regions: 22,147 vs 15,965 in cADNs; hypermethylated genes: 4938 vs 3443 in cADNs) and more extensive (region for region), and it occurred mainly within CpG islands and shores. Given its resemblance to the CIMP typical of SSA/Ps' putative descendant colon cancers, we refer to the SSA/P methylation phenotype as proto-CIMP. Verification studies of six hypermethylated regions in an independent series of precancers demonstrated DNA methylation markers' high potential for predicting the diagnosis of SSA/Ps and cADNs. Surprisingly, proto-CIMP in SSA/Ps was associated with upregulated gene expression; downregulation was more common in cADNs. In conclusion, the epigenetic landscape of SSA/Ps differs markedly from that of cADNs. These differences are a potentially rich source of novel tissue-based and noninvasive biomarkers.

Small RNA sequencing of sessile serrated polyps identifies microRNA profile associated with colon cancer

Sessile serrated adenoma/polyps (SSA/Ps) of the colon account for 20-30% of all colon cancers. Small non-coding RNAs, including microRNAs (miRNAs), may function as oncogenes or tumor suppressor genes involved in cancer development. Small RNA sequencing (RNA-seq) was used to characterize miRNA profiles in SSA/Ps, hyperplastic polyps (HPs), adenomatous polyps and paired uninvolved colon. Our 108 small RNA-seq samples' results were compared to small RNA-seq data from 212 colon cancers from the Cancer Genome Atlas. Twenty-three and six miRNAs were differentially expressed in SSA/Ps compared to paired uninvolved colon and HPs, respectively. Differential expression of MIR31-5p, MIR135B-5p and MIR378A-5p was confirmed by RT-qPCR. SSA/P-specific miRNAs are similarly expressed in colon cancers containing genomic aberrations described in serrated cancers. Correlation of miRNA expression with consensus molecular subtypes suggests more than one subtype is associated with the serrated neoplasia pathway. Canonical pathway analysis suggests many of these miRNAs target growth factor signaling pathways.

Colorectal premalignancy is associated with consensus molecular subtypes 1 and 2

Background

Gene expression-based profiling of colorectal cancer (CRC) can be used to identify four molecularly homogeneous consensus molecular subtype (CMS) groups with unique biologic features. However, its applicability to colorectal premalignant lesions remains unknown.

Patients and methods

We assembled the largest transcriptomic premalignancy dataset by integrating different public and proprietary cohorts of adenomatous and serrated polyps from sporadic (N = 311) and hereditary (N = 78) patient populations and carried out a comprehensive analysis of carcinogenesis pathways using the CMS random forest (RF) classifier.

Results

Overall, transcriptomic subtyping of sporadic and hereditary polyps revealed CMS2 and CMS1 subgroups as the predominant molecular subtypes in premalignancy. Pathway enrichment analysis showed that adenomatous polyps from sporadic or hereditary cases (including Lynch syndrome) displayed a CMS2-like phenotype with WNT and MYC activation, whereas hyperplastic and serrated polyps with CMS1-like phenotype harbored prominent immune activation. Rare adenomas with CMS4-like phenotype showed significant enrichment for stromal signatures along with transforming growth factor-β activation. There was a strong association of CMS1-like polyps with serrated pathology, right-sided anatomic location and BRAF mutations.

Conclusions

Based on our observations made in premalignancy, we propose a model of pathway activation associated with CMS classification in colorectal carcinogenesis. Specifically, while adenomatous polyps are largely CMS2, most hyperplastic and serrated polyps are CMS1 and may transition into other CMS groups during evolution into carcinomas. Our findings shed light on the transcriptional landscape of premalignant colonic polyps and may help guide the development of future biomarkers or preventive treatments for CRC.

Colorectal cancer: genetic abnormalities, tumor progression, tumor heterogeneity, clonal evolution and tumor-initiating cells

Colon cancer is the third most common cancer worldwide. Most colorectal cancer occurrences are sporadic, not related to genetic predisposition or family history; however, 20-30% of patients with colorectal cancer have a family history of colorectal cancer and 5% of these tumors arise in the setting of a Mendelian inheritance syndrome. In many patients, the development of a colorectal cancer is preceded by a benign neoplastic lesion: either an adenomatous polyp or a serrated polyp. Studies carried out in the last years have characterized the main molecular alterations occurring in colorectal cancers, showing that the tumor of each patient displays from two to eight driver mutations. The ensemble of molecular studies, including gene expression studies, has led to two proposed classifications of colorectal cancers, with the identification of four/five non-overlapping groups. The homeostasis of the rapidly renewing intestinal epithelium is ensured by few stem cells present at the level of the base of intestinal crypts. Various experimental evidence suggests that colorectal cancers may derive from the malignant transformation of intestinal stem cells or of intestinal cells that acquire stem cell properties following malignant transformation. Colon cancer stem cells seem to be involved in tumor chemoresistance, radioresistance and relapse.

Platform-independent gene expression signature differentiates sessile serrated adenomas/polyps and hyperplastic polyps of the colon

Background

Sessile serrated adenomas/polyps are distinguished from hyperplastic colonic polyps subjectively by their endoscopic appearance and histological morphology. However, hyperplastic and sessile serrated polyps can have overlapping morphological features resulting in sessile serrated polyps diagnosed as hyperplastic. While sessile serrated polyps can progress into colon cancer, hyperplastic polyps have virtually no risk for colon cancer. Objective measures, differentiating these types of polyps would improve cancer prevention and treatment outcome.

Methods

RNA-seq training data set and Affimetrix, Illumina testing data sets were obtained from Gene Expression Omnibus (GEO). RNA-seq single-end reads were filtered with FastX toolkit. Read mapping to the human genome, gene abundance estimation, and differential expression analysis were performed with Tophat-Cufflinks pipeline. Background correction, normalization, and probe summarization steps for Affimetrix arrays were performed using the robust multi-array method (RMA). For Illumina arrays, log₂-scale expression data was obtained from GEO. Pathway analysis was implemented using Bioconductor package GSAR. To build a platform-independent molecular classifier that accurately differentiates sessile serrated and hyperplastic polyps we developed a new feature selection step. We also developed a simple procedure to classify new samples as either sessile serrated or hyperplastic with a class probability assigned to the decision, estimated using Cantelli’s inequality.

Results

The classifier trained on RNA-seq data and tested on two independent microarray data sets resulted in zero and three errors. The classifier was further tested using quantitative real-time PCR expression levels of 45 blinded independent formalin-fixed paraffin-embedded specimens and was highly accurate. Pathway analyses have shown that sessile serrated polyps are distinguished from hyperplastic polyps and normal controls by: up-regulation of pathways implicated in proliferation, inflammation, cell-cell adhesion and down-regulation of serine threonine kinase signaling pathway; differential co-expression of pathways regulating cell division, protein trafficking and kinase activities.

Conclusions

Most of the differentially expressed pathways are known as hallmarks of cancer and likely to explain why sessile serrated polyps are more prone to neoplastic transformation than hyperplastic. The new molecular classifier includes 13 genes and may facilitate objective differentiation between two polyps.

Electronic supplementary material

The online version of this article (10.1186/s12920-017-0317-7) contains supplementary material, which is available to authorized users.

Exome sequencing characterizes the somatic mutation spectrum of early serrated lesions in a patient with serrated polyposis syndrome (SPS)

Background

Serrated or Hyperplastic Polyposis Syndrome (SPS, HPS) is a yet poorly defined colorectal cancer (CRC) predisposition characterised by the occurrence of multiple and/or large serrated polyps throughout the colon. A serrated polyp-CRC sequence (serrated pathway) of CRC formation has been postulated, however, to date only few molecular signatures of serrated neoplasia (BRAF, KRAS, RNF43 mutations, CpG Island Methylation, MSI) have been described in a subset of SPS patients and neither the etiology of the syndrome nor the distinct genetic alterations during tumorigenesis have been identified.

Methods

To identify somatic point mutations in potential novel candidate genes of SPS-associated lesions and the involved pathways we performed exome sequencing of eleven early serrated polyps obtained from a 41 year-old female patient with clinically confirmed SPS. For data filtering and analysis, standard pipelines were used. Somatic mutations were identified by comparison with leukocyte DNA and were validated by Sanger sequencing.

Results

The BRAF p.V600E or KRAS p.G12D mutation was identified in six polyps (~50%) and not found in polyps from the distal colon. In addition, we found seven unique rare somatic alterations of seven different genes in four serrated tumours, all of which are missense variants. The variant in ABI3BP and CATSPERB are predicted to be deleterious. No established cancer gene or candidate genes related to serrated tumorigenesis were affected.

Conclusions

Somatic mutations seem to be rare events in early hyperplastic and serrated lesions of SPS patients. Neither frequently affected genes nor enrichment of specific pathways were observed. Thus, other alterations such as non-coding variants or epigenetic changes might be the major driving force of tumour progression in SPS.

Electronic supplementary material

The online version of this article (10.1186/s13053-017-0082-9) contains supplementary material, which is available to authorized users.

A 16-gene signature predicting prognosis of patients with oral tongue squamous cell carcinoma

Background

Oral tongue squamous cell carcinoma (OTSCC) is the most common subtype of oral cancer. A predictive gene signature is necessary for prognosis of OTSCC.

Methods

Five microarray data sets of OTSCC from the Gene Expression Omnibus (GEO) and one data set from The Cancer Genome Atlas (TCGA) were obtained. Differentially expressed genes (DEGs) of GEO data sets were identified by integrated analysis. The DEGs associated with prognosis were screened in the TCGA data set by univariate survival analysis to obtain a gene signature. A risk score was calculated as the summation of weighted expression levels with coefficients by Cox analysis. The signature was used to distinguish carcinoma, estimated by receiver operator characteristic curves and the area under the curve (AUC). All were validated in the GEO and TCGA data sets.

Results

Integrated analysis of GEO data sets revealed 300 DEGs. A 16-gene signature and a risk score were developed after survival analysis. The risk score was effective to stratify patients into high-risk and low-risk groups in the TCGA data set (P < 0.001). The 16-gene signature was valid to distinguish the carcinoma from normal samples (AUC 0.872, P < 0.001).

Discussion

We identified a useful 16-gene signature for prognosis of OTSCC patients, which could be applied to clinical practice. Further studies were needed to prove the findings.

Hereditary Colorectal Polyposis and Cancer Syndromes: A Primer on Diagnosis and Management

Colorectal cancer (CRC) is the fourth most common cancer amongst men and women. Between 3 and 6% of all CRCs are attributed to well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), and several hamartomatous polyposis conditions. Identification of these patients through family history and appropriate genetic testing can provide estimates of cancer risk that inform appropriate cancer screening, surveillance and/or preventative interventions. This narrative review examines the hereditary colorectal cancer and polyposis syndromes, their genetic basis, clinical management, and evidence supporting cancer screening.

The Serrated Polyp Pathway: Is It Time to Alter Surveillance Guidelines?

PURPOSE OF REVIEW

In this manuscript, we review current surveillance guidelines for serrated polyps (SPs) and discuss how recent studies inform the selection of appropriate surveillance intervals for patients with SPs.

RECENT FINDINGS

Large and/or proximal SPs, particularly sessile serrated polyps (SSPs), are associated with increased risk of both synchronous and metachronous neoplasia, including advanced adenomas and colorectal cancer (CRC). Persons harboring multiple SSPs or dysplastic SSPs are at the highest risk. Moreover, a high percentage of large and/or proximal SPs are reclassified as SSPs when read by trained gastrointestinal pathologists, even if they were originally reported as hyperplastic polyps. These findings support the adoption of surveillance guidelines that prescribe closer surveillance of large and/or proximal SPs, regardless of subtype. SSPs remain a challenge to reliably identify, resect, and diagnose via histology. The increased risk of future neoplasia in patients with SSPs is likely driven by a combination of underdetection, inadequate removal, misclassification, and biology. Until further evidence emerges, we support guidelines that recommend close surveillance of patients with a history of large and/or proximal SPs and SSPs specifically in order to mitigate the threat of interval CRC.

Hereditary Colorectal Cancer Syndromes

Awareness of hereditary colorectal cancer syndromes is important to facilitate their identification because affected patients are at increased risk for early onset, synchronous, and metachronous colorectal malignancies, and certain extracolonic malignancies depending on the syndrome. Identification of an affected individual allows for screening and early interventions for patients and their at-risk kindred. Genetic counseling and testing is important to the care of these patients. As knowledge of the genetic basis of these syndromes grows, unique genotype-phenotype profiles allow clinicians to tailor surveillance and treatment strategies based on individual risk.

Colonic organoids derived from human induced pluripotent stem cells for modeling colorectal cancer and drug testing

With the goal of modeling human disease of the large intestine, we sought to develop an effective protocol for deriving colonic organoids (COs) from differentiated human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs). Extensive gene and immunohistochemical profiling confirmed that the derived COs represent colon rather than small intestine, containing stem cells, transit-amplifying cells, and the expected spectrum of differentiated cells, including goblet and endocrine cells. We applied this strategy to iPSCs derived from patients with familial adenomatous polyposis (FAP-iPSCs) harboring germline mutations in the WNT-signaling-pathway-regulator gene encoding APC, and we generated COs that exhibit enhanced WNT activity and increased epithelial cell proliferation, which we used as a platform for drug testing. Two potential compounds, XAV939 and rapamycin, decreased proliferation in FAP-COs, but also affected cell proliferation in wild-type COs, which thus limits their therapeutic application. By contrast, we found that geneticin, a ribosome-binding antibiotic with translational 'read-through' activity, efficiently targeted abnormal WNT activity and restored normal proliferation specifically in APC-mutant FAP-COs. These studies provide an efficient strategy for deriving human COs, which can be used in disease modeling and drug discovery for colorectal disease.

Sessile Serrated Polyps and Colon Cancer Prevention

Evidence suggests that up to one fifth of colorectal carcinomas develop from serrated polyps, named for their pattern of colonic crypts, and include the sessile serrated adenoma/polyp (SSA/P) that has malignant potential. SSA/Ps are typically located in the proximal colon and have molecular features of hypermethylation of CpG islands in gene promoters and activating point mutations (V600E) in the BRAF oncogene. Both of these features are seen in sporadic colorectal carcinomas with microsatellite instability (MSI) which is potentially consistent with an origin of these cancers from precursor SSA/Ps. Dysplasia is detected in a subset of SSA/Ps with a high risk of progression to carcinoma. An uncommon serrated polyp is the traditional serrated adenoma that is typically found in the left colon, has a tubulovillous architecture, and frequently harbors mutant KRAS To date, the epidemiology of these serrated lesions is poorly understood, and limited observational data suggest a potential chemopreventive benefit of nonsteroidal anti-inflammatory drugs. The current primary strategy to reduce the risk of colorectal carcinoma from serrated polyps is to enhance their detection at colonoscopy and to ensure their complete removal. This review provides insight into the epidemiologic, clinical, histopathologic, and molecular features of serrated polyps and includes data on their endoscopic detection and chemoprevention. Cancer Prev Res; 10(5); 270-8. ©2017 AACR.

MCM2 expression in serrated polyps demonstrates aberrant cellular proliferation

In normal colonic epithelium, the proliferative zone is limited to the lower half of the colonic crypt. Evaluating the changes in the colonic epithelial proliferation can be useful in understanding pathophysiology of various diseases. Our aim was to investigate the proliferative compartment of serrated polyps (SPs) using MCM2, a protein involved in DNA replication, and assess for changes along the SP spectrum. Immunohistochemistry was performed on serrated polyps (16 microvesicular-type hyperplastic polyps (HP), 58 sessile serrated adenomas (SSA), 7 SSAs with dysplasia) and 6 sections of normal colon using anti-MCM2 antibody. Multiple sections of normal colon showed the following pattern for MCM2 and Ki-67 staining: positive nuclear staining of the lower half of the colonic crypts and/or slightly expanded to the lower two-thirds of the crypt. By MCM2, SPs show expansion of the proliferative compartments; 81.3% of HPs and 100% of SSAs showed some degree of full crypt MCM2 staining. SSAs with dysplasia showed consistent diffuse polyp staining. Aberrant staining in adjacent normal mucosa was also seen in SSAs with dysplasia and in a subset of non-dysplastic SSAs. By using MCM2, we show that serrated polyps exhibit changes in proliferation during progression along the pathway. HPs and SSAs show a similar highly proliferative profile. Aberrant proliferative cell staining patterns in adjacent normal colonic mucosa as seen in SSAs with dysplasia and a subset of SSAs suggest a field effect phenomenon. This indicates that changes in the colonic micro-environment may promote adenoma morphogenesis and predisposition to malignancy.

Olfactomedin 1 negatively regulates NF-κB signalling and suppresses the growth and metastasis of colorectal cancer cells

Uncontrolled growth and distant metastasis are hallmarks of colorectal cancer (CRC), but the mechanisms are poorly understood. Olfactomedin 1 (OLFM1), a member of the olfactomedin domain-containing protein family, plays an important role in the development of neurogenic tissues. Recently, OLFM1 deregulation was frequently observed in several cancers, and it was induced in colon cell lines after treatment with the demethylating agent 5-aza-2'-deoxycytidine. However, the function of OLFM1 in CRC remains unknown. In this study, we reanalysed published microarray data and found that OLFM1 was significantly down-regulated in primary CRC samples compared to adjacent non-cancerous tissues. The results of immunohistochemistry indicated that decreased OLFM1 expression was significantly associated with lymph node status (p = 0.023), distant metastasis (p < 0.001), and AJCC/TNM stage (p = 0.013), and CRC patients with low OLFM1 expression had consistently poor overall survival (OS; p < 0.001) and progression-free survival (PFS; p < 0.001). Further analysis demonstrated that OLFM1 was epigenetically silenced in CRC tissues and cell lines via promoter hypermethylation. Overexpression and knockdown of OLFM1 attenuated and increased, respectively, CRC cells' proliferation, migration, and invasion in vitro and metastasis to the lung and liver in vivo. Mechanistically, the promotion of growth and metastasis of CRC cells by silencing of OLFM1 was associated with the activation of the non-canonical NF-κB signalling pathway. OLFM1 interacted with NF-κB-inducing kinase (NIK; MAP3K14) and repressed the phosphorylation of its downstream substrate Ikappa B kinase alpha (IKKα). OLFM1 expression was negatively correlated with the phosphorylation level of IKKα in CRC tissue samples. Knockdown of NIK impaired the ability of OLFM1 to repress NF-κB signalling, cell growth or migration. Thus, OLFM1 may be a valuable biomarker and therapeutic target for CRC patients. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.