Traditional serrated adenoma-like lesions in patients with inflammatory bowel disease:

Patients with inflammatory bowel disease (IBD) have an increased risk of colorectal carcinoma. The significance of serrated lesions resembling traditional serrated adenoma (TSA) in IBD patients is unclear. In this retrospective study, we analyzed 52 TSA-like lesions arising in 30 IBD patients and diagnosed in colectomy or endoscopic specimens. The 27 colectomy lesions presented predominantly as ill-defined areas with granular appearance, with a median size of 15 mm, located throughout the large bowel and associated with synchronous advanced colorectal lesions in 58%. Low-grade serrated dysplasia was present in 56%, high-grade serrated dysplasia in 37%, and TSA-type cytology in 7%. Increased Ki-67 immunostaining and abnormal p53 expression were identified in 96% and 48%, respectively; 74% had a KRAS mutation, and 4% had a BRAF mutation. Endoscopically resectable TSA-like lesions were all discrete polypoid lesions, smaller in size (median 9 mm), predominantly in the distal large bowel, with an adjacent precursor polyp in 24%, and associated with synchronous and metachronous advanced colorectal lesions in 6%. Most (92%) show TSA-type cytology. p53 overexpression was present in 4%, KRAS mutation in 41%, and BRAF mutation in 32%. None of the 52 TSA-like lesions demonstrated loss of MLH1 or SATB2 expression by immunohistochemistry. On follow-up, 4 patients were diagnosed with colorectal carcinoma or high-grade adenomatous IBD-associated dysplasia. None of the patients with lesions showing TSA-type cytology only developed an advanced lesion. Our findings suggest that some TSA-like lesions, essentially from colectomy, may represent a form of IBD-associated dysplasia associated with an increased risk of advanced neoplasia

Aspirin reduces the incidence of metastasis in a pre-clinical study of Braf mutant serrated colorectal neoplasia

Background: Aspirin reduces the incidence of conventional adenomas driven by APC mutation and thus colorectal cancer. The effect of aspirin on the ~20% of colorectal cancers arising via BRAF mutation is yet to be established. Methods: BrafV637E/+;Villin-CreERT2/+ mice were allocated to a control (n = 86) or aspirin-supplemented (n = 83) diet. After 14 months the incidence of murine serrated lesions, carcinoma and distant metastases were measured by histological examination. RNA was extracted from carcinomas from each cohort and subjected to sequencing to identify differentially expressed genes and molecular pathways. Results: Aspirin did not reduce the incidence of murine serrated lesions or carcinoma when compared to control, however, did significantly reduce lesion size (P = 0.0042). Among the mice with carcinoma there was a significant reduction in the incidence of distant metastasis with aspirin treatment (RR 0.69, 95% CI 0.48–0.90, P = 0.0134). Key pathways underlying metastasis of carcinoma cells include NOTCH, FGFR and PI3K signalling, were significantly downregulated in carcinomas sampled from mice on an aspirin-supplemented diet. Conclusions: Aspirin reduces the incidence of metastatic Braf mutant carcinoma, although this is not due to a reduction in primary disease. The reduction in metastasis could be attributed to a delay or prevention of molecular changes within the primary site driving metastatic growth.</p

Alterations in signaling pathways that accompany spontaneous transition to malignancy in a mouse model of BRAF mutant microsatellite stable colorectal cancer

The serrated neoplasia pathway gives rise to a distinct subgroup of colorectal cancers distinguished by the presence of mutant BRAF and the CpG Island Methylator Phenotype (CIMP). BRAF mutant CRC are commonly associated with microsatellite instability, which have an excellent clinical outcome. However, a proportion of BRAF mutant CRC retain microsatellite stability and have a dismal prognosis. The molecular drivers responsible for the development of this cancer subgroup are unknown. To address this, we established a murine model of BRAF mutant microsatellite stable CRC and comprehensively investigated the exome and transcriptome to identify molecular alterations in signaling pathways that drive malignancy. Exome sequencing of murine serrated lesions (mSL) and carcinomas identified frequent hot spot mutations within the gene encoding β-catenin (Ctnnb1). Immunohistochemical staining of β-catenin indicated that these mutations led to an increase in the presence of aberrant nuclear β-catenin that resulted in gene expression changes in targets of β-catenin transcription. Gene expression profiling identified a significant enrichment for transforming growth factor-β (TGF-β) signaling that was present in mSL and carcinomas. Early activation of TGF-β suggests that this pathway may be an early cue directing mSL to microsatellite stable carcinoma. These findings in the mouse model support the importance of alterations in WNT and TGF-β signaling during the transition of human sessile serrated lesions to malignancy

Evidence for BRAF mutation and variable levels of microsatellite instability in a syndrome of familial colorectal cancer

Background & Aims: Recently, an alternative pathway of tumorigenesis has been identified in the colorectum associated with serrated precursor lesions, variable levels of microsatellite instability (MSI-V), and driven in part by activating mutations in the BRAF proto-oncogene (V599E). Somatic BRAF mutations in hereditary nonpolyposis colon cancer (HNPCC) are rarely observed. Here, we discuss their role in the development of other familial colorectal cancers (CRC). We studied non-FAP, non-HNPCC CRC families characterized by tumors that varied in their level of MSI between individual members. Methods: A subset of tumors from a total of 55 collected (25 polyp and 30 cancers) from 43 individuals across 11 families underwent pathology review, examination for V599E using allele-specific polymerase chain reaction, and for methylation of the MINT31 CpG island. Results: All MSI-V families met the current revised Bethesda Guidelines and 6 of 11 (55%) met the Amsterdam I criteria. V599E was observed in 12 of 19 (63%) polyps and 14 of 20 (70%) cancers (4 of 4 high MSI, 2 of 4 low MSI, and 8 of 12 stable MSI), a significant increase over HNPCC (0 of 15 or 0%), and unselected CRC (30 of 197 or 15.2%) (P < .05). Eight of the 10 (80%) cancers that underwent analysis showed hypermethylation of MINT31. CRCs showed early age at onset and were more likely to show a serrated architecture than unselected CRCs (P < .05). Conclusion: These data provide evidence that the families described here represent a syndrome of familial CRC that is distinct from HNPCC. High levels of BRAF mutation and MINT31 hypermethylation suggest an origin in the serrated pathway of CRC development