Serrated adenoma of the colorectum is a recently proposed entity characterized by a saw-toothed structure of hyperplastic polyp and cytologic atypia of tubular adenoma. To clarify the role of apoptosis in morphogenesis of serrated adenoma, we investigated apoptotic indices and expression of apoptosis-related antigens in the tumor cells. Thirty-eight serrated adenomas were examined by the nick-end DNA labeling method and immunostained for CD95 (Fas), bcl-2, bax, and p53. Thirty-seven hyperplastic polyps, 48 tubular adenomas, and 16 sections containing normal colonic mucosa were similarly examined for comparison. The apoptotic indices in the upper and middle zones of the crypts of serrated adenomas and hyperplastic polyps were lower than those of normal colon mucosa and tubular adenomas with statistically significant differences. The CD95 expression was diffusely observed throughout the epithelium of normal crypts and tubular adenomas, whereas it was reduced in serrated adenomas and hyperplastic polyps. The bcl-2 expression was confined to the basal crypts in the latter two lesions but was diffuse throughout the neoplastic epithelium in tubular adenomas. The bax expression was increased in serrated adenomas and tubular adenomas but was decreased in hyperplastic polyps. Overexpression of p53 protein was observed in 50% of serrated adenomas, none of hyperplastic polyps, and 14% of tubular adenomas. These findings suggest that inhibition of apoptosis is caused by reduced CD95 expression in serrated adenomas and hyperplastic polyps, which may induce the characteristic saw-toothed structure in these lesions. Based on the similarities and differences between serrated adenoma and hyperplastic polyp observed in the present study, a progression from the latter to the former lesion may be postulated.
"Because apoptosis is a crucial event in serrated tumorigenesis  and AURKA overexpression enhances cell survival , we determined the levels of apoptosis in our series of serrated lesions. Terminal deoxynucleotidyl transferase– mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay was used to evaluate the percentage of apoptotic cells (In Situ Cell Death Detection Kit, TMR red; Roche, Basel, CH). "
[Show abstract][Hide abstract] ABSTRACT: A crucial role for Aurora Kinase A (AURKA) gene has been demonstrated in the advanced steps of colorectal tumor progression. Little is known, however, about its role in the early phases of the adenoma-carcinoma sequence. Moreover, no data are currently available concerning AURKA involvement in the serrated tumorigenesis. Fluorescence in situ hybridization analysis and immunohistochemistry were used to assess gene copy number and protein expression in 40 colorectal adenomas, 20 cancerized adenomas, and 20 serrated polyps. An increased copy number was found either in adenomatous tissue or in early cancer in the vast majority of cancerized adenomas, but only in 5% of adenomas (P < .001). Protein expression strictly paralleled fluorescence in situ hybridization results. No changes in the gene copy number were observed in serrated polyps, regardless of their histotype and the presence of dysplasia, even if high percentages of immunostained cells were detected in all the subgroups. AURKA gene is associated with progressive colorectal adenomas but is uninvolved in the development of nonprogressive adenomas. The diploid status of the gene is maintained along the progression of serrated neoplasia. AURKA protein expression in serrated polyps is uncoupled from gene status and is likely to reflect apoptotic dysregulation.
Human pathology 12/2014; 46(3). DOI:10.1016/j.humpath.2014.11.016 · 2.77 Impact Factor
"It has also been found that B-Raf mutations are prevalent in precursor lesions which denote that B-Raf mutations are a preliminary step in the pathway to these types of colorectal carcinomas (Cantwell-Dorris et al., 2011; Dong et al., 2005; Park et al., 2003; Yang et al., 2004). Mutant B-Raf CpG island methylation phenotype (CIMP) tumours often show serrated morphology which is believed to be a consequence of inhibition of apoptosis (Tateyama et al., 2002). It has been shown that if B-Raf is over expressed, it can stop apoptosis through a postmitochondrial regulation of apoptosis (Erhardt et al., 1999). "
[Show abstract][Hide abstract] ABSTRACT: B-Raf is one of the more commonly mutated proto-oncogenes implicated in the development of cancers. In this review, we consider the mechanisms and clinical impacts of B-Raf mutations in cancer and discuss the implications for the patient in melanoma, thyroid cancer and colorectal cancer, where B-Raf mutations are particularly common.
[Show abstract][Hide abstract] ABSTRACT: DNA microarray technology has in a decade been rapidly adopted by biomedical researchers and emerged as a very prominent research tool. In this study, microarray technology, together with supporting methods, was utilized in studies of human cancer. The study focused on two types of cancer, a hereditary syndrome called Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC) and on colorectal cancer (CRC). HLRCC is a disease caused by mutations in the Krebs cycle gene fumarase, where some of the patients develop an aggressive and early-onset renal cancer or uterine leiomyosarcoma. CRC is one of the leading causes of death in the Western world. In the first study, yeast models with fumarase mutations were subjected to microarray profiling and functional experiments to reveal changes caused by two different fumarase mutations and to find potential candidate genes for the renal cancer observed in some of the HLRCC patients. No significant differences in fumarase gene or protein expressions or in enzyme activities were observed. This indicated that modifying genes, rather than genotype-phenotype effects, play a role in the formation of the malign tumors. In the second study, Dukes' C stage colorectal tumors with good and bad prognosis were studied using microarray profiling, and a molecular signature separating these two groups with differing prognoses was identified. The study showed that gene expression profiling of surgical samples can predict the recurrence of Dukes' C patients. In the third study, serrated colorectal carcinomas, which differ morphologically from conventional colorectal carcinomas, were distinguished from each other using expression microarrays. The separation by unsupervised clustering indicated that serrated tumors differ biologically from conventional ones. Statistical analyses were used to identify key genes with differential expression between these two tumor types and the results were further validated by immunohistochemical analyses. A key gene, EPHB2, revealed by the expression data analysis of serrated CRC, was further characterized in the last two studies to find out more about the relevance of this gene to colorectal tumorigenesis. Germline mutations in EPHB2 were found in few CRC patients, but did not appear to be a major contributor in CRC susceptibility. Aberrant promoter hypermethylation and frameshift mutations in a repetitive track of the gene were, however, found to be frequent mechanisms of EPHB2 inactivation in CRC. In general, it was observed that the use of combined research methods greatly enhance the power of microarray studies, and enable focusing of the analyses. Although the technology is presently used primarily in basic research, clinical applications are foreseeable and slowly emerging. TKK dissertations, ISSN 1795-4584; 40
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