Abstract 1085: TGFBR2-dependent alterations of glycosylation in MSI colorectal cancer
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Abstract Aberrant glycosylation is a common feature of many malignancies including colorectal cancers. About 15% of colorectal cancers show the microsatellite instability (MSI) phenotype that is associated with a high frequency of biallelic frameshift mutations in the exon 3 coding mononucleotide microsatellite of the Transforming growth factor beta receptor 2 (TGFBR2) gene. If and how disruption of normal TGFBR2 signaling in these MSI colorectal cancer cells is linked to altered glycan pattern is largely unexplored. To address this issue we used the TGFBR2-deficient MSI colon carcinoma cell line HCT116 as a model system. Stable clones enabling doxycycline-inducible expression of wildtype TGFBR2 transgene were generated by recombinase-mediated cassette exchange (RMCE). In two independent clones dox-inducible expression of wildtype TGFBR2 protein and functional reconstitution of TGFBR2-mediated signal transduction as recognized by target gene regulation (SMAD7, SERPINE, c-myc) and Phospho-SMAD2 analysis was confirmed by Western blot and qRT-PCR analysis. Metabolic labeling experiments using the sialic acid precursor 3H-N-acetyl-mannosamine revealed a significant decline of 30% and hence newly synthesized sialoglycoproteins in TGFBR2 expressing cells. Therefore, our findings demonstrate that this model system can be used as a versatile tool to study TGFBR2-dependent effects. Furthermore, our data reveal a TGFBR2 gene-dependent aberrant glycosylation pattern in the MSI colon cell line HCT116. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1085. doi:1538-7445.AM2012-1085Keywords:
Microsatellite Instability
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Microsatellite Instability
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Colorectal cancer is a heterogeneous disease with multiple epigenetic alterations and different molecular features. The molecular classification is based on 2 major distinct pathways: microsatellite stable pathway and the microsatellite instability pathway. Molecular profiling of colorectal cancer provides important information regarding treatment and prognosis. Aim of the study was to assess the frequency of microsatellite instability in colon cancer and the clinicopathological characteristics of the tumors with high level of microsatellite instability (MSI-H) in our region. The secondary outcome was to assess the frequency of v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations in colon cancer.The study included 129 patients with colon cancer fit for surgery. Demographic data, clinical and pathological data, immunohistochemistry staining pattern (4 mismatch repair proteins were investigated), and BRAF gene mutations were assessed. According to microsatellite instability status by polymerase chain reaction, patients were divided into 3 groups: microsatellite stable (MSS) = 108 patients, high level of microsatellite instability (MSI-H) = 15 patients and low level of microsatellite instability (MSI-L) = 6 patients. Different clinicopathological comparisons between MSS and MSI-H patients, and between MSS and MSI-L patients were performed.Microsatellite instability was found in 16.3% patients: 11.6% had MSI-H and 4.7% had MSI-L. Significantly more patients in the MSI-H group than in the MSS group were female (P = .01) and had a family history of colon cancer (P < .001). MSI-H and MSI-L groups were associated with the ascending colon location of the tumors, were mostly type G3, T2, and stage I whereas MSS tumors were mostly G2, pT3, and stage III. Overall, BRAF mutations were identified in 18/129 patients (13.9%). BRAF mutant tumors were predominantly associated with MSI-H and MSI-L tumors. Immunohistochemistry had a sensitivity of 76% and a specificity of 89% in detecting MSI tumors and an accuracy of 87.6%.The frequency of microsatellite instability in our study was 16.3%. MSI-H is a distinct molecular phenotype of colon cancer with particular features: female gender, family history of colorectal cancer, a predilection for the ascending colon, poorly differentiated, predominantly T2, and stage I. The frequency of BRAF mutations was 13.9% and mutations were more often present in the MSI tumors.
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Widespread microsatellite instability (MSI) due to the defective DNA mismatch repair underlies the pathogenesis of the majority of hereditary non-polyposis colorectal cancer and a subset of various sporadic malignant tumors. Using 5 microsatellite markers and the criteria of MSI proposed by the National Cancer Institute (NCI) workshop, we analyzed 205 gastric adenocarcinomas for MSI. Based on the number of markers showing instability per tumor, the tumors were divided into three groups; those with two or more of the five markers displaying instability (high MSI, MSI-H), those with one of five markers displaying instability (low MSI, MSI-L), and those with no instability (microsatellite stable, MSS). Among 205 tumors, 30 (15%) were MSI-H. 15 (7%) were MSI-L, and 160 (78%) were MSS. All of the 30 MSI-H tumors demonstrated instability at BAT26, a sensitive marker for the widespread MSI, while none of the 15 MSI-L tumors did. MSI-H tumors were significantly associated with distal location and well or moderate differentiation, but MSI-H tumors were indistinguishable from MSS tumors. Bax frameshift mutations were detected in 60% of the 30 MSI-H tumors, while not in any of the 15 MSI-L tumors. These results suggest that microsatellite analysis using the criteria proposed by the NCI workshop may appropriate for gastric cancers because it unveils real differences in genotype and phenotype.
Microsatellite Instability
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Microsatellite Instability
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Exon trapping
Exon shuffling
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Microsatellite Instability
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Abstract Widespread microsatellite instability (MSI) occurs in nearly 15% of sporadic colorectal cancers. Large bowel carcinomas with high-frequency MSI (MSI-H) (instability at > or = 30% of microsatellite loci) are believed to display distinctive pathologic features and to behave less aggressively than microsatellite-stable (MSS) tumors and carcinomas with low-frequency MSI (MSI-L) (instability at < 30% of microsatellite loci). In this study we would like to show the impression of MSI on clinical condition and outcome of patients with colorectal adenocarcinoma. Methods: MSI status was evaluated in 600 large bowel adenocarcinomas using polymerase chain reaction (PCR) and sequencing. Tumors that showed instability with at least two microsatellite markers were classified as MSI-H, whereas the other tumors were classified as MSI-L (instability at one locus) or MSS (no instability). Results: MSI-H was detected in 51.6% of CRC patients. The prevalence of proximal lesions in the MSI-H group (38.7%) was higher than in the MSS group (27.4%). The percentage of moderately differentiated tumors was slightly lower in the MSI-H group (16.3%) when compared to the MSS group. Eight mutations were detected in five patients with 32 MSI-H. Conclusion: Assessment of MSI status is an essential step in discovering genetic characterizations of large bowel carcinomas and identifies a subset of tumors with distinct clinical, pathologic, and biologic features. Citation Information: Cancer Prev Res 2010;3(1 Suppl):A87.
Microsatellite Instability
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To examine the alteration and significance of the DPC4 gene in paraffin-embedded tissues of pancreatic carcinomas.Polymerase chain reaction and single-strand conformation polymorphism analysis were used to search for deletions and mutations in the DPC4 gene in 46 cases of pancreatic carcinomas.Thirteen of forty-six (28.3%) cases were found to have homozygous deletions in exon 1, 2, 3, 4, 8 and 11. One was in exon 11, one in exon 1 and 11, one in exon 2 and 3, one in exon 3 and 8, one in exon 1, 2 and 8, one in exon 2, 4 and 11, one in exon 3, 4 and 11, three in exon 3, 4 and 8, one in exon 2, 3, 4, and 8, one in exon 2, 3, 8 and 11, one in exon 2, 3, 4, 8 and 11. Intragenic mutations were found in 10 of 46 cases (21.7%). One case was in exon 1, one in exon 2, three in exon 8, four in exon 11, and one in exon 4 and 11. The total frequency of intragenic changes of DPC4 in paraffin-embedded tissues was 45.6% (21/46).Inactivation of tumor-suppressor gene DPC4 may play an important role during the tumorigenesis of pancreatic carcinomas.
Exon trapping
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Microsatellite Instability
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Colorectal cancer is the third most common cancer in males and second in females. This disease can be caused by genetic and acquired/environmental factors. Microsatellite instability (MSI) is one of the major mechanisms in colorectal cancer. This mechanism is a specific condition of genetic hyper mutability that results from incompetent DNA mismatch repair. MSI has been applied to classify different colorectal cancer subtypes. However, the effects of MSI status on gene expression are largely unknown. In our study, we integrated the gene expression profile and MSI status of all CRC samples from the TCGA database, and then categorized the CRC samples into three subgroups, namely, MSI-stable, MSI-low, and MSI-high, according to the MSI status. We applied a novel computational method based on machine learning and screened the genes specifically expressed for the different colorectal cancer subtypes. The results showed the distinct mechanisms of the different colorectal cancer subtypes with MSI status and provided the genes that may be the optimal standards to further classify the various molecular subtypes of colorectal cancer with distinct MSI status.
Microsatellite Instability
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