Monika Zazula

CDH1 gene promoter hypermethylation in gastric cancer - Relationship to Goseki grading, microsatellite instability status, and EBV invasion

Hypermethylation of the CDH1 promoter region seems to be the most common epigenetic mechanism in this gene silencing in gastric cancer. In this study, CDH1 promoter hypermethylation was observed in 54.8% (46/84) of the analyzed sporadic gastric carcinomas. We introduce a new relation: clustering of Goseki grading into 3 grade was determined by CDH1 promoter hypermethylation. The percentage of methylation in Goseki III cancers was significantly higher (83%) when compared with other grades; the lowest proportion was detected in IV (36%) and II (38%) groups, whereas grade I demonstrated typical percentage of promoter hypermethylation. A novel polymorphism R732R in exon 14 of the CDH1 gene was detected by mutational analysis. Additionally, all cases with the MSI-high phenotype revealed CDH1 promoter hypermethylation. In MSI-low and MSS gastric cancers, this percentage was lower, reaching 71% and 41%, respectively. Moreover, the methylation status was correlated with the LOH phenotype. We detected CDH1 promoter hypermethylation in all EBV-positive gastric cancers (5/5), whereas methylation in the EBV-negative group occurred in 58% of cases. We also report that “methylated” tumors were slightly larger than “nonmethylated,” whereas the second group revealed a higher probability of longer patient survival, though these relationships were not statistically significant. These results suggest that downregulation of E-cadherin, caused by promoter hypermethylation, in sporadic gastric carcinomas may be associated with a worse prognosis and specific tumor phenotype.

Dose response and kinetics of foci disappearance following exposure to high- and low-LET ionizing radiation

Purpose: The effect of different radiation qualities on (i) 53BP1 (p53 Binding Protein 1) and p-ATM (phosphorylated ataxia telangiectasia mutated) foci induction, and (ii) on the kinetics of foci disappearance was analysed. Material and methods: Normal human skin fibroblasts were exposed to 240 kV broad-field X-rays or targeted with individually counted helium (3He) particles or protons (1H) from a Charged Particle Microbeam. Anti-p-ATM and anti-53BP1 antibodies were used for foci visualisation via immunocytochemistry. Results: 1 Gy of X-rays yielded ≈ 33 53BP1-positive foci/cell. The ratio between the number of delivered particles and yielded tracks was found to be 1:1 and 3:1 after targeted 3He and 1H irradiation, respectively. It was determined that ≈ 50% of radiation-induced damage was repaired as measured by loss of foci during the first 2, 6, and 10 hours following X-ray, protons, and 3He irradiation, respectively. Conclusions: There was significant radiation quality dependence for 53BP1- and p-ATM-positive foci induction observed. Foci disappearance was radiation dose-independent in the samples irradiated with X-rays. Our results confirm that kinetics of foci disappearance depends on radiation quality, even when individual ions are targeted to cells.

High frequency of RPL22 mutations in microsatellite-unstable colorectal and endometrial tumors

Ribosomal Protein L22 (RPL22) encodes a protein that is a component of the 60S subunit of the ribosome. Variants in this gene have recently been linked to cancer development. Mutations in an A8 repeat in exon 2 were found in a recent study in 52% of microsatellite‐unstable endometrial tumors. These tumors are particularly prone to mutations in repeats due to mismatch repair deficiency. We screened this coding repeat in our collection of microsatellite‐unstable endometrial tumors (EC) and colorectal tumors (CRC). We found 50% mutation frequency for EC and 77% mutation frequency for CRC. These results confirm the previous study on the involvement of RPL22 in EC and, more importantly, reports for the first time such high mutation frequency in this gene in colorectal cancer. Furthermore, considering the high mutation frequency found, our data point toward an important role for RPL22 in microsatellite instability carcinogenesis.

Low-level microsatellite instability colorectal carcinomas: do they really belong to a "gray zone" between high-level microsatellite instability and microsatellite-stable cancers?

Abstract Background and aims. Colorectal carcinomas demonstrating low-level microsatellite instability (MSI-L) may form a distinct group differing both from high-level MSI (MSI-H) and microsatellite-stable (MSS) tumors. Materials and methods. In a retrospective series of 172 colorectal carcinomas the microsatellite status was examined based on DNA extracted from archival blocks. Three groups – MSS (n=100), MSI-L (n=37), MSI-H (n=35) – were compared with respect to clinical data, stage, histology, and immunoexpression of Ki-67, and P53. Results. Compared to MSS and MSI-H carcinomas the MSI-L tumors were exceptionally rarely right-sided, and demonstrated the lowest proliferation fraction. There was a trend for less frequent high-grade histology, more frequent intermediate P53 expression, and prominent mucinous histology. Conclusion. Features of MSI-L colorectal carcinomas are not necessarily located between their MSS and MSI-H counterparts. The MSI-L category may contain a group of tumors belonging to a distinct carcinogenetic pathway.

New Target Genes in Endometrial Tumors Show a Role for the Estrogen-Receptor Pathway in Microsatellite-Unstable Cancers

Microsatellite instability (MSI) in tumors results in an accumulation of mutations in (target) genes. Previous studies suggest that the profile of target genes differs according to tumor type. This paper describes the first genome‐wide search for target genes for mismatch repair‐deficient endometrial cancers. Genes expressed in normal endometrium containing coding repeats were analyzed for mutations in tumors. We identified 44 possible genes of which seven are highly mutated (>15%). Some candidates were also found mutated in colorectal and gastric tumors. The most frequently mutated gene, NRIP1 encoding nuclear receptor‐interacting protein 1, was silenced in an endometrial tumor cell line and expression microarray experiments were performed. Silencing of NRIP1 was associated with differences in the expression of several genes in the estrogen‐receptor network. Furthermore, an enrichment of genes related to cell cycle (regulation) and replication was observed. We present a new profile of target genes, some of them tissue specific, whereas others seem to play a more general role in MSI tumors. The high‐mutation frequency combined with the expression data suggest, for the first time, an involvement of NRIP1 in endometrial cancer development.

Colorectal carcinoma in Poland in 1975 and 1995: not only more, but also different

Background and aims: We previously reported that the sole clinicopathological parameters of carcinomas diagnosed in a single institution in 1975 differed from those in patients diagnosed in 1995. The findings might be compatible with the loss of importance of the microsatellite instability of the carcinogenic pathway. Materials and methods: We examined the microsatellite status and selected immunomarkers (Ki-67, p53, BAX) in the archival material from 1975 (n=76) and 1995 (n=105). Results and conclusion: The distribution of tumors showing no microsatellite instability, low microsatellite instability, and high microsatellite instability in the 2-yearly cohorts was similar (1975: 55.6%, 22.2%, 22.2%; 1995: 60.2%, 20.4%, 19.4%, respectively). The percentage of carcinomas showing microsatellite instability at the APC locus differed significantly (1975: 37.5%; 1995: 21.4%). The typical clinicopathological parameters of carcinomas exhibiting high microsatellite instability were largely shared by the carcinomas demonstrating instability at the APC locus. The carcinomas resected in 1995 more frequently demonstrated high expression of an antiapoptotic protein BAX and a different distribution of their Ki-67 proliferation fraction. The evolution of colorectal carcinoma in Poland also involves qualitative changes, including its genetic background.