Association of Functional Polymorphisms in MSH3 and IL-6 Pathway Genes with Different Types of Microsatellite Instability in Sporadic Colorectal Cancer.

Microsatellite instability (MSI) has been recognized as an important factor in colorectal cancer (CRC). It arises due to deficient mismatch repair (MMR), mostly attributed to MLH1 and MSH2 loss of function leading to a global MMR defect affecting mononucleotide and longer microsatellite loci. Recently, microsatellite instability at tetranucleotide loci, independent of the global MMR defect context, has been suggested to represent a distinct entity with possibly different consequences for tumorigenesis. It arises as a result of an isolated MSH3 loss of function due to its translocation from the nucleus to the cytoplasm under the influence of interleukin-6 (IL-6). In this study the influence of MSH3 and IL-6 signaling pathway polymorphisms (MSH3 exon 1, MSH3+3133A/G, IL-6-174G/C, IL-6R+48892A/C, and gp130+148G/C) on the occurrence of different types of microsatellite instability in sporadic CRC was examined by PCR-RFLP and real-time PCR SNP analyses. A significant difference in distribution of gp130+148G/C genotypes (p = 0.037) and alleles (p = 0.031) was observed in CRC patients with the C allele being less common in tumors with di- and tetranucleotide instability (isolated MSH3 loss of function) compared to tumors without microsatellite instability. A functional polymorphism in gp130 might modulate the IL-6 signaling pathway, directing it toward the occurrence of microsatellite instability corresponding to the IL-6-mediated MSH3 loss of function.

Genetic Influences of Proinflammatory Cytokines on Pain Severity in Patients with Temporomandibular Disorders.

This case-control study investigated single nucleotide polymorphism (SNP) genotypes (CXC motif chemokine ligand 8 (CXCL8): rs2227306 and rs2227307 and tumor necrosis factor (TNF): rs1800629) in 85 patients with pain-related temporomandibular disorders (TMDp) and 85 controls to explore their associations with TMDp presence, pain intensity (low/high), and the presence of chronic arthralgia/myalgia. TMDp was diagnosed using a validated protocol, and polymorphisms were genotyped from buccal mucosa swabs using TaqMan assays. High pain intensity individuals had an increased risk for carrying minor allele "G" (rs2227307) and "T" (rs2227306) compared to controls (76% vs. 55.3%, p = 0.012; 72% vs. 54.1%, p = 0.030, respectively). Carriers of the minor allele "G" (rs2227307) were more prevalent in TMDp patients with arthralgia compared to controls (70.30% vs. 55.30%, p = 0.037). According to logistic regression, the most important predictors for high pain intensity were minor allele "G" of rs2227307 (OR 2.435, 95% CI 1.123-5.282), increasing age (OR 1.038, 95% CI 1.002-1.075), and female sex (OR 4.592, 95% CI 1.289-16.361). The explored gene polymorphisms were not significant risk factors for TMDp presence. These findings highlight the importance of genetic variations, particularly rs2227307, in understanding the diverse clinical manifestations of temporomandibular disorders.

Unique miRNA Expression Profile in MSI- and EMAST-Unstable Sporadic Colon Cancer.

MicroRNAs (miRNAs) are critical post-transcriptional gene regulators and their involvement in sporadic colon cancer (CRC) tumorigenesis has been confirmed. In this study we investigated differences in miRNA expression in microsatellite stable (MSS/EMAST-S), microsatellite unstable marked by high elevated microsatellite alterations at selected tetranucleotide repeats (MSS/EMAST-H), and high microsatellite unstable (MSI-H/EMAST-H) tumor subgroups as well as in tumors with different clinicopathologic characteristics. An RT-qPCR analysis of miRNA expression was carried out on 45 colon cancer and adjacent normal tissue samples (15 of each group). Overall, we found three differentially expressed miRNAs between the subgroups. miR-92a-3p and miR-224-5p were significantly downregulated in MSI-H/EMAST-H tumors in comparison to other subgroups. miR-518c-3p was significantly upregulated in MSS/EMAST-H tumors in comparison to stable and highly unstable tumors. Furthermore, we showed that miR-143-3p and miR-145-5p were downregulated in tumors in comparison to normal tissues in all subgroups. In addition, we showed overexpression of miR-125b-5p in well-differentiated tumors and miR-451a in less advanced tumors. This is the first report on differences in miRNA expression profiles between MSS/EMAST-S, MSS/EMAST-H, and MSI-H/EMAST-H colorectal cancers. Our findings indicate that the miRNA expression signatures differ in CRC subgroups based on their instability status.

EMAST Type of Microsatellite Instability-A Distinct Entity or Blurred Overlap between Stable and MSI Tumors.

Microsatellite instability (MSI) represents an accumulation of frameshifts in short tandem repeats, microsatellites, across the genome due to defective DNA mismatch repair (dMMR). MSI has been associated with distinct clinical, histological, and molecular features of tumors and has proven its prognostic and therapeutic value in different types of cancer. Recently, another type of microsatellite instability named elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) has been reported across many different tumors. EMAST tumors have been associated with chronic inflammation, higher tumor stage, and poor prognosis. Nevertheless, the clinical significance of EMAST and its relation to MSI remains unclear. It has been proposed that EMAST arises as a result of isolated MSH3 dysfunction or as a secondary event in MSI tumors. Even though previous studies have associated EMAST with MSI-low phenotype in tumors, recent studies show a certain degree of overlap between EMAST and MSI-high tumors. However, even in stable tumors, (MSS) frameshifts in microsatellites can be detected as a purely stochastic event, raising the question of whether EMAST truly represents a distinct type of microsatellite instability. Moreover, a significant fraction of patients with MSI tumors do not respond to immunotherapy and it can be speculated that in these tumors, EMAST might act as a modifying factor.