MLH1, MSH2, MRE11, and XRCC1 in Oral Leukoplakia and Oral Squamous Cell Carcinoma

Investigating Tobacco's Impact on DNA Repair Genes and Risks in Oral Precancer and Cancer: A Comprehensive Research Study

Objective

This study aimed to explore genetic variations associated with DNA repair mechanisms to enhance the management of both oral cancer (OC) and oral precancer (OPC).

Methods

A cohort of 380 patients diagnosed with OC and OPC, comprising 220 males and 160 females, was analyzed. Participants were categorized based on their tobacco-chewing habits, with corresponding control groups established. Key genetic markers investigated for polymorphisms included OGG1, APE1, and XRCC1.

Results

The XRCC1 Arg280H variant demonstrated significant associations with the susceptibility to both OC and OPC across various models. Further analyses, incorporating factors such as tobacco and alcohol consumption, unveiled a correlation between the XRCC1 Arg194Trp variant and an elevated risk of developing head and neck cancer. Stratified analyses also revealed an increased risk of OC or OPC based on the specific site of the cancer.

Conclusion

The study underscores the importance of XRCC1 polymorphisms, particularly XRCC1 Arg280H and XRCC1 Arg194Trp, within the genetic framework of OC and OPC. Understanding these genetic associations provides valuable insights for the potential development of targeted interventions aimed at individuals predisposed to these conditions.

Sustained inactivation of the Polycomb PRC1 complex induces DNA repair defects and genomic instability in epigenetic tumors

Cancer initiation and progression are typically associated with the accumulation of driver mutations and genomic instability. However, recent studies demonstrated that cancer can also be driven purely by epigenetic alterations, without driver mutations. Specifically, a 24-h transient downregulation of polyhomeotic (ph-KD), a core component of the Polycomb complex PRC1, is sufficient to induce epigenetically initiated cancers (EICs) in Drosophila, which are proficient in DNA repair and characterized by a stable genome. Whether genomic instability eventually occurs when PRC1 downregulation is performed for extended periods of time remains unclear. Here, we show that prolonged depletion of PH, which mimics cancer initiating events, results in broad dysregulation of DNA replication and repair genes, along with the accumulation of DNA breaks, defective repair, and widespread genomic instability in the cancer tissue. A broad misregulation of H2AK118 ubiquitylation and to a lesser extent of H3K27 trimethylation also occurs and might contribute to these phenotypes. Together, this study supports a model where DNA repair and replication defects accumulate during the tumorigenic transformation epigenetically induced by PRC1 loss, resulting in genomic instability and cancer progression.

New insights into redox-related risk factors and therapeutic targets in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common cancer in the oral cavity accounting for 90 % of oral cancer with a global incidence of 350.000 new cases per year. Curative resection along with adjuvant radiation therapy or a combination of radiotherapy with chemotherapy remain as gold standard in treating OSCC. Still, local recurrence, lymph nodal recurrence, and complications of radiation remain the main cause of tumor-related mortality. Reactive oxygen species are not only correlated to the etiology of OSCC due to oxidative DNA damage, lipid peroxidation or effecting signal transduction cascades that effect cell proliferation and tumorigenesis, but are also of great interest in the therapy of OSCC patients. As induced oxidative stress can be used therapeutically for the induction of tumor cell death, redox targets might be a therapeutic addition to the conventional treatment options. In this review, we discuss markers of impaired redox homeostasis as well as potential redox-related treatment targets in OSCC.

Targeting DNA damage response as a potential therapeutic strategy for head and neck squamous cell carcinoma

Cells experience both endogenous and exogenous DNA damage daily. To maintain genome integrity and suppress tumorigenesis, individuals have evolutionarily acquired a series of repair functions, termed DNA damage response (DDR), to repair DNA damage and ensure the accurate transmission of genetic information. Defects in DNA damage repair pathways may lead to various diseases, including tumors. Accumulating evidence suggests that alterations in DDR-related genes, such as somatic or germline mutations, single nucleotide polymorphisms (SNPs), and promoter methylation, are closely related to the occurrence, development, and treatment of head and neck squamous cell carcinoma (HNSCC). Despite recent advances in surgery combined with radiotherapy, chemotherapy, or immunotherapy, there has been no substantial improvement in the survival rate of patients with HNSCC. Therefore, targeting DNA repair pathways may be a promising treatment for HNSCC. In this review, we summarized the sources of DNA damage and DNA damage repair pathways. Further, the role of DNA damage repair pathways in the development of HNSCC and the application of small molecule inhibitors targeting these pathways in the treatment of HNSCC were focused.

Comprehensive development and validation of gene signature for predicting survival in patients with glioblastoma

Glioblastoma (GBM) is the most common brain tumor, with rapid proliferation and fatal invasiveness. Large-scale genetic and epigenetic profiling studies have identified targets among molecular subgroups, yet agents developed against these targets have failed in late clinical development. We obtained the genomic and clinical data of GBM patients from the Chinese Glioma Genome Atlas (CGGA) and performed the least absolute shrinkage and selection operator (LASSO) Cox analysis to establish a risk model incorporating 17 genes in the CGGA693 RNA-seq cohort. This risk model was successfully validated using the CGGA325 validation set. Based on Cox regression analysis, this risk model may be an independent indicator of clinical efficacy. We also developed a survival nomogram prediction model that combines the clinical features of OS. To determine the novel classification based on the risk model, we classified the patients into two clusters using ConsensusClusterPlus, and evaluated the tumor immune environment with ESTIMATE and CIBERSORT. We also constructed clinical traits-related and co-expression modules through WGCNA analysis. We identified eight genes (ANKRD20A4, CLOCK, CNTRL, ICA1, LARP4B, RASA2, RPS6, and SET) in the blue module and three genes (MSH2, ZBTB34, and DDX31) in the turquoise module. Based on the public website TCGA, two biomarkers were significantly associated with poorer OS. Finally, through GSCALite, we re-evaluated the prognostic value of the essential biomarkers and verified MSH2 as a hub biomarker.

DNA Methylation by Bisulfite Next-Generation Sequencing for MLH1 and MGMT in Oral Squamous Cell Carcinomas and Potentially Malignant Disorders: An Integrative Analysis towards Field Cancerization

Background and Objectives: MGMT methylation is a well-described biomarker in several solid tumors and MLH1 seems to occur in the initial stages of oral carcinogenesis. The aims of this study were to evaluate MHL1 and MGMT methylation levels in oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMDs), and to integrate this information with The Cancer Genome Atlas (TCGA) database. Materials and Methods: To determine the percentage of gene methylation in MLH1 and MGMT, pyrosequencing analysis was conducted. Samples were divided as follows: (1) patients diagnosed with OSCC (N = 16); (2) patients with OPDM who developed OSCC in the same location (N = 47); and (3) patients with OPDM who developed OSCC in a different location (N = 22). As a validation cohort in this study, data from The Cancer Genomic Atlas (TCGA) database, particularly regarding Head and Neck Squamous Cell Carcinoma, was used. Results: Overall MLH1 methylation levels of 8.6 ± 11.5% and 8.1 ± 9.2% for MGMT were obtained. With regard to MHL1, the OSCC presented the highest degree of methylation with 9.3 ± 7.3% (95%CI 5.1–13.6), and with regards to MGMT, the simultaneous malignancy group presented the highest degree of methylation with 10 ± 13.5% (95%CI 6–10), although no significant differences were found between the groups (p = 0.934 and p = 0.515, respectively). The estimated survival was higher for MGMT methylated cases (19.1 months, 95%CI 19.1–19.1) than for unmethylated cases (9.4 months, 95%CI 6–12.8), but not statistically significant. Conclusions: Our results did not show a correlation between MGMT and MLH1 methylation and any clinicopathological feature or survival in our institutional cohort. MLH1 methylation was present mainly in OSCC, whilst MGMT in OPMD represented a modest contribution to field cancerization, with an overall consistency with the TCGA database.

Analysis of the Expression and Prognostic Value of MSH2 in Pan-Cancer Based on Bioinformatics

Background

MutS homolog 2 (MSH2), with the function of identifying mismatches and participating in DNA repair, is the “housekeeping gene” in the mismatch repair (MMR) system. MSH2 deficiency has been reported to enhance cancer susceptibility for the association of hereditary nonpolyposis colorectal cancer. However, the expression and prognostic significance of MSH2 have not been studied from the perspective of pan-cancer.

Methods

The GTEx database was used to analyze the expression of MSH2 in normal tissues. The TCGA database was used to analyze the differential expression of MSH2 in pan-cancers. The prognostic value of MSH2 in pan-cancer was assessed using Cox regression and Kaplan-Meier analysis. Spearman correlations were used to measure the relationship between the expression level of MSH2 in pan-cancer and the level of immune infiltration, tumor mutational burden (TMB), and microsatellite instability (MSI).

Results

MSH2 is highly expressed in most type of cancers and significantly correlated with prognosis. In COAD, KIRC, LIHC, and SKCM, the expression of MSH2 was significantly positively correlated with the abundance of B cells, CD4+ T cells, CD8+ T cells, dendritic cells, macrophages, and neutrophils. In THCA, MSH2 expression correlated with CD8+T Cell showed a significant negative correlation. MSH2 had significantly negative correlations with stromal score and immune score in a variety of cancers and significantly correlated with TMB and MSI of a variety of tumors.

Conclusions

MSH2 may play an important role in the occurrence, development, and immune infiltration of cancer. MSH2 can emerge as a potential biomarker for cancer diagnosis and prognosis.