A Review of the Repair of DNA Double Strand Breaks in the Development of Oral Cancer

We explore the possibility that defects in genes associated with the response and repair of DNA double strand breaks predispose oral potentially malignant disorders (OPMD) to undergo malignant transformation to oral squamous cell carcinoma (OSCC). Defects in the homologous recombination/Fanconi anemia (HR/FA), but not in the non-homologous end joining, causes the DNA repair pathway to appear to be consistent with features of familial conditions that are predisposed to OSCC (FA, Bloom's syndrome, Ataxia Telangiectasia); this is true for OSCC that occurs in young patients, sometimes with little/no exposure to classical risk factors. Even in Dyskeratosis Congenita, a disorder of the telomerase complex that is also predisposed to OSCC, attempts at maintaining telomere length involve a pathway with shared HR genes. Defects in the HR/FA pathway therefore appear to be pivotal in conditions that are predisposed to OSCC. There is also some evidence that abnormalities in the HR/FA pathway are associated with malignant transformation of sporadic cases OPMD and OSCC. We provide data showing overexpression of HR/FA genes in a cell-cycle-dependent manner in a series of OPMD-derived immortal keratinocyte cell lines compared to their mortal counterparts. The observations in this study argue strongly for an important role of the HA/FA DNA repair pathway in the development of OSCC.

Association Between X-Ray Repair Cross-Complementing Group 1 Arg399Gln Polymorphism and Risk of Oral Leukoplakia: A Meta-analysis

Aims: Previous studies have have reported inconsistent results regarding the association of the XRCC1 polymorphism Arg399Gln with oral leukoplakia (OLK) risk. This study was designed to assess the existing evidence of this association using a meta-analytic approach. Materials and Methods: The literature was searched using multiple databases, including PubMed, EMBASE, and China National Knowledge Infrastructure (CNKI), through October 22, 2020. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of any associations. Results: A total of 671 Indian cases and 1009 Indian controls from seven case-control studies were included in the meta-analysis. The overall analysis revealed that the AA genotype was associated with a significantly increased OLK risk compared with the GG+GA genotypes (OR = 1.51, 95% CI = 1.10-2.06). In the subgroup analysis stratified by tobacco use, a significant association was found in the mixed group (OR = 1.51, 95% CI = 1.12-2.56), but not in the tobacco-using group or the no tobacco use group. In the OLK subtype subgroup analysis, a significantly increased risk was found in the hyperplastic subgroup (OR = 5.01, 95% CI = 1.39-18.11), whereas no associations were found in the dysplastic or mixed subgroups. Conclusions: The results of this meta-analysis suggest that the XRCC1 Arg399Gln polymorphism may significantly contribute to susceptibility to OLK in the Indian population.

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

BACKGROUND

DNA damage is accumulated in the cells over time as the result of both exogenous and endogenous factors. The objective of this study was to analyze the immunohistochemical expression of the repair proteins in oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Paraffin blocks were selected from the archives of the Laboratory of Hospital Clinico Universitario de Santiago de Compostela, Spain. The sample was composed of 16 cases of OL without dysplasia, 14 cases of OL with dysplasia, and 15 cases of OSCC. The patients' clinical data were collected and immunohistochemical analysis was performed for MLH1, MSH2, MRE11, and XRCC1. The data were submitted to the χ2 and the Kruskal-Wallis (P≤0.05) tests.

RESULTS

MSH2 was overexpressed in OSCC (P=0.020) and was positive in 100% of patients with OL with dysplasia or OSCC (P=0.019). Positivity for MLH1 was significantly associated with comorbidity (P=0.040), especially in patients who presented with 2 or more pathologies (P=0.028). XRCC1 positivity was also associated with comorbidity (P=0.039). No significant associations were found for the MRE11A expression. Although the simultaneous positivity for the 4 markers was observed in presence of comorbidities (P=0.006).

CONCLUSIONS

This study supports the effect of the overexpression of MSH2 protein in samples of OL with dysplasia and OSCC, most notably in patients who present with comorbidities and negativity for OL without dysplasia.

Genetic polymorphism of tumor necrosis factor alpha (TNF-α) and tumor necrosis factor beta (TNF-β) genes and risk of oral pre-cancer and cancer in North Indian population

OBJECTIVE

There are inconclusive data connecting single-nucleotide polymorphisms (SNPs) of TNF-α (rs361525) and TNF-β (rs909253) to potential malignant oral disorder (PMOD) such as lichen planus and oral fibrosis. Here, we have investigated the risk of oral squamous cell carcinoma as well as oral pre-cancerous lesions in North Indian population with the polymorphism of the TNFα/ β genes.

MATERIAL AND METHODS

A total 500 patients with oral pre-cancer and OSCC and 500 healthy volunteers were genotypes for the TNF-α (-238) G/A (rs361525) and TNF-β (252) A/G (rs909253) gene polymorphism. Genotypes were identified by polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP). Genotype frequencies were evaluated by Chi-square test.

RESULTS

Compared to the GG genotype, the GA genotype of TNF-α (G238A) polymorphism (rs361525) has been found to significantly increase the risk of oral disease (OR = 1.99) and especially the risk of lichen planus and OSCC (OR = 2.805 and 5.790, respectively). Similarly, the risk of oral disease was also more in the heterozygote (AG) than the common allele homozygote (AA) of TNF-β (A252G) polymorphism (rs909253) (OR = 1.483).

CONCLUSION

We conclude that the SNPs rs361525 and rs909253 were significantly associated with oral pre-cancer and OSCC.

Relationship of the XRCC1 rs25487 polymorphism with demographic, behavioral, clinical, and histological parameters in oral potentially malignant disorders and oral squamous cell carcinoma in a Colombian population

OBJECTIVES

To evaluate the salivary detection of XRCC1 rs25487 single-nucleotide polymorphism (SNP), its relationship with clinicopathological characteristics, and the interactions with demographic/behavioral variables in the etiopathogenesis of oral potentially malignant disorders (OPMD) and oral squamous cell carcinoma (OSCC) in a Colombian population.

METHODS

Demographic/behavioral data and saliva samples were obtained from patients with oral leukoplakia (OL, n = 17) and oral lichenoid lesions with epithelial dysplasia (OLL-ED, n = 10), or OSCC (n = 45), along with healthy controls (n = 40). Tissue biopsies were obtained for histological assessment and genetic analysis was performed using polymerase chain reaction-restriction fragment length polymorphism. Descriptive analyses were used to compare the distribution of genotypes/alleles between study groups alongside an analysis of the interaction between genetic findings and demographic/behavioral variables.

RESULTS

No association was observed between the genotype and allele frequencies in OPMD or OSCC. The AG genotype was significantly more frequent in OL with high-grade dysplasia, acanthotic epithelial lining, moderate-to-severe mitotic count, and negative-to-mild apoptotic count; and in OSCC cases with stage III/IV, poorly differentiated, perineural/lymphovascular invasion, severe cellular atypia, moderate-to-severe mitotic count, and negative-to-mild apoptotic counts. Significant interaction effects were detected in the AG genotype with regard to ageing, smoking habits, and alcohol consumption in both OL and OSCC.

CONCLUSION

Although rs25487 SNP appeared to not modulate the risk of OPMD/OSCC independently, its significant association with clinicopathological characteristics in OL and OSCC, and the synergistic interaction between ageing and smoking/alcohol consumption, might play a role in these two diseases.

New Insights Into Oral Squamous Cell Carcinoma: From Clinical Aspects to Molecular Tumorigenesis

Oral squamous cell carcinoma (SCC) is a prevalent malignant disease worldwide, especially so in Taiwan. Early- or even preclinical-stage detection is critical for reducing morbidity and mortality from oral SCC. Epidemiological and genome association studies are useful for identifying clinicopathological risk factors for preventive, diagnostic, and therapeutic approaches of oral SCC. For advanced oral SCC, effective treatments are critical to prolonging survival and enhancing quality of life. As oral SCC is characteristic of regional invasion with lymph node metastases, understanding the aggressive features of oral SCC, particularly in lymphangiogenesis, is essential for determining effective treatments. Emerging evidence has demonstrated that the tumor microenvironment (TME) plays a pivotal role in tumor growth, invasion, and metastases. Recent clinical successes in immune checkpoint inhibitors either alone or combined with chemotherapy have also supported the therapeutic value of immunotherapy in oral SCC. This review summarizes critical advances in basic knowledge of oral SCC from the perspective of clinicopathological risk factors, molecular tumorigenesis, and the TME. We also highlight our recent investigations on the microbiome, genome association studies, lymphangiogenesis, and immunomodulation in oral SCC. This review may provide new insights for oral SCC treatment by systematically interpreting emerging evidence from various preclinical and clinical studies.

Expression of DNA repair genes in oral squamous cell carcinoma using reverse transcription-quantitative polymerase chain reaction

OBJECTIVE

The aim of this study was to evaluate the expression of DNA repair genes in cases of oral squamous cell carcinoma (OSCC).

STUDY DESIGN

Expression of the MLH1, MSH2, MLH3, ATM, MRE11A, XRCC1, and PMS2 genes was evaluated by reverse transcription-quantitative polymerase chain reaction in the OSCC group (32 patients) and the control group (15 patients). The groups were compared by using the Mann-Whitney test, with Bonferroni correction. Associations between gene expression levels and clinical data were explored by using Pearson's and Spearman's correlation coefficients, with P value less than .05 indicating a significant difference.

RESULTS

The MLH1, MSH2, MLH3, ATM, MRE11A, XRCC1, and PMS2 genes were downregulated in the OSCC group compared with the control group, with significant values for MLH1 (P < .0001); MSH2 (P = .038); MLH3 (P < .0001); ATM (P < .0001); MRE11A (P < .0001); XRCC1 (P = .0004); and PMS2 (P = .008). Analysis of the correlation between gene expression and clinical data only revealed a significant negative correlation between age and expression of the PMS2 gene.

CONCLUSIONS

Expression of the DNA repair genes MLH1, MSH2, MLH3, ATM, MRE11 AMRE11A, XRCC1, and PMS2 was reduced in OSCC.

Associations Among Glutathione S-Transferase T1, M1, and P1 Polymorphisms and the Risk of Oral Leukoplakia

AIMS

The potential association between glutathione S-transferase (GST) M1, T1, P1 polymorphisms and the risk of oral leukoplakia (OLK) has been extensively studied. However, the results of previous studies have been contradictory. In an effort to resolve these different findings we performed a meta-analysis.

MATERIALS AND METHODS

Eligible articles were identified by a search of PubMed, the China National Knowledge Infrastructure (CNKI), MEDLINE, EMBASE, and the Web of Science databases through December 1, 2015. Crude odds ratios (ORs) with 95% confidence intervals were used to evaluate the risk of OLK by tobacco use, ethnicity, and OLK subtype.

RESULTS

A total of 3122 cases and 6037 controls were included in the meta-analysis. The results indicated that the glutathione S-transferase Mu1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms increase the risk of OLK (OR = 1.838, 95% CI = 1.582-2.134 and OR = 1.337, 95% CI = 1.132-1.579, respectively), especially in the groups with tobacco use (OR = 2.478, 95% CI = 2.032-3.020 and OR = 2.034, 95% CI = 1.486-2.783, respectively). Conversely the glutathione S-transferase P1 (GSTP1) polymorphism did not demonstrate a significant relationship with OLK risk (OR = 1.139, 95% CI = 0.900-1.442). The GSTM1 and GSTT1 null polymorphisms were identified as being significantly associated with an increased risk of OLK within the German and Indian populations: German subgroup (GSTM1: OR = 11.555, 95% CI = 7.465-17.884), Indian subgroup (GSTM1: OR = 1.333, 95% CI = 1.084-1.638; GSTT1: OR = 1.332, 95% CI = 1.057-1.679).

CONCLUSIONS

Our findings provide evidence that the GSTT1 and GSTM1 null polymorphisms may be risk factors of OLK, especially for persons who use tobacco, whereas the GSTP1 polymorphism does not contribute to the development of OLK. Thus, detection of GSTT1 and GSTM1 null polymorphisms may be promising biomarkers for the OLK susceptibility.

Involvement of the XRCC1 Arg399Gln gene polymorphism in the development of cervical carcinoma

BACKGROUND

Although infection with the human papillomavirus (HPV) is crucial to the development of cervical cancer, it is not considered a sufficient isolated factor to cause this malignancy. The association of the XRCC1 Arg399Gln (rs25487) polymorphism with cervical cancer has been demonstrated in some populations.

METHODS

The XRCC1 Arg399Gln genetic variants were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in patients with advanced cervical cancer (n=189) and controls (n=308).

RESULTS

We observed that patients with advanced cervical cancer having the Gln/Gln or Gln/Arg vs Arg/Arg genotype displayed a 1.726-fold increased risk of cervical cancer (95% confidence interval [CI]=1.158-2.572, p=0.007). The odds ratio (OR) for Gln/Gln vs Gln/Arg or Arg/Arg was 1.742 (95% CI=1.073-2.827; p=0.0236). We also found a significantly higher frequency of the XRCC1 399Gln allele in patients with cancer than in controls, with OR=1.489 (95% CI=1.148-1.930, p=0.0026). The p value of the chi-square test for the trend observed for the XRCC1 Arg399Gln polymorphism was also statistically significant (ptrend=0.002). The statistical power of this study amounted to 78% for the Gln/Gln or Gln/Arg genotypes and 61% for the Gln/Gln genotype.

CONCLUSION

Although the statistical power of our study did not reach 80%, we found a statistically significant association between the XRCC1 399Gln variant and the incidence of cervical cancer.

Associated risk of XRCC1 and XPD cross talk and life style factors in progression of head and neck cancer in north Indian population

Effective DNA repair machinery ensures maintenance of genomic integrity. Environmental insults, ageing and replication errors necessitate the need for proper DNA repair systems. Any alteration in DNA repair efficacy would play a dominant role in progression of squamous cell carcinoma of head and neck (SCCHN). Genotypes of XRCC1 gene-Arg194Trp, Arg280His, Arg399Gln and XPD Lys751Gln, by PCR-RFLP were studied in 278 SCCHN patients and an equal number of matched healthy controls residing in north India. In XRCC1 polymorphisms, Arg194Trp and Arg399Gln variants showed a reduced risk, whereas, XPD Lys751Gln variants exhibited ∼2-fold increase in SCCHN risk. With XRCC1-Arg280His variants, there was no association with SCCHN risk. Arg399Gln of XRCC1 appears to have a protective role in people those consume alcohol, while XPD Lys751Gln variants indicated ∼2-fold increased risk of SCCHN in all the co-variate groups. Comparison of gene-gene interaction among XRCC1 Arg280His and XPD Lys751Gln suggested enhanced risk of SCCHN by ∼2.3-fold in group one and ∼6.1-fold in group two. In dichotomized groups of this combination, the risk was ∼2.4 times. Haplotype analysis revealed the frequency of C-G-G-G and C-A-G-G to be significantly associated with an increased risk of SCCHN. On the contrary, T-G-A-A significantly diminished the risk. CART analysis results showed that the terminal node that contains homozygous mutants of XPD Lys751Gln and XRCC1 Arg194Trp, wild type of XRCC1 Arg399Gln and homozygous mutant of XRCC1 Arg280His, represent the highest risk group. Our results demonstrate high degree of gene-gene interaction involving DNA repair genes of NER and BER pathways, namely XRCC1 and XPD. This study amply demonstrates positive association of XPD Arg751Gln polymorphism with an increased risk of SCCHN. Further, XRCC1 Arg280His variant though dormant individually, may also contribute to the development of cancer in combination with XPD Arg751Gln.