Expression of DNA repair proteins, MSH2, MLH1 and MGMT in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients' survival

Screening for Biomarkers for Progression from Oral Leukoplakia to Oral Squamous Cell Carcinoma and Evaluation of Diagnostic Efficacy by Multiple Machine Learning Algorithms

The aim of the study is to identify key genes during the progression from oral leukoplakia (OL) to oral squamous cell carcinoma (OSCC) and predict effective diagnoses. Weighted gene co-expression network analysis (WGCNA) and differential expression analysis were performed to identify seven genes associated with the progression from OL to OSCC. Twelve machine learning algorithms including k-nearest neighbor (KNN), neural network (NNet), and extreme gradient boosting (XGBoost) were used to construct multi-gene models, which revealed that each model had good diagnostic efficacy. The functional mechanism or the pathways associated with these genes were evaluated using enrichment analysis, subtype clustering, and immune infiltration analysis. The enrichment analysis revealed that the genes enriched were associated with the cell cycle, cell division, and intracellular energy metabolism. The immunoassay results revealed that the genes primarily affected the infiltration of proliferating T cells and macrophage polarization. Finally, a nomogram and Kaplan-Meier survival analysis were used to predict the prognostic efficacy of key genes in OSCC patients. The results showed that genes could predict the prognosis of the patients, and patients in the high-risk group had a poor prognosis. Our study identified that the seven key genes, including DHX9, BCL2L12, RAD51, MELK, CDC6, ANLN, and KIF4A, were associated with the progression from OL to OSCC. These genes had good diagnostic efficacy and could be used as potential biomarkers for the prognosis of OSCC patients.

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.

DNA Damage Response during Replication Correlates with CIN70 Score and Determines Survival in HNSCC Patients

Aneuploidy is a consequence of chromosomal instability (CIN) that affects prognosis. Gene expression levels associated with aneuploidy provide insight into the molecular mechanisms underlying CIN. Based on the gene signature whose expression was consistent with functional aneuploidy, the CIN70 score was established. We observed an association of CIN70 score and survival in 519 HNSCC patients in the TCGA dataset; the 15% patients with the lowest CIN70 score showed better survival (p = 0.11), but association was statistically non-significant. This correlated with the expression of 39 proteins of the major repair complexes. A positive association with survival was observed for MSH2, XRCC1, MRE11A, BRCA1, BRCA2, LIG1, DNA2, POLD1, MCM2, RAD54B, claspin, a negative for ERCC1, all related with replication. We hypothesized that expression of these factors leads to protection of replication through efficient repair and determines survival and resistance to therapy. Protein expression differences in HNSCC cell lines did not correlate with cellular sensitivity after treatment. Rather, it was observed that the stability of the DNA replication fork determined resistance, which was dependent on the ATR/CHK1-mediated S-phase signaling cascade. This suggests that it is not the expression of individual DNA repair proteins that causes therapy resistance, but rather a balanced expression and coordinated activation of corresponding signaling cascades.

Evaluation of HPV and EBV in OSCC and the expression of p53, p16, E-cadherin, COX-2, MYC, and MLH1

OBJECTIVE

This study aimed to evaluate the presence of human papillomavirus (HPV) and Epstein-Barr virus (EBV) and the expression of p53, p16, E-cadherin, COX-2, MLH1, and MYC in oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

One hundred OSCC specimens were submitted to in situ hybridization for HPV and EBV, and immunohistochemistry for detection of the human proteins.

RESULTS

Thirty-one cases showed HPV in tumor tissue. EBV was not detected in any case investigated. The HPV(+) group demonstrated an increase of staining scores for nuclear p16 (p = .047), cytoplasmic MYC (p = .002), while a decrease for nuclear MLH1 (p = .048), suggesting that HPV may upregulate the expression of the first two proteins and down-regulate the latter.

CONCLUSION

Our findings reinforce the hypothesis of the HPV-related oral carcinogenesis involving the expression of p16 and MYC, and MLH1 suppression. Exclusively cytoplasmic stainings for p16, MLH1, and MYC were also associated with more advanced tumors. Finally, in view of the lack of studies correlating the HPV or EBV infection to the expression of oncoproteins, more researches assessing a broader panel of markers and employing different approaches are still necessary in order to understand the role of these viruses as well as the molecular mechanisms involved in the development and progression of oral carcinomas.

The Mismatch Repair System (MMR) in Head and Neck Carcinogenesis and Its Role in Modulating the Response to Immunotherapy: A Critical Review

Simple Summary

The dysfunction of the mismatch repair system, an important mechanism for the detection and correction of DNA replication mistakes, may often lead to instability in the length of specific genetic sequences, known as microsatellites, and to the accumulation of mutations. Microsatellite instability is a well-known risk factor for the development of colorectal cancers and other types of tumors but is also considered a positive predictor of the immunotherapy response. Malignancies harboring such a specific genomic instability are very immunogenic because of the great number of aberrant antigens they produce. Therapies based on the blockade of specific immune checkpoints have shown to induce an effective immune response against microsatellite-unstable cancer. Many studies proved that microsatellite instability has a decisive role in the carcinogenesis and the malignant progression of head and neck cancer and, in the near future, it may become a useful tool in tailoring immunotherapy also in this field of precision oncology.

Abstract

The mismatch repair (MMR) system has a major role in the detection and correction of DNA replication errors, resulting from DNA polymerase slippage or nucleotides misincorporation. Specific inherited/acquired alterations or epigenetic inactivation of MMR genes are associated with microsatellite instability (MSI): the loss of crucial function in repairing DNA alterations can promote carcinogenesis by favoring the accumulation of thousands of mutations in a broad spectrum of different anatomic sites such as colon, stomach, prostate, esophagus, endometrium, lung and head and neck. Recent extensive data suggest that tumor mutational burden strongly correlates with a clinical response to immunotherapy using checkpoint inhibitors and this response is influenced by MMR deficiency in a wide range of human solid cancers. In this context, few data about this crucial point are available for head and neck cancer (HNC). In this review, we discuss the role of MMR alterations and the resulting MSI in HNC pathogenesis. Furthermore, by summarizing the clinical available data on how they influence the progression of precancerous lesions and the risk of recurrence or second primary tumors, we want to define the current role of MSI in the management of HNC. Finally, we analyze the complex interaction between cancer cells and the immune system addressing the data now available about a potential correlation between microsatellite instability and immunotherapy response in HNC.

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.

MicroRNA and target mRNA selection through invasion and cytotoxicity cell modeling and bioinformatics approaches in esophageal squamous cell carcinoma

This study analyzed microRNA (miRNA) and mRNA expression profiles and investigated the biological characteristics of ESCC by using invasion and cytotoxicity cell models. miRNA profiles were evaluated through miRNA microarray. Transwell chamber and nedaplatin (NDP) were used to construct invasion and cytotoxicity cell models. Invasion Transwell and cytotoxicity assays were performed to examine the invasiveness and proliferation in the cell models. Functional miRNAs were selected from dysregulated miRNAs through qRT-PCR. Biometric Research Program (BRB)-array tools, Cytoscape plugins, and DAVID were utilized to find potential mRNAs targeted by these two miRNAs between ESCC and paired normal adjacent tissues. Our microarray obtained 11 dysregulated miRNAs expressed in three paired ESCC samples from Kazakhs (ethnicity in Northwestern China). qRT-PCR demonstrated the miRNA expression in the invasion and cytotoxicity cell models. miR‑652-5p and miR‑21‑5p exhibited a consistent expression level in the microarray and cell models. Bioinformatics revealed that the potential targets of PLD1, MSH2, STC1, and DSG1 might be involved in ESCC invasion and proliferation. Cell models with bioinformatics approaches may help distinguish functional genes. miR‑652-5p, miR‑21‑5p, and their potential target genes may participate in ESCC development and metastasis.

Integrative Genomics and Transcriptomics Analysis Reveals Potential Mechanisms for Favorable Prognosis of Patients with HPV-Positive Head and Neck Carcinomas

Patients with HPV-positive head neck squamous cell carcinomas (HNSCC) usually have a better prognosis than the HPV-negative cases while the underlying mechanism remains far from being well understood. We investigated this issue by an integrative analysis of clinically-annotated multi-omics HNSCC data released by the Cancer Genome Atlas. As confirmatory results, we found: (1) Co-occurrence of mutant TP53 and HPV infection was rare; (2) Regardless of HPV status, HNSCCs of wild-type TP53 implied a good survival chance for patients and had fewer genome-wide somatic mutations than those with a mutation burden on the gene. Our analysis further led to some novel observations. They included: (1) The genes involved in “DNA mismatch repair” pathway were up-regulated in HPV-positive tumors compared to normal tissue samples and HPV-negative cases, and thus constituted a strong predictive signature for the identification of HPV infection; (2) HPV infection could disrupt some regulatory miRNA-mRNA correlations operational in the HPV-negative tumors. In light of these results, we proposed a hypothesis for the favorable clinical outcomes of HPV-positive HNSCC patients. That is, the replication of HPV genome and/or its invasion into the genomes of cancer cells may enhance DNA repair mechanisms, which in turn limit the accumulation of lethal somatic mutations.

Human MutL homolog 1 immunoexpression in oral leukoplakia and oral squamous cell carcinoma: A prospective study in Indian population

BACKGROUND

Mammalian mismatch repair system is responsible for maintaining genomic stability during repeated duplications, and human MutL homolog 1 (hMLH1) protein constitutes an important part of it. Various isolated studies have reported the altered expression of hMLH1 in oral leukoplakia (OL) and oral squamous cell carcinoma (OSCC). Research is lacking in the quantitative estimation and comparison of hMLH1 expression in OL and OSCC.

AIMS

To evaluate, quantify and compare hMLH1 immunoexpression in normal oral mucosa, OL and OSCC.

SETTINGS AND DESIGN

Thirty patients of OL and thirty patients of OSCC formed the study group and thirty patients were included in the control group (normal oral mucosa). Formalin-fixed paraffin wax blocks were prepared from the tissue samples.

MATERIALS AND METHODS

Immunohistochemistry for hMLH1 was performed, and the total number of positive cells was counted in high-power fields, and based on that percentage positivity of hMLH1 was calculated in all the cases.

STATISTICAL ANALYSIS

Kruskal-Wallis and t-test were used. P < 0.05 was considered to be statistically significant.

RESULTS

The mean hMLH1 value in control group, leukoplakia and OSCC was 78.26, 54.33 and 40.97 respectively. hMLH1 immunoexpression showed decreasing indexes from control group to leukoplakia and then further to OSCC. hMLH1 expression was significantly lower in OSCC as compared to leukoplakia. There was no significant correlation of mean hMLH1 expression between different clinical and histopathological stages of leukoplakia and OSCC.

CONCLUSIONS

hMLH1 immunoexpression was inversely related to the degree of dysplasia. These findings suggest that there is a progressive decrease in hMLH1 expression from control to leukoplakia and further to OSCC. Thus, it can be concluded that hMLH1 can be used as a reliable biomarker for malignant transformation.

Metallothioneins and digestive system tumors

Metallothioneins (MTs) are low-molecular weight, cysteine-rich, intracellular metal-binding proteins involved in diverse functions, such as metal homeostasis and/or detoxification, scavenging free radicals and stress response. Recent studies show that MTs play an important role in cell differentiation, proliferation and carcinogenesis by displaying different expression patterns and through different signaling pathways, have important value for the clinical diagnosis, treatment and prognosis of tumors, and can be used as a cancer biomarker. This article aims to discuss the research progress in MTs as a cancer maker in human digestive system tumors.

Low expression of MSH2 DNA repair protein is associated with poor prognosis in head and neck squamous cell carcinoma

Objective

This study aimed to investigate the expression of the MSH2 DNA repair protein in head and neck squamous cell carcinoma (HNSCC) in order to analyze its association with clinicopathologic factors and overall survival of patients.

Material and Methods

Clinical data and primary lesions of HNSSC were collected from 55 patients who underwent surgical resection with postoperative radiotherapy in Montes Claros, state of Minas Gerais, Brazil, between 2000 and 2008. Immunohistochemical reactions were performed to analyze MSH2 protein expression.

Results

Bivariate analysis showed no significant correlation or association between MSH2 expression and clinicopathologic parameters by Mann-Whitney and Kruskal-Wallis tests. Patients with locoregional metastatic disease (OR=4.949, p<0.001) and lower MSH2 immunohistochemical expressions (OR=2.943, p=0.032) presented poorer survival for HNSCC by Cox regression models.

Conclusions

Our data demonstrated that lower MSH2 expression might contribute to a higher clinic aggressiveness of HNSCC by promoting an unfavorable outcome.

Genome stability pathways in head and neck cancers

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.

Prognostic molecular markers in cancer - quo vadis?

Despite the tremendous number of studies of prognostic molecular markers in cancer, only a few such markers have entered clinical practise. The lack of clinical prognostic markers clearly reflects limitations in or an inappropriate approach to prognostic studies. This situation should be of great concern for the research community, clinicians and patients. In the present review, we evaluate immunohistochemical prognostic marker studies in oral squamous cell carcinomas (OSCC) from 2006 to 2012. We comment upon general issues such as study design, assay methods and statistical methods, applicable to prognostic marker studies irrespective of cancer type. The three most frequently studied markers in OSCC are reviewed. Our analysis revealed that most new molecular markers are reported only once. To draw conclusions of clinical relevance based on the few markers that appeared in more than one study was problematic due to between-study heterogeneity. Currently, much valuable tissue material, time and money are wasted on irrelevant studies.

O(6)-methylguanine-DNA methyltransferase in equine sarcoids: molecular and epigenetic analysis

Background

Bovine papillomaviruses (BPVs) types 1 and 2 are the only known papillomaviruses able to jump the species. In fact, BPVs 1/2 induce neoplasia in their natural bovine host but infection is also associated to neoplastic skin lesions in equids termed sarcoids. The equine sarcoid is considered to be the most common equine cutaneous tumour worldwide for which no effective therapy is available. Very little is known about the molecular mechanisms underlying tumourigenesis, although genes contributing to sarcoid development have been identified. Several studies associate the development of cancer to the loss of function of a number of oncosuppressor genes. In this study the putative role of O⁶-methylguanine-DNA methyltrasferase (MGMT) was investigated for sarcoids. The expression of the oncosuppressor protein was assessed in normal and sarcoid cells and tissues. In addition, the DNA methylation profile was analysed to assess the role of epigenetic mechanism in regulation of MGMT expression.

Results

A group of 15 equine sarcoids and two primary sarcoid cell lines (fibroblasts) were analyzed for the expression of MGMT protein by immunohistochemistry, immunofluorescence and Western blotting techniques. The sarcoid cell line EqSO4b and the tumour samples showed a reduction or absence of MGMT expression. To investigate the causes of deregulated MGMT expression, ten samples were analyzed for the DNA methylation profile of the CpG island associated to the MGMT promoter. The analysis of 73 CpGs encompassing the region of interest showed in 1 out of 10 (10%) sarcoids a pronouncedly altered methylation profile when compared to the control epidermal sample. Similarily the EqSO4b cell line showed an altered MGMT methylation pattern in comparison to normal fibroblasts.

Conclusion

As previously demonstrated for the oncosuppressor gene FHIT, analysis of MGMT expression in sarcoid tissues and a sarcoid-derived fibroblast cell line further suggests that oncosuppressor silencing may be also involved in BPV-induced equine tumours. Abnormal DNA methylation seems to be one of the possible molecular mechanisms involved in the alteration of MGMT expression. Further studies are required to address other basic molecular mechanisms involved in reduced MGMT expression. This study underlines the possible role of DNA methylation in oncosuppressor inactivation in equine sarcoids.

FAK and Src expression in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients survival

PURPOSE

Focal adhesion kinase (FAK) and Src are protein tyrosine kinases, localized in the focal adhesions, which, upon activation interacts each other, regulate several cellular signaling pathways implicated in malignant transformation and disease progression. The present study aimed to evaluate the clinical significance of FAK and Src protein expression in mobile tongue squamous cell carcinoma (SCC).

METHODS

FAK and Src protein expression was assessed immunohistochemically on 48 mobile tongue SCC tissue samples and was analyzed in relation with clinicopathological characteristics, overall and disease-free patients' survival.

RESULTS

FAK positivity was noted in 32 (66.67 %) and Src positivity in 45 (93.75 %) out of 48 mobile tongue SCC cases. FAK and Src protein expression was significantly increased in well-differentiated tumors compared to poorly differentiated ones (p = 0.0455 and p = 0.0301, respectively). Mobile tongue SCC patients presenting elevated Src expression showed longer overall and disease-free survival (log-rank test, p = 0.0145 and p = 0.0388, respectively). In multivariate analysis, the depth of invasion proved to be an independent prognostic factor of both overall and disease-free patients' survival (Cox regression, p = 0.0313 and p = 0.0481, respectively), whereas Src expression did not remain significant.

CONCLUSIONS

The present study supported evidence for a potential role of FAK and Src signaling in mobile tongue SCC, rendering their small-molecule tyrosine kinase inhibitors as possible treatment strategy in tongue cancer chemoprevention.

Advances and applications of oral cancer basic research

Cancer of the oral cavity accounts for almost 3% of cancer cases in the world. The incidence varies widely reflecting geographic differences in exposure to risk factors. The recent rise in younger age groups and females seen in many countries is of particular concern. Treatment and management of complications, locoregional recurrence and further primary tumors result in high morbidity and mortality especially when the disease is advanced stage at initial diagnosis. Progress in cancer research has provided abundant new knowledge about cellular processes and molecular biology underlying oral carcinogenesis and tumor progression. The present review attempts to summarize the current most widely-used research approaches and their application in the prevention, diagnosis, effective treatment, and improved outcome of oral cancer.

Histone deacetylase-1 and -2 expression in mobile tongue squamous cell carcinoma: associations with clinicopathological parameters and patients survival

BACKGROUND

 Histone deacetylases (HDACs) have been associated with tumor development and progression in several types of human malignancy and HDAC inhibitors are currently being explored as anti-cancer agents in clinical trials. The aim of the present study was to evaluate the clinical significance of HDAC-1 and -2 protein expression in mobile tongue squamous cell carcinoma (SCC).

METHODS

HDAC-1 and -2 protein expression was assessed immunohistochemically on 49 mobile tongue SCC tissue samples and was analyzed in relation with clinicopathological characteristics, overall and disease-free patients' survival.

RESULTS

 HDAC-1 overexpression was significantly associated with younger patients' age (P = 0.0381) and male gender (P = 0.0345), poor histopathological grade of differentiation (P = 0.0236) and the presence of lymph node metastases (P = 0.0104). Intense HDAC-1 staining intensity was significantly associated with male gender (P = 0.0127), increased stromal infiltration reaction (P = 0.0125) and well-defined shape of tumor invasion (P = 0.0396). HDAC-2 overexpression did not show significant correlations with any clinicopathological parameters, whereas intense HDAC-2 staining intensity was significantly associated with the presence of muscular invasion (P = 0.0466) and advanced depth of invasion (P = 0.0251). Mobile tongue SCC patients with HDAC-1 overexpression presented shorter overall and disease-free survival compared to those with no evidence of HDAC-1 overexpression (log-rank test, P = 0.0651 and 0.0247, respectively).

CONCLUSIONS

 The present study supported evidence that HDACs may participate in the formation and progression of mobile tongue SCC, reinforcing their possible use as biomarkers as also the therapeutic utility of HDAC inhibitors in mobile tongue SCC chemoprevention and treatment.