Expression patterns of cancer stem cell markers ALDH1 and CD133 correlate with a high risk of malignant transformation of oral leukoplakia

Mitochondria in oral cancer stem cells: Unraveling the potential drug targets for new and old drugs

Head and neck cancer is a major health problem worldwide, with most cases arising in the oral cavity. Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, accounting for over 90% of all cases. Compared to other types of cancer, OSCC, has the worse prognosis, with a 5-year survival rate of 50%. Additionally, OSCC is characterized by a high rate of resistance to chemotherapy treatment, which may be partly explained by the presence of cancer stem cells (CSC) subpopulation. CSC can adapt to harmful environmental condition and are highly resistant to both chemotherapy and radiotherapy treatments, thus contributing to tumor relapse. The aim of this review is to highlight the role of mitochondria in oral CSC as a potential target for oral cancer treatment. For this purpose, we reviewed some fundamental aspects of the most validated protein markers of stemness, autophagy, the mitochondrial function and energy metabolism in oral CSC. Moreover, a discussion will be made on why energy metabolism, especially oxidative phosphorylation in CSC, may offer such a diverse source of original pharmacological target for new drugs. Finally, we will describe some drugs able to disturb mitochondrial function, with emphasis on those aimed to interrupt the electron transport chain function, as novel therapeutic strategies in multidrug-resistant oral CSC. The reutilization of old drugs approved for clinical use as new antineoplastics, in cancer treatment, is also matter of revision.

Cancer Stem Cells' Biomarker ALDH1&2 Increased Expression in Erosive Oral Lichen Planus Compared to Oral Leukoplakia

INTRODUCTION

ALDH1&2 has been considered an oral cancer stem cell (CSC) marker. Oral carcinogenesis is a process that usually passes through oral potentially malignant disorders (OPMD). Oral lichen planus (OLP) consists of immune-related chronic disorders that have been included in the OPMDs due to their possible transformation into oral cancer. The aim of this study was to investigate the early presence of ALDH1&2 in OLP compared to early oral leukoplakias (OL), especially mildly and non-dysplastic OL.

MATERIALS AND METHODS

The study type is experimental, and the study design is characterized as semiquantitative research which belongs to the branch of experimental research. The study sample consisted of paraffin-embedded OLP biopsy samples from the archives of the Department of Oral Medicine/Pathology, School of Dentistry, Aristotle University of Thessaloniki, Greece, during the period 2009-2019. The study sample contained 24 cases of OLP (14 erosive and 10 reticular) and 30 cases of OL (16 cases of moderately and severely dysplastic OL and 14 cases of mildly and non-dysplastic OL). The CSC-related biomarker ALDH1&2 was examined using semiquantitative immunohistochemistry (monoclonal antibody sc-166362, Santa Cruz Biotechnology, Dallas, Texas, USA, 1:100). ALDH1&2 expression was evaluated through a scale of 1 to 3 depending on the percentage of positive epithelial cells and was compared to normal epithelium as well as cases of OL (the most prominent OPMD). The statistical analysis was performed with the Pearson chi-square test and the significance level was set at p≤0.05.

RESULTS

The cytoplasmic staining of ALDH1&2 was observed mostly in the epithelial cells of the basal layer of the epithelium of OLP. Overall, this expression was significantly increased compared to normal epithelium. In addition, statistically significantly higher expression of ALDH1&2 was observed in the erosive form of OLP. Interestingly, this OLP positivity was higher compared to mild and non-dysplastic leukoplakias (p<0.001).

CONCLUSIONS

ALDH1&2 is a confirmed CSC marker that was found to be clearly increased in OLP and characteristically in erosive OLP epithelium for the first time. Noteworthy, it was more prominent in erosive OLP rather than in mildly and non-dysplastic OL. Whether this pattern of expression raises the red flag of an early epithelial "CSC" phenotype in OLP or that ALDH1&2 expression indicates a response to the OLP inflammatory process requires further investigation.

Altered Presence of Cancer Stem Cell ALDH1/2 in Oral Leukoplakias and Squamous Cell Carcinomas

INTRODUCTION

Cancer stem cells (CSCs) are responsible for initiating the process of carcinogenesis by enabling the self-renewal and self-proliferation of the cancer cells. This study aimed to investigate the presence of epithelial cells with cancer stem cells characteristics (ALDH+) in the early stages of oral precancerous lesions (Oral Leukoplakias) and the frequency of these cells in the different stages of oral squamous cell carcinomas (OSCCs).

MATERIALS & METHODS

The aim of this study was the detection of the immunohistochemical pattern of expression of CSC protein-biomarker ALDH1&2 (sc-166362, Santa Cruz Co, Dallas, Texas, USA) in paraffin-embedded samples of 30 cases of leukoplakia of all degrees of dysplasia and 21 cases of oral squamous cell carcinomas (OSCC) of all degrees of differentiation compared to the histologically normal oral epithelium. The samples were retrieved from 2009-2019 from the archives of the Department of Oral Medicine/Pathology, School of Dentistry, Aristotle University of Thessaloniki, Greece. The samples were evaluated through a three-tier scale (positive cells Ι: 6-35%, ΙΙ: 36-70%, ΙΙΙ: 71-100%). Statistical analysis was performed through SPSS Pearson Chi-square, and the significance level was set at 0.05 (p=0.05).  Results: The staining of ALDH1&2 was observed mildly in the cell membrane of cells in the stratum spinosum of the normal epithelium and the cell membrane of cells in the stratum basale of the normal epithelium, characteristically at the interface point with the basal membrane. ALDH1&2 were expressed significantly more in the OSCC than in the leukoplakia (p-value=0.0001) and the normal epithelium (p-value=0.0001). Mainly, ALDH1&2 were expressed significantly more in the severely and moderately dysplastic oral leukoplakia compared to the mildly dysplastic and non-dysplastic leukoplakia (p-value=0.001).

DISCUSSION

The characteristic expression of ALDH in potentially malignant oral and OSCC lesions suggests the presence of CSCs and their possible implication in the early stages of oral tumorigenesis, even at the stage of oral leukoplakia.

Biomarkers of malignant transformation in oral leukoplakia: from bench to bedside

Oral leukoplakia is a common precursor lesion of oral squamous cell carcinoma, which indicates a high potential of malignancy. The malignant transformation of oral leukoplakia seriously affects patient survival and quality of life; however, it is difficult to identify oral leukoplakia patients who will develop carcinoma because no biomarker exists to predict malignant transformation for effective clinical management. As a major problem in the field of head and neck pathologies, it is imperative to identify biomarkers of malignant transformation in oral leukoplakia. In this review, we discuss the potential biomarkers of malignant transformation reported in the literature and explore the translational probabilities from bench to bedside. Although no single biomarker has yet been applied in the clinical setting, profiling for genomic instability might be a promising adjunct.

Can precancerous stem cells be risk markers for malignant transformation in the oral mucosa?

Accurate assessment of the carcinogenic potential of oral mucosal diseases can significantly reduce the prevalence of oral cancer. We speculate that precancerous stem cells (pCSCs) arise during the evolution of carcinomas based on long-term experimental findings, published literature, and the cancer stem cell (CSC) theory, wherein pCSCs exist in precancerous lesions and have characteristics of both CSCs and normal stem cells. This apparently contradictory feature may be the foundation of the reversible transformation of precancerous lesions. Predicting malignant transformation in potentially malignant oral illnesses would allow for focused treatment, prognosis, and secondary prevention. Currently available clinical assays for chromosomal instability and DNA aneuploidy have several deficiencies. We hope that our study will increase attention to pCSC research and lead to the development of novel strategies for the prevention and treatment of oral cancer by identifying pCSC markers.

Molecular Biomarkers of Malignant Transformation in Head and Neck Dysplasia

Head and neck squamous cell carcinoma (HNSCC) and its treatments are associated with substantial morbidity, often resulting in cosmetic deformity and loss of physiologic functions including speech and swallowing. Despite advancements in treatment, 5-year survival rates for mucosal malignancies remain below 70%. Effective prevention of HNSCC demands an understanding of the molecular pathways of carcinogenesis. Specifically, defining features of pre-cancerous dysplastic lesions that indicate a better or worse prognosis is necessary to help identify patients who are likely to develop a carcinoma and allow a more aggressive approach to management. There remains a need for identification of biomarkers that can provide both early prognostic and predictive value in clinical decision-making by serving as both therapeutic targets as well as predictors of therapy response. Here, we comprehensively review the most frequently altered molecular biomarkers of malignant transformation in head and neck dysplasia. These markers are involved in a wide range of cellular processes in head and neck carcinogenesis, including extracellular matrix degradation, cell motility and invasion, cell-cell adhesion, solute transport, immortalization, metabolism, the cell cycle and apoptosis, transcription, and cell signaling.

High CD44 Immunoexpression Correlates with Poor Overall Survival: Assessing the Role of Cancer Stem Cell Markers in Oral Squamous Cell Carcinoma Patients from the High-Risk Population of Pakistan

Oral squamous cell carcinoma (OSCC) is a top-ranked cancer in the Pakistani population, and patient survival has remained unchanged at ∼50% for several decades. Recent advances have claimed that a subset of tumour cells, called cancer stem cells (CSCs), are responsible for tumour progression, treatment resistance, and metastasis, which leads to a poor prognosis. This study investigated the impact of CSC markers expression on overall survival (OS) and disease-free survival (DFS) of OSCC patients. Materials and Methods. Immunohistochemistry was used to evaluate CD44, CD133, L1CAM, and SOX2 expression in a well-characterized cohort of 100 Pakistani patients with primary treatment naïve OSCC. The immunoreactivity for each marker was correlated with patient clinicopathologic characteristics, oral cancer risk chewing habits, and survival. The minimum follow-up time for all patients was five years, and survival estimates were calculated using the Kaplan–Meier method and Cox proportional hazards model. Results. In this cohort of 100 patients, there were 57 males and 43 females. The median OS and DFS time durations observed were 64 and 52.5 months, respectively. Positive expression for CD44, CD133, L1CAM, and SOX2 was observed in 33%, 23%, 41%, and 63% of patients. High CD44 expression correlated with decreased OS (P=0.047) but did not influence DFS. However, CD133, L1CAM, and SOX2 had no effect on either OS or DFS. Tonsils, nodal involvement, and AJCC stage were independent predictors of worse OS and DFS both. Conclusion. Of the CSC markers investigated here, only CD44 was a predictor for poor OS. CD44 was also associated with advanced AJCC and T stages. Interestingly, CD133 was significantly lower in patients who habitually consumed oral cancer risk factors.

Multifunctional photodynamic/photothermal nano-agents for the treatment of oral leukoplakia

Oral leukoplakia (OLK) has gained extensive attention because of the potential risk for malignant transformation. Photosensitizers (PSs) played an indispensable role in the photodynamic therapy (PDT) of OLK, but the poor light sensitivity greatly hampered its clinical application. Herein, a novel organic photosensitive ITIC-Th nanoparticles (ITIC-Th NPs) were developed for OLK photodynamic/photothermal therapy (PTT). ITIC-Th NPs present both high photothermal conversion efficiency (~ 38%) and suitable reactive oxygen species (ROS) generation ability under 660 nm laser irradiation, making them possess excellent PDT and PTT capability. In 4-nitroquinoline 1-oxide (4NQO)-induced oral precancerous animal models, ITIC-Th NPs effectively suppress the OLK's cancerization without apparent topical or systemic toxicity in vivo. This study offers a promising therapeutic strategy for PDT and PTT in OLK treatment, and this study is the first interdisciplinary research in the field of multimodal therapy for OLK.

Nucleostemin upregulation and STAT3 activation as early events in oral epithelial dysplasia progression to squamous cell carcinoma

Most low-grade oral epithelial dysplasia remains static or regress, but a significant minority of them (4-11%) advances to oral squamous cell carcinoma (OSCC) within a few years. To monitor the progression of epithelial dysplasia for early cancer detection, we investigated the expression profiles of nucleostemin (NS) and phospho-STAT3 (p-STAT3) in rodent and human samples of dysplasia and OSCCs. In a 4NQO-induced rat oral carcinogenesis model, the number and distribution of NS and p-STAT3-positive cells increased in hyperplastic, dysplastic, and neoplastic lesions compared to normal epithelium. In human samples, the NS signal significantly increased in high-grade dysplasia and poorly differentiated OSCC, whereas p-STAT3 was more ubiquitously expressed than NS and showed increased intensity in high-grade dysplasia and both well and poorly differentiated OSCC. Analyses of human dysplastic samples with longitudinally followed outcomes revealed that cells with prominent nucleolar NS signals were more abundant in low-grade dysplasia that advanced to OSCC in 2 or 3 years than those remaining static for 7-14 years. These results suggest that NS upregulation and STAT3 activation are early events in the progression of low-grade dysplasia to OSCC.

Role of cancer stem cells in head-and-neck squamous cell carcinoma - A systematic review

Targeting cancer stem cell (CSC) subpopulation within the tumor remains an obstacle for specific therapy in head-and-neck squamous cell carcinoma (HNSCC). Few studies in the literature describe a panel of stem cell makers, however a distinct panel has not been put forth. This systematic review aims to enhance the knowledge of additional markers to accurately relate their expression to tumorigenesis, metastasis, and therapy resistance. Databases, including PubMed, Google Scholar, Ebsco, and Science Direct, were searched from 2010 to 2017 using various combinations of the following keywords: “Stem cell markers in HNSCC” and “chemoresistance and radioresistence in HNSCC.” Original experimental studies (both in vitro and in vivo) published in English considering stem cell markers in HNSCC, were considered and included. We excluded articles on tumors other than HNSCC, reviews, editorial letters, book chapters, opinions, and abstracts from the analyses. Forty-two articles were included, in which 13 types of stem cell markers were identified. The most commonly expressed CSC markers were CD44, aldehyde dehydrogenase, and CD133, which were responsible for tumorigenesis, self-renewal, and therapy resistance, whereas NANOG, SOX-2, and OCT-4 were involved in metastasis and invasion. Identification of an accurate panel of CSC markers is the need of the hour as nonspecificity of the current markers poses a problem. Further studies with a large sample size would help validate the role of these CSC markers in HNSCC. These CSC proteins can be developed as therapeutic targets for HNSCC therapy, making future treatment modality more specific and effective.

Human Papilloma Virus and Cancer Stem Cell markers in Oral Epithelial Dysplasia-An Immunohistochemical Study

OBJECTIVES

To study the correlation between the putative cancer stem cell (CSC) markers aldehyde dehydrogenase 1 (ALDH1), cluster of differentiation 44 (CD44), sex-determining region Y-box 2 (SOX2), and octamer-binding protein 4 (OCT4) and human papilloma virus (HPV) infection using p16, the surrogate marker of HPV in oral epithelial dysplasia (OED) and normal mucosa.

METHODS

Five sections each from 40 histopathologically diagnosed cases of different grades of OED and 10 cases of normal oral mucosa without dysplasia were immunohistochemically stained with p16, ALDH1, CD44, SOX2, and OCT4, respectively.

RESULTS

Expression of ALDH1 and SOX2 was significantly increased in OED cases, whereas CD44 and OCT4 expression was increased in normal mucosa. P16-positive OED cases showed upregulation of ALDH1 and OCT4 expression as compared to p16-negative cases, while CD44 and SOX2 expression was downregulated in p16-positive OED cases; however, the results were not statistically significant.

CONCLUSION

The present study indicated a suggestive link between p16 and cancer stem cell marker expression in HPV-associated OED, and that p16 has a significant role in CSC progression in OED. This is the first study to evaluate the expression of putative CSC markers in HPV-associated OED. However, low study numbers are a potential limiting factor in this study.

Upregulated histone deacetylase 2 gene correlates with the progression of oral squamous cell carcinoma

BACKGROUND

Histone deacetylases (HDACs) are considered as an essential regulator of cellular proliferation, differentiation, and apoptosis. The HDAC2 enzyme of Class I HDACs plays an important role in tumor progression of human malignancies.

OBJECTIVE

The aim of the present study was to analyze the HDAC2 gene expression in pre-oral cancer and oral squamous cell carcinoma (OSCC), and its association with clinico-pathological features.

METHODS

The HDAC2 protein expression was analyzed through the immunohistochemistry and western blot techniques in 82 oral pre-malignant, 90 OSCC, and 16 normal control tissues. qRT-PCR was used to quantify the mRNA fold change in all groups.

RESULTS

The HDAC2 protein and mRNA levels were significantly higher in OSCC and pre-oral cancer groups compared to the controls. Immunostaining of HDAC2 protein was enhanced in 84.4% of OSCC and 67.1% of pre-cancerous tissue sections (p< 0.01). The mean protein level was analyzed as 1.96 ± 0.44 in oral carcinoma, 1.61 ± 0.39 in pre-cancer and 0.96 ± 0.10 in control tissues. In addition, HDAC2 mean protein level was associated with histological differentiation (OR = 25, p< 0.05) and tumor-node-metastasis (TNM) stages (OR = 6.2, p< 0.05) of OSCC patients.

CONCLUSIONS

The upregulated HDAC2 gene in pre-cancer and OSCC tissues indicates its crucial role in the transformation of pre-malignant to malignant carcinoma. It could be a potential cancer biomarker of prognosis and targeted therapy in OSCC.

World Workshop on Oral Medicine VII: Prognostic biomarkers in oral leukoplakia and proliferative verrucous leukoplakia-A systematic review of retrospective studies

OBJECTIVE

To systematically review retrospective studies examining prognostic potentials of candidate biomarkers to stratify malignant progression of oral leukoplakia (OL) and proliferative verrucous leukoplakia (PVL).

MATERIALS AND METHODS

A systematic literature search of PubMed, EMBASE, Evidence-Based Medicine and Web of Science databases targeted literature published through 29 March 2018. Inter-rater agreement was ascertained during title, abstract and full-text reviews. Eligibility evaluation and data abstraction from eligible studies were guided by predefined PICO questions and bias assessment by the Quality in Prognosis Studies tool. Reporting followed Preferred Reporting Items for Systematic Review and Meta-Analysis criteria. Biomarkers were stratified based on cancer hallmarks.

RESULTS

Eligible studies (n = 54/3,415) evaluated 109 unique biomarkers in tissue specimens from 2,762 cases (2,713 OL, 49 PVL). No biomarker achieved benchmarks for clinical application to detect malignant transformation. Inter-rater reliability was high, but 65% of included studies had high "Study Confounding" bias risk.

CONCLUSION

There was no evidence to support translation of candidate biomarkers predictive of malignant transformation of OL and PVL. Systematically designed, large, optimally controlled, collaborative, prospective and longitudinal studies with a priori-specified methods to identify, recruit, prospectively follow and test for malignant transformation are needed to enhance feasibility of prognostic biomarkers predicting malignant OL or PVL transformation.

Clinicopathological correlation of stem cell markers expression in oral squamous cell carcinoma; relation to patients` outcome

Background: Squamous cell carcinoma (OSCC) is the commonest oral malignancy.The overall 5 year survival of OSCC has remained at 50%, largely unchanged for 40 years. CSCs are important within the development, invasion, drug resistance, and prediction of carcinomas treatment outcome. ALDH1 and CD44 are commonly used epithelial tumors cancer stem-like cells surface markers. Materials: Our study aimed to judge CD44 and ALDH1 immunohistochemical expressions in 44 cases of OSCC and relates the expression to patients' survival. Results: High CD44 & ALDH1 expressions were significantly expressed in variable histologic grades of OSCCs, large sized carcinomas, presence lymph vascular invasion, presence of nodal and distant metastasis, advanced TNM clinical stage, recurrence and death during follow up period (P ≤ 0.05). Reduced DFS and three years overall survival were significantly recorded in cases with high CD44 expression, and high ALDH1 expression (p < 0.05). CD44 & ALDH1 expressions, histologic grade, tumor size were the independent predictors of DFS and three years OS. Conclusion: CD44 and ALDH1 expressions are valuable prognostic factors in OSCC and could be well considered predictors for patients' 3 years OS and DFS.

Difficulties in the Prognostic Study of Oral Leukoplakia: Standardisation Proposal of Follow-Up Parameters

Oral leukoplakia is the most prevalent potentially malignant disorder of the oral cavity. To evaluate its potential for malignancy, appropriate documentation of the biological parameters is crucial, allowing the patients' progression to be assessed. We hypothesized a lack of standardization in the parameters employed for the prognostic study of oral leukoplakia; our aims were to determine the different parameters used for follow-up according to definition, importance, and frequency of use, and to provide a standardization proposal of follow-up research. We made a scoping review to identify papers with the keywords “leukoplakia,” “oral,” and “follow-up” published until June 2019 in English, Spanish and Portuguese literature through an online search in PUBMED, SCIELO, and SCOPUS databases. In total, 514 articles were initially identified, and fifty-nine publications were selected, of which 37 were retrospective. The reports included a total of 18,660 patients between 13 and 98 years old, with a mean age of 57.6 years. Tobacco and alcohol habits were positive for 77 and 37% of the patients, respectively. Our results showed that reported leukoplakias were predominantly located on buccal mucosa (40.4%), were homogeneous (60.8%), multiple (59.9%), smaller than 2 cm (74.4%) and histopathologically non-dysplastic (71%). The mean follow-up time was 55 months, with a 13% malignant transformation rate. The categorization and definition of multiple variables were notably diverse. Age, sex, habits (tobacco and alcohol), site, size, distribution, morphology, degree of dysplasia, and evolution were the chosen parameters for our proposal. The current study reflected the lack of consensus found in the literature regarding parameters for diagnosis or follow-up, impacting negatively on clinical and research results. standardization comprises an efficient way to facilitate the prognosis assessment of oral leukoplakia, being beneficial for clinical practice, and enabling better quality information to apply in research.

Two novel cell culture models of buccal mucosal oral cancer from patients with no risk-habits of tobacco smoking or chewing

OBJECTIVE

Tobacco consumption is one of the major etiological factors for oral cancer, but it also develops in non-tobacco users, with unknown etiologies. Cellular models for tobacco associated oral cancer are available, however; reports of cellular models for studying non-tobacco associated oral cancer are limiting. We report here the establishment and characterization of two novel buccal mucosal cancer cell lines 'GBC02' and 'GBC035' derived from non-tobacco users.

MATERIALS AND METHODS

Short tandem repeats (STR) profiling, Next-generation sequencing for whole-genome, exome and copy number alterations, immunofluorescence, flow-cytometry, proliferation, live-cell chemotaxis, 3D-spheroid formation, chemotherapy response, gene-expression microarray, gene-set enrichment analysis and xenograft development were performed.

RESULTS

Sources of the established cultures were matched to their donors through STR profiling. Genome sequence analysis revealed somatic mutations in TP53, CASP8, CDKN2A for GBC02 with deletions and amplifications encompassing CDKN2A, FAT1 and CCND1, PIK3CA, SOX2, EGFR, MYC genes, respectively. GBC035 harbored mutations in FAT1, NOTCH1, HRAS, CDKN2A, HLA-B, HLA-A genes. While GBC035 cells showed higher E-Cadherin positive cell-cell junctions and collective cell migration in chemotaxis; GBC02 cells were vimentin-positive and demonstrated individual cell migration. Further, exhibiting their relevance to preclinical research, GBC02 3D-spheroids demonstrated enrichment of development-related gene-signatures in microarray transcriptome analysis and were resistant to Cisplatin, but showed sensitivity to cancer stem cells-targeting drug, Salinomycin. Additionally, tumorigenic ability of GBC02 was demonstrated.

CONCLUSIONS

Altogether, we present here comprehensively characterized unique cell lines established from non-tobacco associated tumors, which may serve as models for preclinical investigations of oral cancers caused independent of tobacco usage.

Pathophysiological relationship between hypoxia associated oxidative stress, Epithelial-mesenchymal transition, stemness acquisition and alteration of Shh/ Gli-1 axis during oral sub-mucous fibrosis and oral squamous cell carcinoma

Oral sub-mucous fibrosis (OSF) is a pathophysiological state of oral cavity or oropharynx having a high chance of conversion to oral squamous cell carcinoma (OSCC). It involves fibrotic transformation of sub-epithelial matrix along with epithelial abnormalities. The present work aims to unveil the mechanistic domain regarding OSF to OSCC conversion exploring the scenario of hypoxia associated oxidative stress, epithelial-mesenchymal transition (EMT), metastasis and stemness acquisition. The study involves histopathological analysis of the diseased condition along with the exploration of oxidative stress status, assessment of mitochondrial condition, immunohistochemical analysis of HIF-1α, E-cadherin, vimentin, ERK, ALDH-1, CD133, Shh, Gli-1 and survivin expressions in the oral epithelial region together with the quantitative approach towards collagen deposition in the sub-epithelial matrix. Oxidative stress was found to be associated with type-II EMT in case of OSF attributing the development of sub-epithelial fibrosis and type-III EMT in case of OSCC favoring malignancy associated metastasis. Moreover, the acquisition of stemness during OSCC can also be correlated with EMT. Alteration of Shh and Gli-1 expression pattern revealed the mechanistic association of hypoxia with the phenotypic plasticity and disease manifestation in case of OSF as well as OSCC. Shh/ Gli-1 signaling can also be correlated with survivin mediated cytoprotective phenomenon under oxidative stress. Overall, the study established the correlative network of hypoxia associated oxidative stress, EMT and manifestation of oral pre-cancerous and cancerous condition in a holistic approach that may throw rays of hope in the therapeutic domain of the concerned diseases.

Tissue biomarkers for predicting the risk of oral cancer in patients diagnosed with oral leukoplakia: A systematic review

OBJECTIVES

We performed a systematic review to evaluate the published biomarkers related to oral leukoplakia (OL), aiming to identify the biomarkers that indicate any future risk of cancer in patients with oral leukoplakia.

METHODS

A search strategy was developed for three main electronic databases: PubMed, Cochrane Library, and EBSCO, and also for Google Scholar, until February 28, 2020. The study selection was performed in a two-phase process aiming at studies assessing tissue biomarkers for "malignant transformation of OL." Risk of bias analysis of included studies was performed using the Quality in Prognosis Studies Tool.

RESULTS

From 3,130 articles initially identified by searching databases, a total of 46 studies were included in this systematic review, with a combined sample of 3,783 patients, of whom 1,047 presented with malignant transformation of a previously diagnosed OL as reported by the authors. The cancer incidence in the whole group was 27.6% (range: 5.4% to 54.1%). The studies were derived from different geographic areas, including Asia (n = 21), Europe (n = 15), North America (n = 9), and Oceania (n = 1). There were 49 different molecular biomarkers evaluated in the 46 included studies: p53 and podoplanin proteins were the most frequently reported, followed by abnormalities at particular chromosomal loci (e.g., LOH). Risk of bias analysis revealed concerns associated with "measurement of prognostic factor," "study confounding" and "statistical analysis and reporting."

CONCLUSIONS

Substantial heterogeneity and lack of standardized reporting of data among the studies were identified. The most promising biomarkers reported to have a significant association with the malignant transformation in OL included podoplanin and chromosomal loci abnormalities. A critical examination of the follow-up studies on OL published so far indicated that tissue biomarkers that could predict the risk of oral cancer in patients with OL are still in a discovery phase.

Biomarkers of progression to oral cancer in patients with dysplasia: A systematic review

Identifying oral dysplastic lesions with a high risk of malignant transformation may create opportunities for early therapeutic interventions. Several tissue biomarkers have been suggested to date as prognostic indicators of the progression of dysplastic lesions to oral cancer. We herein present a systematic review (PROSPERO CRD42018086476), with the aim of identifying, evaluating and summarizing evidence on prognostic biomarkers of progression to oral cancer in patients with dysplasia. A search through MEDLINE/PubMed and Scopus databases was performed. The review only included primary articles that reported risk values associated with malignancy after a multivariate analysis. The quality of the findings was analyzed using the Reporting Recommendations for Tumor Marker Prognostic Studies, and research trends were established using SciCurve Open. A total of 4 potential biomarkers were identified: Degree of dysplasia, and the proteins retinal dehydrogenase 1, prominin-1 and podoplanin. All 3 protein biomarkers have been recognized as cancer stem cell markers. The studies were of acceptable quality, although none included sample size determinations. Due to the lack of validation and follow-up studies, these biomarkers are considered to be in a discovery phase and require validation by prospective clinical trials. The present analysis indicated that there are currently insufficient data to include these biomarkers in the clinical decision-making process.

CD133 Role in Oral Carcinogenesis

Objective:

to investigate CD133 immunoexpression, cancer stem cells marker, in oral epithelial dysplasias (OEDs) and oral squamous cells carcinomas (OSCCs) and understandits possible involvement in the malignant transformation process of these lesions and to better elucidate their biological behavior.

Material and methods:

Tissue samples of 15 cases of OSCCs and 15 OEDs were subjected to CD133 antibody immunohistochemistry reactions. The analysis used quantitative parameters (number of immunostained cells regardless of immunostaining sublocations).

Results:

All samples of OSCCs and OEDs showed positive immunostaining, with no significant difference between these groups (p = 0.283). We did not observe statistical difference between the degree of dysplasia and the amount of CD133+ cells (p = 0.899). CD133 immunoexpression showed no association with the OEDs and OSCCs sites. It was observed that nuclear and cytoplasmic immunostaining was more evident with the progression of the malignant process.

Conclusion:

It is suggested that the CD133 cellular localization together with the histopathological criteria of OEDs classification can contribute to provide more concrete indications about the oral carcinogenesis process.

Oral potentially malignant disorders: A scoping review of prognostic biomarkers

This scoping review aimed to map evidence regarding biomarkers for malignant transformation of oral potentially malignant disorders (OPMD). Seventy-three longitudinal studies investigating prognostic biomarkers for OPMD malignant transformation were included, encompassing 5612 disorders and 108 biomarkers, of which 72 were investigated by immunohistochemistry. Most biomarkers were assessed in one or two studies, while five (p53, Ki-67, podoplanin, p16, and DNA ploidy) were analyzed in five or more studies. All studies investigating podoplanin (n = 8) reported a significant association between positive/high immunoexpression and malignant transformation. Similarly, all studies assessing DNA ploidy (n = 5) found that aneuploidy or gross genomic aberrations were significantly associated with malignant transformation. Included studies often presented mixed data from different OPMD subtypes, inadequate description of population characteristics, and lack of adjusted analysis for confounding factors. One hundred and eight biomarkers were identified and, from these, podoplanin immunoexpression and DNA ploidy were considered promising candidates for future long-term clinical research.

Loss of oral mucosal stem cell markers in oral submucous fibrosis and their reactivation in malignant transformation

The integrity of the basal stem cell layer is critical for epithelial homoeostasis. In this paper, we review the expression of oral mucosal stem cell markers (OM-SCMs) in oral submucous fibrosis (OSF), oral potentially malignant disorders (OPMDs) and oral squamous cell carcinoma (OSCC) to understand the role of basal cells in potentiating cancer stem cell behaviour in OSF. While the loss of basal cell clonogenicity triggers epithelial atrophy in OSF, the transition of the epithelium from atrophic to hyperplastic and eventually neoplastic involves the reactivation of basal stemness. The vacillating expression patterns of OM-SCMs confirm the role of keratins 5, 14, 19, CD44, β1-integrin, p63, sex-determining region Y box (SOX2), octamer-binding transcription factor 4 (Oct-4), c-MYC, B-cell-specific Moloney murine leukaemia virus integration site 1 (Bmi-1) and aldehyde dehydrogenase 1 (ALDH1) in OSF, OPMDs and OSCC. The downregulation of OM-SCMs in the atrophic epithelium of OSF and their upregulation during malignant transformation are illustrated with relevant literature in this review.

Advancements in Cancer Stem Cell Isolation and Characterization

Occurrence of stem cells (CSCs) in cancer is well established in last two decades. These rare cells share several properties including presence of common surface markers, stem cell markers, chemo- and radio- resistance and are highly metastatic in nature; thus, considered as valuable prognostic and therapeutic targets in cancer. However, the studies related to CSCs pave number of issues due to rare cell population and difficulties in their isolation ascribed to common stem cell marker. Various techniques including flow cytometry, laser micro-dissection, fluorescent nanodiamonds and microfluidics are used for the isolation of these rare cells. In this review, we have included the advance strategies adopted for the isolation of CSCs using above mentioned techniques. Furthermore, CSCs are primarily found in the core of the solid tumors and their microenvironment plays an important role in maintenance, self-renewal, division and tumor development. Therefore, in vivo tracking and model development become obligatory for functional studies of CSCs. Fluorescence and bioluminescence tagging has been widely used for transplantation assay and lineage tracking experiments to improve our understanding towards CSCs behaviour in their niche. Techniques such as Magnetic resonance imaging (MRI) and Positron emission tomography (PET) have proved useful for tracking of endogenous CSCs which could be helpful in their identification in clinical settings.

Different Expression of Aldehyde Dehydrogenases 1A1 and 2 in Oral Leukoplakia With Epithelial Dysplasia and in Oral Squamous Cell Carcinoma

Oral potentially malignant disorders (OPMD) may develop malignant characteristics and transform into oral squamous cell carcinoma (OSCC) in a range of 1% to 2% of cases. Chronic alcohol consumption is associated with carcinogenesis, but its mechanism has not yet been fully elucidated. ALDH1A1 and 2, isoenzymes responsible for aldehyde oxidation involved in ethanol metabolism may be associated with the development of malignant head and neck neoplasms. The aim of this study was to analyze the expression of ALDH1A1 and ALDH2 in oral leukoplakia with epithelial dysplasia (OLP) and OSCC. A retrospective study was conducted on 27 cases of OLP and 30 cases of OSCC. Clinical data were obtained from medical records, and all cases were classified as mild, moderate, and severe for OLP, and well-differentiated, moderately differentiated, or poorly differentiated for OSCC cases. The ALDH1A1 and ALDH2 expression in OLP and OSCC was evaluated by the immunohistochemical technique. There was predominance of the male sex, in both OLP and OSCC cases. Oral tongue was the most affected site in both groups. OLP showed positive protein expression of ALDH1A1 in all cases, both basal and suprabasal epithelial layers, whereas ALDH2 showed less protein expression. In OSCC, the immunohistochemical reaction for ALDH1A1 expression was negative in 70%, whereas ALDH2 expression was positive in all cases. This study demonstrated the gradual loss of ALDH1A1 expression in OSCC in comparison with OLP, and the increased ALDH2 expression in OSCC.

Cancer stem cells: A comprehensive review on identification and therapeutic implications

Cancer stem cells (CSCs) are distinct subpopulations of tumor cells that possess the ability for perpetual self-renewal and proliferation. They produce downstream progenitor cells and cancer cells that drive tumor growth. Studies of many cancer types including oral squamous cell carcinoma (OSCC) have identified CSCs using specific markers, but it is still unclear as to where in the stem cell hierarchy these markers fall. This is compounded further by the presence of multiple CSC subtypes within OSCC, making investigation reliant on the use of multiple markers. This review paper focuses on the current knowledge in CSC markers including OCT4, SOX2, NANOG, aldehyde dehydrogenase 1, CD44, CD24, CD133 and Musashi-1, highlighting their use and validity in OSCC CSC research.

Identification, characterization and microRNA expression profiling of side population cells in human oral squamous cell carcinoma Tca8113 cell lines

The present study aimed to evaluate the stem cell markers, characteristics and biological functions of cancer stem-like side population (SP) cells in human oral cancer. SP cells were isolated from the human oral squamous cell carcinoma Tca8113 cell line by Hoechst 33342 fluorescence dye and flow cytometry. The colony forming and proliferative capability of SP and non-SP cells were detected using a live-cell analysis system in vitro. The number of cells expressing stem cell markers was compared between SP cells and non-SP cells by flow cytometry. Reverse transcription-quantitative polymerase chain reaction and western blotting were used to detect the mRNA and protein expression levels of stem cell genes, respectively. Differential expression of microRNAs (miRNAs) in SP and non-SP cells was determined by microarray hybridization and an miRNA regulation network was produced. With regard to the proliferation capability, SP cells reached 60.0% confluence after 40 h of growth compared with 35.1% confluence for non-SP cells (P<0.05). The number of colonies in SP cells was 43.1±9.2 compared with 33.0±8.2 of non-SP cells (P<0.05). The aldehyde dehydrogenase-1 (ALDH1)-positive cell number in the SP cells was increased by 10 times compared with the non-SP cells (P<0.01). The mRNA and protein expression levels of ALDH1, SRY-box 2, POU class 5 homeobox 1 and Nanog homeobox in SP cells were significantly higher compared with non-SP cells (P<0.05). Microarray hybridization demonstrated that 21 miRNAs were upregulated and 13 miRNAs were downregulated in SP cells compared with non-SP cells. SP cells in Tca8113 demonstrated greater capability of proliferation and colony formation compared with non-SP cells in vitro. Stem cell markers were overexpressed in SP cells compared with non-SP cells.

The current markers of cancer stem cell in oral cancers

Head and neck cancer (HNC) constitute 5% of all reported cancers. Among all, the oral cavity cancer is the most frequent type of HNC which accounts for over half of HNC cases. Mouth cancer ranks the sixth leading cause of cancer-related mortality. Generally, conventional chemotherapy has shown success at decreasing relapse and metastasis rates and improves the overall prognosis. Recently, target therapy and targeted drug delivery systems have been introduced as promising treatments. The elimination of efficiency of current therapeutic strategies due to the spared cancer stem cells that cause chemotherapy resistance, relapse and metastasis. Inefficiency methodologies in the elimination of all cancer cells in the body are a major problem that remained to be resolved before to confront the new cancer therapies. Many studies imply to cancer stem cell markers as important agents for targeted anti-cancer as well as improving chemotherapy efficiencies. The potentials of targeted cancer therapy led us to search for novel markers in the mouth cancer stem cells especially in rare cancers. The aimed of this research was, first a comprehensive critical review of the previous studies on the markers of cancer stem cells in oral cancers including oral squamous cell carcinoma, salivary gland cancers, and to highlight the most common cancer stem cell markers which have potential to be exploited as indicators for the preneoplastic lesion malignancy, oral cancer progression, and/or treatment prognosis.

Prognostic Significance of ALDH1, Bmi1, and OCT4 Expression in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma

BACKGROUND

Increasing evidence suggests the involvement of cancer stem cells (CSCs) in both oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Among the various CSC markers, aldehyde dehydrogenase (ALDH) 1, B cell-specific Moloney murine leukaemia virus integration site 1 (Bmi1), and octamer-binding protein 4 (OCT4) have been noted to increase in OSCC. The aim of the study was to analyze ALDH1, Bmi1, and OCT4 expression in OED and OSCC with clinicopathologic correlation and survival analysis.

METHODS

A total of 40 cases each of OED and OSCC were retrieved from departmental archives. Expression of ALDH1, Bmi1, and OCT4 was analyzed using immunohistochemistry and was correlated with clinicopathological parameters. A follow-up ranging from 6 to 52 months was considered for Kaplan-Meier survival analysis. The log-rank test was performed to analyze significant difference in survival rates.

RESULTS

The expression levels of ALDH1, Bmi1, and OCT4 increased significantly from OED through OSCC (P < .05). The expression of ALDH1 and OCT4 showed a significant correlation with lymph node metastasis. Positive cases of ALDH1 showed a significantly reduced survival rate compared to cases showing negative expression. Kaplan-Meier survival analysis showed a significant reduction of survival rate (P = .00) in patients showing a positive expression for all the 3 markers.

CONCLUSION

ALDH1 and OCT4 could be used as individual prognostic markers for assessing prognosis. ALDH1, Bmi1, and OCT4 could be used as a collective panel of markers to enable surgeons in predicting the prognosis of patients and thereby carry out prompt follow-up for such cases.

Assessment of cancer stem cell marker expression in primary head and neck squamous cell carcinoma shows prognostic value for aldehyde dehydrogenase (ALDH1A1)

Cancer stem cells (CSCs) play a key role in carcinogenesis and progression of head and neck squamous cell carcinomas (HNSCC). The most common markers indicating for CSCs are: CD44, CD24, CD133, ALDH1A1. Our objective was to evaluate the prognostic potential of CSC markers in HNSCC. The study included 49 patients treated for primary HNSCC, 11 patients with upper respiratory tract epithelial dysplasia and 12 subjects with the normal pharyngeal mucosa as a control group. The frequency and expression levels of the four CSC markers were assessed by immunohistochemistry. Univariate and multivariate analyses were used to correlate CSC expression levels with tumor stage, lymph node metastases or overall survival (OS). CD44, CD24, CD133, ALDH1A1 were widely expressed in tumors, whereas CD44 was found to be higher in cancer tissue (P = 0.001). ALDH1A1 expression levels were found to be significantly higher in T3-T4 tumors vs. T1-T2 tumors (P = 0.05). Lymph node metastases had significantly higher expression levels of CD24 (P = 0.01) and CD133 (P < 0.05) than primary tumors. Multifactorial analysis revealed that overall survival (OS) for patients with ALDH1A1 negative tumors was 5.25 times higher than for patients with ALDH1A1 positive (ALDH1A1+) tumors (P = 0.01). On univariate and multivariate analysis, only ALDH1A1 positivity had a significant effect on OS of HNSCC patients (HR = 2.47 for P = 0.02). Immunohistochemistry-based assessments of CSC marker expression in HNSCC has significant predictive implications for patients with HNSCC. The frequency of CSCs in the tumor, specifically of ALDH1A1+ cells correlated with five-year OS in these patients.

Recent trends in predictive biomarkers for determining malignant potential of oral potentially malignant disorders

Despite of the tremendous advancements in the field of cancer prevention, detection and treatment, the overall prognosis of oral squamous cell carcinoma (OSCC) still remains poor. This can be partly imparted to the lack of early detection of oral potentially malignant disorders (OPMDs), especially those at a higher risk of progression into OSCC. Over years, various specific and non-specific markers have been introduced that could predict the malignant transformation of OPMDs; however detail information on these OPMD markers in a concise manner is lacking. Moreover, their use on daily clinical basis still remains questionable. With continuous research in the field of cytology and genomics, several contemporary biomarkers have been discovered that are not yet foregrounded and proved to be more promising than those used conventionally. Here, in the present paper, we overview several recently concluded predictive biomarkers with special emphasis on their role in molecular pathogenesis of OSCC transformation. These markers can be used for risk assessment of malignant transformation in patients with OPMDs as well as for prophylactic conciliation and fair management of the high-risk OPMD patient group.

A subtype of cancer-associated fibroblasts with lower expression of alpha-smooth muscle actin suppresses stemness through BMP4 in oral carcinoma

Cancer-associated fibroblasts (CAFs) demonstrate the characteristics of myofibroblast differentiation by often expressing the ultrastructure of alpha-smooth muscle actin (αSMA). However, heterogeneity among cancer-associated fibroblasts (CAFs), with respect to αSMA expression, has been demonstrated in several clinical studies of oral cancer. Like normal stem cells, stem-like cancer cells (SLCCs) are also regulated extrinsically by its microenvironment; therefore, we postulated that the heterogeneous oral-CAFs would differently regulate oral-SLCCs. Using transcriptomics, we clearly demonstrated that the gene expression differences between oral tumor-derived CAFs were indeed the molecular basis of heterogeneity. This also grouped these CAFs in two distinct clusters, which were named as C1 and C2. Interestingly, the oral-CAFs belonging to C1 or C2 clusters showed low or high αSMA-score, respectively. Our data with tumor tissues and in vitro co-culture experiments interestingly demonstrated a negative correlation between αSMA-score and cell proliferation, whereas, the frequency of oral-SLCCs was significantly positively correlated with αSMA-score. The oral-CAF-subtype with lower score for αSMA (C1-type CAFs) was more supportive for cell proliferation but suppressive for the self-renewal growth of oral-SLCCs. Further, we found the determining role of BMP4 in C1-type CAFs-mediated suppression of self-renewal of oral-SLCCs. Overall, we have discovered an unexplored interaction between CAFs with lower-αSMA expression and SLCCs in oral tumors and provided the first evidence about the involvement of CAF-expressed BMP4 in regulation of self-renewal of oral-SLCCs.

Expression of DNA doublestrand repair proteins in oral leukoplakia and the risk of malignant transformation

The present study assessed the expression of the DNA doublestrand repair (DDR) proteins ATM serine/threonine kinase (ATM), checkpoint kinase 2 (CHEK2) and γH2A histone family member X (γH2AFX) in oral leukoplakia (OL) and evaluated their clinical significance and usefulness as biomarkers for predicting OL transformation. Retrospectively, ATM, CHEK2 and γH2AFX protein levels were evaluated using immunohistochemical analysis in 61 OL, 33 oral squamous cell carcinoma (OSCC) and 15 normal oral mucosa tissues. OL tissues were classified into two groups according to the epithelial dysplasia pathology: The low risk dysplasia group (n=41) and the high-risk dysplasia group (n=20). The results of the present study revealed that the expression of ATM and γH2AFX in OSCC was significantly increased compared with that in OL with low-risk dysplasia and normal oral mucosa tissues. There was no statistically significant difference in CHEK2 expression among the groups. ATM expression was correlated with that of γH2AFX in OSCC tissue. The prognostic values of the DDR proteins and their correlation with clinical and pathological parameters were evaluated further in 99 OL patients with low risk dysplasia. Multivariate analysis revealed that increased expression of ATM and γH2AFX was significantly associated with an increased risk of malignant transformation. Immunohistochemical analysis of ATM and γH2AFX protein expression provided useful prognostic information on the carcinogenesis of OL. Increased ATM and γH2AFX expression may indicate a poor prognosis.

Tumor microenvironment - Unknown niche with powerful therapeutic potential

Head and neck squamous cell carcinomas (HNSCC) are in a group of cancers that are the most resistant to treatment. The survival rate of HNSCC patients has been still very low since last 20 years. The existence of relationship between oncogenic and surrounding cells is probably the reason for a poor response to treatment. Fibroblasts are an important element of tumor stroma which increases tumor cells ability to proliferate. Another highly resistance, tumorigenic and metastatic cell population in tumor microenvironment are cancer initiating cells (CICs). The population of cancer initiating cells can be found regardless of differentiation status of cancer and they seem to be crucial for HNSCC development. In this review, we describe the current state of knowledge about HNSCC biological and physiological tumor microenvironment.

Aldehyde dehydrogenase 1 isoenzyme expression as a marker of cancer stem cells correlates to histopathological features in head and neck cancer: A meta-analysis

There is a lack of predictive biomarkers that can identify patients with head and neck squamous cell carcinoma (HNSCC) who will experience treatment failure and develop drug resistance, recurrence, and metastases. Cancer stem-like cells (CSC) were identified as a subset of cells within the tumor in a variety of solid tumors including HNSCC. CSC are considered the tumor-initiating population responsible for recurrence or metastasis and are associated with therapy resistance. This meta-analysis including fourteen studies with altogether 1258 patients updates and summarizes all relevant data on the impact of ALDH1⁺ CSC on the prognosis of HNSCC and its association with clinicopathological parameters. ALDH1 expression is highly correlated with tumor differentiation (G3 vs. G1+G2; odds ratio = 2.85. 95% CI: 1.72–4.73, P<0.0001) and decreased overall survival (relative risk = 1.77. 95% CI: 1.41–2.22, P<0.0001) if one out of seven studies was excluded because of heterogeneity. These findings provide insights into the understanding of more aggressive tumor phenotypes and also suggest that the prognostic value provided by HNSCC-subtyping by CSC frequency warrant further clinical investigation.

Lentivirus-mediated RNA interference inhibits the tumorigenicity of cluster of differentiation 44+ tumor cells in hypopharyngeal cancer

The present study aimed to investigate whether the inhibition of cluster of differentiation (CD)44 expression reduces the tumorigenicity of CD44⁺ cancer stem cells in hypopharyngeal cancer. To assess this, effective recombinant CD44 short hairpin RNA-expressing lentiviruses were produced. Lentivirus-mediated RNA interference (RNAi) was then used to knockdown CD44 gene expression in the hypopharyngeal cancer FaDu cell line. The viability of FaDu cells in the two control groups and the RNAi group (RNAi-CD44 lentiviral vector) was detected using an MTT assay in vitro. Cells from each group were injected into non-obese diabetic/severe combined immunodeficiency mice and their tumorigenicity determined in vivo. Following lentivirus-mediated RNAi, an MTT assay indicated that cells from the RNAi group exhibited lower viability than the control group. The in vivo tumorigenicity study further revealed a significant difference in tumorigenic rates between the RNAi group and the control group (Fisher's exact test, P<0.05). In addition, tumors in the RNAi group of animals had a longer incubation period than those in the control groups, and the mean tumor volume was also significantly smaller (t=3.47, P<0.05). Pathological study confirmed that all tumors were poorly differentiated squamous cell carcinomas with cellular heterogeneity. The viability of the hypopharyngeal cancer FaDu cells in vitro and their tumorigenicity in vivo were markedly inhibited once CD44 was knocked down. The results of the present study therefore suggest that CD44 may confer tumorigenic characteristics upon CD44⁺ cancer stem cells in hypopharyngeal cancer.

Cancer Stem Cells in Oral Cavity Squamous Cell Carcinoma: A Review

Cancer stem cells (CSCs) have been identified in oral cavity squamous cell carcinoma (OCSCC). CSCs possess the ability for perpetual self-renewal and proliferation, producing downstream progenitor cells and cancer cells that drive tumor growth. Studies of many cancer types including OCSCC have identified CSCs using specific markers, but it is still unclear as to where in the stem cell hierarchy these markers fall. This is compounded further by the presence of multiple CSC subtypes within OCSCC, making investigation reliant on the use of multiple markers. This review examines the current knowledge in CSC markers OCT4, SOX2, NANOG, ALDH1, phosphorylated STAT3, CD44, CD24, CD133, and Musashi-1, specifically focusing on their use and validity in OCSCC CSC research and how they may be organized into the CSC hierarchy. OCSCC CSCs also express components of the renin–angiotensin system (RAS), which suggests CSCs may be novel therapeutic targets by modulation of the RAS using existing medications.

[Clinical significance of CD44 and CD133 expression in oral potentially malignant disorder and oral squamous cell carcinoma]

OBJECTIVE

This study aims to investigate the expression and relationship of CD44 and CD133 in normal oral mucosa, oral potentially malignant disorder (OPMD), and oral squamous cell carcinoma (OSCC). This work also analyzes the relationship between such expression and clinical factors. This study intends to evaluate the clinical value of using CD44 and CD133 as indices to evaluate the carcinogenic potential of OPMD.

METHODS

Clinical data from 60 patients with OPMD, 60 patients with OSCC, and 10 cases of normal oral mucosa were analyzed. Double immunohistochemical analysis was applied to investigate the expression of CD44 and CD133 in paraffin sections of normal oral mucosa, OPMD, and OSCC tissues. Subsequently, the relationships between such expression and clinical factors were analyzed.

RESULTS

The positive rates of CD44 expression in the normal oral mucosa, OPMD, and OSCC tissues were 100.00%, 96.67%, and 71.67% (P<0.05), respectively. Meanwhile, the positive rates of CD133 expression in the normal oral mucosa, OPMD, and OSCC tissues were 0.00%, 35.00%, and 63.33% (P<0.05), respectively. The expression of CD44 and CD133 was found to be correlated (P<0.05). Such expression was related to the clinical stages and lymphatic metastasis of OSCC (P<0.05).

CONCLUSIONS

CD44 and CD133 can be used individually as clinical indices to evaluate the carcinogenic potential of OPMD.
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ALDH1 and podoplanin expression patterns predict the risk of malignant transformation in oral leukoplakia

Oral leukoplakia (OL) is a clinically diagnosed preneoplastic lesion of the oral cavity with an increased oral cancer risk. However, the risk of malignant transformation is still difficult to assess. The objective of the present study was to examine the expression patterns of aldehyde dehydrogenase 1 (ALDH1) and podoplanin in OL, and to determine their roles in predicting oral cancer development. In the present study, the expression patterns of ALDH1 and podoplanin were determined in samples from 79 patients with OL. The association between protein expression and clinicopathological parameters, including oral cancer-free survival, was analyzed during a mean follow-up period of 3.4 years. Expression of ALDH1 and podoplanin was observed in 61 and 67% patients, respectively. Kaplan-Meier analysis demonstrated that the expression of the proteins was correlated with the risk of progression to oral cancer. Multivariate analysis revealed that expression of ALDH1 and podoplanin was associated with 3.02- and 2.62-fold increased risk of malignant transformation, respectively. The malignant transformation risk of OL was considerably higher in cases with expression of both proteins. Point-prevalence analysis revealed that 66% of patients with co-expression of ALDH1 and podoplanin developed oral cancer. Taken together, our data indicate that ALDH1 and podoplanin expression patterns in OL are associated with oral cancer development, suggesting that ALDH1 and podoplanin may be useful biomarkers to identify OL patients with a substantially high oral cancer risk.

Identification, expansion and characterization of cancer cells with stem cell properties from head and neck squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) is a major public health concern. Recent data indicate the presence of cancer stem cells (CSC) in many solid tumors, including HNSCC. Here, we assessed the stem cell (SC) characteristics, including cell surface markers, radioresistance, chromosomal instability, and in vivo tumorigenic capacity of CSC isolated from HNSCC patient specimens. We show that spheroid enrichment of CSC from early and short-term HNSCC cell cultures was associated with increased expression of CD44, CD133, SOX2 and BMI1 compared with normal oral epithelial cells. On immunophenotyping, five of 12 SC/CSC markers were homogenously expressed in all tumor cultures, while one of 12 was negative, four of 12 showed variable expression, and two of the 12 were expressed heterogeneously. We showed that irradiated CSCs survived and retained their self-renewal capacity across different ionizing radiation (IR) regimens. Fluorescence in situ hybridization (FISH) analyses of parental and clonally-derived tumor cells revealed different chromosome copy numbers from cell to cell, suggesting the presence of chromosomal instability in HNSCC CSC. Further, our in vitro and in vivo mouse engraftment studies suggest that CD44+/CD66- is a promising, consistent biomarker combination for HNSCC CSC. Overall, our findings add further evidence to the proposed role of HNSCC CSCs in therapeutic resistance.

Identification and Characterization of CD133(pos) Subpopulation Cells From a Human Laryngeal Cancer Cell Line

Background

Recent research indicates that CD133 are expressed in several kinds of stem cells, among which, its high expression in laryngeal carcinoma has caused wide concern. To further explore efficaciously targeting drugs to laryngeal carcinoma stem cells (CSCs), we transplanted a solid tumor from CSCs into abdominal subcutaneous tissue of nude mice, and then compared the biological characteristics of laryngeal solid tumors with or without cisplatin intervention.

Material/Methods

In this study, the expression of CD133 was detected in the Hep-2 cell line by flow cytometry. By applying magnetic cell sorting (MACS) technology, we reported the results of purifying CD133-positive cells from a Hep-2 cell line. Cell proliferation, colony formation, and tumor-forming ability were examined in vitro and in vivo to identify the marker of CSCs in Hep-2 cell line.

Results

Upon flow cytometry analysis, CD133 was expressed constantly on 40.12±1.32% in Hep-2 cell line. Cell proliferation and colony formation ability were higher in CD133-positive cells compared to CD133-negative cells, and the in vivo tumorigenesis experiment showed the same results as in vitro assay. The 2 subpopulations cells were both sensitive to DDP, among which, the effect of DPP on proliferation ability and tumor-forming ability of CD133-positive cells was obviously greater than that of CD133-negative cells.

Conclusions

Above all, our study revealed that CD133-positive cells have properties of higher proliferation, colony formation, and tumorigenesis in Hep-2 cell line, indicating that CD133 could be a marker to characterize laryngeal cancer stem cells.

The prognostic role of the cancer stem cell marker aldehyde dehydrogenase 1 in head and neck squamous cell carcinomas: a meta-analysis

OBJECTIVE

This study aimed to investigate the correlation between aldehyde dehydrogenase 1 (ALDH1)-positive head and neck squamous cell carcinomas (HNSCC) and clinicopathological features and its effect on survival. A meta-analysis based on published studies was conducted to accurately evaluate the association between the presence of cancer stem cells (CSCs) in clinical samples and clinical outcome.

METHODS

A search in the PubMed, EMBASE, and Wanfang databases (up to May 1, 2014) was conducted. Publications assessing the clinical or prognostic significance of ALDH1 expression in HNSCC were identified and reviewed until May 1, 2014. A meta-analysis was performed to clarify the association between ALDH1 expression and clinical outcomes.

RESULTS

A total of 9 publications satisfied the criteria and comprised 749 cases. ALDH1 expression was not significantly associated with tumor T stage [I+II vs. III+IV; odds ratio (OR)=1.23, 95% confidence interval (CI)=0.70-2.15, P=0.48]. However, in the identified studies, ALDH1 expression was highly correlated with tumor differentiation (G1+G2 vs. G3; OR=3.30, 95% CI=1.92-5.67, P<0.001), lymph node metastasis (OR=4.07, 95% CI=1.18-14.10, P=0.03), decreased overall survival [relative risk (RR)=1.84, 95% CI=1.43-2.36, P<0.0001], and decreased disease-free survival (RR=2.34, 95% CI=1.37-4.00, P=0.002).

CONCLUSION

ALDH1-positive HNSCC patients had worse prognosis, which was associated with common clinicopathological features and poor prognostic factors.

Expression of cancer stem cell marker during 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis

One of the theories regarding oral carcinogenesis is that the tumor growth is initiated from cancer stem cells (CSCs) that self-renew and give rise to differentiated tumor cells, like stem cells do in normal tissues. The most common methods of CSC identification are based on CSC marker expression in carcinogenesis. This study examined the expression of CD133 and CD44, the most commonly used CSC biomarkers in oral squamous cell sarcoma (SCC), with the goal of identifying molecular biomarkers whose expression is associated with the multistep oral carcinogenesis. The expression of CD133, CD44, proliferating cell nuclear antigen (PCNA), and Cytokeratin (CK) was examined by Western blot analysis and confirmed by immunohistochemistry in a 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis model. Also, the expression of aldehyde dehydrogenase 1 (ALDH1), OCT-4 and Nanog were investigated for alteration of cancer cell stemness by Western blot. Along with the progress of multistep carcinogenesis, there were slight increases of CD133 and CD44 expression in the dysplasia group compared with normal rats. However, CD133 protein level was significantly overexpressed in SCC. The expression of PCNA and CK were low in normal group, but sequentially increased in SCC. ALDH1, Nanog and OCT-4 expression were significantly increased according to SCC grade during carcinogenesis. The findings indicate that CD133 is useful in identifying oral CSCs, which suggests that CD133 may serve as a predictor to identify CSCs with a high risk of oral cancer development.