Expression of stem cell markers in oral cavity and oropharynx squamous cell carcinoma

Study on Tumor Budding and Immunoexpression of Cancer Stem Cell Marker ALDH1 in Oral Squamous Cell Carcinoma

Background Tumor budding refers to the presence of individual cancer cells or small clusters of cells that break away from the main tumor and are seen at the edge where the tumor is invading surrounding tissue. Aldehyde dehydrogenase 1 is a cancer stem cell marker that causes oxidation of retinol to retinoic acid in early stem cell differentiation. This study aimed to examine tumor budding in oral squamous cell carcinoma and explore how it relates to various clinical and pathological factors. A study of cancer stem cell marker ALDH1 was also done with correlation to tumor budding and prognostic markers. Material and methods A prospective study was carried out in a pathology department over one year and included all newly diagnosed cases of oral squamous cell carcinoma that had undergone surgical resection. Both the gross specimens and the tissue sections stained with hematoxylin and eosin (H&E) from paraffin-embedded samples were examined for tumor size, histopathological grade, in situ carcinoma, necrosis, lymphovascular emboli, perineurial invasion, and lymph node metastasis. Tumor budding was evaluated for every case by observing tumor buds (clusters of a single tumor cell or a small cluster of tumor cells (<5) at the invasive front of the tumor) at 40x. Immunohistochemical analysis for ALDH-1 was performed on paraffin-embedded histopathological sections. Results A total of 50 cases were included in the study, with a mean age of 49 years and a male-to-female ratio of 7.3:1. The most common site of carcinoma was buccal mucosa (34%), followed by tongue (30%). Ninety percent (90%) of cases were moderately differentiated squamous cell carcinoma, with 82% of cases showing lymphovascular emboli and 32% showing perineural invasion. The highest number of cases, 22% (11), were classified as pT4aN0Mx, followed by 16% (8 cases each) classified as pT2N0Mx and pT3N0Mx. Sixty-six percent (66%; n=33) of cases showed high-grade tumor budding while 34% (n=17) showed low-grade tumor budding. Eighty-eight point eight percent (88.8%; n=32) of cases with high-grade tumor budding as well as lymphovascular invasion were observed with a statistically significant association (p=0.042). The study found a statistically significant link between high-grade tumor budding and the presence of lymph node metastasis (p=0.003). Fifty-eight percent (58%) of cases showed positive immunostaining of ALDH1 with varying intensity from weak to strongly positive. ALDH1 expression showed a significant association with high-grade tumor budding, with the result being statistically highly significant (p = 0.0001). Conclusion High-grade tumor budding is associated with increased expression of cancer stem cell marker ALDH1 in oral squamous cell carcinoma. It is also associated with lymphovascular invasion and lymph node metastasis, suggesting a poor prognosis in these patients. It is recommended that tumor budding should be included in histopathological reports of oral carcinoma. ALDH1 may be explored as a potential target for therapy in oral carcinoma. The authors suggest that further larger studies with extended follow-up may be done to establish the role of tumor budding and ALDH1 in the prognosis of oral carcinoma.

Prognostic effect of programmed cell death ligand 1/programmed cell death 1 expression in cancer stem cells of human oral squamous cell carcinoma

The relationship between cancer stem cells (CSCs) in oral squamous cell carcinoma (OSCC) and programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) remains unclear. Therefore, the present study aimed to clarify the association between the CD44v3high/CD24low immunophenotype of CSCs in OSCC and PD-L1/PD-1 co-expression, and to assess the prognostic effect of CSCs in terms of immune checkpoint molecules. Formalin-fixed, paraffin-embedded tissue samples and clinicopathological data from 168 patients with OSCC were retrospectively retrieved. Immunohistochemical staining and reverse transcription quantitative polymerase chain reaction were applied to a tissue microarray of the invasive front of each case. Semi-automated cell counting was used to assess CD44v3, CD24, PD-L1 and PD-1 expression by immunohistochemistry (IHC) using a digital image analysis program. Associations between immunological markers and clinicopathological variables were estimated. Patients with the CSC immunophenotype CD44v3high/CD24low, and patients with a high PD-L1/PD-1-positive cell density in the tumor parenchyma and stroma had significantly lower survival rates. Furthermore, patients with the CSC immunophenotype (CD44v3high/CD24low) and high PD-L1/PD-1 co-expression had even lower survival rates (P<0.01, log-rank test). Notably, there was a positive correlation between CD44v3 and PD-L1 expression (τ=0.1096, P=0.0366, Kendall rank correlation coefficient) and a negative correlation between CD24 and PD-1 expression (τ=-0.1387, P=0.0089, Kendall rank correlation coefficient). Additionally, the high CD44v3 expression group, as determined by IHC, exhibited significantly decreased expression of U2 small nuclear RNA auxiliary factor 1 (U2AF1) at the mRNA level compared with that in the low CD44v3 expression group (P<0.001, Mann-Whitney U test), and U2AF1 and PD-L1 mRNA expression exhibited a significant negative correlation (τ=-0.3948, P<0.001, Kendall rank correlation coefficient). In conclusion, CSCs in OSCC may evade host immune mechanisms and maintain CSC stemness via PD-L1/PD-1 co-expression, resulting in unfavorable clinical outcomes.

Recent Advances in the Targeting of Head and Neck Cancer Stem Cells

Head and neck squamous cell carcinoma (HNSCC) is a very heterogeneous cancer with a poor overall response to therapy. One of the reasons for this therapy resistance could be cancer stem cells (CSCs), a small population of cancer cells with self-renewal and tumor-initiating abilities. Tumor cell heterogeneity represents hurdles for therapeutic elimination of CSCs. Different signaling pathway activations, such as Wnt, Notch, and Sonic-Hedgehog (SHh) pathways, lead to the expression of several cancer stem factors that enable the maintenance of CSC features. Identification and isolation of CSCs are based either on markers (CD133, CD44, and aldehyde dehydrogenase (ALDH)), side populations, or their sphere-forming ability. A key challenge in cancer therapy targeting CSCs is overcoming chemotherapy and radiotherapy resistance. However, in novel therapies, various approaches are being employed to address this hurdle such as targeting cell surface markers, other stem cell markers, and different signaling or metabolic pathways, but also, introducing checkpoint inhibitors and natural compounds into the therapy can be beneficial.

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.

Expression of CD44 in Head and Neck Squamous Cell Carcinoma-An In-Silico Study

Introduction  CD44, a multistructural and multifunctional transmembrane glycoprotein, is a promising cancer stem cell (CSC) marker that regulates the properties of CSCs, including self-renewal, tumor initiation, and metastasis, and confers resistance to chemotherapy and radiotherapy. The aim of the present study was to evaluate the gene and protein expression of CD44 and explore its prognostic value in head and neck squamous cell carcinoma (HNSCC). Methodology  The present observational study employs computational tools for analysis. The Cancer Genome Atlas Head-Neck Squamous Cell Carcinoma dataset (520 primary HNSCC and 44 normal tissues) from the University of Alabama at Birmingham Cancer platform was used to study the association of CD44 mRNA transcript levels with various clinicopathological characteristics of HNSCC including age, gender, tumor grade, tumor stage, human papillomavirus (HPV) status, p53 mutation status, and overall survival. The CD44 protein expression in HNSCC and normal tissues was ascertained using the National Cancer Institute's Clinical Proteomic Tumor Analysis Consortium Head-and-Neck cancer dataset (108 primary HNSCC and 71 normal tissues). Results  CD44 mRNA transcript and protein expression levels were significantly higher in HNSCC tissues than in normal tissues, and high CD44 expression was correlated with poor survival. CD44 was upregulated in Stage 1 and Grade 2 HNSCC compared with other stages and grades. Overexpression of CD44 was observed in HPV-negative and TP53-positive mutant status in HNSCC. Conclusion  The pleiotropic roles of CD44 in tumorigenesis urge the need to explore its differential expression in HNSCC. The study concludes that CD44 can be a potential diagnostic and prognostic biomarker for HNSCC and offer new molecular targets for CD44-targeted therapy for cancer management.

Utility of CD44/CD24 in the Outcome and Prognosis of Oral Squamous Cell Carcinoma: A Systematic Review

Cancer stem cells (CSCs) are characterized by their capacity for self-renewal and differentiation. CD44 and CD24 are two commonly used markers to identify these CSCs. Despite the enormous amount of data available in the literature, their specificity and coexistence remain elusive in oral squamous cell carcinoma (OSCC). In the present review, we aimed to assess the diagnostic utility of the CD44/CD24 combination in tumor development and metastasis in OSCC. Two investigators independently performed a systematic search to identify all the relevant studies from various electronic databases. Out of 694 articles, 9 were found eligible for further evaluation. Details including the number of patients, gender, site, tobacco and alcohol consumption, histological stage, CD24 expression, CD44 expression, CD44/CD24 expression, nodal status, disease-free survival, and overall survival were extracted. CD44+CD24- expression was noted in 35/207 (16.9%) cases, CD44+CD24+ in 53/207 (25.6%) cases, CD44-CD24- in 49/207 subjects (23.67%), and CD44-/CD24+ in 70/207 (33.81%) cases. CD44 or CD24 or their co-expression did not correlate with the disease-free survival rate, and double negatives (CD44-/CD24-) demonstrated a higher overall survival than other immunotypes. CD44/CD24 profile may be used on small incisional biopsies to predict the outcome and treatment planning. This finding may help in developing new therapeutic targets to suppress cancer metastasis and provide a better long-term prognosis for patients diagnosed with OSCC.

Can Immunoexpression of Cancer Stem Cell Markers Prognosticate Tongue Squamous Cell Carcinoma? A Systematic Review and Meta-Analysis

The objective was to evaluate the association of the immunoexpression of cancer stem cell (CSC) markers with clinicopathological and survival outcomes in tongue squamous cell carcinoma (TSCC) patients. This systematic review and meta-analysis [PROSPERO (CRD42021226791)] included observational studies that compared the association of clinicopathological and survival outcomes with CSC immunoexpression in TSCC patients. Pooled odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CI) were used as outcome measures. Six studies identified the association with three surface markers (c-MET, STAT3, CD44) and four transcription markers (NANOG, OCT4, BMI, SOX2). The odds of early-stage presentation were 41% (OR = 0.59, 95% CI 0.42-0.83) and 75% (OR = 0.25; 95% CI 0.14-0.45) lower in CSC and SOX2 immuno-positive cases than immuno-negative cases, respectively. The odds of well-differentiated tumors in transcription marker immuno-positive cases were 45% lower compared to immuno-negative cases (OR = 0.55, 95% CI 0.32-0.96). The odds of positive lymph nodes were 2.01 times higher in CSC immuno-positive cases compared to immuno-negative cases (OR = 2.01, 95% CI 1.11-3.65). Mortality in immuno-positive cases was 121% higher than that in immuno-negative cases (HR = 2.21; 95% CI 1.16-4.21). Advanced tumor staging and grading, lymph node metastasis, and mortality were significantly associated with positive immunoexpression of CSC markers.

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.

Oral Cancer Stem Cells: Therapeutic Implications and Challenges

Head and neck squamous cell carcinoma (HNSCC) is currently one of the 10 most common malignancies worldwide, characterized by a biologically highly diverse group of tumors with non-specific biomarkers and poor prognosis. The incidence rate of HNSCC varies widely throughout the world, with an evident prevalence in developing countries such as those in Southeast Asia and Southern Africa. Tumor relapse and metastasis following traditional treatment remain major clinical problems in oral cancer management. Current evidence suggests that therapeutic resistance and metastasis of cancer are mainly driven by a unique subpopulation of tumor cells, termed cancer stem cells (CSCs), or cancer-initiating cells (CICs), which are characterized by their capacity for self-renewal, maintenance of stemness and increased tumorigenicity. Thus, more understanding of the molecular mechanisms of CSCs and their behavior may help in developing effective therapeutic interventions that inhibit tumor growth and progression. This review provides an overview of the main signaling cascades in CSCs that drive tumor repropagation and metastasis in oral cancer, with a focus on squamous cell carcinoma. Other oral non-SCC tumors, including melanoma and malignant salivary gland tumors, will also be considered. In addition, this review discusses some of the CSC-targeted therapeutic strategies that have been employed to combat disease progression, and the challenges of targeting CSCs, with the aim of improving the clinical outcomes for patients with oral malignancies. Targeting of CSCs in head and neck cancer (HNC) represents a promising approach to improve disease outcome. Some CSC-targeted therapies have already been proven to be successful in pre-clinical studies and they are now being tested in clinical trials, mainly in combination with conventional treatment regimens. However, some studies revealed that CSCs may not be the only players that control disease relapse and progression of HNC. Further, clinical research studying a combination of therapies targeted against head and neck CSCs may provide significant advances.

Targeting Cancer Stem Cell Markers or Pathways: A Potential Therapeutic Strategy for Oral Cancer Treatment

Cancer stem cells (CSCs) are a small subset of cancer cells with stem cell-like properties, self-renewal potential, and differentiation capacity into multiple cell types. Critical genetic alterations or aberrantly activated signaling pathways associated with drug resistance and recurrence have been observed in multiple types of CSCs. In this context, CSCs are considered to be responsible for tumor initiation, growth, progression, therapeutic resistance, and metastasis. Therefore, to effectively eradicate CSCs, tremendous efforts have been devoted to identify specific target molecules that play a critical role in regulating their distinct functions and to develop novel therapeutics, such as proteins, monoclonal antibodies, selective small molecule inhibitors, and small antisense RNA (asRNA) drugs. Similar to other CSC types, oral CSCs can be characterized by certain pluripotency-associated markers, and oral CSCs can also survive and form 3D tumor spheres in suspension culture conditions. These oral CSC-targeting therapeutics selectively suppress specific surface markers or key signaling components and subsequently inhibit the stem-like properties of oral CSCs. A large number of new therapeutic candidates have been tested, and some products are currently in the pre-clinical or clinical development phase. In the present study, we review new oral CSC-targeted therapeutic strategies and discuss the various specific CSC surface markers and key signaling components involved in the stem-like properties, growth, drug resistance, and tumorigenicity of oral CSCs.

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.

Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma-Treatment Modalities

Head and neck squamous cell carcinoma (HNSCC) belongs to the most frequent cancer subtypes in the world. Mutations due to genetic and chromosomal instability, syndromes such as Fanconi anemia and the Bloom syndrome, environmental risk factors such as tobacco smoking, alcohol and human papillomavirus infection (HPV) subtypes 16,18,31,33,35,52,58 are implicated in its pathogenesis. The HNSCC belongs to the solid tumors of epithelial origin and consists of stromal, inflammatory, cancer cells and most importantly a fraction of them, the cancer stem cells (CSCs). The identification of the CSCs through their biomarkers such as CD44, CD10, CD166, CD133, CD271, ALDH, Oct4, Nanog, Sox2 and Bmi1, the maintenance of their subpopulation through epithelial to mesenchymal transition, the role of HPV infection regarding their prognosis and of their microenvironment regarding their resistance to therapy, all constitute key elements that must be taken thoroughly into consideration in order to develop an effective targeted therapy. There are already therapies in place targeting specific related biomarkers, important biochemical pathways and growth factors. The aim of this literature review is to illustrate the treatment modalities available against the cancer stem cells of head and neck squamous cell carcinoma.

Prognostic Implications of ALDH1 and Notch1 in Different Subtypes of Oral Cancer

Background

The present study aimed to investigate the clinical significance and prognostic value of the immunoexpression of cancer stem cell markers, ALDH1 and Notch1, in subtypes of oral squamous cell carcinoma.

Materials and Methods

The expression of ALDH1 and Notch1 in 63 patients with well and poorly differentiated oral squamous cell carcinomas and their subtypes, verrucous carcinoma and basaloid squamous cell carcinoma, was evaluated by immunohistochemistry. The semi-quantitative analysis of the ALDH1 and Notch immunoexpression levels, based on the capture of 10 microscopic fields, at 400X magnification, at the invasive tumor front was performed and associated with clinicopathological variables using the chi-square test or Fisher's exact test. The overall and disease-free survival rates were estimated according to the Kaplan-Meier method and the curves were compared using the log-rank test. The independent effects of variables were calculated using Cox's proportional hazards regression model.

Results

Strong ALDH1 and Notch1 expression was observed in 16 (25.4%) and 27 (42.9%) oral squamous cell carcinomas including their subtypes, respectively. Most tumors with strong immunoexpression of ALDH1 were basaloid squamous cell carcinoma (56.3%). Statistically significant associations were observed between the strong immunoexpression of Notch1 in poorly differentiated oral squamous cell carcinoma with perineural infiltration (p = 0.011) and lymph node involvement (pN+) (p = 0.034). The strong immunoexpression of ALDH1 was a prognostic factor associated with worse overall survival (p = 0.040) for patients with oral cancer.

Conclusion

The strong immunoexpression of Notch1 can contribute to identification of patients with poorly differentiated oral squamous cell carcinoma, who have perineural infiltration or lymph node metastasis. In addition, the strong immunoexpression of ALDH1 may help to identify a worse prognosis in patients with oral squamous cell carcinoma and their subtypes.

HPV+ve/-ve oral-tongue cancer stem cells: A potential target for relapse-free therapy

The tongue squamous cell carcinoma (TSCC) is a highly prevalent head and neck cancer often associated with tobacco and/or alcohol abuse or high-risk human papillomavirus (HR-HPV) infection. HPV positive TSCCs present a unique mechanism of tumorigenesis as compared to tobacco and alcohol-induced TSCCs and show a better prognosis when treated. The poor prognosis and/or recurrence of TSCC is due to presence of a small subpopulation of tumor-initiating tongue cancer stem cells (TCSCs) that are intrinsically resistant to conventional chemoradio-therapies enabling cancer to relapse. Therefore, targeting TCSCs may provide efficient therapeutic strategy for relapse-free survival of TSCC patients. Indeed, the development of new TCSC targeting therapeutic approaches for the successful elimination of HPV+ve/-ve TCSCs could be achieved either by targeting the self-renewal pathways, epithelial mesenchymal transition, vascular niche, nanoparticles-based therapy, induction of differentiation, chemoradio-sensitization of TCSCs or TCSC-derived exosome-based drug delivery and inhibition of HPV oncogenes or by regulating epigenetic pathways. In this review, we have discussed all these potential approaches and highlighted several important signaling pathways/networks involved in the formation and maintenance of TCSCs, which are targetable as novel therapeutic targets to sensitize/eliminate TCSCs and to improve survival of TSCC patients.

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.

Expression and Role of E-Cadherin, β-Catenin, and Vimentin in Human Papillomavirus-Positive and Human Papillomavirus-Negative Oropharyngeal Squamous Cell Carcinoma

Oropharyngeal squamous cell carcinoma (OPSCC) is subclassified by the World Health Organization into two different entities: human papillomavirus (HPV)-positive and HPV-negative tumors. HPV infection promotes the epithelial-to-mesenchymal transition (EMT) and transformation of keratinocyte stem cells into cancer stem cells. EMT is a crucial process in the carcinogenesis of epithelial-derived malignancies, and we aimed to study the role of its markers in OPSCC. This study consists of 202 consecutive OPSCC patients diagnosed and treated with curative intent. We examined E-cadherin, β-catenin, and vimentin expression using immunohistochemistry and compared these with tumor and patient characteristics and treatment outcome. We found that the cell-membranous expression of β-catenin was stronger in HPV-positive than in HPV-negative tumors, and it was stronger in the presence of regional metastasis. The stromal vimentin expression was stronger among HPV-positive tumors. A high E-cadherin expression was associated with tumor grade. No relationship between these markers and survival emerged. In conclusion, β-catenin and vimentin seem to play different roles in OPSCC: the former in the tumor tissue itself, and the latter in the tumor stroma. HPV infection may exploit the β-catenin and vimentin pathways in carcinogenic process. More, β-catenin may serve as a marker for the occurrence of regional metastasis:

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.

Oral cancer stem cells drive tumourigenesis through activation of stromal fibroblasts

BACKGROUND

Cancer stem cells are responsible for tumour progression and chemoresistance. Fibroblasts surrounding a tumour also promote progression and fibroblast "activation" is an independent prognostic marker in oral cancer. Cancer stem cells may therefore promote tumourigenesis through communication with stromal fibroblasts.

METHODS

Cancer stem cells were isolated from oral cancer cell lines by adherence to fibronectin or cisplatin resistance. Fibroblasts were exposed to conditioned medium from these cells, and the activation markers, alpha smooth muscle actin and interleukin-6, were assessed using qPCR and immunofluorescence. Stem cell markers and smooth muscle actin were examined in oral cancer tissue using immunohistochemistry.

RESULTS

Adherent and chemoresistant cells expressed increased levels of stem cell markers CD24, CD44 and CD29 compared with unsorted cells. Adherent cells exhibited lower growth rate, higher colony forming efficiency and increased cisplatin resistance than unsorted cells. Smooth muscle actin and Interleukin-6 expression were increased in fibroblasts exposed to conditioned medium. In oral cancer tissue, there was a positive correlation between expression of αSMA and stem cell markers.

CONCLUSIONS

Adherence to fibronectin and chemoresistance isolates stem-like cells that can activate fibroblasts, which together with a correlation between markers of both in vivo, provides a mechanism by which such cells drive tumourigenesis.

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.

Targeting cancer stem cells in squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a highly aggressive tumor and the sixth most common cancer worldwide. Current treatment strategies for HNSCC are surgery, radiotherapy, chemotherapy, immunotherapy or combinatorial therapies. However, the overall 5-year survival rate of HNSCC patients remains at about 50%. Cancer stem cells (CSCs), a small population among tumor cells, are able to self-renew and differentiate into different tumor cell types in a hierarchical manner, similar to normal tissue. In HNSCC, CSCs are proposed to be responsible for tumor initiation, progression, metastasis, drug resistance, and recurrence. In this review, we discuss the molecular and cellular characteristics of CSCs in HNSCC. We summarize current approaches used in the literature for identification of HNSCC CSCs, and mechanisms required for CSC regulation. We also highlight the role of CSCs in treatment failure and therapeutic targeting options for eliminating CSCs in HNSCC.

The stem cell markers expression CD44v6 and podoplanin in lip cancer: clinical significance

This study aimed to analyze the immunoexpression of cancer stem cell markers, CD44v6, and podoplanin in 91 patients with lip squamous cell carcinomas (LSCC). The immunostaining of podoplanin and CD44v6 was evaluated in ten high-power fields (× 400 magnification) at the invasive front of LSCC, using a semi-quantitative score method. Chi-square test or Fisher's exact test was used to verify the association of podoplanin and CD44v6 expressions with clinicopathologic variables. Spearman's correlation test was used to analyze the correlation between the two antibodies in lip cancer. Disease-free survival probabilities in 5 and 10 years were estimated according to the Kaplan-Meier method and compared using the log-rank test. The independent effects of the significant variables were analyzed by Cox proportional hazards regression model. A strong podoplanin expression was observed in the membrane and cytoplasm of most lip tumor cells, and this was inversely associated with locoregional recurrence (p = 0.028) and with histopathological grade of malignancy (p = 0.026). Additionally, CD44v6 immunostaining was strongly expressed in the membrane of tumor cells in 95.4% of the LSCC. Patients with strong membranous (p = 0.016) or strong cytoplasmic (p = 0.030) podoplanin-positive tumors resulted in significantly better disease-free survival than those who had podoplanin weak/negative tumors, confirming podoplanin expression as a favorable independent prognostic factor. Podoplanin and CD44v6 were strongly expressed by tumor cells and podoplanin immunoexpression can help to determine lip cancer patients with lower risk for disease recurrence.

Cancer stem cells and fibroblast niche cross talk in an in-vitro oral dysplasia model

Understanding the cellular interactions during oral carcinogenesis has the potential to identify novel prognostic and therapeutic targets. This study aimed at investigating the cancer stem cell (CSC)-fibroblast niche interactions using in-vitro dysplastic cell line models developed from different stages of 4NQO-induced oral carcinogenic mice model. The spontaneously transformed epithelial cells (DysMSCTR6, 14 and 16) were developed from three time points (mild/moderate/severe), while two fibroblast cell lines (FibroMSCTR12, 16) were developed from moderate and severe dysplastic tissue. The epithelial (Epcam+/Ck+) and the fibroblast cell lines (Vimentin+/α-SMA+/Ck-) were authenticated and assessment of cells representing progressive grades of dysplastic severity indicated a significant increase in dysplastic marker profile (P < 0.05). Evaluation of the CSC characteristics showed that an increase in expression of Cd133, Cd44, Aldh1a1, Notch1, and Sox2 was accompanied by an increase in migratory (P > 0.05) and colony formation capacity (P > 0.005). Targeting Notch1 (GSI inhibitor PZ0187; 30 μM), showed a significant reduction in cell proliferation capacity (P < 0.05) and in the dysplastic marker profile. Further, Notch1 inhibition resulted in down regulation of Cd133 and Aldh1a 1 (P < 0.05) and a complete abrogation of colony formation ability (P < 0.0001). The effect of niche interactions evaluated using FibroMSCTR12-conditioned media studies, revealed an enrichment of ALDH1A1+ cells (P < 0.05), induction of spheroid formation ability (P < 0.0001) and increased proliferation capacity (3.7 fold; P < 0.005). Although PZ0187 reduced cell viability by ∼40%, was unable to abrogate the conditioned-media induced increase in proliferation capacity completely. This study reports a Notch-1 dependent enrichment of CSC properties during dysplastic progression and a Notch-1 independent dysplastic cell-fibroblast interaction during oral carcinogenesis.

Decreased expression of cell adhesion genes in cancer stem-like cells isolated from primary oral squamous cell carcinomas

The goal of this study was to isolate cancer stem-like cells marked by high expression of CD44, a putative cancer stem cell marker, from primary oral squamous cell carcinomas and identify distinctive gene expression patterns in these cells. From 1 October 2013 to 4 September 2015, 76 stage III-IV primary oral squamous cell carcinoma of the gingivobuccal sulcus were resected. In all, 13 tumours were analysed by immunohistochemistry to visualise CD44-expressing cells. Expression of CD44 within The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma RNA-sequencing data was also assessed. Seventy resected tumours were dissociated into single cells and stained with antibodies to CD44 as well as CD45 and CD31 (together referred as Lineage/Lin). From 45 of these, CD44+Lin- and CD44-Lin- subpopulations were successfully isolated using fluorescence-activated cell sorting, and good-quality RNA was obtained from 14 such sorted pairs. Libraries from five pairs were sequenced and the results analysed using bioinformatics tools. Reverse transcription quantitative polymerase chain reaction was performed to experimentally validate the differential expression of selected candidate genes identified from the transcriptome sequencing in the same 5 and an additional 9 tumours. CD44 was expressed on the surface of poorly differentiated tumour cells, and within the The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma samples, its messenger RNA levels were higher in tumours compared to normal. Transcriptomics revealed that 102 genes were upregulated and 85 genes were downregulated in CD44+Lin- compared to CD44-Lin- cells in at least 3 of the 5 tumours sequenced. The upregulated genes included those involved in immune regulation, while the downregulated genes were enriched for genes involved in cell adhesion. Decreased expression of PCDH18, MGP, SPARCL1 and KRTDAP was confirmed by reverse transcription quantitative polymerase chain reaction. Lower expression of the cell-cell adhesion molecule PCDH18 correlated with poorer overall survival in the The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma data highlighting it as a potential negative prognostic factor in this cancer.

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.

RGD-Binding Integrins in Head and Neck Cancers

Alterations in integrin expression and function promote tumour growth, invasion, metastasis and neoangiogenesis. Head and neck cancers are highly vascular tumours with a tendency to metastasise. They express a wide range of integrin receptors. Expression of the αv and β1 subunits has been explored relatively extensively and linked to tumour progression and metastasis. Individual receptors αvβ3 and αvβ5 have proved popular targets for diagnostic and therapeutic agents but lesser studied receptors, such as αvβ6, αvβ8, and β1 subfamily members, also show promise. This review presents the current knowledge of integrin expression and function in squamous cell carcinoma of the head and neck (HNSCC), with a particular focus on the arginine-glycine-aspartate (RGD)-binding integrins, in order to highlight the potential of integrins as targets for personalised tumour-specific identification and therapy.