CD44v3+/CD24- cells possess cancer stem cell-like properties in human oral squamous cell carcinoma

Meta-Analysis of Prognostic Significance of Cancer Stem Cell Markers in Oral Squamous Cell Carcinoma

OBJECTIVE

Researchers have shown significant interest in cancer stem cells in recent years. CD44, CD24, CD133, and ALDH serve as indicators of cancer stem cell-like cells in Oral Squamous Cell Carcinoma. However, the prognostic significance of these Cancer Stem Cell markers in Squamous Cell Carcinoma is still debated. This study employed meta-analysis to evaluate the prognostic significance of cancer stem cells about Oral Squamous Cell Carcinoma.

METHODS

CD44, CD133, CD24, and ALDH markers were analyzed in 19 retrospective studies to determine their relationship with prognosis and clinicopathological parameters. Risk ratios (RRs) and odds ratios (ORs) were calculated for 3-years survival rates and clinicopathological parameters, respectively, using a fixed-effects model.

RESULT

The finding of our study based on extracted survival rates showed that cancer stem cell markers, CD133 expression was related with the poor prognosis (RR= 1.62 ,95% CI = 1.08-2.44, P= 0.02). ALDH expression significantly correlated with lymph node metastasis (OR= 4.13, 95% Cl= 1.88-9.10, P<0.001) and clinical staging (OR= 2.26, 95% CI= 1.05-4.88, P= 0.04).

CONCLUSION

The findings indicate that CSC markers could be used to predict oral cancer prognosis. Our study contributes to the literature on survival outcomes of Oral Squamous Cell Carcinoma. These findings offer a structure for the advancement of cancer treatments that specifically target cancer stem cells. Conducting additional studies with a broader group of patients will help confirm the role of cancer stem cells as dependable predictors of prognosis.

Generality Assessment of a Model Considering Heterogeneous Cancer Cells for Predicting Tumor Control Probability for Stereotactic Body Radiation Therapy Against Non-Small Cell Lung Cancer

The generality of a model for predicting tumor control probability from in vitro clonogenic survival considering of cancer stem-like cells, the so-called integrated microdosimetric-kinetic model, is presented by comparing the model to public data on stereotactic body radiation therapy for non-small cell lung cancer cells.

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.

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.

IFIT2 Depletion Promotes Cancer Stem Cell-like Phenotypes in Oral Cancer

(1) Background: Cancer stem cells (CSCs) are a small cell population associated with chemoresistance, metastasis and increased mortality rate in oral cancer. Interferon-induced proteins with tetratricopeptide repeats 2 (IFIT2) depletion results in epithelial to mesenchymal transition, invasion, metastasis, and chemoresistance in oral cancer. To date, no study has demonstrated the effect of IFIT2 depletion on the CSC-like phenotype in oral cancer cells. (2) Methods: Q-PCR, sphere formation, Hoechst 33,342 dye exclusion, immunofluorescence staining, and flow cytometry assays were performed to evaluate the expression of the CSC markers in IFIT2-depleted cells. A tumorigenicity assay was adopted to assess the tumor formation ability. Immunohistochemical staining was used to examine the protein levels of IFIT2 and CD24 in oral cancer patients. (3) Results: The cultured IFIT2 knockdown cells exhibited an overexpression of ABCG2 and CD44 and a downregulation of CD24 and gave rise to CSC-like phenotypes. Clinically, there was a positive correlation between IFIT2 and CD24 in the patients. IFIT2high/CD24high/CD44low expression profiles predicted a better prognosis in HNC, including oral cancer. The TNF-α blockade abolished the IFIT2 depletion-induced sphere formation, indicating that TNF-α may be involved in the CSC-like phenotypes in oral cancer. (4) Conclusions: The present study demonstrates that IFIT2 depletion promotes CSC-like phenotypes in oral cancer.

CD44v3 is a marker of invasive cancer stem cells driving metastasis in gastric carcinoma

BACKGROUND

Cancer stem cells (CSCs) are at the origin of tumour initiation and progression in gastric adenocarcinoma (GC). However, markers of metastasis-initiating cells remain unidentified in GC. In this study, we characterized CD44 variants expressed in GC and evaluated the tumorigenic and metastatic properties of CD44v3+ cells and their clinical significance in GC patients.

METHODS

Using GC cell lines and patient-derived xenografts, we evaluated CD44+ and CD44v3+ GC cells molecular signature and their tumorigenic, chemoresistance, invasive and metastatic properties, and expression in patients-derived tissues.

RESULTS

CD44v3+ cells, which represented a subpopulation of CD44+ cells, were detected in advanced preneoplastic lesions and presented CSCs chemoresistance and tumorigenic properties in vitro and in vivo. Molecular and functional analyses revealed two subpopulations of gastric CSCs: CD44v3+ CSCs with an epithelial-mesenchymal transition (EMT)-like signature, and CD44+/v3- CSCs with an epithelial-like signature; both were tumorigenic but CD44v3+ cells showed higher invasive and metastatic properties in vivo. CD44v3+ cells detected in the primary tumours of GC patients were associated with a worse prognosis.

CONCLUSION

CD44v3 is a marker of a subpopulation of CSCs with metastatic properties in GC. The identification of metastasis-initiating cells in GC represents a major advance for further development of anti-metastatic therapeutic strategies.

1,2,3,4,6-Penta-O-galloyl-β-D-glucose Inhibits CD44v3, a cancer stem cell marker, by regulating its transcription factor, in human pancreatic cancer cell line

Inhibition of cluster of differentiation 44 (CD44), a pancreatic cancer stem cell (CSC) marker, is a potential treatment for pancreatic ductal adenocarcinoma (PDAC). In this study, we evaluated the effect of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG), a gallotannin contained in various medicinal plants, on CD44 standard (CD44s) and CD44 variant 3 (CD44v3) in Mia-PaCa-2, human pancreatic cancer cells and explored the underlying mechanisms. PGG showed cytotoxic effects and inhibited the proliferation of Mia-PaCa-2 cells. It also inhibited clonogenic activity, adhesion to fibronectin, and cell migration, which are characteristics of CSCs. PGG inhibited the expression of CD44s and CD44v3 by inducing the phosphorylation of p53 and suppressing NF-κB and Foxo3. Inhibition of Foxo3 induces CD44v3 ubiquitination. Indeed, PGG increased proteasome activity and promoted CD44v3 ubiquitination. PGG downregulated the CSC regulatory factors Nanog, Oct-4, and Sox-2, which act downstream of CD44v3 signaling. These data indicate that PGG may have therapeutic effects in pancreatic cancer mediated by inhibition of CSC markers.

4-Methylumebelliferone Enhances Radiosensitizing Effects of Radioresistant Oral Squamous Cell Carcinoma Cells via Hyaluronan Synthase 3 Suppression

Radioresistant (RR) cells are poor prognostic factors for tumor recurrence and metastasis after radiotherapy. The hyaluronan (HA) synthesis inhibitor, 4-methylumbelliferone (4-MU), shows anti-tumor and anti-metastatic effects through suppressing HA synthase (HAS) expression in various cancer cells. We previously reported that the administration of 4-MU with X-ray irradiation enhanced radiosensitization. However, an effective sensitizer for radioresistant (RR) cells is yet to be established, and it is unknown whether 4-MU exerts radiosensitizing effects on RR cells. We investigated the radiosensitizing effects of 4-MU in RR cell models. This study revealed that 4-MU enhanced intracellular oxidative stress and suppressed the expression of cluster-of-differentiation (CD)-44 and cancer stem cell (CSC)-like phenotypes. Interestingly, eliminating extracellular HA using HA-degrading enzymes did not cause radiosensitization, whereas HAS3 knockdown using siRNA showed similar effects as 4-MU treatment. These results suggest that 4-MU treatment enhances radiosensitization of RR cells through enhancing oxidative stress and suppressing the CSC-like phenotype. Furthermore, the radiosensitizing mechanisms of 4-MU may involve HAS3 or intracellular HA synthesized by HAS3.

miR-146a participates in the regulation of cancer stemness of oral carcinoma cells

Background/purpose

Increasing evidence regarded the existence of cancer stem cells (CSCs) as a leading cause of therapy failure and tumor relapse due to their self-renewal and differentiation abilities. Although ectopic overexpression of micro-RNAs (miRNAs) can modulate the cancer stemness and tumor development in oral cancer, their molecular mechanism is still unclear. Therefore, in the present study, we attempt to uncover the role of miR-146a in the maintenance of oral CSCs.

Materials and methods

The expression of miR-146a was determined using qRT-PCR analysis. Aldehyde dehydrogenase (ALDH) enzymic activity and sphere formation assays were used to evaluate the cancer stemness and self-renewal, respectively. Functional assays, including migration/invasion Transwell and colony formation assay, were used to evaluate the aggressive abilities. Luciferase reporter assay was performed to validate the relationship between miR-146a and Numb.

Results

In the present study, we reported an increased expression of miR-146a in the oral squamous cell carcinoma (OSCC) specimen, primary OSCC cells sphere, and high ALDH1 activity population within OSCC cells. Inhibition of miR-146a significantly suppressed the ALDH1 activity, self-renewal capacity, and aggressive abilities, including migration, invasion, and colony formation. Moreover, we demonstrated that Numb is a functional target of miR-146a in OSCC-CSCs. Notably, silencing of Numb could retrieve the self-renewal and migration impaired by knockdown of miR-146a.

Conclusion

Our results indicate that miR-146a can regulate the cancer stemness in OSCC by modulating Numb, and hence miR-146a/Numb axis can serve as a potential target for oral cancer therapy.

Prognostic utility of SOX2, STAT3, and CD44high/CD24low expression in penile cancer

PURPOSE

Penile cancer has a high incidence in developing countries. The standard treatment is removal of the primary tumor and, when necessary, inguinal lymphadenectomy. Currently, the most important prognostic factor is lymph node disease, however, the available staging methods are inaccurate, and the high morbidity rate of lymphadenectomy has stimulated the study of predictive biomarkers of lymph node metastasis for selecting the patients who need lymphadenectomy. SOX2, STAT3 and CD44^high/CD24^low were chosen because they have provided good predictive results in other squamous cell carcinoma (SCC), although there are no studies for penile cancer. Thus, the expression of SOX2, STAT3, CD24+, and CD44+ in the penile cancer tumor microenvironment was investigated for correlation with tumor behavior in SCC.

METHODS

This observational, prospective, translational study included 34 men and investigated the expression of SOX2, STAT3, CD24+, and CD44+ in tumor tissue by flow cytometry.

RESULTS

The median age of the 38 evaluated patients with penile cancer was 61 (37-80) years. Most patients presented a tumor located on the glans penis (82.3%), with the usual histological type (79.4%) and 61.7% of patients presented stage pT2. No metastasis was found in 85.3% of patients. The expression of SOX2, STAT3 and CD44^high/CD24^low in the microenvironment of penile SCC treated with lymphadenectomy was significantly associated with aggressive tumor behavior (p < 0.05). STAT3 expression shows discrepant points when evaluated in context of angiolymphatic vascular invasion.

CONCLUSION

SOX2, STAT3 and CD44^high/CD24^low in penile SCC can be indicators of prognosis, allowing for selection of more aggressive treatment when necessary.

Cargo and Functional Profile of Saliva-Derived Exosomes Reveal Biomarkers Specific for Head and Neck Cancer

Background

Exosomes contribute to immunosuppression in head and neck squamous cell carcinoma (HNSCC), a tumor entity which lacks specific tumor biomarkers. Plasma-derived exosomes from HNSCC patients correlate with clinical parameters and have potential as liquid biopsy. Here, we investigate the cargo and functional profile of saliva-derived exosomes from HNSCC patients and their potential as non-invasive biomarkers for disease detection and immunomodulation.

Methods

Exosomes were isolated from saliva of HNSCC patients (n = 21) and healthy donors (HD, n = 12) by differential ultracentrifugation. Surface values of immune checkpoints and tumor associated antigens on saliva-derived exosomes were analyzed by bead-based flow cytometry using CD63 capture. Upon co-incubation with saliva-derived exosomes, activity and proliferation of T cells were assessed by flow cytometry (CD69 expression, CFSE assay). Adenosine levels were measured by mass spectrometry after incubation of saliva-derived exosomes with exogenous ATP. miRNA profiling of saliva-derived exosomes was performed using the nCounter^® SPRINT system.

Results

Saliva-derived, CD63-captured exosomes from HNSCC patients carried high amounts of CD44v3, PDL1 and CD39. Compared to plasma, saliva was rich in tumor-derived, CD44v3⁺ exosomes and poor in hematopoietic cell-derived, CD45⁺ exosomes. CD8⁺ T cell activity was attenuated by saliva-derived exosomes from HNSCC patients, while proliferation of CD4⁺ T cells was not affected. Further, saliva-derived exosomes produced high levels of immunosuppressive adenosine. 62 HD- and 31 HNSCC-exclusive miRNAs were identified. Samples were grouped in "Healthy" and "Cancer" based on their saliva-derived exosomal miRNA profile, which was further found to be involved in RAS/MAPK, NF-κB complex, Smad2/3, and IFN-α signaling.

Conclusions

Saliva-derived exosomes from HNSCC patients were enriched in tumor-derived exosomes whose cargo and functional profile reflected an immunosuppressive TME. Surface values of CD44v3, PDL1 and CD39 on CD63-captured exosomes, adenosine production and the miRNA cargo of saliva-derived exosomes emerged as discriminators of disease and emphasized their potential as liquid biomarkers specific for HNSCC.

Eliminating Cancer Stem-Like Cells in Oral Cancer by Targeting Elementary Signaling Pathways

Oral cancer is a heterogeneous, aggressive, and complex entity. Current major treatment options for the disease are surgery, chemo, and/or radiotherapy either alone or in combination with each other. Each treatment method has its own limitations such as a significant journey with deformities and a protracted rehabilitation process leading to loss of self-esteem, loss of tolerance, and therapeutic side effects. Conventional therapies are frequently experienced with regimen resistance and recurrence attributed to the cancer stem cells (CSCs). Given that CSCs exert their tumorigenesis by affecting several cellular and molecular targets and pathways an improved understanding of CSCs' actions is required. Hence, more research is recommended to fully understand the fundamental mechanisms driving CSC-mediated treatment resistance. Despite the difficulties and disagreements surrounding the removal of CSCs from solid tumors, a great amount of knowledge has been derived from the characterization of CSCs. Various efforts have been made to identify the CSCs using several cell surface markers. In the current review, we will discuss numerous cell surface markers such as CD44, ALDH1, EPCAM, CD24, CD133, CD271, CD90, and Cripto-1 for identifying and isolating CSCs from primary oral squamous cell carcinoma (OSCC). Further, a spectrum of embryonic signaling pathways has been thought to be the main culprit of CSCs' active state in cancers, resulting in conventional therapeutic resistance. Hence, we discuss the functional and molecular bases of several signaling pathways such as the Wnt/beta;-catenin, Notch, Hedgehog, and Hippo pathways and their associations with disease aggressiveness. Moreover, numerous inhibitors targeting the above mentioned signaling pathways have already been identified and some of them are already undergoing clinical trials. Hence, the present review encapsulates the characterization and effectiveness of the prospective potential targeted therapies for eradicating CSCs in oral cancers.

Literature review of cancer stem cells in oral lichen planus: a premalignant lesion

OBJECTIVE

As there is no review study about cancer stem cells (CSCs) involved in the pathogenesis of oral lichen planus (OLP), for the first time we review the role of these cells in OLP and this hypothesis may be a clue for the evaluation of the premalignancy of OLP.

BACKGROUND

Cellular mediated immune responses are the main etiopathogenesis in OLP and it is a potentially premalignant lesion. One of the factors proposed in the pathogenesis of OLP and the comparable trend of this autoimmune disease to squamous cell carcinoma (SCC) are CSCs. CSCs have been detected in several solid tumors including head and neck cancers, and have special characteristics including metastasis and resistance to chemotherapy.

METHODS

Related keywords were searched and risk of bias assessment was done for each study.

CONCLUSIONS

Among all of the studies reviewed in this article, all markers had increased expression in OLP compared to controls that are consistent with SCC. Only CD44 was in contradiction to other papers, in which different expression of CD44 strains was measured in different samples such as saliva and tissue. Based on the results of this review and more studies in the future by investigating the levels of these markers in OLP, it may be possible to determine the prognosis and course of the disease for each patient individually.

CD44: A Multifunctional Mediator of Cancer Progression

CD44, a non-kinase cell surface transmembrane glycoprotein, has been widely implicated as a cancer stem cell (CSC) marker in several cancers. Cells overexpressing CD44 possess several CSC traits, such as self-renewal and epithelial-mesenchymal transition (EMT) capability, as well as a resistance to chemo- and radiotherapy. The CD44 gene regularly undergoes alternative splicing, resulting in the standard (CD44s) and variant (CD44v) isoforms. The interaction of such isoforms with ligands, particularly hyaluronic acid (HA), osteopontin (OPN) and matrix metalloproteinases (MMPs), drive numerous cancer-associated signalling. However, there are contradictory results regarding whether high or low CD44 expression is associated with worsening clinicopathological features, such as a higher tumour histological grade, advanced tumour stage and poorer survival rates. Nonetheless, high CD44 expression significantly contributes to enhanced tumourigenic mechanisms, such as cell proliferation, metastasis, invasion, migration and stemness; hence, CD44 is an important clinical target. This review summarises current research regarding the different CD44 isoform structures and their roles and functions in supporting tumourigenesis and discusses CD44 expression regulation, CD44-signalling pathways and interactions involved in cancer development. The clinical significance and prognostic value of CD44 and the potential of CD44 as a therapeutic target in cancer are also addressed.

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.

CD44 Sorted Cells Have an Augmented Potential for Proliferation, Epithelial-Mesenchymal Transition, Stemness, and a Predominantly Inflammatory Cytokine and Angiogenic Secretome

Cancer stem cells (CSCs) have garnered attention with their potential for early diagnosis and prognosis of oral squamous cell carcinoma (OSCC). It is still indistinct whether CSCs are recognized with a specific set of characteristics. The present study aimed to assess the association of CD44 with stemness-related, Epithelial Mesenchymal Transition EMT-related genes and the secretome of the CSCs. The single-cell suspension from primary OSCC tumors was prepared by enzymatic digestion and the cells were cultured in-vitro. The cancer stem cells were isolated by CD44+ selection using magnetic cell-sorting. The expression of CD44, proliferation rate, gene expression of EMT-related transcription factors, stemness markers, cytokine levels and angiogenic factors in both cell population was assessed. The sorted CD44+ cells showed significantly higher proliferation rate than heterogenous population. The CD44 expression was >90% in the sorted cells which was higher than the heterogenous cells. The CD44+ CSCs cells demonstrated significant increased levels of EMT-related genes TWIST1 and CDH2 (N-cadherin), CSC-related genes CD44 and CD133 (PROM1), stemness-related genes OCT4, SOX2, inflammatory cytokines IL-1ß, IL-12, IL-18 and TNF-α and angiogenic factors Angiopoietin-1, Angiopoietin-2, bFGF and VEGF while levels of epithelial gene CDH1 (E-cadherin) decreased in comparison to mixed cell population. The genetic and secretome profiling of the CD44+ CSCs could serve as diagnostic and prognostic tools in the treatment of oral cancers.

Extracellular Vesicles in Head and Neck Cancer: A Potential New Trend in Diagnosis, Prognosis, and Treatment

Head and neck cancer (HNC) is a fatal and debilitating disease that is characterized by steady, poor survival rates despite advances in treatment. There is an urgent and unmet need to improve our understanding of what drives this insidious cancer and causes poor outcomes. Extracellular vesicles (EVs) are small vesicles that originate from tumor cells, immune cells, and other cell types and are secreted into plasma, saliva, and other bio-fluids. EVs represent dynamic, real-time changes of cells and offer an exciting opportunity to improve our understanding of HNC biology that may translate to improved clinical practice. Considering the amplified interest in EVs, we have sought to provide a contemporary review of the most recent and salient literature that is shaping the field. Herein, we discuss the functionality of EVs in HNCs and their clinical potential with regards to biomarker and therapeutic capabilities.

Interplay between Podoplanin, CD44s and CD44v in Squamous Carcinoma Cells

Podoplanin and CD44 are transmembrane glycoproteins involved in inflammation and cancer. In this paper, we report that podoplanin is coordinately expressed with the CD44 standard (CD44s) and variant (CD44v) isoforms in vivo—in hyperplastic skin after a pro-inflammatory stimulus with 12-O-tetradecanoylphorbol-13-acetate (TPA)—and in vitro—in cell lines representative of different stages of mouse-skin chemical carcinogenesis, as well as in human squamous carcinoma cell (SCC) lines. Moreover, we identify CD44v10 in the mouse-skin carcinogenesis model as the only CD44 variant isoform expressed in highly aggressive spindle carcinoma cell lines together with CD44s and podoplanin. We also characterized CD44v3-10, CD44v6-10 and CD44v8-10 as the major variant isoforms co-expressed with CD44s and podoplanin in human SCC cell lines. Immunofluorescence confocal microscopy experiments show that these CD44v isoforms colocalize with podoplanin at plasma membrane protrusions and cell–cell contacts of SCC cells, as previously reported for CD44s. Furthermore, CD44v isoforms colocalize with podoplanin in chemically induced mouse-skin SCCs in vivo. Co-immunoprecipitation experiments indicate that podoplanin physically binds to CD44v3-10, CD44v6-10 and CD44v8-10 isoforms, as well as to CD44s. Podoplanin–CD44 interaction is mediated by the transmembrane and cytosolic regions and is negatively modulated by glycosylation of the extracellular domain. These results point to a functional interplay of podoplanin with both CD44v and CD44s isoforms in SCCs and give insight into the regulation of the podoplanin–CD44 association.

Evaluation of CD24 and CD44 as cancer stem cell markers in squamous cell carcinoma and epithelial dysplasia of the oral cavity by q- RT-PCR

BACKGROUND

Squamous cell carcinoma (SCC) is the most common cancer of the oral cavity and may be preceded by dysplastic epithelial lesion. Oral SCC (OSCC) contains a rare subset of cancer cells with self-renewal ability, termed as cancer stem cells (CSCs). CD24 and CD44 as CSC markers are cell surface glycoproteins. These markers contribute to the onset, maintenance, and extension of tumor growth, as well as angiogenesis. In the present study, these two markers were simultaneously evaluated to provide a specific phenotype for carcinogenesis process in oral cavity.

MATERIALS AND METHODS

In this analytical-cross-sectional study, the expression of CD24 and CD44 genes was evaluated in 45 OSCCs (20 low-grade and 25 high-grade) and 15 oral epithelial dysplasia specimens by real-time quantitative reverse transcription polymerase chain reaction. Kruskal-Wallis and Mann-Whitney U-test, Kendall, and Spearman tests were used for statistical analysis. The significance level was considered <0.05.

RESULTS

High expression of both markers genes was reported in two-thirds of samples. There was no significant difference between studied groups in gene expression of CD24 and CD44 whereas statistically significant association between CD24 and CD44 was observed in all three groups. This correlation was more significant in OSCC groups (P < 0.001).

CONCLUSION

High expression of CSC markers in OSCC and oral epithelial dysplasia revealed the importance of accurate examination of dysplastic lesions with high expression of these markers and the possibility of malignant transformation. Regarding a significant association of two markers, further studies are necessary to provide a specific phenotype (CD44 high CD24 high) for these lesions.

Mitochondrial DNA alterations may influence the cisplatin responsiveness of oral squamous cell carcinoma

Cisplatin is the first-line chemotherapeutic agent for the treatment of oral squamous cell carcinoma (OSCC). However, the intrinsic or acquired resistance against cisplatin remains a major obstacle to treatment efficacy in OSCC. Recently, mitochondrial DNA (mtDNA) alterations have been reported in a variety of cancers. However, the role of mtDNA alterations in OSCC has not been comprehensively studied. In this study, we evaluated the correlation between mtDNA alterations (mtDNA content, point mutations, large-scale deletions, and methylation status) and cisplatin sensitivity using two OSCC cell lines, namely SAS and H103, and stem cell-like tumour spheres derived from SAS. By microarray analysis, we found that the tumour spheres profited from aberrant lipid and glucose metabolism and became resistant to cisplatin. By qPCR analysis, we found that the cells with less mtDNA were less responsive to cisplatin (H103 and the tumour spheres). Based on the findings, we theorised that the metabolic changes in the tumour spheres probably resulted in mtDNA depletion, as the cells suppressed mitochondrial respiration and switched to an alternative mode of energy production, i.e. glycolysis. Then, to ascertain the origin of the variation in mtDNA content, we used MinION, a nanopore sequencer, to sequence the mitochondrial genomes of H103, SAS, and the tumour spheres. We found that the lower cisplatin sensitivity of H103 could have been caused by a constellation of genetic and epigenetic changes in its mitochondrial genome. Future work may look into how changes in mtDNA translate into an impact on cell function and therefore cisplatin response.

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.

CD44v3 protein-carrying tumor-derived exosomes in HNSCC patients' plasma as potential noninvasive biomarkers of disease activity

The molecular cargo of tumor-cell-derived exosomes (TEX) mimics that of parental tumor cells. Thus, TEX could potentially serve as noninvasive biomarkers of cancer progression. However, separation of TEX from non-TEX in patients’ plasma requires tumor antigen-specific detection reagents. CD44v3 has been of interest as a potential biomarker of disease progression in HNSCC, because its overexpression in tumor cells associates with poor outcome. Here, CD44v3+ TEX immunocaptured from plasma of 44 HNSCC patients and 7 healthy donors (HDs) were evaluated as potential biomarkers of disease activity and stage. Exosomes were isolated from plasma of by size exclusion chromatography. Using anti-CD44v3 or anti-CD3 mAbs on beads, CD44v3+ TEX CD3(-)TEX-enriched exosomes were immunocaptured from supernatants of nonmalignant or HNSCC cell lines and from patients’ plasma. On-bead flow cytometry was used for the detection of FAS-L, PD-L1, TGFF-β. CSPG4 or EGFR on exosomes. The TEX expression profiles were correlated to clinicopathological parameters. Relative florescence intensity (RFI) values for CD44v3 were higher (p < .01) on TEX from HNSCC cell lines or on CD44v3+ CD3(-) plasma-derived exosomes. RFI values of CD44v3 on CD3(-) exosomes were higher (p < .005) in patients than in HDs and correlated (p < .05) with the UICC stage and lymph node metastasis. In HNSCC patients, CD44v3+ exosomes higher levels of immunosuppressive proteins compared to CD44v3(-) exosomes (p < .05-p < .005), and RFI values for these markers correlated with higher disease stages and lymph node metastasis. Isolation of CD44v3+ exosomes by immunocapture allowed for enrichment of TEX which are potentially promising liquid biomarkers of the tumor burden and disease stage in HNSCC.

Cancer stem cells and oral cancer: insights into molecular mechanisms and therapeutic approaches

Cancer stem cells (CSCs) have been identified as a little population of cancer cells, which have features as the same as the cells normal stem cells. There is enough knowledge of the CSCs responsibility for metastasis, medicine resistance, and cancer outbreak. Therefore, CSCs control possibly provides an efficient treatment intervention inhibiting tumor growth and invasion. In spite of the significance of targeting CSCs in treating cancer, few study comprehensively explored the nature of oral CSCs. It has been showed that oral CSCs are able to contribute to oral cancer progression though activation/inhibition a sequences of cellular and molecular pathways (microRNA network, histone modifications and calcium regulation). Hence, more understanding about the properties of oral cancers and their behaviors will help us to develop new therapeutic platforms. Head and neck CSCs remain a viable and intriguing option for targeted therapy. Multiple investigations suggested the major contribution of the CSCs to the metastasis, tumorigenesis, and resistance to the new therapeutic regimes. Therefore, experts in the field are examining the encouraging targeted therapeutic choices. In spite of the advancements, there are not enough information in this area and thus a magic bullet for targeting and eliminating the CSCs deviated us. Hence, additional investigations on the combined therapies against the head and neck CSCs could offer considerable achievements. The present research is a review of the recent information on oral CSCs, and focused on current advancements in new signaling pathways contributed to their stemness regulation. Moreover, we highlighted various therapeutic approaches against oral CSCs.

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.

Distinct roles of PIK3CA in the enrichment and maintenance of cancer stem cells in head and neck squamous cell carcinoma

Recurrence and metastasis are the major causes of mortality in head and neck squamous cell carcinoma (HNSCC). It is suggested that cancer stem cells (CSCs) play pivotal roles in recurrence and metastasis. Thus, a greater understanding of the mechanisms of CSC regulation may provide opportunities to develop novel therapies for improving survival by controlling recurrence or metastasis. Here, we report that overexpression of the gene encoding the catalytic subunit of PI3K (PIK3CA), the most frequently amplified oncogene in HNSCC, promotes epithelial‐to‐mesenchymal transition and enriches the CSC population. However, PIK3CA is not required to maintain these traits and inhibition of the phosphatidylinositol 3‐kinase (PI3K) signaling pathway paradoxically promotes CSC population. Molecular analysis revealed that overexpression of PIK3CA activates multiple receptor tyrosine kinases (RTKs), in which ephrin receptors (Ephs), tropomyosin receptor kinases (TRK) and mast/stem cell growth factor receptor (c‐Kit) contribute to maintain CSC population. Accordingly, simultaneous inhibition of these RTKs using a multi‐kinase inhibitor ponatinib has a superior effect at eliminating the CSC population and reduces metastasis of PIK3CA‐overexpressing HNSCC cells. Our result suggests that co‐targeting of Ephs, TRKs and the c‐Kit pathway may be effective at eliminating the PI3K‐independent CSC population, thereby providing potential targets for future development of a novel anti‐CSC therapeutic approach for HNSCC patients, particularly for patients with PIK3CA amplification.

TGFβ induces stemness through non-canonical AKT-FOXO3a axis in oral squamous cell carcinoma

Background

FOXO3a has been widely regarded as a tumor suppressor. It also plays a paradoxical role in regulating the cancer stem cells (CSCs), responsible for tumor-initiation, chemo-resistance, and recurrence in various solid tumors, including oral squamous cell carcinoma (OSCC). This study aims to uncover the role of FOXO3a and its importance for a non-canonical pathway of TGFβ in regulating the OSCC stemness.

Methods

We identified FOXO3a expression in OSCC tissues and cell lines using immunohistochemistry and western blot. The correlation between FOXO3a and stemness was evaluated. Stable cell lines with differential expression of FOXO3a were constructed using lentiviruses. The effects of FOXO3a on stem-cell like properties in OSCC was further evaluated in vitro and in vivo. We also explored the effect of TGFβ on FOXO3a with respect to its expression and function.

Findings

Our findings suggest that FOXO3a was widely expressed and negatively correlated with the stemness in OSCC. This regulation can be abolished by TGFβ through phosphorylation, nuclear exclusion, and degradation in the non-Smad pathway. We also observed that non-Smad AKT-FOXO3a axis is essential to regulate stemness of CSCs by TGFβ.

Interpretation

TGFβ induces stemness through non-canonical AKT-FOXO3a axis in OSCC. Our study provides a foundation to understand the mechanism of CSCs and a possible therapeutic target to eliminate CSCs.

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.

An Updated Review of Oral Cancer Stem Cells and Their Stemness Regulation

Cancer stem cells (CSCs; also known as tumor-initiating cells) are a small population of cancer cells that retain characteristics similar to those of normal stem cells. CSCs are known to be responsible for metastasis, drug resistance, and cancer recurrence. Thus, controlling CSCs may provide an effective therapeutic intervention that inhibits tumor growth and aggressiveness. Despite the importance of targeting CSCs in cancer therapy, the detailed nature of oral CSCs remains underexplored. This article reviews the current understanding of oral CSCs, with emphasis on recent advances in novel signaling pathways involved in their stemness regulation.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Isolation of cancer cells with augmented spheroid-forming capability using a novel tool equipped with removable filter

Three-dimensional (3D) cell culture systems have been used to obtain multicellular spheroidal cell aggregates, or spheroids, from cancer cells. However, it is difficult to efficiently prepare large tumor-derived spheroids from cancer cells. To circumvent this problem, we here used a tool equipped with removal membrane, called Spheroid Catch, for the selection and enrichment of large-sized and/or size-matched spheroids from human squamous cell carcinoma (SAS cells) without loss of recovery. After a five-round process of selection and enrichment, we successfully isolated a subpopulation of SAS cells with augmented spheroid-forming capability, named eSAS: the efficiency of spheroid formation is 28.5% (eSAS) vs 16.8% (parental SAS). Notably, we found that some of eSAS cells survived after exposure of high doses of cisplatin in 3D culture. Moreover, orthotopic implantation by injecting eSAS cells into the tongues of nude mice showed reduced survival rate and increased tumor growth compared with those of nude mice injected with SAS cells. These results suggest that spheroids exhibiting properties of higher spheroid forming capacity can be efficiently collected by using Spheroid Catch. Indeed, genome-wide cDNA microarray and western blot analyses demonstrated higher mRNA and protein levels of hedgehog acyltransferase (HHAT), which is associated with stem maintenance in cell carcinoma by catalysing the N-palmitoylation of Hedgehog proteins, in eSAS cells than in SAS cells. We propose that Spheroid Catch could be useful for the study of spheroids, and potentially organoids, in the basic and clinical sciences, as an alternative method to other type of cell strainers.

Nicotine inhibits CD24 expression in Lewis lung carcinoma cells by upregulation of RAS expression

Cluster of ddifferentiation 24 (CD24) is a widely used cancer stem cell (CSC) marker in numerous cancer types. However, a number of studies have shown that CD24 is a prognostic marker, but not a CSC marker for lung adenocarcinoma. In the present study, firstly, bioinformatic analyses were used to identify the CD24 mRNA levels in the subtypes of lung cancer. Secondly, CD24high and CD24low cells were isolated from the side population of Lewis lung carcinoma (LLC) cells using flow cytometry. Furthermore, the stemness of CD24high and CD24low cells were determined in vivo and in vitro. Lastly, the mechanism(s) of nicotine-inhibited CD24 expression in LLC cells were assessed. The main findings of this study are that: i) CD24 could be used as a prognostic marker for human lung adenocarcinoma; ii) the in vitro and in vivo experiments did not determine a significant influence of CD24 on the tumorgenicity of LLC cells; and iii) nicotine inhibited CD24 expression in LLC cells by upregulation of RAS. However, the detailed mechanism(s) of these results require further analysis.

Separation of plasma-derived exosomes into CD3(+) and CD3(-) fractions allows for association of immune cell and tumour cell markers with disease activity in HNSCC patients

Head and neck squamous cell carcinoma (HNSCC) is a highly immunosuppressive malignancy. Exosomes in HNSCC patients' plasma are enriched in inhibitory cargo and mediate immunosuppression. As these exosomes are products of various cells, the cellular origin of immunoregulatory proteins they carry is unknown. To test whether tumour- or T cell-derived exosomes in patients' plasma are immunosuppressive and impact upon disease activity, we separated CD3^(-) from CD3⁽⁺⁾ exosomes by immunocapture using anti-CD3 antibodies. The exosome protein cargo was evaluated for immunoregulatory proteins using on-bead flow cytometry. Tumour protein-enriched CD3^(-) exosomes were CD44v3⁽⁺⁾ . Surprisingly, mean levels of programmed death ligand 1 (PD-L1), cytotoxic T lymphocyte antigen 4 (CTLA-4) and cyclooxygenase-2 (COX-2) were similar in CD3⁽⁺⁾ and CD3^(-) exosomes, although the latter induced higher (P < 0·0025) ex-vivo apoptosis of CD8⁽⁺⁾ T cells and greater (P < 0·005) conversion of CD4⁺ T cells to CD4⁽⁺⁾ CD39⁽⁺⁾ regulatory T cells (T_reg ). CD3⁽⁺⁾ and CD3^(-) exosomes carrying high levels of immunosuppressive proteins were highly effective in mediating these functions. Exosomes of patients with Union for International Cancer Control (UICC) stages III/IV disease had higher levels of PD-L1 and COX-2 than stages I/II patients (P < 0·005). Patients with nodal involvement had exosomes with the higher inhibitory protein content than N0 patients (P < 0·03). CD3⁽⁺⁾ and CD3^(-) exosomes of HNSCC patients had higher PD-L1, COX-2 and CD15s levels than healthy donors' exosomes (P < 0·009), although levels of immunostimulatory OX40 or OX40L were not different. By isolating CD3^(-) /CD44v3-enriched and CD3⁽⁺⁾ exosomes from plasma, the cellular origins of immunoregulatory proteins they carry were identified. Association of exosome molecular profiles with disease progression supports the exosome potential as future cancer biomarkers.

SOX8 regulates cancer stem-like properties and cisplatin-induced EMT in tongue squamous cell carcinoma by acting on the Wnt/β-catenin pathway

A sub-population of chemoresistant cells exhibits biological properties similar to cancer stem cells (CSCs), and these cells are believed to be a main cause for tumor relapse and metastasis. In our study, we explored the role of SOX8 and its molecular mechanism in the regulation of the stemness properties and the epithelial mesenchymal transition (EMT) of cisplatin-resistant tongue squamous cell carcinoma (TSCC) cells. We found that SOX8 was upregulated in cisplatin-resistant TSCC cells, which displayed CSC-like properties and exhibited EMT. SOX8 was also overexpressed in chemoresistant patients with TSCC and was associated with higher lymph node metastasis, advanced tumor stage and shorter overall survival. Stable knockdown of SOX8 in cisplatin-resistant TSCC cells inhibited chemoresistance, tumorsphere formation, and EMT. The Wnt/β-catenin pathway mediated the cancer stem-like properties in cisplatin-resistant TSCC cells. Further studies showed that the transfection of active β-catenin in SOX8 stable-knockdown cells partly rescued the SOX8 silencing-induced repression of stem-like features and chemoresistance. Through chromatin immunoprecipitation and luciferase assays, we observed that SOX8 bound to the promoter region of Frizzled-7 (FZD7) and induced the FZD7-mediated activation of the Wnt/β-catenin pathway. In summary, SOX8 confers chemoresistance and stemness properties and mediates EMT processes in chemoresistant TSCC via the FZD7-mediated Wnt/β-catenin pathway.

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.