Expansion and characterization of cancer stem-like cells in squamous cell carcinoma of the head and neck. Oral Oncol. 2009;45:633-639. [PMID: 19027347 DOI: 10.1016/j.oraloncology.2008.10.003]

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.

Exploring olfactory receptor family 7 subfamily C member 1 as a novel oral cancer stem cell target for immunotherapy

The mortality rate of oral cancer has not improved over the past three decades despite remarkable advances in cancer therapies. Oral cancers contain a subpopulation of cancer stem cells (CSCs) that share characteristics associated with normal stem cells, including self-renewal and multi-differentiation potential. CSCs are tumorigenic, play a critical role in cancer infiltration, recurrence, and distant metastasis, and significantly contribute to drug resistance to current therapeutic strategies, including immunotherapy. Cytotoxic CD8+ T lymphocytes (CTLs) are key immune cells that effectively recognize peptide antigens presented by the major histocompatibility complex class I molecules. Increasing evidence suggests that cancer antigen-specific targeting by CTLs effectively regulates CSCs that drive cancer progression. In this study, we utilized data from public domains and performed various bioassays on human oral squamous cell carcinoma clinical samples and cell lines, including HSC-2 and HSC-3, to investigate the potential role of olfactory receptor family 7 subfamily C member 1 (OR7C1), a seven transmembrane G-protein-coupled olfactory receptor that is also expressed in nonolfactory tissues and was previously reported as a novel marker and target of colon cancer initiating cell-targeted immunotherapy, in CSC-targeted treatment against oral cancer. We found that the OR7C1 gene was expressed only in oral CSCs, and that CTLs reacted with human leukocyte antigen-A24-restricted OR7C1 oral CSC-specific peptides. Taken together, our findings suggest that OR7C1 represents a novel target for potent CSC-targeted immunotherapy in oral cancer.

Interplay between EZH2/β-catenin in stemness of cisplatin-resistant HNSCC and their role as therapeutic targets

The Wnt/β-catenin signaling pathway is associated with the regulation of cancer stem cells, and it can be driven by epigenetic modifications. Here, we aim to identify epigenetic modifications involved in the control of the Wnt/β-catenin signaling and investigate the role of this pathway in the accumulation of cancer stem cells (CSC) and chemoresistance of Head and Neck Squamous Cell Carcinoma (HNSCC). Quantitative-PCR, western blot, shRNA assay, viability assay, flow cytometry assay, spheres formation, xenograft model, and chromatin immunoprecipitation were employed to evaluate the Wnt/β-catenin pathway and EZH2 in wild-type and chemoresistant oral carcinoma cell lines, and in the populations of CSC and non-stem cells. We demonstrated that β-catenin and EZH2 were accumulated in cisplatin-resistant and CSC population. The upstream genes of the Wnt/β-catenin signaling (APC and GSK3β) were decreased, and the downstream gene MMP7 was increased in the chemoresistant cell lines. The inhibition of β-catenin and EZH2 combined effectively decreased the CSC population in vitro and reduced the tumor volume and CSC population in vivo. EZH2 inhibition increased APC and GSK3β, and the Wnt/β-catenin inhibition reduced MMP7 levels. In contrast, EZH2 overexpression decreased APC and GSK3β and increased MMP7. EZH2 and β-catenin inhibitors sensitized chemoresistant cells to cisplatin. EZH2 and H3K27me3 bounded the promoter of APC, leading to its repression. These results suggest that EZH2 regulates β-catenin by inhibiting the upstream gene APC contributing to the accumulation of cancer stem cells and chemoresistance. Moreover, the pharmacological inhibition of the Wnt/β-catenin combined with EZH2 can be an effective strategy for treating HNSCC.

Novel Stemness-Related Gene Signature Predicting Prognosis and Indicating a Different Immune Microenvironment in HNSCC

Background: The head and neck squamous cell carcinomas (HNSCC) is one of the most frequent cancers in the world, with an unfavorable prognosis. Cancer stem cells (CSCs) have been found to be responsible for HNSCC recurrence and therapeutic resistance.

Methods: The stemness of HNSCC was measured using a stemness index based on mRNA expression (mRNAsi). Stemness-related genes were discovered using weighted gene co-expression network analysis, least absolute shrinkage and selection operator analysis, and Cox regression, and a stemness-related prognostic index (SPI) was constructed. This research was based on TCGA and GSE65858.

Results: Stemness was found upregulated in HNSCC compared with normal tissues. The risk score model including five stemness-related genes exhibited a good accuracy in predicting outcomes. High SPI predicted a shorter overall survival (OS) in HNSCC patients, in the meantime, also demonstrated a lower CD8+ T cell infiltration and a higher enrichment of macrophages and fibroblasts than the low-SPI group, focusing on several up-regulated pathways such as epithelial mesenchymal transition (EMT), MYC targets v1, E2F targets, mTORC1 signaling, hypoxia, MYC targets v2, angiogenesis, G2M checkpoint, and glycolysis.

Conclusion: The SPI signature, which includes five stemness-related genes, could be utilized as a prognostic biomarker for HNSCC, implying that stemness may impact HNSCC immunologic profiles and be a feasible therapeutic target.

CD44-positive cancer stem cells from oral squamous cell carcinoma exhibit reduced proliferation and stemness gene expression upon adipogenic induction

We proposed to assess adipogenic differentiation and its effect on the proliferation and stemness markers in CD44 + OSCC CSCs. D44 + CSCs were sorted by magnetic sorting from the single-cell suspension of the OSCC tumor. Adipogenic differentiation was induced by an adipogenic induction medium. Lipid droplet formation was confirmed by oil red O staining. The expression of the cell surface marker was analyzed by flow cytometry. Real-time qPCR was performed to examine the gene expression activity. CD44 + OSCC CSCs can differentiate into adipocytes and adipogenesis in these cells decrease their proliferation and stemness gene expression. Adipogenic induction can make the cancer stem cells from OSCC tumors lose their stemness potential. Oral cancer, especially OSCC, is a huge burden worldwide. Similar to other stem cells, cancer stem cells can differentiate into other lineage cells. Our study shows that the proliferation and stemness gene expression in the CSCs from OSCC tumors can be thwarted by inducing them to differentiate into adipocytes, which could be advantageous to find out new clinical approaches in the treatment of cancers, like OSCC.

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.

Heterogeneity of Cancer Stem Cells in Tumorigenesis, Metastasis, and Resistance to Antineoplastic Treatment of Head and Neck Tumours

The discovery of a small subset of cancer cells with self-renewal properties that can give rise to phenotypically diverse tumour populations has shifted our understanding of cancer biology. Targeting cancer stem cells (CSCs) is becoming a promising therapeutic strategy in various malignancies, including head and neck squamous cell carcinoma (HNSCC). Diverse sub-populations of head and neck cancer stem cells (HNCSCs) have been identified previously using CSC specific markers, the most common being CD44, Aldehyde Dehydrogenase 1 (ALDH1), and CD133, or by side population assays. Interestingly, distinct HNCSC subsets play different roles in the generation and progression of tumours. This article aims to review the evidence for a role of specific CSCs in HNSCC tumorigenesis, invasion, and metastasis, together with resistance to treatment.

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.

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.

Identifying 8-mRNAsi Based Signature for Predicting Survival in Patients With Head and Neck Squamous Cell Carcinoma via Machine Learning

Cancer stem cells (CSCs) have been characterized by several exclusive features that include differentiation, self-renew, and homeostatic control, which allows tumor maintenance and spread. Recurrence and therapeutic resistance of head and neck squamous cell carcinomas (HNSCC) have been identified to be attributed to CSCs. However, the biomarkers led to the development of HNSCC stem cells remain less defined. In this study, we quantified cancer stemness by mRNA expression-based stemness index (mRNAsi), and found that mRNAsi indices were higher in HNSCC tissues than that in normal tissue. A significantly higher mRNAsi was observed in HPV positive patients than HPV negative patients, as well as in male patients than in female patients. The 8-mRNAsi signature was identified from the genes in two modules which were mostly related to mRNAsi screened by weighted gene co-expression network analysis. In this prognostic signatures, high expression of RGS16, LYVE1, hnRNPC, ANP32A, and AIMP1 focus in promoting cell proliferation and tumor progression. While ZNF66, PIK3R3, and MAP2K7 are associated with a low risk of death. The riskscore of eight signatures have a powerful capacity for 1-, 3-, 5-year of overall survival prediction (5-year AUC 0.77, 95% CI 0.69-0.85). These findings based on stemness indices may provide a novel understanding of target therapy for suppressing HNSCC stem cells.

Expression profile of stem cell markers and ABC transporters in 5-fluorouracil resistant Hep-2 cells

Resistance of laryngeal squamous cell carcinoma cells to traditional therapeutic regimens still remains to be a major reason for therapeutic failure in patients. In this study, we aimed at investigating the expression profiles of ATP-binding cassette (ABC) transporters and stem cell markers in 5-fluorouracil (5-FU) resistant laryngeal Hep-2 cells. We treated parental Hep-2 cells, with stepwise increased doses of 5-FU for almost 1 year to develop 5-FU resistant sub-lines with resistance against varying levels of 5-FU concentrations (4 sub-lines resistant to 1, 2, 4, and eightfold of 5-FU). Then, we measured the expression levels of 10 genes from ABC transporters family and 4 stem cell associated markers using quantitative reverse transcription polymerase chain reaction (qRT-PCR) to find out a potential relationship between these markers and chemoresistance. We found that stemness-associated markers had elevated expressions from the beginning of 5-FU resistance acquisition. Their expressions elevated stepwise while parental Hep-2 cells got resistance to higher doses of 5-FU. Expressions of tested ABC transporters (ABCA5, ABCB1, ABCB6, ABCC1, ABCC2, ABCC3, ABCC5, ABCC10 and ABCF2, and ABCG2) were also deregulated in 5-FU resistant Hep-2 cells. Although their expressions remained unaltered at the beginning of acquisition of resistance, expressions of ABC transporters except from ABCB6 increased significantly when cells became resistant to higher doses of 5-FU. Our results suggest that enrichment of cells with stemness characteristics and upregulation of ABC transporters might be amongst the crucial contributors of chemoresistance in laryngeal cancer cells.

ZSCAN4 facilitates chromatin remodeling and promotes the cancer stem cell phenotype

Cancer stem cells (CSCs) are cells within tumors that maintain the ability to self-renew, drive tumor growth, and contribute to therapeutic resistance and cancer recurrence. In this study, we investigate the role of Zinc finger and SCAN domain containing 4 (ZSCAN4) in human head and neck squamous cell carcinoma (HNSCC). The murine Zscan4 is involved in telomere maintenance and genomic stability of mouse embryonic stem cells. Our data indicate that the human ZSCAN4 is enriched for, marks and is co-expressed with CSC markers in HNSCC. We show that transient ZSCAN4 induction for just 2 days increases CSC frequency both in vitro and in vivo and leads to upregulation of pluripotency and CSC factors. Importantly, we define for the first time the role of ZSCAN4 in altering the epigenetic profile and regulating the chromatin state. Our data show that ZSCAN4 leads to a functional histone 3 hyperacetylation at the promoters of OCT3/4 and NANOG, leading to an upregulation of CSC factors. Consistently, ZSCAN4 depletion leads to downregulation of CSC markers, decreased ability to form tumorspheres and severely affects tumor growth. Our study suggests that ZSCAN4 plays an important role in the maintenance of the CSC phenotype, indicating it is a potential therapeutic target in HNSCC.

The impact of photobiomodulation therapy on the biology and behavior of head and neck squamous cell carcinomas cell lines

Photobiomodulation therapy (PBMT) is an emerging therapeutic modality designed to prevent and treat chemotherapy-driven oral mucositis (OM). However, the response of tumor cells to the effects of PBMT remains poorly understood. Our study explores the effects of PBMT in head and neck squamous cell carcinoma (HNSCC) based on cellular proliferation, migration, and survival of tumor cells and its population of cancer stem cells (CSC). We explored the behavior of two HNSCC cell lines (HN6 and HN13) under two distinct conditions, a physiological growing condition (10% FBS), and under stress growing condition (2% FBS) prior to irradiation using diode laser (InGaAlP; MM Optics, São Carlos, SP, Brazil). Diode laser (660 nm) was applied with a power of 100 mW delivering a total energy per point of 0.24 J. MTT and wound healing test (scratch assay) were performed to evaluate, respectively, proliferation and migration of tumor cells. Clonogenic and spheres formation assays were also performed to evaluate the survival and percentage of CSC upon irradiation. Overall, we observed that PBMT does not exacerbate the behavior of HNSCC. We could only observe a decrease in cellular proliferation of one cell line (HN6) when cultured under nutritional stress conditions (p < .05). There were no significant differences between the control and the PBMT groups regarding cell migration, survival and the percentage of CSC. Collectively, our results suggest that in vitro administration of PBMT to HNSCC does not modify the behavior of tumor cells.

Effect of ethanol extracts of Antrodia cinnamomea on head and neck squamous cell carcinoma cell line

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignant tumors. Ethanol extract of Antrodia cinnamomea (EEA) has been widely studied for its health benefits including anticancer effects. The purpose of this study was to assess the effects of EEA on HNSCC. Cell proliferation, transwell, and wound healing assays were performed. The impact of EEA on tumor growth was investigated using a xenograft model. Expressions of migration-related proteins (MMP-2, MMP-9, TIMP-1, and TIMP-2) and apoptosis-related proteins (cleaved caspase-9 and cleaved PARP) were determined using western blot analysis. The results indicated that EEA significantly inhibited the capacities of proliferation, invasion, and migration of HNSCC cells in a dose-dependent manner. Cleaved caspase-9 and cleaved PARP expressions were increased in cells treated with an increasing concentration of EEA, which suggested that EEA induced apoptosis of HNSCC. MMP-2 and MMP-9 were downregulated when cells were administered EEA, while TIMP-1 and TIMP-2 were not affected, which uncovered the mechanisms mediating the EEA-induced inhibition on cell invasion and migration. The animal experiment also suggested that EEA inhibited tumor growth. Our study confirmed the inhibitive effects of EEA on cell proliferation, invasion, and migration of HNSCC in vitro and in vivo, providing the basis for further study of the application of EEA as an effective candidate for cancer treatment.

Stem cell markers in oral and oropharyngeal squamous cell carcinomas in relation to the site of origin and HPV infection: clinical implications

The expression of potential stem cell markers in HNSCCs was investigated to assess their potential clinical role. 69 primary, previously untreated oral (OSCC) and oropharyngeal squamous cell carcinomas (OPSCC) were enrolled; personal, clinical and follow-up data were collected. HPV infection and expression of 5 potential stem cell markers (CD44, CD133, Oct-4, Nanog, and Sox-2) were evaluated. HPV+ OPSCC showed lower expression of Nanog. The cytoplasmic expression of Nanog was associated with significantly worse prognosis in OPSCC, but not in OSCC. Sox-2 staining was more intense among OPSCCs. Sox-2 nuclear staining was associated with worse prognosis. Nanog expression was associated with HPV- OPSCC and may have a role as a surrogate diagnostic marker. In general, the expression profile of some stem cell markers in HNSCC seems to vary according to the site of origin and HPV infection. Nanog and Sox-2 may also have prognostic value.

Dihydroartemisinin Prevents Distant Metastasis of Laryngeal Carcinoma by Inactivating STAT3 in Cancer Stem Cells

Background

Accumulating evidence indicates that cancer stem cells (CSCs) are a minor subpopulation of cancer cells that may be the primary source of cancer invasion, migration, and widespread metastasis.

Material/Methods

We investigated the effects of dihydroartemisinin (DHA) on distant metastasis of laryngeal carcinoma and the relevant mechanism. In vitro, we used the Hep-2 human laryngeal squamous carcinoma cell line (Hep-2 cells) to assemble CSCs, using CD133 as the cell surface marker. Our data demonstrate that the CD133⁺ subpopulation of Hep-2 cells has greater invasion and migration capabilities than CD133⁻ cells. We also evaluated the effects of DHA, a newly defined STAT3 inhibitor, on the invasion and migration of CD133⁺ Hep-2 cells under hypoxia and IL-6 stimulation, both of which can activate STAT3 phosphorylation.

Results

CSCs exhibited a significant decrease in the ability of migration and invasion upon the application of DHA, along with simultaneous alterations in related proteins, both in cultured cells and in xenograft tumors. The associated signaling proteins included phosphorylated STAT3 (p-STAT3), matrix metalloproteinase-9 (MMP-9), and E-cadherin, which are closely involved in cancer invasion and metastasis. In vivo, we found that DHA can reduce lung metastasis formation caused by CSCs and prolong survival in mice, and can inhibit STAT3 activation, downregulate MMP-9, and upregulate E-cadherin in lung metastatic tumors.

Conclusions

Taken together, our findings indicate that CSCs possess stronger invasive and metastatic capabilities than non-CSCs, and DHA inhibits invasion and prevents metastasis induced by CSCs by inhibiting STAT3 activation.

Immunoregulatory Potential of Exosomes Derived from Cancer Stem Cells

Head and neck squamous cell carcinomas (HNSCCs) are malignancies that originate in the mucosal lining of the upper aerodigestive tract. Despite advances in therapeutic interventions, survival rates among HNSCC patients have remained static for years. Cancer stem cells (CSCs) are tumor-initiating cells that are highly resistant to treatment, and are hypothesized to contribute to a significant fraction of tumor recurrences. Consequently, further investigations of how CSCs mediate recurrence may provide insights into novel druggable targets. A key element of recurrence involves the tumor's ability to evade immunosurveillance. Recent published reports suggest that CSCs possess immunosuppressive properties, however, the underlying mechanism have yet to be fully elucidated. To date, most groups have focused on the role of CSC-derived secretory proteins, such as cytokines and growth factors. Here, we review the established immunoregulatory role of exosomes derived from mixed tumor cell populations, and propose further study of CSC-derived exosomes may be warranted. Such studies may yield novel insights into new druggable targets, or lay the foundation for future exosome-based diagnostics.

Fibroblasts-dependent invasion of podoplanin-positive cancer stem cells in squamous cell carcinoma

To clear whether podoplanin-positive cancer stem cells in squamous cell carcinoma have higher invasion activity during a fibroblasts-dependent invasion. A collagen gel invasion assay was performed using fluorescent ubiquitination-based cell cycle indicator-labeled A431 cells. The total number and number of invading cells in S/G2/M phase were counted using time-lapse imaging cocultured with fibroblasts. There was no significant difference between the number of invading podoplanin-positive and negative A431 cells when fibroblasts did not exist. On the contrary, the number of invading podoplanin-positive cells was significantly higher when fibroblasts existed. The frequency of cells in S/G2/M phase among invasion was no difference. Knockdown of podoplanin decreased the number of invaded A431 cells significantly when fibroblasts existed. Podoplanin-positive A431 cells display higher invasion activity when fibroblasts exist, suggesting that some biological functions of cancer stem cells might become evident only within the fibrous tumor microenvironment.

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.

CD44-Targeted Magnetic Nanoparticles Kill Head And Neck Squamous Cell Carcinoma Stem Cells In An Alternating Magnetic Field

Background

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignant tumor in the world. Studies in recent years have demonstrated that cancer stem cells (CSCs) are present in many tumor tissues, including HNSCC, and CSCs are the root cause of tumor recurrence and metastasis. Thus, taking new treatment measures to target the killing of CSCs that are resistant to chemotherapy and radiotherapy is key to the success of cancer treatment.

Methods

We explored a method for preparing anti-CD44 antibody-modified superparamagnetic iron oxide nanoparticles (SPIONPs). Biocompatibility was evaluated by a CCK-8 assay. The CSCs were obtained by a 3D cell culture technique from Cal-27 (human oral squamous cell carcinoma) cells, and then the CSCs were identified by quantitative real-time polymerase chain reaction (qRT-PCR). The targeting efficiency of the CD44-SPIONPs to CSCs was confirmed by Prussian blue staining and visualized by laser scanning confocal microscopy (LSCM). Flow cytometry was used to detect the apoptosis of CSCs after alternating magnetic field (AMF) treatment. The efficacy of tumor growth inhibition by CD44-SPIONP-mediated magnetic hyperthermia therapy was evaluated with tumor xenografts in nude mice.

Results

The CD44-SPIONPs exhibited no negative effect on CSCs, indicating good biocompatibility. After SPIONPs were cocultured with stem cells, the majority of CD44-SPIONPs labeled with FITC penetrated the cell membrane into the cytoplasm. After AMF treatment, CD44-SPIONPs induced CSCs to undergo programmed death. The inhibitory ratio of the treated group was 33.43%, and necrotic areas in the tumor tissue were mainly distributed around the magnetic fluid.

Conclusion

These results demonstrate that it is possible to kill CSCs using targeted magnetic nanoparticles and an AMF and that magnetic fluid hyperthermia significantly inhibited the growth of grafted Cal-27 tumors in mice.

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

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

Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma: Identification, Characterization and Clinical Implications

Head and neck squamous cell carcinoma (HNSCC) is the sixth most commonly diagnosed cancer worldwide. Despite advances in the treatment management, locally advanced disease has a poor prognosis, with a 5-year survival rate of approximately 50%. The growth of HNSCC is maintained by a population of cancer stem cells (CSCs) which possess unlimited self-renewal potential and induce tumor regrowth if not completely eliminated by therapy. The population of CSCs is not only a promising target for tumor treatment, but also an important biomarker to identify the patients at risk for therapeutic failure and disease progression. This review aims to provide an overview of the recent pre-clinical and clinical studies on the biology and potential therapeutic implications of HNSCC stem cells.

Heterogeneity of Head and Neck Squamous Cell Carcinoma Stem Cells

Current systemic cancer treatment in head and neck squamous cell carcinoma (HNSCC) is moving toward more personalized approaches such as de-escalation protocols human-papilloma-virus dependent HNSCC or application of checkpoint inhibitors. However, these treatments have been challenged by cancer stem cells (CSC), a small population within the bulk tumor, which are leading to treatment failure, tumor recurrence, or metastases. This review will give an overview of the characteristics of HNSCC-CSC. Specifically, the mechanisms by which HNSCC-CSC induce tumor initiation, progression, recurrence, or metastasis will be discussed. Although evidence-based treatment options targeting HNSCC-CSC specifically are still being sought for, they warrant a promise for additional and sustainable treatment options where for HNSCC patients where others have failed.

Therapeutic potency of oncolytic virotherapy-induced cancer stem cells targeting in brain tumors, current status, and perspectives

Brain tumors are the most common form of solid tumors in children and is presently a serious therapeutic challenge worldwide. Traditional treatment with chemotherapy and radiotherapy was shown to be unsuccessful in targeting brain tumor cancer stem cells (CSCs), leading to recurrent, treatment-resistant secondary malignancies. Oncolytic virotherapy (OV) is an effective antitumor therapeutic strategy which offers a novel, targeted approach for eradicating pediatric brain tumor CSCs by utilizing mechanisms of cell killing that differ from conventional therapies. A number of studies and some clinical trials have therefore investigated the effects of combined therapy of radiations or chemotherapies with oncolytic viruses which provide new insights regarding the effectiveness and improvement of treatment responses for brain cancer patients. This review summarizes the current knowledge of the therapeutic potency of OVs-induced CSCs targeting in the treatment of brain tumors for a better understanding and hence a better management of this disease.

Cellular Plasticity-Targeted Therapy in Head and Neck Cancers

Head and neck cancer is one of the most frequent human malignancies worldwide, with a high rate of recurrence and metastasis. Head and neck squamous cell carcinoma (HNSCC) is cellularly and molecularly heterogeneous, with subsets of undifferentiated cancer cells exhibiting stem cell-like properties, called cancer stem cells (CSCs). Epithelial-mesenchymal transition, gene mutation, and epigenetic modification are associated with the formation of cellular plasticity of tumor cells in HNSCC, contributing to the acquisition of invasive, recurrent, and metastatic properties and therapeutic resistance. Tumor microenvironment (TME) plays a supportive role in the initiation, progression, and metastasis of head and neck cancer. Stromal fibroblasts, vasculature, immune cells, cytokines, and hypoxia constitute the main components of TME in HNSCC, which contributes not only to the acquisition of CSC properties but also to the recurrence and therapeutic resistance of the malignancies. In this review, we discuss the potential mechanisms underlying the development of cellular plasticity, especially the emergence of CSCs, in HNSCC. We also highlight recent studies implicating the complex interplays among TME components, plastic CSCs, tumorigenesis, recurrence, and therapeutic resistance of HNSCC. Finally, we summarize the treatment modalities of HNSCC and reinforce the novel concept of therapeutic targeting CSCs in HNSCC.

Acetylshikonin suppresses invasion of Porphyromonas gingivalis‑infected YD10B oral cancer cells by modulating the interleukin-8/matrix metalloproteinase axis

The development of pharmaceutical agents possessing anti‑invasive and anti‑metastatic abilities, as well as apoptotic activity, is important in decreasing the incidence and recurrence of oral cancer. Cancer cells are known to acquire invasiveness not only through epigenetic changes, but also from inflammatory stimuli within the tumor microenvironment. Accordingly, the identification of agents that can suppress the inflammation‑promoted invasiveness of cancer cells may be important in treating cancer and improving the prognosis of patients with cancer. Acetylshikonin, a flavonoid with anti‑inflammatory activity, inhibits proliferation and induces apoptosis of oral cancer cells. In the present study, the anti‑invasive effect of acetylshikonin on YD10B oral cancer cells infected with Porphyromonas gingivalis, a major pathogen of chronic periodontitis, and the mechanisms involved were investigated. Firstly, we examined whether P. gingivalis infection increased the invasiveness of YD10B cells. Results suggested that YD10B oral cancer cells become more aggressive when they are infected with P. gingivalis. Secondly, acetylshikonin significantly inhibited the invasion of P. gingivalis‑infected YD10B cells by suppressing IL‑8 release and IL‑8‑dependent MMP release. These data suggest that acetylshikonin may be a useful preventive and therapeutic candidate for oral cancer that is chronically infected with periodontal pathogens.

Targeted photodynamic therapy as potential treatment modality for the eradication of colon cancer and colon cancer stem cells

Colorectal cancer is commonly treated by tumour resection, as chemotherapy and radiation have proven to be less effective, especially if the tumour has metastasized. Resistance to therapies occurs in almost all patients with colorectal cancer, especially in those with metastatic tumours. Cancer stem cells have the ability to self-renew, and their slow rate of cycling enhances resistance to treatment and increases the likelihood of tumour recurrence. Most metastatic tumours are unable to be surgically removed, thus creating a need for treatment modalities that target cancers directly and destroy cancer stem cells. Photodynamic therapy involves a photosensitizer that when exposed to a light source of a particular wavelength becomes excited and produces a form of oxygen that kills cancer cells. Photodynamic therapy is currently being investigated as a treatment modality for colorectal cancer, and new studies are exploring enhancing photodynamic therapy efficacy with the aid of drug carriers and immune conjugates. These modifications could prove effective in targeting cancer stem cells that are thought to be resistant to photodynamic therapy. In order for photodynamic therapy to be an effective treatment in colorectal cancer, it requires treatment of both primary tumours and the metastatic secondary disease that is caused by colon cancer stem cells. This review focuses on current photodynamic therapy treatments available for colorectal cancer and highlights proposed actively targeted photosynthetic drug uptake mechanisms specifically mediated towards colon cancer stem cells, as well as identify the gaps in research which need to be investigated in order to develop a combinative targeted photodynamic therapy regime that can effectively control colorectal cancer primary and metastatic tumour growth by eliminating colon cancer stem cells.

Epigenetic therapy regulates the expression of ALDH1 and immunologic response: Relevance to the prognosis of oral cancer

OBJECTIVES

Aldehyde dehydrogenase 1 (ALDH1) is associated with tumorigenesis, and shown to identify cancer stem cells (CSC)-like cells. We aimed to investigate the significance of ALDH1 in oral squamous cell carcinoma (OSCC) and its correlation with DNMT3b and immune evasion in the present study.

METHODS

We retrospectively analyzed the clinical outcomes of OSCC patients and examined its correlation with the levels of ALDH1 in tumors and circulating myeloid-derived suppressor cells (MDSCs) in the peripheral blood. Furthermore, the relationships between the DNMT3b, ALDH1 expression, and immune response were examined via clinical specimens and cellular and animal experiments. We also investigated the therapeutic potential of DNA hypomethylating agents in OSCC.

RESULTS

Our data revealed that the levels of ALDH1 expression were linked to treatment resistance, CSC-like properties, higher circulating MDSC and poor prognosis for OSCC. The radiation resistance noted in ALDH1-positive tumors was associated with augmented radiation-induced increases in the expression of programmed death ligand (PD-L1) and the activation of MDSCs. Furthermore, there was a positive link between ALDH1 and DNMT3b expression shown by clinical specimens and cellular experiments. DNA hypomethylating agents attenuated the radioresistance of ALDH1-positive cancer cells associated with the decreased ALDH1 and the increased DNA damages. In addition, the activation of MDSCs and the expression of PD-L1 were significantly attenuated by epigenetic therapy.

CONCLUSIONS

Our findings suggested that ALDH1 played an important role in treatment response and the tumor-promoting microenvironment in OSCC. Moreover, epigenetic therapy could be a promising strategy for the treatment of OSCC.

A modified method by differential adhesion for enrichment of bladder cancer stem cells

Purpose:

In a previous study the vaccine was effective against bladder cancer in a mouse model. However, a small portion of tumors regrew because the vaccine could not eliminate bladder cancer stem cells (CSCs). In this study, we showed a modified method for the isolation of bladder CSCs using a combination of differential adhesion method and serum-free culture medium (SFM) method.

Materials and Methods:

Trypsin-resistant cells and trypsin-sensitive cells were isolated from MB49, EJ and 5637 cells by a combination of differential adhesion method and SFM method. The CSCs characterizations of trypsin-resistant cells were verified by the flow cytometry, the western blotting, the quantitative polymerase chain reaction, the resistance to chemotherapy assay, the transwell assay, and the tumor xenograft formation assay.

Results:

Trypsin-resistant cells were isolated and identified in CSCs characters, with high expression of CSCs markers, higher resistance to chemotherapy, greater migration in vitro, and stronger tumorigenicity in vivo.

Conclusion:

Trypsin-resistant cells displayed specific CSCs properties. Our study showed trypsin-resistant cells were isolated successfully with a modified method using a combination of differential adhesion method and SFM method.

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.

Trending Speculations of Tumor-Initiating Cells in Squamous Cell Cancers of Head and Neck

Tumor-initiating cells are a diminutive subpopulation of stem cells that have ability of long term self-renewal and generation of varied traits of tumor cell population. Understanding the concept of tumor-initiating cells may have a great implicative intimation for our comprehension of cancer pathobiology and for the delineation of new therapies directed towards these stem cells. The present review is an endeavor to conceptualize the role of tumor-initiating cells in the Squamous Cell Cancers (SCC) of head and neck, their role in tumorigenesis and the possible supplementary approach in the latest treatment modalities.

Overcoming radioresistance in head and neck squamous cell carcinoma

Radiation therapy plays an essential role in the treatment of head and neck squamous cell carcinoma (HNSCC), yet therapeutic efficacy is hindered by treatment-associated toxicity and tumor recurrence. In comparison to other cancers, innovation has proved challenging, with the epidermal growth factor receptor (EGFR) antibody cetuximab being the only new radiosensitizing agent approved by the FDA in over half a century. This review examines the physiological mechanisms that contribute to radioresistance in HNSCC as well as preclinical and clinical data regarding novel radiosensitizing agents, with an emphasis on those with highest translational promise.

Cancer stem cells and personalized cancer nanomedicine

Despite the progress in cancer treatment over the past years advanced cancer is still an incurable disease. Special attention is pointed toward cancer stem cell (CSC)-targeted therapies, because this minor cell population is responsible for the treatment resistance, metastatic growth and tumor recurrence. The recently described CSC dynamic phenotype and interconversion model of cancer growth hamper even more the possible success of current cancer treatments in advanced cancer stages. Accordingly, CSCs can be generated through dedifferentiation processes from non-CSCs, in particular, when CSC populations are depleted after treatment. In this context, the use of targeted CSC nanomedicines should be considered as a promising tool to increase CSC sensitivity and efficacy of specific anti-CSC therapies.

Targeting head and neck tumoral stem cells: From biological aspects to therapeutic perspectives

Head and neck squamous cell cancer (HNSCC) is the sixth most common cancer in the world. Effective therapeutic modalities such as surgery, radiation, chemotherapy and combinations of each are used in the management of the disease. In most cases, treatment fails to obtain total cancer cure. In recent years, it appears that one of the key determinants of treatment failure may be the presence of cancer stem cells (CSCs) that escape currently available therapies. CSCs form a small portion of the total tumor burden but may play a disproportionately important role in determining outcomes. CSCs have stem features such as self-renewal, high migration capacity, drug resistance, high proliferation abilities. A large body of evidence points to the fact that CSCs are particularly resistant to radiotherapy and chemotherapy. In HNSCC, CSCs have been increasingly shown to have an integral role in tumor initiation, disease progression, metastasis and treatment resistance. In the light of such observations, the present review summarizes biological characteristics of CSCs in HNSCC, outlines targeted strategies for the successful eradication of CSCs in HNSCC including targeting the self-renewal controlling pathways, blocking epithelial mesenchymal transition, niche targeting, immunotherapy approaches and highlights the need to better understand CSCs biology for new treatments modalities.

Isolation and Characterization of Cancer Stem Cells from Primary Head and Neck Squamous Cell Carcinoma Tumors

Drug resistance remains a significant problem in the treatment of patients with head and neck squamous cell carcinoma (HNSCC). Recent reports showed that a subpopulation of highly tumorigenic cells, called cancer stem cells (CSCs), is uniquely resistant to chemotherapy, suggesting that these cells play an important role in the relapse of HNSCC. The development of methods for the isolation and culture of cancer stem cells is a key step to enable studies exploring the mechanisms underlying the role of these cells in chemoresistance. Here, we describe a method to isolate cancer stem cells from primary head and neck tumors and for the generation of orospheres.

Development of a therapy against metastatic bladder cancer using an interleukin-2 surface-modified MB49 bladder cancer stem cells vaccine

Introduction

In previous study the streptavidin interleukin-2 (SA-IL-2)-modified MB49 vaccine was effective against bladder cancer in a mouse model. However, a small portion of tumors regrew because the vaccine could not eliminate MB49 bladder cancer stem cells (MCSCs). Accordingly, we developed a SA-IL-2-modified MCSCs vaccine and evaluated its antitumor effects.

Methods

MCSCs were isolated and identified in cancer stem cells (CSCs) characters, with high expression of CSCs markers, higher resistance to chemotherapy, greater migration in vitro, and stronger tumorigenicity in vivo. The SA-IL-2 MCSCs vaccine was prepared and its bioactivity was evaluated. The protective, therapeutic, specific and memory immune response in animal experiments were designed to identify whether the vaccine elicited antitumor immunity and acted against metastatic bladder cancer.

Results

MCSCs had higher level of CD133 and CD44, less susceptibility to chemotherapy, more pronounced migration and greater tumorigenic ability. The successfully prepared SA-IL-2 MCSCs vaccine inhibited the tumor volume and prolonged mice survival in animal experiments. The expression of IgG, the population of dendritic cells, CD8⁺ and CD4⁺ T cells were highest in the experimental group than in the four control groups.

Conclusions

The SA-IL-2 MCSCs vaccine induced an antitumor immune response and was used to eliminate MCSCs to prevent tumor regrowth.

Common stemness regulators of embryonic and cancer stem cells

Pluripotency of embryonic stem cells (ESCs) and induced pluripotent stem cells is regulated by a well characterized gene transcription circuitry. The circuitry is assembled by ESC specific transcription factors, signal transducing molecules and epigenetic regulators. Growing understanding of stem-like cells, albeit of more complex phenotypes, present in tumors (cancer stem cells), provides a common conceptual and research framework for basic and applied stem cell biology. In this review, we highlight current results on biomarkers, gene signatures, signaling pathways and epigenetic regulators that are common in embryonic and cancer stem cells. We discuss their role in determining the cell phenotype and finally, their potential use to design next generation biological and pharmaceutical approaches for regenerative medicine and cancer therapies.

Expression of Oct3/4 and Nanog in the head and neck squamous carcinoma cells and its clinical implications for delayed neck metastasis in stage I/II oral tongue squamous cell carcinoma

BACKGROUND

The side population (SP) of cancer cells is reportedly enriched with cancer stem cells (CSCs), however, the functional role and clinical relevance of CSC marker molecules upregulated in the SP of head and neck squamous carcinoma (HNSCC) cells are yet to be elucidated. Patients with clinical stage I/II (T1-2N0M0) tongue squamous cell carcinoma (TSCC) typically undergo partial glossectomy; however, development of delayed neck metastasis (DNM) tends to reduce their survival. In the present study, we aimed to determine the CSC markers in the SP of HNSCC cells along with their functions in cellular behaviors, and to clarify the association of these markers with DNM.

METHODS

Flow cytometry was applied to isolate SP from main population (MP) in HNSCC cells. The expression of the CSC markers was examined by semi-quantitative RT-PCR and immunocytochemistry. In vitro proliferation, migration, and invasion assays were performed to assess cellular behaviors. Clinicopathological factors and immunohistochemical expressions of Oct3/4 and Nanog were evaluated using surgical specimens from 50 patients with stage I/II TSCC.

RESULTS

SPs were isolated in all three cell lines examined. Expression levels of Oct3/4 and Nanog were higher in SP cells than MP cells. Additionally, cell migration and invasion abilities were higher in SP cells than MP cells, whereas there was no difference in proliferation. Univariate analysis showed that expression of Oct3/4 and Nanog, vascular and muscular invasion, and mode of invasion were significantly correlated with DNM. Multivariate logistic regression revealed that Oct3/4 expression (risk ratio = 14.78, p = 0.002) and vascular invasion (risk ratio = 12.93, p = 0.017) were independently predictive of DNM. Regarding the diagnostic performance, Oct3/4 showed the highest accuracy, sensitivity, and NPV of 82.0 %, 61.5 %, and 86.8 %, respectively, while vascular invasion showed the highest specificity and PPV of 94.6 % and 71.4 %, respectively.

CONCLUSION

These results suggest that Oct3/4 and Nanog represent probable CSC markers in HNSCC, which contribute to the development of DNM in part by enhancing cell motility and invasiveness. Moreover, along with vascular invasion, expression of Oct3/4 can be considered a potential predictor for selecting patients at high risk of developing DNM.

Enhancement of Cytotoxicity and Inhibition of Angiogenesis in Oral Cancer Stem Cells by a Hybrid Nanoparticle of Bioactive Quinacrine and Silver: Implication of Base Excision Repair Cascade

A poly(lactic-co-glycolic acid) (PLGA)-based uniform (50-100 nm) hybrid nanoparticle (QAgNP) with positive zeta potential (0.52 ± 0.09 mV) was prepared by single emulsion solvent evaporation method with bioactive small molecule quinacrine (QC) in organic phase and silver (Ag) in aqueous phase. Physiochemical properties established it as a true hybrid nanoparticle and not a mixture of QC and Ag. Antitumor activity of QAgNP was evaluated by using various cancer cell lines including H-357 oral cancer cells and OSCC-cancer stem cell in an in vitro model system. QAgNP caused more cytotoxicity in cancer cells than normal epithelial cells by increasing BAX/BCL-XL, cleaved product PARP-1, and arresting the cells at S phase along with DNA damage. In addition, QAgNPs offered greater ability to kill the OSCC-CSCs compared to NQC and AgNPs. QAgNP offered anticancer action in OSCC-CSCs by inhibiting the base excision repair (BER) within the cells. Interestingly, alteration of BER components (Fen-1 and DNA polymerases (β, δ, and ε) and unalteration of NHEJ (DNA-PKC) or HR (Rad-51) components was noted in QAgNP treated OSCC-CSC cells. Furthermore, QAgNP significantly reduced angiogenesis in comparison to physical mixture of NQC and AgNP in fertilized eggs. Thus, these hybrid nanoparticles caused apoptosis in OSCC-CSCs by inhibiting the angiogenesis and BER in cells.

Prolonged and repetitive exposure to Porphyromonas gingivalis increases aggressiveness of oral cancer cells by promoting acquisition of cancer stem cell properties

Periodontitis is the most common chronic inflammatory condition occurring in the human oral cavity, but our knowledge on its contribution to oral cancer is rather limited. To define crosstalk between chronic periodontitis and oral cancer, we investigated whether Porphyromonas gingivalis, a major pathogen of chronic periodontitis, plays a role in oral cancer progression. To mimic chronic irritation by P. gingivalis in the oral cavity, oral squamous cell carcinoma (OSCC) cells were infected with P. gingivalis twice a week for 5 weeks. Repeated infection of oral cancer cells by P. gingivalis resulted in morphological changes of host cancer cells into an elongated shape, along with the decreased expression of epithelial cell markers, suggesting acquisition of an epithelial-to-mesenchymal transition (EMT) phenotype. The prolonged exposure to P. gingivalis also promoted migratory and invasive properties of OSCC cells and provided resistance against a chemotherapeutic agent, all of which are described as cellular characteristics undergoing EMT. Importantly, long-term infection by P. gingivalis induced an increase in the expression level of CD44 and CD133, well-known cancer stem cell markers, and promoted the tumorigenic properties of infected cancer cells compared to non-infected controls. Furthermore, increased invasiveness of P. gingivalis-infected OSCC cells was correlated with enhanced production of matrix metalloproteinase (MMP)-1 and MMP-10 that was stimulated by interleukin-8 (IL-8) release. This is the first report demonstrating that P. gingivalis can increase the aggressiveness of oral cancer cells via epithelial-mesenchymal transition-like changes and the acquisition of stemness, implicating P. gingivalis as a potential bacterial risk modifier.

Targeting CD133 in the enhancement of chemosensitivity in oral squamous cell carcinoma-derived side population cancer stem cells

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most common cancers in the world. Previously, we enriched a subpopulation of OSCC-derived cancer stem cells (OSCC-CSCs), and identified CD133 as an OSCC-CSC marker.

METHOD

We determined the function of CD133 on chemosensitivity of oral cancer CSCs by silencing CD133.

RESULTS

Initially, we observed that the expression profile of CD133 in OSCC-side population (OSCC-SPs) cells, which exerted properties of CSCs, was significantly upregulated than that of major population (MPs) cells of OSCCs. The cell viability experiments showed that SPs were more chemoresistant compared with major populations. Importantly, targeting CD133 ameliorated the drug resistance of OSCC-SPs to cisplatin treatment. Targeting CD133 and cisplatin co-treatment led to the maximal inhibition on tumor initiating properties in OSCC-SPs.

CONCLUSION

Side population cells with CSCs properties existed in OSCCs, and silencing CD133 exhibited a prominent therapeutic effect in enhancing the sensitivity of chemotherapy in OSCC through elimination of CSCs. © 2015 Wiley Periodicals, Inc. Head Neck 38: E231-E238, 2016.

Cancer stem cells in head and neck squamous cell carcinoma: a review

Research indicates that a small population of cancer cells is highly tumorigenic, endowed with the capacity for self-renewal, and has the ability to differentiate into cells that constitute the bulk of tumors. These cells are considered the "drivers" of the tumorigenic process in some tumor types, and have been named cancer stem cells (CSC). Epithelial-mesenchymal transition (EMT) appears to be involved in the process leading to the acquisition of stemness by epithelial tumor cells. Through this process, cells acquire an invasive phenotype that may contribute to tumor recurrence and metastasis. CSC have been identified in human head and neck squamous cell carcinomas (HNSCC) using markers such as CD133 and CD44 expression, and aldehyde dehydrogenase (ALDH) activity. Head and neck cancer stem cells reside primarily in perivascular niches in the invasive fronts where endothelial-cell initiated events contribute to their survival and function. Clinically, CSC enrichment has been shown to be enhanced in recurrent disease, treatment failure and metastasis. CSC represent a novel target of study given their slow growth and innate mechanisms conferring treatment resistance. Further understanding of their unique phenotype may reveal potential molecular targets to improve therapeutic and survival outcomes in patients with HNSCC. Here, we discuss the state-of-the-knowledge on the pathobiology of cancer stem cells, with a focus on the impact of these cells on head and neck tumor progression, metastasis and recurrence due to treatment failure.

Targeting serum glucocorticoid-regulated kinase-1 in squamous cell carcinoma of the head and neck: a novel modality of local control

Purpose

The inhibition of serum glucocorticoid-regulated kinase-1 (SGK-1) has been found to decrease growth of colon and prostate cancer cells. The purpose of this study is to evaluate the therapeutic effect of SGK-1 inhibition in head and neck squamous cell carcinoma (SCC).

Experimental Design

Human head and neck tumors (HTB41/43) were established in athymic mice. Growth rates between mice treated with vehicle (PBS) injection (group 1, n = 5), SGK-1 Inhibitor GSK 650394 (group 2, n = 6), systemic cisplatin (group 3, n = 6), and a combination of SGK-1 Inhibitor and cisplatin (group 4, n = 6) were compared using repeated measures one-way ANOVA with Newman-Keuls Multiple Comparison Test. Tumor cells were subsequently submitted to further analyses.

Results

At the end of the experiment mean tumor sizes were 122.33+/−105.86, 76.73+/−36.09, 94.52+/−75.92, and 25.76+/−14.89 mm² (mean +/− SD) for groups 1 to 4. Groups 2 and 3 showed decreased tumor growth compared to controls (p<0.001). Group 4 displayed even greater growth suppression (p<0.0001). Importantly, group 4 fared better than group 3 (p<0.001). CD44 expression was reduced in group 2 (p<0.05), and to an even greater extent in groups 3 and 4 (p<0.0025). A trend towards reduction of HER 2 expression was noted in group 4.

Conclusions

SGK-1 inhibition suppresses tumor growth, and in combination with systemic cisplatin exceeds the effect of cisplatin alone. Decreased expression of CD44 and HER 2 implies depletion of tumor stem cells, and less tumorigenicity. SGK-1 inhibition represents a potential modality of local control for palliation in advanced cases.