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

Understanding the autophagic functions in cancer stem cell maintenance and therapy resistance

Complex tumour ecosystem comprising tumour cells and its associated tumour microenvironment (TME) constantly influence the tumoural behaviour and ultimately impact therapy failure, disease progression, recurrence and poor overall survival of patients. Crosstalk between tumour cells and TME amplifies the complexity by creating metabolic changes such as hypoxic environment and nutrient fluctuations. These changes in TME initiate stem cell-like programmes in cancer cells, contribute to tumoural heterogeneity and increase tumour robustness. Recent studies demonstrate the multifaceted role of autophagy in promoting fibroblast production, stemness, cancer cell survival during longer periods of dormancy, eventual growth of metastatic disease and disease resistance. Recent ongoing studies examine autophagy/mitophagy as a powerful survival strategy in response to environmental stress including nutrient deprivation, hypoxia and environmental stress in TME. It prevents irreversible senescence, promotes dormant stem-like state, induces epithelial-mesenchymal transition and increases migratory and invasive potential of tumour cells. The present review discusses various theories and mechanisms behind the autophagy-dependent induction of cancer stem cell (CSC) phenotype. Given the role of autophagic functions in CSC aggressiveness and therapeutic resistance, various mechanisms and studies based on suppressing cellular plasticity by blocking autophagy as a powerful therapeutic strategy to kill tumour cells are discussed.

Targeting anticancer immunity in oral cancer: Drugs, products, and nanoparticles

Oral cavity carcinomas are the most frequent malignancies among head and neck malignancies. Oral tumors include not only oral cancer cells with different potency and stemness but also consist of diverse cells, containing anticancer immune cells, stromal and also immunosuppressive cells that influence the immune system reactions. The infiltrated T and natural killer (NK) cells are the substantial tumor-suppressive immune compartments in the tumor. The infiltration of these cells has substantial impacts on the response of tumors to immunotherapy, chemotherapy, and radiotherapy. Nevertheless, cancer cells, stromal cells, and some other compartments like regulatory T cells (Tregs), macrophages, and myeloid-derived suppressor cells (MDSCs) can repress the immune responses against malignant cells. Boosting anticancer immunity by inducing the immune system or repressing the tumor-promoting cells is one of the intriguing approaches for the eradication of malignant cells such as oral cancers. This review aims to concentrate on the secretions and interactions in the oral tumor immune microenvironment. We review targeting tumor stroma, immune system and immunosuppressive interactions in oral tumors. This review will also focus on therapeutic targets and therapeutic agents such as nanoparticles and products with anti-tumor potency that can boost anticancer immunity in oral tumors. We also explain possible future perspectives including delivery of various cells, natural products and drugs by nanoparticles for boosting anticancer immunity in oral tumors.

SDCBP Modulates Stemness and Chemoresistance in Head and Neck Squamous Cell Carcinoma through Src Activation

Simple Summary

Drug resistance is the principal limiting factor to achieving good survival rates in patients with cancer. The identification of potential biomarkers for diagnosis and prognostic prediction, as well as the design of new molecular-targeted treatments, will be essential to improving head and neck squamous cell carcinoma (HNSCC) patient outcomes. In this sense, the sensitization of resistant cells and cancer stem cells (CSCs) represents a major challenge in cancer therapy. We conducted a proteomic study involving cisplatin-resistance and CSCs with the aim to unravel the molecular and cellular mechanisms by which tumor cells acquire resistance to chemotherapy. Syntenin-1 (SDCBP) was identified as an important protein involved in the chemoresistance and stemness of HNSCC tumors.

Abstract

To characterize the mechanisms that govern chemoresistance, we performed a comparative proteomic study analyzing head and neck squamous cell carcinoma (HNSCC) cells: CCL-138 (parental), CCL-138-R (cisplatin-resistant), and cancer stem cells (CSCs). Syntenin-1 (SDCBP) was upregulated in CCL-138-R cells and CSCs over parental cells. SDCBP depletion sensitized biopsy-derived and established HNSCC cell lines to cisplatin (CDDP) and reduced CSC markers, Src activation being the main SDCBP downstream target. In mice, SDCBP-depleted cells formed tumors with decreased mitosis, Ki-67 positivity, and metastasis over controls. Moreover, the fusocellular pattern of CCL-138-R cell-derived tumors reverted to a more epithelial morphology upon SDCBP silencing. Importantly, SDCBP expression was associated with Src activation, poor differentiated tumor grade, advanced tumor stage, and shorter survival rates in a series of 382 HNSCC patients. Our results reveal that SDCBP might be a promising therapeutic target for effectively eliminating CSCs and CDDP resistance.

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

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

Cancer stem cell characteristics and their potential as therapeutic targets

Cancer stem cells (CSCs) are a tumour subpopulation whose capacity for self-renewal, differentiation and proliferation generates unfavourable patient outcomes, including therapeutic resistance and metastasis. Much research has focused on the generation, biomarkers and therapeutic resistance of CSCs, as well as the development of CSC-targeted therapies. Reviews to date have either addressed general CSC characteristics or focused on CSCs from a well-studied cancer. Increasingly, specific treatment plans based on identification of molecular features and biomarkers of a patient's cancer, rather than classification according to tissue origin or bulk tumour properties, are leading to better patient outcomes. Here, we compare CSC characteristics, specifically their biomarkers and molecular features, and identify those that are common to a number of cancers. Identification of CSC markers that suggest therapeutic strategies has led to several successful in vitro and animal tests, recommending clinical trials of treatments with potentially enhanced therapeutic benefits, especially for recurring cancers.

Fenretinide, Tocilizumab, and Reparixin Provide Multifaceted Disruption of Oral Squamous Cell Carcinoma Stem Cell Properties: Implications for Tertiary Chemoprevention

Locoregional recurrence of oral squamous cell carcinoma (OSCC) dramatically reduces patient survival. Further, as many OSCC recurrences are inoperable, radiotherapy and chemotherapy with or without biological adjuncts are the remaining treatment options. Although the tumors may initially respond, radiotherapy- and chemotherapy-resistant cancer stem cells (CSC) can readily repopulate OSCC tumors. Currently, following the initial OSCC treatment, patients are closely monitored until a recurrence or a second primary is detected. Identification of agents with complementary mechanisms to suppress CSC tumorigenic functions could change this passive approach. The goals of this study were twofold: (1) develop and validate CSC-enriched (CSCE) OSCC cell lines and (2) identify chemopreventive agents that obstruct multiple CSCE protumorigenic pathways. CSCE cultures, which were created by paclitaxel treatment followed by three tumorsphere passes, demonstrated CSC characteristics, including increased expression of stem cell and inflammatory genes, increased aldehyde dehydrogenase (ALDH) activity, and enhanced in vitro/in vivo proliferation and invasion. Three chemopreventives, fenretinide, tocilizumab, and reparixin, were selected due to their distinct and complementary CSC-disruptive mechanisms. The CSCE selection process modulated the cells' intermediate filaments resulting in an epithelial-predominant (enhanced cytokeratin, proliferation, IL6 release) line and a mesenchymal-predominant (upregulated vimentin, invasive, IL8 release) line. Our results confirm that 4HPR binds with appreciably higher affinity than Wnt at the Frizzled binding site and significantly inhibits CSC-enabling Wnt-β-catenin downstream signaling. Notably, combination fenretinide-tocilizumab-reparixin treatment significantly suppressed IL6 and IL8 release, stem cell gene expression, and invasion in these diverse CSCE populations. These promising multiagent in vitro data provide the basis for our upcoming in vivo CSCE tertiary chemoprevention studies.

Cancer Stem Cells in Head and Neck Carcinomas: Identification and Possible Therapeutic Implications

The recurrence and/or lack of response of certain tumors to radio- and chemotherapy has been attributed to a small subpopulation of cells termed cancer stem cells (CSCs). CSCs have been identified in many tumors (including solid and hematological tumors). CSCs are characterized by their capacity for self-renewal, their ability to introduce heterogeneity within a tumor mass and its metastases, genomic instability, and their insensitivity to both radiation and chemotherapy. The latter highlights the clinical importance of studying this subpopulation since their resistance to traditional treatments may lead to metastatic disease and/or tumor relapse. Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common malignancy worldwide with the highest incidence occurring in East Asia and eastern and southern Africa. Several cellular subpopulations believed to have CSC properties have been isolated from HNSCCs, but at present, identification and characterization of CSCs remains an experimental challenge with no established or standardized protocols in place to confirm their identity. In this review we discuss current approaches to the study of CSCs with a focus on HNSCCs, particularly in the context of what this might mean from a therapeutic perspective.

Relationship between CD44high/CD133high/CD117high cancer stem cells phenotype and Cetuximab and Paclitaxel treatment response in head and neck cancer cell lines

Recent evidence suggests that cancer stem cells (CSCs), a small population of cancer cells that are highly tumourigenic, capable of self-renewal and have the ability to differentiate into cells that constitute the tumor, are the "drivers" of local recurrence and metastatic spread and may be associated with resistant to conventional therapy. The objectives of the study are to identify and characterize two head and neck cancer cell lines with regard CD44high/CD133high/CD117high profile (CSCs) and CD44low/CD133low/CD117low profile (Non-CSCs); to investigate the influence of chemotherapy treatment in CSCs and compare with Non-CSCs; to evaluate CD44 and EGFR gene expression in CSCs. Fluorescent-activated cell sorting (FACS) using specific cell surface marker combination (CD44, CD117 and CD133) was performed to isolate CSCs of Non-CSCs from cell lines. The Wound Healing assay was performed to confirm the presence of CSCs. After, the CSCs subpopulation and Non-CSCs were cultured and exposed for 24 h to Cetuximab and Paclitaxel treatment, separately. Cell proliferation was determined by MTS assay. CD44 and EGFR gene expression was quantified by quantitative real time PCR (qPCR) using TaqMan® Assay in both subpopulations. CSCs subpopulation untreated were considered as relative expression control. We firstly characterized CSCs in HN13 and HEP-2 cell lines with CD44, CD133 and CD117 biomarkers. We treated CSCs and Non-CSCs subpopulations with Cetuximab and Paclitaxel treatment and found that CSCs subpopulations demonstrated more resistance to Paclitaxel chemoterapy, when compared with Non-CSCs subpopulations of oral cancer cell line. These CSCs subpopulations presented up-regulation of CD44 gene and down-regulation of EGFR gene in oral cancer cell line, and down-regulation of CD44 gene and up-regulation of EGFR gene in laryngeal cancer cell line when compared with Non-CSCs subpopulations. We conclude that the combination of CD44, CD133 and CD117 biomarkers have stem cell properties in both cell lines. CSCs has ability to resist to Paclitaxel treatment in oral cancer cell line. CSCs present high expression of CD44 gene and down expression of EGFR gene in oral cancer cell line. CSCs in laryngeal cell line present down expression of CD44 gene and high expression of EGFR gene when compared with cells without characteristics of cancer stem cells.

DSPP-MMP20 gene silencing downregulates cancer stem cell markers in human oral cancer cells

BACKGROUND

Recent findings indicate that dentin sialophosphoprotein (DSPP) and matrix metalloproteinase (MMP) 20 interact in oral squamous cell carcinoma (OSCC). The objective of this study was to determine the effects of DSPP/MMP20 gene silencing on oral cancer stem cell (OCSC) markers.

METHODS

The expression of well-established OCSC markers: ABCG2; ALDH1; CD133; CD44; BMI1; LGR4, and Podoplanin in DSPP/MMP20-silenced OSCC cell line, OSC2, and controls were assayed by western blot (WB), and flow cytometry techniques. The sensitivity of OSC2 cells to cisplatin following DSPP/MMP20 silencing was also determined.

RESULTS

DSPP/MMP20 silencing resulted in downregulation of OCSC markers, more profoundly ABCG2 (84%) and CD44 (81%), following double silencing. Furthermore, while treatment of parent (pre-silenced) OSC2 cells with cisplatin resulted in upregulation of OCSC markers, DSPP/MMP20-silenced OSC2 cells similarly treated resulted in profound downregulation of OCSC markers (72 to 94% at 50 μM of cisplatin), and a marked reduction in the proportion of ABCG2 and ALDH1 positive cells (~ 1%).

CONCLUSIONS

We conclude that the downregulation of OCSC markers may signal a reduction in OCSC population following MMP20/DSPP silencing in OSCC cells, while also increasing their sensitivity to cisplatin. Thus, our findings suggest a potential role for DSPP and MMP20 in sustaining OCSC population in OSCCs, possibly, through mechanism(s) that alter OCSC sensitivity to treatment with chemotherapeutic agents such as cisplatin.

Acid sphingomyelinase activity as an indicator of the cell stress in HPV-positive and HPV-negative head and neck squamous cell carcinoma

Human papillomavirus (HPV) infection, especially HPV-16 and HPV-18, has been increasingly associated with head and neck squamous cell carcinoma. The treatment of HPV-positive squamous cell carcinoma has a better response to both radiotherapy and chemotherapy and presents a better prognosis for the patient. Defining the underlying mechanism of the difference might help in developing future treatment options and could be an important factor in personal therapy planning. Endogenously secreted acid sphingomyelinase (ASMase) levels in the cellular stress caused by irradiation and cisplatin were investigated. MTT assay was performed to evaluate the viability of the treated cells. Keratinocytes were used to evaluate the effects of radiation on normal tissues. Irradiation caused a dose-dependent increase in ASMase activity in both SCC9 HPV-negative, and UDSCC2 HPV-positive cells. ASMase activity in UDSCC2 cells was significantly higher than that in SCC9 cells. UDSCC cells were more sensitive to cisplatin treatment than SCC cells, and the dose-response in the activity was observed in long-time treatments when high doses of cisplatin were used. The results of the current study have clearly showed that HPV positivity should be considered as one of the determinative factors which should be considered when tumor treatments are planned. However, further studies are needed to determine the differences in cellular responses and pathways among HPV-negative and HPV-positive cells.

Targeted molecular ablation of cancer stem cells for curing gastrointestinal cancers

Abundance of the ATPase-binding cassette (ABC) transporters and deranged self-renewal pathways characterize the presence of cancer stem cells (CSCs) in gastrointestinal cancers (GI cancers), which play crucial roles in tumorigenesis, chemotherapy resistance, tumor recurrence, and cancer metastasis. Therefore, in order to ensure high cure rates, chemoquiescence, CSCs should be ablated. Recent advances in either understanding CSCs or biomarker identification enable scientists to develop techniques for ablating CSCs and clinicians to provide cancer cure, especially in GI cancers characterized by inflammation-driven carcinogenesis. Areas covered: A novel approach to ablate CSCs in GI cancers, including esophageal, gastric, and colon cancers, is introduced along with explored underlying molecular mechanisms. Expert commentary: Though CSC ablation is still in the empirical stages and not in clinical practice, several strategies for ablating CSCs in GI cancers had been published, proton-pump inhibitors (PPIs) that regulate the membrane-bound ABC transporters, which underlie drug resistance; chloroquine (CQ) that inhibits autophagy, which is responsible for tumor survival; Hedgehog/Wnt/Notch inhibitors that influence the underlying stem-cell growth, and some natural products including Korean red ginseng, cancer-preventive kimchi, Artemisia extract, EGCG from green tea, and walnut extracts.

Interferon-α Promotes the Expression of Cancer Stem Cell Markers in Oral Squamous Cell Carcinoma

Objectives: IFNα can stimulate an antitumor immune response and has a direct inhibition on cancer cells. This study is to test whether IFNα can activate dormant cancer stem cell (CSC) in oral squamous cell carcinoma (OSCC) to facilitate their elimination by chemotherapy. Materials and methods: Nude mouse transplantation tumor model was established and administrated with IFNα and saline. The influence on CD44 and ALDH1A1 expression under IFNα treatment was detected by in vivo experiments. Flow cytometry, western blot, and immunofluorescence were used to detect the expression of CD44 and ALDH1A1 after INFa treatment in OSCC cell lines. Tumorsphere formation assay was conducted under incubation with IFNα for 2 weeks. Chromatin immunoprecipitation (ChIP) assays was used to examine the IFNα-induced transcriptional regulation of CD44 and ALDH1A1 expression. That IFNα-primed enhanced killing effect of chemotherapy was evaluated by MTT and western blot. Results: IFNα transcriptionally activated the expression of CD44 and ALDH1A1 expression both in vivo and in vitro. IFNα-primed enhanced the cytotoxic inhibition effect of CDDP, erlotinib and nimotuzumab on OSCC cells. Conclusion: These results suggest that IFNα could be administrated to patients prior to chemotherapeutic drugs, which will facilitate the killing of cancer stem cells in OSCC.

Omics-based molecular techniques in oral pathology centred cancer: prospect and challenges in Africa

BACKGROUND

The completion of the human genome project and the accomplished milestones in the human proteome project; as well as the progress made so far in computational bioinformatics and "big data" processing have contributed immensely to individualized/personalized medicine in the developed world.

MAIN BODY

At the dawn of precision medicine, various omics-based therapies and bioengineering can now be applied accurately for the diagnosis, prognosis, treatment, and risk stratification of cancer in a manner that was hitherto not thought possible. The widespread introduction of genomics and other omics-based approaches into the postgraduate training curriculum of diverse medical and dental specialties, including pathology has improved the proficiency of practitioners in the use of novel molecular signatures in patient management. In addition, intricate details about disease disparity among different human populations are beginning to emerge. This would facilitate the use of tailor-made novel theranostic methods based on emerging molecular evidences.

CONCLUSION

In this review, we examined the challenges and prospects of using currently available omics-based technologies vis-à-vis oral pathology as well as prompt cancer diagnosis and treatment in a resource limited setting.

Ectopic overexpression of CD133 in HNSCC makes it resistant to commonly used chemotherapeutics

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers in the world. Resistance to cytotoxic chemotherapy is a major cause of mortality in patients with HNSCC. A small subset of cancer cells called cancer stem cells (CSCs) may be key contributors to drug resistance and tumor recurrence in HNSCC. The aim of this study was to determine whether CD133, which maintains properties of CSCs, promotes chemoresistance by arresting cell cycle transition and reducing apoptosis in HNSCC cells. CD133 overexpression was examined in KB cells, and colony forming and aldehyde dehydrogenase activity assays were performed. To investigate the role of CD133 in chemoresistance, cell death was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Diff-Quick, flow cytometry, and western blot of apoptosis-related protein expression in fluorouracil (5-FU)- or cisplatin-treated cells. In addition, microarray and related protein expression assessments were performed to investigate the mechanism of chemoresistance against 5-FU and cisplatin in KB cells. Moreover, chemoresistance against 5-FU or cisplatin in a KB-inoculated mouse model was analyzed by hematoxylin and eosin staining, immunohistochemical study of CD133, and immunofluorescence of tumor tissue. In this study, we demonstrate that ectopic overexpression of CD133 significantly promotes properties of stemness in KB cell lines. Furthermore, CD133 promotes chemoresistance by arresting transition of the cell cycle and reducing apoptosis, which results in inhibition of tumor growth in 5-FU- or cisplatin-injected mouse tumor model. Taken together, our findings show that elevated levels of CD133 lead to HNSCC chemoresistance through increased stemness and cell cycle arrest.

Targeting stem cells by radiation: From the biological angle to clinical aspects

Radiotherapy is a cornerstone of anticancer treatment. However in spite of technical evolutions, important rates of failure and of toxicity are still reported. Although numerous pre-clinical data have been published, we address the subject of radiotherapy-stem cells interaction from the clinical efficacy and toxicity perspective. On one side, cancer stem cells (CSCs) have been recently evidenced in most of solid tumor primary locations and are thought to drive radio-resistance phenomena. It is particularly suggested in glioblastoma, where CSCs were showed to be housed in the subventricular zone (SVZ). In recent retrospective studies, the radiation dose to SVZ was identified as an independent factor significantly influencing overall survival. On the other side, healthy tissue stem cells radio-destruction has been recently suggested to cause two of the most quality of life-impacting side effects of radiotherapy, namely memory disorders after brain radiotherapy, and xerostomia after head and neck radiotherapy. Recent publications studying the impact of a radiation dose decrease on healthy brain and salivary stem cells niches suggested significantly reduced long term toxicities. Stem cells comprehension should be a high priority for radiation oncologists, as this particular cell population seems able to widely modulate the efficacy/toxicity ratio of radiotherapy in real life patients.