Cancer stem cells: mediators of tumorigenesis and metastasis in head and neck squamous cell carcinoma

Metformin overcomes chemoresistance by regulating stemness via KLF4 in oral squamous cell carcinoma

OBJECTIVE

Chemoresistance is a common event after chemotherapy, including oral squamous cell carcinoma (OSCC). Accumulated evidence suggests that the cancer stemness significantly contributes to therapy resistance. An unresolved question remains regarding how to effectively overcome OSCC chemoresistance by targeting stemness. This study aims to investigate the antitumor effect of metformin and clarify the potential molecular mechanisms.

METHODS

Cellular models resistant to chemotherapy were established, and their viability and sphere-forming ability were assessed using CCK-8 and soft agar formation assays, respectively. RNA-seq and Western blotting analyses were employed to delve into the molecular pathways. Furthermore, to corroborate the inhibitory effects of metformin and cisplatin at an animal level, a subcutaneous tumor transplantation model was instituted.

RESULTS

Metformin as a monotherapy exhibited inhibition of stemness traits via Krüppel-like factor 4 (KLF4). Metformin and cisplatin can synergically inhibit cell proliferation and induce cell apoptosis. Animal experiments confirmed the inhibitory effect of cisplatin and metformin on tumor in mice.

CONCLUSION

Our study proposes a potential therapeutic approach of combining chemotherapy with metformin to overcome chemoresistance in OSCC.

Cancer Stem Cells from Definition to Detection and Targeted Drugs

Cancers remain the second leading cause of mortality in the world. Preclinical and clinical studies point an important role of cancer/leukaemia stem cells (CSCs/LSCs) in the colonisation at secondary organ sites upon metastatic spreading, although the precise mechanisms for specific actions are still not fully understood. Reviewing the present knowledge on the crucial role of CSCs/LSCs, their plasticity, and population heterogeneity in treatment failures in cancer patients is timely. Standard chemotherapy, which acts mainly on rapidly dividing cells, is unable to adequately affect CSCs with a low proliferation rate. One of the proposed mechanisms of CSC resistance to anticancer agents is the fact that these cells can easily shift between different phases of the cell cycle in response to typical cell stimuli induced by anticancer drugs. In this work, we reviewed the recent studies on CSC/LSC alterations associated with disease recurrence, and we systematised the functional assays, markers, and novel methods for CSCs screening. This review emphasises CSCs' involvement in cancer progression and metastasis, as well as CSC/LSC targeting by synthetic and natural compounds aiming at their elimination or modulation of stemness properties.

Possible role of ALDH1 and CD44 in lip carcinogenesis

BACKGROUND

Lip squamous cell carcinoma (LSCC) accounts for 12% of all head and neck cancers. It is caused by chronic exposure to ultraviolet light solar radiation and related to previous actinic cheilitis (AC). This study aimed to investigate the immunostaining of the putative cancer stem cells (CSC) markers ALDH1 and CD44 in AC (n=30) and LSCC (n=20). ALDH1 positivity was found to be statistically higher in LSCC than in AC lesions (p=0.0045), whilst CD44 expression was statistically higher in AC than in LSCC lesions (p=0.0155). ALDH1+ cells in AC lesions were associated with specific clinical features: a younger age (<60 years old), the female gender, white skin, not smoking or consuming alcohol, and a fast evolution, and not associated with the chronic exposure to UV radiation (p<0.0001). CD44 positivity was associated with patients who were male, feoderm, smoked, consumed alcohol, underwent occupational exposure to UV-radiation, and demonstrated lesions with log-time evolution (p<0.0001). ALDH1 + cells were associated with mild dysplasia using a system from the World Health Organization (WHO), and with a low risk of malignant transformation, according to the binary system (p<0.0001). CD44+ cells were also associated with moderated dysplasia, according to the WHO system. In LSCC, ALDH1 + cells were positively associated with patients who were older (≥ 60 years old), smokers, and with those who consumed alcohol (p<0.0001). CD44 + cells in LSCC were associated with older (≥ 60 years old) patients as well, but also with female patients, white skin, non-smokers, and individuals who did not consume alcohol (p<0.0001), all of whom showed distinct patterns in pre- and malignant lesions of both markers. Additionally, in LSCC, both ALDH1 and CD44 staining were associated with smaller tumor sizes (T1/T2; p<0.0001). In summary, although both ALDH1 and CD44 were associated with the presence of dysplasia in AC lesions, the present findings suggest that ALDH1 and CD44 may be activated by different etiopathogenic pathways, predominantly in distinct steps of oral carcinogenesis. CD44 would thus be more significantly related to the potentially malignant lesion, while ALDH1 would be closely linked to malignancy.

CSRP2 promotes cell stemness in head and neck squamous cell carcinoma

BACKGROUND

Cysteine-rich protein 2 (CSRP2) is discovered as oncogene. The study aims to investigate the clinical significance and potential mechanism of CSRP2 in head and neck squamous cell carcinoma (HNSCC).

METHODS

CSRP2 expression was explored by immunohistochemistry tissue microarrays and Western blotting in HNSCC. The effect of CSRP2 on the cancer stemness and epithelial-to-mesenchymal transition (EMT) of HNSCC cells was investigated by sphere formation, wound healing, and transwell assays. The vitro and vivo experiments revealed that CSRP2 modulated cancer stemness and EMT phenotypes in HNSCC.

RESULTS

CSRP2 was overexpressed in HNSCC patients and presented poor prognosis. CSRP2 knockdown inhibited the migration and invasion ability of the HNSCC cells. And CSRP2 expression was closely associated with CSCs markers, EMT-transcription factor, new oncoprotein, and immune checkpoint.

CONCLUSION

The overexpression of CSRP2 indicates poor prognosis and plays a key role in maintaining the cancer cell stemness and EMT.

Therapeutic inhibition of Bmi-1 ablates chemoresistant cancer stem cells in adenoid cystic carcinoma

OBJECTIVES

Adenoid Cystic Carcinomas (ACC) typically show modest responseto cytotoxic therapy. Cancer stem cells (CSC) have been implicated in chemoresistance and tumor relapse. However, their role in ACC remains unknown. The purpose of this work was to evaluate the impact of targeting ACC CSCs with Bmi-1 inhibitors on resistance to cytotoxic therapy and tumor relapse.

MATERIALS AND METHODS

Therapeutic efficacy of a small molecule inhibitor of Bmi-1 (PTC596; Unesbulin) and/or Cisplatin on ACC stemness was evaluated in immunodeficient mice harboring PDX ACC tumors (UM-PDX-HACC-5) and in human ACC cell-lines (UM-HACC-2A,-14) or low passage primary human ACC cells (UM-HACC-6). The effect of therapy on stemness was examined by salisphere assays, flow cytometry for ALDH activity and CD44 expression, and Western blots for Bmi-1 (self-renewal marker) and Oct4 (embryonic stem cell marker) expression.

RESULTS

Platinum-based agents (Cisplatin, Carboplatin) induced Bmi-1 and Oct4 expression, increased salisphere formation and the CSC fraction in vitro and in vivo. In contrast, PTC596 inhibited expression of Bmi-1, Oct4 and pro-survival proteins Mcl-1 and Claspin; decreased the number of salispheres, and the fraction of ACC CSCs in vitro. Silencing Claspin decreased salisphere formation and CSC fraction. Both, single agent PTC596 and PTC596/Cisplatin combination decreased the CSC fraction in PDX ACC tumors. Notably, short-term combination therapy (2 weeks) with PTC596/Cisplatin prevented tumor relapse for 150 days in a preclinical trial in mice.

CONCLUSION

Therapeutic inhibition of Bmi-1 ablates chemoresistant CSCs and prevents ACC tumor relapse. Collectively, these results suggest that ACC patients might benefit from Bmi-1-targeted therapies.

The Role of IL-6 in Cancer Cell Invasiveness and Metastasis-Overview and Therapeutic Opportunities

Interleukin 6 (IL-6) belongs to a broad class of cytokines involved in the regulation of various homeostatic and pathological processes. These activities range from regulating embryonic development, wound healing and ageing, inflammation, and immunity, including COVID-19. In this review, we summarise the role of IL-6 signalling pathways in cancer biology, with particular emphasis on cancer cell invasiveness and metastasis formation. Targeting principal components of IL-6 signalling (e.g., IL-6Rs, gp130, STAT3, NF-κB) is an intensively studied approach in preclinical cancer research. It is of significant translational potential; numerous studies strongly imply the remarkable potential of IL-6 signalling inhibitors, especially in metastasis suppression.

From Tissue Physoxia to Cancer Hypoxia, Cost-Effective Methods to Study Tissue-Specific O2 Levels in Cellular Biology

The human body is endowed with an extraordinary ability to maintain different oxygen levels in various tissues and organs. The maintenance of physiological levels of oxygen is known as physoxia. The development of hypoxic conditions plays an important role in the biology of several pathologies, including cancer. In vitro studies using normal and neoplastic cells require that culture conditions be carried out under appropriate oxygen levels, either physoxic or hypoxic conditions. Such requirements are difficult to widely implement in laboratory practice, mainly due to the high costs of specialized equipment. In this work, we present and characterize a cost-effective method to culture cells under a range of oxygen levels using deoxidizing pouches. Our results show that physoxic and hypoxic levels using deoxidizing absorbers can be achieved either by implementing a gradual change in oxygen levels or by a regimen of acute depletion of oxygen. This approach triggers the activation of an epithelial-mesenchymal transition in cancer cells while stimulating the expression of HIF-1α. Culturing cancer cells with deoxidizing agent pouches revealed PI3K oncogenic pathway exacerbations compared to tumor cells growing under atmospheric levels of oxygen. Similar to the PI3K signaling disturbance, we also observed augmented oxidative stress and superoxide levels and increased cell cycle arrest. Most interestingly, the culture of cancer cells under hypoxia resulted in the accumulation of cancer stem cells in a time-dependent manner. Overall, we present an attractive, cost-effective method of culturing cells under appropriate physoxic or hypoxic conditions that is easily implementable in any wet laboratory equipped with cell culture tools.

Advancement in Cancer Stem Cell Biology and Precision Medicine-Review Article Head and Neck Cancer Stem Cell Plasticity and the Tumor Microenvironment

Head and Neck cancer survival has continued to remain around 50% despite treatment advances. It is thought that cancer stem cells play a key role in promoting tumor heterogeneity, treatment resistance, metastasis, and recurrence in solid malignancies including head and neck cancer. Initial studies identified cancer stem cell markers including CD44 and ALDH in head and neck malignancies and found that these cells show aggressive features in both in vitro and in vivo studies. Recent evidence has now revealed a key role of the tumor microenvironment in maintaining a cancer stem cell niche and promoting cancer stem cell plasticity. There is an increasing focus on identifying and targeting the crosstalk between cancer stem cells and surrounding cells within the tumor microenvironment (TME) as new therapeutic potential, however understanding how CSC maintain a stem-like state is critical to understanding how to therapeutically alter their function. Here we review the current evidence for cancer stem cell plasticity and discuss how interactions with the TME promote the cancer stem cell niche, increase tumor heterogeneity, and play a role in treatment resistance.

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.

The IL-6R and Bmi-1 axis controls self-renewal and chemoresistance of head and neck cancer stem cells

Despite major progress in elucidating the pathobiology of head and neck squamous cell carcinoma (HNSCC), the high frequency of disease relapse correlates with unacceptably deficient patient survival. We previously showed that cancer stem-like cells (CSCs) drive tumorigenesis and progression of HNSCC. Although CSCs constitute only 2–5% of total tumor cells, CSCs contribute to tumor progression by virtue of their high tumorigenic potential and their resistance to chemo-, radio-, and immunotherapy. Not only are CSCs resistant to therapy, but cytotoxic agents actually enhance cancer stemness by activating transcription of pluripotency factors and by inducing expression of Bmi-1, a master regulator of stem cell self-renewal. We hypothesized therapeutic inhibition of interleukin-6 receptor (IL-6R) suppresses Bmi-1 to overcome intrinsic chemoresistance of CSCs. We observed that high Bmi-1 expression correlates with decreased (p = 0.04) recurrence-free survival time in HNSCC patients (n = 216). Blockade of IL-6R by lentiviral knockdown or pharmacologic inhibition with a humanized monoclonal antibody (Tocilizumab) is sufficient to inhibit Bmi-1 expression, secondary sphere formation, and to decrease the CSC fraction even in Cisplatin-resistant HNSCC cells. IL-6R inhibition with Tocilizumab abrogates Cisplatin-mediated increase in CSC fraction and induction of Bmi-1 in patient-derived xenograft (PDX) models of HNSCC. Notably, Tocilizumab inhibits Bmi-1 and suppresses growth of xenograft tumors generated with Cisplatin-resistant HNSCC cells. Altogether, these studies demonstrate that therapeutic blockade of IL-6R suppresses Bmi-1 function and inhibits cancer stemness. These results suggest therapeutic inhibition of IL-6R might be a viable strategy to overcome the CSC-mediated chemoresistance typically observed in HNSCC patients.

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.

Understanding the complex pathogenesis of oral cancer: A comprehensive review

The pathogenesis of oral cancer is a complex and multifactorial process that requires a deep understanding of the underlying mechanisms involved in the development and progress of malignancy. The ever-improving comprehension of the diverse molecular characteristics of cancer, the genetic and epigenetic alterations of tumor cells, and the complex signaling pathways that are activated and frequently cross talk open up promising horizons for the discovery and application of diagnostic molecular markers and set the basis for an era of individualized management of the molecular defects underlying and governing oral premalignancy and cancer. The purpose of this article is to review the key molecular concepts that are implicated in oral carcinogenesis, especially focusing on oral squamous cell carcinoma, and to review selected biomarkers that play a substantial role in controlling the so-called "hallmarks of cancer," with special reference to recent advances that shed light on their deregulation during the different steps of oral cancer development and progression.

Spelling Out CICs: A Multi-Organ Examination of the Contributions of Cancer Initiating Cells' Role in Tumor Progression

Tumor invasion and metastasis remain the leading causes of mortality for patients with cancer despite current treatment strategies. In some cancer types, recurrence is considered inevitable due to the lack of effective anti-metastatic therapies. Recent studies across many cancer types demonstrate a close relationship between cancer-initiating cells (CICs) and metastasis, as well as general cancer progression. First, this review describes CICs' contribution to cancer progression. Then we discuss our recent understanding of mechanisms through which CICs promote tumor invasion and metastasis by examining the role of CICs in each stage. Finally, we examine the current understanding of CICs' contribution to therapeutic resistance and recent developments in CIC-targeting drugs. We believe this understanding is key to advancing anti-CIC clinical therapeutics.

Immune deserts in head and neck squamous cell carcinoma: A review of challenges and opportunities for modulating the tumor immune microenvironment

Immunotherapy revolutionized cancer treatment but has yet to elicit durable responses in the majority of patients with head and neck squamous cell carcinoma (HNSCC). HNSCC is generally characterized by a high tumor mutational burden, which has translated to a large neoantigen load that could prime the immune system to recognize and eliminate malignant cells. Studies are increasingly showing, however, that HNSCC is an "immune desert" tumor that can hijack multiple parts of the tumor immunity cycle in order to evade immune recognition and suppress immune system activation. Herein we will review how HNSCC tumors modulate their architecture, cellular composition, and cytokine milieu to maximize immunosuppression; as well as relevant therapeutic opportunities and emerging issues facing the field of HNSCC immuno-oncology.

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

Cancer stem cells enrichment with surface markers CD271 and CD44 in human head and neck squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) has a poor 5-year survival rate of 50%. One potential reason for treatment failure is the presence of cancer stem cells (CSCs). Several cell markers, particularly CD44, have been used to isolate CSCs. However, isolating a pure population of CSC in HNSCC still remains a challenging task. Recent findings show that normal oral stem cells were isolated using CD271 as a marker. Thus, we investigated the combined use of CD271 and CD44 to isolate an enriched subpopulation of CSCs, followed by their characterization in vitro, in vivo, and in patients' tissue samples. Fluorescent-activated cell sorting was used to isolate CD44+/CD271+ and CD44+/CD271- from two human HNSCC cell lines. Cell growth and self-renewal were measured with MTT and sphere/colony formation assays. Treatment-resistance was tested against chemotherapy (cisplatin and 5-fluorouracil) and ionizing radiation. Self-renewal, resistance, and stemness-related genes expression were measured with qRT-PCR. In vivo tumorigenicity was tested with an orthotopic immunodeficient mouse model of oral cancer. Finally, we examined the co-localization of CD44+/CD271+ in patients' tissue samples. We found that CD271+ cells were a subpopulation of CD44+ cells in human HNSCC cell lines and tissues. CD44+/CD271+ cells exhibited higher cell proliferation, sphere/colony formation, chemo- and radio-resistance, upregulation of CSCs-related genes, and in vivo tumorigenicity when compared to CD44+/CD271- or the parental cell line. These cell markers showed increased expression in patients with the increase of the tumor stage. In conclusion, using both CD44 and CD271 allowed the isolation of CSCs from HNSCC. These enriched CSCs will be more relevant in future treatment and HNSCC progression studies.

mTOR Inhibition Ablates Cisplatin-Resistant Salivary Gland Cancer Stem Cells

Patients with advanced salivary gland mucoepidermoid carcinoma (MEC) are treated with surgery and radiotherapy, as current systemic therapies are largely ineffective. As such, current treatment frequently leads to poor long-term survival due to locoregional recurrence or metastases. We have shown that salivary gland cancer stem cells (CSCs) are resistant to platinum-based chemotherapy and drive tumor progression. The purpose of this study was to investigate the effect of therapeutic inhibition of mTOR (mechanistic target of rapamycin) on resistance of CSCs to cisplatin, a prototypic platinum-based chemotherapeutic agent. Viability assays determined the effect of several inhibitors of PI3k/mTOR signaling (e.g., temsirolimus, BKM120, AZD8055, PF4708671) and/or cisplatin on survival of human MEC cells. The impact of mTOR inhibitors and/or cisplatin on MEC stemness was examined with salisphere assays, flow cytometry for ALDH/CD44 (CSC markers for MEC), and Western blots for Bmi-1 expression (marker of stem cell self-renewal). Salivary gland MEC patient-derived xenografts were used to examine the effect of cisplatin and/or temsirolimus on CSCs in vivo. We observed that cisplatin induced mTOR and S6K1 phosphorylation, increased the number and size of MEC salispheres, and induced Bmi-1 expression and the fraction of CSCs in MEC models in vitro. Cisplatin also increased the fraction of CSCs in vivo. In contrast, mTOR inhibition (e.g., temsirolimus) blocked cisplatin-induced Bmi-1 expression and salisphere formation in vitro. Remarkably, temsirolimus slowed down tumor growth and decreased the fraction of CSCs (P < 0.05) even in presence of cisplatin in a short-term in vivo experiment. Collectively, these results demonstrate that therapeutic inhibition of mTOR ablates cytotoxic-resistant CSCs, and they suggest that a combination of an mTOR inhibitor and platinum-based chemotherapy might be beneficial to patients with salivary gland mucoepidermoid carcinoma.

Combined treatment with acetazolamide and cisplatin enhances the chemosensitivity of human head and neck squamous cell carcinoma TU868 cells

AIMS

To investigate whether combination of acetazolamide and cisplatin can enhance the chemosensitivity of human head and neck squamous cell carcinoma (HNSCC) cell line TU868.

METHODS

MTT assay was performed to determine the effect of acetazolamide, cisplatin and their combination on the proliferation of TU868 cells. Then the effect of these 2 drugs on the expression of proliferation-related and apoptosis-related proteins was detected by Western blot. Moreover, the effect of acetazolamide and cisplatin on the expression of aquaporin-1 was detected by RT-qPCR. Loss-of-function assays was performed to assess whether the effect of acetazolamide and cisplatin on TU868 cells was mediated by aquaporin-1. The effect of acetazolamide and cisplatin on tumor cell growth was confirmed in mice by testing the tumor growth size.

RESULTS

Acetazolamide and cisplatin treatment displayed synergistic effects on the inhibition of TU868 cell growth compared with the drugs used alone. Moreover, the acetazolamide/cisplatin combination could decrease the level of PCNA but increase the level of p53; decrease the ratio of Bcl-2/Bax and increase the expression of caspase-3 compared with the single drug treated group. Moreover, we found that the combination also significantly inhibits aquaporin-1 expression. Loss-of-function assays suggested that the anti-tumor effect of these 2 drugs was achieved via affecting aquaporin-1. Consistent with the in vitro assays, combined treatment with acetazolamide and cisplatin significantly inhibits the tumor growth in mice compared with the single drug treated group.

CONCLUSION

These results demonstrated that combined treatment with acetazolamide and cisplatin could synergistically inhibit the malignant development of HNSCC cells.

Advances in Therapeutic Targeting of Cancer Stem Cells within the Tumor Microenvironment: An Updated Review

Despite great strides being achieved in improving cancer patients' outcomes through better therapies and combinatorial treatment, several hurdles still remain due to therapy resistance, cancer recurrence and metastasis. Drug resistance culminating in relapse continues to be associated with fatal disease. The cancer stem cell theory posits that tumors are driven by specialized cancer cells called cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells known to be resistant to therapy and cause metastasis. Whilst the debate on whether CSCs are the origins of the primary tumor rages on, CSCs have been further characterized in many cancers with data illustrating that CSCs display great abilities to self-renew, resist therapies due to enhanced epithelial to mesenchymal (EMT) properties, enhanced expression of ATP-binding cassette (ABC) membrane transporters, activation of several survival signaling pathways and increased immune evasion as well as DNA repair mechanisms. CSCs also display great heterogeneity with the consequential lack of specific CSC markers presenting a great challenge to their targeting. In this updated review we revisit CSCs within the tumor microenvironment (TME) and present novel treatment strategies targeting CSCs. These promising strategies include targeting CSCs-specific properties using small molecule inhibitors, immunotherapy, microRNA mediated inhibitors, epigenetic methods as well as targeting CSC niche-microenvironmental factors and differentiation. Lastly, we present recent clinical trials undertaken to try to turn the tide against cancer by targeting CSC-associated drug resistance and metastasis.

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.

LIN28: A cancer stem cell promoter for immunotherapy in head and neck squamous cell carcinoma

Lin28, a highly conserved RNA-binding protein, plays an important role in differentiation, metabolism, proliferation, pluripotency, and tumourigenicity. Lin28 overexpression promotes tumour-cell proliferation and metastasis in various human cancers, including head and neck cancer. Multiple studies demonstrate that Lin28 critically contributes to anti-tumour immunity and production of cancer stem cells in head and neck squamous cell carcinoma (HNSCC). Thus, Lin28 has potential application in HNSCC treatment.

Cancer Stem Cells and Targeting Strategies

Chemoresistance is a major problem in cancer therapy as cancer cells develop mechanisms that counteract the effect of chemotherapeutic compounds, leading to relapse and the development of more aggressive cancers that contribute to poor prognosis and survival rates of treated patients. Cancer stem cells (CSCs) play a key role in this event. Apart from their slow proliferative property, CSCs have developed a range of cellular processes that involve drug efflux, drug enzymatic inactivation and other mechanisms. In addition, the microenvironment where CSCs evolve (CSC niche), effectively contributes to their role in cancer initiation, progression and chemoresistance. In the CSC niche, immune cells, mesenchymal stem cells (MSCs), endothelial cells and cancer associated fibroblasts (CAFs) contribute to the maintenance of CSC malignancy via the secretion of factors that promote cancer progression and resistance to chemotherapy. Due to these factors that hinder successful cancer therapies, CSCs are a subject of intense research that aims at better understanding of CSC behaviour and at developing efficient targeting therapies. In this review, we provide an overview of cancer stem cells, their role in cancer initiation, progression and chemoresistance, and discuss the progress that has been made in the development of CSC targeted therapies.

Role of Telomeric TRF2 in Orosphere Formation and CSC Phenotype Maintenance Through Efficient DNA Repair Pathway and its Correlation with Recurrence in OSCC

The major problem to effective treatment of oral cancer is the presence of therapy resistance. Presence of cancer stem cell in the bulk of tumor have been implicated in therapeutic resistance. In this study, we report a non-telomeric role of TRF2 in formation of oral cancer spheroids and CSC phenotype maintenance via an efficient DNA damage repair mechanism in the presence of chemotherapeutic insult. We report reduced sphere formation efficiency and reduced spheroid size in TRF2 silenced oral cancer cell lines. TRF2 silenced orospheres further reported reduced proliferative capacity as compared to non-silenced orospheres. Furthermore, TRF2 silencing hampered the migratory potential of oral cancer cell line and also reduced the expression of several CSC markers like CD44, Oct4, Sox2, KLF4 and c-Myc along with β-catenin and hTERT molecules both in Cal27 cell line and generated orospheres. TRF2 silencing impaired efficient DNA damage repair capacity of non-orospheric and orospheric cells and repressed ERCC1 expression levels when treated with Cisplatin. TRF2 overexpression was also observed to correlate with poor overall survival and disease relapse of OSCC patients. In silico studies further identified several amino acid residues that show high binding affinity and strong protein-protein interactions among TRF2 and CSC marker KLF4. Hence, our report confirms a non-telomeric role of TRF2 in spheroid generation, maintenance of CSC phenotype and efficient DNA damage repair capacity contributing to chemotherapy resistance in oral cancer cell line. We further iterate the use of TRF2 as a prognostic marker in OSCC for faster detection and improved survival.

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.

Exposure to nicotine-derived nitrosamine ketone and arecoline synergistically facilitates tumor aggressiveness via overexpression of epidermal growth factor receptor and its downstream signaling in head and neck squamous cell carcinoma

Long-term nicotine-derived nitrosamine ketone (NNK) and arecoline exposure promotes carcinogenesis and head and neck squamous cell carcinoma (HNSCC) progression, although most associated data on the two were analyzed individually. The molecular mechanisms underlying tumor progression associated with the synergistic effects of NNK and arecoline remain unclear. We treated SCC-25 and FaDu cells with NNK and arecoline (separately or in combination) for 3 months. Comparative analysis was performed to investigate the mechanism underlying the acquisition of properties related to tumor promotion, including stemness, anti-apoptosis, and resistance to HNSCC therapeutics. Long-term exposure to NNK and arecoline resulted in an increase in cancer stem cell properties, anti-apoptosis, and the resistance to cisplatin in HNSCC. We detected abundant epidermal growth factor receptor (EGFR) expression in HNSCC cells after combined treatment with NNK and arecoline. EGFR was pivotal in inducing tumor promotion and anti-apoptosis in cancer cells by inducing pAKT and NFκB. Combined treatment with NNK and arecoline synergistically facilitated tumor aggressiveness via EGFR–AKT signaling. Targeting EGFR–AKT signaling may be a feasible strategy for treating HNSCC.

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.

CD271 Confers an Invasive and Metastatic Phenotype of Head and Neck Squamous Cell Carcinoma through the Upregulation of Slug

Purpose: Head and neck squamous cell carcinoma (HNSCC) is comprised of heterogeneous populations of cells, and CD271 (NGFR; p75NTR) has been associated with a tumor-initiating cell subpopulation. This study assessed the role of CD271 in modulating metastatic behavior in HNSCC.Experimental Design: CD271 was overexpressed in murine and human oral squamous cell carcinoma cells to assess the impact of CD271 activation on the invasive and metastatic phenotype of these cells, using in vitro and orthotopic in vivo modeling. Treatment with human nerve growth factor (NGF) to activate CD271, as well as shRNA knockdown of the CD271-upregulated Snai2 expression, was used to assess the mechanism of the CD271-induced invasive phenotype. Relevance of CD271 expression in human HNSCC was evaluated in patient-derived xenografts (PDX) and primary human oral cancers, annotated with clinical behavior characteristics and survival data.Results: Forced expression of CD271 resulted in a more invasive and metastatic phenotype. Slug, an epithelial-to-mesenchymal transition (EMT)-related transcription factor, encoded by Snai2, was highly expressed in MOC2-CD271 and HSC3-CD271, compared with respective parental cells. CD271 activation by NGF conferred enhanced invasiveness in CD271-overexpressing cells, which was abrogated by Snai2 knockdown. In PDXs and primary human HNSCC, CD271 expression correlated with higher Snai2 expression, greater nodal metastasis, and shorter disease-free survival.Conclusions: Activation of CD271 results in upregulation of Snai2/Slug, which, in turn, results in a more invasive phenotype and an enhanced capacity for metastasis to regional lymph nodes. These findings point to CD271 as a promising, therapeutic target for oral cancer metastasis. Clin Cancer Res; 24(3); 674-83. ©2017 AACR.

Endothelial-derived interleukin-6 induces cancer stem cell motility by generating a chemotactic gradient towards blood vessels

Recent evidence suggests that the metastatic spread of head and neck squamous cell carcinomas (HNSCC) requires the function of cancer stem cells endowed with multipotency, self-renewal, and high tumorigenic potential. We demonstrated that cancer stem cells reside in perivascular niches and are characterized by high aldehyde dehydrogenase (ALDH) activity and high CD44 expression (ALDHhighCD44high) in HNSCC. Here, we hypothesize that endothelial cell-secreted interleukin-6 (IL-6) contributes to tumor progression by enhancing the migratory phenotype and survival of cancer stem cells. Analysis of tissue microarrays generated from the invasive fronts of 77 HNSCC patients followed-up for up to 11 years revealed that high expression of IL-6 receptor (IL-6R) (p=0.0217) or co-receptor gp130 (p=0.0422) correlates with low HNSCC patient survival. We observed that endothelial cell-secreted factors induce epithelial to mesenchymal transition (EMT) and enhance invasive capacity of HNSCC cancer stem cells. Conditioned medium from CRISPR/Cas9-mediated IL-6 knockout primary human endothelial cells is less chemotactic for cancer stem cells in a microfluidics-based system than medium from control endothelial cells (p<0.05). Blockade of the IL-6 pathway with a humanized anti-IL-6R antibody (tocilizumab) inhibited endothelial cell-induced motility in vitro and decreased the fraction of cancer stem cells in vivo. Notably, xenograft HNSCC tumors vascularized with IL-6-knockout endothelial cells exhibited slower tumor growth and smaller cancer stem cell fraction. These findings demonstrate that endothelial cell-secreted IL-6 enhances the motility and survival of highly tumorigenic cancer stem cells, suggesting that endothelial cells can create a chemotactic gradient that enables the movement of carcinoma cells towards blood vessels.

Novel C-Terminal Heat Shock Protein 90 Inhibitors (KU711 and Ku757) Are Effective in Targeting Head and Neck Squamous Cell Carcinoma Cancer Stem cells

Advanced head and neck squamous cell carcinoma (HNSCC) remains a therapeutic challenge due to the development of therapy resistance. Several studies have implicated the development of cancer stem cells as a possible mechanism for therapy resistance in HNSCC. Heat shock protein 90's (Hsp90's) molecular chaperone function is implicated in pathways of resistance in HNSCC. Therefore, in the present study, we investigated the efficacy of novel C-terminal Hsp90 inhibitors (KU711 and KU757) in targeting HNSCC cancer stem cells (CSCs). Treatment of HNSCC human cell lines MDA1986, UMSCC 22B, and UMSCC 22B cisplatin-resistant cells with the KU compounds indicated complete blockage of self-renewal for the resistant and parent cell lines starting from 20 μM KU711 and 1 μM KU757. Dose-dependent decrease in the cancer stem cell markers CD44, ALDH, and CD44/ALDH double-positive cells was observed for all cell lines after treatment with KU711 and KU757. When cells were treated with either drug, migration and invasion were downregulated greater than 90% even at the lowest concentrations of 20 μM KU711 and 1 μM KU757. Western blot showed >90% reduction in client protein "stemness" marker BMI-1 and mesenchymal marker vimentin, as well as increase in epithelial marker E-cadherin for both cell lines, indicating epithelial to mesenchymal transition quiescence. Several CSC-mediated miRNAs that play a critical role in HNSCC therapy resistance were also downregulated with KU treatment. In vivo, KU compounds were effective in decreasing tumor growth with no observed toxicity. Taken together, these results indicate that KU compounds are effective therapeutics for targeting HNSCC CSCs.

Trends in Surgical Research in Head and Neck Cancer

OPINION STATEMENT

The task of surgical research is to improve the efficacy of available surgical therapeutic modalities, develop new ones, and balance this well with favorable functional outcome. Therefore, surgical research is composed of a translational and a clinical component. In translational surgical research, animal models are used to better understand the biology of head and neck cancers, but even more importantly, the biology of changes to the disease and the microenvironment created by surgical interventions. Animal models additionally allow for the development of image-guided surgery systems, novel strategies of intraoperative adjuvant treatment, and patient "avatars" to test innovative anticancer drug combinations. In clinical surgical research, surgical techniques are validated in clinical trials for effectiveness of tumor control and improvement of functional recovery of the patient. In conclusion, surgical research for head and neck cancer is an active field spanning across the entire breadth of basic and clinical science devoted to a better understanding of what surgery does to the disease and to the patient.

CD109 released from human bone marrow mesenchymal stem cells attenuates TGF-β-induced epithelial to mesenchymal transition and stemness of squamous cell carcinoma

Although there is increasing evidence that human bone marrow mesenchymal stem cells (hBM-MSCs) play an important role in cancer progression, the underlying mechanisms are poorly understood. Transforming growth factor β (TGF-β) is an important pro-metastatic cytokine. We have previously shown that CD109, a glycosylphosphatidylinositol-anchored protein, is a TGF-β co-receptor and a strong inhibitor of TGF-β signalling. Moreover, CD109 can be released from the cell surface. In the current study, we examined whether hBM-MSCs regulate the malignant properties of squamous cell carcinoma cells, and whether CD109 plays a role in mediating the effect of hBM-MSCs on cancer cells. Here we show that hBM-MSC-conditioned medium decreases proliferation and induces apoptosis in human squamous carcinoma cell lines, A431 and FaDu. Importantly, hBM-MSC-conditioned medium markedly suppresses markers of epithelial-to-mesenchymal transition and stemness, and concomitantly decreases cell migration, invasion, and spheroid formation in A431 and FaDu cells. In addition, knockdown of CD109 in hBM-MSCs abrogates the anti-malignant activity of hBM-MSC-conditioned medium on A431 and FaDu cells. Furthermore, overexpression of CD109 in A431 cells decreases their malignant traits. Together, our findings suggest that hBM-MSCs inhibit the malignant traits of squamous cell carcinoma cells by a paracrine effect via released factors and that CD109 released from hBM-MSCs, at least partially, mediates these effects.

Simulation of head and neck cancer oxygenation and doubling time in a 4D cellular model with angiogenesis

Tumor oxygenation has been correlated with treatment outcome for radiotherapy. In this work, the dependence of tumor oxygenation on tumor vascularity and blood oxygenation was determined quantitatively in a 4D stochastic computational model of head and neck squamous cell carcinoma (HNSCC) tumor growth and angiogenesis. Additionally, the impacts of the tumor oxygenation and the cancer stem cell (CSC) symmetric division probability on the tumor volume doubling time and the proportion of CSCs in the tumor were also quantified. Clinically relevant vascularities and blood oxygenations for HNSCC yielded tumor oxygenations in agreement with clinical data for HNSCC. The doubling time varied by a factor of 3 from well oxygenated tumors to the most severely hypoxic tumors of HNSCC. To obtain the doubling times and CSC proportions clinically observed in HNSCC, the model predicts a CSC symmetric division probability of approximately 2% before treatment. To obtain the doubling times clinically observed during treatment when accelerated repopulation is occurring, the model predicts a CSC symmetric division probability of approximately 50%, which also results in CSC proportions of 30-35% during this time.

Development of an in silico stochastic 4D model of tumor growth with angiogenesis

PURPOSE

A stochastic computer model of tumour growth with spatial and temporal components that includes tumour angiogenesis was developed. In the current work it was used to simulate head and neck tumour growth. The model also provides the foundation for a 4D cellular radiotherapy simulation tool.

METHODS

The model, developed in Matlab, contains cell positions randomised in 3D space without overlap. Blood vessels are represented by strings of blood vessel units which branch outwards to achieve the desired tumour relative vascular volume. Hypoxic cells have an increased cell cycle time and become quiescent at oxygen tensions less than 1 mmHg. Necrotic cells are resorbed. A hierarchy of stem cells, transit cells and differentiated cells is considered along with differentiated cell loss. Model parameters include the relative vascular volume (2-10%), blood oxygenation (20-100 mmHg), distance from vessels to the onset of necrosis (80-300 μm) and probability for stem cells to undergo symmetric division (2%). Simulations were performed to observe the effects of hypoxia on tumour growth rate for head and neck cancers. Simulations were run on a supercomputer with eligible parts running in parallel on 12 cores.

RESULTS

Using biologically plausible model parameters for head and neck cancers, the tumour volume doubling time varied from 45 ± 5 days (n = 3) for well oxygenated tumours to 87 ± 5 days (n = 3) for severely hypoxic tumours.

CONCLUSIONS

The main achievements of the current model were randomised cell positions and the connected vasculature structure between the cells. These developments will also be beneficial when irradiating the simulated tumours using Monte Carlo track structure methods.

5T4-Targeted Therapy Ablates Cancer Stem Cells and Prevents Recurrence of Head and Neck Squamous Cell Carcinoma

Purpose: Locoregional recurrence is a frequent treatment outcome for patients with advanced head and neck squamous cell carcinoma (HNSCC). Emerging evidence suggests that tumor recurrence is mediated by a small subpopulation of uniquely tumorigenic cells, that is, cancer stem cells (CSC), that are resistant to conventional chemotherapy, endowed with self-renewal and multipotency.Experimental Design: Here, we evaluated the efficacy of MEDI0641, a novel antibody-drug conjugate targeted to 5T4 and carrying a DNA-damaging "payload" (pyrrolobenzodiazepine) in preclinical models of HNSCC.Results: Analysis of a tissue microarray containing 77 HNSCC with follow-up of up to 12 years revealed that patients with 5T4^high tumors displayed lower overall survival than those with 5T4^low tumors (P = 0.038). 5T4 is more highly expressed in head and neck CSC (ALDH^highCD44^high) than in control cells (non-CSC). Treatment with MEDI0641 caused a significant reduction in the CSC fraction in HNSCC cells (UM-SCC-11B, UM-SCC-22B) in vitro Notably, a single intravenous dose of 1 mg/kg MEDI0641 caused long-lasting tumor regression in three patient-derived xenograft (PDX) models of HNSCC. MEDI0641 ablated CSC in the PDX-SCC-M0 model, reduced it by five-fold in the PDX-SCC-M1, and two-fold in the PDX-SCC-M11 model. Importantly, mice (n = 12) treated with neoadjuvant, single administration of MEDI0641 prior to surgical tumor removal showed no recurrence for more than 200 days, whereas the control group had 7 recurrences (in 12 mice; P = 0.0047).Conclusions: Collectively, these findings demonstrate that an anti-5T4 antibody-drug conjugate reduces the fraction of CSCs and prevents local recurrence and suggest a novel therapeutic approach for patients with HNSCC. Clin Cancer Res; 23(10); 2516-27. ©2016 AACR.

Therapeutic Inhibition of the MDM2-p53 Interaction Prevents Recurrence of Adenoid Cystic Carcinomas

Purpose: Conventional chemotherapy has modest efficacy in advanced adenoid cystic carcinomas (ACC). Tumor recurrence is a major challenge in the management of ACC patients. Here, we evaluated the antitumor effect of a novel small-molecule inhibitor of the MDM2-p53 interaction (MI-773) combined with cisplatin in patient-derived xenograft (PDX) ACC tumors.Experimental Design: Therapeutic strategies with MI-773 and/or cisplatin were evaluated in SCID mice harboring PDX ACC tumors (UM-PDX-HACC-5) and in low passage primary human ACC cells (UM-HACC-2A, -2B, -5, -6) in vitro The effect of therapy on the fraction of cancer stem cells (CSC) was determined by flow cytometry for ALDH activity and CD44 expression.Results: Combined therapy with MI-773 with cisplatin caused p53 activation, induction of apoptosis, and regression of ACC PDX tumors. Western blots revealed induction of MDM2, p53 and downstream p21 expression, and regulation of apoptosis-related proteins PUMA, BAX, Bcl-2, Bcl-x_L, and active caspase-9 upon MI-773 treatment. Both single-agent MI-773 and MI-773 combined with cisplatin decreased the fraction of CSCs in PDX ACC tumors. Notably, neoadjuvant MI-773 and surgery eliminated tumor recurrences during a postsurgical follow-up of more than 300 days. In contrast, 62.5% of mice that received vehicle control presented with palpable tumor recurrences within this time period (P = 0.0097).Conclusions: Collectively, these data demonstrate that therapeutic inhibition of MDM2-p53 interaction by MI-773 decreased the CSC fraction, sensitized ACC xenograft tumors to cisplatin, and eliminated tumor recurrence. These results suggest that patients with ACC might benefit from the therapeutic inhibition of the MDM2-p53 interaction. Clin Cancer Res; 23(4); 1036-48. ©2016 AACR.

IL-6 Inhibition With MEDI5117 Decreases The Fraction of Head and Neck Cancer Stem Cells and Prevents Tumor Recurrence

Head and neck squamous cell carcinomas (HNSCC) exhibit a small population of uniquely tumorigenic cancer stem cells (CSC) endowed with self-renewal and multipotency. We have recently shown that IL-6 enhances the survival and tumorigenic potential of head and neck cancer stem cells (i.e. ALDH(high)CD44(high) cells). Here, we characterized the effect of therapeutic inhibition of IL-6 with a novel humanized anti-IL-6 antibody (MEDI5117) using three low-passage patient-derived xenograft (PDX) models of HNSCC. We observed that single agent MEDI5117 inhibited the growth of PDX-SCC-M1 tumors (P < .05). This PDX model was generated from a previously untreated HNSCC. In contrast, MEDI5117 was not effective at reducing overall tumor volume for PDX models representing resistant disease (PDX-SCC-M0, PDX-SCC-M11). Low dose MEDI5117 (3 mg/kg) consistently decreased the fraction of cancer stem cells in PDX models of HNSCC when compared to IgG-treated controls, as follows: PDX-SCC-M0 (P < .001), PDX-SCC-M1 (P < .001), PDX-SCC-M11 (P = .04). Interestingly, high dose MEDI5117 (30 mg/kg) decreased the CSC fraction in the PDX-SCC-M11 model (P = .002), but not in PDX-SCC-M0 and PDX-SCC-M1. MEDI5117 mediated a dose-dependent decrease in the number of orospheres generated by ALDH(high)CD44(high) cells cultured in ultra-low attachment plates (P < .05), supporting an inhibitory effect on head and neck cancer stem cells. Notably, single agent MEDI5117 reduced the overall recurrence rate of PDX-SCC-M0, a PDX generated from the local recurrence of human HNSCC. Collectively, these data demonstrate that therapeutic inhibition of IL-6 with low-dose MEDI5117 decreases the fraction of cancer stem cells, and that adjuvant MEDI5117 inhibits recurrence in preclinical models of HNSCC.

The Tip of the Iceberg: Clinical Implications of Genomic Sequencing Projects in Head and Neck Cancer

Recent genomic sequencing studies have provided valuable insight into genetic aberrations in head and neck squamous cell carcinoma. Despite these great advances, certain hurdles exist in translating genomic findings to clinical care. Further correlation of genetic findings to clinical outcomes, additional analyses of subgroups of head and neck cancers and follow-up investigation into genetic heterogeneity are needed. While the development of targeted therapy trials is of key importance, numerous challenges exist in establishing and optimizing such programs. This review discusses potential upcoming steps for further genetic evaluation of head and neck cancers and implementation of genetic findings into precision medicine trials.

Targeting Head and Neck Cancer Stem Cells: Current Advances and Future Challenges

Cancer stem cells (CSCs), or tumor-initiating cells, comprise a subset of tumor cells with demonstrated ability for tumor growth, invasion, metastasis, and resistance to chemotherapy and radiation. Targeting of CSCs remains an attractive yet elusive therapeutic option, with the goal of increasing specificity and effectiveness in tumor eradication, as well as decreasing off-target or systemic toxicity. Research into further characterization and targeted therapy toward head and neck CSCs is an active and rapidly evolving field. This review discusses the current state of research into therapy against head and neck CSCs and future directions for targeted therapy.

CD271 is a functional and targetable marker of tumor-initiating cells in head and neck squamous cell carcinoma

Tumor-initiating cells (TICs) in squamous cell carcinoma of the head and neck (SCCHN) are best characterized by their surface expression of CD44. Although there is great interest in identifying strategies to target this population, no marker of these cells has been found to be functionally active. Here, we examined the expression of the purported marker of normal human oral epithelial stem cells, CD271. We show that CD271 expression is restricted to a subset of the CD44⁺ cells. Using xenograft assays, we show that the CD44⁺CD271⁺ subpopulation contains the most tumorigenic cells. Loss of CD271 function results in a block in the G2-M phase of the cell cycle and a profound negative impact on the capacity of these cells to initiate tumor formation in vivo. Incubation with recombinant NGF results in enhanced phosphorylation of Erk, providing additional evidence that CD271 is functionally active. Finally, incubation of SCCHN cells with antibody to CD271 results in decreased Erk phosphorylation and decreased tumor formation in vivo. Thus, our data are the first to demonstrate that CD271 more specifically identifies the TIC subpopulation within the CD44⁺ compartment in SCCHN and that this receptor is a functionally active and targetable molecule.

Identification of molecular signature of head and neck cancer stem-like cells

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer in the world. HNSCC remains difficult to treat, and despite advances in treatment, overall survival rate has modestly improved over the past several years. Poor survival rate is attributed to high frequency of local recurrence and distant metastasis. Cancer stem-like cells (CSCs) have been implicated in tumor recurrence and confer resistance to anti-cancer therapy treatment. In this study, we have characterized genes that are modulated in HNSCC-CSCs and can be targeted in future as potential therapeutics. CSCs were isolated from HNSCC cells (oralspheres) and examined for tumorigenicity in immunodeficient mice. We observed aggressive tumor growth with oralspheres as compared to parental cells. The CSC-derived tumors were grossly extremely vascularized and expressed VEGFR1. We next analyzed the molecular determinant of oralspheres. In addition to CD133 and Nanog, we observed significant higher expression of Notch1 protein in the oralspheres. There was differential expression of angiogenesis and invasive marker genes such as angiopoietin1, integrin β3, MMP9 and THBS1. Interestingly, c-Fos was upregulated in oralspheres as compared to parental cells. Our observations suggest that understanding the molecular determinant of oralspheres will help in developing future therapeutic modalities against treatment resistant HNSCC.

SMURF1 silencing diminishes a CD44-high cancer stem cell-like population in head and neck squamous cell carcinoma

BACKGROUND

Bone morphogenetic protein (BMP) signaling is thought to play key roles in regulating the survival and maintenance of cancer stem cells (CSCs), which contribute to disease recurrences and treatment failures in many malignances, including head and neck squamous cell carcinoma (HNSCC). Intracellular BMP signaling is regulated by SMAD specific E3 ubiquitin protein ligase 1 (SMURF1) during cellular development. However, little is known about the role or regulation of BMP signaling in HNSCC CSCs.

METHODS

Two CSC-like populations, CD44(high)/BMI1(high) and CD44(high)/ALDH(high), were enriched from HNSCC cell lines and evaluated for the expression of SMURF1 by qRT-PCR, flow cytometry, and immunoblotting. The activation status of BMP signaling in these populations was determined by using immunoblotting to detect phosphorylated SMAD1/5/8 (pSMAD1/5/8) levels. Knockdown of SMURF1 transcripts by RNA interference was used to assess the role of SMURF1 in BMP signaling and CSC maintenance. Loss of CSC-like phenotypes following SMURF1 knockdown was determined by changes in CD44(high) levels, cellular differentiation, and reduction in colony formation.

RESULTS

Populations of enriched CSC-like cells displayed decreased levels of pSMAD1/5/8 and BMP signaling target gene ID1 while SMURF1, CD44, and BMI1 were highly expressed when compared to non-CSC populations. Stable knockdown of SMURF1 expression in CSC-like cells increased pSMAD1/5/8 protein levels, indicating the reactivation of BMP signaling pathways. Decreased expression of SMURF1 also promoted adipogenic differentiation and reduced colony formation in a three-dimensional culture assay, indicating loss of tumorigenic capacity. The role of SMURF1 and inhibition of BMP signaling in maintaining a CSC-like population was confirmed by the loss of a CD44(high) expressing subpopulation in SMURF1 knockdown cells.

CONCLUSIONS

Our findings suggest that inhibition of BMP signaling potentiates the long-term survival of HNSCC CSCs, and that this inhibition is mediated by SMURF1. Targeting SMURF1 and restoring BMP signaling may offer a new therapeutic approach to promote differentiation and reduction of CSC populations leading to reduced drug resistance and disease recurrence.

Human papillomavirus induced transformation in cervical and head and neck cancers

Human papillomavirus (HPV) is one of the most widely publicized and researched pathogenic DNA viruses. For decades, HPV research has focused on transforming viral activities in cervical cancer. During the past 15 years, however, HPV has also emerged as a major etiological agent in cancers of the head and neck, in particular squamous cell carcinoma. Even with significant strides achieved towards the screening and treatment of cervical cancer, and preventive vaccines, cervical cancer remains the leading cause of cancer-associated deaths for women in developing countries. Furthermore, routine screens are not available for those at risk of head and neck cancer. The current expectation is that HPV vaccination will prevent not only cervical, but also head and neck cancers. In order to determine if previous cervical cancer models for HPV infection and transformation are directly applicable to head and neck cancer, clinical and molecular disease aspects must be carefully compared. In this review, we briefly discuss the cervical and head and neck cancer literature to highlight clinical and genomic commonalities. Differences in prognosis, staging and treatment, as well as comparisons of mutational profiles, viral integration patterns, and alterations in gene expression will be addressed.

Sinonasal carcinoma: clinical, pathological, genetic and therapeutic advances

The sinonasal cavities represent an anatomical region affected by a variety of tumours with clinical, aetiological, pathological, and genetic features distinct from tumours at the main head and neck cancer localizations. Together, squamous-cell carcinoma and adenocarcinoma account for 80% of all sinonasal tumours, and are aetiologically associated with professional exposure to wood and leather dust particles and other industrial compounds, and therefore, are officially recognized as an occupational disease. Owing to their distinctive characteristics, sinonasal tumours should be considered as separate entities, not to be included in the miscellany of head and neck cancers. Sinonasal tumours are rare, with an annual incidence of approximately 1 case per 100,000 inhabitants worldwide, a fact that has hampered molecular-genetic studies of the tumorigenic pathways and the testing of alternative treatment strategies. Nevertheless, the clinical management of sinonasal cancer has improved owing to advances in imaging techniques, endoscopic surgical approaches, and radiotherapy. Genetic profiling and the development of in vitro cell lines and animal models currently form the basis for future targeted anticancer therapies. We review these advances in our understanding and treatment of sinonasal tumours.

Role of human papillomavirus in oropharyngeal squamous cell carcinoma: A review

Human papillomavirus (HPV) has been implicated in the pathogenesis of a subset of oropharyngeal squamous cell carcinoma. As a result, traditional paradigms in relation to the management of head and neck squamous cell carcinoma have been changing. Research into HPV-related oropharyngeal squamous cell carcinoma is rapidly expanding, however many molecular pathological and clinical aspects of the role of HPV remain uncertain and are the subject of ongoing investigation. A detailed search of the literature pertaining to HPV-related oropharyngeal squamous cell carcinoma was performed and information on the topic was gathered. In this article, we present an extensive review of the current literature on the role of HPV in oropharyngeal squamous cell carcinoma, particularly in relation to epidemiology, risk factors, carcinogenesis, biomarkers and clinical implications. HPV has been established as a causative agent in oropharyngeal squamous cell carcinoma and biologically active HPV can act as a prognosticator with better overall survival than HPV-negative tumours. A distinct group of younger patients with limited tobacco and alcohol exposure have emerged as characteristic of this HPV-related subset of squamous cell carcinoma of the head and neck. However, the exact molecular mechanisms of carcinogenesis are not completely understood and further studies are needed to assist development of optimal prevention and treatment modalities.