Mouse models for human head and neck squamous cell carcinomas

Cancer stem cells in head and neck squamous cell carcinoma and its associated markers: A review

ABSTRACT

Evidences of the current research say that cancer is multifactorial with varied mechanisms of origin. Most theories evolve either intrinsic (genetic) or extrinsic factors like tobacco and alcoholism as the major cause of oral cancer in India. There is growing evidence that human papilloma virus may act as a co-carcinogen, along with tobacco, in the causation of cancers. The cells being triggered by the agents may be somatic (differentiated functional cell) or a normal stem cell with multipotency or even the transient proliferative cells derived from the stem cells. These stem cells possess several features like slow cell cycle, ability to extrude chemotherapeutic drugs, exhibit epithelial mesenchymal transition, and inhibit apoptosis. Targeting these progenitor stem cells may aid in improving the overall prognosis of the patient. These cancer stem cells are targeted using various markers that are apparently more or less specific to various types of stem cells.

Gender Difference in DNA Damage Induced by the Environmental Carcinogen Dibenzo[def,p]chrysene Individually and in Combination with Mouse Papillomavirus Infection in the Mouse Oral Cavity

Tobacco smoking and human papillomavirus infection are established etiological agents in the development of head and neck squamous cell carcinoma (HNSCC). The incidence and mortality of HNSCC are higher in men than women. To provide biochemical basis for sex differences, we tested the hypothesis that carcinogen treatment using dibenzo[def,p]chrysene, which is an environmental pollutant and tobacco smoke constituent, in the absence or presence of the mouse papillomavirus infection results in significantly higher levels of DNA damage in the oral cavity in male than in female mice. However, the results of the present investigation do not support our hypothesis since we found that females were more susceptible to carcinogen-induced covalent DNA damage than males independent of the viral infection. Since DNA damage represents only a single-step in the carcinogenesis process, additional factors may contribute to sex differences in humans.

In vitro models as tools for screening treatment options of head and neck cancer

Various in vitro models using primary and established 2- and 3-dimensional cultures, multicellular tumor spheroids, standardized tumor slice cultures, tumor organoids, and microfluidic systems obtained from tumor lesions/biopsies of head and neck cancer (HNC) have been employed for exploring and monitoring treatment options. All of these in vitro models are to a different degree able to capture the diversity of tumors, recapitulate the disease genetically, histologically, and functionally and retain their tumorigenic potential upon xenotransplantation. The models were used for the characterization of the malignant features of the tumors and for in vitro screens of drugs approved for the treatment of HNC, including chemotherapy and radiotherapy as well as recently developed targeted therapies and immunotherapies, or for novel treatments not yet licensed for these tumor entities. The implementation of the best suitable model will enlarge our knowledge of the oncogenic properties of HNC, expand the drug repertoire and help to develop individually tailored treatment strategies resulting in the translation of these findings into the clinic. This review summarizes the different approaches using preclinical in vitro systems with their advantages and disadvantages and their implementation as preclinical platforms to predict disease course, evaluate biomarkers and test therapy efficacy.

Molecular immuno-imaging improves tumor detection in head and neck cancer

Detection and accurate delineation of tumor is important for the management of head and neck squamous cell carcinoma (HNSCC) but is challenging with current imaging techniques. In this study, we evaluated whether molecular immuno-imaging targeting myeloperoxidase (MPO) activity, an oxidative enzyme secreted by many myeloid innate immune cells, would be superior in detecting tumor extent compared to conventional contrast agent (DTPA-Gd) in a carcinogen-induced immunocompetent HNSCC murine model and corroborated in human surgical specimens. In C57BL/6 mice given 4-nitroquinoline-N-oxide (4-NQO), there was increased MPO activity in the head and neck region as detected by luminol bioluminescence compared to that of the control group. On magnetic resonance imaging, the mean enhancing volume detected by the MPO-targeting agent (MPO-Gd) was higher than that by the conventional agent DTPA-Gd. The tumor volume detected by MPO-Gd strongly correlated with tumor size on histology, and higher MPO-Gd signal corresponded to larger tumor size found by imaging and histology. On the contrary, the tumor volume detected by DTPA-Gd did not correlate as well with tumor size on histology. Importantly, MPO-Gd imaging detected areas not visualized with DTPA-Gd imaging that were confirmed histopathologically to represent early tumor. In human specimens, MPO was similarly associated with tumors, especially at the tumor margins. Thus, molecular immuno-imaging targeting MPO not only detects oxidative immune response in HNSCC, but can better detect and delineate tumor extent than nonselective imaging agents. Thus, our findings revealed that MPO imaging could improve tumor resection as well as be a useful imaging biomarker for tumor progression, and potentially improve clinical management of HNSCC once translated.

TNFα Signaling Is Increased in Progressing Oral Potentially Malignant Disorders and Regulates Malignant Transformation in an Oral Carcinogenesis Model

Oral carcinogenesis represents a multi-stage process which encompasses several genetic and molecular changes that promote the progression of oral potentially malignant disorders (OPMDs) to oral squamous cell carcinomas (OSCCs). A better understanding of critical pathways governing the progression of OMPDs to OSCCs is critical to improve oncologic outcomes in the future. Previous studies have identified an important role of tumor necrosis factor α (TNFα) and TNF receptor 1 (TNFR1) in the invasiveness of oral cancer cell lines. Here, we investigate the expression of TNFα and TNFR1 in human OPMDs that progress to OSCC compared to non-progressing OPMDs utilizing fluorescent immunohistochemistry (FIHC) to show increased TNFα/TNFR1 expression in progressing OPMDs. In order to interrogate the TNFα/TNFR1 signaling pathway, we utilized a 4-nitroquinoline 1-oxide (4-NQO) mouse model of oral carcinogenesis to demonstrate that TNFα/TNFR1 expression is upregulated in 4-NQO-induced OSCCs. TNFα neutralization decreased serum cytokines, inhibited the development of invasive lesions and reduced tumor-associated neutrophils in vivo. Combined, this data supports the role of TNFα in oral malignant transformation, suggesting that critical immunoregulatory events occur downstream of TNFR1 leading to malignant transformation. Our results advance the understanding of the mechanisms governing OSCC invasion and may serve as a basis for alternative diagnostic and therapeutic approaches to OPMDs and OSCC management.

Molecular homology between canine spontaneous oral squamous cell carcinomas and human head-and-neck squamous cell carcinomas reveals disease drivers and therapeutic vulnerabilities

Spontaneously occurring canine oral squamous cell carcinomas (COSCC) are viewed as a useful model for human head and neck squamous cell carcinomas (HNSCC). To date however, the molecular basis of COSCC remains poorly understood. To identify changes pertinent to cancer cells in COSCC, we specifically analyzed tumor cells and matched normal epithelium from clinical formalin-fixed paraffin-embedded specimens using laser-capture-microdissection coupled with RNA-sequencing (RNAseq). Our results identify strong contributions of epithelial-to-mesenchymal transition (EMT), classical tumor-promoting (such as E2F, KRAS, MYC, mTORC1, and TGFB1 signaling) and immune-related pathways in the tumor epithelium of COSCC. Comparative analyses of COSCC with 43 paired tumor/normal HNSCC from The Cancer Genome Atlas revealed a high homology in transcriptional reprogramming, and identified processes associated with cell cycle progression, immune processes, and loss of cellular differentiation as likely central drivers of the disease. Similar to HNSCC, our analyses suggested a ZEB2-driven partial EMT in COSCC and identified selective upregulation of KRT14 and KRT17 in COSCC. Beyond homology in transcriptional signatures, we also found therapeutic vulnerabilities strongly conserved between the species: these included increased expression of PD-L1 and CTLA-4, coinciding with EMT and revealing the potential for immune checkpoint therapies, and overexpression of CDK4/6 that sensitized COSCC to treatment with palbociclib. In summary, our data significantly extend the current knowledge of molecular aberrations in COSCC and underline the potential of spontaneous COSCC as a model for HNSCC to interrogate therapeutic vulnerabilities and support translation of novel therapies from bench to bedside.

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

A Novel Multimodal NIR-II Nanoprobe for the Detection of Metastatic Lymph Nodes and Targeting Chemo-Photothermal Therapy in Oral Squamous Cell Carcinoma

Current surgical treatment for oral squamous cell carcinoma (OSCC) must be as precise as possible to fully resect tumors and preserve functional tissues. Thus, it is urgent to develop efficient fluorescent probes to clearly identify tumor delineation, as well as metastatic lymph nodes. Chemo-photothermal therapy combination attracted a growing attention to increase anti-tumor effect in various types of cancer, including OSCC. In the present study, we designed a multimodal NIR-II probe that involves combining photothermal therapy with chemotherapy, imaging OSCC tumors and detecting metastatic lymph nodes. Methods: In this study, we synthesized a novel near infrared (NIR)-II probe named TQTPA [4,4'-((6,7-bis(4-(hexyloxy)phenyl)-[1,2,5]thiadiazolo [3,4-g]quinoxaline-4,9-diyl)bis(thiophene-5,2-diyl))bis(N,N-diphenylaniline)] via the Suzuki reaction and prepared multimodal nanoparticles (NPs) loading TQTPA and cis-dichlorodiammine platinum (CDDP) (HT@CDDP) by hyaluronic acid. The characteristics of the NPs, including their photothermal and imaging capabilities were investigated in vitro and in vivo. Their anti-tumor efficacy was evaluated using orthotopic, tongue tumor-bearing, nude mice. Results: The NPs possessed good stability and water solubility and were pH/hyaluronidase sensitive. The good tissue penetration quality and active targeting ability enabled the NPs to draw the outline of orthotopic tongue tumors and metastatic lymph nodes as small as 1 mm in nude mice by IR-808 under NIR exposure. In vitro and in vivo experiments validated the biocompatibility and low systematic toxicity of the NPs. At the same time, the NPs acted as multimodal therapy agents, combining photothermal therapy with chemotherapy. Conclusion: With a good imaging capability and anti-tumor efficacy, our NPs successfully outlined orthotopic tongue tumors and metastatic lymph nodes as well as enabled chemo-photothermal therapy combination. Our study established a solid foundation for the application of new clinical diagnosis and treatment patterns in the future.

Cooperation Between Pten and Smad4 in Murine Salivary Gland Tumor Formation and Progression

Salivary gland tumor (SGT) is a rare tumor type, which exhibits broad-spectrum phenotypic, biological, and clinical heterogeneity. Currently, the molecular mechanisms that cause SGT pathogenesis remain poorly understood. A lack of animal models that faithfully recapitulate the naturally occurring process of human SGTs has hampered research progress on this field. In this report, we developed an inducible keratin 5-driven conditional knockout mouse model to delete gene(s) of interest in murine salivary gland upon local RU486 delivery. We have deleted two major tumor suppressors, Pten, a negative regulator of the PI3K pathway, and Smad4, the central signaling mediator of TGFβ pathway, in the murine salivary gland. Our results have shown that deletion of either Pten or Smad4 in murine salivary gland resulted in pleomorphic adenomas, the most common tumor in human SGT patients. Deletion of both Pten and Smad4 in murine salivary gland developed several malignancies, with salivary adenoid cystic carcinoma (SACC) being the most frequently seen. Molecular characterization showed that SACC exhibited mTOR activation and TGFβ1 overexpression. Examination of human SGT clinical samples revealed that loss of Pten and Smad4 is common in human SACC samples, particularly in the most aggressive solid form, and is correlated with survival of SACC patients, highlighting the human relevance of the murine models. In summary, our results offer significant insight into synergistic role of Pten and Smad4 in SGT, providing a rationale for targeting mTOR and/or TGFβ signaling to control SGT formation and progression.

TNFRSF19 Inhibits TGFβ Signaling through Interaction with TGFβ Receptor Type I to Promote Tumorigenesis

Genetic susceptibility underlies the pathogenesis of cancer. We and others have previously identified a novel susceptibility gene TNFRSF19, which encodes an orphan member of the TNF receptor superfamily known to be associated with nasopharyngeal carcinoma (NPC) and lung cancer risk. Here, we show that TNFRSF19 is highly expressed in NPC and is required for cell proliferation and NPC development. However, unlike most of the TNF receptors, TNFRSF19 was not involved in NFκB activation or associated with TRAF proteins. We identified TGFβ receptor type I (TβRI) as a specific binding partner for TNFRSF19. TNFRSF19 bound the kinase domain of TβRI in the cytoplasm, thereby blocking Smad2/3 association with TβRI and subsequent signal transduction. Ectopic expression of TNFRSF19 in normal epithelial cells conferred resistance to the cell-cycle block induced by TGFβ, whereas knockout of TNFRSF19 in NPC cells unleashed a potent TGFβ response characterized by upregulation of Smad2/3 phosphorylation and TGFβ target gene transcription. Furthermore, elevated TNFRSF19 expression correlated with reduced TGFβ activity and poor prognosis in patients with NPC. Our data reveal that gain of function of TNFRSF19 in NPC represents a mechanism by which tumor cells evade the growth-inhibitory action of TGFβ.Significance:TNFRSF19, a susceptibility gene for nasopharyngeal carcinoma and other cancers, functions as a potent inhibitor of the TGFβ signaling pathway.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3469/F1.large.jpg Cancer Res; 78(13); 3469-83. ©2018 AACR.

Immunocompromised and immunocompetent mouse models for head and neck squamous cell carcinoma

Mouse models can closely mimic human oral squamous epithelial carcinogenesis, greatly expand the in vivo research possibilities, and play a critical role in the development of diagnosis, monitoring, and treatment of head and neck squamous cell carcinoma. With the development of the recent research on the contribution of immunity/inflammation to cancer initiation and progression, mouse models have been divided into two categories, namely, immunocompromised and immunocompetent mouse models. And thus, this paper will review these two kinds of models applied in head and neck squamous cell carcinoma to provide a platform to understand the complicated histological, molecular, and genetic changes of oral squamous epithelial tumorigenesis.

Animal models of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the most common oral cancer worldwide. Local bone invasion into the maxilla or mandible and metastasis to regional lymph nodes often result in a poor prognosis, decreased quality of life and shortened survival time for HNSCC patients. Poor response to treatment and clinical outcomes are the major concerns in this aggressive cancer. Multiple animal models have been developed to replicate spontaneous HNSCC and investigate genetic alterations and novel therapeutic targets. This review provides an overview of HNSCC as well as the traditional animal models used in HNSCC preclinical research. The value and challenges of each in vivo model are discussed. Similarity between HNSCC in humans and cats and the possibility of using spontaneous feline oral squamous cell carcinoma (FOSCC) as a model for HNSCC in translational research are highlighted.

Conditional deletion of nonmuscle myosin II-A in mouse tongue epithelium results in squamous cell carcinoma

To investigate the contribution of nonmuscle myosin II-A (NM II-A) to early cardiac development we crossed Myh9 floxed mice and Nkx2.5 cre-recombinase mice. Nkx2.5 is expressed in the early heart (E7.5) and later in the tongue epithelium. Mice homozygous for deletion of NM II-A (A^Nkx/A^Nkx) are born at the expected ratio with normal hearts, but consistently develop an invasive squamous cell carcinoma (SCC) of the tongue (32/32 A^Nkx/A^Nkx) as early as E17.5. To assess reproducibility a second, independent line of Myh9 floxed mice derived from a different embryonic stem cell clone was tested. This second line also develops SCC indistinguishable from the first (15/15). In A^Nkx/A^Nkx mouse tongue epithelium, genetic deletion of NM II-A does not affect stabilization of TP53, unlike a previous report for SCC. We attribute the consistent, early formation of SCC with high penetrance to the role of NM II in maintaining mitotic stability during karyokinesis.

Single and Multiple Gene Manipulations in Mouse Models of Human Cancer

Mouse models of human cancer play a critical role in understanding the molecular and cellular mechanisms of tumorigenesis. Advances continue to be made in modeling human disease in a mouse, though the relevance of a mouse model often relies on how closely it is able to mimic the histologic, molecular, and physiologic characteristics of the respective human cancer. A classic use of a genetically engineered mouse in studying cancer is through the overexpression or deletion of a gene. However, the manipulation of a single gene often falls short of mimicking all the characteristics of the carcinoma in humans; thus a multiple gene approach is needed. Here we review genetic mouse models of cancers and their abilities to recapitulate human carcinoma with single versus combinatorial approaches with genes commonly involved in cancer.

Cancer stem cells and stemness markers in oral squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) is one of the world top ten most common cancers with its highest occurrence in the Indian subcontinent and different aggressive and etiological behavioural patterns. The scenario is only getting worst with the 5 year survival rates dropping to 50%, persistent treatment failures and frequent cases of relapse/recurrence. One of the major reasons for these failures is the presence of 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 bulk of tumours. Notably, recent evidence suggests that cancer stem cells are especially resistant to conventional therapy and are the "drivers" of local recurrence and metastatic spread. Specific markers for this population have been investigated in HNSCC in the hope of developing a deeper understanding of their role in oral cancer pathogenesis, elucidating novel biomarkers for early diagnosis and newer therapeutic strategies. This review covers the fundamental relevance of almost all the CSC biomarkers established to date with a special emphasis on their impact in the process of oral tumourigenesis and their potential role in improving the diagnosis, prognosis and treatment of OSCC patients.

Near-infrared fluorescence imaging-guided surgery improves recurrence-free survival rate in novel orthotopic animal model of head and neck squamous cell carcinoma

BACKGROUND

Appropriate animal models are required to test novel therapeutics for head and neck squamous cell carcinoma (HNSCC) such as near-infrared (NIR) imaging-guided surgery.

METHODS

We developed an optimized animal model of orthotopic HNSCC (in female athymic NMRI (Naval Medical Research Institute) nude mice) with a prolonged survival time. Resection of the orthotopic tumors was performed 30 days after implantation with or without the aid of a miniaturized clinical grade NIR optical imaging device, after systemic administration of a fluorescent RGD-based probe that targets αv β3 integrin.

RESULTS

NIR optical imaging-guided surgery increased the recurrence-free survival rate by 50% through the detection of fluorescent cancer residues as small as 185 µm; these fragments could remain unidentified if resection was performed exclusively under unaided visual guidance.

CONCLUSION

NIR optical imaging-guided surgery showed an improved HNSCC tumor resection quality in our optimized orthotopic animal model. © 2015 Wiley Periodicals, Inc. Head Neck 38: E246-E255, 2016.

Canine spontaneous head and neck squamous cell carcinomas represent their human counterparts at the molecular level

Spontaneous canine head and neck squamous cell carcinoma (HNSCC) represents an excellent model of human HNSCC but is greatly understudied. To better understand and utilize this valuable resource, we performed a pilot study that represents its first genome-wide characterization by investigating 12 canine HNSCC cases, of which 9 are oral, via high density array comparative genomic hybridization and RNA-seq. The analyses reveal that these canine cancers recapitulate many molecular features of human HNSCC. These include analogous genomic copy number abnormality landscapes and sequence mutation patterns, recurrent alteration of known HNSCC genes and pathways (e.g., cell cycle, PI3K/AKT signaling), and comparably extensive heterogeneity. Amplification or overexpression of protein kinase genes, matrix metalloproteinase genes, and epithelial-mesenchymal transition genes TWIST1 and SNAI1 are also prominent in these canine tumors. This pilot study, along with a rapidly growing body of literature on canine cancer, reemphasizes the potential value of spontaneous canine cancers in HNSCC basic and translational research.

Animal Models of Bone Metastasis

Bone is one of the most common sites of cancer metastasis in humans and is a significant source of morbidity and mortality. Bone metastases are considered incurable and result in pain, pathologic fracture, and decreased quality of life. Animal models of skeletal metastases are essential to improve the understanding of the molecular pathways of cancer metastasis and growth in bone and to develop new therapies to inhibit and prevent bone metastases. The ideal animal model should be clinically relevant, reproducible, and representative of human disease. Currently, an ideal model does not exist; however, understanding the strengths and weaknesses of the available models will lead to proper study design and successful cancer research. This review provides an overview of the current in vivo animal models used in the study of skeletal metastases or local tumor invasion into bone and focuses on mammary and prostate cancer, lymphoma, multiple myeloma, head and neck squamous cell carcinoma, and miscellaneous tumors that metastasize to bone.

Role of near-infrared fluorescence imaging in head and neck cancer surgery: from animal models to humans

Complete resection of head and neck cancers with negative surgical margins improves the prognosis of the disease and decreases the recurrence rate. Near-infrared fluorescence-guided surgery of head and neck cancer is a rapidly evolving field that represents an invaluable tool for tumor detection and resection. Here, we present a literature review of the principles of near-infrared fluorescence imaging and its use in head and neck cancer surgery. We discuss important studies in both animal models and humans that have been carried out up to this point. We also outline the important fluorescent molecules and devices used in head and neck fluorescence imaging-guided surgery. Although near-infrared fluorescence-guided surgery for head and neck cancers showed efficacy in animal models, its use in humans is limited by the small number of fluorescent probes that are approved for clinical use. However, it is considered as a novel surgical aid that helps delineate tumor margins preoperatively and could spare patients from the added morbidity that is associated with additional surgery or chemoradiation. In addition, it is a useful tool to detect sentinel lymph nodes as well as metastatic lymph nodes.

Use of high frequency ultrasound to monitor cervical lymph node alterations in mice

Cervical lymph node evaluation by clinical ultrasound is a non-invasive procedure used in diagnosing nodal status, and when combined with fine-needle aspiration cytology (FNAC), provides an effective method to assess nodal pathologies. Development of high-frequency ultrasound (HF US) allows real-time monitoring of lymph node alterations in animal models. While HF US is frequently used in animal models of tumor biology, use of HF US for studying cervical lymph nodes alterations associated with murine models of head and neck cancer, or any other model of lymphadenopathy, is lacking. Here we utilize HF US to monitor cervical lymph nodes changes in mice following exposure to the oral cancer-inducing carcinogen 4-nitroquinoline-1-oxide (4-NQO) and in mice with systemic autoimmunity. 4-NQO induces tumors within the mouse oral cavity as early as 19 wks that recapitulate HNSCC. Monitoring of cervical (mandibular) lymph nodes by gray scale and power Doppler sonography revealed changes in lymph node size eight weeks after 4-NQO treatment, prior to tumor formation. 4-NQO causes changes in cervical node blood flow resulting from oral tumor progression. Histological evaluation indicated that the early 4-NQO induced changes in lymph node volume were due to specific hyperproliferation of T-cell enriched zones in the paracortex. We also show that HF US can be used to perform image-guided fine needle aspirate (FNA) biopsies on mice with enlarged mandibular lymph nodes due to genetic mutation of Fas ligand (Fasl). Collectively these studies indicate that HF US is an effective technique for the non-invasive study of cervical lymph node alterations in live mouse models of oral cancer and other mouse models containing cervical lymphadenopathy.

Temporal characterization of lymphatic metastasis in an orthotopic mouse model of oral cancer

BACKGROUND

The overall mortality rate in cases of head and neck squamous cell carcinoma (HNSCC) has not improved over the past 30 years, mostly because of the high treatment failure rate among patients with regionally metastatic disease. To better understand the pathobiologic processes leading to lymphatic metastasis development, there is an urgent need for relevant animal models.

METHODS

HNSCC cell lines were implanted into the tongues of athymic nude mice. Histology, immunohistochemistry, and ex vivo 2-photon microscopy were used to evaluate tumor progress and spread.

RESULTS

Orthotopic xenografts of different HNSCC cell lines produced distinct patterns of survival, tumor histology, disease progression rate, and lymph node metastasis development. Remarkably, all injected cell types reached the lymph nodes within 24 hours after injection, but not all developed metastasis.

CONCLUSION

This orthotopic xenograft model closely mimics several characteristics of human cancer and could be extremely valuable for translational studies focusing on lymphatic metastasis development and pathobiology.

Angiogenesis in spontaneous tumors and implications for comparative tumor biology

Blood supply is essential for development and growth of tumors and angiogenesis is the fundamental process of new blood vessel formation from preexisting ones. Angiogenesis is a prognostic indicator for a variety of tumors, and it coincides with increased shedding of neoplastic cells into the circulation and metastasis. Several molecules such as cell surface receptors, growth factors, and enzymes are involved in this process. While antiangiogenic therapy for cancer has been proposed over 20 years ago, it has garnered much controversy in recent years within the scientific community. The complex relationships between the angiogenic signaling cascade and antiangiogenic substances have indicated the angiogenic pathway as a valid target for anticancer drug development and VEGF has become the primary antiangiogenic drug target. This review discusses the basic and clinical perspectives of angiogenesis highlighting the importance of comparative biology in understanding tumor angiogenesis and the integration of these model systems for future drug development.

PTEN deficiency contributes to the development and progression of head and neck cancer

The sequencing of the head and neck cancer has provided a blueprint of the most frequent genetic alterations in this cancer type. They include inactivating mutations in Notch, p53, and p16(ink4a) tumor suppressor genes, in addition to nonoverlapping activating mutations of the PIK3CA and RAS oncogenes or inactivation of the tumor suppressor gene PTEN. Notably, these genetic alterations, along with epigenetic changes, result in increased activity of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, which is present in most head and neck squamous cell carcinomas (HNSCCs). Moreover, we show here that approximately 30% of HNSCCs exhibit reduced PTEN expression. We challenged the biologic relevance of this finding by combining the intraoral administration of a tobacco surrogate, 4-nitroquinoline 1-oxide, with a genetically defined animal model displaying reduced PTEN expression, achieved by the conditional deletion of Pten using the keratin promoter 14 CRE-lox system. This provided a specific genetic and environmentally defined animal model for HNSCC that resulted in the rapid development of oral-specific carcinomas. Under these experimental conditions, control mice did not develop HNSCC lesions. In contrast, most mice harboring Pten deficiency developed multiple SCC lesions in the lateral border and ventral part of the tongue and floor of the mouth, which are the preferred anatomic sites for human HNSCC. Overall, our study highlights the likely clinical relevance of reduced PTEN expression and/or inactivation in HNSCC progression, while the combined Pten deletion with exposure to tobacco carcinogens or their surrogates may provide a unique experimental model system to study novel molecular targeted treatments for HNSCC patients.

Downregulation of keratin 76 expression during oral carcinogenesis of human, hamster and mouse

Background

Keratins are structural marker proteins with tissue specific expression; however, recent reports indicate their involvement in cancer progression. Previous study from our lab revealed deregulation of many genes related to structural molecular integrity including KRT76. Here we evaluate the role of KRT76 downregulation in oral precancer and cancer development.

Methods

We evaluated KRT76 expression by qRT-PCR in normal and tumor tissues of the oral cavity. We also analyzed K76 expression by immunohistochemistry in normal, oral precancerous lesion (OPL), oral squamous cell carcinoma (OSCC) and in hamster model of oral carcinogenesis. Further, functional implication of KRT76 loss was confirmed using KRT76-knockout (KO) mice.

Results

We observed a strong association of reduced K76 expression with increased risk of OPL and OSCC development. The buccal epithelium of DMBA treated hamsters showed a similar trend. Oral cavity of KRT76-KO mice showed preneoplastic changes in the gingivobuccal epithelium while no pathological changes were observed in KRT76 negative tissues such as tongue.

Conclusion

The present study demonstrates loss of KRT76 in oral carcinogenesis. The KRT76-KO mice data underlines the potential of KRT76 being an early event although this loss is not sufficient to drive the development of oral cancers. Thus, future studies to investigate the contributing role of KRT76 in light of other tumor driving events are warranted.

Ron tyrosine kinase receptor synergises with EGFR to confer adverse features in head and neck squamous cell carcinoma

Background:

Although EGFR inhibitors have shown some success in the treatment of head and neck squamous cell carcinomas (HNSCCs), the results are not dramatic. Additional molecular targets are urgently needed. We previously showed that the loss of Ron receptor activity significantly slowed squamous tumour growth and progression in a murine model. Based on these data, we hypothesised that Ron expression confers an aggressive phenotype in HNSCCs.

Methods:

We prospectively collected and evaluated 154 snap-frozen, primary HNSCCs for Ron and EGFR expression/phosphorylation. Biomarker correlation with clinical, pathological and outcome data was performed. The biological responses of HNSCC cell lines to Ron knockdown, its activation and the biochemical interaction between Ron and EGFR were examined.

Results:

We discovered that 64.3% (99 out of 154) HNSCCs expressed Ron. The carcinomas expressed exclusively mature functional Ron, whereas the adjacent nonmalignant epithelium expressed predominantly nonfunctional Ron precursor. There was no significant association between Ron and sex, tumour differentiation, perineural/vascular invasion or staging. However, patients with Ron+HNSCC were significantly older and more likely to have oropharyngeal tumours. Ron+HNSCC also had significantly higher EGFR expression and correlated strongly with phosphorylated EGFR (pEGFR). Newly diagnosed HNSCC with either Ron/pEGFR or both had lower disease-free survival than those without Ron and pEGFR. Knocking down Ron in SCC9 cells significantly blunted their migratory response to not only the Ron ligand, MSP, but also EGF. Stimulation of Ron in SCC9 cells significantly augmented the growth effect of EGF; the synergistic effect of both growth factors in SCC9 cells was dependent on Ron expression. Activated Ron also interacted with and transactivated EGFR.

Conclusion:

Ron synergises with EGFR to confer certain adverse features in HNSCCs.

Oral premalignancy: the roles of early detection and chemoprevention

Premalignancy and chemoprevention studies in head and neck cancer typically focus on the oral cavity. Avoiding or cessation of alcohol and smoking, early detection of potentially malignant disorders or cancer, and early detection of recurrent and/or second primary tumor form the basis of prevention of oral cancer. Analysis of tissue prospectively collected in evaluation of retinoids for chemoprevention trials allowed identification of molecular biomarkers of risk to develop oral cancer, loss of heterozygosity being the most validated one. Improving risk assessment and identification of new targets for chemoprevention represent the main challenges in this field.

The molecular pathogenesis of head and neck squamous cell carcinoma

Squamous cell carcinoma of the head and neck (HNSCC) is a relatively common human cancer characterized by high morbidity, high mortality, and few therapeutic options outside of surgery, standard cytotoxic chemotherapy, and radiation. Although the most important risk factors are tobacco use and alcohol consumption, the disease is also linked to infection with high-risk types of human papilloma viruses (HPVs). Recent genetic analyses have yielded new insights into the molecular pathogenesis of this disease. Overall, while somatic activating mutations within classical oncogenes including PIK3CA and RAS occur in HNSCC, they are relatively uncommon. Instead genetic data point to a contribution of multiple tumor suppressor pathways, including p53, Rb/INK4/ARF, and Notch, in tumor initiation, progression, and maintenance. The increasingly refined knowledge of HNSCC genetics, combined with ever-more-sophisticated animal models and newer drug targeting strategies, should promote novel therapeutic approaches and improved disease outcomes.

Role of phosphatidylinositol-3-kinase pathway in head and neck squamous cell carcinoma

Activation of the phosphatidylinositol-3-kinase (PI3K) pathway is one of the most frequently observed molecular alterations in many human malignancies, including head and neck squamous cell carcinoma (HNSCC). A growing body of evidence demonstrates the prime importance of the PI3K pathway at each stage of tumorigenesis, that is, tumor initiation, progression, recurrence, and metastasis. Expectedly, targeting the PI3K pathway yields some promising results in both preclinical studies and clinical trials for certain cancer patients. However, there are still many questions that need to be answered, given the complexity of this pathway and the existence of its multiple feedback loops and interactions with other signaling pathways. In this paper, we will summarize recent advances in the understanding of the PI3K pathway role in human malignancies, with an emphasis on HNSCC, and discuss the clinical applications and future direction of this field.

Characterization of bone resorption in novel in vitro and in vivo models of oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most commonly diagnosed oral malignancy in humans and cats and frequently invades bone. The objective of this study was to determine if feline OSCC serves as a relevant model of human OSCC in terms of osteolytic behavior and expression of bone resorption agonists. Novel feline OSCC cell lines (SCCF2 and SCCF3) were derived from spontaneous carcinomas. Gene expression and osteolytic behavior were compared to an established feline OSCC cell line (SCCF1) and three human OSCC cell lines (UMSCC-12, A253 and SCC25). Interaction of OSCC with bone and murine pre-osteoblasts (MC3T3) was investigated using in vitro co-culture techniques. In vivo bioluminescent imaging, Faxitron radiography and microscopy were used to measure xenograft growth and bone invasion in nude mice. Human and feline OSCC expressing the highest levels of parathyroid hormone-related protein (PTHrP) were associated with in vitro and in vivo bone resorption and osteoclastogenesis. MC3T3 cells had increased receptor activator of nuclear factor κB ligand (RANKL) expression and reduced osteoprotegerin (OPG) expression in conditioned medium from bone-invasive SCCF2 cells compared to minimally bone invasive SCCF3 cells, which was partially reversed with a neutralizing anti-PTHrP antibody. Human and feline OSCC cells cultured in bone-conditioned medium had increased PTHrP secretion and proliferation. Feline OSCC-induced bone resorption was associated with tumor cell secretion of PTHrP and with increased RANKL:OPG expression ratio in mouse preosteoblasts. Bone-CM increased OSCC proliferation and secretion of PTHrP. The preclinical models of feline OSCC recapitulated the bone-invasive phenotype characteristic of spontaneous OSCC and will be useful to future preclinical and mechanistic studies of bone invasive behavior.

Comprehensive MicroRNA profiling for head and neck squamous cell carcinomas

PURPOSE

The objective of this study is to investigate the significance of microRNAs (miRNA) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

A global miRNA profiling was done on 51 formalin-fixed archival HNSCC samples using quantitative reverse transcription-PCR approach, correlated with patients' clinical parameters. Functional characterization of HNSCC-associated miRNAs was conducted on three HNSCC cell lines. Cell viability and proliferation were investigated using MTS and clonogenic assays, respectively; cell cycle analyses were assessed using flow cytometry.

RESULTS

Thirty-eight of the 117 (33%) consistently detected miRNAs were significantly differentially expressed between malignant versus normal tissues. Concordant with previous reports, overexpression of miR-21, miR-155, let-7i, and miR-142-3p and underexpression of miR-125b and miR-375 were detected. Upregulation of miR-423, miR-106b, miR-20a, and miR-16 as well as downregulation of miR-10a were newly observed. Exogenous overexpression of miR-375 in HNSCC cell lines reduced proliferation and clonogenicity and increased cells in sub-G(1). Similar cellular effects were observed in knockdown studies of the miR-106b-25 cluster but with accumulation of cells in G(1) arrest. No major difference was detected in miRNA profiles among laryngeal, oropharyngeal, or hypopharyngeal cancers. miR-451 was found to be the only significantly overexpressed miRNA by 4.7-fold between nonrelapsed and relapsed patients.

CONCLUSION

We have identified a group of aberrantly expressed miRNAs in HNSCC and showed that underexpression of miR-375 and overexpression of miR-106b-25 cluster might play oncogenic roles in this disease. Further detailed examinations of miRNAs will provide opportunities to dissect the complex molecular abnormalities driving HNSCC progression.

Smad4 loss in mice causes spontaneous head and neck cancer with increased genomic instability and inflammation

Smad4 is a central mediator of TGF-beta signaling, and its expression is downregulated or lost at the malignant stage in several cancer types. In this study, we found that Smad4 was frequently downregulated not only in human head and neck squamous cell carcinoma (HNSCC) malignant lesions, but also in grossly normal adjacent buccal mucosa. To gain insight into the importance of this observation, we generated mice in which Smad4 was deleted in head and neck epithelia (referred to herein as HN-Smad4-/- mice) and found that they developed spontaneous HNSCC. Interestingly, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited increased genomic instability, which correlated with downregulated expression and function of genes encoding proteins in the Fanconi anemia/Brca (Fanc/Brca) DNA repair pathway linked to HNSCC susceptibility in humans. Consistent with this, further analysis revealed a correlation between downregulation of Smad4 protein and downregulation of the Brca1 and Rad51 proteins in human HNSCC. In addition to the above changes in tumor epithelia, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited severe inflammation, which was associated with increased expression of TGF-beta1 and activated Smad3. We present what we believe to be the first single gene-knockout model for HNSCC, in which both HNSCC formation and invasion occurred as a result of Smad4 deletion. Our results reveal an intriguing connection between Smad4 and the Fanc/Brca pathway and highlight the impact of epithelial Smad4 loss on inflammation.

Smad4: gatekeeper gene in head and neck squamous cell carcinoma

Unchecked cell growth is a hallmark of cancer. During oncogenesis, cancerous cells become resistant to the TGF-beta signaling pathway that usually keeps cell growth in check. The role of a critical mediator of this pathway, Smad4, in head and neck squamous cell carcinoma (HNSCC) remains unclear. In this issue of the JCI, Bornstein and colleagues report that Smad4 expression is decreased in malignant HNSCC and, surprisingly, also in normal-appearing buccal mucosa adjacent to HNSCC (see the related article beginning on page 3408). They also show that targeted conditional deletion of Smad4 in the head and neck epithelium of mice is alone sufficient to initiate spontaneous HNSCC, in conjunction with DNA repair gene dysregulation, genetic instability, and inflammation. These findings point to a novel function for Smad4 as a guardian gene that maintains genomic stability.

CTIP2 expression in human head and neck squamous cell carcinoma is linked to poorly differentiated tumor status

Background

We have demonstrated earlier that CTIP2 is highly expressed in mouse skin during embryogenesis and in adulthood. CTIP2 mutant mice die at birth with epidermal differentiation defects and a compromised epidermal permeability barrier suggesting its role in skin development and/or homeostasis. CTIP2 has also been suggested to function as tumor suppressor in cells, and several reports have described a link between chromosomal rearrangements of CTIP2 and human T cell acute lymphoblast leukemia (T-ALL). The aim of the present study was to look into the pattern of CTIP2 expression in Head and Neck Squamous Cell Carcinoma (HNSCC).

Methodology/Principal Findings

In the present study, we analyzed CTIP2 expression in human HNSCC cell lines by western blotting, in paraffin embedded archival specimens by immunohistochemistry (IHC), and in cDNA samples of human HNSCC by qRT-PCR. Elevated levels of CTIP2 protein was detected in several HNSCC cell lines. CTIP2 staining was mainly detected in the basal layer of the head and neck normal epithelium. CTIP2 expression was found to be significantly elevated in HNSCC (p<0.01), and increase in CTIP2 expression was associated with poorly differentiated tumor status. Nuclear co-localization of CTIP2 protein and cancer stem cell (CSC) marker BMI1 was observed in most, if not all of the cells expressing BMI1 in moderately and poorly differentiated tumors.

Conclusions/Significance

We report for the first time expression of transcriptional regulator CTIP2 in normal human head and neck epithelia. A statistically significant increase in the expression of CTIP2 was detected in the poorly differentiated samples of the human head and neck tumors. Actual CTIP2, rather than the long form of CTIP2 (CTIP2_L) was found to be more relevant to the differentiation state of the tumors. Results demonstrated existence of distinct subsets of cancer cells, which express CTIP2 and underscores the use of CTIP2 and BMI1 co-labeling to distinguish tumor initiating cells or cancer stem cells (CSCs) from surrounding cancer cells.

Akt activation synergizes with Trp53 loss in oral epithelium to produce a novel mouse model for head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a common human neoplasia with poor prognosis and survival that frequently displays Akt overactivation. Here we show that mice displaying constitutive Akt activity (myrAkt) in combination with Trp53 loss in stratified epithelia develop oral cavity tumors that phenocopy human HNSCC. The myrAkt mice develop oral lesions, making it a possible model of human oral dysplasia. The malignant conversion of these lesions, which is hampered due to the induction of premature senescence, is achieved by the subsequent ablation of Trp53 gene in the same cells in vivo. Importantly, mouse oral tumors can be followed by in vivo imaging, show metastatic spreading to regional lymph nodes, and display activation of nuclear factor-kappaB and signal transducer and activator of transcription-3 pathways and decreased transforming growth factor-beta type II receptor expression, thus resembling human counterparts. In addition, malignant conversion is associated with increased number of putative tumor stem cells. These data identify activation of Akt and p53 loss as a major mechanism of oral tumorigenesis in vivo and suggest that blocking these signaling pathways could have therapeutic implications for the management of HNSCC.

Inhibition of Mammalian target of rapamycin by rapamycin causes the regression of carcinogen-induced skin tumor lesions

PURPOSE

The activation of Akt/mammalian target of rapamycin (mTOR) pathway represents a frequent event in squamous cell carcinoma (SCC) progression, thus raising the possibility of using specific mTOR inhibitors for the treatment of SCC patients. In this regard, blockade of mTOR with rapamycin prevents the growth of human head and neck SCC cells when xenotransplanted into immunodeficient mice. However, therapeutic responses in xenograft tumors are not always predictive of clinical anticancer activity.

EXPERIMENTAL DESIGN

As genetically defined and chemically induced animal cancer models often reflect better the complexity of the clinical setting, we used here a two-step chemical carcinogenesis model to explore the effectiveness of rapamycin for the treatment of skin SCC.

RESULTS

Rapamycin exerted a remarkable anticancer activity in this chemically induced cancer model, decreasing the tumor burden of mice harboring early and advanced tumor lesions, and even recurrent skin SCCs. Immunohistochemical studies on tumor biopsies and clustering analysis revealed that rapamycin causes the rapid decrease in the phosphorylation status of mTOR targets followed by the apoptotic death of cancer cells and the reduction in the growth and metabolic activity of the surviving ones, concomitant with a decrease in the population of cancer cells expressing mutant p53. This approach enabled investigating the relationship among molecular changes caused by mTOR inhibition, thus helping identify relevant biomarkers for monitoring the effectiveness of mTOR inhibition in the clinical setting.

CONCLUSIONS

Together, these findings provide a strong rationale for the early evaluation of mTOR inhibitors as a molecular targeted approach to treat SCC.

Establishment of a highly metastatic tongue squamous cell carcinoma cell line from New Zealand White rabbit

OBJECTIVE

Prior to this study, the widely used tongue squamous cell carcinoma cell lines could only initiate tumours in immunodeficient mice, which greatly delayed studies on immune function during carcinogenesis. This study established a new tongue squamous cell carcinoma cell line named 'RSCC-1', which can initiate tumours in both immunocompetent rabbits and immunodeficient nude mice and has high metastatic ability.

DESIGN

Primary tongue cancer was induced by DMBA and local mechanical stimulation in New Zealand White rabbits. The induced cancer was serially transplanted into homogeneous rabbits to establish transplanted models. At the same time, cancer samples were collected, cultured and passaged in vitro. Finally, a cell line named 'RSCC-1' was established. Its growth behaviour, cell cycle distribution and tumourigenicity in rabbits and nude mice were investigated.

RESULTS

RSCC-1 cells were cultured continuously in vitro for 19 months (165 passages). They contain between 54 and 196 chromosomes, with a modal number of 75. Tumourigenicity rates were 100% in both homogeneous rabbits and nude mice, with 20% lung metastasis and 50% cervical lymph node metastasis in homogeneous rabbits.

CONCLUSION

RSCC-1 is a poorly differentiated, highly malignant rabbit tongue squamous cell carcinoma cell line. Its behaviour in the inoculated animal model closely resembles human tongue cancer, and could metastasize to local lymph nodes and remote organs.