An orthotopic floor-of-mouth cancer model allows quantification of tumor invasion

Orthotopic and metastatic tumour models in preclinical cancer research

Mouse models of disease play a pivotal role at all stages of cancer drug development. Cell-line derived subcutaneous tumour models are predominant in early drug discovery, but there is growing recognition of the importance of the more complex orthotopic and metastatic tumour models for understanding both target biology in the correct tissue context, and the impact of the tumour microenvironment and the immune system in responses to treatment. The aim of this review is to highlight the value that orthotopic and metastatic models bring to the study of tumour biology and drug development while pointing out those models that are most likely to be encountered in the literature. Important developments in orthotopic models, such as the increasing use of early passage patient material (PDXs, organoids) and humanised mouse models are discussed, as these approaches have the potential to increase the predictive value of preclinical studies, and ultimately improve the success rate of anticancer drugs in clinical trials.

Vaccination with a nanoparticle E7 vaccine can prevent tumor recurrence following surgery in a human papillomavirus head and neck cancer model

High-risk human papillomavirus (HPV) encoding E6/E7-HPV oncogenes are responsible for a subgroup of head and neck squamous-cell carcinoma (HNSCC) and thus therapeutic E7-vaccines may be used to control HPV⁺HNSCC tumors. Herein we investigated the effects of an optimized nanoparticle-conjugated E7 long-peptide vaccine adjuvanted with CpG (NP-E7LP) in an orthotopic immunocompetent mouse model of HPV⁺HNSCC which is based on injection of HPV16 E6/E7-expressing mEERL95-cells into the submental space. In absence of surgery, vaccination performed before or after tumor-cell injection decreased tumor growth or prolonged mice survival only marginally, despite the high numbers of vaccine-induced circulating E7-specific IFN-γ-secreting CD8⁺ T-cells. This contrasts with the high-efficacy of NP-E7LP-vaccination reported in the genital and subcutaneous HPV16-E6/E7-expressing TC-1 models. Our data show that in a direct comparison, NP-E7LP-vaccination fully controlled TC-1, but not mEERL95, tumors subcutaneously growing in the flanks. Immune-cell infiltration was 10-fold higher in TC-1-tumors, than in mEERL95-tumors, suggesting that vaccine-induced CD8⁺ T-cells can only poorly infiltrate mEERL95-tumors. Indeed, immunofluorescence staining of orthotopic mEERL95-tumors showed that CD3⁺ T-cells are preferentially located peritumorally. However, when NP-E7LP-vaccination was performed after mEERL95-cell injection, but before resection of primary tumors, no postsurgical recurrence was observed and 100% of the mice survived until the experimental endpoint (day 70) in the NP-E7LP-vaccinated group. In contrast, we observed a 60% recurrence rate and only 35% survival in PBS-vaccinated mice. This suggests that removal of the primary tumor modified the tumor microenvironment, allowing a therapeutic effect of the vaccine-induced anti-tumor response. E7-vaccination combined with surgery may thus benefit patients with HPV⁺HNSCC.

G. B, Sebastian P, Somananthan T, Maliekal TT. TM1-IR680 peptide for assessment of surgical margin and lymph node metastasis in murine orthotopic model of oral cancer

Treatment outcome after surgical removal in oral carcinoma is poor due to inadequate methodologies available for marking surgical margins. Even though some methodologies for intraoperative margin assessment are under clinical and preclinical trials for other solid tumours, a promising modality for oral cancer surgery is not developed. Fluorescent-based optical imaging using Near Infrared (NIR) dyes tagged to tumour specific target will be an optimal tool for this purpose. One such target, Gastrin Releasing Peptide Receptor (GRPR) was selected for the study, and its binding peptide, TM1-IR680, was tested for its efficacy for surgical margin prediction in murine orthotopic model of oral cancer, derived from primary samples. Here, for the first time in a preclinical analysis, we show that the size and margin of oral cancer can be predicted, as revealed by 3D-imaging. Interestingly, the peptide was sensitive enough to detect lymph nodes that harboured dispersed tumour cells before colonization, which was impossible to identify by conventional histopathology. We recommend the use of TM1-NIR dyes alone or in combination with other technologies to improve the clinical outcome of oral cancer surgery.

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.

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.

Future directions and treatment strategies for head and neck squamous cell carcinomas

Head and neck cancer is a devastating disease that afflicts many individuals worldwide. Conventional therapies are successful in only a limited subgroup and often leave the patient with disfigurement and long lasting adverse effects on normal physiologic functions. The field is in dire need of new therapies. Oncolytic viral as well as targeted therapies have shown some success in other malignancies and are attractive for the treatment of head and neck cancer. Recently, it has been shown that a subset of head and neck cancers is human papillomavirus (HPV) positive and that this subset of cancers is biologically distinct and more sensitive to chemoradiation therapies although the underlying mechanism is unclear. However, chemoresistance remains a general problem. One candidate mediator of therapeutic response, which is of interest for the targeting of both HPV-positive and -negative tumors is the human DEK proto-oncogene. DEK is upregulated in numerous tumors including head and neck cancers regardless of their HPV status. Depletion of DEK in tumor cells in culture results in sensitivity to genotoxic agents, particularly in rapidly proliferating cells. This suggests that tumors with high DEK protein expression may be correlated with poor clinical response to clastogenic therapies. Targeting molecules such as DEK in combination with new and/or conventional therapies, holds promise for novel future therapeutics for head and neck cancer.

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 patterns in microRNA regulation of transcription factors during tumor metastasis

In spite of a large body of information about the upstream regulators of metastasis, a process that often plays a limiting factor in therapeutic outcome of cancer patients, the impact of regulatory microRNA patterns remains obscure. This review describes computational analysis of coordinated regulation of genes by di-directional regulation of microRNA and transcription factors that specifically regulate the process of metastasis. We discovered several unexpected modes of regulatory patterns between microRNAs and transcription factors. For example, we found a double positive feedback loop regulated by the hub transcription factor ZEB1 and miR-200 during epithelial-mesenchymal transition. This review further explains flow of information and how such components coordinate various adaptable controls of microRNAs and thus, contribute to regulation of transcription factors in context of cancer metastasis. Information described here provides a regulatory framework for future experimental analyses and discoveries of new insights into post-transcriptional gene regulation at the microRNA level in cancer metastasis.

A novel orthotopic mouse model of head and neck cancer with molecular imaging

OBJECTIVES/HYPOTHESIS

Our goal was to develop a noninvasive, dynamic imaging method that would further the understanding of head and neck cancer (HNC) tumor growth and local spreading. We developed a novel orthotopic mouse model of HNC with a stable cell line expressing a red fluorescent protein gene to compare a molecular imaging tumor quantification with traditional caliper measurement.

METHODS

An HNC-tdT stable cell line expressing the tdTomato gene was established, which were injected into the floor of the mouth of nude mice. Tumor growth was constantly monitored using molecular imaging for up to 35 days. The tumors were further evaluated by histologic examination.

RESULTS

Established tumors consistently expressed fluorescent signals that were successfully imaged by molecular imaging during the study. Initial tumor development was detected earlier than caliper measurement would allow. The fluorescent signal quantities of tumors detected by the imaging correlated with the tumor sizes measured by calipers.

CONCLUSIONS

This novel animal model represents an orthotopic human HNC model. The tumor can be detected earlier with molecular imaging than by conventional external caliper measurement. Unlike surgical measurement, the tumor can be quantified without disturbing the tumor environment. This model has significant potential for HNC oncologic research.

Zoledronic acid reduces bone loss and tumor growth in an orthotopic xenograft model of osteolytic oral squamous cell carcinoma

Squamous cell carcinoma (SCC) is the most common form of oral cancer. Destruction and invasion of mandibular and maxillary bone frequently occurs and contributes to morbidity and mortality. We hypothesized that the bisphosphonate drug zoledronic acid (ZOL) would inhibit tumor-induced osteolysis and reduce tumor growth and invasion in a murine xenograft model of bone-invasive oral SCC (OSCC) derived from an osteolytic feline OSCC. Luciferase-expressing OSCC cells (SCCF2Luc) were injected into the perimaxillary subgingiva of nude mice, which were then treated with 100 μg/kg ZOL or vehicle. ZOL treatment reduced tumor growth and prevented loss of bone volume and surface area but had no effect on tumor invasion. Effects on bone were associated with reduced osteolysis and increased periosteal new bone formation. ZOL-mediated inhibition of tumor-induced osteolysis was characterized by reduced numbers of tartrate-resistant acid phosphatase-positive osteoclasts at the tumor-bone interface, where it was associated with osteoclast vacuolar degeneration. The ratio of eroded to total bone surface was not affected by treatment, arguing that ZOL-mediated inhibition of osteolysis was independent of effects on osteoclast activation or initiation of bone resorption. In summary, our results establish that ZOL can reduce OSCC-induced osteolysis and may be valuable as an adjuvant therapy in OSCC to preserve mandibular and maxillary bone volume and function.

KITENIN represents a more aggressive phenotype in a murine model of oral cavity squamous carcinoma

Objective: To investigate the tumor invasiveness and early lung metastasis associated with KITENIN in a murine model of oral cavity squamous carcinoma.

Study Design: Cross-sectional study with planned data collection.

Setting: Department of Otolaryngology–Head and Neck Surgery, Medical Research Center for Gene Regulation, and Pathology, Chonnam National University Medical School and Hwasun Hospital.

Subjects and Methods: The cDNA of KITENIN and vector only were transfected into the SCC VII (murine squamous cell line) cells. The suspension of 5 × 105/mL viable KITENIN- or vector-transfected SCC VII cells was injected into the floor of the mouth of C3H/HeJ syngeneic mice, deep into the mylohyoid muscle via the intraoral approach. From the first to the sixth week after injection, tumor, lung, liver, and brain tissues were obtained.

Results: For all groups, the tumor invaded the superficial musculature of the floor of the mouth, the deep musculature of the floor of the mouth, the salivary glands, perineural tissue, bone, and skin, sequentially. Lung metastases developed multiple focal nodular patterns at first and then became more extensive. Earlier and more aggressive tumor invasion into the deep floor of the mouth musculature, salivary glands, perineural tissue, bone, and skin was observed in the KITENIN-transfected group compared to the vector-only group. An earlier and more extensive lung metastasis was observed in the KITENIN group.

Conclusion: An antisense KITENIN strategy might inhibit distant metastasis and the progression of head and neck squamous cell carcinoma.

Xenograft models of head and neck cancers

Head and neck cancers are among the most prevalent tumors in the world. Despite advances in the treatment of head and neck tumors, the survival of patients with these cancers has not markedly improved over the past several decades because of our inability to control and our poor understanding of the regional and distant spread of this disease. One of the factors contributing to our poor understanding may be the lack of reliable animal models of head and neck cancer metastasis. The earliest xenograft models in which human tumor cells were grown in immunosuppressed mice involved subcutaneous implantation of human head and neck cancer cell lines. Subcutaneous xenograft models have been popular because they are easy to establish, easy to manage, and lend themselves to ready quantitation of the tumor burden. More recently, orthotopic xenograft models, in which the tumor cells are implanted in the tumor site of origin, have been used with greater frequency in animal studies of head and neck cancers. Orthotopic xenograft models are advantageous for their ability to mimic local tumor growth and recapitulate the pathways of metastasis seen in human head and neck cancers. In addition, recent innovations in cell labeling techniques and small-animal imaging have enabled investigators to monitor the metastatic process and quantitate the growth and spread of orthopically implanted tumors. This review summarizes the progress in the development of murine xenograft models of head and neck cancers. We then discuss the advantages and disadvantages of each type of xenograft model. We also discuss the potential for these models to help elucidate the mechanisms of regional and distant metastasis, which could improve our ability to treat head and neck cancers.

An orthotopic floor-of-mouth model for locoregional growth and spread of human squamous cell carcinoma

The molecular investigation of head and neck cancer targets requires the utilization and optimization of established animal models to characterize the effects of gene transcription and protein expression on invasion and metastasis. Floor-of-the-mouth murine models have been developed to study tumor growth, invasion, and metastasis of murine squamous cell carcinoma (SCC) cells in immunocompetent mice and invasion and metastasis of human SCC cells in nude mice. However, there are tumor cell lines that do not produce tumors in mice, using standard techniques, thus reducing the utility of the model to study specific genetic or treatment conditions. Furthermore, these techniques require large tumor volumes raising the possibility of airway compromise. In this report, we detail significant modifications to the orthotopic floor-of-mouth murine model for human SCC to facilitate predictable growth of a large panel of University of Michigan SCC cell lines. Furthermore, we describe the use of bioluminescence and micro-computed tomography to monitor tumor growth and bony invasion.

Mouse models for human head and neck squamous cell carcinomas

Mouse models of human cancer play an important role in understanding the mechanisms of carcinogenesis and have accelerated the search for finding new molecular targets for cancer therapy. However, genetically engineered mouse models for head and neck squamous cell carcinoma (HNSCC) have only recently overcome major technical obstacles and begun to be explored. Here we review the current progress in the development of mouse models for human HNSCC, with emphasis on conditional transgenic and knockout mouse models. These new models faithfully recapitulate human HNSCC at both the pathologic and molecular levels. These animal models will not only be useful to define the roles of specific genes in HNSCC development and progression but will also provide a unique tool for developing and testing new therapeutic approaches.

Animal models in oral cancer research

Biologically and clinically relevant animal models are essential in investigation of the progression of diseases and the elaboration of diagnostic or therapeutic protocols. The several rodent models used for in vivo evaluation for oral cancer employ chemical, transplantation and genetic (knockout and transgenic) induction methods. These models are described together with their advantages and disadvantages. Their optimization and application in future research may improve the early detection and treatment of oral cancer.

Validation of ultrasonography to evaluate murine orthotopic oral cavity tumors

BACKGROUND

The murine orthotopic oral cavity tumor model allows evaluation of tumor growth and invasion. Currently, serial measurements of tissue growth are difficult to obtain since invasive procedures or animal sacrifice is necessary to evaluate tumor size. High-resolution ultrasound was evaluated as a noninvasive method to monitor tumor size in vivo.

METHODS

Sixteen immunodeficient mice, age 9 weeks, were injected transcervically with a human squamous cell carcinoma cell line into the tongue, and tumor volume was assessed by high-frequency ultrasound at 11 days. The animals were subsequently sacrificed and the tumors processed for histology. Tumor size was then calculated by caliper measurement in two dimensions.

RESULTS

Tumor dimensions obtained using ultrasound were found to significantly correlate with the histologic measurements (Spearman coefficient 0.90, p < 0.0001). Tumor dimensions were on average larger using ultrasound versus histologic measurements, although this was not significantly different than zero (95% confidence interval -13.96 to 62.37 mm2).

CONCLUSIONS

High-resolution ultrasound accurately measures tumor volume in the murine orthotopic oral cavity tumor model without sacrifice.

Role of squamous cell carcinoma antigen 1 expression in the invasive potential of head and neck squamous cell carcinoma

BACKGROUND

Serine proteases have important roles in tumor invasion and metastasis, and their inhibitors, serine protease inhibitors (serpins), are attractive targets for therapeutic strategies. On chromosome 18q21, there is a cluster of serpins: maspin, headpin, and squamous cell carcinoma antigen 1 (SCCA1)/SCCA2. Others and we have reported that the expression of these serpins is down regulated in head and neck squamous cell carcinoma (HNSCC) cells compared with normal squamous epithelial cells. In this study, we hypothesized that expression of SCCA1 is biologically disadvantageous to HNSCC cells.

METHODS

HNSCC cell lines were transfected with a mammalian expression vector with SCCA1 cDNA. In vitro proliferation, migration, or invasive potential (matrigel assay) of the transfectants were assayed. In addition, the in vivo growth and invasion was analyzed using the floor-of-mouth model of nude mice.

RESULTS

SCCA1 expression did not alter the in vitro growth rate of established HNSCC cells. However, SCCA1 expression significantly inhibited the in vitro invasion in matrigel assays. Furthermore, the in vivo growth and invasion in nude mice was also inhibited by SCCA1 expression.

CONCLUSIONS

Overexpression of SCCA1 in a HNSCC cell line inhibited its invasive potential. Loss of expression of the serpin SCCA1 may play a role in the malignant progression of HNSCC.

[Orthotopic murine model of head and neck squamous cell carcinoma]

PURPOSE

To develop a reliable animal model able to reproduce the behavior of head and neck squamous cell carcinomas (HNSCC). This model should facilitate our understanding of the molecular mechanisms of tumorigenicity and progression of these tumors, as well as the evaluation of novel therapies.

MATERIAL AND METHODS

20 nude mice nu/nu were injected intraorally and submucosally with a cell line derived from a human squamous cell carcinoma of the glottis.

RESULTS

90% of the mice developed locally agressive squamous cell carcinomas, invading the surrounding muscle fibers and into loose connective tissue structures. All the tumors showed perineural growth. Four (22%) of the 18 mice showed bone destruction, and 22% vascular invasion. Tumor cells invaded lymphatic vessels in all the specimens, and 100% of the mice developed regional lymph node metastases. None of the animals developed haematogenous metastases.

CONCLUSIONS

We present a metastasing model of HNSCC that resembles its human counterpart in many aspects.

Metastatic dissemination of human malignant oral keratinocyte cell lines following orthotopic transplantation reflects response to TGF-beta 1

This study examined the behaviour of nine human malignant oral keratinocyte cell lines following orthotopic transplantation to the floor of the mouth of athymic mice. Tumourigenesis, local spread, and metastatic dissemination were correlated with known cellular responses to transforming growth factor-beta 1 (TGF-beta 1). Six of nine cell lines were tumourigenic; four of these cell lines showed local spread which was characterized by vascular and bone invasion. Metastatic spread was uncommon, with only 9% of animals with primary tumours developing metastases and these were almost exclusively found in the regional lymph nodes; there was one pulmonary metastasis and no liver deposits. Tumour cell behaviour did not reflect the clinical stage of the original tumours. Cell lines that were resistant to TGF-beta 1-induced growth inhibition were more likely to form primary tumours, exhibit local spread, and metastasize than cells that were growth-inhibited by the ligand. The data demonstrate that tumourigenicity and tumour behaviour in this orthotopic mouse model varied between cell lines and that the pattern of local invasion and metastasis was similar to that seen in human oral cancer. Furthermore, cell lines that were refractory to the growth inhibitory effects of TGF-beta 1 behaved more aggressively than cells that underwent ligand-induced cell-cycle arrest.

Calcium-induced Matrix Metalloproteinase 9 Gene Expression Is Differentially Regulated by ERK1/2 and p38 MAPK in Oral Keratinocytes and Oral Squamous Cell Carcinoma

Matrix metalloproteinases (MMPs) play an important role in the invasive behavior of a number of cancers including oral squamous cell cancer (OSCC), and increased expression of MMP-9 is correlated with invasive and metastatic OSCC. Because calcium is an important regulator of keratinocyte function, the effect of modulating extracellular calcium on MMP-9 expression in OSCC cell lines was evaluated. Increasing extracellular calcium induced a dose-dependent increase in MMP-9 expression in immortalized normal and premalignant oral keratinocytes, but not in two highly invasive OSCC cell lines. Differential activation of MAPK signaling was also induced by calcium. p38 MAPK activity was down-regulated, whereas ERK1/2 activity was enhanced. Pharmacologic inhibition of p38 MAPK activity or expression of a catalytically inactive mutant of the upstream kinase MAPK kinase 3 (MKK3) increased the calcium induced MMP-9 gene expression, demonstrating that p38 MAPK activity negatively regulated this process. Interestingly blocking p38 MAPK activity enhanced ERK1/2 phosphorylation, suggesting reciprocal regulation between the ERK1/2 and p38 MAPK pathways. Together these data support a model wherein calcium-induced MMP-9 expression is differentially regulated by the ERK1/2 and p38 MAPK pathways in oral keratinocytes, and the data suggest that a loss of this regulatory mechanism accompanies malignant transformation of the oral epithelium.

HSulf-1 modulates HGF-mediated tumor cell invasion and signaling in head and neck squamous carcinoma

Recently, we cloned a novel sulfatase domain-containing downregulated gene, HSulf-1, which modulates heparin-binding growth factor signaling in ovarian cancer. Based on the pilot data showing the loss of HSulf-1 in head and neck squamous cell carcinoma cell lines (SCCHN), we sought to employ SCCHN as a model to define the role of HSulf-1 in the molecular regulation of tumorigenicity. Three SCCHN lines (012SCC, WMMSCC, and 015SCC) had no detectable HSulf-1 mRNA. Clonal lines of HSulf-1-expressing 012SCC attenuated the activation of ERK/mitogen-activated protein kinase (MAPK) signaling mediated by fibroblast growth factor (FGF-2) and both ERK/MAPK and Akt signaling mediated by hepatocyte growth factor (HGF). Consistent with this downregulation, phosphorylation of HGF receptor, c-Met, which is frequently overexpressed in SCCHN, was also attenuated in HSulf-1 clonal 012SCC cell lines. HGF markedly enhanced the motility and migration of vector-transfected cells in a transwell invasion chamber. However, HGF-mediated motility and invasion was attenuated in HSulf-1 clonal 012SCC cell lines. In addition, transfected cells displayed significant growth inhibition concomitant with a decrease in mitogenicity, as measured by thymidine incorporation and increased sensitivity to staurosporine- and cisplatin-induced apoptosis. These data suggest that HSulf-1 normally functions as a negative regulator in cell growth and loss of HSulf-1 in SCCHN potentiates growth factor signaling, enhances motility, invasiveness and inhibits stress-induced apoptosis, with a resulting increase in tumorigenicity.

Functional significance of MMP-2 and MMP-9 expression by human malignant oral keratinocyte cell lines

This study examined the expression of MMP-2 and MMP-9 in normal and human malignant oral keratinocytes. The expression of pro-MMP-2 and pro-MMP-9 was heterogeneous in the malignant cell lines. Normal oral keratinocytes expressed less pro-MMP-2 and more pro-MMP-9 than their malignant counterparts. Cells that expressed high levels of both MMP-2 and MMP-9 showed the greatest degree of invasion through Matrigel in vitro compared to cells with either low or variable levels of these enzymes; normal keratinocytes were non-invasive in these conditions. The degree to which the cells invaded through Matrigel was similar to their motility in the absence of Matrigel and was not influenced by the activation of the pro-enzymes or the inhibition of enzyme activity using a chemical inhibitor of gelatinases. Cells were transplanted orthotopically to athymic mice and demonstrated a variable capacity not only to form tumours at the site of inoculation but, also, to metastasise; normal oral keratinocytes were non-tumorigenic. There was no correlation between the expression of either MMP-2 or MMP-9 and the tumorigenic/metastatic phenotype. The results emphasise the limitations of correlating in vitro and in vivo assays of tumour cell behaviour and suggest that invasion/motility in vitro may be a distinct phenotype from tumorigenicity/metastasis in vivo.

Integrins in head and neck squamous cell carcinoma invasion

OBJECTIVE

To relate the invasive properties of different squamous cell cancer cell lines to the function and expression of the integrins.

STUDY DESIGN

A series of in vitro and in vivo experiments were designed to assess and compare integrin expression and function in two different head and neck squamous cell carcinoma cell lines.

METHODS

Invasive properties of two squamous cell carcinoma cell lines (UM-SCC-1 and JHU-022-SCC) were assessed using an in vitro artificial matrix assay as well as an in vivo system with orthotopically implanted tumor cells in mice. Whole cell and surface expression levels of integrin subunits (alpha2, alpha3, alpha5, alpha6, beta1, and beta4) were determined for each cell line using Western blot analysis and flow cytometry. We compared the ability of JHU-022-SCC and UM-SCC-1 cells to bind the extracellular matrix elements collagen IV, fibronectin, laminin 5, and laminin10 using an in vitro adhesion assay. Contributions of the different integrins to the adhesive properties were determined by selective antibody blocking of different subunits.

RESULTS

The UM-SCC-1 cell line is 50% more invasive in vitro and displays a greater propensity for perineural and lymphatic invasion in vivo. The UM-SCC-1 cells exhibited greater adherence to fibronectin than JHU-022-SCC cells. Alpha6 and beta4 expression is approximately twofold greater in the JHU-022-SCC cells. Alpha2, alpha3, and beta1 expression appears to be upregulated in UM-SCC-1 cells.

CONCLUSION

The UM-SCC-1 carcinoma cells are more invasive than JHU-022-SCC cells and may be related to differential expression of the integrins alpha6beta4, alpha3beta1, and alpha2beta1.

A lymph node metastatic mouse model reveals alterations of metastasis-related gene expression in metastatic human oral carcinoma sublines selected from a poorly metastatic parental cell line

BACKGROUND

Greater than 40% of patients with squamous cell carcinoma (SCC) of the oral cavity have lymph node metastasis at the time of diagnosis and a 5-year survival rate of less than 50%. Changes in gene expression that regulate metastasis of SCC to lymph nodes have not been identified.

METHODS

To study metastasis of oral SCC, highly metastatic oral SCC cell lines from a poorly metastatic oral SCC cell line were established by in vivo selection using a lymph node metastatic mouse model. The metastatic potential of the cells was studied using Matrigel invasion and cell surface protein adhesion assays. mRNA and protein encoded from metastasis-related genes in the metastatic derivatives and in their parental cells were examined using Northern blot analysis, immunoblotting, rapid analysis of gene expression, and a cDNA microarray technique.

RESULTS

The in vivo selected metastatic cells showed much higher Matrigel invasion capability than the parental cells. They also showed alterations in their adhesion properties to three cell surface proteins. Comparison of metastatic and nonmetastatic cells revealed several significant alterations in the expression of metastasis-related genes, including up-regulation of the urokinase-type plasminogen activator receptor, integrin beta1, membrane type 1-matrix metalloproteinase, and down-regulation of protease-activated receptor-1.

CONCLUSIONS

To the authors' knowledge, the current study is the first to report on gene expression analysis using a lymph node metastatic mouse model of human oral SCC. The data suggest that certain alterations of metastasis-related gene expression favor invasion of oral SCC and that cell surface proteins may play major roles in the metastasis of oral SCC to the lymph nodes.

Effect of herpes simplex virus type-1 on growth of oral cancer in an immunocompetent, orthotopic mouse model

Herpes simplex virus type-1 has been proposed as an agent for the treatment of oral cancer. Experiments were designed to test its effectiveness in an animal model that had a high level of similarity to the human disease. The mouse oral cancer cell line, AT-84, was implanted at an orthotopic site--the base of the tongue--into syngeneic, immunocompetent C3H mice. As expected, tumors invaded the musculature of the tongue, eroded the mandible, and metastasized to the lungs. To obtain a suitable strain of HSV-1 for therapy we screened 17 fresh clinical isolates and selected one that grew to a high titer in vitro. The mouse tumors were then treated by injection of HSV-1 at a titer of 10(9) plaque-forming units/milliliter. To prolong the anti-tumor effect some mice were also given cyclophosphamide, hydrocortisone, or a second injection of virus. To find the importance of bystander killing of tumor cells, some mice were given virus with ganciclovir. A reduction in tumor volume for a limited period was seen after treatment by HSV-1, and was increased by a second injection of virus or by the administration of cyclophosphamide. Ganciclovir negated the anti-tumor effect. Virus was detectable in the tumors for up to 7 days, and loss of virus coincided with the time at which growth of tumors resumed. The mortality of the mice varied up to around 50%. It appears that (1) a non-attenuated strain of HSV-1 can inhibit the growth of an aggressive malignant oral tumor, but only to a limited extent and (2) inhibition depends on the ability of the virus to replicate in the tumor. It is suggested that mutations in the virus will be necessary to prevent mortality, but must be designed carefully so as not to reduce the virulence of the virus.

Characterization of a spontaneously arising murine squamous cell carcinoma (SCC VII) as a prerequisite for head and neck cancer immunotherapy

BACKGROUND

To develop novel therapeutic approaches for patients with head and neck malignancies, poorly immunogenic murine models of squamous cell carcinoma (SCC) need to be defined.

METHODS

The phenotype, growth characteristics, and responsiveness to tumor-specific T-cell transfer of a spontaneously arising murine SCC (SCC VII) were characterized.

RESULTS

SCC VII expresses major histocompatibility complex (MHC) class I molecules yet is resistant to tumor-specific T-cell killing and relatively insensitive to killing mediated by lymphokine-activated killer (LAK) cells. Intradermal tumors are reproducibly established after vaccination of 5 x 10(4) cells, and systemic micrometastases are apparent after intravenous administration of 2.5 x 10(4) cells. Immunotherapy of 3-day lung metastases using tumor-specific T cells and systemic interleukin-2 (IL-2) was ineffective in reducing the number of metastases in vivo.

CONCLUSIONS

SCC VII is a poorly immunogenic murine squamous cell cancer, which represents an ideal model for preclinical testing of immunotherapeutic approaches for patients with SCC of the upper aerodigestive tract.

Expression of protease-activated receptor 1 in oral squamous cell carcinoma

Protease-activated receptor 1 (PAR-1) is a G-coupled membrane protein. In this study, we analyzed the expression of PAR-1 in oral squamous cell carcinomas (SCCs). PAR-1 was expressed in oral SCCs, but the level of PAR-1 protein was lower in non-metastatic cells than in metastatic cells. Thrombin stimulated the growth of metastatic cells, and both thrombin and thrombin receptor activation peptide (TRP) enhanced the adhesion of these cells to fibronectin, but had no effect on non-metastatic cells. Thrombin and TRP also induced matrix metalloproteinase (MMP)-2 and MMP-9 activities in metastatic cells. These results suggest that PAR-1 may contribute to the growth and invasive potential of oral SCC.

AlphaVbeta6 integrin promotes invasion of squamous carcinoma cells through up-regulation of matrix metalloproteinase-9

The integrin alphaVbeta6 is a fibronectin receptor, which is not detectable on normal epithelium but is neo-expressed in oral epithelial dysplasia and oral squamous-cell carcinoma (SCC), suggesting a role in promoting malignant behaviour and tumour progression. We used transfection and retroviral infection to create a panel of SCC cell lines expressing various levels of alphaVbeta6 to examine this possibility. We found that increased expression of alphaVbeta6 in malignant keratinocytes up-regulates MMP-9 and MMP-2 expression and promotes invasion in an MMP-9-dependent manner. Our results suggest a possible mechanism for the involvement of alphaVbeta6 in squamous carcinoma in vivo.