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

Direct Contact with Platelets Induces Podoplanin Expression and Invasion in Human Oral Squamous Cell Carcinoma Cells

Oral squamous cell carcinoma (OSCC) is mostly diagnosed at an advanced stage, with local and/or distal metastasis. Thus, locoregional and/or local control of the primary tumor is crucial for a better prognosis in patients with OSCC. Platelets have long been considered major players in cancer metastasis. Traditional antiplatelet agents, such as aspirin, are thought to be potential chemotherapeutics, but they need to be used with caution because of the increased bleeding risk. Podoplanin (PDPN)-expressing cancer cells can activate platelets and promote OSCC metastasis. However, the reciprocal effect of platelets on PDPN expression in OSCC has not been investigated. In this study, we found that direct contact with platelets upregulated PDPN and integrin β1 at the protein level and promoted invasiveness of human OSCC Ca9.22 cells that express low levels of PDPN. In another human OSCC HSC3 cell line that express PDPN at an abundant level, silencing of the PDPN gene reduced cell invasiveness. Analysis of the public database further supported the co-expression of PDPN and integrin β1 and their increased expression in metastatic tissues compared to normal and tumor tissues of the oral cavity. Taken together, these data suggest that PDPN is a potential target to regulate platelet-tumor interaction and metastasis for OSCC treatment, which can overcome the limitations of traditional antiplatelet drugs.

Up-Regulation of Tiam1 Promotes the Radioresistance of Laryngeal Squamous Cell Carcinoma Through Activation of the JNK/ATF-2 Signaling Pathway

Purpose

Our previous study has revealed that T-lymphoma invasion and metastasis-inducing factor 1 (Tiam1) overexpression are significantly associated with aggressive behavior and poor prognosis in patients with laryngeal squamous cell carcinoma (LSCC). However, the influence of Tiam1 in the radioresistance of LSCC and its mechanism have never been elucidated.

Materials and Methods

Western blotting was used to confirm the relationship between Tiam1 and the JNK/ATF-2 signaling pathway. To explore the specific functions of Tiam1 and JNK/ATF-2 signaling pathway on the proliferation and apoptosis of LSCC after radiation, cloning formation assay and flow cytometry were conducted in vitro, and the experiments on a xenograft mouse model and TUNEL assay were performed in vivo.

Results

Western blotting indicated that Tiam1 can regulate the JNK/ATF-2 signaling pathway through the influence of the activity of JNK and ATF-2. Up-regulation of Tiam1 could promote proliferation and inhibit apoptosis of LSCC after radiation both in vitro and in vivo. Moreover, the down-regulation of the JNK/ATF-2 signaling pathway reduced the radioresistance of LSCC caused by Tiam1 up-regulation.

Conclusion

These results suggest that the up-regulation of Tiam1 expression can promote the radioresistance of LSCC through activation of the JNK/ATF-2 signaling pathway.

Interferon-stimulated gene 15 modulates cell migration by interacting with Rac1 and contributes to lymph node metastasis of oral squamous cell carcinoma cells

In an effort to understand the underlying mechanisms of lymph node metastasis in oral squamous cell carcinoma (OSCC), through in vivo selection, LN1-1 cells were previously established from OEC-M1 cells and showed enhanced lymphangiogenesis and lymphatic metastasis capabilities. In the current study, we use a stable isotope labeling with amino acids in cell culture (SILAC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic platform to compare LN1-1 to OEC-M1 cells. Interferon-stimulated gene 15 (ISG15) was found highly expressed in LN1-1 cells. Immunohistochemical analysis and meta-analysis of publicly available microarray datasets revealed that the ISG15 level was increased in human OSCC tissues and associated with poor disease outcome. Knockdown of ISG15 had minimal effects on tumor growth but did decrease tumor lymphangiogenesis and lymphatic metastasis of LN1-1 cells. Consistent with the in vivo assay, ISG15 knockdown did not impair cell growth but diminished cell migration, invasion, and transendothelial migration in vitro. ISG15-induced cell migration was independent of ISGylation and associated with membrane protrusion. Ectopic expression of ISG15 increased Rac1 activity and knockdown of Rac1 impaired ISG15-enhanced migration. Furthermore, Rac1 colocalized with ISG15 to a region of membrane protrusion and ISG15 coimmunoprecipitated with Rac1, especially with the Rac1-GDP form. Importantly, as shown by proximity ligation assays, ISG15 and Rac1 physically interacted with each other. Our results indicated that ISG15 affects cell migration by interacting with Rac1 and regulating Rac1 activity and contributes to lymphatic metastasis in OSCC.

uPA/uPAR and SERPINE1 in head and neck cancer: role in tumor resistance, metastasis, prognosis and therapy

There is strong evidence supporting the role of the plasminogen activator system in head and neck squamous cell carcinoma (HNSCC), particularly of its uPA (urokinase plasminogen activator) / uPAR (urokinase plasminogen activator receptor) and SERPINE1 components. Overexpression of uPA/uPAR and SERPINE1 enhances tumor cell migration and invasion and plays a key role in metastasis development, conferring poor prognosis. The apparent paradox of uPA/uPAR and its inhibitor SERPINE1 producing similar effects is solved by the identification of SERPINE1 activated signaling pathways independent of uPA inhibition. Both uPA/uPAR and SERPINE1 are directly linked to the induction of epithelial-to-mesenchymal transition, the acquisition of stem cell properties and resistance to antitumor agents. The aim of this review is to provide insight on the deregulation of these proteins in all these processes.

We also summarize their potential value as prognostic biomarkers or potential drug targets in HNSCC patients. Concomitant overexpression of uPA/uPAR and SERPINE1 is associated with a higher risk of metastasis and could be used to identify patients that would benefit from an adjuvant treatment. In the future, the specific inhibitors of uPA/uPAR and SERPINE1, which are still under development, could be used to design new therapeutic strategies in HNSCCs.

p70S6K promotes IL-6-induced epithelial-mesenchymal transition and metastasis of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the fifth most common cancer worldwide and a common cause of cancer-related death, with a 5-year survival rate of less than 60%. IL-6 has been suggested to play an important role in cancer metastasis, but its mechanism in HNSCC has not been fully clarified. p70S6K has been reported to induce epithelial-mesenchymal transition (EMT) of ovarian cancer, but its role in HNSCC remains unknown. In this study, we found that p70S6K and IL-6 were upregulated in high-metastatic HNSCC cell lines that underwent EMT when compared to paired low-metastatic cell lines. Overexpression of p70S6K promoted EMT and migration of HNSCC cells, while downregulation of p70S6K attenuated IL-6-induced EMT and cell migration. Furthermore, IL-6-induced p70S6K activation was attenuated by inhibitors of the PI3K/Akt/mTOR, MAPK/ERK, and JAK/STAT3 signaling pathways, suggesting that it located downstream of these pathways. These findings suggest that p70S6K promotes IL-6-induced EMT and metastasis of HNSCC. Targeting p70S6K for HNSCC therapy may benefit patients through the inhibition of tumor growth, as well as metastasis.

Phosphorylation-mediated activation of LDHA promotes cancer cell invasion and tumour metastasis

Metastases remain the major cause of death from cancer. Recent molecular advances have highlighted the importance of metabolic alterations in cancer cells, including the Warburg effect that describes an increased glycolysis in cancer cells. However, how this altered metabolism contributes to tumour metastasis remains elusive. Here, we report that phosphorylation-induced activation of lactate dehydrogenase A (LDHA), an enzyme that catalyses the interconversion of pyruvate and lactate, promotes cancer cell invasion, anoikis resistance and tumour metastasis. We demonstrate that LDHA is phosphorylated at tyrosine 10 by upstream kinases, HER2 and Src. Targeting HER2 or Src attenuated LDH activity as well as invasive potential in head and neck cancer and breast cancer cells. Inhibition of LDH activity by small hairpin ribonucleic acid or expression of phospho-deficient LDHA Y10F sensitized the cancer cells to anoikis induction and resulted in attenuated cell invasion and elevated reactive oxygen species, whereas such phenotypes were reversed by its product lactate or antioxidant N-acetylcysteine, suggesting that Y10 phosphorylation-mediated LDHA activity promotes cancer cell invasion and anoikis resistance through redox homeostasis. In addition, LDHA knockdown or LDHA Y10F rescue expression in human cancer cells resulted in decreased tumour metastasis in xenograft mice. Furthermore, LDHA phosphorylation at Y10 positively correlated with progression of metastatic breast cancer in clinical patient tumour samples. Our findings demonstrate that LDHA phosphorylation and activation provide pro-invasive, anti-anoikis and pro-metastatic advantages to cancer cells, suggesting that Y10 phosphorylation of LDHA may represent a promising therapeutic target and a prognostic marker for metastatic human cancers.

Caveolin-1-negative head and neck squamous cell carcinoma primary tumors display increased epithelial to mesenchymal transition and prometastatic properties

Distant metastases arise in 20-30% of patients with squamous cell carcinoma of the head and neck (HNSCC) in the 2 years following treatment. Therapeutic options are limited and the outcome of the patients is poor. The identification of predictive biomarkers of patient at risk for distant metastasis and therapies are urgently needed. We previously identified a clinical subgroup, called "R1" characterized by high propensity for rapid distant metastasis. Here, we showed that "R1" patients do not or at very low level express caveolin-1 (Cav1). Low or no expression of Cav1 is of bad prognosis. Disappearance of Cav1 enables cells to undergo epithelial-mesenchymal transition (EMT). EMT is associated with enhanced migration and invasion. Our study uncovered a new target, α5β1 integrin. Targeting α5β1 integrins might not only prevent metastasis of HNSCC but also delay the development of the primary tumor by reducing tumor cell viability. Cav1 detection might be taken into consideration in the future in the clinic not only to identify patients at high risk of metastasis but also to select patient who might benefit from an anti-integrin therapy.

Insulin-like growth factor-independent insulin-like growth factor binding protein 3 promotes cell migration and lymph node metastasis of oral squamous cell carcinoma cells by requirement of integrin β1

Frequent metastasis to the cervical lymph nodes leads to poor survival of patients with oral squamous cell carcinoma (OSCC). To understand the underlying mechanisms of lymph node metastasis, two sublines were successfully isolated from cervical lymph nodes of nude mice through in vivo selection, and identified as originating from poorly metastatic parental cells. These two sublines specifically metastasized to cervical lymph nodes in 83% of mice, whereas OEC-M1 cells did not metastasize after injection into the oral cavity. After gene expression analysis, we identified insulin-like growth factor binding protein 3 (IGFBP3) as one of the significantly up-regulated genes in the sublines in comparison with their parental cells. Consistently, meta-analysis of the public microarray datasets and IGFBP3 immunohistochemical analysis revealed increased both levels of IGFBP3 mRNA and protein in human OSCC tissues when compared to normal oral or adjacent nontumorous tissues. Interestingly, the up-regulated IGFBP3 mRNA expression was significantly associated with OSCC patients with lymph node metastasis. IGFBP3 knockdown in the sublines impaired and ectopic IGFBP3 expression in the parental cells promoted migration, transendothelial migration and lymph node metastasis of orthotopic transplantation. Additionally, ectopic expression of IGFBP3 with an IGF-binding defect sustained the IGFBP3-enhanced biological functions. Results indicated that IGFBP3 regulates metastasis-related functions of OSCC cells through an IGF-independent mechanism. Furthermore, exogenous IGFBP3 was sufficient to induce cell motility and extracellular signal-regulated kinase (ERK) activation. The silencing of integrin β1 was able to impair exogenous IGFBP3-mediated migration and ERK phosphorylation, suggesting a critical role of integrin β1 in IGFBP3-enchanced functions.

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.

Increased expression of miR-93 is associated with poor prognosis in head and neck squamous cell carcinoma

MicroRNA-93-5p (miR-93) is a novel oncogenic microRNA (miRNA) and is elevated in diverse human malignancies. Aberrant expression and dysfunction of miR-93 are involved in many types of human tumours. However, the exact role of miR-93 remains unclear in head and neck squamous cell carcinoma (HNSCC). The objective of this study is to determine the expression pattern and clinical significance of miR-93 in HNSCC. MiR-93 expression levels in 103 primary HNSCC tissues and 16 corresponding non-cancerous epithelia were analysed by miRNA in situ hybridisation and correlated with the clinicopathological parameters and patient outcomes. Moreover, the expression of miR-93 was examined in four HNSCC cell lines and 17 pairs of HNSCC tissues and their corresponding adjacent tissues using quantitative real-time PCR (qRT-PCR). The miR-93 levels in HNSCC tissues and cell lines were significantly higher than those in the non-cancerous tissues. Notably, high miR-93 expression was significantly associated with T classification, lymph node metastasis and clinical stage. Kaplan-Meier survival analysis demonstrated that patients with high miR-93 expression had poorer overall survival than patients with low miR-93 expression. Multivariate Cox regression analysis revealed that miR-93 overexpression and lymph node metastasis were independent prognostic factors in patients with HNSCC. This study demonstrated that miR-93 expression was significantly increased in HNSCC tissue samples and cell lines and that miR-93 overexpression was associated with tumour progression, metastasis and poor prognosis in HNSCC patients. These results suggest that miR-93 may play a critical role in the initiation and progression of HNSCC, indicating that miR-93 may be a valuable marker for the prediction of metastasis and prognosis in HNSCC.

Melanoma cell lysate induces CCR7 expression and in vivo migration to draining lymph nodes of therapeutic human dendritic cells

We have previously reported a novel method for the production of tumour-antigen-presenting cells (referred to as TAPCells) that are currently being used in cancer therapy, using an allogeneic melanoma-derived cell lysate (referred to as TRIMEL) as an antigen provider and activation factor. It was recently demonstrated that TAPCell-based immunotherapy induces T-cell-mediated immune responses resulting in improved long-term survival of stage IV melanoma patients. Clinically, dendritic cell (DC) migration from injected sites to lymph nodes is an important requirement for an effective anti-tumour immunization. This mobilization of DCs is mainly driven by the C-C chemokine receptor type 7 (CCR7), which is up-regulated on mature DCs. Using flow cytometry and immunohistochemistry, we investigated if TRIMEL was capable of inducing the expression of the CCR7 on TAPCells and enhancing their migration in vitro, as well as their in vivo relocation to lymph nodes in an ectopic xenograft animal model. Our results confirmed that TRIMEL induces a phenotypic maturation and increases the expression of surface CCR7 on melanoma patient-derived DCs, and also on the monocytic/macrophage cell line THP-1. Moreover, in vitro assays showed that TRIMEL-stimulated DCs and THP-1 cells were capable of migrating specifically in the presence of the CCR7 ligand CCL19. Finally, we demonstrated that TAPCells could migrate in vivo from the injection site into the draining lymph nodes. This work contributes to an increased understanding of the biology of DCs produced ex vivo allowing the design of new strategies for effective DC-based vaccines for treating aggressive melanomas.

Invasive potential of melanoma cells correlates with the expression of MT1-MMP and regulated by modulating its association with motility receptors via N-glycosylation on the receptors

Matrix remodeling and invasion of basement membrane are the major determinants of malignant progression. Matrix degrading enzymes play a pivotal role in this process and have been shown to be regulated at multiple levels. Using high metastatic B16F10 and its invasive variant B16BL6 cells, we previously demonstrated that the expression of β1,6 branched N-oligosaccharides promotes cellular adhesion on different matrix components which in turn induces secretion of MMP9. The present investigations report that although the two cell lines do not differ in the expression of uPAR, expression of MT1-MMP is significantly higher on B16BL6 cells. Analysis of the transcripts of tissue inhibitors of matrix metalloproteinases (TIMPs) showed that expression of both TIMP1 and TIMP2 correlates negatively with the invasive potential of cells. CD44 and β1 integrin, the two important receptors involved in motility, were identified to carry β1,6 branched N-oligosaccharides in an invasive potential dependent manner. However, their glycosylation status did not appear to influence their surface expression. Although glycosylation on CD44 had no effect, that on β1 integrin significantly affected association of β1 integrin with MT1-MMP. The results thus demonstrate that the cancer cells use multiple mechanisms for degradation of matrix in a controlled manner to couple it with movement for effective invasion.

High MMP-21 expression in metastatic lymph nodes predicts unfavorable overall survival for oral squamous cell carcinoma patients with lymphatic metastasis

The aim of the present study was to examine the clinical significance of lymph node metastatic (LNM) foci in predicting the overall survival of oral squamous cell carcinoma (OSCC) patients with LNM. MMP-21 was screened based on the LNM animal model of OSCC. Then four proteins, matrix metalloproteinase (MMP)-2, MMP-21, vascular endothelial growth factor (VEGF)-C and VEGF receptor (VEGFR)-3 were examined by immunohistochemistry in 63 OSCC specimens, including the primary tumors (PTs) and the corresponding LNM foci. The expression levels between the PTs and LNM foci were compared by Wilcoxon paired test. Relationships between expression of the four proteins and patient overall survival were assessed by Kaplan-Meier based on the median of the labeling index. The Cox proportional hazards model was used to assess the relative hazard factors. MMP-21 and VEGF-C expression levels were higher in the LNM foci than levels in the PTs. Results showed that MMP-2 and VEGF-C expression levels in the PTs and MMP-2, MMP-21 and VEGF-C expression in the LNM foci correlated with the overall survival of the OSCC patients with lymphatic metastasis. MMP-21 expression level in the LNM foci was the most reliable predictor among all the tested factors. These results suggest that high MMP-21 expression in LNM foci can be used to predict survival in OSCC patients with LNM. Characteristics of LNM foci may be more reliable than PT characteristics in predicting the overall survival of OSCC patients with lymphatic metastasis.

Metadherin regulates metastasis of squamous cell carcinoma of the head and neck via AKT signalling pathway-mediated epithelial-mesenchymal transition

Our recent study suggested that metadherin (MTDH) is overexpressed in laryngeal squamous cell carcinoma. Here, we further investigated its role in promoting metastasis of squamous cell carcinoma of the head and neck (SCCHN). An immunohistochemistry analysis demonstrated that MTDH is elevated and positively correlated with metastasis in 189 primary SCCHN tissues. In vitro experiments demonstrated that MTDH overexpression enhanced the migratory and invasive ability of SCCHN cells. Moreover, MTDH induced epithelial-mesenchymal transition (EMT) by both regulating morphological changes and mediating the expression of the biomolecular makers E-cadherin and vimentin. In addition, MTDH mediated AKT activation, and all of the above effects were nearly completely blocked by the inhibition of AKT. Our results suggested that MTDH might promote the metastasis of SCCHN through AKT signalling pathway mediated-EMT.

The prometastatic ribosomal S6 kinase 2-cAMP response element-binding protein (RSK2-CREB) signaling pathway up-regulates the actin-binding protein fascin-1 to promote tumor metastasis

Metastasis is the leading cause of death in patients with breast, lung, and head and neck cancers. However, the molecular mechanisms underlying metastases in these cancers remain unclear. We found that the p90 ribosomal S6 kinase 2 (RSK2)-cAMP response element-binding protein (CREB) pathway is commonly activated in diverse metastatic human cancer cells, leading to up-regulation of a CREB transcription target Fascin-1. We also observed that the protein expression patterns of RSK2 and Fascin-1 correlate in primary human tumor tissue samples from head and neck squamous cell carcinoma patients. Moreover, knockdown of RSK2 disrupts filopodia formation and bundling in highly invasive cancer cells, leading to attenuated cancer cell invasion in vitro and tumor metastasis in vivo, whereas expression of Fascin-1 significantly rescues these phenotypes. Furthermore, targeting RSK2 with the small molecule RSK inhibitor FMK-MEA effectively attenuated the invasive and metastatic potential of cancer cells in vitro and in vivo, respectively. Taken together, our findings for the first time link RSK2-CREB signaling to filopodia formation and bundling through the up-regulation of Fascin-1, providing a proinvasive and prometastatic advantage to human cancers. Therefore, protein effectors of the RSK2-CREB-Fascin-1 pathway represent promising biomarkers and therapeutic targets in the clinical prognosis and treatment of metastatic human cancers.

A novel orthotopic mouse model of head and neck cancer and lymph node metastasis

Prognosis of head and neck squamous cell carcinoma (HNSCC) is largely determined by the extent of lymph node (LN) metastasis at diagnosis, and this appears to be controlled by cancer cell genetics. To examine the role of these genes in LN metastasis, we created a human-in-mouse orthotopic model of HNSCC and performed comparative microarray analysis of gene expression between populations of HNSCC cell lines derived before and after serial transplantation and in vivo metastasis in mice. Microarray analysis comparing the USC-HN3-GFP, USC-HN3-GFP-G1 and USC-HN3-GFP-G2 cell lines identified overexpression of genes implicated in epithelial-to- mesenchymal transition and the formation of cancer stem cells, including CAV-1, TLR-4 (Toll-like receptor 4), MMP-7 (matrix metalloproteinase 7), ALDH1A3, OCT-4 and TRIM-29. Ingenuity Pathway Analysis confirmed upregulation of respective gene signaling pathways in the USC-HN1-GFP-G2 cell line. Patient HNSCC samples from advanced stages overexpressed ALDH1A3, CAV-1 and MMP-7. Our results show that CAV-1, TLR-4, MMP-7, ALDH1A3, OCT-4 and TRIM-29 have increased expression in HNSCC cells selected for an enhanced metastatic phenotype and suggest that these genes may have an important role in the metastatic potential of HNSCC cells. Inhibition of these genes may therefore have prognostic and therapeutic utility in HNSCC.

High-level β1-integrin expression in a subpopulation of highly tumorigenic oral cancer cells

OBJECTIVES

The β1 integrin (CD29) is a putative marker for cancerous epithelial stem cells. Cancer stem cells are essential to drive tumor growth, recurrence, and metastasis. We investigated the role of β1-integrin expression in the development of malignant phenotypes of oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Immunostaining was used to analyze the expression levels of β1 integrins in different types of cell colonies and tumor spheres. The results of cell viability and migration assays with and without siRNA knockdown of β1-integrin expression were compared. Cells expressing β1 integrins were evaluated for their tumorigenicity in mice. The expression of β1 integrins in human specimens of oral cancers at different clinical stages was semiquantified based on immunohistochemical staining of the β1-integrin protein.

RESULTS

The expression level of β1 integrins in Meng-1 oral epidermoid carcinoma cells (OECM-1) cells was significantly higher in holoclonal colonies and tumor spheres compared to control cells. The knockdown of β1-integrin expression in OECM-1 cells reduced cell proliferation, migration, and tumor sphere formation. Beta-1 integrin (+) cells were more tumorigenic in the mouse xenograft model than β1 integrin (-) cells. In the human specimens, the expression level of the β1-integrin protein positively correlated with the clinical stage.

CONCLUSION

The expression of β1 integrin in OECM-1 cells is involved in the development of malignant phenotypes of OSCC.

CLINICAL RELEVANCE

Inhibitors for β1-integrin signaling may be suitable to become target-specific therapies for OSCC.

ECRG4 inhibits growth and invasiveness of squamous cell carcinoma of the head and neck in vitro and in vivo

ECRG4 has been shown to be a candidate tumor suppressor in several tumors, but its role in head and neck cancer remains poorly understood. In the present study, the effect of ECRG4 on head and neck cancer was investigated in vitro and in vivo. pFLAG-CMV-2-ECRG4 was stably transfected into squamous cell carcinoma of the head and neck (SCCHN) M2 cell lines to overexpress the ECRG4 gene. Real-time PCR and western blot analysis were performed to detect gene and protein expression, respectively. An MTT assay and flow cytometric analysis were used to detect the growth of M2 cells. Matrigel™ invasion and scratch assays were applied to observe the invasion and migration of the cells. A tumorigenicity assay was applied to test the tumor growth and cervical lymph node metastasis in vivo. Based on the data, pFLAG-CMV-2-ECRG4 significantly increased the expression of ECRG4 in the M2 cells. The constructed plasmid inhibited cell proliferation and promoted cell cycle arrest and apoptosis in the M2 cells. The growth rate and metastasis of the tumor cells in xenografts were suppressed following the overexpression of ECRG4 in nude mice. These data suggest that ECRG4 plays a significant role in the regulation of growth and metastasis in SCCHN, providing new clues for the diagnosis and therapy of SCCHN.

Biodistribution Study of Nanoparticle Encapsulated Photodynamic Therapy Drugs Using Multispectral Imaging

Photodynamictherapy (PDT) uses a drug called a photosensitizer that is excited by irradiation with a laser light of a particular wavelength, which generates reactive singlet oxygen that damages the tumor cells. The photosensitizer and light are inert; therefore, systemic toxicities are minimized in PDT. The synthesis of novel PDT drugs and the use of nanosized carriers for photosensitizers may improve the efficiency of the therapy and the delivery of the drug. In this study, we formulated two nanoparticles with and without a targeting ligand to encapsulate phthalocyanines 4 (Pc 4) molecule and compared their biodistributions. Metastatic human head and neck cancer cells (M4e) were transplanted into nude mice. After 2-3 weeks, the mice were injected with Pc 4, Pc 4 encapsulated into surface coated iron oxide (IO-Pc 4), and IO-Pc 4 conjugated with a fibronectin-mimetic peptide (FMP-IO-Pc 4) which binds specifically to integrin β1. The mice were imaged using a multispectral camera. Using multispectral images, a library of spectral signatures was created and the signal per pixel of each tumor was calculated, in a grayscale representation of the unmixed signal of each drug. An enhanced biodistribution of nanoparticle encapsulated PDT drugs compared to non-formulated Pc 4 was observed. Furthermore, specific targeted nanoparticles encapsulated Pc 4 has a quicker delivery time and accumulation in tumor tissue than the non-targeted nanoparticles. The nanoparticle-encapsulated PDT drug can have a variety of potential applications in cancer imaging and treatment.

The pivotal role of integrin β1 in metastasis of head and neck squamous cell carcinoma

PURPOSE

This study aimed to understand the prognostic value of integrin β1 expression in head and neck squamous cell carcinoma (HNSCC) and the mechanism underlying its association with metastatic HNSCC.

EXPERIMENTAL DESIGN

Archival HNSCC tissues including 99 nonmetastatic primary tumors and 101 metastatic primary tumors were examined for the association of integrin β1 expression with metastasis and disease prognosis by appropriate statistical methods. Fluorescence-activated cell sorting was used to separate the integrin β1(high/+) cell population from the integrin β1(low/-) population in HNSCC cell lines. These two populations and integrin β1 shRNA knockdown HNSCC cells were examined for the effect of integrin β1 on invasion in vitro and on lymph node and lung metastases in a xenograft mouse model. Expression and activation of matrix metalloproteinases (MMP) were examined by zymography.

RESULTS

Statistical analysis showed that integrin β1 expression was significantly higher in the metastatic primary tumors than in the nonmetastatic tumors (42.6% vs. 24.8%, P < 0.0001 and P < 0.0001 by univariate and multivariate analyses, respectively). In patients with lymph node metastasis, integrin β1 expression was inversely correlated with overall survival (P = 0.035). The integrin β1 knockdown or integrin β1(low/-) HNSCC cells showed a significant reduction in lymph node and lung metastases in vivo (P < 0.001 and P < 0.05, respectively). Significantly reduced Matrigel invasion capability was also found in integrin β1 knockdown or integrin β1(low/-) HNSCC cells (P < 0.01). Finally, zymography results showed integrin β1-affected HNSCC invasion by regulating MMP-2 activation.

CONCLUSION

These findings indicate that integrin β1 has a major impact on HNSCC prognosis through its regulation of metastasis.

Black tea polyphenols reverse epithelial-to-mesenchymal transition and suppress cancer invasion and proteases in human oral cancer cells

Epithelial-to-mesenchymal transition (EMT) in cancer cells is considered to be a prerequisite for acquiring invasive/migratory phenotype and subsequent metastasis. This study provides molecular evidence associated with the antimetastatic effect of black tea polyphenol extracts (BTE), which contain polyphenols including gallic acid, gallocatechin, catechin, epigallocatechin-3-gallate, epicatechin-3-gallate, and theaflavin 3,3'-digallate, in an an oral squamous cell culture system by showing a nearly complete inhibition on the invasion (p < 0.001) of SCC-4 cells via reduced activities of MMP-2 (p < 0.001) and u-PA (p < 0.001). Immunoblot was performed to find that BTE could induce up-regulation of epithelial markers such as E-cadherin and inhibit mesenchymal markers such as snail-1 and vimentin. BTE inhibited p-FAK and p-paxillin, indicating the anti-EMT effect of BTE in oral squamous cell carcinoma. BTE was evidenced by its inhibition of the tumor growth of SCC-4 cells via cancer cell xenografted nude mice mode. These results suggested that BTE could reduce invasion by reversing EMT in human oral cancer cells.

Overexpression of Smad proteins, especially Smad7, in oral epithelial dysplasias

OBJECTIVE

Transforming growth factor β, via membrane-bound receptors and downstream Smad2-4, 7, can modulate tumorigenesis. Smad2 and Smad3 heterodimerize with Smad4, and the complex migrates to the nucleus to regulate the expression of target genes. Smad7 is a key negative regulator of this signaling pathway. This study aimed to examine Smad2-4, 7 expression and phosphorylated Smad2-3 (p-Smad2-3) in oral epithelial dysplasia and compared it with normal oral mucosa, hyperkeratosis/epithelial hyperplasia and squamous cell carcinoma (SCC).

MATERIALS AND METHODS

Immunohistochemical staining of Smad2-4, 7 and p-Smad2-3, was performed for 75 samples of human oral mucosa, including hyperkeratosis/epithelial hyperplasia (n = 20), mild epithelial dysplasia (n = 11), moderate to severe epithelial dysplasia (n = 11), and SCC (n = 43). Normal buccal mucosa samples (n = 9) were also included.

RESULTS

A significant increase in Smad7 expression was observed in the ascending order of samples of normal oral mucosa, hyperkeratosis/epithelial hyperplasia/mild oral epithelial dysplasia, moderate to severe oral epithelial dysplasia, and well-differentiated oral SCC/moderately to poorly differentiated oral SCC. Additionally, significant increases in Smad7 expression were noted as compared with expression of Smad2-4 and p-Smad2-3 in lesions of hyperkeratosis/epithelial hyperplasia, mild oral epithelial dysplasia, moderate to severe oral epithelial dysplasia, well-differentiated oral SCC, and moderately to poorly differentiated oral SCC.

CONCLUSIONS

Our results indicate that Smad proteins, particularly Smad7, in oral epithelial dysplasia and SCC could contribute to the attenuation of Smads anti-proliferative signaling in cancer development.

CLINICAL RELEVANCE

Smad7 could be a marker for risk of malignant transformation of oral epithelial dysplasia.

Downregulation of IRS-1 promotes metastasis of head and neck squamous cell carcinoma

Lymph node metastasis is responsible for the high morbidity of head and neck squamous cell carcinoma (HNSCC). To date, the role of insulin receptor substrate 1 (IRS-1) in tumorigenesis and metastasis of head and neck cancer has not been elucidated. In this study, we found a negative correlation of IRS-1 expression with tumor metastasis both in human tissue samples and in cell lines. Furthermore, we found that knockdown of IRS-1 expression enhanced cell invasive potency and induced EMT in parallel with upregulation of miR-9 expression. We propose that IRS-1 suppresses metastasis of head and neck cancer possibly through miR-9.

Selective inhibition of nuclear factor-κB by nuclear factor-κB essential modulator-binding domain peptide suppresses the metastasis of highly metastatic oral squamous cell carcinoma

Nuclear factor-κB (NF-κB) activation contributes to the development of metastasis, thus leading to a poor prognosis in many cancers, including OSCC. However, little in vivo experimental data are available about the effects of NF-κB inhibition on OSCC metastasis. OSCC sublines were established from a GFP-expressing parental cell line, GSAS, and designated GSAS/N3 and N5 according to the in vivo passage number after cervical lymph node metastasis by a serial orthotopic transplantation model. In vitro migration and invasion were assessed in these cells, and the NF-κB activities and expression of NF-κB-regulated metastasis-related molecules were also examined. In in vivo experiments, the metastasis and survival of tumor-engrafted mice were monitored. Furthermore, the effects of a selective NF-κB inhibitor, NEMO-binding domain (NBD) peptide, on metastasis in GSAS/N5-engrafted mice were assessed, and engrafted tongue tumors were immunohistochemically examined. Highly metastatic GSAS/N3 and N5 cells showed an enhanced NF-κB activity, thus contributing to increased migration, invasion, and a poor prognosis compared with the parent cells. Furthermore, the expression levels of NF-κB-regulated metastasis-related molecules, such as fibronectin, β1 integrin, MMP-1, -2, -9, and -14, and VEGF-C, were upregulated in the highly metastatic cells. The NBD peptide suppressed metastasis and tongue tumor growth in GSAS/N5-inoculated mice, and was accompanied by the downregulation of the NF-κB-regulated metastasis-related molecules in engrafted tongue tumors. Our results suggest that the selective inhibition of NF-κB activation by NBD peptide may provide an effective approach for the treatment of highly metastatic OSCC.

Analysis of transcriptional factors and regulation networks in laryngeal squamous cell carcinoma patients with lymph node metastasis

The present study was to identify and quantitate differentially expressed proteins in laryngeal squamous cell carcinoma (LSCC) tissues with or without lymph node metastasis and to explore transcriptional factors and regulation networks associated with the process. Tissue specimens were taken from 20 patients with LSCC, including 10 cases of LSCC without metastasis LSCC (N0) and 10 cases of LSCC with metastasis LSCC (Nx). Among the 643 unique proteins identified by using iTRAQ labeling and quantitative proteomic technology, 389 proteins showed an abundance change in LSCC (Nx) as compared to LSCC (N0). Cytoskeleton remodeling, cell adhesion, and immune response activation were found to be the main processes in LSCC metastasis. The construction of transcription regulation networks identified key transcription regulators for lymph node metastasis of LSCC, including Sp1, c-myc, and p53, which may affect LSCC metastasis through the epithelial-mesenchymal transition. Furthermore, our results suggest that ubiquitination may be a critical factor in the networks. The present study provides insights into transcriptional factors and regulation networks involved in LSCC metastasis, which may lead to new strategies for treatment of LSCC metastasis.

Downregulation of EphA2 expression suppresses the growth and metastasis in squamous-cell carcinoma of the head and neck in vitro and in vivo

PURPOSE

Our previous study has revealed that EphA2 overexpression is significantly associated with aggressive behavior and poor prognosis in patients with squamous-cell carcinoma of the head and neck (SCCHN). However, the function of EphA2 in tumorigenesis and cervical lymph node metastasis of SCCHN has never been elucidated in vivo.

METHODS

EphA2 was knocked down in SCCHN cell lines. CCK-8 assays, fluorescence-activated cell sorting analysis, invasion and migration assays were performed in vitro. In vivo tumorigenicity assays were performed, and the impact on cervical lymph node metastasis was evaluated.

RESULTS

The present investigation demonstrated that suppression of EphA2 resulted in a significant inhibition of proliferation, migration, invasion of SCCHN cells in vitro and markedly diminished their tumorigenicity and lymph node metastasis in vivo.

CONCLUSIONS

These results suggest that EphA2 plays a critical role in SCCHN growth and metastasis and may be a promising therapeutic target to prevent the progression of SCCHN.

On-chip integrated labelling, transport and detection of tumour cells

Microflow cytometry represents a promising tool for the investigation of diagnostic and prognostic cellular cancer markers, particularly if integrated within a device that allows primary cells to be freshly isolated from the solid tumour biopsies that more accurately reflect patient-specific in vivo tissue microenvironments at the time of staining. However, current tissue processing techniques involve several sequential stages with concomitant cell losses, and as such are inappropriate for use with small biopsies. Accordingly, we present a simple method for combined antibody-labelling and dissociation of heterogeneous cells from a tumour mass, which reduces the number of processing steps. Perfusion of ex vivo tissue at 4°C with antibodies and enzymes slows cellular activity while allowing sufficient time for the diffusion of minimally active enzymes. In situ antibody-labelled cells are then dissociated at 37°C from the tumour mass, whereupon hydrogel-filled channels allow the release of relatively low cell numbers (<1000) into a biomimetic microenvironment. This novel approach to sample processing is then further integrated with hydrogel-based electrokinetic transport of the freshly liberated fluorescent cells for downstream detection. It is anticipated that this integrated microfluidic methodology will have wide-ranging biomedical and clinical applications.

TGF-β1 regulates the invasive and metastatic potential of mucoepidermoid carcinoma cells

BACKGROUND

Patients with mucoepidermoid carcinoma exhibit poor long-term prognosis because of the lack of therapeutic strategies that effectively block tumor progression. We have previously characterized the Ms cells as a highly metastatic mucoepidermoid carcinoma cell line that expresses high levels of transforming growth factor β1 (TGF-β1). Here, we studied the effect of suppressing TGF-β1 by RNA silencing on the invasive and metastatic potential of mucoepidermoid carcinoma.

METHODS

Cell motility, substratum adhesion, and transmembrane invasion were estimated by migration, matrigel adhesion, and matrigel invasion assay. Matrix metalloproteinase (MMP)-2 and MMP-9 activity were determined using gelatin gel zymography. Balb/c nu/nu nude mice lung metastatic model was used to test the metastatic ability of the Ms cells. Lung metastatic tumors were experimentally induced by mice tail vein inoculation of cancer cells.

RESULTS

TGF-β1 silencing inhibits cell motility, substratum adhesion, and transmembrane invasion. In vivo, a significant decrease in lung metastasis was observed when mice received tail vein injections of TGF-β1-silenced mucoepidermoid carcinoma cells, as compared to controls.

CONCLUSION

These results unveil a critical role for TGF-β1 in the progression of mucoepidermoid carcinomas and suggest that patients with this malignancy may benefit from therapeutic inhibition of the effectors of the TGF-β1 pathway.

Epigallocatechin-3 gallate inhibits invasion, epithelial-mesenchymal transition, and tumor growth in oral cancer cells

Epithelial to mesenchymal transition (EMT) is critical for the progression, invasion, and metastasis of epithelial tumorgenesis. Here, we provided molecular evidence associated with the antimetastatic effect of green tea polyphenol epigallocatechin-3 gallate (EGCG) in an oral squamous cell culture system by showing a nearly complete inhibition on the invasion (P < 0.001) of squamous cell carcinoma-9 (SCC-9) cells via a reduced expression of matrix metalloproteinase-2 (P < 0.001) and urokinasetype plasminogen activator (P < 0.001). EGCG exerted an inhibitory effect on cell migration (P < 0.001), motility (P < 0.001), spread, and adhesion (P < 0.001). We performed Western blot to find that EGCG inhibited p-focal adhesion kinase (p-FAK), p-Src, snail-1, and vimentin, indicating the anti-EMT effect of EGCG in oral squamous cell carcinoma. EGCG was also sufficient to inhibit phorbol-12-myristate-13-acetate-induced cell invasion and matrix metalloproteinase-9 expression, as evidenced by its inhibition on the tumor growth of SCC-9 cells in vivo via cancer cell xenografted nude mice mode. These results suggested that EGCG could reduce the invasion and cell growth of tumor cells, and such a characteristic may be of great value in developing a potential cancer therapy.

c-Jun NH2-terminal kinase-dependent upregulation of DR5 mediates cooperative induction of apoptosis by perifosine and TRAIL

BACKGROUND

Perifosine, an alkylphospholipid tested in phase II clinical trials, modulates the extrinsic apoptotic pathway and cooperates with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to augment apoptosis. The current study focuses on revealing the mechanisms by which perifosine enhances TRAIL-induced apoptosis.

RESULTS

The combination of perifosine and TRAIL was more active than each single agent alone in inducing apoptosis of head and neck squamous cell carcinoma cells and inhibiting the growth of xenografts. Interestingly, perifosine primarily increased cell surface levels of DR5 although it elevated the expression of both DR4 and DR5. Blockade of DR5, but not DR4 upregulation, via small interfering RNA (siRNA) inhibited perifosine/TRAIL-induced apoptosis. Perifosine increased phosphorylated c-Jun NH2-terminal kinase (JNK) and c-Jun levels, which were paralleled with DR4 and DR5 induction. However, only DR5 upregulaiton induced by perifosine could be abrogated by both the JNK inhibitor SP600125 and JNK siRNA. The antioxidants, N-acetylcysteine and glutathione, but not vitamin C or tiron, inhibited perifosine-induced elevation of p-c-Jun, DR4 and DR5. Moreover, no increased production of reactive oxygen species was detected in perifosine-treated cells although reduced levels of intracellular GSH were measured.

CONCLUSIONS

DR5 induction plays a critical role in mediating perifosine/TRAIL-induced apoptosis. Perifosine induces DR5 expression through a JNK-dependent mechanism independent of reactive oxygen species.

Clinical significance of EphA2 expression in squamous-cell carcinoma of the head and neck

PURPOSE

EphA2 receptor tyrosine kinase is frequently overexpressed and functionally altered in a variety of human cancers. The study aimed to assess EphA2 expression and to explore its roles in squamous-cell carcinoma of the head and neck (SCCHN).

METHODS

EphA2 expression in 98 primary SCCHN tissue specimens was analyzed by immunohistochemistry and correlated with clinicopathological parameters. Additionally, 13 paired SCCHN tissues and 6 SCCHN cell lines were evaluated for EphA2 expression by RT-PCR and immunoblotting.

RESULTS

EphA2 overexpressed in SCCHN tissues and SCCHN cell lines. More importantly, high EphA2 expression was significantly associated with tumor site, T classification, clinical stage, recurrence, and lymph node metastasis, respectively. Patients with high EphA2 expression had both poorer disease-free survival and overall survival than patients with low EphA2 expression. Multivariate Cox regression analysis revealed that EphA2 overexpression was an independent prognostic factor for patients with SCCHN.

CONCLUSIONS

These findings suggested that EphA2 may contribute to SCCHN progression and represent a novel prognostic indicator for patients with SCCHN.

Characterization of side populations in HNSCC: highly invasive, chemoresistant and abnormal Wnt signaling

Side Population (SP) cells, a subset of Hoechst-low cells, are enriched with stem cells. Originally, SP cells were isolated from bone marrow but recently have been found in various solid tumors and cancer cell lines that are clonogenic in vitro and tumorigenic in vivo. In this study, SP cells from lymph node metastatic head and neck squamous cell carcinoma (HNSCC) cell lines were examined using flow cytometry and Hoechst 3342 efflux assay. We found that highly metastatic HNSCC cell lines M3a2 and M4e contained more SP cells compared to the low metastatic parental HNSCC cell line 686LN. SP cells in HNSCC were highly invasive in vitro and tumorigenic in vivo compared to non-SP cells. Furthermore, SP cells highly expressed ABCG2 and were chemoresistant to Bortezomib and etoposide. Importantly, we found that SP cells in HNSCC had abnormal activation of Wnt/beta-catenin signaling as compared to non-SP cells. Together, these findings indicate that SP cells might be a major driving force of head and neck tumor formation and metastasis. The Wnt/beta-catenin signaling pathway may be an important target for eliminating cancer stem cells in HNSCC.

Gypenosides inhibits migration and invasion of human oral cancer SAS cells through the inhibition of matrix metalloproteinase-2 -9 and urokinase-plasminogen by ERK1/2 and NF-kappa B signaling pathways

Gypenosides (Gyp), found in Gynostemma pentaphyllum Makino, has been used as a folk medicine in the Chinese population for centuries and is known to have diverse pharmacologic effects, including anti-proliferative and anti-cancer actions. However, the effects of Gyp on prevention from invasion and migration of oral cancer cells are still unsatisfactory. The purpose of this study was to investigate effects of Gyp treatment on migration and invasion of SAS human oral cancer cells. SAS cells were cultured in the presence of 90 and 180 μg/mL Gyp for 24 and 48 hours. Gyp induced cytotoxic effects and inhibited SAS cells migration and invasion in dose- and time-dependent response. Wound-healing assay and boyden chamber assay were carried out to investigate Gyp-inhibited migration and invasion of SAS cells. Gyp decreased the abundance of several proteins, including nuclear factor-kappa B (NF-κB), cyclooxygenase-2 (COX-2), extracellular signal-regulated kinase 1/2 (ERK1/ 2), matrix metalloproteinase-9, -2 (MMP-9, -2), sevenless homolog (SOS), Ras, urokinase-type plasminogen activator (uPA), focal adhesion kinase (FAK) and RAC-alpha serine/threonine-protein kinase (Akt), in a time-dependent manner. In addition, Gyp decreased mRNA levels of MMP-2, MMP-7, MMP-9 but did not affect FAK and Rho A mRNA levels in SAS cells. These results provide evidences for the role of Gyp as a potent anti-metastatic agent, which can markedly inhibit the metastatic and invasive capacity of oral cancer cells. The inhibition of NF-κB and MMP-2, -7 and -9 signaling may be one of the mechanisms that is present in Gyp-inhibited cancer cell invasion and migration.

p90 ribosomal S6 kinase 2 promotes invasion and metastasis of human head and neck squamous cell carcinoma cells

Head and neck squamous cell carcinoma (HNSCC) is one of the most common types of human cancer and frequently metastasizes to LNs. Identifying metastasis-promoting factors is of immense clinical interest, as the prognosis for patients with even a single unilateral LN metastasis is extremely poor. Here, we report that p90 ribosomal S6 kinase 2 (RSK2) promotes human HNSCC cell invasion and metastasis. We determined that RSK2 was overexpressed and activated in highly invasive HNSCC cell lines compared with poorly invasive cell lines. Expression of RSK2 also correlated with metastatic progression in patients with HNSCC. Ectopic expression of RSK2 substantially enhanced the invasive capacity of HNSCC cells, while inhibition of RSK2 activity led to marked attenuation of invasion in vitro. Additionally, shRNA knockdown of RSK2 substantially reduced the invasive and metastatic potential of HNSCC cells in vitro and in vivo in a xenograft mouse model, respectively. Mechanistically, we determined that cAMP-responsive element-binding protein (CREB) and Hsp27 are phosphorylated and activated by RSK2 and are important for the RSK2-mediated invasive ability of HNSCC cells. Our findings suggest that RSK2 is involved in the prometastatic programming of HNSCC cells, through phosphorylation of proteins in a putative signaling network. Moreover, targeting RSK2 markedly attenuates in vitro invasion and in vivo metastasis of HNSCC cells, suggesting that RSK2 may represent a therapeutic target in the treatment of metastatic HNSCC.

Urinary-type plasminogen activator receptor/alpha 3 beta 1 integrin signaling, altered gene expression, and oral tumor progression

Oral squamous cell carcinoma (OSCC) has 50% 5-year survival rate, highlighting our limited understanding of the molecular events that contribute to disease progression. Microarray analyses of primary oral tumors have identified urinary-type plasminogen activator (uPA) and its receptor (uPAR) as key genes associated with human OSCC progression. The uPAR functions as both a proteinase receptor and an integrin ligand, modifying proteolysis, migration, integrin signaling, and cellular transcription. In the current study, uPAR expression levels were modified in OSCC cells followed by analysis of tumor growth in an in vivo orthotopic xenograft model and by transcriptional profiling. Overexpression of uPAR resulted in more infiltrative and less differentiated tumors, with ill-defined borders, cytologic atypia, and enhanced vascularity. Analysis of serial sections of both murine experimental tumors and microarrayed human OSCC showed a statistically significant association between uPAR and alpha(3) integrin colocalization in areas exhibiting extracellular signal-regulated kinase phosphorylation, suggesting that uPAR/alpha(3) integrin interaction potentiates extracellular signal-regulated kinase signaling in vivo. This is supported by cDNA microarray analysis, which showed differential expression of 148 genes (113 upregulated and 35 downregulated). Validation of gene expression changes in human OSCC using immunohistochemistry and quantitative real-time PCR showed increased growth factors, proteinases/inhibitors, and matrix components in uPAR-overexpressing tumors. Together, these results support a model wherein increased uPAR expression promotes alpha(3)beta(1) integrin association, resulting in increased mitogen-activated protein kinase signaling and transcriptional activation, leading to the formation of more aggressive tongue tumors. This combined approach has efficacy to identify additional biomarkers and/or prognostic indicators associated with aggressive human OSCC.

The role of constitutively activated STAT3 in B16 melanoma cells

Constitutively activated STAT3 is found frequently in a wide variety of human tumors, including melanoma. Moreover, constitutive STAT3 activation actively participates in tumor formation and progression, making STAT3 an attractive target for cancer therapy. We report here that in murine B16 melanoma cells, which have been previously shown to express constitutively active STAT3, the expression of a mutant form of STAT3 with the canonical tyrosine phosphorylation site (residue 705) mutated to phenylanaine has dominant-negative properties (STAT3-DN). STAT3-DN inhibits STAT3 tyrosine phosphorylation and STAT3-dependent DNA binding activity. Most importantly, STAT3-DN expression in B16 cells inhibits their invasiveness, as well as their melanogenesis by down-regulation of tyrosinase mRNA and protein expression as well as tyrosinase activity. These results suggest that STAT3 signaling plays a critical role in regulating melanoma behavior, and may represent a druggable target for melanoma therapy.

Anti-invasion and anti-tumor growth effect of doxycycline treatment for human oral squamous-cell carcinoma--in vitro and in vivo studies

Regional lymph node and distant organ metastasis of oral squamous-cell carcinoma (OSCC) has been associated with increased production of matrix metalloproteases (MMPs), and scientific data showed that doxycycline (Dox) could down-regulate the expression of MMPs. The objective of this study was to evaluate the effect of Dox on the expression of MMPs in vitro using the SCC-15 cell line and in vivo SCC-15 xenografted nude mice. SCC-15 cells maintained under distinct culture conditions expressed high levels of pro-MMP-2 and pro-MMP-9; however, as determined by zymography and Western blot analysis, Dox significantly reduced the production of pro-MMP-2 and pro-MMP-9 after 24h of treatment in a dose-dependent manner (2.5-40 microg/ml). Dox (10 microg/ml) decreased the expression of MMP-9 mRNA but did not alter the level of MMP-2 mRNA after 24h of treatment. In addition, this drug significantly inhibited the invasive and migration activities of SCC-15 cells in vitro (>75% inhibition at 10 microg/ml). On the other hand, daily administration of Dox (3mg/mice) restrained tumor growth in SCC-15 xenografted nude mice, with an inhibition rate of 85.6%. Compared with the control group (treated with normal saline), MMP-9 mRNA levels in the fresh tumor tissue decreased upon Dox treatment (P<0.01) while MMP-2 mRNA levels were unchanged. In conclusion, reduced expression of MMP-9 at the transcriptional level and MMP-2 at the post-transcriptional level caused by Dox was found to be associated with decreased invasion of oral SCC in vitro. Moreover, Dox exerted a significant suppressive effect on tumor growth in an in vivo nude mice model. Taken together, these results, to our knowledge, may first imply that Doxycycline has an adjuvant therapeutic effect on OSCC that is associated with inhibition of MMPs expression.

Metastasis-associated genes in oral squamous cell carcinoma and salivary adenoid cystic carcinoma: a differential DNA chip analysis between metastatic and nonmetastatic cell systems

Overall modes of differential gene expressions were analyzed between human oral/salivary carcinoma cell systems with (MK-1 and ACCM) and without (ZK-1/ZK-2 and ACC2/ACC3) metastatic potential by using micro-array analysis with cancer-associated DNA chips to determine the kinds of genes associated with metastatic behaviors. MK-1 and/or ACCM showed lower levels of gene expression in extracellular matrix-related molecules, such as collagen type IV, laminin, and adhesion molecules such as cadherin 2, but higher levels of genes which control extracellular matrix degradation, such as MMP 9, as well as cell growth and cycle, such as FGF7 and cyclin D1. Among the differentially expressed genes, similar protein expression tendencies for FGF7, laminin, cyclin D1, and collagen type IV were confirmed by immunofluorescence. Metastatic potentials of oral/salivary carcinoma cells seem to have resulted from certain combinations of over-/underexpression of the genes, which were responsible for extracellular matrix metabolism and cell growth in particular.

The cancer stem cell concept in progression of head and neck cancer

Human head and neck cancer (HNC) is a highly heterogeneous disease. Understanding the biology of HNC progression is necessary for the development of novel approaches to its prevention, early detection, and treatment. A current evolutional progression model has limitations in explaining the heterogeneity observed in a single tumor nest. Accumulating evidence supports the existence of cancer stem cells (CSCs) as small subpopulations in solid tumors, including HNC. These CSCs can be selected by appropriate cell surface markers, which are cancer type specific and have been confirmed by unique in vitro and in vivo assays. Selected CSC populations maintain a self-renewal capability and show aggressive behaviors, such as chemoresistance and metastasis. In addition to introducing the CSC concept in solid tumors, this short review summarizes current publications in HNC CSC and the prospective development and application of the CSC concept to HNC in the clinic.

Transcriptome profiling and network pathway analysis of genes associated with invasive phenotype in oral cancer

The aim of this study was to clarify relevant alterations of gene expression associated with the invasive phenotype of oral cancer. To reduce heterogeneity and to obtain data on genes specifically involved in invasive mechanism, we established a highly invasive ORC subline through in vitro Matrigel invasion method. Affymetrix microarrays were used for transcriptome profiling between parental and the highly invasive subline. Seventy-nine genes were differentially expressed at least 2-fold, including 38 up-regulated and 41 down-regulated. After analyzing the microarray data by MetaCore algorithm, a total of 12 regulatory pathways were found to be associated with invasive phenotype (p<0.001). Two functional pathways were most significant: the cell adhesion through extracellular matrix remodeling (p=4.964e-06), and MHC-class-I mediated antigen presentation (p=9.843e-05). To shed more light on the biological functions of invasiveness, two genes highly over-expressed in the invasive subline, Cyr61 and CD44 were further validated. RNAi knockdown of these two genes led to significant suppression of cell growth (32% and 31%, respectively at day 3), cell migration (45% and 96%, respectively at 24 h), and cell invasion (83% and 87%, respectively at day 3). These results suggested important roles of these genes in regulating invasive phenotype, and demonstrated the confidence of this study design in the search of invasive associated genes. The identified pathways associated with invasion mechanism may be novel targets for manipulation of the cancer behavior with consequences on treatment outcome.

Restoration of caveolin-1 expression suppresses growth and metastasis of head and neck squamous cell carcinoma

Caveolin-1 (Cav-1) plays an important role in modulating cellular signalling, but its role in metastasis is not well defined. A significant reduction in Cav-1 levels was detected in lymph node metastases as compared with primary tumour of head and neck squamous cell carcinoma (HNSCC) specimens (P<0.0001), confirming the downregulation of Cav-1 observed in a highly metastatic M4 cell lines derived from our orthotopic xenograft model. To investigate the function of Cav-1 in metastasis of HNSCC, we compared stable clones of M4 cells carrying human cav-1 cDNA (CavS) with cells expressing an empty vector (EV) in vitro and in the orthotopic xenograft model. Overexpression of Cav-1 suppressed growth of the CavS tumours compared with the EV tumours. The incidence of lung metastases was significantly lower in animals carrying CavS tumours than those with EV tumours (P=0.03). In vitro, CavS cells displayed reduced cell growth, invasion, and increased anoikis compared with EV cells. In CavS cells, Cav-1 formed complex with integrin beta1 and Src. Further application of integrin beta1 neutralising antibody or Src inhibitor PP2 to EV cells illustrated similar phenotypes as CavS cells, suggesting that Cav-1 may play an inhibitory role in tumorigenesis and lung metastasis through regulating integrin beta1- and Src-mediated cell-cell and cell-matrix interactions.

Differential bortezomib sensitivity in head and neck cancer lines corresponds to proteasome, nuclear factor-kappaB and activator protein-1 related mechanisms

Head and neck squamous cell carcinomas (HNSCC) exhibit constitutive activation of transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), which are modulated by the proteasome and promote resistance to cell death. HNSCC show variable sensitivity to the proteasome inhibitor bortezomib in vitro as well as in murine xenografts and patient tumors in vivo, and the mechanisms are not well understood. To address this question, the sensitivities of nine HNSCC cell lines to bortezomib were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, and the potential relationship between the sensitivity and bortezomib effects on biological processes was examined in HNSCC lines of differential bortezomib sensitivity. The most sensitive cell line (UM-SCC-11B) underwent cell death at 10(-9) mol/L in vitro and tumor regression at a maximally tolerated dose of bortezomib in a murine xenograft model. The differential sensitivity between UM-SCC-11A and UM-SCC-11B cells corresponded to differences in the extent of suppression of proteasome activity, ubiquitinated protein degradation, and NF-kappaB and AP-1 activation. Lower concentrations of bortezomib transiently increased NF-kappaB and sustained AP-1 activation in UM-SCC-11A cells. AP-1 reporter activity and cell density of UM-SCC-11A were suppressed when bortezomib was combined with c-Jun NH(2)-terminal kinase and p38 kinase pathways inhibitors. Thus, the differential sensitivities to bortezomib corresponded to dissimilar effects on the proteasome, NF-kappaB and AP-1 activities. Inhibition of c-Jun NH(2)-terminal kinase and p38 pathways blocked AP-1 activity and enhanced the antitumor effects. These findings revealed molecular mechanisms of bortezomib sensitivity and resistance, which are under development as biomarkers for clinical trials in patients with HNSCC.

Antimetastatic potentials of flavones on oral cancer cell via an inhibition of matrix-degrading proteases

OBJECTIVE

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck cancers with a poor prognosis due to frequent lymph node metastasis and local invasion. A growing number of in vitro studies have been conducted on the potential anticancer activity of flavonoids in various cancer cell lines. However, the antimetastatic activities of flavones, one subclass of flavonoids, in human oral squamous carcinoma SCC-4 cells have not been understood clearly.

DESIGN

The present study investigated the effect of four flavones on invasion and migration of SCC-4 cells to find that 7-hydroxyflavanone, 5,6,7-trihydroxyflavanone, and 4',5,7-trihydroxyflavanone exerted a dose-dependent inhibitory effect on the invasion and migration of SCC-4 cells.

RESULTS

Results from zymography and Western blot showed that flavones treatment may decrease the expressions of matrix metalloproteinase (MMP)-2, urokinase plasminogen activator (u-PA) in a concentration-dependent manner, together with altered expression levels of their endogenous inhibitors, which are tissue inhibitor of metalloproteinase-2 (TIMP-2) and plasminogen activator inhibitor-1 (PAI-1). Furthermore, an in vivo chorioallantoic membrane (CAM) intravasation assay was also treated and analysed to reveal the antimetastatic effect.

CONCLUSIONS

Our data suggest that 7-hydroxyflavanone, 5,6,7-trihydroxyflavanone, and 4',5,7-trihydroxyflavanone could be applicable to be a potential antimetastatic agent of SCC-4 cells.

CCR7 mediates inflammation-associated tumor progression

Chemokine receptor 7 (CCR7) mediates leukocyte adhesion and chemotaxis from peripheral sites of inflammation through lymphatic channels to secondary lymphoid organs. Aberrant CCR7 expression has been identified on certain tumor types and been linked to pro-survival and invasive pathways. In metastatic squamous cell carcinoma of the head and neck (SCCHN), we have described the selective upregulation of functional CCR7. In this manuscript, we review our understanding of CCR7-mediated signaling in metastatic SCCHN and provide evidence for its involvement in tumor survival, invasion, and metastasis. Autocrine and paracrine CCR7 activation appears to propagate the response to the CCR7 ligands CCL19 and CCL21, which are expressed by the lymphatic endothelium, secondary lymphoid tissues, and CCR7-positive tumor cells. Based on our recent findings, the induction of CCR7 expression and the sustenance of the autocrine signaling pathway have been shown to be regulated by NF-kappaB, similar to several types of immune cells. While extending these observations to metastatic SCCHN tumor cells, our studies highlight the importance of downstream NF-kappaB mediated CCR7 signals in the progression of SCCHN malignancy.

Preclinical models of regional lymph node tumor metastasis

Animal models have produced vital information regarding the mechanisms of RLN metastasis. Modern imaging and molecular techniques have made it clear that growing tumors secrete cytokines that induce invasion, angiogenesis, lymphangiogenesis, increased intratumoral IFV and IFP, increased fluid flow from the tumor to the surrounding tissues, increased lymphatic flow, an increase in the rate of entry of tumor cells into lymphatic capillaries, and an increased number of tumor cells reaching the RLN(s). This is important knowledge that will help direct translational research in human patients. We can look forward to continued improvement in the management of human tumors that metastasize to the RLNs.

Down-regulation of S100A2 in lymph node metastases of head and neck cancer

BACKGROUND

Our cDNA microarray analysis of squamous cell carcinoma of the head and neck (SCCHN) previously identified that S100A2 was down-regulated in highly metastatic 686LN-M3s cell lines established through in vivo selection using a metastatic xenograft mouse model. S100A2, a putative tumor suppressor, has been found to be down-regulated in several types of primary tumor as compared with the normal tissue. Only a few reports have explored its expression status and function in metastasis.

METHODS

To further confirm down-regulation of S100A2 in human metastasis, we examined S100A2 expression using immunohistochemical analysis of paraffin-embedded SCCHN tissues. The samples included primary SCCHN tumors (Tu-1) and involved lymph nodes (Met-1) from the same patients, and primary tumors in node-negative patients (Tu-2).

RESULTS

Most of these tumors expressed S100A2 but lymph node metastases showed a pattern of reduced staining for S100A2 compared with primary tumors. A similar expression pattern of S100A2 was also observed in several SCCHN cell lines by reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting. Particularly, S100A2 expression was lower in 686LN than Tu686 and hardly detectable in the metastatic derivatives 686LN-M3s. Further study of S100A2 promoter showed higher methylation intensity in these metastatic derivatives than in Tu686 and 686LN.

CONCLUSIONS

S100A2 was down-regulated in lymph node metastasis of SCCHN, suggesting that instead of being a putative tumor suppressor, S100A2 may play a role in the metastasis of SCCHN.

Understanding metastatic SCCHN cells from unique genotypes to phenotypes with the aid of an animal model and DNA microarray analysis

Metastasis of squamous cell carcinoma of the head and neck (SCCHN) is a significant health-care problem worldwide. The 5-year survival rate is less than 50% for patients with lymph node metastases. Understanding the molecular basis of SCCHN metastasis would facilitate the development of new therapeutic approaches to the disease. To identify proteins that mediate SCCHN metastasis, we established a SCCHN xenograft mouse model and performed in vivo selection from a SCCHN cell line using the model. In the fourth round of in vivo selection, significant incidences of metastases in lymph nodes (7/10) and lungs (6/10) were achieved from a derived SCCHN cell line as compared with its parental cells, 1/5 in lymph nodes and 0/5 in lungs. Metastatic cell lines from lymph node metastases and parental cell lines from non-metastatic xenograft tumors were subjected to DNA microarray analysis using an Affymetrix gene chip HG-U133A, followed by data mining studies. The identified metastasis-related genes were further evaluated for their encoding protein products and the metastatic cells were examined by biological analyses. DNA microarray analysis highlighted molecular features of the metastatic SCCHN cells, including alteration of expression of cell-cell adhesion proteins, epithelial cell markers, apoptosis and cell cycle regulatory molecules. Further biological analyses of phenotypic alterations revealed that the metastatic cells gained epithelial-mesenchymal transition (EMT) features and were more resistant to anoikis, which are two of the important phenotypes for metastatic SCCHN.