Potential molecular targets for inhibiting bone invasion by oral squamous cell carcinoma: a review of mechanisms

Osteoblasts are induced into cancer-associated osteoblasts to promote tumor progression in head and neck squamous cell carcinoma

Bone invasion by head and neck squamous cell carcinoma (HNSCC) significantly impacts tumor staging, treatment choice, prognosis, and quality of life. While HNSCC is known to cause osteolytic bone invasion, we found that specific HNSCC subtypes can induce osteogenic bone destruction at the tumor-bone interface. This destruction mode significantly correlated with reduced patient survival rates and increased neck lymph node metastasis. Further in vivo and in vitro experiments indicated that HNSCC cells triggered abnormal phenotypic changes in osteoblasts to remodel the tumor-bone microenvironment, facilitating tumor lymphatic metastasis. Through transcriptome analysis, we identified three genes-osteopontin (SPP1), chemokine (C-X-C motif) ligand 1 (CXCL1), and matrix metalloprotein (MMP)9 (MMP9) linked to a poorer prognosis. We discovered osteoblasts with abnormal phenotypes at the tumor-bone interface exhibiting high SPP1, MMP9, and CXCL1 expressions. Based on these characteristics, we identified this osteoblast subpopulation as "cancer-associated osteoblasts (CAOs)." HNSCC cells activated the TNF-α/NF-κB signaling pathway in osteoblasts, transforming them into "CAOs." These CAOs significantly contributed to the progression of tumor-induced bone invasion, facilitating cancer growth and metastasis. We first provided clinical data and in vivo and in vitro evidence that HNSCC cells can promote tumor progression by manipulating osteoblasts into "CAOs" in the bone invasion.

Clinical, Radiological, and Pathological Correlation of Mandibular Invasion in Carcinoma Bucco-alveolar Complex

A prospective cross-sectional study was conducted to correlate clinically, radiologically, and pathologically the mandibular invasion in carcinoma bucco-alveolar complex. All biopsy-proven oral cavity cancer cases (64 patients) were assessed clinically and radiologically for involvement of the mandible. Preoperative clinicoradiological findings were compared with postoperative histopathological findings. In our study, oral cancer was 4 times more prevalent in males as compared to females and clinical evaluation was found to be highly sensitive in predicting mandibular invasion. Orthopantomogram showed sensitivity of 66.6% and specificity of 100%. CT scan showed sensitivity of 100% and specificity of 46% whereas MRI showed sensitivity of 54.5% and a specificity of 96%. MRI correlates well with final histopathology in predicting size of tumor. Prevalence of bony invasion in carcinoma oral cavity was 18%. We noted an inverse relation with tumor differentiation and mandibular invasion, and none of the verrucous carcinoma lesions showed mandibular invasion. Association of clinical T and N staging with postoperative histopathology was found to be statistically significant. Despite recent advances in molecular biology, radiological techniques, and newer modalities like visual surgical planning, exact measurement of bone invasion is still challenging. At present, CT scan and MRI along with clinical evaluation are widely used to evaluate mandibular invasion in carcinoma oral cavity, and all these are complementary to each other. The recent progress in tissue engineering technologies and stem cell biology has significantly promoted the development of regenerative reconstruction of jawbone defects.

Systemic and Local Administration of a Dual-siRNA Complex Efficiently Inhibits Tumor Growth and Bone Invasion in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) accounts for nearly 90% of oral and oropharyngeal cancer cases and is characterized by high mortality and poor prognosis. RNA-based gene therapies have been developed as an emerging option for cancer treatment, but it has not been widely explored in OSCC. In this work, we developed an efficient siRNA cationic micelle DOTAP-mPEG-PCL (DMP) by self-assembling the cationic lipid DOTAP and monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) polymer. We tested the characteristics and transformation efficiency of this micelle and combined DMP with siRNA targeting STAT3 and TGF-β to evaluate the antitumor effect and bone invasion interfering in vitro and in vivo. The average size of the DMP was 28.27 ± 1.62 nm with an average zeta potential of 54.60 ± 0.29 mV. The DMP/siRNA complex showed high delivery efficiency, with rates of 97.47 ± 0.42% for HSC-3. In vitro, the DMP/siSTAT3 complex exhibited an obvious cell growth inhibition effect detected by MTT assay (an average cell viability of 25.1%) and clonogenic assay (an average inhibition rate of 51.9%). Besides, the supernatant from HSC-3 transfected by DMP/siTGF-β complexes was found to interfere with osteoclast differentiation in vitro. Irrespective of local or systemic administration, DMP/siSTAT3+siTGF-β showed antitumor effects and bone invasion inhibition in the OSCC mice mandibular invasion model according to tumor volume assays and Micro-CT scanning. The complex constructed by DMP cationic micelles and siSTAT3+siTGF-β represents a potential RNA-based gene therapy delivery system for OSCC.

Sclerostin Alters Tumor Cell Characteristics of Oral Squamous Cell Carcinoma and May Be a Key Player in Local Bone Invasion

Localized jawbone invasion is a milestone in the progression of oral squamous cell carcinoma (OSCC). The factors that promote this process are not well understood. Sclerostin is known to be involved in bone metabolism and there are preliminary reports of its involvement in bone tumors and bone metastasis. To identify a possible involvement of sclerostin in the bone invasion process of OSCC, sclerostin expression was analyzed in vitro in two different human OSCC tumor cell lines by quantitative real-time polymerase chain reaction (qRT-PCR), and the effect of recombinant human (rh)-sclerostin treatment on tumor cell capabilities was evaluated using proliferation, migration, and invasion assays. Undifferentiated human mesenchymal stem cells (hMSCs) were osteogenically differentiated and co-cultured with OSCC tumor cells to demonstrate potential interactions and migration characteristics. Sclerostin expression was evaluated in clinical cases by immunohistochemistry at the OSCC-jawbone interface in a cohort of 15 patients. Sclerostin expression was detected in both OSCC tumor cell lines in vitro and was also detected at the OSCC-jawbone interface in clinical cases. Tumor cell proliferation rate, migration and invasion ability were increased by rh-sclerostin treatment. The migration rate of tumor cells co-cultured with osteogenically differentiated hMSCs was increased. The results presented are the first data suggesting a possible involvement of sclerostin in the bone invasion process of OSCC, which deserves further investigation and may be a potential approach for drug-based tumor therapy.

Dual roles of cellular communication network factor 6 (CCN6) in the invasion and metastasis of oral cancer cells to bone via binding to BMP2 and RANKL

The acquisition of motility via epithelial-mesenchymal transition (EMT) and osteoclast induction are essential for the invasion and metastasis of oral squamous cell carcinoma (OSCC) to bone. However, the molecule suppressing both EMT and osteoclastogenesis is still unknown. In this study, we found that cellular communication network factor 6 (CCN6) was less produced in a human OSCC cell line, HSC-3 with mesenchymal phenotype, than in HSC-2 cells without it. Notably, CCN6 interacted with bone morphogenetic protein 2 (BMP2) and suppressed the cell migration of HSC-3 cells stimulated by BMP2. Moreover, knockdown of CCN6 in HSC-2 cells led to the promotion of EMT and enhanced the effect of transforming growth factor-β (TGF-β) on the promotion of EMT. Furthermore, CCN6 combined with BMP2 suppressed EMT. These results suggest that CCN6 strongly suppresses EMT in cooperation with BMP2 and TGF-β. Interestingly, CCN6 combined with BMP2 increased the gene expression of receptor activator of nuclear factor-κB ligand (RANKL) in HSC-2 and HSC-3 cells. Additionally, CCN6 interacted with RANKL, and CCN6 combined with RANKL suppressed RANKL-induced osteoclast formation. In metastatic lesions, increasing BMP2 due to the bone destruction led to interference with binding of CCN6 to RANKL, which results in the promotion of bone metastasis of OSCC cells due to continuous osteoclastogenesis. These findings suggest that CCN6 plays dual roles in the suppression of EMT and in the promotion of bone destruction of OSCC in primary and metastatic lesions, respectively, through cooperation with BMP2 and interference with RANKL.

Cortical microarchitecture and remodeling-associated gene expression related to oral cancer prognosis

The objective of this study was to assess the remodeling-associated gene expression in the mandible of patients diagnosed with oral squamous cell carcinoma (OSCC), investigating the cortical microarchitecture, and their influence on disease-free survival (DFS) and overall survival (OS) rates. A total of twenty-four patients who underwent mandibulectomy for OSCC treatment had two bone fragments harvested from the mandible for gene expression (RANK, RANKL, OPG, and SOST), and microarchitecture analysis, including bone volume, surface, mineral density, degree of anisotropy, and fractal dimension. The prognosis of the patients was assessed. The results revealed that RANK, RANKL, and SOST were predominantly downregulated, while OPG was completely downregulated. Tumors located adjacent to the posterior region of the mandible (p = 0.02), with a bone mineral density below 1.03 g/cm3 HA (p = 0.001), and a bone volume less than 86.47% (p = 0.03) were associated with poor outcomes. In conclusion, bone-remodeling-associated genes exhibited downregulation in the cortex of the mandible in OSCC patients. Additionally, the tumor's location within the mandible, bone volume, and cortical bone mineral density were identified as factors impacting DFS.

Piperine Induces Apoptosis and Autophagy in HSC-3 Human Oral Cancer Cells by Regulating PI3K Signaling Pathway

Currently, therapies for treating oral cancer have various side effects; therefore, research on treatment methods employing natural substances is being conducted. This study aimed to investigate piperine-induced apoptosis and autophagy in HSC-3 human oral cancer cells and their effects on tumor growth in vivo. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay demonstrated that piperine reduced the viability of HSC-3 cells and 4',6-diamidino-2-phenylindole staining, annexin-V/propidium iodide staining, and analysis of apoptosis-related protein expression confirmed that piperine induces apoptosis in HSC-3 cells. Additionally, piperine-induced autophagy was confirmed by the observation of increased acidic vesicular organelles and autophagy marker proteins, demonstrating that autophagy in HSC-3 cells induces apoptosis. Mechanistically, piperine induced apoptosis and autophagy by inhibiting the phosphatidylinositol-3-kinase (PI3K)/protein kinase B/mammalian target of rapamycin pathway in HSC-3 cells. We also confirmed that piperine inhibits oral cancer tumor growth in vivo via antitumor effects related to apoptosis and PI3K signaling pathway inhibition. Therefore, we suggest that piperine can be considered a natural anticancer agent for human oral cancer.

Depletion of PARP10 inhibits the growth and metastatic potential of oral squamous cell carcinoma

Background: Although poly (ADP-ribose) polymerase family member 10 (PARP10) has been implicated in the progression of multiple cancer types, its role in oral squamous cell carcinoma (OSCC) remains unknown. This study aimed to examine the function of PARP10 in OSCC and investigate the underlying mechanisms.

Methods: The expression of PARP10 in OSCC was investigated in OSCC patient cohorts. Kaplan-Meier curve analysis was performed to assess the association between PARP10 and prognosis in OSCC. Correlation between PARP10 expression and the related variables was analyzed by χ² test. CKK-8, transwell assay, western blot, immunohistochemistry, immunofluorescence, and bioinformatic analysis, were applied to clarify the role of PARP10 in OSCC.

Results: PARP10 was found to be markedly elevated in OSCC tissues. The upregulation of PARP10 predicted shorter overall survival and disease-specific survival and was significantly correlated with several malignant features. Moreover, depletion of PARP10 markedly inhibited the proliferation, migration, and invasion of OSCC cells, and promoted OSCC cell apoptosis, and resulted in alterations of relevant proteins. Furthermore, a positive correlation was observed between the expression of PARP10 and Ki67, PARP1, MMP2, and VEGF. In addition, depletion of PARP10 impaired the PI3K-AKT and MAPK signaling pathways.

Conclusion: PARP10 is involved in the progression of OSCC via regulation of PI3K-AKT and MAPK signaling pathways.

Significance of cancer stroma for bone destruction in oral squamous cell carcinoma using different cancer stroma subtypes

Stromal cells in the tumor microenvironment (TME) can regulate the progression of numerous types of cancer; however, the bone invasion of oral squamous cell carcinoma (OSCC) has been poorly investigated. In the present study, the effect of verrucous SCC-associated stromal cells (VSCC-SCs), SCC-associated stromal cells (SCC-SCs) and human dermal fibroblasts on bone resorption and the activation of HSC-3 osteoclasts in vivo were examined by hematoxylin and eosin, AE1/3 (pan-cytokeratin) and tartrate-resistant acid phosphatase staining. In addition, the expression levels of matrix metalloproteinase (MMP)9, membrane-type 1 MMP (MT1-MMP), Snail, receptor activator of NF-κB ligand (RANKL) and parathyroid hormone-related peptide (PTHrP) in the bone invasion regions of HSC-3 cells were examined by immunohistochemistry. The results suggested that both SCC-SCs and VSCC-SCs promoted bone resorption, the activation of osteoclasts, and the expression levels of MMP9, MT1-MMP, Snail, RANKL and PTHrP. However, SCC-SCs had a more prominent effect compared with VSCC-SCs. Finally, microarray data were used to predict potential genes underlying the differential effects of VSCC-SCs and SCC-SCs on bone invasion in OSCC. The results revealed that IL1B, ICAM1, FOS, CXCL12, INS and NGF may underlie these differential effects. In conclusion, both VSCC-SCs and SCC-SCs may promote bone invasion in OSCC by enhancing the expression levels of RANKL in cancer and stromal cells mediated by PTHrP; however, SCC-SCs had a more prominent effect. These findings may represent a potential regulatory mechanism underlying the bone invasion of OSCC.

Epithelial-mesenchymal transition related to bone invasion in oral squamous cell carcinoma

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Presence of epithelial-mesenchymal transition markers in tumor-bone interface.

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Dominant infiltrative pattern in bone tissue is associated with lower survival.

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E-cadherin-positive cases were associated with tobacco smoking.

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Vimentin-positive cases were associated with tumors under 4 cm.

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Twist could be strongly involved in bone invasion and in disease progression.

Introduction

Bone invasion is an important prognostic factor in oral squamous cell carcinoma, leading to a lower survival rate and the use of aggressive treatment approaches. Epithelial-mesenchymal transition (EMT) is possibly involved in this process, because it is often related to mechanisms of cell motility and invasiveness. This study examined whether a panel of epithelial-mesenchymal markers are present in cases of oral squamous cell carcinoma with bone invasion and whether these proteins have any relationship with patients’ clinical-pathological parameters and prognostic factors.

Methods

Immunohistochemical analysis of E-cadherin, twist, vimentin, TGFβ1, and periostin was performed in paraffin-embedded samples of 62 oral squamous cell carcinoma cases.

Results

The analysis revealed that most cases (66%) presented with a dominant tumor infiltrative pattern in bone tissue, associated with lower survival rates, when compared with cases with a dominant erosive invasion pattern (P = 0.048). Twenty-seven cases (43%) expressed markers that were compatible with total or partial EMT at the tumor-bone interface. There was no association between evidence of total or partial EMT and other demographic or prognostic features. E-cadherin-positive cases were associated with tobacco smoking (P = 0.022); vimentin-positive cases correlated with tumors under 4 cm (P = 0.043). Twistexpression was observed in tumors with a dominant infiltrative pattern (P = 0.041) and was associated with the absence of periostin (P = 0.031).

Conclusion

We observed evidence of total or partial EMT in oral squamous cell carcinoma bone invasion. The transcription factor twist appears to be involved in bone invasion and disease progression.

Cancer-associated fibroblasts promote oral squamous cell carcinoma progression through LOX-mediated matrix stiffness

Background

Cancer-associated fibroblasts (CAFs), the most abundant cells in the tumor microenvironment, have prominent roles in the development of solid tumors as stromal targets. However, the underlying mechanism of CAFs’ function in oral squamous cell carcinoma (OSCC) development remains unclear. Here, we investigated the role of lysyl oxidase (LOX) expression in CAFs in tumor stromal remodeling and the mechanism of its effect on OSCC progression.

Methods

Multiple immunohistochemistry (IHC) staining was performed to detect the correlation of CAFs and LOX in the stroma of OSCC specimens, as well as the correlation with clinicopathological parameters and prognosis. The expression of LOX in CAFs were detected by RT-qPCR and western blot. The effects of LOX in CAFs on the biological characteristics of OSCC cell line were investigated using CCK-8, wound-healing and transwell assay. CAFs were co-cultured with type I collagen in vitro, and collagen contraction test, microstructure observation and rheometer were used to detect the effect of CAFs on remodeling collagen matrix. Then, collagen with different stiffness were established to investigate the effect of matrix stiffness on the progression of OSCC. Moreover, we used focal adhesion kinase (FAK) phosphorylation inhibitors to explored whether the increase in matrix stiffness promote the progression of OSCC through activating FAK phosphorylation pathway.

Results

LOX was colocalized with CAFs in the stroma of OSCC tissues, and its expression was significantly related to the degree of malignant differentiation and poor prognosis in OSCC. LOX was highly expressed in CAFs, and its knockdown impaired the proliferation, migration, invasion and EMT process of OSCC cells. The expression of LOX in CAFs can catalyze collagen crosslinking and increase matrix stiffness. Furthermore, CAFs-derived LOX-mediated increase in collagen stiffness induced morphological changes and promoted invasion and EMT process in OSCC cells by activating FAK phosphorylation pathway.

Conclusions

Our findings suggest that CAFs highly express LOX in the stroma of OSCC and can remodel the matrix collagen microenvironment, and the increase in matrix stiffness mediated by CAFs-derived LOX promotes OSCC development through FAK phosphorylation pathway. Thus, LOX may be a potential target for the early diagnosis and therapeutic treatment of OSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03181-x.

Identification of Hypoxia-Related Molecular Classification and Associated Gene Signature in Oral Squamous Cell Carcinoma

The high heterogeneity of oral squamous cell carcinoma (OSCC) is the main obstacle for individualized treatment. Recognizing the characteristics of different subtypes and investigating the promising strategies for each subclass are of great significance in precise treatment. In this study, we systematically evaluated hypoxia-mediated patterns together with immune characteristics of 309 OSCC patients in the TCGA training set and 97 patients in the GSE41613 testing set. We further identified two different hypoxia subtypes with distinct immune microenvironment traits and provided treatment programs for the two subclasses. In order to assess hypoxia level individually, we finally constructed a hypoxia-related risk score, which could predict the clinical outcome and immunotherapy response of OSCC patients. In summary, the recognition of different hypoxia patterns and the establishment of hypoxia-related risk score might enhance our understanding of the tumor microenvironment of OSCC and provide more personalized treatment strategies in the future.

The Role of Immune Microenvironment in Maxillofacial Bone Homeostasis

Maxillofacial bone defects are common medical problems caused by congenital defects, necrosis, trauma, tumor, inflammation, and fractures non-union. Maxillofacial bone defects often need bone graft, which has many difficulties, such as limited autogenous bone supply and donor site morbidity. Bone tissue engineering is a promising strategy to overcome the above-mentioned problems. Osteoimmunology is the inter-discipline that focuses on the relationship between the skeletal and immune systems. The immune microenvironment plays a crucial role in bone healing, tissue repair and regeneration in maxillofacial region. Recent studies have revealed the vital role of immune microenvironment and bone homeostasis. In this study, we analyzed the complex interaction between immune microenvironment and bone regeneration process in oral and maxillofacial region, which will be important to improve the clinical outcome of the bone injury treatment.

Bone-targeted erythrocyte-cancer hybrid membrane-camouflaged nanoparticles for enhancing photothermal and hypoxia-activated chemotherapy of bone invasion by OSCC

Background

Jaw bones are the most common organs to be invaded by oral malignancies, such as oral squamous cell carcinoma (OSCC), because of their special anatomical relationship. Various serious complications, such as pathological fractures and bone pain can significantly decrease the quality of life or even survival outcomes for a patient. Although chemotherapy is a promising strategy for bone invasion treatment, its clinical applications are limited by the lack of tumor-specific targeting and poor permeability in bone tissue. Therefore, it is necessary to develop a smart bone and cancer dual targeting drug delivery platform.

Results

We designed a dual targeting nano-biomimetic drug delivery vehicle Asp8[H40-TPZ/IR780@(RBC-H)] that has excellent bone and cancer targeting as well as immune escape abilities to treat malignancies in jaw bones. These nanoparticles were camouflaged with a head and neck squamous cell carcinoma WSU-HN6 cell (H) and red blood cell (RBC) hybrid membrane, which were modified by an oligopeptide of eight aspartate acid (Asp8). The spherical morphology and typical core-shell structure of biomimetic nanoparticles were observed by transmission electron microscopy. These nanoparticles exhibited the same surface proteins as those of WSU-HN6 and RBC. Flow cytometry and confocal microscopy showed a greater uptake of the biomimetic nanoparticles when compared to bare H40-PEG nanoparticles. Biodistribution of the nanoparticles in vivo revealed that they were mainly localized in the area of bone invasion by WSU-HN6 cells. Moreover, the Asp8[H40-TPZ/IR780@(RBC-H)] nanoparticles exhibited effective cancer growth inhibition properties when compared to other TPZ or IR780 formulations.

Conclusions

Asp8[H40-TPZ/IR780@(RBC-H)] has bone targeting, tumor-homing and immune escape abilities, therefore, it is an efficient multi-targeting drug delivery platform for achieving precise anti-cancer therapy during bone invasion.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01088-9.

Functional Heterogeneity of Reelin in the Oral Squamous Cell Carcinoma Microenvironment

Background

Reelin, an extracellular glycoprotein, is expressed on neuronal cells and participates in neuronal migration during brain development. Recently, Reelin also has a vital role in carcinogenesis. However, its role in oral squamous cell carcinoma (OSCC) remains to be explored. The purpose of this study was to explore the roles of Reelin in OSCC.

Methods

The expression of Reelin in cancer-associated fibroblasts (Reelin^CAF) and tumor cells (Reelin^TC) was analyzed by the Gene Expression Omnibus (GEO) database. Immunohistochemistry (IHC) was used to detect the spatial pattern of Reelin in 75 OSCCs. The diagnostic and prognostic values of Reelin were evaluated and also verified by The Cancer Genome Atlas (TCGA) database. Primary CAFs from 13 OSCC patients were isolated to confirm Reelin expression. Thirty-nine OSCC peripheral blood samples were used to analyze the change of immunocytes based on Reelin levels by flow cytometry. The relationship between Reelin and tumor immune microenvironment in head and neck squamous cell carcinoma (HNSCC) tissues was determined by TISIDB and the Tumor Immune Estimation Resource (TIMER) database.

Results

In breast cancer, pancreatic cancer and rectal cancer, Reelin in CAFs was significantly upregulated compared with Reelin in TCs. The IHC results in OSCC also showed that Reelin levels were higher in CAFs. Upregulated Reelin^TC was related to a decreased pN stage and distant metastasis. Strikingly, patients with enhanced Reelin^CAF had a high risk of lymph node metastasis, poor worst pattern of invasion (WPOI), and distant metastasis, but showed comparable Ki-67 level in all OSCC patients, resulting in shorter overall survival (OS) and disease-specific survival (DSS). Unexpectedly, Reelin in tumor-infiltrating lymphocytes (Reelin^TIL) was correlated with postoperative relapse. Patients with high Reelin^TIL, but not Reelin^TC and Reelin^CAF, had poor cytotoxicity of CD8⁺ T cells and higher ratio of CD4/CD8 in peripheral blood. However, Reelin was positively associated with tissue-resident B cells and NK cells in the tumor microenvironment.

Conclusion

Reelin has a versatile function in distinct cell types during the development of OSCC via governing tumor cell and stroma microenvironment.

Oral Squamous Cell Carcinoma Contributes to Differentiation of Monocyte-Derived Tumor-Associated Macrophages via PAI-1 and IL-8 Production

Tumor-associated macrophages (TAMs) promote cancer cell proliferation and metastasis, as well as anti-tumor immune suppression. Recent studies have shown that tumors enhance the recruitment and differentiation of TAMs, but the detailed mechanisms have not been clarified. We thus examined the influence of cancer cells on the differentiation of monocytes to TAM subsets, including CD163+, CD204+, and CD206+ cells, in oral squamous cell carcinoma (OSCC) using immunohistochemistry, flow cytometry, and a cytokine array. Furthermore, we investigated the effect of OSCC cells (HSC-2, SQUU-A, and SQUU-B cells) on the differentiation of purified CD14+ cells to TAM subsets. The localization patterns of CD163+, CD204+, and CD206+ in OSCC sections were quite different. The expression of CD206 on CD14+ cells was significantly increased after the co-culture with OSCC cell lines, while the expressions of CD163 and CD204 on CD14+ cells showed no change. High concentrations of plasminogen activator inhibitor-1 (PAI-1) and interleukin-8 (IL-8) were detected in the conditioned medium of OSCC cell lines. PAI-1 and IL-8 stimulated CD14+ cells to express CD206. Moreover, there were positive correlations among the numbers of CD206+, PAI-1+, and IL-8+ cells in OSCC sections. These results suggest that PAI-1 and IL-8 produced by OSCC contribute to the differentiation of monocytes to CD206+ TAMs.

The Axin2-snail axis promotes bone invasion by activating cancer-associated fibroblasts in oral squamous cell carcinoma

Background

In bone-invasive oral squamous cell carcinoma (OSCC), cancer-associated fibroblasts (CAFs) infiltrate into bony tissue ahead of OSCC cells. In the present study, we aimed to investigate the role of the Axin2-Snail axis in the biological behaviour of CAFs and bone invasion in OSCC.

Methods

The clinicopathological significance of Axin2 and Snail expression was investigated by immunohistochemistry in an OSCC cohort containing 217 tissue samples from patients with long-term follow-up. The influence of the Axin2-Snail axis on the biological behaviour of OSCC cells and CAFs was further investigated both in vitro and in vivo.

Results

Axin2 expression was significantly associated with Snail expression, the desmoplasia status, and bone invasion in patients with OSCC. In multivariate analysis, lymph node metastasis, desmoplasia, Axin2 expression, and Snail expression were independent poor prognostic factors in our cohort. Consistent with these findings, OSCC cells demonstrated attenuated oncogenic activity as well as decreased expression of Snail and various cytokines after Axin2 knockdown in vitro. Among the related cytokines, C-C motif chemokine ligand 5 (CCL5) and interleukin 8 (IL8) demonstrated a strong influence on the biological behaviour of CAFs in vitro. Moreover, both the desmoplastic reaction and osteolytic lesions in the calvaria were predominantly decreased after Axin2 knockdown in OSCC cells in vivo using a BALB/c athymic nude mouse xenograft model.

Conclusions

Oncogenic activities of the Axin2-Snail axis are not limited to the cancer cells themselves but rather extend to CAFs via regulation of the cytokine-mediated cancer-stromal interaction, with further implications for bone invasion as well as a poor prognosis in OSCC.

Bone Invasive Properties of Oral Squamous Cell Carcinoma and its Interactions with Alveolar Bone Cells: An In Vitro Study

BACKGROUND

Co-culture of cancer cells with alveolar bone cells could modulate bone invasion and destructions. However, the mechanisms of interaction between oral squamous cell carcinoma (OSCC) and bone cells remain unclear.

OBJECTIVE

The aim of this study is to analyse the direct and indirect effects of OSCC cells in the stimulation of osteolytic activity and bone invasion.

METHODS

Direct co-culture was achieved by culturing OSCC (TCA8113) with a primary alveolar bone cell line. In the indirect co-culture, the supernatant of TCA8113 cells was collected to culture the alveolar bone cells. To assess the bone invasion properties, in vitro assays were performed.

RESULTS

The proliferation of co-cultured cancer cells was significantly (p<0.05) higher in comparison to the monolayer control cells. However, the proliferation rates were not significantly different between direct and indirect co-cultured cells with indirect co-cultured cells proliferated slightly more than the direct co-cultured cells. Invasion and migration capacities of co-cultured OSCC and alveolar bone cells enhanced significantly (p<0.05) when compared to that of control monolayer counterparts. Most importantly, we noted that OSCC cells directly co-cultured with alveolar bone cells stimulated pronounced bone collagen destruction. In addition, stem cells and epithelialmesenchymal transition markers have shown significant changes in their expression in co-cultured cells.

CONCLUSION

In conclusion, the findings of this study highlight the importance of the interaction of alveolar bone cells and OSCC cells in co-culture setting in the pathogenesis of bone invasion. This may help in the development of potential future biotherapies for bone invasion in OSCC.

CCL28-induced RARβ expression inhibits oral squamous cell carcinoma bone invasion

Oral squamous cell carcinoma (OSCC) frequently invades the maxillary or mandibular bone, and this bone invasion is closely associated with poor prognosis and survival. Here, we show that CCL28 functions as a negative regulator of OSCC bone invasion. CCL28 inhibited invasion and epithelial-mesenchymal transition (EMT), and its inhibition of EMT was characterized by induced E-cadherin expression and reduced nuclear localization of β-catenin in OSCC cells with detectable RUNX3 expression levels. CCL28 signaling via CCR10 increased retinoic acid receptor-β (RARβ) expression by reducing the interaction between RARα and HDAC1. In addition, CCL28 reduced RANKL production in OSCC and osteoblastic cells and blocked RANKL-induced osteoclastogenesis in osteoclast precursors. Intraperitoneally administered CCL28 inhibited tumor growth and osteolysis in mouse calvaria and tibia inoculated with OSCC cells. RARβ expression was also increased in tumor tissues. In patients with OSCC, low CCL28, CCR10, and RARβ expression levels were highly correlated with bone invasion. Patients with OSCC who had higher expression of CCL28, CCR10, or RARβ had significantly better overall survival. These findings suggest that CCL28, CCR10, and RARβ are useful markers for the prediction and treatment of OSCC bone invasion. Furthermore, CCL28 upregulation in OSCC cells or CCL28 treatment can be a therapeutic strategy for OSCC bone invasion.

Carbonic Anhydrase III Promotes Cell Migration and Epithelial-Mesenchymal Transition in Oral Squamous Cell Carcinoma

Epithelial–mesenchymal transition (EMT) is strongly correlated with tumor metastasis and contains several protein markers, such as E-cadherin. Carbonic anhydrase III (CA III) exhibits low carbon dioxide hydratase activity in cancer. However, the detailed mechanisms of CA III and their roles in oral cancer are still unknown. This study established a CA III-overexpressed stable clone and observed the expression of CA III protein in human SCC-9 and SAS oral cancer cell lines. The migration and invasion abilities were determined using a Boyden chamber assay. Our results showed that the overexpression of CA III protein significantly increased the migration and invasion abilities in oral cancer cells. Moreover, a whole genome array analysis revealed that CA III regulated epithelial–mesenchymal transition by reducing the expression of epithelial markers. Data from the GEO database also demonstrated that CA III mRNA is negatively correlated with CDH1 mRNA. Mechanistically, CA III increased the cell motility of oral cancer cells through the FAK/Src signaling pathway. In conclusion, this suggests that CA III promotes EMT and cell migration and is potentially related to the FAK/Src signaling pathway in oral cancer.

Inhibition of ROS-NF-κB-dependent autophagy enhances Hypocrellin A united LED red light-induced apoptosis in squamous carcinoma A431 cells

Cutaneous squamous cell carcinoma (cSCC) is a type of malignant skin tumor derived from epidermal Malpighian cells. Photodynamic therapy is regarded as a crucial method in oncology. Hypocrellin A (HA), an efficient natural photosensitizer, has been reported to exert excellent light induced antiviral, antimicrobial and anticancer activity through mediating multiple signaling pathways. The purpose of the present study is to examine the effects of HA united red light irradiation on human squamous carcinoma A431 cells and further reveal the underlying regulatory mechanisms. The results showed that synergistic treatment of HA and red light irradiation inhibited cell proliferation and induced cell apoptosis and autophagy. Moreover, HA united red light irradiation caused a significant accumulation of reactive oxygen species (ROS), and induced the activation of c-Jun NH 2 terminal kinases (JNKs) which was inhibited by the antioxidant N-Acetyl-cysteine (NAC). Furthermore, HA united red light irradiation activated the nuclear factor-kappa B (NF-κB) pathway, and inhibition of NF-κB activity exacerbated HA united red light irradiation-induced apoptosis but suppressed cell autophagy. In addition, the inhibition of autophagy promoted HA united red light irradiation-induced apoptosis and facilitated the NF-κB activity. Over all, our results revealed that HA united red light irradiation could inhibit A431 cell proliferation by inducing apoptosis and autophagy via the activation of the ROS mediated JNK and NF-κB pathways, providing prospective for HA as a potential therapeutic for the treatment of cSCC.

Bone invasion-targeted chemotherapy with a novel anionic platinum complex (3Pt) for oral squamous cell carcinoma

Cisplatin (CDDP) is an important drug for chemotherapy in patients with head and neck squamous cell carcinoma. Nephrotoxicity and lack of an effect on bone invasion are limitations of CDDP. To increase its antitumor effect on bone invasion and reduce toxicity problems, anionic Pt complex (3Pt) has been developed. The present study aimed to characterize the basis of the cytotoxicity of the novel platinum complex 3Pt in comparison with that of CDDP for oral squamous cell carcinoma. The ionic platinum complex was prepared to increase solubility and avoid platinum nephrotoxicity. Furthermore, 3Pt was designed to target bone hydroxyapatite and has germinal bisphosphonate moieties for drug delivery. In vitro antitumor activity was assayed in two oral squamous cell carcinoma cell lines. To investigate the antitumor and nephrotoxic effects of 3Pt, nude mice with OSC-19 were given 3Pt and CDDP. The in vitro growth-inhibitory effect of 3Pt was significantly less than that of CDDP. However, both 3Pt and CDDP showed equivalent antitumor effects in vivo. Mice injected with CDDP developed renal cell apoptosis; however, those injected with 3Pt were almost free of renal cell injury. In addition to similar in vivo antitumor effects, 3Pt decreased the volume of bone resorption compared to that with CDDP in a bone invasion model using OSC-19. In conclusion, considering the potential advantages in terms of noticeable antitumor activity on bone invasion and reduced nephrotoxicity, 3Pt represents a significant improvement in the development of bone-targeting platinum drugs.

Combination of quercetin and cisplatin enhances apoptosis in OSCC cells by downregulating xIAP through the NF-κB pathway

While cisplatin is a first-line chemotherapeutic drug commonly used to treat patients with oral squamous cell carcinoma (OSCC), the cisplatin-resistance poses a major challenge for its clinical application. Recent studies have shown that quercetin, a natural flavonoid found in various plants and foods possesses an anti-cancer effect. The following study examined the combined effect of quercetin and cisplatin on OSCC apoptosis in vitro and in vivo (using a mice tumor model). We found that quercetin promotes cisplatin-induced apoptosis in human OSCC (cell lines Tca-8113 and SCC-15) by down-regulating NF-κB. Pretreatment of cancer cells with quercetin inhibited the phosphorylation Akt and IKKβ, and led to the suppression of NF-κB and anti-apoptotic protein xIAP. In addition, we observed that the pretreatment of cancer cells with quercetin improves extrinsic and intrinsic apoptosis by activating caspase-8 and caspase-9, respectively. Our in vivo data also indicated that the combination of quercetin and cisplatin may inhibit the xenograft growth in mice. To sum up, our results provide a new evidence for the application of quercetin and cisplatin in OSCC therapy.

CXCL12/CXCR4 pathway orchestrates CSC-like properties by CAF recruited tumor associated macrophage in OSCC

Tumor-associated macrophage (TAM), a crucial component of immune cell infiltrated in tumor microenvironment, is associated with progression of oral squamous cell carcinoma (OSCC). However, it is still unclear how TAM is induced/accumulated and activated around/in OSCC. In the study herein, we tried to understand how TAM accumulates and activates in the OSCC and how TAM promotes OSCC to convert cancer stem cell (CSC). In this study, first important finding was that the M2 macrophages significantly increased in all twenty human OSCC samples in vivo. Cancer-associated fibroblast (CAF)-derived CXCL12 effectively attracted monocytes, which displayed M2 macrophage phenotype. Blocking CXCL12 receptor (CXCR4) significantly reduced chemotaxis of M2 macrophage. Polarized M2 macrophage promoted CSC-like transition in OSCC cell line, Cal27 cells. These CSC-like cells significantly expressed higher Sox2, Oct4, and Nanog genes, were stronger positive for CD44 and CD105, increased cell proliferation with less apoptosis, enhanced cell migration, and were resistant to chemotherapy drug, vineristine. These results indicate that CAF effectively attracts monocytes via the CXCL12/CXCR4 pathway and induces their differentiation to M2 macrophages. Interestingly, these polarized M2 macrophages promote formation of CSC-like cells from the OSCC lead to enhance OSCC proliferation with less apoptosis. Therefore, our findings have potential to lead to novel therapy for the OSCC to target CXCL12-mediated TAM recruitment.

Lentiviral RNA interference-mediated downregulation of Forkhead box M1 expression suppresses growth of oral squamous cell carcinoma in vitro

Oral squamous cell carcinoma (OSCC) is one of the most fatal types of oral cancer worldwide. Forkhead box M1 (FOXM1) is associated with the occurrence and development of a number of types of human cancer, but its function in OSCC remains unclear. The present study aimed to explore the effect of FOXM1 downregulation using lentivirus-mediated short hairpin (sh)RNA against FOXM1 (LV-shFOXM1) in the cell line Tca8113 in vitro. Infection of Tca8113 cells with LV-shFOXM1 inhibited the mRNA and protein expression level of FOXM1. The downregulation of FOXM1 resulted in cell cycle arrest of Tca8113 cells, and the inhibition of proliferation, migration and invasion. The protein expression level of cyclins B1 and D1 were downregulated, whereas those of p27 and p21 were upregulated following infection with LV-shFOXM1, compared with the blank control and LV-shCON groups. In addition, FOXM1 downregulation decreased the expression of matrix metalloproteinase-2 and LV-shFOXM1 significantly suppressed OSCC cell viability. Therefore, FOXM1 may be a target for the treatment of OSCC.

CD47 as a potential prognostic marker for oral leukoplakia and oral squamous cell carcinoma

Cluster of differentiation (CD)47, which acts as a negative indicator for phagocytic cells, is overexpressed on the surface of multiple human solid tumor cell types. Avoiding phagocytosis by CD47 is required for the progression of solid tumors. The present study investigated the expression of CD47 in oral leukoplakia (OLK) and oral squamous cell carcinoma (OSCC), and preliminarily explored the impact of CD47 on the proliferation of OSCC cells. A total of 56 tissue samples, including 36 cases of OLK, 10 cases of OSCC and 10 cases of normal oral mucosa (NOM) were selected to detect the expression of CD47 by immunohistochemistry. For subgroup analysis, OLK samples were divided into OLK with low-risk dysplasia (LR-OLK) and OLK with high-risk dysplasia (HR-OLK). The subcellular localization of CD47 was determined by immunofluorescence in three OSCC cell lines (Tca8113, SCC-9 and Cal-27). The effect of CD47 antibody on the proliferation of the Cal-27 cell line was analyzed using the Cell Counting kit-8 assay. CD47 expression in OLK and OSCC lesions was significantly higher than in NOM (P<0.05). Compared with LR-OLK, the expression of CD47 in HR-OLK and OSCC cells was upregulated (P=0.0327 and P=0.0048, respectively). CD47 was highly expressed in OSCC cell lines (Tca8113, Cal-27 and SCC-9) and weakly expressed in normal oral keratinocytes. The proliferation of Cal-27 cells was inhibited by CD47 antibody in a concentration and time-dependent manner. CD47 may be a reliable biomarker for predicting the progression of oral precancer and cancer, and it may serve as an important molecular target for designing a novel therapy for oral cancer.

Mutant monocyte chemoattractant protein-1 protein (7ND) inhibits osteoclast differentiation and reduces oral squamous carcinoma cell bone invasion

The seven-amino acid truncated (7ND) protein is an N-terminal deletion mutant of monocyte chemoattractant protein-1 (MCP-1) and it functions as a dominant-negative inhibitor. 7ND and wild-type MCP-1 form a heterodimer, which binds to MCP-1 receptors and inhibits monocyte chemotaxis. In the present study, the 7ND protein was cloned, expressed and purified. An MTT assay revealed that the proliferation of oral squamous cell carcinoma (OSCC) SCC25 cells was not affected following 3 days of treatment with synthetic 7ND protein. Serial dilutions of the 7ND protein were tested for monocyte migration and osteoclast differentiation, and tartrate-resistant acid phosphatase staining demonstrated that significantly fewer osteoclasts were differentiated from cluster of differentiation 14⁺ (CD14⁺) monocytes using magnetic activated cell sorting. Immunofluorescence confirmed these results and significantly less F-actin staining was observed in 7ND-treated osteoclasts. Furthermore, bone invasion was examined by subcutaneously injecting SCC25 cells into the area overlaying the calvariae of nude mice. The results demonstrated that the average tumor volume of SCC25 cells with 7ND protein was similar to the average volume of tumors formed by untreated SCC25 cells. Flow cytometric analysis suggested that the CD14⁺ subpopulation in the bone marrow of 7ND-treated mice was reduced compared with that of untreated mice. Micro-computed tomography imaging revealed significantly less bone resorption in the calvariae injected with SCC25 cells plus the 7ND protein. Taken together, the results of the present study demonstrated the potential therapeutic value of the 7ND protein. The 7ND MCP-1 variant not only functions in vitro to inhibit osteoclast differentiation, but also reduces the progression of bone invasion by OSCC cells in vivo.

Loss of RUNX3 expression inhibits bone invasion of oral squamous cell carcinoma

High recurrence and lower survival rates in patients with oral squamous cell carcinoma (OSCC) are associated with its bone invasion. We identified the oncogenic role of RUNX3 during bone invasion by OSCC. Tumor growth and the generation of osteolytic lesions were significantly inhibited in mice that were subcutaneously inoculated with RUNX3-knockdown human OSCC cells. RUNX3 knockdown enhanced TGF-β-induced growth arrest and inhibited OSCC cell migration and invasion in the absence or presence of transforming growth factor-β (TGF-β), a major growth factor abundant in the bone microenvironment. RUNX3 knockdown induced cell cycle arrest at the G1 and G2 phases and promoted G2 arrest by TGF-β in Ca9.22 OSCC cells. RUNX3 knockdown also inhibited both the basal and TGF-β-induced epithelial-to-mesenchymal transition by increasing E-cadherin expression and suppressing the nuclear translocation of β-catenin. In addition, the expression and TGF-β-mediated induction of parathyroid hormone-related protein (PTHrP), one of key osteolytic factors, was blocked in RUNX3-knockdown OSCC cells. Furthermore, treating human osteoblastic cells with conditioned medium derived from RUNX3-knockdown OSCC cells reduced the receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin ratio compared with treatment with conditioned medium from RUNX3-expressing cells. These findings indicate that RUNX3 expression in OSCC cells contributes to their bone invasion and the resulting osteolysis by inducing their malignant behaviors and production of osteolytic factors. RUNX3 alone or in combination with TGF-β and PTHrP may be a useful predictive biomarker and therapeutic target for bone invasion by oral cancer.

Signal regulatory protein α associated with the progression of oral leukoplakia and oral squamous cell carcinoma regulates phenotype switch of macrophages

Signal regulatory protein α (SIRPα) is a cell-surface protein expressed on macrophages that are regarded as an important component of the tumor microenvironment. The expression of SIRPα in oral leukoplakia (OLK) and oral squamous cell carcinoma (OSCC), and further explored the role of SIRPα on the phenotype, phagocytosis ability, migration, and invasion of macrophages in OSCC were investigated. The expression of SIRPα in OLK was higher than in OSCC, correlating with the expression of CD68 and CD163 on macrophages. After cultured with the conditioned media of oral cancer cells, the expression of SIRPα on THP-1 cells was decreased gradually. In co-culture system, macrophages were induced into M2 phenotype by oral cancer cells. Blockade of SIRPα inhibited phagocytosis ability and IL-6, TNF-α productions of macrophages. In addition, the proliferation, migration, and IL-10, TGF-β productions of macrophages were upregulated after blockade of SIRPα. Macrophages upregulated the expression of SIRPα and phagocytosis ability, and inhibited the migration and invasion when the activation of NF-κB was inhibited by pyrrolidine dithiocarbamate ammonium (PDTC). Hence, SIRPα might play an important role in the progression of OLK and oral cancer, and could be a pivotal therapeutic target in OSCC by regulating the phenotype of macrophages via targeting NF-κB.

Dihydromyricetin promotes autophagy and apoptosis through ROS-STAT3 signaling in head and neck squamous cell carcinoma

Chemotherapy is an effective weapon in the battle against cancer, but numerous cancer patients are either not sensitive to chemotherapy or develop drug resistance to current chemotherapy regimens. Therefore, an effective chemotherapy mechanism that enhances tumor sensitivity to chemotherapeutics is urgently needed. The aim of the present study was to determine the antitumor activity of dihydromyricetin (DHM) on head and neck squamous cell carcinoma (HNSCC) and its underlying mechanisms. We demonstrated that DHM can markedly induce apoptotic cell death and autophagy in HNSCC cells. Meanwhile, increased autophagy inhibited apoptosis. Pharmacological or genetic inhibition of autophagy further sensitized the HNSCC cells to DHM-induced apoptosis. Mechanistic analysis showed that the antitumor of DHM may be due to the activation phosphorylation of signal transducer and activator of transcription 3 (p-STAT3), which contributed to autophagy. Importantly, DHM triggered reactive oxygen species (ROS) generation in the HNSCC cells and the levels of ROS decreased with N-acetyl-cysteine (NAC), a ROS scavenger. Moreover, NAC abrogated the effects of DHM on STAT3-dependent autophagy. Overall, the following critical issues were observed: first, DHM increased the p-STAT3-dependent autophagy by generating ROS-signaling pathways in head and neck squamous cell carcinoma. Second, inhibiting autophagy could enhance DHM-induced apoptosis in head and neck squamous cell carcinoma.

Characterization of different osteoclast phenotypes in the progression of bone invasion by oral squamous cell carcinoma

The present study aimed to characterize different phenotypes of osteoclasts in the progression of bone invasion by oral squamous cell carcinoma (OSCC). A local bone invasion model of OSCC was established by injecting SCC25 human OSCC cells into the center of calvariae in nude mice, and all mice were found to have a typical bone resorption area. Staining for tartrate-resistant acid phosphatase (TRAP) revealed various types of giant osteoclasts in the tumour-bone interface. Bone marrow cells (BMCs) were isolated from the nude mice for primary osteoclast culture, but only a few giant osteoclasts were generated. Additionally, special blood centrifuge tubes were utilized to obtain large numbers of peripheral blood mononuclear cells (PBMCs). Using magnetic activated cell sorting (MACS) and the cytokines colony-stimulating factor (CSF) and receptor activator of nuclear factor-κb ligand (RANKL), we differentiated human osteoclasts from CD14+ monocytes of PBMCs. Bone resorption was further confirmed by a bone resorption assay. Finally, Transwell inserts were used for indirect cell co-culture of SCC25 cells and CD14+ monocytes. Expression of specific osteoclast markers was detected by real-time PCR and western blotting. After co-culture for 3 and 6 days, conditioned medium (CM) of SCC25 cells stimulated the expression of osteoclast markers, and additional osteoclasts were detected through staining of TRAP and F-actin. In the present study distinct osteoclast phenotypes were observed in the established bone invasion animal model, and were confirmed using various primary osteoclast cultures. CM of OSCC cells may promote the expression of osteoclast markers and induce the differentiation of monocytes to mature osteoclasts, which can resorb adjacent bone tissue.

Cancer-associated fibroblasts promote bone invasion in oral squamous cell carcinoma

Background:

The molecular mechanisms involved in the invasion of bone by oral squamous cell carcinomas (OSCC) are poorly understood, and little is known about the role of cancer-associated fibroblasts (CAF), the presence of which confers a poor prognosis.

Methods:

Clinicopathological data from 277 OSCC cases involving bone resections were reviewed, and 32 cases thoroughly analysed histologically. Immunohistochemistry was used to examine αSMA, RANKL and OPG. Western blotting and qPCR were used to assess myofibroblast (CAF-like) differentiation, RANKL and OPG expression in vitro, and RANKL secretion was analysed by ELISA. Osteoclastogenesis was examined using TRAP staining, multinucleation and pit forming assays.

Results:

Fibrous stroma intervened between tumour and bone in the majority of cases, with no direct contact between cancer cells and bone. RANKL and OPG, two proteins key to regulating bone resorption, were expressed in tumour cells as well as fibrous stroma adjacent to bone and αSMA-positive myofibroblastic CAF were consistently seen infiltrating into bone ahead of tumour cells. Human primary osteoblasts cultured with conditioned media from human OSCC-derived cells and human primary CAF showed a significant increase in RANKL and a decline in OPG mRNA expression. RANKL secretion was significantly increased in primary oral fibroblasts induced to differentiate into a CAF-like phenotype by transforming growth factor-β1 (TGF-β1) treatment and in primary CAF. Indirect co-culture of murine macrophages with conditioned media from CAF (experimentally derived and isolated from OSCCs) resulted in a marked increase in osteoclastogenesis (in excess of that provoked by cancer cells) determined by tartrate-resistant acid phosphatase activity, multinucleation and resorption pit formation.

Conclusions:

This study is the first to describe a functional role for CAFs in bone invasion and turnover, identifying a novel potential therapeutic target and diagnostic indicator in this difficult to treat bone invasive malignancy.

Utilization of E-cadherin by monocytes from tumour cells plays key roles in the progression of bone invasion by oral squamous cell carcinoma

E-cadherin (E-cad) is recently reported to be expressed in early stages of osteoclastogenesis, and blocking E-cad with neutralizing antibodies decreases osteoclast differentiation. Since our previous research demonstrates the loss of E-cad protein in the bone invasion by oral squamous cell carcinoma (OSCC), we hypothesize that E-cad may be utilized by monocytes to fuse and differentiate into osteoclasts. Two research models are used in the present study to explore our hypothesis. On one hand, we use OSCC cells of SCC25 to establish an animal model of bone invasion by OSCC, and investigate whether E-cad protein disappears in vivo; on the other hand, we use the indirect co-culture model of SCC25 and RAW 264.7 cells, with the treatment of transforming growth factor-β1 (TGF-β1), and observe whether the decreased E-cad protein is ‘hijacked’ in vitro. Results showed the animal model of OSCC with bone invasion was successfully established. Immunohistochemistry (IHC) found similar changes of E-cad protein, which was weakly stained by tumour cells. By using 5 ng/ml of TGF-β1, we confirmed the artificial epithelial-mesenchymal transition (EMT) of SCC25 cells, with changes of EMT marker expression and cell morphology. Real-time PCR showed E-cad mRNA decreased in SCC25 while increased in RAW 264.7 of the indirect cell co-culture model, and immunofluoresence (IF) observed the evident switch of E-cad staining from SCC25 to RAW 264.7. With the supplement of receptor activator of NF-κB ligand (RANKL), tartrate-resistant acid phosphatase (TRAP) and F-actin staining confirmed the increased number of osteoclasts. Taken together, our study found the switch of E-cad protein in the progression of bone invasion by OSCC. The loss of E-cad in tumour cells may be utilized by monocytes to differentiate into osteoclasts, thus further explaining the underlying mechanisms of bone invasion by OSCC, which may supply clues for future molecular biotherapies.

Blockade of adenosine A2A receptor enhances CD8+ T cells response and decreases regulatory T cells in head and neck squamous cell carcinoma

BACKGROUND

Cancer immunotherapy offers a promising approach in cancer treatment. The adenosine A2A receptor (A2AR) could protect cancerous tissues from immune clearance via inhibiting T cells response. To date, the role of A2AR in head and neck squamous cell carcinoma (HNSCC) has not been investigated. Here, we sought to explore the expression and immunotherapeutic value of A2AR blockade in HNSCC.

METHODS

The expression of A2AR was evaluated by immunostaining in 43 normal mucosae, 48 dysplasia and 165 primary HNSCC tissues. The immunotherapeutic value of A2AR blockade was assessed in vivo in genetically defined immunocompetent HNSCC mouse model.

RESULTS

Immunostaining of HNSCC tissue samples revealed that increased expression of A2AR on tumor infiltrating immune cells correlated with advanced pathological grade, larger tumor size and positive lymph node status. Elevated A2AR expression was also detected in recurrent HNSCC and HNSCC tissues with induction chemotherapy. The expression of A2AR was found to be significantly correlated with HIF-1α, CD73, CD8 and Foxp3. Furthermore, the increased population of CD4⁺Foxp3⁺ regulatory T cells (Tregs), which partially expressed A2AR, was observed in an immunocompetent mouse model that spontaneously develops HNSCC. Pharmacological blockade of A2AR by SCH58261 delayed the tumor growth in the HNSCC mouse model. Meanwhile, A2AR blockade significantly reduced the population of CD4⁺ Foxp3⁺ Tregs and enhanced the anti-tumor response of CD8⁺ T cells.

CONCLUSIONS

These results offer a preclinical proof for the administration of A2AR inhibitor on prophylactic experimental therapy of HNSCC and suggest that A2AR blockade can be a potential novel strategy for HNSCC immunotherapy.

Selective blockade of B7-H3 enhances antitumour immune activity by reducing immature myeloid cells in head and neck squamous cell carcinoma

Immature myeloid cells including myeloid-derived suppressor cells (MDSCs) and tumour-associated macrophages (TAMs) promote tumour growth and metastasis by facilitating tumour transformation and angiogenesis, as well as by suppressing antitumour effector immune responses. Therefore, strategies designed to reduce MDSCs and TAMs accumulation and their activities are potentially valuable therapeutic goals. In this study, we show that negative immune checkpoint molecule B7-H3 is significantly overexpressed in human head and neck squamous cell carcinoma (HNSCC) specimen as compared with normal oral mucosa. Using immunocompetent transgenic HNSCC models, we observed that targeting inhibition of B7-H3 reduced tumour size. Flow cytometry analysis revealed that targeting inhibition of B7-H3 increases antitumour immune response by decreasing immunosuppressive cells and promoting cytotoxic T cell activation in both tumour microenvironment and macroenvironment. Our study provides direct in vivo evidence for a rationale for B7-H3 blockade as a future therapeutic strategy to treat patients with HNSCC.

Transforming growth factor-β1 suppresses bone morphogenetic protein-2-induced mesenchymal-epithelial transition in HSC-4 human oral squamous cell carcinoma cells via Smad1/5/9 pathway suppression

Squamous cell carcinoma is the most common cancer in the oral cavity. We previously demonstrated that transforming growth factor-β1 (TGF-β1) promotes the epithelial-mesenchymal transition (EMT) of human oral squamous cell carcinoma (hOSCC) cells; however, it remains to be clarified whether the TGF-β superfamily member bone morphogenetic protein (BMP) affects this process in hOSCC cells. Here, we examined the independent and collective effects of TGF-β1 and BMP-2 on EMT and mesenchymal‑epithelial transition (MET) in a panel of four hOSCC cell lines. Notably, we found that HSC-4 cells were the most responsive to BMP-2 stimulation, which resulted in the upregulation of Smad1/5/9 target genes such as the MET inducers ID1 and cytokeratin 9 (CK9). Furthermore, BMP-2 downregulated the mesenchymal marker N-cadherin and the EMT inducer Snail, but upregulated epithelial CK9 expression, indicating that BMP-2 prefers to induce MET rather than EMT. Moreover, TGF-β1 dampened BMP-2-induced epithelial gene expression by inhibiting Smad1/5/9 expression and phosphorylation. Functional analysis revealed that TGF-β1 and BMP-2 significantly enhanced HSC-4 cell migration and proliferation, respectively. Collectively, these data suggest that TGF-β positively regulates hOSCC invasion in the primary tumor, whereas BMP-2 facilitates cancer cell colonization at secondary metastatic sites. Thus, the invasive and metastatic characteristics of hOSCC appear to be reciprocally regulated by BMP and TGF-β.

CCL2/EGF positive feedback loop between cancer cells and macrophages promotes cell migration and invasion in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) represents the most frequent malignancy in the head and neck region, and the survival rate has not been improved significantly over the past three decades. It has been reported the infiltrated macrophages contribute to the malignant progression of HNSCC. However, the crosstalk between macrophages and cancer cells remains poorly understood. In the present study, we explored interactions between monocytes/macrophages and HNSCC cells by establishing the direct co-culture system, and found that the crosstalk promoted the migration and invasion of cancer cells by enhancing the invadopodia formation through a CCL2/EGF positive feedback loop. Our results demonstrated HNSCC cells educated monocytes into M2-like macrophages by releasing C-C motif chemokine ligand 2 (CCL2, or MCP-1). And the M2-like macrophages secreted epithelial growth factor (EGF), which increased the motility of HNSCC cells by enhancing the invadopodia formation. These subcellular pseudopodia degraded extracellular matrix (ECM), facilitating tumor local invasion and distant metastasis. Moreover, EGF up-regulated CCL2 expression in HNSCC cells, which recruited monocytes and turned them into M2-like macrophages, thus forming a positive feedback paracrine loop. Finally, we reported that curcumin, a powerful natural drug, suppressed the production of EGF and CCL2 in macrophages and cancer cells, respectively, blocking the feedback loop and suppressing the migration and invasion of HNSCC cells. These results shed light on the possibilities and approaches based on targeting the crosstalk between cancer cells and monocytes/macrophages in HNSCC for potential cancer therapy.

Tumor growth suppression by inhibiting both autophagy and STAT3 signaling in HNSCC

Autophagy is considered as a double-edged sword. It can prolong the survival of cancer cells and enhance its resistance to apoptosis, and paradoxically, defective autophagy has been linked to increased tumorigenesis, but the mechanism behind this phenomenon is unclear. In this study, we demonstrated that decreased phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) was correlated with increased autophagy through the Akt/mTOR and Erk signaling pathways in human head and neck squamous cell carcinoma (HNSCC). We also showed that blockage of STAT3 by NSC74859 could markedly induce apoptotic cell death and autophagy. Meanwhile, increased autophagy inhibited apoptosis. The pharmacological or genetic inhibition of autophagy and STAT3 further sensitized HNSCC cells to apoptosis. Furthermore, evidence from xenograft model proved that suppressed STAT3 activity combined with inhibition of autophagy promoted tumor regression better than either treatment alone. Taken together, this present study demonstrated that autophagy alleviates apoptotic cell death in HNSCC, and combination of inhibition of STAT3 by NSC74859 and autophagy might be a promising new therapeutic strategy for HNSCC.

CD73 is associated with poor prognosis in HNSCC

CD73 is a cell surface immunosuppressive enzyme involved in tumor progression and metastasis. While patients whose cancer cells express elevated CD73 are typically associated with an unfavorable outcome, the clinical impact of CD73 expression in patients with Head and neck squamous cell carcinoma (HNSCC) remains unclear. In the present study, we investigated the prognostic significance of CD73 in HNSCC using gene and protein expression analyses. Our results demonstrate that high levels of CD73 are significantly associated with reduced overall survival in patients with HNSCC. We also investigated the functional role of CD73 in vitro and demonstrated that CD73 promotes HNSCC migration and invasion through adenosine A3R stimulation and the activation of EGF/EGFR signaling. Moreover, in vivo xenograft studies demonstrated that CD73 promotes tumorigenesis. In conclusion, our study highlights a role for CD73 as a poor prognostic marker of patient survival and also as a candidate therapeutic target in HNSCCs.

p16 expression independent of human papillomavirus is associated with lower stage and longer disease-free survival in oral cavity squamous cell carcinoma

There is limited information regarding the incidence of p16 expression, its association with human papillomavirus (HPV) and prognosis in oral cavity squamous cell carcinoma (OSCC). The role of p16 in OSCC is evaluated in 215 cases using tissue microarrays (TMAs). p16 immunohistochemistry and HPV in situ hybridisation were performed on TMAs following histopathology review of 215 patients with OSCC in the Sydney Head and Neck Cancer Institute database. Thirty-seven (17.2%) cases showed p16 expression without association with HPV. p16 expression significantly decreased with increasing pT category (p=0.002). p16 expression was associated with longer disease-specific survival on univariable analysis (p=0.044) but not on multivariable analysis adjusting for depth of invasion. Amongst patients receiving adjuvant radiotherapy, patients with p16 expression had significantly longer disease-free and overall survival. p16 expression was seen in early stage OSCCs and was associated with better survival following surgery and radiotherapy. While not an independent predictor of survival, p16 may mediate its effects by contributing to reduced proliferative capacity, leading to smaller tumour size and lower invasive potential.

Insulin-like growth factor-II mRNA binding protein-3 and podoplanin expression are associated with bone invasion and prognosis in oral squamous cell carcinoma

OBJECTIVE

This study aimed to evaluate the prognostic implications of insulin-like growth factor-II mRNA binding protein-3 (IMP3) and podoplanin (PDPN) as therapeutic targets against oral squamous cell carcinoma (OSCC) with bone invasion.

STUDY DESIGN

We elucidated the correlation of IMP3 and PDPN expression with bone invasion in 160 OSCC tissue specimens, and assessed a mouse calvarium xenograft model using an IMP3- and PDPN-depleted OSCC cell line.

RESULTS

The retrospective analysis revealed that the expression of IMP3 and PDPN is significantly correlated with T stage, lymph node metastasis, and the overall survival of OSCC patients. In addition, the dual expression of IMP3 and PDPN but not the single expression of either IMP3 or PDPN was associated with bone invasion and the number of osteoclasts in patients with OSCC. In support of these findings, IMP3 or PDPN depletion inhibited the invasive capacity of OSCC cells in a three-dimensional culture system, tumorigenesis, and regional bone destruction in a xenograft mouse model. In addition, IMP3 or PDPN depletion inhibited the expression of interleukin (IL)-6 and IL-8 in OSCC cells, and decreased the expression of receptor activator of NF-κB ligand (RANKL) in xenograft tumor tissues of OSCC.

CONCLUSIONS

These results suggest that IMP3 and PDPN may have strong influence on the pathogenesis of OSCC, especially in bone invasion, and may serve as novel therapeutic targets with prognostic implications for bone-invasive OSCC.

T regulatory and Th17 cells in chronic rhinosinusitis with polyps

BACKGROUND

Chronic rhinosinusitis (CRS) is categorized into 2 types based on the absence (CRSsNP) and presence of nasal polyps (CRSwNP). Although CRSsNP patients lack nasal polyps, the mucosa may show variable degrees of polypoid change. This raises the question of whether or not the classification system is an over simplification and that CRSsNP and CRSwNP only represent 2 phenotypic extremes along a broader spectrum of immunologically different disease processes. To investigate this, adaptive and innate immune cells were compared in the different tissue types within CRSsNP and CRSwNP patients.

METHODS

Tissue from 15 CRSwNP, 6 CRSsNP, and 8 healthy control patients was obtained prospectively. Nonpolypoid mucosa, polypoid tissues, and polyps were obtained at the time of endoscopic sinus surgery and analyzed using flow cytometry for various adaptive and innate immune cell subsets.

RESULTS

In the polyps from CRSwNP patients there were significantly more T regulatory (Treg) cells (12.86 ± 12.60 vs 2.83 ± 4.68) and Th17 cells (16.12 ± 11.75 vs 2.31 ± 2.13) compared to the polypoid tissue from CRSsNP patients. Cellular infiltrates in the nonpolypoid or polypoid mucosa of the different patient categories showed no difference in CRSwNP, CRSsNP and control groups.

CONCLUSION

This observational study identified an increase in Treg and Th17 cells in CRSwNP patients implying that these cells may be implicated in polyp development. Importantly it also identified a similar inflammatory infiltrate in nonpolyp or polypoid mucosa across control, CRSsNP, and CRSwNP groups inferring that polyps should be sampled when studying CRSwNP.

CTLA4 blockade reduces immature myeloid cells in head and neck squamous cell carcinoma

Immature myeloid cells such as myeloid-derived suppressor cells (MDSCs) and M2 macrophages play a vital role in the tumor immune escape and tumor progression. Cytotoxic T lymphocyte-associated antigen 4 (CTLA4), as a negative immune checkpoint, is highly expressed in numerous solid tumors. However, precise functions of CTLA4 in head and neck squamous cell carcinoma (HNSCC) have not yet been elucidated. In this study, we demonstrated that the ratio of CD8(+)/CTLA4 can be used as a potential index with a clinical prognostic value for HNSCC. Using immunocompetent transgenic mouse model with spontaneous HNSCC, we directly observed that targeting CTLA4 decreases MDSCs and M2 macrophages and promotes T cell activation in both tumor microenvironment and macro-environment. In all, our study provides direct evidence in vivo and proposes a rationale for CTLA4 inhibition as a future therapeutic strategy in patients with HNSCC.

Transient transfection of macrophage migration inhibitory factor small interfering RNA disrupts the biological behavior of oral squamous carcinoma cells

Macrophage migration inhibitory factor (MIF) is closely associated with tumorigenesis. The present study aimed to investigate the effects of MIF on the proliferation, migration and colony formation of oral squamous cell carcinoma (OSCC), and to quantify the protein expression levels of MIF in OSCC tissue samples. Firstly, small interfering (si) RNA was used to knock down the gene expression of MIF in Tca8113, HN5 and SCC25 OSCC cells. Secondly, proliferation, migration and colony formation of the OSCC cells were determined by MTT, transmigration and colony formation assays, respectively. Western blotting was performed to detect changes in the protein expression levels of the epithelial mesenchymal transition markers, Twist-related protein 1 (Twist1), matrix metalloproteinase (MMP)-2 and MMP-9. Finally, immunohistochemistry was used to examine the protein expression of MIF in OSCC tissue samples. The results demonstrated that siRNA against MIF significantly downregulated the expression levels of MIF in all OSCC cells, and decreased their proliferation and migration ability. Colony formation ability was also inhibited in the OSCC cells following transfection with MIF siRNA. Furthermore, western blotting demonstrated that the protein expression of Twist1 was decreased similarly to those of MIF. The protein expression of MMP-2 revealed no change, whereas that of MMP-9 decreased. The protein expression of MIF was detected in OSCC tissue samples with staining predominantly located in the cell membrane and cytoplasm. The present study demonstrated that MIF may be important in the pathogenesis and progression of OSCC, and indicated its potential therapeutic value.

Synergistic Effect of Sorafenib and Radiation on Human Oral Carcinoma in vivo

Oral squamous cell carcinoma often causes bone invasion resulting in poor prognosis and affects the quality of life for patients. Herein, we combined radiation with sorafenib, to evaluate the combination effect on tumor progression and bone erosion in an in situ human OSCC-bearing mouse model. Treatment procedure were arranged as following groups: (a) normal (no tumor); (b) control (with tumor); (c) sorafenib (10 mg/kg/day); (d) radiation (single dose of 6 Gy); (e) pretreatment (sorafenib treatment for 3 days prior to radiation), and (f) concurrent treatment (sorafenib and radiation on the same day). The inhibition of tumor growth and expression level of p65 of NF-κB in tumor tissues were the most significant in the pretreatment group. EMSA and Western blot showed that DNA/NF-κB activity and the expressions of NF-κB-associated proteins were down-regulated. Notably, little to no damage in mandibles and zygomas of mice treated with combination of sorafenib and radiation was found by micro-CT imaging. In conclusion, sorafenib combined with radiation suppresses radiation-induced NF-κB activity and its downstream proteins, which contribute to radioresistance and tumorigenesis. Additionally, bone destruction is also diminished, suggesting that combination treatment could be a potential strategy against human OSCC.