Significance of the fibrous stroma in bone invasion by human gingival squamous cell carcinomas

Assessment of the Electrolyte Heterogeneity of Tissues in Mandibular Bone-Infiltrating Head and Neck Cancer Using Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was recently introduced as a rapid bone analysis technique in bone-infiltrating head and neck cancers. Research efforts on laser surgery systems with controlled tissue feedback are currently limited to animal specimens and the use of nontumorous tissues. Accordingly, this study aimed to characterize the electrolyte composition of tissues in human mandibular bone-infiltrating head and neck cancer. Mandible cross-sections from 12 patients with bone-invasive head and neck cancers were natively investigated with LIBS. Representative LIBS spectra (n = 3049) of the inferior alveolar nerve, fibrosis, tumor stroma, and cell-rich tumor areas were acquired and histologically validated. Tissue-specific differences in the LIBS spectra were determined by receiver operating characteristics analysis and visualized by principal component analysis. The electrolyte emission values of calcium (Ca) and potassium (K) significantly (p < 0.0001) differed in fibrosis, nerve tissue, tumor stroma, and cell-rich tumor areas. Based on the intracellular detection of Ca and K, LIBS ensures the discrimination between the inferior alveolar nerve and cell-rich tumor tissue with a sensitivity of ≥95.2% and a specificity of ≥87.2%. The heterogeneity of electrolyte emission values within tumorous and nontumorous tissue areas enables LIBS-based tissue recognition in mandibular bone-infiltrating head and neck cancer.

The role of potassium in depth profiling of the tumor border in bone-invasive oral cancer using laser-induced breakdown spectroscopy (LIBS): a pilot study

PURPOSE

Microscopic tumor spread beyond the macroscopically visible tumor mass in bone represents a major risk in surgical oncology, where the spatial complexity of bony resection margins cannot be countered with rapid bone analysis techniques. Laser-induced breakdown spectroscopy (LIBS) has recently been introduced as a promising option for rapid bone analysis. The present study aimed to use LIBS-based depth profiling based on electrolyte disturbance tracking to evaluate the detection of microscopic tumor spread in bone.

METHODS

After en bloc resection, the tumor-infiltrated mandible section of a patient's segmental mandibulectomy specimen was natively investigated using LIBS. Spectral and electrolytic depth profiles were analyzed across 30 laser shots per laser spot position in healthy bone and at the tumor border. For the histological validation of the lasered positions, the mandibular section was marked with a thin separating disc.

RESULTS

Solid calcium (Ca) from hydroxyapatite and soluble Ca from dissolved Ca can be reliably differentiated using LIBS and reflect the natural heterogeneity of healthy bone. Increased potassium (K) emission values in otherwise typically healthy bone spectra are the first spectral signs of tumorous bone invasion. LIBS-based depth profiles at the tumor border region can be used to track tumor-associated changes within the bone with shot accuracy based on the distribution of K.

CONCLUSION

Depth profiling using LIBS might enable the detection of microscopic tumor spread in bone. In the future, direct electrolyte tracking using LIBS should be applied to other intraoperative challenges in surgical oncology to advance rapid bone analysis by spectroscopic-optical techniques.

Real-time detection of bone-invasive oral cancer with laser-induced breakdown spectroscopy: A proof-of-principle study

OBJECTIVES

Intraoperative definition of resection margin status in bone-invasive oral cancer is a fundamental problem in oncologic surgery due to the lack of rapid bone analysis methods. Laser-induced breakdown spectroscopy (LIBS) provides direct measurement with real-time examination of a minimal tissue sample. This proof-of-principle study aimed to evaluate the possibility of distinguishing tumorous and healthy areas with LIBS.

MATERIALS AND METHODS

LIBS experiments were executed on native segmental mandibulectomy specimens from 15 patients with bone-invasive oral cancer. Normalized and intensity-matched spectra were compared. Under biological derivation, peak area calculation and principal component analysis (PCA) were applied. The discriminatory power of the PCAs was correlated with the architectural and cytological characteristics of the lasered tumor tissue. Receiver operating characteristics analysis was used to evaluate the performance of LIBS in the real-time detection of bone-invasive cancer.

RESULTS

Calcium (Ca), which is high in healthy bone, is replaced by potassium (K) and sodium (Na) in bone-invasive cancer. The degree of stromal induction is significantly correlated with the discriminatory power between healthy and tumorous spectra. In this study, LIBS ensured an overall sensitivity of 95.51% and a specificity of 98.64% via the intracellular detection of K and Na.

CONCLUSION

This study demonstrated robust real-time detection of bone-invasive oral cancer with LIBS, which may lay the foundation for establishing LIBS as a rapid bone analysis method. Further development of a LIBS-guided assessment of bone tumor resection margins might reduce the extent of bony resection without compromising oncologic safety.

[Advances in molecular mechanisms of bone invasion by oral cancer]

Bone invasion by oral cancer is a common clinical problem, which affects the choice of treatment and predicts a poor prognosis. Unfortunately, the molecular mechanism of this phenomenon has not been fully elucidated. Current studies have revealed that oral cancer cells modulate the formation and function of osteoclasts through the expression of a series of signal molecules. Many signal pathways are involved in this process, of which receptor activator of nuclear factor-κB ligand/receptor activator of nuclear factor-κB/osteoprotegerin signaling pathway attracted much attention. In this review, we introduce recent progress in molecular mechanisms of bone invasion by oral cancer.

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.

Variability in pathologic interpretation of mandibular invasion

OBJECTIVES/HYPOTHESIS

Our objective was to identify the accuracy, sensitivity, and specificity of pathological interpretation of mandibular invasion by oral cavity squamous cell carcinoma (SCC) and compare the sensitivity of detecting mandibular invasion in the erosive versus the infiltrative patterns of invasion. We also aimed to describe the significance of the terminology the carcinoma "abuts the mandible" in pathologic interpretation of mandibular invasion.

STUDY DESIGN

Retrospective case series.

METHODS

Mandibulectomy specimens from patients who underwent surgical treatment for oral cavity SCC between January 1, 2005 and December 31, 2015 were retrospectively reviewed by a board-certified anatomic pathologist. The accuracy of pathologic interpretation of mandibular invasion was calculated using the retrospective interpretation of bone invasion as the true interpretation, which was compared to the interpretation on the original pathology report. Incidence of encountering the terminology the carcinoma "abuts the mandible" in the pathology report was calculated.

RESULTS

A series of 108 consecutive mandibulectomy specimens were reviewed. Sixty-nine percent (74/108) of cases were interpreted as having mandibular invasion. The accuracy of interpreting mandibular invasion was 84%. The sensitivities for interpretation of mandibular invasion for the erosive and infiltrative patterns of invasion were 77% (30/39) and 91% (32/35), respectively (P = .08). Nine percent (10/108) of pathology reports utilized the terminology the carcinoma "abuts the mandible," and 80% (8/10) of these cases exhibited mandibular invasion.

CONCLUSIONS

The accuracy of identifying mandibular invasion is 84%, indicating a certain degree of sampling error and variability in interpretation. A precise pathologic definition of mandibular invasion should be applied during the interpretation of these specimens to minimize variability.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1721-1724, 2020.

Cyclooxygenase and CD147 expression in oral squamous cell carcinoma patient samples and cell lines

OBJECTIVES

In oral squamous cell carcinoma (OSCC), cyclooxygenases (COX-1 and COX-2) contribute to inflammation, and cluster of differentiation factor 147 (CD147) contributes to invasiveness, but their relationship has not been previously examined within a cohort of patients with OSCC or OSCC cell lines.

STUDY DESIGN

COX-2 and CD147 expression was determined by using immunohistochemistry on 39 surgical biopsy specimens of OSCC. Expression in tumor cells, stroma, and adjacent oral epithelium was characterized by using a visual grading system. COX-1, COX-2, and CD147 expression was determined in vitro by using OSCC cell lines (SCC25, BHY, and HN) and reverse transcriptase-quantitative polymerase chain reaction. Secretion of prostagladin E₂ (PGE₂) from OSCC cell lines was determined by using PGE₂ enzyme-linked immunosorbent assay.

RESULTS

Biopsy specimens showed higher COX-2 expression in tumor cells compared with stroma and adjacent epithelium (P < .05). There was no difference in CD147 expression among the tumor cells, stroma, and adjacent epithelium. In OSCC cell lines, there was a trend for COX-2 and CD147 gene expression to be coordinated. Interestingly, PGE₂ secretion was more closely related to COX-1 expression than to COX-2 expression.

CONCLUSIONS

COX-1, COX-2, and CD147 appear to be independently regulated in OSCC, potentially representing 2 therapeutic targets for future investigation. COX-1 expression in OSCC deserves further study because it may be an important determinant of PGE₂ secretion from OSCC cells.

Mandibular Invasion by Oral Squamous Cell Carcinoma: Clinicopathologic Features of 74 Cases

OBJECTIVES

(1) For patients with oral squamous cell carcinoma (OSCC) and mandibular invasion, to determine whether prior radiation to the head and neck region (PXRTHN) affects the density of osteoblasts, osteoclasts, or fibroblasts along the tumor interface invading the mandible and whether this is significantly associated with overall survival. (2) To identify clinicopathologic features that are associated with overall survival.

STUDY DESIGN

Case series with chart review.

SETTING

University of Missouri hospital.

SUBJECTS AND METHODS

Retrospective review of 74 cases with pathologically confirmed mandible invasion by OSCC and surgical treatment between January 1, 2005, and December 31, 2015. A board-certified anatomic pathologist reviewed the slides from all mandibulectomy cases.

RESULTS

The mean density of osteoclasts was 2.0 per linear mm among the patients with PXRTHN and 7.1 among those without PXRTHN ( P < .001). Positive soft tissue frozen section margin was significantly associated with overall survival on univariate analysis ( P < .001; hazard ratio [HR], 0.34; 95% CI, 0.19-0.62) and multivariate analysis ( P = .026; HR, 0.41; 95% CI, 0.19-0.90). Maximum tumor dimension was significantly associated with overall survival on univariate analysis ( P = .021; HR, 1.19; 95% CI, 1.03-1.38) and multivariate analysis ( P = .002; HR, 1.49; 95% CI, 1.16-1.93). Osteoclast, osteoblast, and fibroblast density were not associated with overall survival.

CONCLUSIONS

(1) Osteoclast density along the tumor front is significantly lower among patients with PXRTHN. Stromal cell density was not associated with overall survival. (2) Positive soft tissue frozen section margin and maximum tumor dimension are significantly associated with overall survival among patients with mandibular invasion by OSCC.

RANKL, Ephrin-Eph and Wnt10b are key intercellular communication molecules regulating bone remodeling in autologous transplanted goldfish scales

This study aimed to investigate the precise data of gene expression, functions, and chronological relationships amongst communication molecules involved in the bone remodeling process with an in vivo model using autologous transplanted scales of goldfish. Autotransplantation of methanol-fixed cell-free scales triggers scale resorption and regeneration, as well as helps elucidate the process of bone remodeling. We investigated osteoclastic markers, osteoblastic markers, and gene expressions of communicating molecules (RANKL, ephrinB2, EphB4, EphA4, Wnt10b) by qPCR, in situ hybridization for Wnt10b, and immunohistochemistry for EphrinB2 and EphA4 proteins to elucidate the bone remodeling process. Furthermore, functional inhibition experiments for the signaling of ephrinB2/Eph, ephrin/EphA4, and Wnt10b using specific antibodies, revealed that these proteins are involved in key signaling pathways promoting normal bone remodeling. Our data suggests that the remodeling process comprises of two successive phases. In the first absorption phase, differentiation of osteoclast progenitors by RANKL is followed by the bone absorption by mature, active osteoclasts, with the simultaneous induction of osteoblast progenitors by multinucleated osteoclast-derived Wnt10b, and proliferation of osteoblast precursors by ehprinB2/EphB4 signaling. Subsequently, during the second formation phase, termination of bone resorption by synergistic cooperation occurs, with downregulation of RANKL expression in activated osteoblasts and Ephrin/EphA4-mediated mutual inhibition between neighboring multinucleated osteoclasts, along with simultaneous activation of osteoblasts via forward and reverse EphrinB2/EphB4 signaling between neighboring osteoblasts. In addition, the present study shows that autologous transplantation of methanol-fixed cell-free scale is an ideal in vivo model to study bone remodeling.

Methanol Extract of Holarrhena antidysenterica Inhibits the Growth of Human Oral Squamous Cell Carcinoma Cells and Osteoclastogenesis of Bone Marrow Macrophages

Oral squamous cell carcinoma (OSCC) frequently invades mandibular bone, and outcomes for treatment with surgical resection are typically poor, ultimately resulting in death. Holarrhena antidysenterica L. (Apocynaceae), distributed throughout Sri Lanka and India, has been used as a folk remedy to treat various diseases. Treatment with methanol extract of H. antidysenterica bark (HABE) inhibited cell viability and BrdU incorporation and induced apoptotic cell death in Ca9-22 gingival and HSC-3 tongue SCC cells. Flow cytometric analysis indicated that HABE treatment preferentially induces apoptotic cell death via increasing the sub-G1 peak in Ca9-22 cells and cell cycle arrest at the G1 phase in HSC-3 cells. HABE treatment in the presence of zVAD-fmk, a pan-caspase inhibitor, rescued cell viabilities in both OSCC cell lines. The ratio of Bax to Bcl-2 increased with reductions in the Bcl-2 protein expression, and the activation of caspase 3 and subsequent cleavage of PARP was detected in HABE-treated Ca9-22 and HSC-3 cells. Furthermore, HABE treatment at noncytotoxic concentrations inhibited osteoclast formation in RANKL-stimulated bone marrow macrophages. Taken together, HABE possesses the inhibitory activity on the growth of OSCC cells and antiosteoclastogenic activity. Therefore, HABE may be a promising alternative and complementary agent for preventing and treating OSCC.

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.

Establishment of a xenograft model to explore the mechanism of bone destruction by human oral cancers and its application to analysis of role of RANKL

BACKGROUND

The molecular mechanism underlying bone invasion caused by oral squamous cell carcinoma (OSCC) is not well understood. To elucidate the molecular mechanism, the development of more suitable xenograft models mimicking human mandibular bone destruction by OSCC has been required.

MATERIALS AND METHODS

Human OSCC cell lines, HSC3, HSC3-C1, and HSC3-R2, were injected in the periosteal region of the mandible in athymic mice, and the bone destruction was analyzed. Receptor activators of nuclear factor κ-B ligand (RANKL) mRNA and protein expression levels were measured in the OSCC cell lines. Antibody that specifically neutralizes mouse RANKL and human RANKL, respectively, was injected into HSC3-cell-transplanted mice.

RESULTS

Transplantation of HSC3 cells induced mandibular bone destruction. Histological examination revealed numerous osteoclasts on the bone destruction surface. Fibroblastic cell intervention between the cancer nests and resorbing bone surface was observed in a similar fashion to those observed in human OSCC cases. The number of osteoclasts and fibroblasts was significantly correlated. Bone destruction induced by the transplantation of HSC3 cells was reduced by injection of an antibody that specifically neutralizes mouse RANKL. Transplantation of HSC3-R2 cells, which overexpresses RANKL, induced advanced bone destruction compared to that of HSC3-C1 cells, which only overexpress the empty vector.

CONCLUSIONS

We established a useful xenograft model for investigating the molecular mechanism underlying the bone destruction induced by OSCC in the jaw. This model will be used to investigate the precise roles of several cytokines synthesized by both cancer cells and fibroblastic cells in OSCC-associated bone destruction in the jaw.

Targeting RANKL in metastasis

Acting through its cognate receptor, receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) is an essential mediator of osteoclast function and survival. Preclinical data have now firmly established that blockade of tumor-induced osteoclastogenesis by RANKL inhibition will not only protect against bone destruction but will also inhibit the progression of established bone metastases and delay the formation of de novo bone metastases in cancer models. In patients with bone metastases, skeletal complications are driven by increased osteoclastic activity and may result in pathological fractures, spinal cord compression and the need for radiotherapy to the bone or orthopedic surgery (collectively known as skeletal-related events (SREs)). Denosumab, a fully human monoclonal antibody against RANKL, has been demonstrated to prevent or delay SREs in patients with solid tumors that have metastasized to bone. In addition to its central role in tumor-induced osteolysis, bone destruction and skeletal tumor progression, there is emerging evidence for direct pro-metastatic effects of RANKL, independent of osteoclasts. For example, RANKL also stimulates metastasis via activity on RANK-expressing cancer cells, resulting in increased invasion and migration. Pharmacological inhibition of RANKL may also reduce bone and lung metastasis through blockade of the direct action of RANKL on metastatic cells. This review describes these distinct but potentially overlapping mechanisms by which RANKL may promote metastases.

RANKL synthesized by both stromal cells and cancer cells plays a crucial role in osteoclastic bone resorption induced by oral cancer

The molecular mechanisms underlying bone destruction by invading oral cancer are not well understood. Using IHC, we demonstrated that receptor activator of nuclear factor-κB ligand (RANKL)-positive fibroblasts and cancer cells were located at sites of bone invasion in human oral cancers. HSC3 and HO-1-N-1, human oral cancer cell lines, expressed RANKL and stimulated Rankl expression in the UAMS-32 murine osteoblastic cell line. We discriminated the roles of RANKL synthesized by stromal cells and cancer cells in cancer-associated bone resorption by using species-specific RANKL antibodies against murine RANKL and human RANKL, respectively. Osteoclastogenesis induced by the conditioned medium of HSC3 and HO-1-N-1 cells in a co-culture of murine bone marrow cells and UAMS-32 cells was inhibited by the addition of antibodies against either mouse or human RANKL. HSC3-induced bone destruction was greatly inhibited by the administration of anti-mouse RANKL antibody in a xenograft model. HO-1-N-1-induced bone destruction was inhibited by the administration of either anti-mouse or anti-human RANKL antibody. Bone destruction induced by the transplantation of human RANKL-overexpressing cells (HSC3-R2) was greatly inhibited by the injection of anti-human RANKL antibody. The present study revealed that RANKL produced by both stromal and cancer cells is involved in oral cancer-induced osteoclastic bone resorption. These results provide important information for understanding the cellular and molecular basis of cancer-associated bone destruction and the mechanism of action underlying RANKL antibody (denosumab) therapy.

The role of osteocytes in bone resorption during orthodontic tooth movement

We investigated the roles of osteocytes in osteoclastic bone resorption during orthodontic tooth movement using the transgenic mice in which osteocytes can be specifically ablated. Because these transgenic mice express the receptor for diphtheria toxin on the cell surfaces of osteocytes, the injection of diphtheria toxin can ablate their osteocytes in vivo. Injection of diphtheria toxin into the transgenic mice significantly increased the number of ablated osteocytes in alveolar bone compared with that in wild-type mice with or without diphtheria toxin injection. Increased numbers of ablated osteocytes were observed from day 4 to day 12 after the injection in alveolar bones as well as in cortical bone of the tibiae. We applied the orthodontic force 4 days after the injection of diphtheria toxin, and the distance of tooth movement on day 12 was significantly smaller in transgenic mice than that in control mice. The numbers of osteoclasts and the quantity of eroded bone surface at the compression site were significantly reduced in the transgenic mice injected with diphtheria toxin than in control mice. These results provide in vivo demonstration of osteocyte involvement in osteoclastic bone resorption during orthodontic tooth movement.

Molecular pathways involved in crosstalk between cancer cells, osteoblasts and osteoclasts in the invasion of bone by oral squamous cell carcinoma

AIMS

This study investigates whether matrix metalloproteinases (MMPs), specifically MMP-2 and MMP-9, interacting with other molecules important in osteoblast differentiation and osteoclastogenesis, could play important roles in the invasion of bone by oral squamous cell carcinoma (OSCC).

METHODS

Supernatant (conditioned medium, CM) was collected from OSCC cell lines (SCC15 and SCC25), and from cultured osteoblasts (hFOB cell line and a primary culture, OB), and used for indirect co-culture: OSCC cells were treated with CM from osteoblasts and vice versa. Zymogenic activities of MMP-2 and -9, and protein quantities of all molecules studied, were detected by gelatine zymography and Western blotting, respectively. Real-time polymerase chain reaction (PCR) analysed mRNA of these molecules. Targeted molecules were examined by immunohistochemistry in tissue sections of bone-invasive OSCCs.

RESULTS

Zymogenic activities of both MMPs were increased in OSCC cells following culture with CM from hFOB: Twist1 protein expression was increased while Runx2 did not alter. The RANKL/OPG ratio, zymogen and protein expression of MMP-9 were increased in hFOB cells cultured with CM from OSCC lines, while zymogen expression of MMP-2 was decreased. Real-time PCR showed generally similar changes in expression of these molecules. All targeted molecules were expressed in invading malignant keratinocytes, and all but OPG were expressed in osteoclasts of clinical samples.

CONCLUSIONS

Crosstalk between different cell types appears to exist in the invasion of bone by OSCC. Understanding and ultimately interfering with the molecules involved may provide therapeutic approaches to inhibit such bone invasion.

Mandibular conservation in oral cancer

Surgery is one of the established modes of initial definitive treatment for a majority of oral cancers. Invasion of bony or cartilaginous structures by advanced upper aero-digestive tract cancer has been considered an indication for primary surgery on the basis of historic experience of poor responsiveness to radiation therapy [1]. The mandible is a key structure both in the pathology of intra-oral tumours and their surgical management. It bars easy surgical access to the oral cavity, yet maintaining its integrity is vital for function and cosmesis. Management of tumours that involve or abut the mandible requires specific understanding of the pattern of spread and routes of tumour invasion into the mandible. This facilitates the employment of mandibular sparing approaches like marginal mandibulectomy and mandibulotomy, as opposed to segmental or hemimandibulectomy which causes severe functional problems, as the mandibular continuity is lost. Accurate preoperative assessment that combines clinical examination and imaging along with the understanding of the pattern of spread and routes of invasion is essential in deciding the appropriate level and extent of mandibular resection in oral squamous cell carcinoma. Studies have shown that local control rates achieved with marginal mandibulectomy are comparable with that of segmental mandibulectomy. In carefully selected patients, marginal mandibulectomy is an oncologically safe procedure to achieve good local control and provides a better quality of life. This article aims to review the mechanism of spread, evaluation and prognosis of mandibular invasion, various techniques and role of mandibular conservation in oral squamous cell carcinoma.

CXCL13 activation of c-Myc induces RANK ligand expression in stromal/preosteoblast cells in the oral squamous cell carcinoma tumor-bone microenvironment

CXC chemokine ligand-13 (CXCL13) has been implicated in oral squamous cell carcinoma (OSCC) tumor progression and osteolysis. The tumor necrosis factor family member RANKL (receptor activator of NF-κB ligand), a critical bone resorbing osteoclastogenic factor, has an important role in cancer invasion of bone/osteolysis. Here, we show high-level expression of CXCL13 in primary human OSCC tumor specimens; however, human bone marrow-derived stromal (SAKA-T) and murine preosteoblast (MC3T3-E1) cells produce at very low level. Recombinant CXCL13 (0-15 ng/ml) dose dependently induced CXCR5 expression in SAKA-T and MC3T3-E1 cells. Conditioned media obtained from OSCC cell lines increased the RANKL expression and an antibody against the CXCL13 specific receptor, CXCR5 markedly decreased RANKL expression in these cells. Furthermore, CXCL13 increased hRANKL-Luc promoter activity. Superarray screening identified c-Myc and NFATc3 transcription factors upregulated in CXCL13-stimulated SAKA-T cells. Immunohistochemical analysis of OSCC tumors that developed in athymic mice demonstrated RANKL and NFATc3 expression in tumor and osteoblast cells, however, showed p-c-Myc expression specific to osteoblastic cells at the tumor-bone interface. We further identified NFATc3 expression, but not c-Myc activation in primary human OSCC tumor specimens compared with adjacent normal tissue. Also, CXCL13 significantly increased p-ERK1/2 in SAKA-T and MC3T3-E1 cells. siRNA suppression of c-Myc expression markedly decreased CXCL13-induced RANKL and NFATc3 expression in preosteoblast cells. Chromatin-immuno precipitation assay confirmed p-c-Myc binding to the hRANKL promoter region. In summary, c-Myc activation through CXCL13-CXCR5 signaling axis stimulates RANKL expression in stromal/preosteoblast cells. Thus, our results implicate CXCL13 as a potential therapeutic target to prevent OSCC invasion of bone/osteolysis.

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

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

Ultrastructual morphology of juvenile psammomatoid ossifying fibroma

We investigated the ultrastructural morphology of the hard tissue in a fibro-osseous lesion. Bone samples were obtained from a juvenile psammomatoid ossifying fibroma and were observed under a scanning electron microscope. The lesion had a spongy lamellar structure containing bony tissue. On histological examination, resorbing preexisting lamellar bone associated with a large number of cathepsin K-positive osteoclasts was confirmed. Scanning electron microscopy revealed the bony material to have a cribriform structure and to indicate resorption related to osteoclasts throughout the tumor. These characteristic findings revealed the presence of active bony reconstruction and destruction in this lesion. The spongy calcified structure observed by scanning electron microscopy expressed the characteristic ground glass appearance in computed tomography of this patient. This remarkable activation of osteoclasts may deeply relate to characteristic calcified structure in this lesion. Observation of hard tissue structure under a scanning electron microscope may shed light on the pathology of fibro-osseous lesions in the head and neck.

Roles of interleukin-6 and parathyroid hormone-related peptide in osteoclast formation associated with oral cancers: significance of interleukin-6 synthesized by stromal cells in response to cancer cells

We investigated the roles of interleukin-6 (IL-6) and parathyroid hormone-related peptide (PTHrP) in oral squamous cell carcinoma (OSCC)-induced osteoclast formation. Microarray analyses performed on 43 human OSCC specimens revealed that many of the specimens overexpressed PTHrP mRNA, but a few overexpressed IL-6 mRNA. Immunohistochemical analysis revealed that IL-6 was expressed not only in cancer cells but also in fibroblasts and osteoclasts at the tumor-bone interface. Many of the IL-6-positive cells coexpressed vimentin. Conditioned medium (CM) derived from the culture of oral cancer cell lines (BHY, Ca9-22, HSC3, and HO1-u-1) stimulated Rankl expression in stromal cells and osteoclast formation. Antibodies against both human PTHrP and mouse IL-6 receptor suppressed Rankl in ST2 cells and osteoclast formation induced by CM from BHY and Ca9-22, although the inhibitory effects of IL6 antibody were greater than those of PTHrP antibody. CM derived from all of the OSCC cell lines effectively induced IL-6 expression in stromal cells, and the induction was partially blocked by anti-PTHrP antibody. Xenografts of HSC3 cells onto the periosteal region of the parietal bone in athymic mice presented histology and expression profiles of RANKL and IL-6 similar to those observed in bone-invasive human OSCC specimens. These results indicate that OSCC provides a suitable microenvironment for osteoclast formation not only by producing IL-6 and PTHrP but also by stimulating stromal cells to synthesize IL-6.