Jaw bone remodeling at the invasion front of gingival squamous cell carcinomas

Comparative study of BMP-2 alone and combined with VEGF carried by hydrogel for maxillary alveolar bone regeneration

The effect of vascular endothelial growth factor (VEGF) combined with bone morphogenetic protein-2 (BMP-2) for bone regeneration is still controversial as to whether or not VEGF has a synergistic or additive effect. This study attempted to evaluate the synergistic effect of VEGF and BMP-2 compared to BMP-2 alone for maxillary alveolar bone regeneration using collagen sponge/hydrogel complex sheets in a canine model. After mixing BMP-2 and VEGF with a hyaluronic acid-based hydrogel (HAH), the collagen sponge/hydrogel complex was transplanted into maxillary alveolar bone defects (n=14) after the extraction of canine upper first molars on both sides. Bone regeneration was evaluated in three groups (control group without growth factors, experimental groups I and II with BMP-2 alone and BMP-2 and VEGF, respectively) using micro-computed tomography and histological staining. The total amount of new bone formations and bone mineral density were significantly higher in the group with BMP-2 only and the group with BMP-2 combined with VEGF than it in the control group. The area with positive staining of von Willebrand factor bone defect was significantly greater in the group with BMP-2 only and with dual growth factors than the control. BMP-2 released from the HAH promoted new bone formation. However, the combination of BMP-2 and VEGF did not show a synergistic or additive effect on bone regeneration at canine maxillary alveolar bone defects.

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.

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

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

Reduced syndecan-1 expression is correlated with the histological grade of malignancy at the deep invasive front in oral squamous cell carcinoma

BACKGROUND

Although many histopathological characteristics of oral squamous cell carcinoma (O-SCC) have been identified as prognostic factors, no factor is completely accurate and unequivocal. This study evaluated the association between the loss of syndecan-1 expression and the histological grade of malignancy at the deep invasive front in O-SCC.

METHODS

The expression of syndecan-1 at the invasive tumor front of O-SCC was examined immunohistochemically using archived tissue from 72 cases. The mean age of the patients was 62.5 years (range: 23-90 years) and the male-female ratio was 1.3:1 (41 men, 31 women). There were 26, 24, 11, and 11 cases classified as stages I-IV respectively. The correlation between the intensity of syndecan-1 immunostaining and the clinicopathological factors, especially the histological grade of malignancy at the deep invasive front (invasive front grade) was analyzed.

RESULTS

Of the 72 cases, seven (9.7%), 29 (40.3%), 36 (50.0%) showed strong, intermediate, and weak or negative syndecan-1 staining respectively. There were significant differences between syndecan-1 expression and prognosis, differentiation, and pattern of invasion at the deep invasive front. Moreover, the invasive front grade scores, based on the intensity of syndecan-1 staining, were 5.6 +/- 1.0, 8.0 +/- 2.1, and 10.2 +/- 2.3 points with strong, intermediate, and weak or negative intensity respectively; and the difference was significant (P < 0.0001). Patients with intermediate or strong intensity for syndecan-1 had significantly better prognoses than did those with negative or weak intensity (P = 0.0138).

CONCLUSION

This study demonstrated that the reduced expression of syndecan-1 seems to be a useful marker of histological malignancy at the deep tumor invasive front and may be a useful prognostic factor in O-SCC.

The relationship of the histologic grade at the deep invasive front and the expression of Ki-67 antigen and p53 protein in oral squamous cell carcinoma

BACKGROUND

Although many histopathologic characteristics of oral squamous cell carcinoma (O-SCC) have been identified as prognostic factors, accurate, and unequivocal factors have not been clearly identified. The purpose of this study was to evaluate a potential association between the histologic grade of malignancy at the deep invasive front and the expression of Ki-67 antigen and p53 protein in O-SCC.

METHODS

The expression of Ki-67 antigen and p53 at the invasive tumor front area of O-SCC was examined by immunohistochemistry of archived tissue from 62 cases. The mean age of patients was 60.7 years (range: 37-89) and the male-female ratio was 1.6:1 (38 men, 24 women). There were 20, 17, 14, and 11 cases classified as stage I to stage IV, respectively. The correlation between the intensity of immunostaining for Ki-67 antigen and p53 and the histologic grade of malignancy at the deep invasive front (invasive front grade, IFG) was analyzed. The expression of Ki-67 antigen and p53 in normal oral epithelia (10 cases) was also investigated.

RESULTS

The mean Ki-67 labeling index (LI) in the O-SCC samples was 32.8 +/- 12.0% (n = 62). The mean total score of IFG (IFG score) was 9.1 +/- 2.7 points (n = 62). There was a significant linear correlation between the IFG score and the Ki-67 antigen (gamma = 0.651, R2 = 0.596, P < 0.0001). Of 50 tumors examined, 27 (54.0%) exhibited p53-positive nuclear immunostaining. The staining patterns for Ki-67 antigen and p53 were similar. Both Ki-67-LI and p53-positive status were significantly correlated with the IFG scores.

CONCLUSION

The findings of this study demonstrate that overexpression of Ki-67 antigen and p53 at the deep tumor invasive front of O-SCC is associated with histologic grade of malignancy.