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Background: Unicystic ameloblastoma, an odontogenic neoplasm, presents clinical and radiographic similarities with dentigerous and radicular cysts, non-neoplastic lesions. It is not always possible to reach a final diagnosis with the incisional biopsy, leading to inappropriate treatment. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of the detection of the BRAFV600E mutation in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cysts., Methods: Twenty-six archival samples were included, comprising eight unicystic ameloblastomas (UAs), nine dentigerous and nine radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR., Results: Although all UAs (8/8) showed positive uniform BRAFV600E staining along the epithelial lining length, the mutation was not confirmed by qPCR and Sanger sequencing in three samples. Positive staining for the BRAFV600E protein was observed in one dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed non-specific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay., Conclusions: The BRAFV600E antibody (clone VE1) IHC may show non-specific staining, but molecular assays may be useful for the diagnosis of unicystic ameloblastoma, in conjunction with clinical, radiological and histopathological features., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Ameloblastoma (AM) is a benign odontogenic neoplasm characterized by local invasiveness and recurrence. We compared the immunohistochemical expression of matrix metalloproteinases in different clinical types of AM as well as in normal odontogenic tissue., Methods: Thirteen cases of solid AMs, five cases of unicystic AM and eight pericoronal follicles (PF) were selected and subjected to immunohistochemical investigation for matrix metalloproteinase-1, matrix metalloproteinase-2 and matrix metalloproteinase-9 expressions., Results: The expressions of MMP-1 and MMP-2 were very high in the cytoplasm of cells throughout the entire epithelium and in fibroblasts from the adjacent connective tissue. MMP-9 expression was observed in the same location although with weaker staining. The Kruskal-Wallis test showed statistically significant differences in the epithelial expressions of MMP-1 and MMP-2; there was lower expression among solid AMs when compared with unicystic AM and PF. Compared to both types of AM, higher stromal expression of MMP-9 was found in PF., Conclusion: MMP-1, MMP-2 and MMP-9 seem to be associated with AM tumour behaviour as well as physiological tissue remodelling within PF., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Ameloblastoma is the most common benign odontogenic tumor in Japan. It is believed that it expands in the jaw bone through peritumoral activation of osteoclasts by receptor activator of nuclear factor kappa-B ligand (RANKL) released from the ameloblastoma, as in bone metastases of cancer cells. However, the clinical features of ameloblastoma, including its growth rate and patterns of invasion, are quite different from those of bone metastasis of cancer cells, suggesting that different underlying mechanisms are involved. Therefore, in the present study, we examined the possible mechanisms underlying the invasive expansion of ameloblastoma in the jaw bone. Expression levels of RANKL assessed by western blotting were markedly lower in ameloblastoma (AM-1) cells than in highly metastatic oral squamous cell carcinoma (HSC-3) cells. Experiments coculturing mouse macrophages (RAW264.7) with AM-1 demonstrated low osteoclastogenic activity, as assessed by tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cell formation, probably because of low release of RANKL, whereas cocultures of RAW264.7 with HSC-3 cells exhibited very high osteoclastogenic activity. Thus, RANKL release from AM-1 appeared to be too low to generate osteoclasts. However, AM-1 cultured directly on calcium phosphate-coated plates formed resorption pits, and this was inhibited by application of bafilomycin A1. Furthermore, vacuolar-type H+-ATPase (V-ATPase) and H+/Cl- exchange transporter 7 (CLC-7) were detected on the surface of AM-1 cells by plasma membrane biotinylation and immunofluorescence analysis. Immunohistochemical analysis of clinical samples of ameloblastoma also showed plasma membrane-localized V-ATPase and CLC-7 in the epithelium of plexiform, follicular and basal cell types. The demineralization activity of AM-1 was only 1.7% of osteoclasts demineralization activity, and the growth rate was 20% of human normal skin keratinocytes and HSC-3 cells. These results suggest that the slow expansion of several typical types of ameloblastomas in jaw bone is attributable to its slow growth and low demineralization ability.

Ameloblastoma is a benign but locally infiltrative odontogenic neoplasm. Although ameloblastomas rarely metastasise, recurrences together with radical surgery often result in facial deformity and significant morbidity. Development of non-invasive therapies has been precluded by a lack of understanding of the molecular background of ameloblastoma pathogenesis. When addressing the role of ERBB receptors as potential new targets for ameloblastoma, we discovered significant EGFR over-expression in clinical samples using real-time RT-PCR, but observed variable sensitivity of novel primary ameloblastoma cells to EGFR-targeted drugs in vitro. In the quest for mutations downstream of EGFR that could explain this apparent discrepancy, Sanger sequencing revealed an oncogenic BRAF V600E mutation in the cell line resistant to EGFR inhibition. Further analysis of the clinical samples by Sanger sequencing and BRAF V600E-specific immunohistochemistry demonstrated a high frequency of BRAF V600E mutations (15 of 24 samples, 63%). These data provide novel insight into the poorly understood molecular pathogenesis of ameloblastoma and offer a rationale to test drugs targeting EGFR or mutant BRAF as novel therapies for ameloblastoma., (© 2013 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.)

Morbidity and mortality from malignant neoplasms increases each year, and the average age of patients with first diagnosed decreases. The peak of incidence of malignant tumors of maxillofacial region falls on the elderly life. Not only age-related changes of the organism contribute in the development of this pathology, but also harmful habits. A comprehensive approach to solving the problem requires monitoring of this group of patients to identify risk factors for the development of pathologies in the oral and maxillofacial region.

Rho GTPases are proteins that regulate cell cycle, shape, polarization, invasion, migration, and apoptosis, which are important characteristics of normal and neoplastic cells. Rho GTPases expression has been reported in normal tooth germ and several pathologies; however, it has not been evaluated in ameloblastomas. The aim of this study was to analyze the expression and distribution of RhoA, RhoB, Rac1, and Cdc42 Rho GTPases in solid and unicystic ameloblastomas. Three-micrometer sections from paraffin-embedded specimens were evaluated by using an avidin-biotin immunohistochemical method with antibodies against the proteins mentioned above. RhoA and RhoB staining was observed in a high number of cells (P < 0.05) and greater intensity in non-polarized ones. Rac1 was not observed, and Cdc42 did not show any statistical differences between the number of non-polarized and basal positive cells (P > 0.05). Upon comparing the studied ameloblastomas, a higher number of positive cells in the unicystic variant was observed than that in the solid one (P < 0,05). The results obtained suggest that these GTPases could play a role in the ameloblastoma neoplastic epithelial cell phenotype determination (polarized or non-polarized), as well as in variant (solid or unicystic) and subtype (follicular or plexiform) determination. Furthermore, they could participate in solid ameloblastoma invasion mechanisms., (© 2011 John Wiley & Sons A/S.)

Objective: The aim was to evaluate immunoexpression of matrix metalloproteinases (MMPs) 1, 2, 7, 9, and 26 in calcifying cystic odontogenic tumor (CCOT)., Study Design: Ten cases of CCOT were assessed by immunohistochemical expression of MMPs 1, 2, 7, 9, and 26 in the parenchyma and stroma. Metalloproteinase immunoexpressions and their distribution pattern were semiquantitatively scored., Results: MMPs were expressed in the parenchyma and stroma in all cases of CCOT. Regarding the percentage of immunostained parenchymal cells, MMPs 1, 7, and 9 showed score 2 in 100% of cases. For MMP-2, there was a predominance of score 0 (90%), whereas for MMP-26 immunostaining was varied., Conclusions: The staining of these metalloproteinases, with the exception of MMP-2, suggests their contribution to tumor growth and expansion. The presence of these metalloproteinases in stromal cells reveals the active participation of these cells in the degradation of the extracellular matrix, contributing to the growth of the tumor studied., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Heparanase is an endoglycosidase that cleaves heparan sulfate (HS), thus participating in degradation and remodeling of the extracellular matrix (ECM). Heparanase up-regulation is correlated with lymph node and distant metastasis, microvessel density and reduced postoperative survival of cancer patients. In the present study, we carried out an immunohistochemical investigation of heparanase to extend and confirm present knowledge regarding its expression in ameloblastomas (AMs), which are characterized by locally aggressive behavior. Paraffin-embedded tissue specimens of 53 AMs were stained using an antibody against heparanase. Immunohistochemical reactivity for heparanase was detected in 94.3% of the AMs examined. Heparanase was expressed strongly in peripheral columnar cells and slightly in central stellate reticulum-like cells. Small tumor nests and budding epithelial branches showed a stronger staining pattern. Stromal cells were negative for heparanase, or showed diffuse expression. However, an enhanced positive immunoreaction was present specifically near osseous tissue and adjacent to the invasive front of tumor nests. Areas of cystic degeneration showed intense heparanase immunoreactivity. The enzyme may facilitate the function of HS-binding growth factors that elicit an angiogenic response and favor osteoclastogenesis in AM.

Ameloblastoma (AM) is recognized as a benign tumour but locally invasive with a high risk of recurrence. In vitro model systems for studying AM are limited due to the fact that AM cells grow poorly and begin to senesce early. Japanese researchers have reported the construction of an AM cell line, AM-1, by exposing cells to human papillomavirus 16 (HPV16) but retaining the potential of transformation. In this study, we used a retroviral infection method to over-express the human telomerase reverse transcriptase (hTERT) gene to acquire immortality of hTERT(+)-AM cells. Furthermore, it was revealed both by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot that the pathway of immortalization was loss of p16, not p53 or p21. Also, there was no evidence indicating that the hTERT(+)-AM cells underwent malignant transformation by the nude mouse tumorigenicity assay. Taken together, this hTERT-immortalized cell line may be a potentially valuable and reliable cell model for further study of the invasive properties of AM in vitro.

Background: Ameloblastoma is an odontogenic benign tumor characterized by local invasiveness and most of its local recurrences clinically result from local invasion. This study used matrix metalloproteinase-2 (MMP-2) inhibitor I (MMP-2I) to investigate the role played by MMP-2 activity in the local invasiveness of ameloblastoma., Methods: The cells and xenografts of ameloblastoma were treated with MMP-2I and treatment group were compared with the control group. In vitro, the invasive activity of tumor cells was assayed in transwell cell culture chamber. Gelatinolytic activity of gelatinases and MMP-2/tissue inhibitor of matrix metalloproteinase (TIMP-2) protein expression was detected using gelatin zymography and flow cytometry. The cell viability and adhesion were evaluated using methyl thiazol tetrazolium. In vivo, bilateral subrenal capsule xenograft transplantation of ameloblastoma was performed in 10 nude mice and the invasion of ameloblastoma into the renal parenchyma was observed., Results: Active-MMP-2 of conditioned media was significantly lower in treatment group than in the control group. Accordingly, potential of in vitro cell invasion, adhesion and in vivo tumor invasion were also significantly lower in the treatment group than in the control group., Conclusions: Inhibitor of MMP-2 activity suppressed the local invasive capability of ameloblastoma by decreasing MMP-2 activity. MMP-2 activity is in relation with invasive capacity of ameloblastoma.

The aim of this study was to compare the immunohistochemical expression of matrix metalloproteinases (MMPs) 1, 2, and 9 in odontogenic myxomas and dental germ papillae. Twelve cases of odontogenic myxoma and eight tooth germ specimens were selected for analysis of the immunohistochemical expression and the pattern of distribution of MMPs 1, 2, and 9 in extracellular matrix (ECM), as well as of the number of MMP-positive cells. MMP-2 was expressed only in the ECM of myxomas (p<0.05). No significant difference was observed between ECM immunoreactivity for MMP-9 in myxomas and dental papillae (p>0.05). MMP-1 immunoreactivity was detected in most myxoma cases at a proportion similar to that observed in dental papillae (p>0.05). A significant difference was observed in the number of immunoreactive cells in myxomas (p<0.05), MMP-1 being present at higher proportions than MMPs 2 and 9. There was a gradient in the expression of MMPs in the ECM and in neoplastic cells of odontogenic myxomas, with higher immunoreactivity to MMP-1 and lower immunoreactivity to MMP-9. Taken together, our results suggest the existence of a coordinated mechanism between MMPs 1, 2, and 9 that aimed at the efficient degradation of extracellular matrix in odontogenic myxomas.

Background: Ameloblastomas are odontogenic neoplasms characterized by local invasiveness. This study was conducted to address the role of matrix metalloproteinase-2 (MMP-2) in the invasiveness of ameloblastomas., Methods: Plasmids containing either MMP-2 siRNA or tissue inhibitor of metalloproteinase-2 (TIMP-2) cDNA were created and subsequently transfected into primary ameloblastoma cells. Zymography, RT-PCR, and Western blots were used to assess MMP-2 activity and expression of MMP-2 and TIMP-2, as well as protein levels., Results: Primary cultures of ameloblastoma cells expressed cytokeratin (CK) 14 and 16, and MMP-2, but only weakly expressed CK18 and vimentin. MMP-2 mRNA and protein levels were significantly inhibited by RNA interference (P < 0.05). Both MMP-2 siRNA and TIMP-2 overexpression inhibited MMP-2 activity and the in vitro invasiveness of ameloblastoma., Conclusion: These results indicate that inhibition of MMP-2 activity suppresses the local invasiveness of ameloblastoma cells. This mechanism may serve as a novel therapeutic target in ameloblastomas pursuant to additional research.

Background: To evaluate roles of mitogen-activated protein kinases (MAPKs) in oncogenesis and cytodifferentiation of odontogenic tumors, expression of phosphorylated JNK (p-JNK), p38 MAPK (p-p38 MAPK), and ERK5 (p-ERK5) was analyzed in ameloblastic tumors as well as in tooth germs., Methods: Ten tooth germs, 47 ameloblastomas, and 5 malignant ameloblastic tumors were examined immunohistochemically with the antibodies against p-JNK, p-p38 MAPK, and p-ERK5., Results: Immunoreactivity for p-JNK was detected in epithelial or neoplastic cells detached from the basement membrane in 7 tooth germs and 7 ameloblastomas, and the expression levels of p-JNK in ameloblastic tumors were significantly lower than that in tooth germs. Expression of p-p38 MAPK was found in epithelial or neoplastic cells in tooth germs and ameloblastic tumors except for two ameloblastomas, and increased expression was found in keratinizing cells of acanthomatous ameloblastomas. The expression level of p-p38 MAPK in ameloblastomas was significantly higher than the levels in tooth germs and malignant ameloblastic tumors. Immunoreactivity for p-ERK5 was found predominantly in epithelial or neoplastic cells near the basement membrane in tooth germs and ameloblastic tumors. The expression levels of p-ERK5 in ameloblastic tumors were slightly higher than that in tooth germs, and plexiform ameloblastomas showed significantly higher p-ERK5 expression than follicular ameloblastomas., Conclusion: Expression of p-JNK, p-p38 MAPK, and p-ERK5 in tooth germs and ameloblastic tumors suggests that these MAPK signaling pathways contribute to cell proliferation, differentiation, or apoptosis in both normal and neoplastic odontogenic tissues. Altered expression of these phosphorylated MAPKs in ameloblastic tumors may be involved in oncogenesis and tumor cell differentiation.

The aim of the present study was to examine the expression of inducible nitric oxide synthase (iNOS) in osteosarcoma of the jaw, and its relationship with tumour angiogenesis and clinicopathological characteristics. Streptavidin peroxidase immunohistochemical staining was used to detect the expression level of iNOS and CD34 in paraffin-embedded samples from 25 patients. Osteosarcoma of the jaw was associated with overexpression of iNOS, which correlated with tumour microvessel density (MVD). iNOS expression correlated with the size, pathological grade and clinical stage of the osteosarcoma, and also with clinicopathological characteristics such as primary occurrence or recurrence of tumours. There was no correlation with metastasis. iNOS may promote tumour angiogenesis in osteosarcoma of the jaw, and so may represent an important target in anti-tumour therapy.

Background: To evaluate the roles of angiogenic factors in the development and progression of odontogenic tumors, expression of platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) and of angiopoietins in ameloblastic tumors as well as in tooth germs., Methods: Tissue specimens of 11 tooth germs, 44 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against PD-ECGF/TP and angiopoietin-1 and -2., Results: Immunohistochemical reactivity for PD-ECGF/TP was detected in mesenchymal cells in tooth germs and stromal cells in ameloblastic tumors, and the level of immunoreactivity for PD-ECGF/TP was significantly higher in ameloblastomas than in tooth germs. Granular cell ameloblastomas showed PD-ECGF/TP reactivity in granular neoplastic cells as well as in stromal cells. Immunoreactivity for angiopoietin-1 and -2 was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and in benign and malignant ameloblastic tumors. Malignant ameloblastic tumors had decreased angiopoietin-1 reactivity and ameloblastic carcinomas had increased angiopoietin-2 reactivity as compared with the respective levels in tooth germs and ameloblastomas. Immunohistochemical reactivity for angiopoietin-2 was slightly higher in follicular ameloblastomas than in plexiform ameloblastomas., Conclusion: Expression of PD-ECGF/TP and angiopoietin-1 and -2 in tooth germs and ameloblastic tumors suggests that these angiogenic factors participate in tooth development and odontogenic tumor progression by regulating angiogenesis. Altered expression of PD-ECGF/TP and angiopoietins in ameloblastic tumors may be involved in oncogenesis, malignant potential, and tumor cell differentiation.

Background: To evaluate the roles of matrix-degrading proteinase regulators in progression of odontogenic tumors, expression of membrane-bound matrix metalloproteinase (MMP) MT1-MMP, MMP inhibitor RECK and MMP inducer EMMPRIN was analyzed in ameloblastic tumors as well as in tooth germs., Methods: Tissue specimens of 11 tooth germs, 40 ameloblastomas, and five malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against MT1-MMP, RECK, and EMMPRIN., Results: Immunohistochemical reactivity for MT1-MMP, RECK and EMMPRIN was detected predominantly in odontogenic epithelial cells near the basement membrane in tooth germs and benign and malignant ameloblastic tumors. The level of immunoreactivity for MT1-MMP was slightly higher in benign and malignant ameloblastic tumors than in tooth germs. RECK expression was lower in ameloblastomas than in tooth germs. Follicular ameloblastomas showed significantly lower expression of RECK than plexiform ameloblastomas, and immunoreactivity for RECK in acanthomatous ameloblastomas was slightly lower than that in other cellular variants., Conclusion: Expression of MT1-MMP, RECK and EMMPRIN in tooth germs and ameloblastic tumors suggests that these normal and neoplastic epithelial components control MMP-dependent extracellular matrix (ECM) degradation during tooth development and tumor progression via epithelial-mesenchymal interactions.

Ameloblastoma is the most common odontogenic neoplasm, particularized by its local invasiveness. Heparanase is the endo-glucuronidase enzyme that specifically cleaves heparan sulfate, the important modulator of extracellular matrix, and related to invasion of tumor cells. In this study, we addressed to show the gene expression and localization of heparanase in ameloblastoma. Immunohistochemistry and in situ hybridization of heparanase were carried out in 23 ameloblastomas. Strong expression of heparanase at both mRNA and protein levels was detected in all ameloblastomas studied. Small tumor nests and budding epithelial branches showed stronger staining pattern and the stromal tissues at the immediate vicinity of the tumor nests with strong heparanase expression were loose and edematous. Cystic areas and squamous metaplastic areas of the tumor showed intense staining with heparanase antibody proposing the implication of heparanase in these processes. These results suggest the possible contribution of heparanase in the local invasiveness and secondary morphologic changes of ameloblastoma.

Aims: Ameloblastoma is an odontogenic neoplasm characterized by local invasiveness and recurrence. In this study we analysed the role played by matrix metalloproteinases (MMPs) in the local invasiveness of ameloblastoma. We also attempted to establish a relationship between the presence of MMPs and the proliferative activity of ameloblastoma cells., Methods and Results: Immunohistochemistry was carried out to detect different MMPs in formalin-fixed paraffin-embedded samples of human ameloblastoma. Immunohistochemistry, however, does not establish whether a given MMP is latent or active. To address this point, we carried out biochemical methods, namely zymography and Western blotting. Our results showed expression of latent and active forms of MMPs 1, 2 and 9 in ameloblastoma. These enzymes may digest bone matrix and release mitogenic factors, which would increase tumour proliferation. This possibility prompted us to study the proliferation of ameloblastoma cells located in close proximity to bone. Silver-stained nucleolar organizer region morphometry revealed that ameloblastoma cells in the vicinity of bone show increased proliferation, when compared with controls., Conclusions: Our results suggest an interdependent mechanism involving MMPs and proliferation of ameloblastoma cells, which may contribute to the local invasiveness of this tumour.

Objective: To detect the expression of a disintegrin-like and metalloproteinase (ADAM) 8 and 12 gene in the giant cell lesions of jaw and to study their effects on the histogenesis of cells in these lesions., Methods: ADAM8 and ADAM12 was detected by immunohistochemistry (SP) in 40 paraffin-embedded specimens of central giant cell lesions of jaw, 10 peripheral giant cell lesions, 9 cherubisms, 6 aneurysmal bone cysts., Results: ADAM8 and ADAM12 were positive in the cytomembrane and cytoplasm of all multinucleated giant cells and some round mononuclear cells of the lesions; ADAM12 was positive for some spindle mononuclear stromal cells in central and peripheral giant cell lesions., Conclusions: Multinucleated giant cells probably originated from the fusion of the round mononuclear cells, and ADAM8 and ADAM12 were involved in this process. In addition, ADAM12 might play a role in the maturation of spindle mononuclear stromal cells.

Background: To clarify the roles of rat sarcoma (Ras)/mitogen-activated protein kinase (MAPK) signaling pathway in oncogenesis and cytodifferentiation of odontogenic tumors, K-Ras gene status and expression of Ras, Raf1, MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)1, and ERK1/2 proteins were analyzed in ameloblastomas as well as in tooth germs., Methods: Paraffin sections of 10 tooth germs and 46 benign and 6 malignant ameloblastomas were examined immunohistochemically for the expression of K-Ras, Raf1, MEK1, and ERK1/2. Frozen tissue samples of 22 benign ameloblastomas and 1 malignant (metastasizing) ameloblastoma were analyzed by direct DNA sequencing to detect K-Ras gene alteration., Results: Immunohistochemical reactivity for K-Ras, Raf1, MEK1, and ERK1/2 was detected in both normal and neoplastic odontogenic epithelium, and these molecules were reactive chiefly with odontogenic epithelial cells neighboring the basement membrane. Plexiform ameloblastomas showed slightly stronger expression of these Ras/MAPK signaling molecules than follicular ameloblastomas. Keratinizing cells and granular cells showed decreased reactivity for the signaling molecules. Basal cell ameloblastomas showed slightly stronger reactivity for the signaling molecules than did the other subtypes. K-Ras immunoreactivity in malignant ameloblastomas was lower than that in dental lamina of tooth germs. Direct DNA sequencing showed a GGT to GCT point mutation at codon 12 of K-Ras gene in one ameloblastoma., Conclusion: Expression of K-Ras, Raf1, MEK1, and ERK1/2 in tooth germs and ameloblastomas suggests that Ras/MAPK signaling pathway functions to regulate cell proliferation and differentiation in both normal and neoplastic odontogenic epithelium. K-Ras gene status implied that K-Ras mutations might play a minor role in oncogenesis of odontogenic epithelium.

Objective: To study the expression of telomerase reverse transcriptase (hTERT) and bcl-2 in ameloblastoma (AB), METHODS: hTERT mRNA in 54 cases of AB (primary AB 31 cases, recurrent AB 17 cases, malignant AB 4 cases) and 7 cases of oral normal mucosa was detected by in situ hybridization, and bcl-2 by S-P method., Results: The expression of hTERT mRNA was negative or weak in normal oral mucosa (14.3%), moderate or strong in AB (94.4%). There was a significant difference in these two groups (P < 0.001). The difference between the expressions of hTERT in primary, recurrent and malignant AB was significant (P < 0.05). The positive ratio of bcl-2 in AB and normal oral mucosa was respectively 88.0%, 44.4%. There was a significant statistical difference in these two groups (P < 0.001). hTERT mRNA was stronger in recurred or malignantly transformed AB (P < 0.05)., Conclusion: The expression of hTERT and bcl-2 is stronger in recurred or malignantly transformed AB, and it could be used as an indicator of AB prognosis. Telomerase activity and bcl-2 expression play an important role in genesis and development of AB.

Background: To evaluate the roles of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in tumor progression, expression of MMP-1, -2 and -9 and TIMP-1 and -2 was analyzed in ameloblastomas as well as tooth germs., Methods: Frozen tissue sections of seven tooth germs and 22 ameloblastomas were immunohistochemically examined using anti-MMP-1, -2 and -9 and anti-TIMP-1 and -2 antibodies., Results: MMP-1, -2 and -9 and TIMP-1 and -2 were expressed strongly in mesenchymal components of tooth germs, and stromal cells of ameloblastomas. Immunoreactivity for MMP-9 in stromal cells of ameloblastomas was significantly stronger than in mesenchymal cells of dental follicles and dental papillae. Dental laminae showed weak MMP-2 expression in six tooth germs, MMP-9 expression in two tooth germs and TIMP-1 expression in six tooth germs. Some tumor cells showed weak MMP-2 expression in 19 ameloblastomas, MMP-9 expression in four ameloblastomas and TIMP-1 expression in all cases. TIMP-2 reactivity was prominently found in basement membrane zones of dental laminae in tooth germs, and tumor cell islands or nests in ameloblastomas., Conclusion: Expression of MMPs and TIMPs was considered to be associated with interactions between epithelial cells and mesenchymal components in normal and neoplastic odontogenic tissues; these molecules might play a role in regulation of tumor progression in ameloblastomas as well as regulation of developmental processes in tooth germs.

Jaw cyst lining cells have an active transporting mechanism for Na+ ion and K+ion, a secreting mechanism and a selecting mechanism, and they allow permeation of electrolytes, lipids and protein into cysts. The components within the cysts have a controlling metabolism, and keep the system stable. Tumour wall cells of cystic ameloblastoma have only a passive transporting mechanism for various substances. Their nature differs from that of jaw cyst lining cells.

The myxoma of the jaws represent 8% of the odontogenic tumours in our series (324 cases). The 5 cases described here were studied by histoenzymological and electron microscopic methods. The first method demonstrated in the majority of tumoral cells a high level of activity of alkaline phosphatases and ATPases similar to that noted in odontoblasts of the dental pulp. In addition, an acid phosphatase activity was also present in numerous cells but usually at a low intensity. Ultrastructurally, the tumour was composed of 3 main cellular types: young round cells with numerous ribosomes; stellate secretory cells with well-developed granular ergastoplasma and Golgi apparatus; fusiform cells with characteristics of fibroblasts. Some macrophages and myofibroblasts were also present. The intercellular substance was granulofilamentous and in one of our cases calcifications were obvious upon some collagen fibers. All these results seem to corroborate the hypothesis of odontogenic nature of the tumour. Early odontogenic induction induces the transformation of fibroblasts into cells with enzymatic activities similar to those of odontoblasts and the calcification of collagen fibers seen in one of our cases would express an early mineralization.

An histoenzymological study comprising oxidative enzymes, diaphorases, acid and alkaline phosphatases, naphtolesterases, referred to 60 biopsy and operation specimens. It showed interesting arguments for diagnosis and understanding of precancerous and cancerous lesions of the oral mucosa and also of ameloblastomas of jaws. The enzymatic activities of precancerous and cancerous oral lesions were compared with those of normal buccal mucosa and epidermis, benign hyperkeratosis (activities similar to those of the epidermis) and lichen planus. In severe dysplasia and epidermoid carcinoma, numerous variations of oxidative, esterase and acid phosphatase activities were seen from one cell to another. But this pattern was non conclusive for the diagnosis, a similar one being found in inflammatory lesions and especially in the lichen planus. In lobules of invasive carcinoma, the strong enzymological activities (particularly acid phosphatases, naphtolesterases) were correlated with a high degree of differentiation of the tumor and these enzymatic methods offered an interesting contribution for the fine evaluation of histoprognosis in malignant epithelial tumors. Among the lesions of jaws, radicular and dentigerous cysts had low enzymatic activities similar to those of normal buccal epithelium. The epidermoid cysts (keratocysts), because of their highly differentiated keratinization, like benign hyperkeratosis, had the same enzymatic activities as epidermis. Peculiar were the enzymatic activities of common ameloblastoma; they differed from those of other lesions of squamous tissues (low oxidative activities without decreasing gradient). Besides, round epithelial clumps, the stroma showed a high and widespread alkaline phosphatase activity. Thus, this peculiar stromal activity may be useful to differentiate ameloblastoma from the other epidermoid cysts of the jaws. In the other hand, such a constatation suggests a low degree of odontogenic induction.

A histoenzymological study was carried out on 41 tissue specimens removed at biopsy and for surgical operations of the following lesions: benign hyperkeratosis, lichen planus, severe epithelial dysplasia, carcinoma in situ, epidermoid carcinoma, radicular cyst, odontogenic keratocyst and ameloblastoma. The purpose of this study was to study some possibly significant variations in levels of activities of oxidative enzymes, diaphorases, acid phosphatases and Naphthol esterases in such lesions (normal oral mucosa and epidermis serving as controls). In the lesions of the oral mucosa, these histoenzymological variations were not sufficiently characteristic to contribute to histological diagnosis. In lichen planus, some vacuolated or necrotic basal cells lacked enzyme activities, whereas in the upper layers, enzyme activities were irregularly present. Benign hyperkeratosis showed enzymatic activities similar to those of the normal epidermis, namely high oxidative activities particularly prominent in basal cells and in granular layer, and esterase activity beneath the keratinized layer. In severe epithelial dysplasia, carcinoma in situ and epidermoid carcinoma, numerous variations of activities of oxidative enzymes, esterases and acid phosphatase were seen from one cell to the other. In cystic diseases of jaws, enzymatic activities were equally nonspecific in the epithelial lining of the radicular cyst and the odontogenic keratocyst (activities similar to those of normal oral epithelium and epidermis, respectively). But in common ameloblastoma, there was diffuse uniformly low oxidative enzymatic activities in the epithelium and high widespread activity of alkaline phosphatase in the stroma. The latter may be useful in differentiating the cystic acanthomatous variety of ameloblastoma from odontogenic keratocysts of the jaws.

The activity and electrophoretic mobility of 1-naphthyl acetate esterases in cystic fluids and cystic tissues of ameloblastomas, follicular and apical cysts were examined. The cystic fluids showed lower activities than sera but had very similar patterns on the electrophoretogram. The activity levels of the three kinds of cystic fluids were not statistically significantly different. The fluid esterases may have originated from serum but they were not produced by the cystic lining tissue. Ameloblastoma tissues showed the highest activity per wet weight and per mg protein of the three kinds of cyst lesions (P less than 0.05). On the electrophoretogram, the esterase-I activity constituted 41% of the total activity in ameloblastomas, whereas in follicular cysts and apical cysts the esterase-I activity constituted 32% and 24% of the total activity, respectively.

An histoenzymological study (including oxidative enzymes, diaphorases, acid and alkaline phosphatases and naphtolesterases) of 41 biopsy and operation specimens revealed interesting factors in the diagnosis of some lesions of the buccal mucosa, and also of cysts and ameloblastomas of the jaw. When compared with normal buccal mucosa and epidermis, the enzymatic activities found in the oral lesions, fell into three different types. In non dysplasic leukoplakia, enzymatic activities were found that were similar to those of the epidermis (high oxidative activities, particularly prominent in basal cells and in the granular layer and esterasic activity beneath the keratinised layer). In lichen planus, some vacuolized or necrotic basal cells occurred which lacked enzymatic activity. In the upper layers, the distribution of the enzymes was irregular. In severe dysplasia and epidermoid carcinoma, numerous variations of oxidative, esterasic and acid phosphatase activities were seen from one cell to another. Among the lesions of the jaws, radicular cysts as well as dentigerous cysts, had low enzymatic activities, similar to those of normal buccal epithelium. The epidermoid cysts (keratocysts), because of their highly differentiated keratinization, like leukoplakia, had the same enzymatic activities as epidermis. The enzymatic activities of common ameloblastoma differed from those of malpighian tissues (low oxidative activities without decreasing gradient). Besides round epithelial nests, the stroma showed a high and widespread alkaline phosphatase activity, which indicated a low degree of odontogenic induction. Thus, this peculiar stromal activity may be useful in differentiating between cystic epidermoid varieties of ameloblastoma and the other epidermoid cysts of the jaws.