Calcifying epithelial odontogenic (Pindborg) tumor-associated amyloid consists of a novel human protein

Correlation of amyloid and ameloblast-associated proteins to odontogenic cysts and tumors: A cross-sectional study

Background and Aims

Odontogenic cysts and tumors often form hard and soft structures that resemble odontogenesis. It is well known that amyloid is produced in Pindborg tumors; however, it is still debatable whether it is also formed in other odontogenic tumors and cysts. This study aimed to detect the presence of amyloid in different odontogenic cysts and tumors in correlation to matrix proteins secreted during enamel formation; namely amelogenin and odontogenic ameloblast-associated protein.

Methods

This study included formalin fixed paraffin embedded tissue blocks of 106 different types of odontogenic cysts and tumors. Congo red and thioflavin T were performed to confirm the presence of amyloid; immunohistochemistry was used to detect amelogenin and odontogenic ameloblast-associated protein.

Results

Amyloid was detected in pindborg tumors (conventional), adenomatoid odontogenic tumors, odontogenic fibroma (Amyloid variant), follicular solid and unicystic ameloblastomas, radicular cysts, dentigerous cysts, dentinogenic ghost cell odontogenic tumor, ameloblastic fibroma, calcifying odontogenic cyst, and primordial Odontogenic tumor. Amelogenin was detected in 95.3% of the cases, while odontogenic ameloblast-associated protein was detected in 93.4% of the cases. The association between odontogenic ameloblast-associated protein and amyloid was highly significant at p < 0.01. However, there was no significant relationship between amelogenin and amyloid p > 0.05.

Conclusion

Although pindborg tumor is the bonafide example of amyloid deposition in odontogenic tumors, this study concluded that amyloid may be deposited in traces to massive amounts in various odontogenic cysts and tumors, and it is significantly linked to odontogenic ameloblast-associated protein but not amelogenin matrix protein, since all amyloid cases were odontogenic ameloblast associated protein positive.

The versatile roles of odontogenic ameloblast-associated protein in odontogenesis, junctional epithelium regeneration and periodontal disease

Junctional epithelium (JE) is a vital epithelial component which forms an attachment to the tooth surface at the gingival sulcus by the adhesion of protein complexes from its basal layer. Disruption of the JE is associated with the development of gingivitis, periodontal disease, and alveolar bone loss. Odontogenic ameloblast-associated (ODAM) is comprised of a signal peptide and an ODAM protein with 12 putative glycosylation sites. It is expressed during odontogenesis by maturation stage ameloblasts and is incorporated into the enamel matrix during the formation of outer and surface layer enamel. ODAM, as a secreted protein which is accumulated at the interface between basal lamina and enamel, mediates the adhesion of the JE to the tooth surface; and is involved with extracellular signalling of WNT and ARHGEF5-RhoA, as well as intracellular signalling of BMP-2-BMPR-IB-ODAM. ODAM is also found to be highly expressed in salivary glands and appears to have implications for the regulation of formation, repair, and regeneration of the JE. Bioinformatics and research data have identified the anti-cancer properties of ODAM, indicating its potential both as a prognostic biomarker and therapeutic target. Understanding the biology of ODAM will help to design therapeutic strategies for periodontal and dental disorders.

Non-calcifying Langerhans Cell Rich Variant of Calcifying Epithelial Odontogenic Tumor and Amyloid Rich Variant of Central Odontogenic Fibroma: A Unique Entity or a Spectrum?

Overlapping clinicopathological features of non-calcifying Langerhans cell rich variant of calcifying epithelial odontogenic tumor (NCLC-CEOT) and the amyloid rich variant of the central odontogenic fibroma (AR-COF) have been recognized recently. It is still under debate whether these two diseases are indeed one unique disease entity or belong to CEOT and COF, respectively. To clarify this issue, we have performed a literature review to compare the similarities and differences in clinicopathological features among NCLC-CEOT, AR-COF, classic CEOT, and classic COF. We aimed to investigate whether NCLC-CEOT and AR-COF might be the same and one distinctive disease entity, or a variant (or variants) of either CEOT or COF; or whether COF, NCLC-CEOT/AR-COF, and CEOT represented a histopathological spectrum of one disease. Our results indicate that NCLC-CEOT and AR-COF cases share many similar clinicopathological features. Thus, we suggest that they are the same disease entity. Due to nearly no reported recurrence of NCLC-CEOT/AR-COF cases, the conservative surgical treatment is appropriate. The NCLC-CEOT/AR-COF cases show some overlapping clinicopathological features with COF rather than the CEOT cases. However, differences in the clinicopathological features are still recognized among the NCLC-CEOT/AR-COF, COF, and CEOT cases. Future research, particularly molecular biological studies, may further elucidate their relationships and assist proper classification of the NCLC-CEOT/AR-COF cases.

An Unusual Maxillary Tumor with Tubuloductal Epithelial Structures, Solid Epithelial Nests and Stromal Odontogenic Ameloblast-Associated Protein Deposits. Tubuloductal/Syringoid Variant of Central Odontogenic Fibroma with Amyloid?

Glandular tumors of jaw bones present, most often, histopathologic features of salivary gland and, rarely, of cutaneous glandular neoplasms. They are thought to originate from odontogenic epithelium. An unusual maxillary tumor presenting as a radiolucency in the periapical area of the right permanent lateral incisor of a 74-year-old male is presented causing root resorption. Preparations revealed occasionally branching tubular cords and ductal structures characterized, mostly, by a bilayer composed of luminal cuboidal to low columnar cytokeratin (CK) 7, Ber-EP4 and occasionally CK8/18 positive cells, and abluminal, CK5/6 positive, basal/basaloid cells revealing nuclear reactivity for p63/p40. Smooth muscle actin and calponin were negative, save for a single focus of calponin positive cells, confirming absence of myoepithelial support or epithelial mesenchymal transition. CK19 exhibited staining of both layers, the luminal being more intense. Eosinophilic secretory material and, occasionally, a luminal pellicle were decorated with CK8/18 and polyclonal carcinoembryonic antigen (CEA). CD1a identified only rare Langerhans' cells and Ki67 decorated 1-2% of abluminal cell nuclei. Small solid nests of epithelial cells were also present. Infrequently, an apparent transition of a nest into a tubular structure was appreciated. The partially inflamed stroma featured multiple hyalinized acellular deposits consistent with amyloid, as confirmed by bright orange Congo red reactivity with apple-green birefringence, which reacted with odontogenic ameloblast-associated (ODAM) protein antibody but not with antibodies for amelotin and secretory calcium-binding phosphoprotein proline-glutamine rich 1. Based on the above, the diagnosis of tubuloductal/syringoid variant of central odontogenic fibroma with ODAM amyloid is favored.

Stress Response Is the Main Trigger of Sporadic Amyloidoses

Amyloidoses are a group of diseases associated with the formation of pathological protein fibrils with cross-β structures. Approximately 5-10% of the cases of these diseases are determined by amyloidogenic mutations, as well as by transmission of infectious amyloids (prions) between organisms. The most common group of so-called sporadic amyloidoses is associated with abnormal aggregation of wild-type proteins. Some sporadic amyloidoses are known to be induced only against the background of certain pathologies, but in some cases the cause of amyloidosis is unclear. It is assumed that these diseases often occur by accident. Here we present facts and hypotheses about the association of sporadic amyloidoses with vascular pathologies, trauma, oxidative stress, cancer, metabolic diseases, chronic infections and COVID-19. Generalization of current data shows that all sporadic amyloidoses can be regarded as a secondary event occurring against the background of diseases provoking a cellular stress response. Various factors causing the stress response provoke protein overproduction, a local increase in the concentration or modifications, which contributes to amyloidogenesis. Progress in the treatment of vascular, metabolic and infectious diseases, as well as cancers, should lead to a significant reduction in the risk of sporadic amyloidoses.

Amyloid Signature Proteins in Feline Amyloidosis

In human amyloidoses, amyloid signature proteins (ASPs), such as serum amyloid P component (SAP) and apolipoprotein E (ApoE), are deposited in tissues together with amyloid fibrils and are implicated in the pathogenesis of amyloidosis. Few reports describe ASPs in animals. In this study, we examined feline amyloidosis and performed immunohistochemical and proteomic analyses of SAP, ApoE, apolipoprotein A-I (ApoAI) and apolipoprotein A-IV (ApoAIV). Ten cases of systemic amyloidosis, three cases of amyloid-producing odontogenic tumour and three cases of islet amyloidosis were used for immunohistochemistry (IHC) and/or proteomic analyses. IHC showed that ApoE was present in amyloid deposits in all samples. ApoAI and ApoAIV differed in the degree of co-deposition with amyloid depending on the type of amyloid and the affected organ. SAP was negative in all amyloid deposits. Proteomic analysis showed that ApoE was present in all samples, but ApoAI and ApoAIV were detected only in some samples and SAP was not detected in any samples. The observation that ApoE was detected in all types of amyloid suggests the involvement of ApoE in the development of feline amyloidosis. ASPs in feline amyloidosis are significantly different from those in human amyloidosis, suggesting that the involvement of ASPs in the pathological condition differs between animal species.

Amyloids: from Pathogenesis to Function

The term "amyloids" refers to fibrillar protein aggregates with cross-β structure. They have been a subject of intense scrutiny since the middle of the previous century. First, this interest is due to association of amyloids with dozens of incurable human diseases called amyloidoses, which affect hundreds of millions of people. However, during the last decade the paradigm of amyloids as pathogens has changed due to an increase in understanding of their role as a specific variant of quaternary protein structure essential for the living cell. Thus, functional amyloids are found in all domains of the living world, and they fulfill a variety of roles ranging from biofilm formation in bacteria to long-term memory regulation in higher eukaryotes. Prions, which are proteins capable of existing under the same conditions in two or more conformations at least one of which having infective properties, also typically have amyloid features. There are weighty reasons to believe that the currently known amyloids are only a minority of their real number. This review provides a retrospective analysis of stages in the development of amyloid biology that during the last decade resulted, on one hand, in reinterpretation of the biological role of amyloids, and on the other hand, in the development of systems biology of amyloids, or amyloidomics.

The clinical correlation of phosphatase and tensin homolog on chromosome 10, phosphorylation of AKT to an activated state, and odontogenic ameloblast-associated protein in gastrointestinal stromal tumors

BACKGROUND

Approximately 15% of gastrointestinal stromal tumors (GISTs) will not respond to tyrosine kinase inhibitors and drug resistance can develop over time. For refractory tumors, additional therapies are needed. Odontogenic ameloblast-associated protein (ODAM) is expressed in some epithelial malignancies and can correlate with clinical outcomes. This study evaluated ODAM and its relationship to phosphatase and tensin homolog on chromosome 10 (PTEN) and phosphorylation of AKT to an activated state (pAKT) in GISTs.

MATERIALS AND METHODS

Ninety-five distinct tumor specimens from 79 patients were identified. Morphologic features and clinical data were recorded for all tumors. Risk of recurrence was calculated using the Memorial Sloan-Kettering nomogram. Immunohistochemistry was performed using antibodies to ODAM, PTEN, and pAKT. Immunoreactivity was assessed for both cytoplasmic and nuclear expression. Staining patterns were correlated with clinical outcomes.

RESULTS

Increasing cytoplasmic ODAM staining correlated with a lower recurrence score (P = 0.002), a lower mitotic rate (P = 0.0001), and smaller tumor size (P = 0.038). Increasing pAKT cytoplasmic staining correlated with a higher recurrence score (P = 0.037) and a higher mitotic rate (P = 0.036). ODAM and pAKT expression in the nucleus was associated with tumor origin. PTEN nuclear expression increased with increasing mitotic rate. pAKT expression increased in the cytoplasm and nucleus in high-risk tumors.

CONCLUSIONS

Risk of recurrence correlated with cytoplasmic expression of ODAM and pAKT, whereas nuclear expression did not predict recurrence. The staining pattern for ODAM and pAKT in the cytoplasm may further clarify the risk of recurrence beyond the available nomograms. The increased expression of pAKT in the cytoplasm and nucleus of high-risk tumors suggests a potential target for systemic therapy.

Laminin γ2 knockout mice rescued with the human protein exhibit enamel maturation defects

The epithelial ameloblasts are separated from the maturing enamel by an atypical basement membrane (BM) that is enriched in laminin 332 (LM-332). This heterotrimeric protein (α3, ß3 and γ2 chains) provides structural integrity to BMs and influences various epithelial cell processes including cell adhesion and differentiation. Mouse models that lack expression of individual LM-332 chains die shortly after birth. The lethal phenotype of laminin γ2 knockout mice can be rescued by human laminin γ2 (LAMC2) expressed using a doxycycline-inducible (Tet-on) cytokeratin 14 promoter-rtTA. These otherwise normal-looking rescued mice exhibit white spot lesions on incisors. We therefore investigated the effect of rescue with human LAMC2 on enamel maturation and structuring of the atypical BM. The maturation stage enamel organ in transgenic mice was severely altered as compared to wild type controls, a structured BM was no longer discernible, dystrophic matrix appeared in the maturing enamel layer, and there was residual enamel matrix late into the maturation stage. Microtomographic scans revealed excessive wear of occlusal surfaces on molars, chipping of enamel on incisor tips, and hypomineralization of the enamel layer. No structural alterations were observed at other epithelial sites, such as skin, palate and tongue. These results indicate that while this humanized mouse model is capable of rescue in various epithelial tissues, it is unable to sustain structuring of a proper BM at the interface between ameloblasts and maturing enamel. This failure may be related to the atypical composition of the BM in the maturation stage and reaffirms that the atypical BM is essential for enamel maturation.

ODAM inhibits RhoA-dependent invasion in breast cancer

Odontogenic ameloblast-associated protein (ODAM) contributes to cell adhesion. In human cancer, ODAM is down-regulated, and the overexpression of ODAM results in a favourable prognosis; however, the molecular mechanisms underlying ODAM-mediated inhibition of cancer invasion and metastasis remain unclear. Here, we identify a critical role for ODAM in inducing cancer cell adhesion. ODAM induced RhoA activity and the expression of downstream factors, including Rho-associated kinase (ROCK). ODAM-mediated RhoA signalling resulted in actin filament rearrangement by activating PTEN and inhibiting the phosphorylation of AKT. When ODAM is overexpressed in MCF7 breast cancer cells and AGS gastric cancer cells that activate RhoA at high levels, it decreases motility, increases adhesion and inhibits the metastasis of MCF7 cells. Conversely, depletion of ODAM in cancer cells inhibits Rho GTPase activation, resulting in increased cancer migration and invasion. These results suggest that ODAM expression in cells maintains their adhesion, resulting in the prevention of their metastasis via the regulation of RhoA signalling in breast cancer cells. SIGNIFICANCE Breast cancer represents the first most frequent cancer, and the ratio of mortality is high in women. Of utmost importance for reducing risk by breast cancer are their anti-invasion mechanisms, particularly in the non-invasive cancer cells because metastasis is the principal cause of death among cancer patients. ODAM induced RhoA activity. ODAM-mediated RhoA signalling resulted in actin filament rearrangement, increased cell adhesion and inhibited the migration/invasion of MCF7 cells. These results suggest that ODAM expression maintains their adhesion, resulting in the prevention of their metastasis via the regulation of RhoA signalling in breast cancer cells.

Maturation and beyond: proteins in the developmental continuum from enamel epithelium to junctional epithelium

Enamel, covering the surface of teeth, is the hardest substance in mammals. It is designed to last a lifetime in spite of severe environmental challenges. Enamel is formed in a biomineralization process that is essentially divided into secretory and maturation stages. While the molecular events of enamel formation during the secretory stage have been elucidated to some extent, the mechanisms of enamel maturation are less defined, and little is known about the molecules present beyond the maturation stage. Several genes, all located within the secreted calcium-binding phosphoprotein (SCPP) gene cluster, were recently shown to be expressed during the developmental continuum from maturation stage ameloblasts to junctional epithelium (JE). This review introduces four such genes and their protein products, and presents our current state of knowledge on their roles, primarily in enamel formation and JE biology. The discovery of these proteins, and a more detailed analysis of their biological functions, will likely contribute to a more thorough understanding of the molecular mechanisms of enamel maturation and dentogingival attachment.

Benign odontogenic tumors versus histochemically related tissues: preliminary results from mid-infrared and solid-state nuclear magnetic resonance spectroscopy

Three types of human odontogenic tumors histologically classified as compound composite odontoma, ossifying fibroma, and Pindborg tumor were characterized using mid-infrared spectroscopy (mid-IR) and solid-state nuclear magnetic resonance (ssNMR). For comparison, human jawbone and dental mineralized tissues such as dentin, enamel, and dental cement were also characterized. The studies focused on the structural properties and chemical composition of pathological tissues versus histochemically related tissues. All analyzed tumors were composed of organic and mineral parts and water. Apatite was found to be the main constituent of the mineral part. Various components (water, structural hydroxyl groups, carbonate ions (CO(3)(2-)), and hydrogen phosphate ions (HPO(4)(2-))) and physicochemical parameters (index of apatite maturity and crystallinity) were examined. The highest organic/mineral ratio was observed in fibrocementoma, a finding that can be explained by the fibrous character of the tumor. The lowest relative HPO(4)(2-) content was found in odontoma. This tumor is characterized by the highest mineral crystallinity index and content of structural hydroxyl groups. The Pindborg tumor mineral portion was found to be poorly crystalline and rich in HPO(4)(2-). The relative CO(3)(2-) content was similar in all samples studied. The results of spectroscopic studies of odontogenic tumors were consistent with the standard histochemical analysis. It was shown that the various techniques of ssNMR and elaborate analysis of the mid-IR spectra, applied together, provide valuable information about calcified benign odontogenic tumors.

Establishment and characterization of a primary calcifying epithelial odontogenic tumor cell population

Calcifying epithelial odontogenic tumors (CEOTs) are rare neoplasms derived from dental tissue with the unique characteristic of calcifying amyloid-like material.

OBJECTIVES

To establish primary CEOT epithelial-derived cell populations, investigate the expression of enamel matrix proteins (EMPs), and identify potential ameloblastin (AMBN) and patched 1 (PTCH1) gene alterations.

MATERIALS AND METHODS

A 28-year-old patient with a lesion of the posterior maxilla, radiographically characterized by a radiolucency with well-defined borders containing mixed radiopacities, agreed to participate with informed consent. The patient's biopsy confirmed the diagnosis of CEOT, and a small representative tumor fragment was ascertained for cell culture. Explant cultures were established and used to establish primary cell populations. These were analyzed for morphology, cell proliferation, mineralization activity, expression of epithelial-associated markers (qRT-PCR and immunocytochemistry), and gene mutations of AMBN or PTCH1. DNA was extracted from tumor cells and gene coding and exon-intron boundaries overlapping fragments amplified. PCR products were bidirectional DNA sequenced and compared against reference sequence.

RESULTS

A CEOT cell population was established and proliferated in culture and could be maintained for several passages. Expression of EMPs, cytokeratin 14 and 17, and patched (PTCH1), as well as ALP activity, was detected. These cells also had the ability to mineralize, similar to the primary tumor. Two AMBN alterations were identified in the sample: c.1323G>A/A441A (rs7680880) and c.1344*+111delA. Two single-nucleotide polymorphisms were identified in the PTCH1 gene.

CONCLUSIONS

Our data support the establishment of a CEOT-derived cell population, which expresses known epithelial-associated proteins.

Odontogenic ameloblast-associated protein (ODAM) inhibits growth and migration of human melanoma cells and elicits PTEN elevation and inactivation of PI3K/AKT signaling

Background

The Odontogenic Ameloblast-associated Protein (ODAM) is expressed in a wide range of normal epithelial, and neoplastic tissues, and we have posited that ODAM serves as a novel prognostic biomarker for breast cancer and melanoma. Transfection of ODAM into breast cancer cells yields suppression of cellular growth, motility, and in vivo tumorigenicity. Herein we have extended these studies to the effects of ODAM on cultured melanoma cell lines.

Methods

The A375 and C8161 melanoma cell lines were stably transfected with ODAM and assayed for properties associated with tumorigenicity including cell growth, motility, and extracellular matrix adhesion. In addition, ODAM–transfected cells were assayed for signal transduction via AKT which promotes cell proliferation and survival in many neoplasms.

Results

ODAM expression in A375 and C8161 cells strongly inhibited cell growth and motility in vitro, increased cell adhesion to extracellular matrix, and yielded significant cytoskeletal/morphologic rearrangement. Furthermore, AKT activity was downregulated by ODAM expression while an increase was noted in expression of the PTEN (phosphatase and tensin homolog on chromosome 10) tumor suppressor gene, an antagonist of AKT activation. Increased PTEN in ODAM-expressing cells was associated with increases in PTEN mRNA levels and de novo protein synthesis. Silencing of PTEN expression yielded recovery of AKT activity in ODAM-expressing melanoma cells. Similar PTEN elevation and inhibition of AKT by ODAM was observed in MDA-MB-231 breast cancer cells while ODAM expression had no effect in PTEN-deficient BT-549 breast cancer cells.

Conclusions

The apparent anti-neoplastic effects of ODAM in cultured melanoma and breast cancer cells are associated with increased PTEN expression, and suppression of AKT activity. This association should serve to clarify the clinical import of ODAM expression and any role it may serve as an indicator of tumor behavior.

Immunohistochemical and biochemical evidence of ameloblastic origin of amyloid-producing odontogenic tumors in cats

Amyloid-producing odontogenic tumors (APOT) are rare, and in cats, the histogenesis of the amyloid remains undetermined. In the present study, APOTs in 3 cats were characterized by immunohistochemistry, and the amyloid components analyzed using tandem mass spectrometry. Antiameloblastin antibodies labeled both neoplastic epithelial cells and amyloid in all cases. Neoplastic epithelial cells had strong, diffuse immunoreactivity to antibodies against cytokeratin AE1/AE3, cytokeratin 14, and cytokeratin 19 in all cases and focal immunoreactivity to nerve growth factor receptor antibodies in 2 of 3 cases. Amyloid and some tumor stromal cells were weakly positive for laminin. Calretinin, amelogenin, S100, and glial fibrillary acidic protein antibodies did not label neoplastic epithelial cells or amyloid. Extracted amyloid peptide sequences were compared to the porcine database because the cat genome is not yet complete. Based on this comparison, 1 identical ameloblastin peptide was detected in each tumor. These results suggest that feline APOTs and the amyloid they produce are of ameloblastic lineage.

Expression of odontogenic ameloblast-associated protein, amelotin, ameloblastin, and amelogenin in odontogenic tumors: immunohistochemical analysis and pathogenetic considerations

Screening for expression of amelogenesis-related proteins represents a powerful molecular approach to characterize odontogenic tumors and investigate their pathogenesis. In this study, we have examined the presence and distribution of odontogenic ameloblast-associated protein (ODAM), amelotin (AMTN), ameloblastin (AMBN), and amelogenin (AMEL) by immunohistochemistry in samples of adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), developing odontoma, ameloblastoma, calcifying cystic odontogenic tumor (CCOT), ameloblastic fibroma (AF), myxoma, odontogenic fibroma (OF), and reduced enamel epithelia (REE). Positive results were obtained in those tumors with epithelial component, except for AF, OF, and ameloblastoma. ODAM was found around mineralized structures (dystrophic calcifications) and CEOT's amyloid, whereas AMTN stained the eosinophilic material of AOTs. The CCOT transitory cells to ghost cells were strongly positive with all proteins except AMEL, and the REE as well as odontomas showed immunoexpression for ODAM, AMTN, AMBN, and AMEL similar to those found in normal rat tooth germs. Based on these results, some histopathogenetic theories were formulated.

Cystic variant of calcifying epithelial odontogenic tumor

The calcifying epithelial odontogenic tumor is a rare benign odontogenic neoplasm of the jaw. Clinically, calcifying epithelial odontogenic tumor manifests as an intraosseous lesion (central type) in the majority of cases (95%). Extraosseous or peripheral lesions account for less than 5% of cases. Calcifying epithelial odontogenic tumor can be associated with an impacted tooth and give a radiographic simulation of dentigerous cyst. Most calcifying epithelial odontogenic tumors are solid in nature, histopathologically, and might have few cyst-like spaces within them. However, a true cystic calcifying epithelial odontogenic tumor is a rare possibility. We describe a case of a true cystic variant of calcifying epithelial odontogenic tumor in a 30-year-old male, which to our knowledge, is only the second reported case.

Odontogenic fibroma, including amyloid and ossifying variants

Sixty-five cases of odontogenic fibroma (OdonF) are herein presented having been segregated into peripheral, extra bony tumors (n = 40) and tumors arising in bone or centrally (n = 25). All cases were characterized microscopically by a fibrous proliferation that varied within and between cases in cellularity and collagen fibril diameter, with intermixed odontogenic epithelial islands and cords. All central lesions presented as well demarcated radiolucencies and resorption of contiguous tooth roots was a common finding. These intraosseous lesions were of the WHO type; the so-called nonWHO type was excluded as all lesions with this diagnosis were devoid of an epithelial component and could be reclassified as other soft tissue fibrogenic tumors. Neither the central tumors nor the peripheral lesions recurred following enucleation/curettage, with a mean follow-up of 4 and 3.4 years respectively. Three distinct microscopic variations were encountered in this series: (1) two cases of OdonF with giant cell reaction, (2) two instances of OdonF with ossifying fibroma; and (3) four instances of OdonF with odontogenic ameloblast-associated protein (ODAM), an amyloid-like protein found deposited adjacent to epithelial cords plus CD1a+/S-100+ Langerhans dendritic cells entwined around the epithelial element. A single instance of the odontogenic fibroma-like hamartoma/enamel hypoplasia syndrome has been included in this series.

Differential enamel and osteogenic gene expression profiles in odontogenic tumors

Odontogenic tumors occur within the jaw bones and may be derived from odontogenic epithelium or ectomesenchyme or contain active components of both tissue types. We investigated the gene expression profile of enamel matrix proteins (EMPs), genes related to osteogenesis, and the mineralization process in odontogenic tumor cell populations focusing on an ameloblastoma (AB-1), a keratocystic odontogenic tumor (KCOT-1), and a calcifying epithelial odontogenic tumor (CEOT-1). All cell populations were shown to be epithelial in origin by CK14 expression. All tested EMPs were expressed by all odontogenic tumor cell types, with higher transcript levels seen in the AB-1 population especially for AMEL, AMBN, and ODAM. CEOT-1 cell populations showed a greater content of ALP-positive cells as well as higher ALP mRNA levels. Using qRT-PCR, we found a higher expression of 8 genes in the CEOT-1 compared to the AB-1 and KCOT-1. In this study we demonstrated the establishment of AB-1, KCOT-1 and CEOT-1 cell populations. The unique gene expression profiles of AB-1, KCOT-1, and CEOT-1 cells and their interactions with the surrounding microenvironment may support their unique tumor development, progression, and survival.

ODAM Expression Inhibits Human Breast Cancer Tumorigenesis

We have posited that Odontogenic Ameloblast Associated Protein (ODAM) serves as a novel prognostic biomarker in breast cancer and now have investigated its potential role in regulating tumor growth and metastasis. Human breast cancer MDA-MB-231 cells were transfected with a recombinant ODAM plasmid construct (or, as a control, the plasmid vector alone). ODAM expression increased adhesion and apoptosis of the transfected MDA-MB-231 cells and suppressed their growth rate, migratory activity, and capability to invade extracellular matrix-coated membranes. Implantation of such cells into mouse mammary fat pads resulted in significantly smaller tumors than occurred in animals that received control cells; furthermore, ODAM-expressing cells, when injected intravenously into mice, failed to metastasize, whereas the control-transfected counterparts produced extensive lung lesions. Our finding that induction of ODAM expression in human breast cancer cells markedly inhibited their neoplastic properties provides further evidence for the regulatory role of this molecule in tumorigenesis and, consequently, is of potential clinical import.

Oral Masses in Two Cats

Incisional biopsies from the oral cavity of 2 adult cats were submitted for histological investigation. Cat No. 1 showed a solitary well-circumscribed neoplasm in the left mandible. Cat No. 2 demonstrated a diffusely infiltrating neoplasm in the left maxilla. Both tumors consisted of medium-size epithelial cells embedded in a fibrovascular stroma. The mitotic index was 0 to 1 mitosis per high-power field. The epithelial cells showed an irregular arrangement forming nests or streams in cat No. 1, whereas a palisading growth was noted in cat No. 2. Both tumors, especially that of cat No. 1, showed multifocal accumulations of amyloid as confirmed by Congo red staining and a distinct green birefringence under polarized light, which lacked cytokeratin immunoreactivity as well as and AL and AA amyloid immunoreactivity. In addition, the amyloid in cat No. 2 was positive for the odontogenic ameloblast-associated protein, formerly termed APin. In sum, both cats suffered from an amyloid-producing odontogenic tumor, but their tumors varied with respect to morphology and type of amyloid produced.

Biochemical and immunohistochemical characterization of the amyloid in canine amyloid-producing odontogenic tumor

The amyloid of canine amyloid-producing odontogenic tumor (APOT) was evaluated biochemically and immunohistochemically. The N-terminal amino-acid sequence of purified amyloid protein from a canine APOT was strikingly similar to the sequence in both rat ameloblastin and porcine sheathlin. Immunohistochemically, the amyloid in APOT from 9 dogs was strongly reactive with anti-rat ameloblastin, anti-porcine sheathlin, and anti-canine APOT amyloid and weakly reactive with anti-porcine amelogenin but negative for antibodies to cytokeratins, vimentin, desmin, alpha-smooth muscle actin, amyloid A, glial fibrillary acidic protein, or S100 protein. The neoplastic epithelial cells of APOT were focally reactive with antibodies to ameloblastin, sheathlin, amelogenin, and canine APOT amyloid. The similarity in amino-acid sequence of the amyloid protein of canine APOT to that of enamel proteins, such as ameloblastin, sheathlin, and amelogenin, and the expression of these antigens in both APOT amyloid and in the neoplastic cells suggest that the amyloid of canine APOT is derived from enamel proteins secreted by ameloblasts.

Inherent anti-amyloidogenic activity of human immunoglobulin gamma heavy chains

We have previously shown that a subpopulation of naturally occurring human IgGs were cross-reactive against conformational epitopes on pathologic aggregates of Abeta, a peptide that forms amyloid fibrils in the brains of patients with Alzheimer disease, inhibited amyloid fibril growth, and dissociated amyloid in vivo. Here, we describe similar anti-amyloidogenic activity that is a general property of free human Ig gamma heavy chains. A gamma(1) heavy chain, F1, had nanomolar binding to an amyloid fibril-related conformational epitope on synthetic oligomers and fibrils as well as on amyloid-laden tissue sections. F1 did not bind to native Abeta monomers, further indicating the conformational nature of its binding site. The inherent anti-amyloidogenic activity of Ig gamma heavy chains was demonstrated by nanomolar amyloid fibril and oligomer binding by polyclonal and monoclonal human heavy chains that were isolated from inert or weakly reactive antibodies. Most importantly, the F1 heavy chain prevented in vitro fibril growth and reduced in vivo soluble Abeta oligomer-induced impairment of rodent hippocampal long term potentiation, a cellular mechanism of learning and memory. These findings demonstrate that free human Ig gamma heavy chains comprise a novel class of molecules for developing potential therapeutics for Alzheimer disease and other amyloid disorders. Moreover, establishing the molecular basis for heavy chain-amyloidogenic conformer interactions should advance understanding on the types of interactions that these pathologic assemblies have with biological molecules.

Odontogenic Ameloblast Associated Protein as a Novel Biomarker for Human Breast Cancer

Odontogenic Ameloblast Associated Protein (ODAM) is a protein isolated in ameloblasts during odontogenesis. ODAM expression was identified in breast cancer, but its significance remains unknown. The purpose of this study is to determine if ODAM expression can serve as a prognostic marker and provide information regarding treatment in human breast cancer. Breast cancer patients were identified from our tumor registry from 1993 to 2003. Archived breast cancer tissue from 243 patients (stage 0 = 53, stage I = 51, stage II = 53, stage III = 47, stage IV = 39) was stained using monoclonal antibody for ODAM. Presence or absence of immunostaining was correlated with stage, histologic grade, response to chemotherapy, and survival using χ2 and logistic regression analyses. Tumor nuclear staining for ODAM increased with increasing group stage ( P < 0.001). Staining for ODAM did not correlate with histologic grade or chemotherapy ( P = 0.558, P = 0.093). Improved outcomes within each stage were noted with ODAM staining, statistically significant for stages 0, I, and II ( P < 0.001, P = 0.003, P = 0.003) and underpowered for stages III and IV ( P = 0.724, P = 0.059). Survival benefit associated with tumor nuclear staining increased with advancing stage ( P < 0.001). These results show that ODAM predicts survival in breast cancer. Research is ongoing to determine ODAM's clinical utility and role in carcinogenesis.

The SCPP gene repertoire in bony vertebrates and graded differences in mineralized tissues

The vertebrate tooth is covered with enamel in most sarcopterygians or enameloid in chondrichthyans and actinopterygians. The evolutionary relationship among these two tissues, the hardest tissue in the body, and other mineralized tissues has long been controversial. We have recently reported that specific combinations of secretory calcium-binding phosphoprotein (SCPP) genes are involved in the mineralization of bone, dentin, enameloid, and enamel. Thus, the early repertoire of SCPP genes would elucidate the evolutionary relationship across these tissues. However, the diversity of SCPP genes in teleosts and tetrapods and the roles of these genes in distinct tissues have remained unclear, mainly because many SCPP genes are lineage-specific. In this study, I show that the repertoire of SCPP genes in the zebrafish, frog, and humans includes many lineage-specific genes and some widely conserved genes that originated in stem osteichthyans or earlier. Expression analysis demonstrates that some frog and zebrafish SCPP genes are used primarily in bone, but also in dentin, while the reverse is true of other genes, similar to some mammalian SCPP genes. Dentin and enameloid initially use shared genes in the matrix, but enameloid is subsequently hypermineralized. Notably, enameloid and enamel use an orthologous SCPP gene in the hypermineralization process. Thus, the hypermineralization machinery ancestral to both enameloid and enamel arose before the actinopterygian-sarcopterygian divergence. However, enamel employs specialized SCPPs as structuring proteins, not used in enameloid, reflecting the divergence of enamel from enameloid. These results show graded differences in mineralized dental tissues and reinforce the hypothesis that bone-dentin-enameloid-enamel constitutes an evolutionary continuum.

Expression of odontogenic ameloblast-associated protein (ODAM) in dental and other epithelial neoplasms

We previously have communicated our discovery that the amyloid associated with calcifying epithelial odontogenic tumors is composed of N-terminal fragments of the structurally novel odontogenic ameloblast-associated protein designated ODAM. Subsequently, it was shown by other investigators that ODAM is expressed in rodent enamel organ and is likely involved in dental development. We now report that this molecule also is found in certain human tissues, principally the salivary gland and trachea, as evidenced by RNA array analysis and immunohistochemistry-utilizing antibodies prepared against synthetic ODAM-related peptides and recombinant protein. Notably, these reagents immunostained normal and malignant ameloblasts and other types of human neoplastic cells, including those of gastric, lung, and breast origin where the presence in the latter was confirmed by in situ hybridization using gene-specific molecular probes. Moreover, significant titers of anti-ODAM IgG antibodies were detected in the sera of patients with these malignancies. Our studies have provided the first evidence in humans for the cellular expression of ODAM in normal and diseased states. Based on our findings, we posit that ODAM is a developmental antigen that has an essential role in tooth maturation and in the pathogenesis of certain odontogenic and other epithelial neoplasms; further, we suggest that ODAM may serve as a novel prognostic biomarker, as well as a potential diagnostic and therapeutic target for patients with breast and other epithelial forms of cancer.

Isolation, identification and quantification of differentially expressed proteins from cancerous and normal breast tissues

BACKGROUND

Infiltrating ductal carcinoma (IDCA) is the most common type of breast cancer accounting for 85% of all invasive breast cancers.

METHODS

Forty tissue specimens comprising 20 pairs of normal and cancerous tissues were analysed. The tissues were homogenized and proteins were extracted using phosphate buffer. The protein extracts from each pair of cancerous and normal tissue were separated using sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the same gel. The protein profiles of both the tissues were compared, and the differentially expressed proteins that were detected at >70% in one or both of the tissue types were selected for protein identification analysis. Target proteins were excised and digested in situ with trypsin prior to liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. A protein that was present in both tissue types was further quantified using extracted ions chromatogram.

RESULTS

The proteins were grouped as down-regulated, up-regulated and unique proteins. Twenty-two proteins were identified and eight of the proteins were found unique to cancer. These proteins belong to various molecular classes, i.e. structural protein, hypothetical protein, cytoskeletal protein, enzyme, calcium binding protein and extracellular matrix protein. One extracellular matrix protein, namely collagen alpha-1(I) chain precursor was found unique to cancer. By virtue of its location on the cell surface and its function in cancer growth, this protein may be a biomarker candidate for breast cancer.

CONCLUSIONS

The proteins identified in this study were present in at least 70% of the tissues tested; therefore they should have significant roles in the development of IDCA.

SCPP gene evolution and the dental mineralization continuum

Many genes critical to vertebrate skeletal mineralization are members of the secretory calcium-binding phosphoprotein (SCPP) gene family, which has evolved by gene duplication from a single ancestral gene. In humans, mutations in some of these SCPP genes have been associated with various diseases related to dentin or enamel hypoplasia. Recently, systematic searches for SCPP genes of various species have allowed us to investigate the history of phylogenetically variable dental tissues as a whole. One important conclusion is that not all disease-associated SCPP genes are present in tetrapods, and teleost fish probably have none, even in toothed species, having acquired their complement of SCPP genes through an independent duplication history. Here, we review comparative analyses of mineralized dental tissues, with particular emphasis on the use of SCPPs, within and between tetrapods and teleosts. Current knowledge suggests a close relationship among bone, dentin, teleost fish enameloid (enamel-like hard tissue), and tetrapod enamel. These tissues thus form a mineralized-tissue continuum. Contemporary dental tissues have evolved from an ancestral continuum through lineage-specific modifications.

Characterization of Apin, a secreted protein highly expressed in tooth-associated epithelia

We previously reported expression of a protein by enamel organ (EO) cells in rat incisors, originally isolated from the amyloid of Pindborg odontogenic tumors called Apin. The aim of the present study was to further characterize the Apin gene and its protein in various species, assess tissue specificity, and clarify its localization within the EO. Northern blotting and RT-PCR revealed that expression of Apin was highest in the EO and gingiva, moderate in nasal and salivary glands, and lowest in the epididymis. The protein sequences deduced from the cloned cDNA for rat, mouse, pig, and human were aligned together with those obtained from four other mammal genomes. Apin is highly conserved in mammals but is absent in fish, birds, and amphibians. Comparative SDS-PAGE analyses of the protein obtained from bacteria, transfected cells, and extracted from EOs all indicated that Apin is post-translationally modified, a finding consistent with the presence of predicted sites for phosphorylation and O-linked glycosylation. In rodent incisors, Apin was detected only in the ameloblast layer of the EO, starting at post-secretory transition and extending throughout the maturation stage. Intense labeling was visible over the Golgi region as well as on the apices of ameloblasts abutting the enamel matrix. Apin was also immunodetected in epithelial cells of the gingiva which bind it to the tooth surface (junctional epithelium). The presence of Apin at cell-tooth interfaces suggests involvement in adhesive mechanisms active at these sites, but its presence among other epithelial tissues indicates Apin likely possesses broader physiological roles.

Odontogenic ameloblast-associated protein nature of the amyloid found in calcifying epithelial odontogenic tumors and unerupted tooth follicles

We have previously reported that the amyloid found in three patients with calcifying epithelial odontogenic tumors (CEOT) was composed of N-terminal fragments of a putative 153-residue protein specified by a gene designated FLJ20513 now known to represent exons 5 through 10 of the odontogenic ameloblast-associated protein (ODAM) locus that encodes a 279-residue polypeptide. Confirmation of the amyloidogenic potential of ODAM has resulted from analyses of four other cases where we found, in addition, a 74-residue segment specified by exon 4. Through preparation of ODAM-related synthetic peptides, it was possible to localize the fibril-forming region of this molecule, as well as generate a monoclonal antibody that reacted specifically with the amyloid associated with CEOT. Notably, we also detected green birefringent congophilic material in unerupted tooth follicles - a precursor of CEOT - and demonstrated through immunologic and chemical analyses the ODAM nature of the deposits. Our studies have provided further evidence for this unique form of odontogenic amyloid that we provisionally designate "AODAM".

[Benign epithelial odontogenic tumors]

The group of benign epithelial odontogenic tumors consists of the four member types of the ameloblastoma family (solid/multicystic, extraosseous/peripheral, desmoplastic, unicystic), squamous odontogenic tumors, calcifying odontogenic tumors, adenomatoid odontogenic tumors, and keratocystic odontogenic tumors, the former "keratocysts" that were recently reclassified by the World Health Organization and are now regarded as tumors. The latter are by far the most frequent tumors in this group, followed by solid/multicystic ameloblastoma. Although the etiology of these lesions is still unknown, a close relationship to normal tooth development is obvious, which is partially imitated by some tumors. Despite some similarities to each other, at least in part, the biological behavior of these lesions is quite different, as are treatment modalities. The diagnosis is essentially based on localization (intraosseous vs. extraosseous/peripheral) and histology, whereupon the correlation of histological findings with radiographic morphology may be of additional diagnostic value. Because of the range of variation, immunohistochemical investigations are not helpful in diagnosing a particular case.

Amyloid peptides and proteins in review

Amyloids are filamentous protein deposits ranging in size from nanometres to microns and composed of aggregated peptide beta-sheets formed from parallel or anti-parallel alignments of peptide beta-strands. Amyloid-forming proteins have attracted a great deal of recent attention because of their association with over 30 diseases, notably neurodegenerative conditions like Alzheimer's, Huntington's, Parkinson's, Creutzfeldt-Jacob and prion disorders, but also systemic diseases such as amyotrophic lateral sclerosis (Lou Gehrig's disease) and type II diabetes. These diseases are all thought to involve important conformational changes in proteins, sometimes termed misfolding, that usually produce beta-sheet structures with a strong tendency to aggregate into water-insoluble fibrous polymers. Reasons for such conformational changes in vivo are still unclear. Intermediate aggregated state(s), rather than precipitated insoluble polymeric aggregates, have recently been implicated in cellular toxicity and may be the source of aberrant pathology in amyloid diseases. Numerous in vitro studies of short and medium length peptides that form amyloids have provided some clues to amyloid formation, with an alpha-helix to beta-sheet folding transition sometimes implicated as an intermediary step leading to amyloid formation. More recently, quite a few non-pathological amyloidogenic proteins have also been identified and physiological properties have been ascribed, challenging previous implications that amyloids were always disease causing. This article summarises a great deal of current knowledge on the occurrence, structure, folding pathways, chemistry and biology associated with amyloidogenic peptides and proteins and highlights some key factors that have been found to influence amyloidogenesis.