Differential enamel and osteogenic gene expression profiles in odontogenic tumors

Fluorescently Labeled Cetuximab-IRDye800 for Guided Surgical Excision of Ameloblastoma: A Proof of Principle Study

PURPOSE

Fluorescently labeled epidermal growth factor receptor (EGFR) antibodies have successfully identified microscopic tumors in multiple in vivo models of human cancers with limited toxicity. The present study sought to demonstrate the ability of fluorescently labeled anti-EGFR, cetuximab-IRDye800, to localize to ameloblastoma (AB) tumor cells in vitro and in vivo.

MATERIAL AND METHODS

EGFR expression in AB cells was confirmed by quantitative real-time polymerase chain reaction and immunohistochemistry. Primary AB cells were labeled in vitro with cetuximab-IRDye800 or nonspecific IgG-IRDye800. An in vivo patient-derived xenograft (PDX) model of AB was developed. The tumor tissue from 3 patients was implanted subcutaneously into immunocompromised mice. The mice received an intravenous injection of cetuximab-IRDye800 or IgG-IRDye800 and underwent imaging to detect infrared fluorescence using a Pearl imaging system (LI-COR Biosciences, Lincoln, NE). After resection of the overlying skin, the tumor/background ratios (TBRs) were calculated and statistically analyzed using a paired t test.

RESULTS

EGFR expression was seen in all AB samples. Tumor-specific labeling was achieved, as evidenced by a positive fluorescence signal from cetuximab-IRDye800 binding to AB cells, with little staining seen in the negative controls treated with IgG-IRDye800. In the animal PDX model, imaging revealed that the TBRs produced by cetuximab were significantly greater than those produced by IgG on days 7 to 14 for AB-20 tumors. After skin flap removal to simulate a preresection state, the TBRs increased with cetuximab and were significantly greater than the TBRs with the IgG control for PDX tumors derived from the 3 patients with AB. The excised tissues were embedded in paraffin and examined to confirm the presence of tumor.

CONCLUSIONS

Fluorescently labeled anti-EGFR demonstrated specificity for AB cells and PDX tumors. The present study is the first report of tumor-specific, antibody-based imaging of odontogenic tumors, of which AB is one of the most clinically aggressive. We expect this technology will ultimately assist surgeons treating AB by helping to accurately assess the tumor margins during surgery, leading to improved long-term local tumor control and less surgical morbidity.

Ameloblastoma RNA profiling uncovers a distinct non-coding RNA signature

Ameloblastoma of the jaws remains the top difficult to treat odontogenic tumour and has a high recurrence rate. New evidence suggests that non-coding RNAs (ncRNAs) play a critical role in tumourgenesis and prognosis of cancer. However, ameloblastoma ncRNA expression data is lacking. Here we present the first report of ameloblastoma ncRNA signatures. A total of 95 ameloblastoma cases and a global array transcriptome technology covering > 285.000 full-length transcripts were used in this two-step analysis. The analysis first identified in a test cohort 31 upregulated ameloblastoma-associated ncRNAs accompanied by signalling pathways of cancer, spliceosome, mRNA surveillance and Wnt. Further validation in an independent cohort points out the long non-coding (lncRNAs) and small nucleolar RNA (snoRNAs): LINC340, SNORD116-25, SNORA11, SNORA21, SNORA47 and SNORA65 as a distinct ncRNA signature of ameloblastoma. Importantly, the presence of these ncRNAs was independent of BRAF-V600E and SMO-L412F mutations, histology type or tumour location, but was positively correlated with the tumour size. Taken together, this study shows a systematic investigation of ncRNA expression of ameloblastoma, and illuminates new diagnostic and therapeutic targets for this invasive odontogenic tumour.

The diagnostic usefulness of immunohistochemistry for odontogenic lesions

The diagnosis of odontogenic tumors can be challenging, largely due to their rarity and consequent difficulties in gaining experience in their assessment. In most cases, careful attention to morphology, in conjunction with clinical and radiological features will allow a diagnosis to be made. However, in some cases, immunohistochemical analysis of the tumor may be useful. In this review we will outline the immunohistochemical expression profile of normal developing odontogenic tissues and a range of odontogenic tumors. In many cases the immunohistochemical markers are neither specific nor sensitive enough to be of help in diagnosis, but in some cases such analysis may prove very useful. Thus we have outlined a limited number of circumstances where immunohistochemistry may be of use to the practicing diagnostic pathologist.

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.

Matrix metalloproteinase expression in keratocystic odontogenic tumors and primary cells

Keratocystic odontogenic tumors (KCOTs) are locally invasive, rapidly proliferating cystic lesions of the jaw. The bone-invasive nature of these tumors has been previously associated with the expression of matrix metalloproteinases (MMPs), which degrade the extracellular matrix. The purpose of this study was to assess the expression and activity of MMPs in primary KCOT cells and tumor tissue.

METHODS

Four independently established KCOT primary cell populations were grown in Dulbecco's modified Eagle medium supplemented with 10% FBS and antibiotics. Primary cells were analyzed by qRT-PCR and immunohistochemistry (IHC), and for secretion of active MMPs. Primary tumor sections were analyzed by IHC.

RESULTS

Of the 18 human MMPs examined, 9 were consistently expressed in primary KCOT cells. MMP-2 and MMP-14 were highly expressed in all KCOT populations, while MMP-1, 3, 11, 12, 16, 17, and 19 were moderately expressed. MMP-3, 11, 12, 16, 17 and 19 were shown to be expressed in KCOTs for the first time. No significant differences in MMPS profiles were found between syndromic (KCOT-3) and non-syndromic cell populations (KCOT-1/2/4). Protein expression of MMP-1, 11, 12, 14 and 16 was confirmed in each KCOT cell populations by IHC. KCOT-3 cells secreted active MMP-2 as determined by a gel zymography assay. Expression of MMP-1, 2, 3, 11, 12, 14, and 16 was confirmed in matching primary KCOT tumor sections representing syndromic and non-syndromic KCOTs.

CONCLUSION

KCOT primary cell populations and tumors express a wide range of MMPs, which likely play a role in the bone-invasive nature of these 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.

Targeting the sonic hedgehog pathway in keratocystic odontogenic tumor

Keratocystic odontogenic tumors (KCOT) may occur sporadically or associated with the nevoid basal cell carcinoma syndrome. It is a benign aggressive tumor of odontogenic epithelial origin with a high rate of recurrence. A primary human keratocystic odontogenic tumor cell population, KCOT-1, has been established from a tumor explant culture. The KCOT-1 cells were characterized by growth rate, gene expression profiles of major tooth enamel matrix proteins (EMPs), amelogenin (AMELX), enamelin (ENAM), ameloblastin (AMBN), amelotin (AMTN), tumor-related proteins enamelysin (MMP-20), kallikrein-4 (KLK-4), and odontogenic ameloblast-associated protein (ODAM) using quantitative real-time reverse transcription-polymerase chain reaction. Cytokeratin 14 (CK14) was examined by immunohistochemistry. In addition, expression of the members of the sonic hedgehog (SHH) pathway, SHH, patched (PTCH-1), smoothened (SMO), GLI-1, and GLI-2 and of the NOTCH signaling pathway, NOTCH-1, NOTCH-2, NOTCH-3, JAG-2 (Jagged-2), and Delta-like-1 (DLL-1) were evaluated. KCOT-1 cells were treated with SMO antagonist cyclopamine. We found that cyclopamine significantly arrested the growth of KCOT-1 cells in a dose-dependent manner and that the effects of cyclopamine were abolished by adding SHH protein. The protein expression of the SHH pathway was down-regulated by cyclopamine, further confirming that cyclopamine inhibits the SHH signaling pathway; SHH down-regulation correlated with the down-regulation of the NOTCH signaling pathway as well. In conclusion, using an established KCOT-1 cell population, we characterized the gene expression profiles related to the EMPs, SHH, and NOTCH signaling pathway and confirmed that cyclopamine significantly arrested the growth of KCOT-1 cells and may be a viable agent as a novel therapeutic.