Hypomethylation of tumor suppressor genes in odontogenic myxoma

Angiogenesis in patient-derived xenografts of odontogenic myxoma

Previously, by employing 3D organotypic tissue culture and patient-derived xenograft (PDX) model, oral myxoma response to a MAPK/MEK inhibitor was observed. Gross examination of the tumour fragments obtained after 55 days of PDX grafting revealed increased capsule vascularization. Microscopic analyses showed blood capillaries intermixed with myxoma cells, but the origin of these capillaries, from mice or humans, was not established. This study aimed to investigate whether the endothelial cells observed in the myxoma PDX model are derived from the mouse or from the primary human tumour. Immunohistochemistry was performed on five tumour fragments from the PDX of myxoma after 55 days of implantation in mice. Immunopositivity for antibodies against human (HLA-ABC) and mouse (H2 Db/H2-D1) major histocompatibility complex class I (MHCI) was assessed in the endothelial cells. The endothelial cells in the PDX fragments revealed a membrane staining for the human MHCI protein in the PDX tumour and adjacent connective tissue capsule, indicating that capillaries were derived from the human tumour fragment. Considering the probable human origin of the endothelial cells from capillary blood vessels in the myxoma PDX, we conclude that this PDX model is an interesting model to study myxoma angiogenesis.

Odontogenic myxomas lack PDGFRB mutations reported in myofibromas

BACKGROUND

The molecular pathogenesis of odontogenic myxoma has not been established yet. Considering that odontogenic myxoma may show myofibroblastic differentiation and myxoid areas can be observed in intra-osseous myofibromas, we tested the hypothesis whether both tumors share a common molecular profile. As recent studies have reported PDGFRB recurrent driver mutations in myofibroma, we evaluated PDGFRB mutations in odontogenic myxomas.

METHODS

A convenience sample of 15 odontogenic myxomas cases was selected. We direct sequenced PDGFRB exons 12 and 14, where p.R561C (c.1681C>T) and p.N666K (c.1998C>G) hotspot mutations have been reported among others in single and/or multiple myofibromas.

RESULTS

All 15 odontogenic myxoma samples were successfully sequenced, and all 15 had wild-type sequences for the PDGFRB mutations investigated.

CONCLUSION

Our findings suggest that PDGFRB mutations do not play a role in odontogenic myxoma pathogenesis, which might be helpful in the differential diagnosis of challenging cases.

p16INK4a as a proliferation marker unrelated to HPV expression in odontogenic cysts and tumors

INTRODUCTION

p16INK4a is a tumor suppressor protein that retards cell cycle progression from G1 to S phase. Prior studies have evaluated p16INK4a expression in odontogenic keratocyst and ameloblastoma, but data regarding other odontogenic cysts and tumors have been sparse.

METHODS

With IRB approval, cases from the following entities were identified from archives of the UF Oral Pathology Biopsy Service (2005-2015): benign incidental odontogenic rest, dentigerous cyst, lateral periodontal cyst, calcifying odontogenic cyst, glandular odontogenic cyst, odontogenic keratocyst, orthokeratinized odontogenic cyst, adenomatoid odontogenic tumor, calcifying epithelial odontogenic tumor, and ameloblastoma. All cases were submitted for p16INK4a immunohistochemical testing.

RESULTS

Results were scored as follows: nuclear and cytoplasmic staining of <5% cells (score 0), 5%-25% (score 1), 25%-50% (score 2), >50% (score 3). No significant difference in p16INK4a staining was noted between odontogenic cysts and the listed odontogenic tumors (chi-square, P = .540). When comparing lesions with higher recurrence rates (over 25% as reported in the literature) versus lesions with low recurrence rates (under 25%), higher recurrence correlated to significantly higher p16INK4a positivity (chi-square, P = .001). Follow-up testing was performed on 18 cases with "2" or "3" p16INK4a expression scores for high-risk HPV strains through HPV in situ hybridization (ISH) messenger RNA testing with no cases exhibiting a positive result.

CONCLUSION

This study exhibits an association between increased p16INK4a positivity and odontogenic lesions with higher recurrence rates and highlights the role of p16INK4a as a progression marker unrelated to HPV expression in this group of pathologic entities.

First insights for targeted therapies in odontogenic myxoma

OBJECTIVE

Odontogenic myxoma (OM) occasionally responds poorly to surgical treatment. The MAPK pathway is constitutively activated in several neoplasms and we aimed to test if the MAPK pathway is activated in OM, in order to pave the way for an alternative therapy for aggressive and recurrent cases.

MATERIALS AND METHODS

The immunoexpression of phosphorylated ERK1/2 (pERK1/2) was assessed in OM. We established a 3D organotypic culture model for the in vitro study and patient-derived xenografts (PDX) in mice for the in vivo study. The MEK inhibitor U0126 was used to inhibit phosphorylation of ERK1/2 in the in vitro and in vivo models.

RESULTS

All OM showed strong pERK1/2 immunoexpression, consistent with MAPK pathway activation. Treatment of the 3D culture with U0126 resulted in a reduced pERK1/2/ERK1/2 ratio. Consistent with the in vitro results, all PDX of animals treated with U0126 showed a decreased volume fold change compared with controls.

CONCLUSIONS

The MAPK pathway is activated in OM and its inhibition leads to tumor shrinkage in PDX and cell culture models.

CLINICAL RELEVANCE

Our results offer a pre-clinical frame for OM-targeted therapy. Further work is needed to determine if this initial finding holds clinical promise.

Epigenetic mechanisms in odontogenic tumors: A literature review

OBJECTIVE

Epigenetic mechanisms, such as DNA methylation, regulate important biological processes as gene expression and it was suggested that these phenomena play important roles in the carcinogenesis and tumor biology. The aim of this review is to provide the current state of knowledge about epigenetic alterations, focusing mainly on DNA methylation, reported in odontogenic tumors.

DESIGN

Literatures were searched based in the combination of the following keywords: odontogenic tumors, epigenetics, DNA methylation, histone modifications, non-coding RNA, microRNA, DNA methyltransferases. Electronic databases (Medline/PubMed, Scopus and Web of Science) were screened.

RESULTS

The analysis of epigenetic alterations in different tumors has rapidly increased; however, limited information is available about epigenetic mechanisms involved in the formation of odontogenic tumors. DNA methylation is the most studied epigenetic modification in these tumors and the participation of non-coding RNA's in odontogenic tumors has been recently addressed. Differential expression of DNA methyltransferases, altered DNA methylation patterns and aberrant expression of non-coding RNA's were reported in odontogenic tumors.

CONCLUSIONS

Current studies suggest epigenetics as an emerging mechanism, possibly implicated in etiopathogenesis of odontogenic tumors. Deeper understanding of the epigenetic abnormalities in these tumors could show potential applications as biomarkers or therapeutic possibilities in the future.

Expression of STK11 gene and its promoter activity in MCF control and cancer cells

Serine/threonine kinase gene (STK11) is identified as tumor suppressor gene whose mutation can lead to Peutz-Jeghers syndrome (PJS). STK11 is emerging as a multifunctional protein, it activates 14 different AMP-activated protein kinase (AMPK) family members, important in the regulation of cell polarity, cell cycle arrest, energy and hemostasis. Present study was designed to evaluate STK11 mRNA expression in MCF-7 cancer and MCF-10 normal breast cells lines. mRNA expression was studied by real-time PCR. Further, human STK11 promoter construct was fused to a luciferase reporter and transfected into both MCF-7 and MCF-10 cells to identify the promoter activity in these cells. STK11 mRNA was found significantly higher in MCF-7 compared to MCF-10 cells (p value < 0.0005) indicating its role in the onset of breast cancer. Interestingly, it was found that the promoter activity of STK11 gene in MCF-7 cells was also significantly higher when compared to MCF-10 cells (p value < 0.005). Positive correlation was observed in promoter activity and gene expression (p = 0.048, r2 = 0.587). This study for the first time relates the altered STK11 gene expression in breast cancer cells with altered promoter activity. The present finding may shed light on the new therapeutic approaches against breast cancer by targeting gene or its promoter.

Gene promoter methylation and protein expression of BRMS1 in uterine cervix in relation to high-risk human papilloma virus infection and cancer

Cervical cancer is strongly related to certain high-risk types of human papilloma virus infection. Breast cancer metastasis suppressor 1 (BRMS1) is a tumor suppressor gene, its expression being regulated by DNA promoter methylation in several types of cancers. This study aims to evaluate the methylation status of BRMS1 promoter in relation to high-risk types of human papilloma virus infection and the development of pre-cancerous lesions and describe the pattern of BRMS1 protein expression in normal, high-risk types of human papilloma virus-infected pre-cancerous and malignant cervical epithelium. We compared the methylation status of BRMS1 in cervical smears of 64 women with no infection by high-risk types of human papilloma virus to 70 women with proven high-risk types of human papilloma virus infection, using real-time methylation-specific polymerase chain reaction. The expression of BRMS1 protein was described by immunohistochemistry in biopsies from cervical cancer, pre-cancerous lesions, and normal cervices. Methylation of BRMS1 promoter was detected in 37.5% of women with no high-risk types of human papilloma virus infection and was less frequent in smears with high-risk types of human papilloma virus (11.4%) and in women with pathological histology (cervical intraepithelial neoplasia) (11.9%). Methylation was detected also in HeLa cervical cancer cells. Immunohistochemistry revealed nuclear BRMS1 protein staining in normal high-risk types of human papilloma virus-free cervix, in cervical intraepithelial neoplasias, and in malignant tissues, where staining was occasionally also cytoplasmic. In cancer, expression was stronger in the more differentiated cancer blasts. In conclusion, BRMS1 promoter methylation and aberrant protein expression seem to be related to high-risk types of human papilloma virus-induced carcinogenesis in uterine cervix and is worthy of further investigation.

DNA methylation analysis of cancer-related genes in oral epithelial cells of healthy smokers

AIM

The aim of this study was to investigate the smoking habit influence on DNA methylation status in the promoters of the cancer related-genes MLH1, hTERT and TP53 in oral epithelial cells of healthy subjects.

MATERIALS AND METHODS

DNA methylation analysis was performed using methylation-sensitive restriction enzymes (MSRE) in oral epithelial cells from non-smokers, smokers and ex-smokers.

RESULTS

The investigated CpG dinucleotides located at HhaI and HpaII sites in the MLH1 gene promoter were observed to be fully methylated in the majority of DNA samples from the smoker group and statistical differences were found between non-smokers and smokers and between smokers and ex-smokers (p<0.05). The same was observed in the hTERT gene promoter at HhaI sites (p<0.05) and for HpaII sites the unmethylated condition was more frequent in smokers in comparison to non-smokers (p<0.05). For TP53, no differences were found among groups (p>0.05), with the fully methylated condition found to be a common event in healthy oral epithelial cells.

CONCLUSION

We conclude that smoking may induce changes in DNA methylation status in cancer-related genes of oral epithelial cells and that the cessation of smoking is capable of reversing this process. Based on our data, we suggest that DNA methylation status of the hTERT and MLH1 gene promoters are promising markers for screening a set of smoking-related alterations in oral cells.

Facial dysmorphology and odontogenic tumor development associated with inborn errors of metabolism: a case report

PURPOSE

Inborn errors of metabolism (IEMs) are genetic disorders that alter normal physiologic functioning. Deficiency of 3-methylcrotonyl-coenzyme A carboxylase is one such IEM that can lead to major episodes of metabolic dysfunction. Certain IEMs are associated with characteristic congenital dysmorphic facial features. This can be problematic, because these dysmorphisms can mask underlying tumor growth. Literature is lacking on a causal relation between IEM and odontogenic tumor development.

MATERIALS AND METHODS

This case was explained in detail and a review of the literature was undertaken. PubMed was used to search for articles involving surgical management of odontogenic myxoma (OM) and associations between odontogenic tumors and IEM.

RESULTS

It was determined that the development of odontogenic tumors, specifically OM, is associated with IEMs. These tumors can easily be overlooked as a common dysmorphic feature of an IEM.

CONCLUSION

IEMs lead to major metabolic disturbances and, thus, can alter the cellular microenvironment. Hypothetically, these alterations can lead to the development of odontogenic tumors. With the diagnosis of IEM becoming more common owing to improved newborn screening, careful attention should be given to these patients because of the possibility that dysmorphologic facial features could be masking underlying tumor growth.

Oncologic profile of maxillary odontogenic myxoma: A rare case

Odontogenic myxoma (OM) is an ectomesenchyme derived neoplasm, almost exclusively found in jaws. This article presents a maxillary OM with a brief review of the molecular and proteomic antecedents of OMs, capturing its histopathogenesis.

Epigenetic regulation of matrix metalloproteinase expression in ameloblastoma

BACKGROUND

An ameloblastoma is a benign odontogenic neoplasm with aggressive behaviour and high recurrence rates. The increased expression of matrix metalloproteinases (MMPs) has been reported in ameloblastomas. In the present study, we hypothesised that epigenetic alterations may regulate MMP expression in ameloblastomas.

METHODS

We investigated the methylation status of the genes MMP-2 and MMP-9 in addition to mRNA transcription and protein expression in ameloblastomas. Methylation analysis was performed by both methylation-specific polymerase chain reaction (MSP-PCR) and restriction enzyme digestion to evaluate the methylation profile of MMP-2 and MMP-9 in 12 ameloblastoma samples and 12 healthy gingiva fragments, which were included as controls. Furthermore, we investigated the transcription levels of the genes by quantitative reverse-transcription PCR (qRT-PCR). Zymography was performed to verify protein expression in ameloblastomas.

RESULTS

The ameloblastomas showed a high frequency of unmethylated MMP-2 and MMP-9, whereas the healthy gingival samples presented a sharp prevalence of methylated MMPs. Higher expression levels of MMP-9 were found in ameloblastomas compared to healthy gingiva. However, no significant differences in the MMP-2 mRNA expression between groups was found. All ameloblastomas showed positive expression of MMP-2 and MMP-9 proteins.

CONCLUSIONS

Our findings suggest that expression of MMP-9 is increased in ameloblastomas and is possibly modulated by unmethylation of the gene.