Sonic Hedgehog Signalling Pathway and Ameloblastoma - A Review

Differentially expressed extracellular matrix genes functionally separate ameloblastoma from odontogenic keratocyst

BACKGROUND

Ameloblastoma and odontogenic keratocyst (OKC) are odontogenic tumors that develop from remnants of odontogenic epithelium. Both display locally invasive growth characteristics and high predilection for recurrence after surgical removal. Most ameloblastomas harbor BRAFV600E mutation while OKCs are associated with PATCH1 gene mutation but distinctive indicators of ameloblastoma growth characteristics relative to OKC are still unclear. The aim of this study was to assess hub genes that underlie ameloblastoma growth characteristics using bioinformatic analysis, ameloblastoma samples and mouse xenografts of human epithelial-derived ameloblastoma cells.

METHODS

RNA expression profiles were extracted from GSE186489 gene expression dataset acquired from Gene Expression Ominibus (GEO) database. Galaxy and iDEP online analysis tools were used to identify differentially expressed genes that were further characterized by gene ontology (GO) and pathway analysis using ShineyGO. The protein-protein interaction (PPI) network was constructed for significantly upregulated differentially expressed genes using online database STRING. The PPI network visualization was performed using Cytoscape and hub gene identification with cytoHubba. Top ten nodes were selected using maximum neighborhood component, degree and closeness algorithms and analysis of overlap was performed to confirm the hub genes. Epithelial-derived ameloblastoma cells from conventional ameloblastoma were transplanted into immunocompromised mice to recreate ameloblastoma in vivo based on the mouse xenograft model. The top 3 hub genes FN1, COL I and IGF-1 were validated by immunostaining and quantitative analysis of staining intensities to ameloblastoma, OKC samples and mouse ameloblastoma xenografts tissues.

RESULTS

Seven hub genes were identified among which FN1, COL1A1/COL1A2 and IGF-1 are associated with extracellular matrix organization, collagen binding, cell adhesion and cell surface interaction. These were further validated by positive immunoreactivity within the stroma of ameloblastoma samples but both ameloblastoma xenograft and OKC displayed only FN1 and IGF-1 immunoreactivity while COL 1 was unreactive. The expression levels of both FN1 and IGF-1 were much lower in OKC relative to ameloblastoma.

CONCLUSION

This study further validates a differentially upregulated expression of matrix proteins FN1, COL I and IGF-1 in ameloblastoma relative to OKC. It suggests that differential stromal architecture and growth characteristics of ameloblastoma relative to OKC could be an interplay of differentially upregulated genes in ameloblastoma.

Targeting BRD4 attenuates the stemness and aggressiveness of ameloblastoma

BACKGROUND

BRD4, belonging to the bromodomain extra-terminal (BET) protein family, plays a unique role in tumor progression. However, the potential impact of BRD4 in ameloblastoma (AM) remains largely unknown. Herein, we aimed to assess the expression and functional role of BRD4 in AM.

METHODS

The expression level of BRD4 was assessed by immunohistochemistry. The proliferation, migration, invasion, and tumorigenic abilities of AM cells were assessed by a series of assays. To explore the molecular expression profile of BRD4-depleted AM cells, RNA sequencing (RNA-seq) was performed. Bioinformatic analysis was performed on AM expression matrices obtained from the Gene Expression Omnibus (GEO). The therapeutic efficacy of BET-inhibitors (BETi) was assessed with AM patient-derived organoids.

RESULTS

Upregulation of BRD4 was observed in conventional AMs, recurrent AMs, and ameloblastic carcinomas. Depletion of BRD4 inhibited proliferation, invasion, migration, and tumorigenesis in AM. Administration of BETi attenuated the aggressiveness of AM and the growth of AM patient-derived organoids. Bioinformatic analysis indicated that BRD4 may promote AM progression by regulating the Wnt pathway and stemness-associated pathways.

CONCLUSION

BRD4 increases the aggressiveness and promotes the recurrence of ameloblastoma by regulating the Wnt pathway and stemness-associated pathways. These findings highlight BRD4 as a promising therapeutic target in AM management.

[Molecular basis of ameloblastoma pathogenesis: A review]

Ameloblastoma is the most common and highly invasive benign odontogenic tumor. Its pathogenesis is not yet fully understood.

Objective

To describe the most important molecular findings that promote the proliferative activity of ameloblastoma and the factors involved that encourage invasion into surrounding bone tissues.

Methodology

A search for scientific evidence was conducted through the following databases: Science Direct, Medline, Wiley, Web of Science, and Google Scholar. A total of 32 articles were reviewed, with inclusion criteria being articles published in English and Spanish; descriptive and analytical studies, narrative and systematic reviews published from January 2015 to June 2021. Letters to the editor were excluded.

Results

The biological molecular findings that allow ameloblastoma to invade surrounding tissues involve alterations in the RANK/RANKL/OPG pathways, transforming growth factor beta (TGF-β), Wnt/β-catenin pathway, and matrix metalloproteinases, as well as alterations in MAPK and SHH pathways that facilitate the proliferation and tumor development of ameloblastoma.

Conclusions

These findings are fundamental for a better understanding of the pathways involved in the pathogenesis of ameloblastoma.

Immunohistochemical analysis of SHH, SMO and GLI-1 proteins in epithelial odontogenic lesions

The present study analyzed the expression of proteins involved in the sonic hedgehog signaling pathway (SHH, SMO, and GLI-1) in benign epithelial odontogenic lesions (odontogenic keratocyst - OKC, ameloblastoma - AB, and adenomatoid odontogenic tumor - AOT) in order to identify the role of these proteins in the pathogenesis of these lesions. The sample consisted of 20 OKCs, 20 ABs, and 10 AOTs. The Kruskal-Wallis, Mann-Whitney U, and Spearman's (r) tests were used for statistical analysis, with the level of significance set at 5% (p < 0.05). The membrane/cytoplasmic expression of SHH was significantly higher in AB compared to AOT (p = 0.022) and OKC (p = 0.02). No differences were found in the membrane/cytoplasmic expression of SMO between the lesions studied. Regarding GLI-1, significant differences were observed at the nuclear level for AB and OKC compared to AOT (p < 0.0001). In addition, significant positive correlations were found between cytoplasmic and nuclear GLI-1 in AB (r = 0.482; p = 0.031) and OKC (r = 0.865; p < 0.0001), and between membrane/cytoplasmic SMO and cytoplasmic GLI-1 in AOT (r = 0.667; p = 0.035) and OKC (r = 0.535; p = 0.015). The results of this study confirm the participation of the sonic hedgehog signaling pathway in the pathogenesis of the lesions studied. Overexpression of SHH in ABs and nuclear expression of GLI-1 in ABs and OKCs indicate that these proteins contribute to the more aggressive behavior of these two lesions when compared to AOT.

Sonic Hedgehog signaling pathway in gynecological and genitourinary cancer (Review)

Cancers of the urinary tract, as well as those of the female and male reproductive systems, account for a large percentage of malignancies worldwide. Mortality is frequently affected by late diagnosis or therapeutic difficulties. The Sonic Hedgehog (SHH) pathway is an evolutionary conserved molecular cascade, which is mainly associated with the development of the central nervous system in fetal life. The present review aimed to provide an in‑depth summary of the SHH signaling pathway, including the characterization of its major components, the mechanism of its upstream regulation and non‑canonical activation, as well as its interactions with other cellular pathways. In addition, the three possible mechanisms of the cellular SHH cascade in cancer tissue are discussed. The aim of the present review was to summarize significant findings with regards to the expression of the SHH pathway components in kidney, bladder, ovarian, cervical and prostate cancer. Reports associated with common deficits and de‑regulations of the SHH pathway were summarized, despite the differences in molecular and histological patterns among these malignancies. However, currently, neither are SHH pathway elements included in panels of prognostic/therapeutic molecular patterns in any of the discussed cancers, nor have the drugs targeting SMO or GLIs been approved for therapy. The findings of the present review may support future studies on the treatment of and/or molecular targets for gynecological and genitourinary cancers.

Molecular and genetic aspects in the etiopathogenesis of ameloblastoma: An update

Ameloblastoma is the second most common benign epithelial odontogenic tumor and though it is of a benign nature, it is locally invasive, has a high recurrence rate and could potentially become malignant. Many theories have been proposed to explain the pathogenesis of ameloblastoma. Proper understanding of the pathogenic mechanism involved in ameloblastoma and its proliferation aids in constituting proper treatment of choice at an early stage, preventing morbidity associated with extensive therapy. An attempt has been made to discuss the current concepts related to molecular and genetic changes that occur in ameloblastoma as these could affect treatment plan and prognosis.

Requirement of Smad4 from Ocular Surface Ectoderm for Retinal Development

Microphthalmia is characterized by abnormally small eyes and usually retinal dysplasia, accounting for up to 11% of the blindness in children. Right now there is no effective treatment for the disease, and the underlying mechanisms, especially how retinal dysplasia develops from microphthalmia and whether it depends on the signals from lens ectoderm are still unclear. Mutations in genes of the TGF-β superfamily have been noted in patients with microphthalmia. Using conditional knockout mice, here we address the question that whether ocular surface ectoderm-derived Smad4 modulates retinal development. We found that loss of Smad4 specifically on surface lens ectoderm leads to microphthalmia and dysplasia of retina. Retinal dysplasia in the knockout mice is caused by the delayed or failed differentiation and apoptosis of retinal cells. Microarray analyses revealed that members of Hedgehog and Wnt signaling pathways are affected in the knockout retinas, suggesting that ocular surface ectoderm-derived Smad4 can regulate Hedgehog and Wnt signaling in the retina. Our studies suggest that defective of ocular surface ectoderm may affect retinal development.