Surface vacuolar ATPase in ameloblastoma contributes to tumor invasion of the jaw bone

Trends in Research of Odontogenic Keratocyst and Ameloblastoma

Odontogenic keratocyst (OKC) and ameloblastoma (AM) are common jaw lesions with high bone-destructive potential and recurrence rates. Recent advancements in technology led to significant progress in understanding these conditions. Single-cell and spatial omics have improved insights into the tumor microenvironment and cellular heterogeneity in OKC and AM. Fibroblast subsets in OKC and tumor cell subsets in AM have been analyzed, revealing mechanisms behind their biological behaviors, including OKC's osteolytic features and AM's recurrence tendencies. Spatial transcriptomics studies of AM have identified engineered fibroblasts and osteoblasts contributing to matrix remodeling gene and oncogene expression at the invasion frontier, driving AM progression. Three-dimensional culture technologies such as organoid models have refined analysis of AM subtypes; uncovered the role of AM fibroblasts in promoting tumor cell proliferation and invasion; and identified signaling pathways such as FOSL1, BRD4, EZH2, and Wnt as potential therapeutic targets. Organoid models also served as preclinical platforms for testing potential therapies. Although preclinical models for AM exist, reliable in vitro and in vivo models for OKC remain scarce. Promising mimic models, including human embryonic stem cells-derived epithelial cells, human oral keratinocytes, human immortalized oral epithelial cells, and HaCaT keratinocytes, show promise, but the advancements in 3-dimensional culture technology are expected to lead to further breakthroughs in this area. Artificial intelligence, including machine learning and deep learning, has enhanced radiomics-based diagnostic accuracy, distinguishing OKC and AM beyond clinician capability. Pathomics-based models further predict OKC prognosis and differentiate AM from ameloblastic carcinoma. Clinical studies have shown positive outcomes with targeted therapies. In a study investigating SMO-targeted treatments for nevoid basal cell carcinoma syndrome, nearly all OKC lesions resolved in 3 patients. A recent clinical trial with neoadjuvant BRAF-targeted therapy for AM demonstrated promising radiologic responses, potentially enabling organ preservation. This review highlights recent advancements and trends in OKC and AM research, aiming to inspire further exploration and progress in these fields.

Proteomics study of bone tissue around ameloblastoma and the potential mechanism of CD36 in bone remodelling

Ameloblastoma (AM) is characterised by local aggressiveness and bone resorption. To our knowledge, the proteomic profile of bone adjacent to AM has not previously been explored. We therefore looked at the differential proteins in cancellous bone (CB) adjacent to AM and normal CB from the mandible. CB proteins were extracted, purified, quantified, and analysed by liquid chromatography-mass spectrometry (LC-MS) using samples from five patients with AM. These proteins were further investigated using gene ontology for additional functional annotation and enrichment. Proteins that met the screening requirements of expression difference ploidy > 1.5-fold (upregulation and downregulation) and p < 0.05 were subsequently deemed differential proteins. Immunohistochemical staining was performed to confirm the above findings. Compared with normal mandibular CB, 151 differential proteins were identified in CB adjacent to the mandibular AM. These were mainly linked to cellular catabolic processes, lipid metabolism, and fatty acids (FA) metabolism. LC-MS and immunohistochemistry showed that CD36 was one of the notably decreased proteins in CB bordering the AM compared with normal mandibular CB (p = 0.0066 and p = 0.0095, respectively). CD36 expression in CB correlates with bone remodelling in AM, making CD36 a viable target for therapeutic approaches.

Machine learning-based radiomics for predicting BRAF-V600E mutations in ameloblastoma

Background

Ameloblastoma is a locally invasive and aggressive epithelial odontogenic neoplasm. The BRAF-V600E gene mutation is a prevalent genetic alteration found in this tumor and is considered to have a crucial role in its pathogenesis. The objective of this study is to develop and validate a radiomics-based machine learning method for the identification of BRAF-V600E gene mutations in ameloblastoma patients.

Methods

In this retrospective study, data from 103 patients diagnosed with ameloblastoma who underwent BRAF-V600E mutation testing were collected. Of these patients, 72 were included in the training cohort, while 31 were included in the validation cohort. To address class imbalance, synthetic minority over-sampling technique (SMOTE) is applied in our study. Radiomics features were extracted from preprocessed CT images, and the most relevant features, including both radiomics and clinical data, were selected for analysis. Machine learning methods were utilized to construct models. The performance of these models in distinguishing between patients with and without BRAF-V600E gene mutations was evaluated using the receiver operating characteristic (ROC) curve.

Results

When the analysis was based on radiomics signature, Random Forest performed better than the others, with the area under the ROC curve (AUC) of 0.87 (95%CI, 0.68-1.00). The performance of XGBoost model is slightly lower than that of Random Forest, and its AUC is 0.83 (95% CI, 0.60-1.00). The nomogram evident that among younger women, the affected region primarily lies within the mandible, and patients with larger tumor diameters exhibit a heightened risk. Additionally, patients with higher radiomics signature scores are more susceptible to the BRAF-V600E gene mutations.

Conclusions

Our study presents a comprehensive radiomics-based machine learning model using five different methods to accurately detect BRAF-V600E gene mutations in patients diagnosed with ameloblastoma. The Random Forest model's high predictive performance, with AUC of 0.87, demonstrates its potential for facilitating a convenient and cost-effective way of identifying patients with the mutation without the need for invasive tumor sampling for molecular testing. This non-invasive approach has the potential to guide preoperative or postoperative drug treatment for affected individuals, thereby improving outcomes.

αTAT1-induced tubulin acetylation promotes ameloblastoma migration and invasion

Ameloblastoma (AB) is the most common benign epithelial odontogenic tumor occurring in the jawbone. AB is a slowly growing tumor but sometimes shows a locally invasive and an aggressive growth pattern with a marked bone resorption. In addition, the local recurrence and distant metastasis of AB also sometimes occurs, which resembles one of the typical malignant potentials. From these points of view, to understand better the mechanisms of AB cell migration or invasion is necessary for the better clinical therapy and improvements of the patients' quality of life. Microtubules in eukaryotic cells reveal the shape of hollow cylinders made up of polymerized alpha (α)- and beta (β)-tubulin dimers and form the cytoskeleton together with microfilaments and intermediate filaments. Microtubules play important roles in cell migration by undergoing assembly and disassembly with post-translational modifications. Stability of microtubules caused by their acetylation is involved in cell migration. In this study, we investigated the expression and distribution of acetylated α-tubulin and alpha-tubulin N-acetyltransferase 1 (αTAT1), an enzyme which acetylates Lys-40 in α-tubulin, in AB specimens, and analyzed how tubulin was acetylated by αTAT1 activation in a human AB cell line, AM-1. Finally, we clarified that TGF-β-activated kinase1 (TAK1) was phosphorylated by TGF-β stimulation, then, induced tubulin acetylation via αTAT1 activation, which subsequently activated the migration and invasion of AB cells.

Molecular biological findings of ameloblastoma

Ameloblastoma is benign odontogenic tumours that mainly occur in the jawbone. This tumour induces aggressive invasion into the surrounding bone and has a high recurrence rate after surgery. Therefore, mandibular resection is performed in many patients with this tumour, causing aesthetic and functional problems. It is necessary to develop a novel treatment strategy for ameloblastoma, but there are currently no innovative treatments. Although our understanding of the molecular biological mechanisms of ameloblastoma is still insufficient, there have been many recent reports of new molecular biological findings on ameloblastoma. Therefore, bioactive factors that have potential for novel therapeutic methods, such as molecular targeted therapy, have been discovered in ameloblastoma. In this review, we summarize the molecular biological findings of ameloblastoma reported over several decades, focusing on factors involved in invasion into surrounding tissues and disease-specific gene mutations. We also mention the effect of the interaction between tumour cells and stromal components in ameloblastoma on tumour development. Scientific field of dental Science: Oral surgery, Odontogenic tumor, Ameloblastoma.

Activation of Wnt signalling reduces the population of cancer stem cells in ameloblastoma

Objectives

The treatment of ameloblastoma, an odontogenic epithelial tumour destroying jawbone, mainly depends on radical destructive resections. Other therapeutic options are limited by the characteristics of ameloblastoma, such as high recurrence rates and resistance to radiation and chemotherapy, which implies possible existence of cancer stem cells (CSCs) in ameloblastoma. Here, we identified a putative CSC population in immortalized and primary human ameloblastoma cells and examined possible therapeutic reagents to reduce the CSC population.

Methods

We investigated subpopulations of AM‐1 cell line and human ameloblastoma cells using immunocytochemistry and flow cytometry and the effects of Wnt signalling activators on the 2‐ and 3‐dimensional cultured ameloblastoma cells using molecular biological analyses.

Result

Among heterogenous ameloblastoma cells, small‐sized and round‐shaped cells were found to be proliferative and expressed a marker of dental epithelial stem cells, SRY‐box 2 (Sox2). Exogenous activation of Wnt signalling using glycogen synthase kinase 3β inhibitors, lithium chloride (LiCl) and valproic acid (VPA), increased the cell size and decreased proliferation of cells and expression of Sox2 in 2 dimensionally cultured AM‐1 and human primary ameloblastoma cells. Furthermore, the growth of 3 dimensionally cultured AM‐1 cells as suspended or embedded in gel was suppressed by treatment with Wnt signalling activators, VPA and CHIR99021, or antibodies to sclerostin, an antagonist of Wnt signalling.

Conclusion

We suggest that Wnt signalling activators are potential drug candidates to suppress CSCs in ameloblastoma.

Volume-regulated chloride channel regulates cell proliferation and is involved in the possible interaction between TMEM16A and LRRC8A in human metastatic oral squamous cell carcinoma cells

OBJECTIVES

Volume-regulated anion channels (VRACs), expressed in various cells, play an important role in cell volume regulation. Despite being physiologically defined almost half a century ago, only the molecular candidates of VRAC, TMEM16A, LRRC8A, and bestrophin-1 (BEST1), are known. Here, we aimed to explore the functional significance of VRAC in, HST-1, an oral squamous cell carcinoma (OSCC) cell line.

METHODS

Cell proliferation assays, RT-PCR, Western blot, and flow cytometry were used to estimate changes in gene expression and cell proliferation. Ion channel activity was recorded using the patch-clamp technique. Specific genes were knocked-down by siRNA assays.

RESULTS

VRAC, identified as a hypotonicity-induced current, was highly functional and associated with the proliferation of HST-1 cells but not of HaCaT (a normal keratinocyte) cells. The pharmacological profile of VRAC in HST-1 was similar to that reported previously. DCPIB, a specific VRAC inhibitor, completely inhibited VRAC and proliferation of HST-1 cells, eventually leading to apoptosis. VRAC in HST-1 was attenuated by the knockdown of TMEM16A and LRRC8A, while knockdown of BEST1 affected cell proliferation. In situ proximity ligation assay showed that TMEM16A and LRRC8A co-localized under isotonic conditions (300 mOsM) but were separated under hypotonic conditions (250 mOsM) on the plasma membrane.

CONCLUSIONS

We have found that VRAC acts to regulate the proliferation of human metastatic OSCC cells and the composition of VRAC may involve in the interactions between TMEM16A and LRRC8A in HST-1 cells.

Hypoxia-induced HIF-1α and ZEB1 are critical for the malignant transformation of ameloblastoma via TGF-β-dependent EMT

Ameloblastic carcinoma (AC) is defined as a rare primary epithelial odontogenic malignant neoplasm and the malignant counterpart of benign epithelial odontogenic tumor of ameloblastoma (AB) by the WHO classification. AC develops pulmonary metastasis in about one third of the patients and reveals a poor prognosis. However, the mechanisms of AC oncogenesis remain unclear. In this report, we aimed to clarify the mechanisms of malignant transformation of AB or AC carcinogenesis. The relatively important genes in the malignant transformation of AB were screened by DNA microarray analysis, and the expression and localization of related proteins were examined by immunohistochemistry using samples of AB and secondary AC. Two genes of hypoxia-inducible factor 1 alpha subunit (HIF1A) and zinc finger E-box-binding homeobox 1 (ZEB1) were significantly and relatively upregulated in AC than in AB. Both genes were closely related in hypoxia and epithelial-mesenchymal transition (EMT). In addition, expressions of HIF-1α and ZEB1 proteins were significantly stronger in AC than in AB. In the cell assays using ameloblastoma cell line, AM-1, hypoxia condition upregulated the expression of transforming growth factor-β (TGF-β) and induced EMT. Furthermore, the hypoxia-induced morphological change and cell migration ability were inhibited by an antiallergic medicine tranilast. Finally, we concluded that hypoxia-induced HIF-1α and ZEB1 were critical for the malignant transformation of AB via TGF-β-dependent EMT. Then, both HIF-1α and ZEB1 could be potential biomarkers to predict the malignant transformation of AB.

Upregulation of interleukin-8 and activin A induces osteoclastogenesis in ameloblastoma

Ameloblastoma is a common odontogenic benign tumor located in the jaws and is characterized by severe local bone destruction. The current study aimed to investigate the effect of interactions between tumor cells and bone marrow stromal cells (BMSCs) on osteoclast formation in ameloblastoma. The impact of ameloblastoma/BMSC interactions on cytokine production, gene expression and osteoclastogenesis was examined using an immortalized ameloblastoma cell line that the authors' previously established. The results demonstrated that interactions between ameloblastoma cells and BMSCs increased interleukin (IL)‑8 and activin A secretion by BMSCs. IL‑8 expression in BMSCs was modulated by tumor‑derived tumor necrosis factor‑α and IL‑8 contributed to osteoclast formation not only directly but also by stimulating receptor activator of NF‑κB ligand (RANKL) expression in BMSCs. Activin A secretion in BMSCs was stimulated by ameloblastoma cells via cell‑to‑cell‑mediated activation of c‑Jun N‑terminal kinase activation, acting as a cofactor of RANKL to induce osteoclast formation and function. The present study highlights the critical role of communication between BMSCs and ameloblastoma cells in bone resorption in ameloblastoma.

Effect of technetium-99 conjugated with methylene diphosphonate (99 Tc-MDP) on OPG/RANKL/RANK system in vitro

BACKGROUND

RANKL and RANK play an important role in jaw resorption during the development of the ameloblastomas. Therefore, the aim of this study was to explore the effect of ⁹⁹ Tc-MDP on OPG/RANKL/RANK system on RAW264.7 and MC3T3-E1 cell lines in vitro and provide the theoretical basis for the clinical treatment of the jaw ameloblastoma.

METHODS

Different concentrations of ⁹⁹ Tc-MDP were used to treat RAW264.7 and MC3T3-E1 cell lines. The cell proliferative inhibition rate was analyzed by CCK-8. Cell apoptosis and cell cycle were detected by flow cytometry. Western blot was used to detect the expression of OPG, RANKL, and RANK.

RESULTS

Treatment of RAW264.7 cell lines with different concentrations of ⁹⁹ Tc-MDP had inhibitory effects and decreased the expression of RANK protein. The cell proliferation of ⁹⁹ Tc-MDP on MC3T3-E1 cell lines was stronger at 48 hours than at 24 hours except for 100 μg/mL concentration group. Compared with the concentration of 0.01 μg/mL, the treatment of MC3T3-E1 cells with 100 μg/mL ⁹⁹ Tc-MDP showed that the cell proliferative effect decreased at 24 hours and 48 hours (P < 0.05). After treatment with 0.01 μg/mL ⁹⁹ Tc-MDP, the expression of OPG in MC3T3-E1 cells was significantly increased (P < 0.05). Compared with 0.01 μg/mL, the expression of RANKL was decreased after treatment with 100 μg/mL ⁹⁹ Tc-MDP (P < 0.05).

CONCLUSION

⁹⁹ Tc-MDP can induce apoptosis of RAW264.7 cells and inhibit the expression of RANK protein. The effect of 0.01 μg/mL of low concentration of ⁹⁹ Tc-MDP can promote the proliferation of MC3T3-E1 cells and increase the expression of OPG and RANKL protein. ⁹⁹ Tc-MDP may have adjuvant therapeutic effects on the treatment of jaw ameloblastoma.