Central giant cell granulomas of the jaws stromal cells harbour mutations and have osteogenic differentiation capacity, in vivo and in vitro.

BACKGROUND: Central giant cell granulomas (CGCG) of the jaws are osteolytic lesions that may behave aggressively and respond poorly to surgery. Microscopically, in addition to giant cells, there is a mononuclear cell population composed of macrophage/monocytic cells and spindle-shaped cells of mesenchymal origin. Seventy two percent of these tumours harbour mutually exclusive TRPV4, KRAS and FGFR1 mutations. We aimed to assess the mutational status of mononuclear and giant cells and the osteogenic potential of stromal cells in vitro and in vivo. METHODS AND RESULTS: We screened CGCG for signature mutations and used laser-capture microdissection to demonstrate that the mutations are restricted to the mononuclear cells. Additionally, we established CGCG primary cell culture and observed that the cells retained the mutations throughout passages. By flow cytometry, we observed predominance of CD14- CD51- CD61- cells, consistent with the expected profile for stromal cells. Considering the mesenchymal origin of stromal cells, we assessed the osteogenic differentiation potential of CGCG cells in culture by cytochemistry (von Kossa and alizarin red staining), alkaline phosphatase (ALP) activity assay and gene expression of osteogenic markers. CGCG cells presented self-capacity to increase ALP levels in a time-dependent manner and under osteogenic induction presented increasing number of calcium deposits, and overall higher expression of osteocalcin, RUNX2, ALPL and osteopontin than cells without osteogenic induction. A patient-derived xenograft model for CGCG was established, and osteoid material deposition was observed. CONCLUSION: Collectively, the results confirm that the signature mutations are restricted to stromal cells in CGCG, and the in vitro and in vivo results support that these cells have the capacity to differentiate into osteoblasts, in line with the bone formation often observed in the stroma of these lesions.

Patient-derived xenograft models for the study of benign human neoplasms.

Preclinical models are a core feature of translational research, and patient-derived xenograft (PDX) models have increasingly been used with such purpose. PDX involves the transplantation of fresh human tumor samples into immunodeficient mice to overcome immunologic rejection. It is a valuable tool for basic as well as preclinical research, contributing to the establishment of models to characterize the neoplasms to drug screening and to allow the identification of therapeutic targets. The use of these models is justified because they retain the histological and genomic features of the primary tumor. PDX models are well described for malignant neoplasms, for which the advantages are clear and include the development of drug treatments. The establishment of malignant tumors PDX is undeniably important from a medical perspective. However, few studies have used such models for benign neoplasms. The use of PDX for benign neoplasm studies can help to clarify the pathobiology of these diseases, as well as invasion and malignant transformation mechanisms, which from a biological perspective is equally important to the study of malignant tumors. Therefore, the aim of this study is to review the current methodology for PDX model generation and to cover its main applications, focusing on benign neoplasms.

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.