Solitary myofibroma of the mandible in an adult with magnetic resonance imaging and positron emission tomography findings: a case report

Myofibroma is a benign tumor composed of myoid spindle cells. The prevalence of myofibroma in the oral cavity is very low, with the mandible being the most common site. This report describes an adult case of myofibroma that arose on the mandible and includes magnetic resonance imaging (MRI) and positron emission tomography (PET) findings. On the MRI T1-weighted images, the tumor appeared with signal iso-intensity and was highly and heterogeneously enhanced with contrast material. On the T2-weighted images, it appeared with increased signal intensity. (18) F-fluorodeoxyglucose (FDG)-PET imaging showed abnormal strong accumulation of FDG in the left mandibular region. The tumor was removed by marginal resection of the left mandible under general anesthesia. Histopathological findings revealed that the tumor stroma contained abundant thin-walled vessels. The postoperative course was uneventful, and we found no evidence of recurrence at the postoperative 34-month follow-up

PARP Inhibitor PJ34 Suppresses Osteogenic Differentiation in Mouse Mesenchymal Stem Cells by Modulating BMP-2 Signaling Pathway

Poly(ADP-ribosyl)ation is known to be involved in a variety of cellular processes, such as DNA repair, cell death, telomere regulation, genomic stability and cell differentiation by poly(ADP-ribose) polymerase (PARP). While PARP inhibitors are presently under clinical investigation for cancer therapy, little is known about their side effects. However, PARP involvement in mesenchymal stem cell (MSC) differentiation potentiates MSC-related side effects arising from PARP inhibition. In this study, effects of PARP inhibitors on MSCs were examined. MSCs demonstrated suppressed osteogenic differentiation after 1 μM PJ34 treatment without cytotoxicity, while differentiation of MSCs into chondrocytes or adipocytes was unaffected. PJ34 suppressed mRNA induction of osteogenic markers, such as Runx2, Osterix, Bone Morphogenetic Protein-2, Osteocalcin, bone sialoprotein, and Osteopontin, and protein levels of Bone Morphogenetic Protein-2, Osterix and Osteocalcin. PJ34 treatment also inhibited transcription factor regulators such as Smad1, Smad4, Smad5 and Smad8. Extracellular mineralized matrix formation was also diminished. These results strongly suggest that PARP inhibitors are capable of suppressing osteogenic differentiation and poly(ADP-ribosyl)ation may play a physiological role in this process through regulation of BMP-2 signaling. Therefore, PARP inhibition may potentially attenuate osteogenic metabolism, implicating cautious use of PARP inhibitors for cancer treatments and monitoring of patient bone metabolism levels

Spontaneous Development of Dental Dysplasia in Aged Parp-1 Knockout Mice

Poly(ADP-ribose) polymerase (Parp)-1 catalyzes polyADP-ribosylation using NAD+ and is involved in the DNA damage response, genome stability, and transcription. In this study, we demonstrated that aged Parp-1-/- mouse incisors showed more frequent dental dysplasia in both ICR/129Sv mixed background and C57BL/6 strain compared to aged Parp-1+/+ incisors, suggesting that Parp-1 deficiency could be involved in development of dental dysplasia at an advanced age. Computed tomography images confirmed that dental dysplasia was observed at significantly higher incidences in Parp-1-/- mice. The relative calcification levels of Parp-1-/- incisors were higher in both enamel and dentin (p < 0.05). Immunohistochemical analysis revealed (1) Parp-1 positivity in ameloblasts and odontoblasts in Parp-1+/+ incisor, (2) weaker dentin sialoprotein positivity in dentin of Parp-1-/- incisor, and (3) bone sialoprotein positivity in dentin of Parp-1-/- incisor, suggesting ectopic osteogenic formation in dentin of Parp-1-/- incisor. These results indicate that Parp-1 deficiency promotes odontogenic failure in incisors at an advanced age. Parp-1 deficiency did not affect dentinogenesis during the development of mice, suggesting that Parp-1 is not essential in dentinogenesis during development but is possibly involved in the regulation of continuous dentinogenesis in the incisors at an advanced age

Synergetic Effects of PARP Inhibitor AZD2281 and Cisplatin in Oral Squamous Cell Carcinoma in Vitro and in Vivo

Cisplatin is a commonly used chemotherapeutic drug for treatment of oral carcinoma, and combinatorial effects are expected to exert greater therapeutic efficacy compared with monotherapy. Poly(ADP-ribosyl)ation is reported to be involved in a variety of cellular processes, such as DNA repair, cell death, telomere regulation, and genomic stability. Based on these properties, poly(ADP-ribose) polymerase (PARP) inhibitors are used for treatment of cancers, such as BRCA1/2 mutated breast and ovarian cancers, or certain solid cancers in combination with anti-cancer drugs. However, the effects on oral cancer have not been fully evaluated. In this study, we examined the effects of PARP inhibitor on the survival of human oral cancer cells in vitro and xenografted tumors derived from human oral cancer cells in vivo. In vitro effects were assessed by microculture tetrazolium and survival assays. The PARP inhibitor AZD2281 (olaparib) showed synergetic effects with cisplatin in a dose-dependent manner. Combinatorial treatment with cisplatin and AZD2281 significantly inhibited xenografted tumor growth compared with single treatment of cisplatin or AZD2281. Histopathological analysis revealed that cisplatin and AZD2281 increased TUNEL-positive cells and decreased Ki67- and CD31-positive cells. These results suggest that PARP inhibitors have the potential to improve therapeutic strategies for oral cancer