Fusobacterium nucleatum outer membrane vesicles activate autophagy to promote oral cancer metastasis.

INTRODUCTION: Metastasis is an important cause of high mortality and lethality of oral cancer. Fusobacterium nucleatum (Fn) can promote tumour metastasis. Outer membrane vesicles (OMVs) are secreted by Fn. However, the effects of Fn-derived extracellular vesicles on oral cancer metastasis and the underlying mechanisms are unclear. OBJECTIVES: We aimed to determine whether and how Fn OMVs mediate oral cancer metastasis. METHODS: OMVs were isolated from brain heart infusion (BHI) broth supernatant of Fn by ultracentrifugation. Tumour-bearing mice were treated with Fn OMVs to evaluate the effect of OMVs on cancer metastasis. Transwell assays were performed to determine how Fn OMVs affect cancer cell migration and invasion. The differentially expressed genes in Fn OMV-treated/untreated cancer cells were identified by RNA-seq. Transmission electron microscopy, laser confocal microscopy, and lentiviral transduction were used to detect changes in autophagic flux in cancer cells stimulated with Fn OMVs. Western blotting assay was performed to determine changes in EMT-related marker protein levels in cancer cells. Fn OMVs' effects on migration after blocking autophagic flux by autophagy inhibitors were determined by in vitro and in vivo experiments. RESULTS: Fn OMVs were structurally similar to vesicles. In the in vivo experiment, Fn OMVs promoted lung metastasis in tumour-bearing mice, while chloroquine (CHQ, an autophagy inhibitor) treatment reduced the number of pulmonary metastases resulting from the intratumoral Fn OMV injection. Fn OMVs promoted the migration and invasion of cancer cells in vivo, leading to altered expression levels of EMT-related proteins (E-cadherin downregulation; Vimentin/N-cadherin upregulation). RNA-seq showed that Fn OMVs activate intracellular autophagy pathways. Blocking autophagic flux with CHQ reduced in vitro and in vivo migration of cancer cells induced by Fn OMVs as well as reversed changes in EMT-related protein expression. CONCLUSION: Fn OMVs not only induced cancer metastasis but also activated autophagic flux. Blocking autophagic flux weakened Fn OMV-stimulated cancer metastasis.

[Effect of boron and fluoride on the expression of enamelin in rat incisor].

OBJECTIVE: To investigate the effects of overdose fluoride, boron and two factors on the expression of enamelin in rat incisor. METHODS: 32 Wistar rats were randomly divided into 4 groups. Group I: The distilled water was given. Group II: 220 mg/L NaF were given. Group III: 382 mg/L Na2B4O2.10H2O were given. Group IV: 220 mg/L NaF and 382 mg/L Na2B4O2.10H2O were given. The rats were sacrificed in the eighth week. HE staining was used to observe the morphology of ameloblasts. Immunohistochemical staining was used for study the expression of enamelin in rat incisors. RESULTS: The results showed that the expression of enamelin was reduced in the group II (P<0.01). Compared with group I, the expression of enamelin in group IV had no significant difference. The expression of enamelin in group IV and group II had significant difference (P<0.01). CONCLUSION: The overdose fluoride can inhibit the expression of enamelin. The effection was weaken when boron added. Boron reduced the toxicity of fluoride on teeth.