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

[Display omitted] •In vivo, Fn OMVs promoted lung metastasis in tumour-bearing mice, while chloroquine (CHQ; an autophagy inhibitor) reduced the number of pulmonary metastases resulting from intratumoral Fn OMV injection.•Fn OMVs promoted cancer cell invasion and migration in vivo, leading to changes in the expression of EMT related proteins.•RNA-seq showed that Fn OMVs activate intracellular autophagy pathways. Blocking autophagic flux with CHQ not only reduced Fn OMV-induced cancer cell migration in vitro and in vivo but also reversed the expression changes in EMT-related proteins. 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. We aimed to determine whether and how Fn OMVs mediate oral cancer metastasis. 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. 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 i