BackgroundWhile treatment failure in cases of head and neck squamous cell carcinoma (HNSCC) frequently takes the form of locoregional recurrences and distant metastasis, our understanding of the mechanisms of metastasis in HNSCC is limited. We initially performed the upstream and key nodes analysis together with whole gene microarray analysis characterized by distant metastatic potential in vivo with HNSCC cell lines and identified JunB, a member of the activator protein-1 (AP-1) family, as a key molecule in the regulation of the pathways related to distant metastasis in HNSCC. We have therefore tested the hypothesis that JunB plays a crucial role in distant metastasis in HNSCC.MethodsTo study the role of JunB on metastatic potential of HNSCC, small interfering RNA (siRNA)-mediated knockdown and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (cas9) system (CRISPR/Cas9)-mediated knockout of JunB in HNSCC cells were established and the abilities of cell invasion and migration in vitro were examined. The efficacy of knockout of JunB was also examined using an experimental lung metastatic mouse model of HNSCC. In addition, to study if the role of JunB in HNSCC cell migration and invasiveness is related to epithelial-to-mesenchymal transition (EMT), cell morphology and expression of mesenchymal or epithelial marker on siRNA mediated JunB knockdown in HNSCC cells were examined with or without TGF-β stimulation.ResultssiRNA knockdown and sgRNA knockout of JunB in metastatic HNSCC cells significantly suppressed both cell invasion and migration in vitro. In addition, the knockout of JunB in metastatic HNSCC cells significantly repressed the incidence of lung metastases and prolonged the survival in vivo. However, we did not observe any change in cell morphology with the down-regulation of mesenchymal markers and up-regulation of epithelial markers in response to siRNA-mediated JunB knockdown in HNSCC cells.ConclusionThese results suggested that JunB could play an important role in promoting cell invasion, migration and distant metastasis in HNSCC via pathways other than EMT and that the down-regulation of JunB may become an effective strategy for patients with invasive HNSCC.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-016-0284-4) contains supplementary material, which is available to authorized users.

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Recent studies showed that human papillomavirus (HPV) integration contributes to the genomic instability seen in HPV-associated head and neck squamous cell carcinoma (HPV-HNSCC). However, the epigenetic alterations induced after HPV integration remains unclear. To identify the molecular details of HPV16 DNA integration and the ensuing patterns of methylation in HNSCC, we performed next-generation sequencing using a target-enrichment method for the effective identification of HPV16 integration breakpoints as well as the characterization of genomic sequences adjacent to HPV16 integration breakpoints with three HPV16-related HNSCC cell lines. The DNA methylation levels of the integrated HPV16 genome and that of the adjacent human genome were also analyzed by bisulfite pyrosequencing. We found various integration loci, including novel integration sites. Integration loci were located predominantly in the intergenic region, with a significant enrichment of the microhomologous sequences between the human and HPV16 genomes at the integration breakpoints. Furthermore, various levels of methylation within both the human genome and the integrated HPV genome at the integration breakpoints in each integrant were observed. Allele-specific methylation analysis suggested that the HPV16 integrants remained hypomethylated when the flanking host genome was hypomethylated. After integration into highly methylated human genome regions, however, the HPV16 DNA became methylated. In conclusion, we found novel integration sites and methylation patterns in HPV-HNSCC using our unique method. These findings may provide insights into understanding of viral integration mechanism and virus-associated carcinogenesis of HPV-HNSCC.

Sensorineural hearing loss (SNHL) caused by noise exposure and attendant loss of glutamatergic synapses between cochlear spiral ganglion neurons (SGNs) and hair cells is the most common sensory deficit worldwide. We show here that systemic administration of a bisphosphonate to mice 24 h after synaptopathic noise exposure regenerated synapses between inner hair cells and SGNs and restored cochlear function. We further demonstrate that this effect is mediated by inhibition of the mevalonate pathway. These results are highly significant because they suggest that bisphosphonates could reverse cochlear synaptopathy for the treatment of SNHL.