lncRNA CASC2/miR­18a­5p axis regulates the malignant potential of nasopharyngeal carcinoma by targeting RBBP8.

Nasopharyngeal carcinoma (NPC) is a prevalent head and neck tumor which has a high mortality rate in Southeast Asia, especially in Southern China. Cancer susceptibility candidate 2 (CASC2) is a newly identified long non­coding RNA (lncRNA) that has been found to play a suppressive role in several types of tumors. However, the expression and functional role of CASC2 in NPC are still unclear. In the present study, using NPC tissues, cells and transplanted mice, we investigated the mechanism of CASC2­mediated regulation of NPC. We showed that the CASC2 level is reduced in NPC tissues and cells. CASC2 downregulation promoted proliferation and inhibited apoptotic cell death in NPC cells. In contrast, CASC2 upregulation inhibited proliferation and increased apoptosis. There were putative binding sites of microRNA (miR)­18a­5p in the promoter of CASC2. The level of miR­18a­5p was upregulated in NPC tissues and cells. We further confirmed that CASC2 could directly bind with miR­18a­5p and inhibit miR­18a­5p expression, using reporter gene and RNA immunoprecipitation assays. miR­18a­5p suppressed CASC2 upregulation­mediated decrease in proliferation and increase in apoptotic cell death. Bioinformatics predicted the putative binding site of miR­18a­5p in the 3' untranslated region of C­terminal binding protein interacting protein (CtIP)/RBBP8. It was further confirmed that miR­18a­5p could directly bind with RBBP8 and inhibit RBBP8 expression. Downregulation of RBBP8 inhibited the anti­miR­18a­5p­mediated increase in apoptosis and decrease in proliferation. Downregulation of CASC2 increased tumor growth, increased the level of miR­18a­5p and decreased RBBP8 expression in vivo. In summary, CASC2 regulates NPC malignancy through modulation of RBBP8 via sponging miR­18a­5p. Our findings highlight the CASC2/miR­18a­5p/RBBP8 axis in NPC pathogenesis and provide new biomarkers and potential targets for the therapy of NPC.

Preoperative evaluation of cochlear implantation through the round window membrane in the facial recess using high-resolution computed tomography.

PURPOSE: We evaluated the risk of cochlear implantation through the round window membrane in the facial recess through a preoperative analysis of the angle between the facial nerve-round window and the cranial midline using high-resolution temporal bone CT. METHODS: Temporal bone CT films of 176 patients with profound sensorineural hearing loss at our hospital from 2013 to 2015 were reviewed. The preoperative temporal bone CT scans of the patients were retrospectively analysed. The vertical distance (d value) from the leading edge of the facial nerve to the posterior wall of the external auditory canal and the angle (α value) between the line from the leading edge of the facial nerve to the midpoint of the round window membrane and the median sagittal line on the round window membrane plane were measured. Based on intraoperative observation, the round window membrane was divided into complete round window membrane exposure (group A), partial exposure (group B), and unexposed (group C) groups, and statistical analysis was performed. RESULTS: The α value could be effectively measured for all 176 patients (62.60 ± 7.12), and the d value could be effectively measured for 95 cases (5.53 ± 1.00). An analysis of the correlation between the α and d values of these 95 cases found a negative correlation. Of the 176 cases, one-way analysis of variance (ANOVA) showed that the differences among the groups were significant [P = 0.000 (< 0.05)]. CONCLUSION: The angle (α value) between the line connecting the leading edge of the facial nerve to the midpoint of the round window and the median sagittal line measured in preoperative CT scans was associated with the difficulty of intraoperatively exposing the round window membrane. When the α value was larger than a certain degree, the difficulty of exposing the round window membrane was increased. In such cases, the surgeon should fully expose the round window membrane during surgery, which could result decrease the likelihood of complications.