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BackgroundChemoresistance to temozolomide (TMZ) is a major challenge in the treatment of glioblastoma (GBM). We previously found that miR-519a functions as a tumor suppressor in glioma by targeting the signal transducer and activator of transcription 3 (STAT3)-mediated autophagy oncogenic pathway. Here, we investigated the effects of miR-519a on TMZ chemosensitivity and autophagy in GBM cells. Furthermore, the underlying molecular mechanisms and signaling pathways were explored.MethodsIn the present study, two stable TMZ-resistant GBM cell lines were successfully generated by exposure of parental cells to a gradually increasing TMZ concentration. After transfecting U87-MG/TMZ and U87-MG cells with miR-519a mimic or inhibitor, a series of biochemical assays such as MTT, apoptosis, and colony formation were performed to determine the chemosensitive response to TMZ. The autophagy levels in GBM cells were detected by transmission electron microscopy, LC3B protein immunofluorescence, and Western blotting analysis. Stable knockdown and overexpression of miR-519a in GBM cells were established using lentivirus. A xenograft nude mouse model and in situ brain model were used to examine the in vivo effects of miR-519a. Tumor tissue samples were collected from 48 patients with GBM and were used to assess the relationship between miR-519a and STAT3 expression.ResultsTMZ treatment significantly upregulated miR-519a in U87-MG cells but not in U87-MG/TMZ cells. Moreover, the expression of miR-519a and baseline autophagy levels was lower in U87-MG/TMZ cells as compared to U87-MG cells. miR-519a dramatically enhanced TMZ-induced autophagy and apoptotic cell death in U87-MG/TMZ cells, while inhibition of miR-519a promoted TMZ resistance and reduced TMZ-induced autophagy in U87-MG cells. Furthermore, miR-519a induced autophagy through modification of STAT3 expression. The in vivo results showed that miR-519a can enhance apoptosis and sensitized GBM to TMZ treatment by promoting autophagy and targeting the STAT3/Bcl-2/Beclin-1 pathway. In human GBM tissues, we found an inverse correlation between miR-519a and STAT3 expression.ConclusionsOur results suggested that miR-519a increased the sensitivity of GBM cells to TMZ therapy. The positive effects of miR-519a may be mediated through autophagy. In addition, miR-519a overexpression can induce autophagy by inhibiting STAT3/Bcl-2 pathway. Therefore, a combination of miR-519a and TMZ may represent an effective therapeutic strategy in GBM.Electronic supplementary materialThe online version of this article (10.1186/s13045-018-0618-0) contains supplementary material, which is available to authorized users.

The results suggest that up-regulation of Lgr5 expression, especially in female patients, may play an important role in colorectal carcinogenesis, probably through the WNT/beta-catenin pathway, but not involve the progression of the CRC.

The vitellogenin receptor (VgR) belongs to the low-density lipoprotein receptor (LDLR) superfamily, and is an important carrier for the uptake of vitellogenin (Vg) into developing oocytes of all oviparous species. The first full-length message for a VgR from a Lepidopteran insect was cloned and sequenced from the ovary of Spodoptera litura Fabricius (GenBank accession no. GU983858). The coding region consisted of 5370 bp flanked by a 49 bp 5'-untranslated region (UTR) and a 177 bp 3'-UTR, which encoded a 1798-residue protein with a predicted molecular weight (MW) of 201.69 kDa. S. litura VgR (SlVgR)comprised two ligand binding sites with four LDLR class A repeats in the first domain and seven in the second domain, an epidermal growth factor-like domain containing an LDLR class B repeat and a YWXD motif, a transmembrane domain and a cytoplasmic domain. A phylogenetic relationship placed SlVgR as a separate group from the other insects. SlVgR messenger RNA (mRNA) was specifically expressed in the ovarian tissues. The developmental expression patterns showed that VgR mRNA was first transcribed in 6(th) day female pupae and the maximum level of VgR mRNA appeared in 36-h-old adults. Immunoblot analysis detected an ovary-specific VgR protein with a MW of ∼200 kDa, whose development profiles were consistent with VgR mRNA expression patterns. RNA inteference (RNAi) specifically disrupted the VgR gene by injection of 3 or 5 µg VgR double-stranded RNA per insect in 4(th) or 6(th) day pupae. RNAi of SlVgR led to a phenotype characterized by high Vg accumulation in the haemolymph, low Vg deposition in the ovary and the failure of insect spawning. These results mean that VgR is critical for binding Vg and transporting it into the oocytes of the insect ovary, thus playing an important role in insect reproduction.