TGF-β1 modulates temozolomide resistance in glioblastoma via altered microRNA processing and elevated MGMT

XPA Enhances Temozolomide Resistance of Glioblastoma Cells by Promoting Nucleotide Excision Repair

Glioblastoma is the most frequent, as well as aggressive kind of high-grade malignant glioma. Chemoresistance is posing a significant clinical barrier to the efficacy of temozolomide-based glioblastoma treatment. By suppressing xeroderma pigmentosum group A (XPA), a pivotal DNA damage recognition protein implicated in nucleotide excision repair (NER), we devised a novel method to enhance glioblastoma therapy and alleviate temozolomide resistance. On the basis of preliminary assessment, we found that XPA dramatically increased in glioblastoma compared with normal cells and contributed to temozolomide resistance. By constructing XPA stably knockdown cells, we illustrate that XPA protects glioma cells from temozolomide-triggered reproductive cell death, apoptosis, as well as DNA repair. Besides, XPA silencing remarkably enhances temozolomide efficacy in vivo. This study revealed a crucial function of XPA-dependent NER in the resistance of glioma cells to temozolomide.

Emerging role and function of miR-198 in human health and diseases

Ever since their discovery, microRNAs (miRNAs/miRs) have astonished us by the plethora of processes they regulate, and thus adding another dimension to the gene regulation. They have been implicated in several diseases affecting cardiovascular, neurodegenerative, hepatic, autoimmune and inflammatory functions. A primate specific exonic miRNA, miR-198 has been vastly studied during the past decade, and shown to have a critical role in wound healing. The aberrant expression of miR-198 was first reported in schizophrenia, linking it to neural development. Later, its dysregulation and tumor suppressive role was reported in hepatocellular carcinoma. However, this was just a beginning, and after which there was an explosion of reports linking miR-198 deregulation to cancers and other ailments. The first target to be identified for miR-198 was Cyclin T1 in monocytes affecting HIV1 replication. Depending on the type of cancer, miR-198 has been shown to function either as a tumor suppressor or an oncomir. Interestingly, miR-198 is not only known to regulate multiple targets and pathways, but also is itself regulated by several circular RNAs and long-non-coding RNAs, highlighting a complex regulatory network. This review highlights the currently understood mechanism and regulation of miR-198 in different diseases, and its possible diagnostic and therapeutic potential.

Long non-coding RNA (lncRNA) HOXD-AS2 promotes glioblastoma cell proliferation, migration and invasion by regulating the miR-3681-5p/MALT1 signaling pathway

Glioblastoma (GBM) is the most lethal type of brain cancer. An increasing number of studies suggest that long non-coding RNAs (lncRNAs) are implicated in tumor progression. LncRNA HOXD-AS2 was reported to be highly expressed in glioma and associated with glioma grade and poor prognosis. However, the molecular mechanism remains to be elucidated. In this study, we first analyzed differentially expressed lncRNAs in glioblastoma using RNA-seq dataset (156 GBM samples and 5 adjacent normal samples in TCGA (Cancer Genome Atlas) and GTEx (Genotype-Tissue Expression) database). HOXD-AS2 was found to be significantly up-regulated in GBM tissues, which was further confirmed in GBM patient tumor samples and GBM cell lines. Silencing HOXD-AS2 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis. We further identified and validated miR-3681-5p as a target of HOXD-AS2, and miR-3681-5p was negatively regulated by HOXD-AS2. By negatively affecting miR-3681-5p, HOXD-AS2 could promote the expression of MALT1 to augment the aggressiveness of GBM cells. miR-3681-5p overexpression or MALT1 knockdown attenuated aggressiveness of GBM cells. Importantly, silencing HOXD-AS2 suppressed tumorigenesis of GBM cells in the xenograft mouse model. Collectively, our study clarified the role of miR-3681-5p/MALT1 axis underlying the oncogenic function of lncRNA HOXD-AS2 in GBM. Future work is required to study the mechanism by which HOXD-AS2 is upregulated in GBM cells, which can provide novel insights into therapeutic intervention for GBM treatment.

LINC00511 facilitates Temozolomide resistance of glioblastoma cells via sponging miR-126-5p and activating Wnt/β-catenin signaling

Temozolomide (TMZ) is the first-line chemotherapy drug for glioblastoma (GBM) but acquired TMZ resistance is frequently observed. Thus, a TMZ resistant GBM cell line U87-R was established to search for potential long noncoding RNAs (lncRNAs) used in TMZ resistance. In our study, LINC00511 was identified as a TMZ resistance-associated lncRNA in U87-R cells by transcriptome RNA sequencing. The potential functions of LINC00511 were evaluated by quantitative real-time polymerase chain reaction, cell viability assay, colony formation assay, western blot, soft agar assay, flow cytometry, tumor xenograft model, immunofluorescence, sphere formation assay, fluorescent in situ hybridization, luciferase reporter assay, and RNA pull-down assay. We found that LINC00511 was upregulated in U87-R cells and GBM samples, and correlated with poor prognosis of GBM patients. Silencing LINC00511 impaired TMZ tolerance of U87-R cells, while LINC00511 overexpression increased TMZ resistance of sensitive GBM cells. Wnt/β-catenin signaling was activated in U87-R cells, and inhibiting Wnt/β-catenin signaling enhanced TMZ sensitivity. Furthermore, LINC00511 was mainly distributed in the cytoplasm of GBM cells and regulated Wnt/β-catenin activation by acting as a molecular sponge for miR-126-5p. Multiple genes of Wnt/β-catenin signaling such as DVL3, WISP1, and WISP2 were targeted by miR-126-5p. MiR-126-5p restoration impaired TMZ resistance of GBM cells. In conclusion, our results provided a novel insight into acquired TMZ resistance of GBM cells and suggested LINC00511 as a potential biomarker or therapeutic target for GBM patients.

Long non-coding RNA H19 promotes myoblast fibrogenesis via regulating the miR-20a-5p-Tgfbr2 axis

Emerging evidence has indicated long non-coding RNAs (lncRNAs) play important roles in diverse biological processes, including fibrosis. Here, we report that lncRNA H19 is able to promote skeletal muscle fibrosis. lnc-H19 was identified to be highly expressed in skeletal muscle fibrosis in vivo and in vitro; while lnc-H19 knockdown attenuated fibrosis in vitro. The knockdown of lnc-H19 was proved to inhibit the activation of the TGFβ/Smad pathway in C2C12 myoblasts by sponging miR-20a-5p to regulate Tgfbr2 expression through the competing endogenous RNA function. Our study elucidates the roles of the lnc-H19-miR-20a-5p-Tgfbr2 axis in regulating the TGFβ/Smad pathway of myoblast fibrogenesis, which might provide a promising therapeutic target for skeletal muscle fibrosis.