Probing Spatial Myeloid Heterogeneity in Glioblastoma

https://openworks.mdanderson.org/sumexp22/1015/thumbnail.jp

H19 Functions as a Competing Endogenous RNA to Regulate EMT by Sponging miR-130a-3p in Glioma

Background/Aims: Glioma is one of the most devasting tumors and confers dismal prognosis. Long noncoding RNAs(lncRNAs) have emerged as important regulators in various tumors including glioma. A classic lncRNA-H19, which is found to be highly expressed in human glioma tissues and cell lines, and is associated with tumor progression thus predicating clinical outcomes in glioma patients. However, the overall biological functions and their mechanism of H19 in glioma are not fully understood. Methods: Firstly, we analyzed H19 alterations in different grades of glioma tissues through an analysis of 5 sequencing datasets and qRT-PCR was performed to confirm the results. Next, we evaluated the effect of H19 on glioma cells migration, invasion and EMT process. Luciferase assays and RIP assays were employed to figure out the correlation of H19 and SOX4. Results: H19 was overexpressed in glioma tissues. Down-regulation of H19 led to the inhibition of migration, invasion and EMT process with a reduction in N-cadherin and Vimentin. H19 and SOX4 are both direct target of miR-130a-3p. H19 could compete with SOX4 via sponging miR-130a-3p. Conclusion: Taken together, these results provide a possible function of H19 as an oncogene in glioma tissues and provide a potential new therapeutic strategy for human glioma

Exosomal transfer of miR-1238 contributes to temozolomide-resistance in glioblastomaResearch in context

Background: Although temozolomide (TMZ) resistance is a significant clinical problem in glioblastoma (GBM), its underlying molecular mechanisms are poorly understood. In this study, we identified the role of exosomal microRNAs (miRNAs) from TMZ-resistant cells as important mediators of chemoresistance in GBM cells. Methods: Exosomes were isolated from TMZ-resistant GBM cells and characterized via scanning electron microscopy (SEM). Expression levels of miR-1238 in GBM cell lines and their exosomes, clinical tissues, and sera were evaluated by RT-qPCR. In vitro and in vivo experiments were performed to elucidate the function of exosomal miR-1238 in TMZ resistance in GBM cells. Co-immunoprecipitation assays and western blot analysis were used to investigate the potential mechanisms of miR-1238/CAV1 that contribute to TMZ resistance. Findings: MiR-1238 levels were higher in TMZ-resistant GBM cells and their exosomes than in sensitive cells. Higher levels of miR-1238 were found in the sera of GBM patients than in healthy people. The loss of miR-1238 may sensitize resistant GBM cells by directly targeting the CAV1/EGFR pathway. Furthermore, bioactive miR-1238 may be incorporated into the exosomes shed by TMZ-resistant cells and taken up by TMZ-sensitive cells, thus disseminating TMZ resistance. Interpretation: Our findings establish that miR-1238 plays an important role in mediating the acquired chemoresistance of GBM and that exosomal miR-1238 may confer chemoresistance in the tumour microenvironment. These results suggest that circulating miR-1238 serves as a clinical biomarker and a promising therapeutic target for TMZ resistance in GBM. Fund: This study was supported by the National Natural Science Foundation of China (No·81402056, 81472362, and 81772951) and the National High Technology Research and Development Program of China (863) (No·2012AA02A508). Keywords: Glioblastoma, Temozolomide, Chemoresistance, miRNA, Exosome

Exosomal transfer of long non-coding RNA SBF2-AS1 enhances chemoresistance to temozolomide in glioblastoma

Abstract Background Acquired drug resistance is a constraining factor in clinical treatment of glioblastoma (GBM). However, the mechanisms of chemoresponsive tumors acquire therapeutic resistance remain poorly understood. Here, we aim to investigate whether temozolomide (TMZ) resistance of chemoresponsive GBM was enhanced by long non-coding RNA SBF2 antisense RNA 1 (lncRNA SBF2-AS1) enriched exosomes. Method LncSBF2-AS1 level in TMZ-resistance or TMZ-sensitive GBM tissues and cells were analyzed by qRT-PCR and FISH assays. A series of in vitro assay and xenograft tumor models were performed to observe the effect of lncSBF2-AS1 on TMZ-resistance in GBM. CHIP assay were used to investigate the correlation of SBF2-AS1 and transcription factor zinc finger E-box binding homeobox 1 (ZEB1). Dual-luciferase reporter, RNA immunoprecipitation (RIP), immunofluorescence and western blotting were performed to verify the relation between lncSBF2-AS1, miR-151a-3p and XRCC4. Comet assay and immunoblotting were performed to expound the effect of lncSBF2-AS1 on DNA double-stand break (DSB) repair. A series of in vitro assay and intracranial xenografts tumor model were used to determined the function of exosomal lncSBF2-AS1. Result It was found that SBF2-AS1 was upregulated in TMZ-resistant GBM cells and tissues, and overexpression of SBF2-AS1 led to the promotion of TMZ resistance, whereas its inhibition sensitized resistant GBM cells to TMZ. Transcription factor ZEB1 was found to directly bind to the SBF2-AS1 promoter region to regulate SBF2-AS1 level and affected TMZ resistance in GBM cells. SBF2-AS1 functions as a ceRNA for miR-151a-3p, leading to the disinhibition of its endogenous target, X-ray repair cross complementing 4 (XRCC4), which enhances DSB repair in GBM cells. Exosomes selected from temozolomide-resistant GBM cells had high levels of SBF2-AS1 and spread TMZ resistance to chemoresponsive GBM cells. Clinically, high levels of lncSBF2-AS1 in serum exosomes were associated with poor response to TMZ treatment in GBM patients. Conclusion We can conclude that GBM cells remodel the tumor microenvironment to promote tumor chemotherapy-resistance by secreting the oncogenic lncSBF2-AS1-enriched exosomes. Thus, exosomal lncSBF2-AS1 in human serum may serve as a possible diagnostic marker for therapy-refractory GBM

Fstl1 Promotes Glioma Growth Through the BMP4/Smad1/5/8 Signaling Pathway

Background: Gliomas result in the highest morbidity and mortality rates of intracranial primary central nervous system tumors because of their aggressive growth characteristics and high postoperative recurrence. They are characterized by genetic instability, intratumoral histopathological variability and unpredictable clinical behavior in patients. Proliferation is a key aspect of the clinical progression of malignant gliomas, complicating complete surgical resection and enabling tumor regrowth and further proliferation of the surviving tumor cells. Methods: The expression of Fstl1 was detected by western blotting and qRT-PCR. We used cell proliferation and colony formation assays to measure proliferation. Then, flow cytometry was used to analyze cell cycle progression. The expression of Fstl1, p-Smad1/5/8 and p21 in GBM tissue sections was evaluated using immunohistochemical staining. Furthermore, we used coimmunoprecipitation (Co-IP) and immunoprecipitation to validate the relationship between Fstl1, BMP4 and BMPR2. Finally, we used orthotopic xenograft studies to measure the growth of tumors in vivo. Results: We found that follistatin-like 1 (Fstl1) was upregulated in high-grade glioma specimens and that its levels correlated with poor prognosis. Fstl1 upregulation increased cell proliferation, colony formation and cell cycle progression, while its knockdown inhibited these processes. Moreover, Fstl1 interacted with bone morphogenetic protein (BMP) 4, but not BMP receptor (BMPR) 2, and competitively inhibited their association. Furthermore, Fstl1 overexpression suppressed the activation of the BMP4/Smad1/5/8 signaling pathway, while BMP4 overexpression reversed this effect. Conclusion: Our study demonstrated that Fstl1 promoted glioma growth through the BMP4/Smad1/5/8 signaling pathway, and these findings suggest potential new glioblastoma treatment strategies

Circular RNA AKT3 upregulates PIK3R1 to enhance cisplatin resistance in gastric cancer via miR-198 suppression

Abstract Background Cisplatin (CDDP) treatment is one of the most predominant chemotherapeutic strategies for patients with gastric cancer (GC). A better understanding of the mechanisms of CDDP resistance can greatly improve therapeutic efficacy in patients with GC. Circular RNAs (circRNAs) are a class of noncoding RNAs whose functions are related to the pathogenesis of cancer, but, in CDDP resistance of GC remains unknown. Methods circAKT3 (hsa_circ_0000199, a circRNA originating from exons 8, 9, 10, and 11 of the AKT3 gene) was identified by RNA sequencing and verified by quantitative reverse transcription PCR. The role of circAKT3 in CDDP resistance in GC was assessed both in vitro and in vivo. Luciferase reporter assay, biotin-coupled RNA pull-down and fluorescence in situ hybridization (FISH) were conducted to evaluate the interaction between circAKT3 and miR-198. Functional experiments were measured by western blotting, a cytotoxicity assay, clonogenic assay and flow cytometry. Results The expression of circAKT3 was higher in CDDP-resistant GC tissues and cells than in CDDP-sensitive samples. The upregulation of circAKT3 in GC patients receiving CDDP therapy was significantly associated with aggressive characteristics and was an independent risk factor for disease-free survival (DFS). Our data indicated that circAKT3 promotes DNA damage repair and inhibits the apoptosis of GC cells in vivo and in vitro. Mechanistically, we verified that circAKT3 could promote PIK3R1 expression by sponging miR-198. Conclusions circAKT3 plays an important role in the resistance of GC to CDDP. Thus, our results highlight the potential of circAKT3 as a therapeutic target for GC patients receiving CDDP therapy