The N 6 -methyladenosine (m 6 A) modification influences various mRNA metabolic events and tumorigenesis, however, its functions in nonsense-mediated mRNA decay (NMD) and whether NMD detects induced carcinogenesis pathways remain undefined. Here, we showed that the m 6 A methyltransferase METTL3 sustained its oncogenic role by modulating NMD of splicing factors and alternative splicing isoform switches in glioblastoma (GBM). Methylated RNA immunoprecipitation-seq (MeRIP-seq) analyses showed that m 6 A modification peaks were enriched at metabolic pathwayrelated transcripts in glioma stem cells (GSC) compared with neural progenitor cells. In addition, the clinical aggressiveness of malignant gliomas was associated with elevated expression of METTL3. Furthermore, silencing METTL3 or overexpressing dominant-negative mutant METTL3 suppressed the growth and self-renewal of GSCs. Integrated transcriptome and MeRIP-seq analyses revealed that downregulating the expression of METTL3 decreased m 6 A modification levels of serineand arginine-rich splicing factors (SRSF), which led to YTHDC1-dependent NMD of SRSF transcripts and decreased SRSF protein expression. Reduced expression of SRSFs led to larger changes in alternative splicing isoform switches. Importantly, the phenotypes mediated by METTL3 deficiency could be rescued by downregulating BCL-X or NCOR2 isoforms. Overall, these results establish a novel function of m 6 A in modulating NMD and uncover the mechanism by which METTL3 promotes GBM tumor growth and progression.Significance: These findings establish the oncogenic role of m 6 A writer METTL3 in glioblastoma stem cells.

In the present study, we aimed to search for dysregulated lnRNAs in Hepatocellular carcinoma (HCC) tissues, and analyze the relationship of its expression level with the clinicopathological feature and patient prognosis. The biological function of FLVCR1-AS1, the identified lncRNA, in the process of HCC development, and progression was investigated in vitro and in vivo. The underlying molecular mechanism was further explored. We determined FLVCR1-AS1 expression in HCC tissues and peri-tumor tissues by bioinformatic analysis, qRT-PCR, Northern blot and in situ hybridization. The relationship between FLVCR1-AS1 expression level and prognosis was determined by analyzing clinical samples. The effects of FLVCR1-AS1 knockdown on HCC cell proliferation, apoptosis, migration, and invasion were investigated by CCK8, FACS, and tanswell assay, respectively. Tumor xenograft model was used to determine the influence of down-regulated FLVCR1-AS1 on tumor growth and metastasis. lncRNA FLVCR1-AS1 was extremely up-regulated in HCC tissues and cell lines. FLVCR1-AS1 expression level was positively correlated with tumor severity. FLVCR1-AS1 knockdown remarkably inhibited HCC cell proliferation, migration, and invasion in vitro and in vivo while induced cell apoptosis. In mechanism, FLVCR1-AS1 acted as a competitive endogenous RNAs to sponge miR-513c which targeted the mRNA of MET for degradation. By directly sponging miR-513c, FLVCR1-AS1 increased MET expression in HCC, and then promoted HCC progression. It was demonstrated that FLVCR1-AS1 played a positive role in HCC development and progression according to the study in its mechanism, function and clinical manifestation, so that it could be expected to become a new target in HCC prevention and treatment.

N6-methyladenosine (m6A) RNA methylation has recently been found involving in regulatory mechanism of the tumor progression. Our aim was to explore the biological function and clinical significance of the m6A methyltransferase METTL3 in intrahepatic cholangiocarcinoma (ICC). In this study, we revealed that METTL3 was upregulated and predicted poor prognosis of patients with ICC. Multivariate regression analysis demonstrated that METTL3 expression was an independent predictor for overall survival in patients with ICC. Moreover, METTL3 knockdown inhibited ICC progression, while METTL3 overexpression showed the opposite effect. METTL3 inhibitor STM2457 also showed anti-tumor effect in ICC. Mechanistically, METTL3 transcription was driven by H3K4me3 activation. Upregulation of METTL3 mediated m6A modification of IFIT2 mRNA and accelerated IFIT2 mRNA decay in a YTHDF2-dependent manner, which promoted the development of ICC and lead to poorer prognosis. In summary, our findings revealed that H3K4me3 activation-driven METTL3 transcription promotes ICC progression by YTHDF2-mediated IFIT2 mRNA degradation, suggesting that METTL3 may serve as a potential target for human ICC therapy.

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Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignant cancer with complex genomic variations, and no targetable genomic lesions have been found yet. Super‐enhancers (SEs) have been found to contribute to the continuous and robust oncogenic transcription. Here, histone H3 lysine 27 acetylation (H3K27ac) is profiled in PDAC cell lines to establish SE landscapes. Concurrently, it is also shown that PDAC is vulnerable to the perturbation of the SE complex using bromodomain‐containing protein 4 (BRD4) inhibitor, JQ1, synergized with cyclin‐dependent kinase 7 (CDK7) inhibitor, THZ1. Formulations of hydrophobic l‐phenylalanine‐poly (ester amide) nanoparticles (NPs) with high drug loading of JQ1 and THZ1 (J/T@8P4s) are further designed and developed. J/T@8P4s is assessed for size, encapsulation efficiency, morphology, drug release profiles, and drug uptake in vitro. Compared to conventional free drug formulation, the nanodelivery system dramatically reduces the hepatotoxicity while significantly enhancing the tumor inhibition effects and the bioavailability of incorporated JQ1 and THZ1 at equal doses in a Gemcitabine‐resistant PDAC patient‐derived xenograft (PDX) model. Overall, the present study demonstrates that the J/T@8P4s can be a promising therapeutic treatment against the PDAC via suppression of SE‐associated oncogenic transcription, and provides a strategy utilizing NPs to assist the drug delivery targeting SEs.

BackgroundIntrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer. The dismal outcome of ICC patients is due to lack of early diagnosis, the aggressive biological behavior of ICC and the lack of effective therapeutic options. Early diagnosis and prognosis of ICC by non-invasive methods would be helpful in providing valuable information and developing effective treatment strategies.MethodsExpression of microfibrillar-associated protein 5 (MFAP5) in the serum of ICC patients was detected by ELISA. Human ICC specimens were immunostained by MFAP5 antibodies. The growth rate of human ICC cell lines treated with MFAP5 or MFAP5 shRNAs was examined by CCK8 and colony formation assays. Cell cycle analysis was performed with PI staining. The effect of MFAP5 inhibition was assessed by xenograft models in nude mice. RNA-seq and ATAC-seq analyses were used to dissect the molecular mechanism by which MFAP5 promoted ICC aggressiveness.ResultsWe identified MFAP5 as a biomarker for the diagnosis and prognosis of ICC. Upregulated MFAP5 is a common feature in aggressive ICC patients’ tissues. Importantly, MFAP5 level in the serum of ICC patients and healthy individuals showed significant differential expression profiles. Furthermore, we showed that MFAP5 promoted ICC cell growth and G1 to S-phase transition. Using RNA-seq expression and ATAC-seq chromatin accessibility profiling of ICC cells with suppressed MFAP5 secretion, we showed that MFAP5 regulated the expression of genes involved in the Notch1 signaling pathway. Furthermore, FLI-06, a Notch signaling inhibitor, completely abolished the MFAP5-dependent transcriptional programs.ConclusionsRaised MFAP5 serum level is useful for differentiating ICC patients from healthy individuals, and could be helpful in ICC diagnosis, prognosis and therapies.

Background Intrahepatic cholangiocarcinoma (ICC) is an aggressive cancer with exceedingly poor prognosis, and chemoresistance is a huge challenge for treatment. N6‐methyladenosine (m 6 A) modification plays an important role in the progression and chemoresistance of cancers. We aimed to investigate the oncogenic function and therapeutic significance of the m 6 A binding protein, YTH domain family 2 (YTHDF2), in ICC progression and cisplatin‐based chemotherapy. Methods Several independent data sets were used to assess the expression of YTHDF2 in ICC, particularly in chemoresistant ICC. Knockdown and overexpression were used to evaluate the effects of YTHDF2 on tumourigenesis and cisplatin response in ICC. Multi‐omics sequencing was performed to identify target genes. RIP, dual luciferase reporter, RNA stability experiment and loss‐of‐function assays were conducted to study the mechanisms underlying the oncogenic function of YTHDF2. Furthermore, patient‐derived xenograft (PDX) model was established to determine the effect of combination treatment of YTHDF2 siRNA and cisplatin in ICC. Results Our study showed that YTHDF2 was upregulated in ICC tissues, particularly in chemoresistant ICC tissues, and correlated with poor prognosis. Furthermore, silencing YTHDF2 led to inhibited proliferation, promoted apoptosis and G0/G1 cell cycle arrest. Its downregulation also enhanced DNA damage and sensitised ICC cells to cisplatin. YTHDF2 overexpression exerted the opposite results. Integration analysis using RNA‐seq, MeRIP‐seq and anti‐YTHDF2 RIP‐seq elucidated the role of YTHDF2 in tumourigenesis and cisplatin‐desensitising function by promoting the degradation of cyclin‐dependent kinase inhibitor 1B (CDKN1B) mRNA in an m 6 A‐dependent manner. Downregulation of CDKN1B increased the YTHDF2 silencing‐induced influence on tumourigenesis and cisplatin response to ICC. In addition, the combination treatment of YTHDF2 siRNA and cisplatin significantly enhanced the anti‐tumour effect of cisplatin in a chemoresistant ICC PDX model. Conclusions YTHDF2 exhibits tumour oncogenic and cisplatin‐desensitising properties, which may offer insight into the development of novel combination therapeutic strategies for ICC.

Intrahepatic cholangiocarcinoma (ICC) is a lethal malignancy with high mortality and lack of effective therapeutic targets. Here, we found that expression of cyclin-dependent kinase 7 (CDK7) was significantly associated with higher tumor grade and worse prognosis in 96 ICC specimens. Depletion of CDK7 significantly inhibited cell growth, induced a G2/M cell cycle arrest, and reduced the migratory and invasive potential in ICC cells. Subsequent experiments demonstrated that ICC cells were highly sensitive to the CDK7 inhibitor THZ1. A low concentration of THZ1 markedly inhibited cell growth, cell cycle, migration, and invasion in ICC cell lines. RNA-sequencing (RNA-seq) analysis revealed that THZ1 treatment decreased the levels of massive oncogene transcripts, particularly those associated with cell cycle and cell migration. Quantitative reverse transcriptase PCR (qRT-PCR) analysis confirmed that transcription of oncogenes involved in cell cycle regulation (AURKA, AURKB, CDC25B, CDK1, CCNA2, and MKI67) and the c-Met pathway (c-Met, AKT1, PTK2, CRK, PDPK1, and ARF6) was selectively repressed by THZ1. In addition, THZ1 exhibited significant anti-tumor activity in a patient-derived xenograft (PDX) model of ICC, without causing detectable side effects.