Explore the vast range of titles available.

Background Increasing studies have shown that circRNA is closely related to the carcinogenesis and development of many cancers. However, biological functions and the underlying molecular mechanism of circRNAs in triple-negative breast cancer (TNBC) remain largely unclear so far. Methods Here, we investigated the expression pattern of circRNAs in four pairs of TNBC tissues and paracancerous normal tissues using RNA-sequencing. The expression and prognostic significance of circSEPT9 were evaluated with qRT-PCR and in situ hybridization in two TNBC cohorts. The survival curves were drawn by the Kaplan-Meier method, and statistical significance was estimated with the log-rank test. A series of in vitro and in vivo functional experiments were executed to investigate the role of circSEPT9 in the carcinogenesis and development of TNBC. Mechanistically, we explored the potential regulatory effects of E2F1 and EIF4A3 on biogenesis of circSEPT9 with chromatin immunoprecipitation (ChIP), luciferase reporter and RNA immunoprecipitation (RIP) assays. Furthermore, fluorescent in situ hybridization (FISH), luciferase reporter and biotin-coupled RNA pull-down assays were implemented to verify the relationship between the circSEPT9 and miR-637 in TNBC. Results Increased expression of circSEPT9 was found in TNBC tissues, which was positively correlated with advanced clinical stage and poor prognosis. Knockdown of circSEPT9 significantly suppressed the proliferation, migration and invasion of TNBC cells, induced apoptosis and autophagy in TNBC cells as well as inhibited tumor growth and metastasis in vivo. Whereas up-regulation of circSEPT9 exerted opposite effects. Further mechanism research demonstrated that circSEPT9 could regulate the expression of Leukemia Inhibitory Factor (LIF) via sponging miR-637 and activate LIF/Stat3 signaling pathway involved in progression of TNBC. More importantly, we discovered that E2F1 and EIF4A3 might promote the biogenesis of circSEPT9. Conclusions Our data reveal that the circSEPT9 mediated by E2F1 and EIF4A3 facilitates the carcinogenesis and development of triple-negative breast cancer through circSEPT9/miR-637/LIF axis. Therefore, circSEPT9 could be used as a potential prognostic marker and therapeutical target for TNBC.

Background Emerging evidence have illustrated the vital role of long noncoding RNAs (lncRNAs) long intergenic non-protein coding RNA 00511 (LINC00511) on the human cancer progression and tumorigenesis. However, the role of LINC00511 in breast cancer tumourigenesis is still unknown. This research puts emphasis on the function of LINC00511 on the breast cancer tumourigenesis and stemness, and investigates the in-depth mechanism. Methods The lncRNA and RNA expression were measured using RT-PCR. Protein levels were measured using western blotting analysis. CCK-8, colony formation assays and transwell assay were performed to evaluate the cell proliferation ability and invasion. Sphere-formation assay was also performed for the stemness. Bioinformatic analysis, chromatin immunoprecipitation (ChIP) and luciferase reporter assays were carried to confirm the molecular binding. Results LINC00511 was measured to be highly expressed in the breast cancer specimens and the high-expression was correlated with the poor prognosis. Functionally, the gain and loss-of-functional experiments revealed that LINC00511 promoted the proliferation, sphere-formation ability, stem factors (Oct4, Nanog, SOX2) expression and tumor growth in breast cancer cells. Mechanically, LINC00511 functioned as competing endogenous RNA (ceRNA) for miR-185-3p to positively recover E2F1 protein. Furthermore, transcription factor E2F1 bind with the promoter region of Nanog gene to promote it transcription. Conclusion In conclusion, our data concludes that LINC00511/miR-185-3p/E2F1/Nanog axis facilitates the breast cancer stemness and tumorigenesis, providing a vital insight for them.

Genomic analysis of a single metastasis informs about the oncogenic—and potentially druggable—genomic alterations present in other tumors within the same man with metastatic prostate cancer. Tumor heterogeneity may reduce the efficacy of molecularly guided systemic therapy for cancers that have metastasized. To determine whether the genomic alterations in a single metastasis provide a reasonable assessment of the major oncogenic drivers of other dispersed metastases in an individual, we analyzed multiple tumors from men with disseminated prostate cancer through whole-exome sequencing, array comparative genomic hybridization (CGH) and RNA transcript profiling, and we compared the genomic diversity within and between individuals. In contrast to the substantial heterogeneity between men, there was limited diversity among metastases within an individual. The number of somatic mutations, the burden of genomic copy number alterations and aberrations in known oncogenic drivers were all highly concordant, as were metrics of androgen receptor (AR) activity and cell cycle activity. AR activity was inversely associated with cell proliferation, whereas the expression of Fanconi anemia (FA)-complex genes was correlated with elevated cell cycle progression, expression of the E2F transcription factor 1 ( E2F1 ) and loss of retinoblastoma 1 ( RB1 ). Men with somatic aberrations in FA-complex genes or in ATM serine/threonine kinase ( ATM ) exhibited significantly longer treatment-response durations to carboplatin than did men without defects in genes encoding DNA-repair proteins. Collectively, these data indicate that although exceptions exist, evaluating a single metastasis provides a reasonable assessment of the major oncogenic driver alterations that are present in disseminated tumors within an individual, and thus may be useful for selecting treatments on the basis of predicted molecular vulnerabilities.

Increasing evidence has indicated that long noncoding RNAs (lncRNAs) are of great importance in different cell contexts. However, only a very small number of lncRNAs have been experimentally validated and functionally annotated during human hematopoiesis. Here, we report an lncRNA, HOTAIRM1, which is associated with myeloid differentiation and has pivotal roles in the degradation of oncoprotein PML-RARA and in myeloid cell differentiation by regulating autophagy pathways. We first revealed that HOTAIRM1 has different variants that are expressed at different levels in cells and that the expression pattern of HOTAIRM1 is closely related to that of the PML-RARA oncoprotein in acute promyelocytic leukemia (APL) patients. We further revealed that the downregulation of HOTAIRM1 could inhibit all-trans retinoic acid (ATRA) -induced degradation of PML-RARA in APL cells and repress the process of differentiation from promyelocytic to granulocytic cells. More importantly, we found that HOTAIRM1 regulates autophagy and that autophagosome formation was inhibited when HOTAIRM1 expression was reduced in the cells. Finally, through the use of a dual luciferase activity assay, AGO2 RNA immunoprecipitation and RNA pull-down, HOTAIRM1 was revealed to act as a microRNA sponge in a pathway that included miR-20a/106b, miR-125b and their targets ULK1, E2F1 and DRAM2. We constructed a human APL-ascites SCID mouse model to validate the function of HOTAIRM1 and its regulatory pathway in vivo . This is the first report showing that a lncRNAs regulates autophagy and the degradation of the PML-RARA oncoprotein during the process of myeloid cell differentiation blockade, suggesting that lncRNAs may be the potential therapeutic targets for leukemia.

MicroRNAs in Parkinson's Mutations in leucine-rich repeat kinase 2 (LRRK2) have been linked to both familial and sporadic Parkinson's disease, but the biochemical function of LRRK2 has remained elusive. Now that function has been discovered. Both Drosophila and human LRRK2 are shown to antagonize microRNA-mediated translational inhibition of E2F1 and DP transcription factors. LRRK2 interacts with the RNA-induced silencing complex component Argonaute to antagonize its suppressive effect on protein translation. In vivo genetic studies demonstrate a key role for E2F1/DP upregulation in mediating mutant LRRK2 pathogenesis. These findings point to a link between impaired microRNA-mediated silencing and deregulated expression of specific microRNA targets to Parkinson's disease pathogenesis, and suggest possible microRNA-based therapeutic approaches. LRRK2 activity is dysregulated in Parkinson's disease, but how it contributes to the pathogenesis is unknown. These authors show that Drosophila LRRK2 interacts with the Argonaute component (dAgo1) of the RNA-induced silencing complex. This is associated with reduced levels of dAgo1, interaction between phospho-4E-BP1 and hAgo2, and impairment of microRNA-mediated repression. This leads to overexpression of the cell cycle genes e2f1 and dp , and consequent degeneration of dopaminergic neurons. Gain-of-function mutations in leucine-rich repeat kinase 2 (LRRK2) cause familial as well as sporadic Parkinson’s disease characterized by age-dependent degeneration of dopaminergic neurons 1 , 2 . The molecular mechanism of LRRK2 action is not known. Here we show that LRRK2 interacts with the microRNA (miRNA) pathway to regulate protein synthesis. Drosophila e2f1 and dp messenger RNAs are translationally repressed by let-7 and miR-184*, respectively. Pathogenic LRRK2 antagonizes these miRNAs, leading to the overproduction of E2F1/DP, previously implicated in cell cycle and survival control 3 and shown here to be critical for LRRK2 pathogenesis. Genetic deletion of let-7, antagomir-mediated blockage of let-7 and miR-184* action, transgenic expression of dp target protector, or replacement of endogenous dp with a dp transgene non-responsive to let-7 each had toxic effects similar to those of pathogenic LRRK2. Conversely, increasing the level of let-7 or miR-184* attenuated pathogenic LRRK2 effects. LRRK2 associated with Drosophila Argonaute-1 (dAgo1) or human Argonaute-2 (hAgo2) of the RNA-induced silencing complex (RISC). In aged fly brain, dAgo1 protein level was negatively regulated by LRRK2. Further, pathogenic LRRK2 promoted the association of phospho-4E-BP1 with hAgo2. Our results implicate deregulated synthesis of E2F1/DP caused by the miRNA pathway impairment as a key event in LRRK2 pathogenesis and suggest novel miRNA-based therapeutic strategies.

Disruption of the retinoblastoma (RB) tumor suppressor pathway, either through genetic mutation of upstream regulatory components or mutation of RB1 itself, is believed to be a required event in cancer. However, genetic alterations in the RB-regulated E2F family of transcription factors are infrequent, casting doubt on a direct role for E2Fs in driving cancer. In this work, a mutation analysis of human cancer revealed subtle but impactful copy number gains in E2F1 and E2F3 in hepatocellular carcinoma (HCC). Using a series of loss- and gain-of-function alleles to dial E2F transcriptional output, we have shown that copy number gains in E2f1 or E2f3b resulted in dosage-dependent spontaneous HCC in mice without the involvement of additional organs. Conversely, germ-line loss of E2f1 or E2f3b, but not E2f3a, protected mice against HCC. Combinatorial mapping of chromatin occupancy and transcriptome profiling identified an E2F1- and E2F3B-driven transcriptional program that was associated with development and progression of HCC. These findings demonstrate a direct and cell-autonomous role for E2F activators in human cancer.

The lethality, chemoresistance and metastatic characteristics of cancers are associated with phenotypically plastic cancer stem cells (CSCs). How the non-cell autonomous signalling pathways and cell-autonomous transcriptional machinery orchestrate the stem cell-like characteristics of CSCs is still poorly understood. Here we use a quantitative proteomic approach for identifying secreted proteins of CSCs in pancreatic cancer. We uncover that the cell-autonomous E2F1/4-pRb/RBL2 axis balances non-cell-autonomous signalling in healthy ductal cells but becomes deregulated upon KRAS mutation. E2F1 and E2F4 induce whereas pRb/RBL2 reduce WNT ligand expression (e.g. WNT7A, WNT7B, WNT10A, WNT4) thereby regulating self-renewal, chemoresistance and invasiveness of CSCs in both PDAC and breast cancer, and fibroblast proliferation. Screening for epigenetic enzymes identifies GCN5 as a regulator of CSCs that deposits H3K9ac onto WNT promoters and enhancers. Collectively, paracrine signalling pathways are controlled by the E2F-GCN5-RB axis in diverse cancers and this could be a therapeutic target for eliminating CSCs. Cancer stem cells (CSCs) are associated with chemoresistance and poor prognosis in multiple cancer types. Here, the authors investigate the role of secreted Wnt ligands in pancreatic and breast CSCs and identify E2F1/4-GCN5-pRb/RBL2 as a regulatory axis underlying Wnt secretion.

Genomic loss of RB1 is a common alteration in castration-resistant prostate cancer (CRPC) and is associated with poor patient outcomes. RB1 loss is also a critical event that promotes the neuroendocrine transdifferentiation of prostate cancer (PCa) induced by the androgen receptor (AR) signaling inhibition (ARSi). The loss of Rb protein disrupts the Rb-E2F repressor complex and thus hyperactivates E2F transcription activators. While the impact of Rb inactivation on PCa progression and linage plasticity has been previously studied, there is a pressing need to fully understand underlying mechanisms and identify vulnerabilities that can be therapeutically targeted in Rb-deficient CRPC. Using an integrated cistromic and transcriptomic analysis, we have characterized Rb activities in multiple CRPC models by identifying Rb-directly regulated genes and revealed that Rb has distinct binding sites and targets in CRPC with different genomic backgrounds. Significantly, we show that E2F1 chromatin binding and transcription activity in Rb-deficient CRPC are highly dependent on LSD1/KDM1A, and that Rb inactivation sensitizes CRPC tumor to the LSD1 inhibitor treatment. These results provide new molecular insights into Rb activity in PCa progression and suggest that targeting LSD1 activity with small molecule inhibitors may be a potential treatment strategy to treat Rb-deficient CRPC.

The histone variant H2AZ is overexpressed in diverse cancer types where it facilitates the accessibility of transcriptional regulators to the promoters of cell cycle genes. However, the molecular basis for its dysregulation in cancer remains unknown. Here, we report that glioblastomas (GBM) and glioma stem cells (GSCs) preferentially overexpress H2AZ for their proliferation, stemness and tumorigenicity. Chromatin accessibility analysis of H2AZ2 depleted GSC revealed that E2F1 occupies the enhancer region within H2AZ2 gene promoter, thereby activating H2AZ2 transcription. Exploration of other H2AZ2 transcriptional activators using a customized “anti-H2AZ2” query signature for connectivity map analysis identified STAT3. Co-targeting E2F and STAT3 synergistically reduced the levels of H2AZ, histone 3 lysine 27 acetylation (H3K27ac) and cell cycle gene transcription, indicating that E2F1 and STAT3 synergize to activate H2AZ gene transcription in GSCs. Remarkably, an E2F/STAT3 inhibitor combination durably suppresses GSC tumorigenicity in an orthotopic GBM xenograft model. In glioma patients, high STAT3 signaling is associated with high E2F1 and H2AZ2 expression. Thus, GBM has uniquely opted the use of E2F1- and STAT3-containing “enhanceosomes” that integrate multiple signaling pathways to achieve H2AZ gene activation, supporting a translational path for the E2F/STAT3 inhibitor combination to be applied in GBM treatment.

Oxidative stress is a ubiquitous threat to all aerobic organisms and has been implicated in numerous pathological conditions such as cancer. Here we demonstrate a pivotal role for E2F1, a cell cycle regulatory transcription factor, in cell tolerance of oxidative stress. Cells lacking E2F1 are hypersensitive to oxidative stress due to the defects in cell cycle arrest. Oxidative stress inhibits E2F1 transcriptional activity, independent of changes in association with Rb and without decreasing its DNA-binding activity. Upon oxidative insult, SUMO2 is extensively conjugated to E2F1 mainly at lysine 266 residue, which specifically modulates E2F1 transcriptional activity to enhance cell cycle arrest for cell survival. We identify SENP3, a desumoylating enzyme, as an E2F1-interacting partner. Oxidative stress inhibits the interaction between E2F1 and SENP3, which leads to accumulation of sumoylated E2F1. SENP3-deficient cells exhibit hypersumoylation of E2F1 and are resistant to oxidative insult. High levels of SENP3 in breast cancer are associated with elevated levels of E2F targets, high tumor grade, and poor survival. Given the prevalence of elevated levels of SENP3 across numerous cancer types, the SENP3-E2F1 axis may serve as an avenue for therapeutic intervention in cancer.