Functional Landscape of PCGF Proteins Reveals Both RING1A/B-Dependent-and RING1A/B-Independent-Specific Activities.

Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) control cell identity by establishing facultative heterochromatin repressive domains at common sets of target genes. PRC1, which deposits H2Aub1 through the E3 ligases RING1A/B, forms six biochemically distinct subcomplexes depending on the assembled PCGF protein (PCGF1-PCGF6); however, it is yet unclear whether these subcomplexes have also specific activities. Here we show that PCGF1 and PCGF2 largely compensate for each other, while other PCGF proteins have high levels of specificity for distinct target genes. PCGF2 associates with transcription repression, whereas PCGF3 and PCGF6 associate with actively transcribed genes. Notably, PCGF3 and PCGF6 complexes can assemble and be recruited to several active sites independently of RING1A/B activity (therefore, of PRC1). For chromatin recruitment, the PCGF6 complex requires the combinatorial activities of its MGA-MAX and E2F6-DP1 subunits, while PCGF3 requires an interaction with the USF1 DNA binding transcription factor.

LncRNA TMPO-AS1 promotes LCN2 transcriptional activity and exerts oncogenic functions in ovarian cancer.

Ovarian cancer remains the sixth most frequently occurring cancer in women worldwide. Long noncoding RNAs (lncRNAs) are capable of regulating gene expression, and thus, participating in a wide range of biological functions and disease processes including cancer development. Our work suggests that lncRNA TMPO antisense RNA 1 (TMPO-AS1) represents an oncogenic lncRNA in ovarian cancer and presents a novel mechanism involving transcription factor E2F transcription factor 6 (E2F6) and lipocalin-2 (LCN2). We identified upregulated lncRNA TMPO-AS1 in ovarian cancer tissues and cells. siRNA-mediated silencing of lncRNA TMPO-AS1 restrained the aggressiveness of ovarian cancer cells and their pro-angiogenic ability, and reduced the expression of LCN2. LncRNA TMPO-AS1 was found to interact with E2F6, a transcriptional repressor that could bind to the promoter region of LCN2 gene. In addition, silencing of E2F6 or overexpression of LCN2 restored the aggressiveness of ovarian cancer cells and their pro-angiogenic ability following siRNA-mediated silencing of lncRNA TMPO-AS1. Taken together, we demonstrated lncRNA TMPO-AS1 could potentially promote LCN2 transcriptional activity by binding to transcription factor E2F6, and thus, stimulated the progression of ovarian cancer. These findings underscore a possible alternative therapeutic strategy for ovarian cancer treatment.

MGA, L3MBTL2 and E2F6 determine genomic binding of the non-canonical Polycomb repressive complex PRC1.6.

Diverse Polycomb repressive complexes 1 (PRC1) play essential roles in gene regulation, differentiation and development. Six major groups of PRC1 complexes that differ in their subunit composition have been identified in mammals. How the different PRC1 complexes are recruited to specific genomic sites is poorly understood. The Polycomb Ring finger protein PCGF6, the transcription factors MGA and E2F6, and the histone-binding protein L3MBTL2 are specific components of the non-canonical PRC1.6 complex. In this study, we have investigated their role in genomic targeting of PRC1.6. ChIP-seq analysis revealed colocalization of MGA, L3MBTL2, E2F6 and PCGF6 genome-wide. Ablation of MGA in a human cell line by CRISPR/Cas resulted in complete loss of PRC1.6 binding. Rescue experiments revealed that MGA recruits PRC1.6 to specific loci both by DNA binding-dependent and by DNA binding-independent mechanisms. Depletion of L3MBTL2 and E2F6 but not of PCGF6 resulted in differential, locus-specific loss of PRC1.6 binding illustrating that different subunits mediate PRC1.6 loading to distinct sets of promoters. Mga, L3mbtl2 and Pcgf6 colocalize also in mouse embryonic stem cells, where PRC1.6 has been linked to repression of germ cell-related genes. Our findings unveil strikingly different genomic recruitment mechanisms of the non-canonical PRC1.6 complex, which specify its cell type- and context-specific regulatory functions.

E2F6 functions as a competing endogenous RNA, and transcriptional repressor, to promote ovarian cancer stemness.

Ovarian cancer is the most lethal cancer of the female reproductive system. In that regard, several epidemiological studies suggest that long-term exposure to estrogen could increase ovarian cancer risk, although its precise role remains controversial. To decipher a mechanism for this, we previously generated a mathematical model of how estrogen-mediated upregulation of the transcription factor, E2F6, upregulates the ovarian cancer stem/initiating cell marker, c-Kit, by epigenetic silencing the tumor suppressor miR-193a, and a competing endogenous (ceRNA) mechanism. In this study, we tested that previous mathematical model, showing that estrogen treatment of immortalized ovarian surface epithelial cells upregulated both E2F6 and c-KIT, but downregulated miR-193a. Luciferase assays further confirmed that microRNA-193a targets both E2F6 and c-Kit. Interestingly, ChIP-PCR and bisulphite pyrosequencing showed that E2F6 also epigenetically suppresses miR-193a, through recruitment of EZH2, and by a complex ceRNA mechanism in ovarian cancer cell lines. Importantly, cell line and animal experiments both confirmed that E2F6 promotes ovarian cancer stemness, whereas E2F6 or EZH2 depletion derepressed miR-193a, which opposes cancer stemness, by alleviating DNA methylation and repressive chromatin. Finally, 118 ovarian cancer patients with miR-193a promoter hypermethylation had poorer survival than those without hypermethylation. These results suggest that an estrogen-mediated E2F6 ceRNA network epigenetically and competitively inhibits microRNA-193a activity, promoting ovarian cancer stemness and tumorigenesis.

Nuclear receptor TLX regulates islet beta cell proliferation via E2F6.

Both type 1 and type 2 diabetes are associated with loss of functional beta cell mass, and strategies to restore beta cells are urgently needed. We reported previously that overexpression of the nuclear receptor TLX induces beta cell proliferation, but the underlying molecular mechanism has not been defined. Here, we identified direct targets of TLX in beta cells at the genome-wide level by ChIP-Seq. These targets include a cadre of regulators that are known to be critical for proliferation. Among these ChIP targets, E2F6 was tightly associated with the cell cycle modules, and thus, we further analyzed E2F6 expression and function in beta cells. We showed that E2F6 is strongly downregulated by TLX, and its expression inhibits beta cell proliferation. Moreover, coexpression of E2F6 with TLX partially abrogated the proliferative effects of TLX. These results strongly suggest that TLX acts through E2F6 to regulate beta cell proliferation. Together, the results of this study reveal a direct interaction between TLX and E2F6 and suggest new targets for the expansion of functional beta cell mass.

EBV Nuclear Antigen 3C Mediates Regulation of E2F6 to Inhibit E2F1 Transcription and Promote Cell Proliferation.

Epstein-Barr virus (EBV) is considered a ubiquitous herpesvirus with the ability to cause latent infection in humans worldwide. EBV-association is evidently linked to different types of human malignancies, mainly of epithelial and lymphoid origin. Of interest is the EBV nuclear antigen 3C (EBNA3C) which is critical for EBV-mediated immortalization. Recently, EBNA3C was shown to bind the E2F1 transcription regulator. The E2F transcription factors have crucial roles in various cellular functions, including cell cycle, DNA replication, DNA repair, cell mitosis, and cell fate. Specifically, E2F6, one of the unique E2F family members, is known to be a pRb-independent transcription repressor of E2F-target genes. In our current study, we explore the role of EBNA3C in regulating E2F6 activities. We observed that EBNA3C plays an important role in inducing E2F6 expression in LCLs. Our study also shows that EBNA3C physically interacts with E2F6 at its amino and carboxy terminal domains and they form a protein complex in human cells. In addition, EBNA3C stabilizes the E2F6 protein and is co-localized in the nucleus. We also demonstrated that both EBNA3C and E2F6 contribute to reduction in E2F1 transcriptional activity. Moreover, E2F1 forms a protein complex with EBNA3C and E2F6, and EBNA3C competes with E2F1 for E2F6 binding. E2F6 is also recruited by EBNA3C to the E2F1 promoter, which is critical for EBNA3C-mediated cell proliferation. These results demonstrate a critical role for E2F family members in EBV-induced malignancies, and provide new insights for targeting E2F transcription factors in EBV-associated cancers as potential therapeutic intervention strategies.

Oct3/4 directly regulates expression of E2F3a in mouse embryonic stem cells.

Embryonic stem (ES) cells, derived from the inner cell mass of blastocysts, have a characteristic cell cycle with truncated G1 and G2 phases. Recent findings that suppression of Oct3/4 expression results in a reduced proliferation rate of ES cells suggest the involvement of Oct3/4 in the regulation of ES cell growth, although the underlying molecular mechanism remains unclear. In the present study, we identified E2F3a as a direct target gene of Oct3/4 in ES cells. Oct3/4 directly bound to the promoter region of the E2F3a gene and positively regulated expression of E2F3a in mouse ES cells. Suppression of E2F3a activity by E2F6 overexpression led to the reduced proliferation in ES cells, which was relieved by co-expression of E2F3a. Furthermore, cell growth retardation caused by loss of Oct3/4 was rescued by E2F3a expression. These results suggest that Oct3/4 upregulates E2F3a expression to promote ES cell growth.

The osteoporosis susceptibility SNP rs188303909 at 2q14.2 regulates EN1 expression by modulating DNA methylation and E2F6 binding.

EN1 encodes a homeodomain-containing transcription factor and is a determinant of bone density and fracture. Previous powerful genome-wide association studies (GWASs) have identified multiple single-nucleotide polymorphisms (SNPs) near EN1 at 2q14.2 locus for osteoporosis, but the causal SNPs and functional mechanisms underlying these associations are poorly understood. The target genes regulated by the transcription factor EN1 are also unclear. In this study, we identified rs188303909, a functional CpG-SNP, as a causal SNP for osteoporosis at 2q14.2 through the integration of functional and epigenomic analyses. Functional experiments demonstrated that unmethylated rs188303909 acted as a strong allele-specific distal enhancer to regulate EN1 expression by modifying the binding of transcription factor E2F6, but rs188303909 methylation attenuated the active effect of E2F6 on EN1 expression. Importantly, transcription factor EN1 could differentially bind osteoporosis GWAS lead SNPs rs4869739-T and rs4355801-G to upregulate CCDC170 and COLEC10 expression, thus promoting bone formation. Our study provided a mechanistic insight into expression regulation of the osteoporosis susceptibility gene EN1, which could be a potential therapeutic target for osteoporosis precision medicine. KEY MESSAGES: CpG-SNP rs188303909 is a causal SNP at the osteoporosis susceptibility locus 2q14.2. Rs188303909 distally regulates EN1 expression by modulating DNA methylation and E2F6 binding. EN1 upregulates CCDC170 and COLEC10 expression through osteoporosis GWAS lead SNPs rs4869739 and rs4355801.

Relationship Between Changes in the Expression Levels of miR-134 and E2F6 in Mediating Control of Apoptosis in NMDA-Induced Glaucomatous Mice.

OBJECTIVE: This investigation was to determine the relationship between changes in the expression levels of miR-134 and the E2F transcription factor 6 (E2F6) in mediating control of apoptosis in N-methyl-D-aspartate (NMDA)-induced glaucomatous mice. METHODS: Morphological and structural changes were quantitatively analyzed along with apoptosis in the retinal ganglion cell (RGC) layer, internal plexiform layer and RGCs. Glaucomatous RGCs were transfected, and cell viability and apoptosis were examined. The targeting relationship between miR-134 and E2F6 was analyzed, as well as their expression pattern. RESULTS: Intravitreal injection of NMDA induced a significant reduction in the number of RGCs and thinning of IPL thickness. miR-134 was highly expressed and E2F6 was lowly expressed in glaucoma mice. Suppression of miR-134 or E2F6 overexpression inhibited apoptosis in the glaucomatous RGCs and instead their proliferative activity. MiR-134 targeted inhibition of E2F6 expression. Suppressing rises in E2F6 expression reduced the interfering effect of miR-134 on glaucomatous RGC development. CONCLUSION: Depleting miR134 expression increases, in turn, E2F6 expression levels and in turn reduces glaucomatous RGC apoptosis expression.

lncRNA ENST00000585827 Contributes to the Progression of Endometrial Carcinoma via Regulating miR-424/E2F6/E2F7 Axis.

Endometrial cancer (EC) ranks fourth among the most common gynecologic malignancies. Despite advances in medical technology, the pathogenesis is still unclear. Numerous reports have identified the involvement of lncRNA in the malignant progression of endometrial cancer. The aim of the study was to investigate the expression level of lncRNA ENST00000585827 (lncRNA E27) in endometrial cancer and the molecular mechanism that regulates the development of endometrial cancer. Combined with the results of the previous study, PCR analysis confirmed that lncRNA E27 was significantly upregulated in endometrial cancer cell lines. The results of CCK-8, wound healing assay, and transwell experiments showed that lncRNA E27 could significantly inhibit cell proliferation, migration, and invasion. Flow cytometry results confirmed that lncRNA E27 could promote apoptosis. Furthermore, based on bioinformatics predictions, dual-luciferase assay and RT-qPCR analysis confirmed that miR-424, as its downstream molecule, competitively regulates the expression of E2F6/E2F7. Rescue experiments further supported that lncRNA E27 inhibited proliferation, migration, invasion, and promoted apoptosis of endometrial cancer through miR-424/E2F6/E2F7 signaling axis. Conclusively, our findings revealed the role of lncRNA E27 in regulating the miR-424/E2F6/E2F7 signaling axis during EC progression, opening up new strategies for the treatment of endometrial cancer.

Combining gene expression microarray- and cluster analysis with sequence-based predictions to identify regulators of IL-13 in allergy.

The Th2 cytokine IL-13 plays a key role in allergy, by regulating IgE, airway hyper secretion, eosinophils and mast cells. In this study, we aimed to identify novel transcription factors (TFs) that potentially regulated IL-13. We analyzed Th2 polarized naïve T cells from four different blood donors with gene expression microarrays to find clusters of genes that were correlated or anti-correlated with IL13. These clusters were further filtered, by selecting genes that were functionally related. In these clusters, we identified three transcription factors (TFs) that were predicted to regulate the expression of IL13, namely CEBPB, E2F6 and AHR. siRNA mediated knockdowns of these TFs in naïve polarized T cells showed significant increases of IL13, following knockdown of CEBPB and E2F6, but not AHR. This suggested an inhibitory role of CEBPB and E2F6 in the regulation of IL13 and allergy. This was supported by analysis of E2F6, but not CEBPB, in allergen-challenged CD4+ T cells from six allergic patients and six healthy controls, which showed decreased expression of E2F6 in patients. In summary, our findings indicate an inhibitory role of E2F6 in the regulation of IL-13 and allergy. The analytical approach may be generally applicable to elucidate the complex regulatory patterns in Th2 cell polarization and allergy.

A positive feedback loop of CENPU/E2F6/E2F1 facilitates proliferation and metastasis via ubiquitination of E2F6 in hepatocellular carcinoma.

Centromere protein U (CENPU), a centromere-binding protein required for cellular mitosis, has been reported to be closely associated with carcinogenesis in multiple malignancies; however, the role of CENPU in hepatocellular carcinoma (HCC) is still unclear. Herein, we investigated its biological role and molecular mechanism in the development of HCC. High CENPU expression in HCC tissue was observed and correlated positively with a poor prognosis in HCC patients. CENPU knockdown inhibited the proliferation, metastasis, and G1/S transition of HCC cells in vivo and in vitro, while ectopic expression of CENPU exerted the opposite effects. Mechanistically, CENPU physically interacted with E2F6 and promoted its ubiquitin-mediated degradation, thus affecting the transcription level of E2F1 and further accelerating the G1/S transition to promote HCC cell proliferation. E2F1 directly binds to the CENPU promoter and increases the transcription of CENPU, thereby forming a positive regulatory loop. Collectively, our findings indicate a crucial role for CENPU in E2F1-mediated signalling for cell cycle progression and reveal a role for CENPU as a predictive biomarker and therapeutic target for HCC patients.

rtcisE2F promotes the self-renewal and metastasis of liver tumor-initiating cells via N6-methyladenosine-dependent E2F3/E2F6 mRNA stability.

Liver cancer is highly heterogeneous, and the tumor tissue harbors a variety of cell types. Liver tumor initiating cells (TICs) well contribute to tumor heterogeneity and account for tumor initiation and metastasis, but the molecular mechanisms of liver TIC self-renewal are elusive. Here, we identified a functional read-through rt-circRNA, termed rtcisE2F, that is highly expressed in liver cancer and liver TICs. rtcisE2F plays essential roles in the self-renewal and activities of liver TICs. rtcisE2F targets E2F6 and E2F3 mRNAs, attenuates mRNA turnover, and increases E2F6/E2F3 expression. Mechanistically, rtcisE2F functions as a scaffold of N-methyladenosine (m6A) reader IGF2BP2 and E2F6/E2F3 mRNA. rtcisE2F promotes the association of E2F6/E2F3 mRNAs with IGF2BP2, and inhibits their association with another m6A reader, YTHDF2. IGF2BP2 inhibits E2F6/E2F3 mRNA decay, whereas YTHDF2 promotes E2F6/E2F3 mRNA decay. By switching m6A readers, rtcisE2F enhances E2F6/E2F3 mRNA stability. E2F6 and E2F3 are both required for liver TIC self-renewal and Wnt/ß-catenin activation, and inhibition of these pathways is a potential strategy for preventing liver tumorigenesis and metastasis. In conclusion, the rtcisE2F-IGF2BP2/YTHDF2-E2F6/E2F3-Wnt/ß-catenin axis drives liver TIC self-renewal and initiates liver tumorigenesis and metastasis, and may provide a strategy to eliminate liver TICs.

E2F6 initiates stable epigenetic silencing of germline genes during embryonic development.

In mouse development, long-term silencing by CpG island DNA methylation is specifically targeted to germline genes; however, the molecular mechanisms of this specificity remain unclear. Here, we demonstrate that the transcription factor E2F6, a member of the polycomb repressive complex 1.6 (PRC1.6), is critical to target and initiate epigenetic silencing at germline genes in early embryogenesis. Genome-wide, E2F6 binds preferentially to CpG islands in embryonic cells. E2F6 cooperates with MGA to silence a subgroup of germline genes in mouse embryonic stem cells and in embryos, a function that critically depends on the E2F6 marked box domain. Inactivation of E2f6 leads to a failure to deposit CpG island DNA methylation at these genes during implantation. Furthermore, E2F6 is required to initiate epigenetic silencing in early embryonic cells but becomes dispensable for the maintenance in differentiated cells. Our findings elucidate the mechanisms of epigenetic targeting of germline genes and provide a paradigm for how transient repression signals by DNA-binding factors in early embryonic cells are translated into long-term epigenetic silencing during mouse development.

Deubiquitination of the repressor E2F6 by USP22 facilitates AKT activation and tumor growth in hepatocellular carcinoma.

Dysregulated ubiquitination of tumor-related proteins plays a critical role in tumor development and progression. The deubiquitinase USP22 is aberrantly expressed in certain types of cancer and contributes to aggressive tumor progression. However, the precise mechanism underlying the pro-tumorigenic function of USP22 in hepatocellular carcinoma (HCC) remains unclear. Here, we report that E2F6, a pocket protein-independent transcription repressor, is essential for HCC cell growth, and that its activities are controlled by USP22-mediated deubiquitination. USP22 interacts with and stabilizes E2F6, resulting in the transcriptional repression of phosphatase DUSP1. Moreover, the process involving DUSP1 repression by E2F6 strengthens AKT activation in HCC cells. Therefore, these findings provide mechanistic insights into the USP22-mediated control of oncogenic AKT signaling, emphasizing the importance of USP22-E2F6 regulation in HCC development.

Long noncoding RNA SLC9A3­AS1 increases E2F6 expression by sponging microRNA­486­5p and thus facilitates the oncogenesis of nasopharyngeal carcinoma.

Long noncoding RNA SLC9A3 antisense RNA 1 (SLC9A3­AS1) plays a central role in lung cancer; yet, its functions in nasopharyngeal carcinoma (NPC) have not been elucidated. The present study revealed the roles of SLC9A3­AS1 in NPC and dissected the mechanisms downstream of SLC9A3­AS1. SLC9A3­AS1 levels in NPC were assessed by applying RT­qPCR. The modulatory role of SLC9A3­AS1 interference on NPC cells was examined using numerous functional experiments. High expression of SLC9A3­AS1 was observed in NPC samples. Patients with NPC with a high level of SLC9A3­AS1 experienced a shorter overall survival than those with a low SLC9A3­AS1 level. Loss of SLC9A3­AS1 reduced NPC cell proliferation, colony formation, migration, and invasion but induced cell apoptosis in vitro. Animal experiments further revealed that the depletion of SLC9A3­AS1 hindered NPC tumour growth in vivo. As a competitive endogenous RNA, SLC9A3­AS1 sponged microRNA­486­5p (miR­486­5p), consequently upregulating E2F transcription factor 6 (E2F6). Finally, the effects of SLC9A3­AS1 silencing on NPC cells were reversed by inhibiting miR­486­5p or overexpressing E2F6. In summary, SLC9A3­AS1 exerted carcinogenic effects on NPC cells by adjusting the miR­486­5p/E2F6 axis. Accordingly, the newly identified SLC9A3­AS1/miR­486­5p/E2F6 pathway may offer attractive therapeutic targets for future development.

Circular RNA ZNF609 functions as a competing endogenous RNA in regulating E2F transcription factor 6 through competitively binding to microRNA-197-3p to promote the progression of cervical cancer progression.

Countless studies have demonstrated that Circular RNAs (circRNAs) exert vital effects in regulating tumorigenesis of various cancers. CircRNA ZNF609 (circ-ZNF609) has been reported as an oncogene in various human cancers. Nevertheless, its regulating effect in cervical cancer (CC) remains to be further explored. RT-qPCR was adopted to measure circ-ZNF609, miR-197-3p and E2F6 levels. CC cell proliferation, migration and invasion were analyzed via CCK-8 and transwell assays. Dual-luciferase reporter assay was adopted to confirm the interaction between miR-197-3p and circ-ZNF609 or E2F6. In the present study, it was found that circ-ZNF609 was elevated in CC tissues and cell lines, and circ-ZNF609 deletion repressed cell viability, migration and invasion in CC. Moreover, circ-ZNF609 was identified to negatively regulate miR-197-3p expression in CC cells. The inhibition of miR-197-3p abrogated the inhibitory effect on CC cell proliferation, migration and invasion induced by circ-ZNF609 knockdown. Additionally, we further demonstrated that circ-ZNF609 upregulated E2F6 by interacting with miR-197-3p. Finally, rescue assays indicated that E2F6 overexpression upended the suppression of CC progression induced by circ-ZNF609 deletion. In conclusion, circ-ZNF609 promoted CC progression through modulating the miR-197-3p/E2F6 axis as an oncogene. This finding offers a unique insight into CC molecular mechanism and suggests a potential target for CC therapy.

Repression of germline genes by PRC1.6 and SETDB1 in the early embryo precedes DNA methylation-mediated silencing.

Silencing of a subset of germline genes is dependent upon DNA methylation (DNAme) post-implantation. However, these genes are generally hypomethylated in the blastocyst, implicating alternative repressive pathways before implantation. Indeed, in embryonic stem cells (ESCs), an overlapping set of genes, including germline "genome-defence" (GGD) genes, are upregulated following deletion of the H3K9 methyltransferase SETDB1 or subunits of the non-canonical PRC1 complex PRC1.6. Here, we show that in pre-implantation embryos and naïve ESCs (nESCs), hypomethylated promoters of germline genes bound by the PRC1.6 DNA-binding subunits MGA/MAX/E2F6 are enriched for RING1B-dependent H2AK119ub1 and H3K9me3. Accordingly, repression of these genes in nESCs shows a greater dependence on PRC1.6 than DNAme. In contrast, GGD genes are hypermethylated in epiblast-like cells (EpiLCs) and their silencing is dependent upon SETDB1, PRC1.6/RING1B and DNAme, with H3K9me3 and DNAme establishment dependent upon MGA binding. Thus, GGD genes are initially repressed by PRC1.6, with DNAme subsequently engaged in post-implantation embryos.

E2F6-Mediated Downregulation of MIR22HG Facilitates the Progression of Laryngocarcinoma by Targeting the miR-5000-3p/FBXW7 Axis.

Recently, abundant evidence has clarified that long noncoding RNAs (lncRNAs) play an oncogenic or anticancer role in the tumorigenesis and development of diverse human cancers. Described as a crucial regulator in some cancers, MIR22HG has not yet been studied in laryngocarcinoma and therefore the underlying regulatory role of MIR22HG in laryngocarcinoma is worth detecting. In this study, MIR22HG expression in laryngocarcinoma cells was confirmed to be downregulated, and upregulated MIR22HG expression led to suppressive effects on laryngocarcinoma cell proliferation and migration. Molecular mechanism assays revealed that MIR22HG sponges miR-5000-3p in laryngocarcinoma cells. Besides, decreased expression of miR-5000-3p suppressed laryngocarcinoma cell proliferation and migration. Moreover, the FBXW7 gene was reported to be a downstream target gene of miR-5000-3p in laryngocarcinoma cells. More importantly, rescue assays verified that FBXW7 depletion or miR-5000-3p upregulation countervailed the repressive effects of MIR22HG overexpression on laryngocarcinoma progression. In addition, E2F6 was proved to be capable of inhibiting MIR22HG transcription in laryngocarcinoma cells. To sum up, E2F6-induced downregulation of MIR22HG promotes laryngocarcinoma progression through the miR-5000-3p/FBXW7 axis.

LncRNA GHET1 promotes cervical cancer progression through regulating AKT/mTOR and Wnt/ß-catenin signaling pathways.

Cervical cancer (CC) is a prevalent gynecological cancer, and the patients with CC usually suffer from dismal prognosis. Long non-coding RNAs (lncRNAs) are demonstrated to serve as promising biological targets in human cancers. Gastric carcinoma proliferation enhancing transcript 1 (GHET1) has been revealed to function as an oncogene in several cancers, but it has never been investigated in CC. We proposed to examine the biological role of GHET1 in CC and the underlying mechanism and validated the up-regulated expression of GHET1 in CC cell lines. Loss-of-function assays demonstrated that down-regulation of GHET1 inhibited cell growth, migration and epithelial-to-mesenchymal transition (EMT) in CC. Furthermore, we validated that GHET1 down-regulation could inactivate AKT/mTOR and Wnt/ß-catenin pathways, and that respective activation of these two pathways abrogated the inhibitive effect of GHET1 knockdown on CC cell growth, migration and EMT. Moreover, we unfolded a preliminary investigation on the modulation of GHET1 on AKT/mTOR and Wnt/ß-catenin pathways. We found that GHET1 stabilized E2F6 mRNA through interacting with IGF2BP2, so as to regulate the activity of AKT/mTOR and Wnt/ß-catenin pathways. Rescue assays also proved that GHET1 regulated these two pathways and CC cell growth, migration and EMT through E2F6. In conclusion, we revealed that down-regulation of GHET1 suppresses cervical cancer progression through regulating AKT/mTOR and Wnt/ß-catenin signaling pathways, indicating GHET1 as a promising molecular biomarker for CC treatment improvement.