Up-regulation of MELK by E2F1 promotes the proliferation in cervical cancer cells

Cervical cancer is a common gynecologic cancer and a frequent cause of death. In this study, we investigated the role of MELK (maternal embryonic leucine zipper kinase) in cervical cancer. We found that HPV 18 E6/E7 promoted MELK expression by activating E2F1. MELK knockdown blocked cancer cells growth. Furthermore, we used MELK-8A to inhibit the kinase activity of MELK and caused the G2/M phase arrest of cancer cells. Under the treatment of inhibitors, Hela cells formed multipolar spindles and eventually underwent apoptosis. We also found that MELK is involved in protein translation and folding during cell division through the MELK interactome and the temporal proteomic analysis under inhibition with MELK-8A. Altogether, these results suggest that MELK may play a vital role in cancer cell proliferation and indicate a potential therapeutic target for cervical cancer.     

Rock2 promotes the invasion and metastasis of hepatocellular carcinoma by modifying MMP2 ubiquitination and degradation

Rho-associated coiled-coil-containing protein kinase 2 (Rock2) is a downstream effector of Rho that plays an important role in the tumorigenesis and progression of hepatocellular carcinoma (HCC). Matrix metalloproteinase 2 (MMP2) is a master regulator of tumor metastasis. In this study, we investigated the collections of Rock2 and MMP2 in HCCs and determined the potential role and molecular mechanism of Rock2 in MMP2-mediated invasiveness and metastasis. We found that Rock2 and MMP2 were markedly overexpressed in HCCs compared with the corresponding adjacent tissues, where a positive correlation in their expression was found. The knockdown of Rock2 significantly decreased MMP2 expression and inhibited the invasion and metastasis of HCC in vitro and in vivo. Additionally, the upregulation of MMP2 rescued the decreased migration and invasion induced by the knockdown of Rock2, whereas the knockdown of MMP2 decreased Rock2-enhanced HCC migration and invasion. Mechanistically, Rock2 stabilized MMP2 by preventing its ubiquitination and degradation. Together, our results link two drivers of invasion and metastasis in HCC and identify a novel pathway for MMP2 control.     

lncRNA NEAT1 facilitates melanoma cell proliferation,migration, and invasion via regulating miR-495-3p and E2F3

Melanoma contributes a lot to skin cancer-related deaths. lncRNAs are implicated in various diseases, including melanoma. lncRNA NEAT1 is frequently dysregulated and can play important roles in multiple cancers. Nevertheless, little has been studied about the function of NEAT1 in melanoma progression. In our present research, we displayed NEAT1 was overexpressed in melanoma cells. A series of functional assays showed that overexpression of NEAT1 promoted the proliferation, migration, and invasion of melanoma cells. By contrast, NEAT1 knockdown obviously restrained melanoma cell progression. Mechanistically, it was revealed that NEAT1 could directly bind with miR-495-3p, which led to a negative effect on miR-495-3p levels. In addition, miR-495-3p was significantly decreased in melanoma cells. Furthermore, E2F3 was postulated as the target of miR-495-3p and overexpression of this miR could suppress the levels of E2F3. Meanwhile, it was exhibited that melanoma cell proliferation, migration, and invasion induced by E2F3 silence was abrogated by miR-495-3p. Moreover, an in vivo xenograft nude mice model was established using A375 cells and it was indicated that NEAT1 promoted melanoma progression in vivo via regulating the miR-495-3p/E2F3 axis. In conclusion, we suggest that NEAT1 exerts an oncogenic effect on melanoma development via inhibition of miR-495-3p and induction of E2F3. NEAT1 might serve as a crucial prognostic biomarker of melanoma.     

E2F1-mediated MNX1-AS1-miR-218-5p-SEC61A1 feedback loop contributes to the progression of colon adenocarcinoma

The long noncoding RNA MNX1-AS1 has been reported to facilitate the progression of glioblastoma and ovarian cancer. Nevertheless, the biological roles and underlying mechanisms of MNX1-AS1 in colon adenocarcinoma have not been studied until now. In the current study, MNX1-AS1 was upregulated in colon adenocarcinoma. JASPAR prediction tool showed that E2F1 could bind to the promoter region of MNX1-AS1. The chromatin immunoprecipitation assay and luciferase reporter assay were used to verify the interactions between MNX1-AS1 and E2F1. Then functional assays revealed that downregulation of MNX1-AS1 decreased cell proliferation, migration, and invasion in colon adenocarcinoma, but upregulation of E2F1 reversed the effects. Moreover, subcellular fractionation assay manifested that MNX1-AS1 was enriched in the cytoplasm of colon adenocarcinoma cells, thus we speculated whether MNX1-AS1 could function as a competing endogenous RNA (ceRNA) to play roles in colon adenocarcinoma. Bioinformatics analysis and luciferase reporter assay indicated that MNX1-AS1 could sponge microRNA-218-5p (miR-218-5p). Furthermore, we discovered that SEC61A1 was downstream target of miR-218-5p, and MNX1-AS1 acted as a ceRNA to upregulate the expression of SEC61A1 through sponging miR-218-5p. Finally, rescue assays confirmed that MNX1-AS1 facilitated the progression of colon adenocarcinoma through regulating miR-218-5p/SEC61A1 axis. Taken together, we concluded that E2F1-mediated MNX1-AS1-miR-218-5p-SEC61A1 feedback loop contributed to the progression of colon adenocarcinoma.     

G1阻滞中p21-E2F间的相互作用

前列腺素A2(PGA2)具有强的体内、外抗增殖活性,引起细胞周期阻滞,同时,可诱导cdk抑制物p21蛋白的表达,后者亦可介导多种细胞的G1阻滞.提示p21^waf1/cip1在PGA2诱导的细胞周期阻滞中具有重要作用.主要介绍了近两年来有关p21^waf1/cip1与转录因子E2F间的相互作用的研究,阐述p21^waf1/cip1在PGA2介导的细胞周期阻滞中的作用机制.     

转录因子E2F1抑制CREG表达调控体外培养的人血管平滑肌细胞分化

为探讨转录因子E2F1在血管平滑肌细胞(vascular smooth muscle cells,VSMCs)表型转化中的作用及其对E1A激活基因阻遏子(cellular repressor of E1A-stimulated genes,CREG)表达调控的分子机制,应用生物信息学方法,定位人CREG(hCREG)基因启动子并确定转录因子E2F1在hCREG启动子区的结合位点,PCR方法克隆并构建hCREG基因启动子绿色荧光报告基因载体,以hCREG启动子区E2F1结合位点为模板,化学合成E2F1寡聚脱氧核苷酸(ODN)和错配E2F1ODN,利用转录因子"诱骗(Decoy)"策略,用E2F1ODN转染体外培养的VSMCs以阻断E2F1与hCREG基因启动子区的结合,蛋白质印迹(Western blot)分析检测阻断前后细胞内hCREG蛋白、报告基因绿色荧光蛋白(green fluorescent protein,GFP)和平滑肌细胞分化标志蛋白SMα-actin表达变化.结果显示:分化表型HITASY细胞中E2F1表达下调伴出核转位,而增殖表型的HITASY细胞中E2F1蛋白表达明显增加且定位于核内.进一步应用FuGene6瞬时转染E2F1ODN和错配E2F1ODN于体外培养HITASY细胞中,蛋白质印迹分析发现,转染E2F1ODN后,HITASY细胞中hCREG、SMα-actin和GFP表达均较未阻断组及错配组细胞明显增加.上述研究结果证实,E2F1是hCREG基因转录的重要调控因子,能够直接结合于hCREG启动子区阻遏hCREG表达,参与hCREG蛋白对VSMCs表型转化的调控作用.     

Interaction of Pin1 with Nek6 and characterization of their expression correlation in Chinese hepatocellular carcinoma patients

The peptidyl-prolyl isomerase Pin1 is prevalently overexpressed in human cancers and is regarded as a new diagnostic and therapeutic target. Pin1 interacts with several proteins involved in cell cycle events in a phosphorylation-dependent manner. Among them, NIMA (never in mitosis, gene A) was first identified to interact with Pin1. In this report, we found that Pin1 could interact with Nek6, one of the human NIMA-related kinases (Neks). This interaction was confirmed by GST pull-down assay, which was further confirmed by immunoprecipitation experiments, as well as immunofluorescence colocalization. We further studied Pin1 and Nek6 mRNA level in 40 pairs of hepatocellular carcinoma cases, finding significant correlations between Nek6 and Pin1 mRNA expression levels in these samples.