The UBE2C oncogene is overexpressed in many types of solid tumours including the lethal castration-resistant prostate cancer (CRPC). The underlying mechanisms causing UBE2C gene overexpression in CRPC are not fully understood. Here, we show that CRPC-specific enhancers drive UBE2C overexpression in both AR-negative and -positive CRPC cells. We further show that co-activator MED1 recruitment to the UBE2C enhancers is required for long-range UBE2C enhancer/promoter interactions. Importantly, we find that the molecular mechanism underlying MED1-mediated chromatin looping involves PI3K/AKT phosphorylated MED1-mediated recruitment of FoxA1, RNA polymerase II and TATA binding protein and their subsequent interactions at the UBE2C locus. MED1 phosphorylation leads to UBE2C locus looping, UBE2C gene expression and cell growth. Our results not only define a causal role of a post-translational modification (phosphorylation) of a co-activator (MED1) in forming or sustaining an active chromatin structure, but also suggest that development of specific therapies for CRPC should take account of targeting phosphorylated MED1.
In prostate cancer, androgen receptor (AR) binding and androgen-responsive gene expression are defined by hormone-independent binding patterns of the pioneer factors FoxA1 and GATA2. Insufficient evidence of the mechanisms by which GATA2 contributes to this process precludes complete understanding of a key determinant of tissue-specific AR activity. Our observations suggest that GATA2 facilitates androgen-responsive gene expression by three distinct modes of action. By occupying novel binding sites within the AR gene locus, GATA2 positively regulates AR expression before and after androgen stimulation. Additionally, GATA2 engages AR target gene enhancers prior to hormone stimulation, producing an active and accessible chromatin environment via recruitment of the histone acetyltransferase p300. Finally, GATA2 functions in establishing and/or sustaining basal locus looping by recruiting the Mediator subunit MED1 in the absence of androgen. These mechanisms may contribute to the generally positive role of GATA2 in defining AR genome-wide binding patterns that determine androgen-responsive gene expression profiles. We also find that GATA2 and FoxA1 exhibit both independent and codependent co-occupancy of AR target gene enhancers. Identifying these determinants of AR transcriptional activity may provide a foundation for the development of future prostate cancer therapeutics that target pioneer factor function.
Side population (SP) cells may play an important role in tumorigenesis and cancer therapy. We isolate and identify the cancer stem-like cells in human esophageal carcinoma (EC) cell lines, EC9706 and EC109 cells labeled with Hoechst 33342. Both the cell lines contained SP cells, and the cells that had the strongest dye efflux activity ("Tip"-SP cell) in EC9706 had higher clone formation efficiency than non-SP cells. When transplanted into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, "Tip"-SP cells showed at least 50 times higher tumorigenicity than non-SP cells. Microarray analysis discriminated a differential gene expression profile between "Tip"-SP and non-SP cells, which is further tested using quantitative real-time RT-PCR. It is ascertained that several important stem cell-related genes (including OCT-4, SOX-2, BMI-1, and ZFX), two ATP-binding cassette (ABC) transporter genes (ABCG2 and ABCA5), and three Wnt and two Notch signal pathway-related genes (such as FZD10, PTGS2, KLF5, TTK, and RBM15) were upregulated in "Tip"-SP cells. Western blot showed a higher expression of beta-catenin protein in "Tip"-SP cells. All these indicated that the minority population described as "Tip"-SP cells possessed cancer stem cell character. Further understanding of tumor stem cell-specific traits will offer insights on the early stages of tumorigenesis for prevention and enhanced selectivity of antitumor therapeutics.
The ECRG4 gene was initially identified and cloned in our laboratory from human normal esophageal epithelium (GenBank accession no. AF325503). We revealed the expression of ECRG4 protein was downregulated in 68.5% (89/130) ESCC samples using tissue microarray. The low ECRG4 protein expression was significantly associated with regional lymph node metastasis, primary tumor size, and tumor stage in ESCC (p < 0.05). ECRG4 mRNA expression was downregulated in ESCC due to the hypermethylation in the gene promoter. The treatment with 5-aza-2 0 -deoxycytidine, which is a DNA methyltransferase inhibitor restored ECRG4 mRNA expression in ESCC cells. The result indicated that promoter hypermethylation may be 1 main mechanism leading to the silencing of ECRG4. The high expression of ECRG4 in patients with ESCC was associated with longer survival compared with those with low ECRG4 expression by Kaplan-Meier survival analysis (p < 0.05). ECRG4 protein was an independent prognostic factor for ESCC by multivariable Cox proportional hazards regression analysis (p < 0.05). The restoration of ECRG4 expression in ESCC cells inhibited cell proliferation, colony formation, anchorage-independent growth, cell cycle progression and tumor growth in vivo (p < 0.05). The transfection of ECRG4 gene in ESCC cells inhibited the expression of NF-jB and nuclear translocation, in addition to the expression of COX-2, a NF-jB target gene, was attenuated. Taken together, ECRG4 is a novel candidate tumor suppressor gene in ESCC, and ECRG4 protein is a candidate prognostic marker for ESCC. ' 2009 UICC
Microtubule (MT) kinesin motor proteins orchestrate various cellular processes (e.g. mitosis, motility and organelle transportation) and have been implicated in human carcinogenesis. Kif18A, a plus-end directed MT depolymerase kinesin, regulates MT dynamics, chromosome congression and cell division. In this study, we report that Kif18A is overexpressed in human breast cancers and Kif18A overexpression is associated with tumor grade, metastasis and poor survival. Functional analyses reveal that ectopic overexpression of Kif18A results in cell multinucleation, whereas ablation of Kif18A expression significantly inhibits the proliferative capability of breast cancer cells in vitro and in vivo. Inhibition of Kif18A not only affects the critical mitotic function of Kif18A but also decreases cancer cell migration by stabilizing MTs at leading edges and ultimately induces anoikis of cells with inactivation of the phosphatidylinositol 3-kinase-Akt signaling pathway. Together, our results indicate that Kif18A is involved in human breast carcinogenesis and may serve as a potential therapeutic target for human breast cancer.
The enhancer pioneer transcription factor FoxA1 is a global mediator of steroid receptor (SR) action in hormone-dependent cancers. In castration-resistant prostate cancer (CRPC), FoxA1 acts as an androgen receptor co-factor to drive G2-M phase cell-cycle transit. Here we describe a mechanistically distinct SR-independent role for FoxA1 in driving G1-S phase cell-cycle transit in CRPC. By comparing FoxA1 binding sites in prostate cancer cell genomes, we defined a co-dependent set of FoxA1-MYBL2 and FoxA1-CREB1 binding sites within the regulatory regions of the Cyclin E2 and E2F1 genes that are critical for CRPC growth. Binding at these sites upregulate the Cyclin E2 and Cyclin A2 genes in CRPC but not in earlier stage androgen-dependent prostate cancer (ADPC), establishing a stage-specific role for this pathway in CRPC growth. Mechanistic investigations indicated that FoxA1, MYBL2 or CREB1 induction of histone H3 acetylation facilitated nucleosome disruption as the basis for co-dependent transcriptional activation and G1-S phase cell-cycle transit. Our findings establish FoxA1 as a pivotal driver of the cell-cycle in CRPC which promotes G1-S phase transit as well as G2-M phase transit through two distinct mechanisms.
Background:The role of S100A14 in tumorigenesis and the underlying mechanisms have not been fully understood. Results: S100A14 affects cell invasiveness by regulating MMP2 transcription in a p53-dependent manner. Conclusion: S100A14 acts as either an inducer or an inhibitor of cell invasion depending on the p53 status of cells. Significance: These studies significantly increase our understanding of how S100A14 regulates cell invasiveness.
Background/Aims: This study aims to investigate the role of circular antisense non-coding RNA at the INK4 locus (cANRIL) in the inflammatory response of vascular endothelial cells (ECs) in a rat model of coronary atherosclerosis (AS). A rat model of AS was established with rats that were injected with a large dose of vitamin D3 and fed a high-fat diet. Methods: Sixty Wistar rats were randomly assigned into control, model, empty vector, over-expressed cANRIL and low-expressed cANRIL groups (12 rats in each group). Sixteen weeks later, the ultrastructure of their coronary arteries was observed via transmission electron microscopy. Rat serum lipid levels were analyzed using an automatic biochemical analyzer, and their atherogenic index (AI) values were calculated. Hematoxylin and eosin staining was used to observe the endothelial morphology of rats. Additionally, rat EC apoptosis was tested via a TUNEL assay. Enzyme-linked immunosorbent assays (ELISAs) were applied to measure serum levels of interleukin-1 (IL-1), IL-6, matrix metalloproteinase-9 (MMP-9) and C-reactive protein (CRP). The cANRIL, Bax, bcl-2 and caspase-3 mRNA expression levels were measured with a quantitative real-time polymerase chain reaction (qRT-PCR). The protein expression levels of Bax, bcl-2 and caspase-3 were detected using immunohistochemistry. Results: In the control group, ECs were closely arranged with normal structures, and there was no proliferation. In the model, empty vector and over-expressed cANRIL groups, some cells were not present, and atherosclerotic plaques and thrombi appeared. However, in the under-expressed cANRIL group, the cells had a normal structure. Compared with the model and empty vector groups, the levels of total cholesterol (CHOL), triglycerides (TGs), low density lipoprotein (LDL), IL-1, IL-6, MMP-9, CRP, cANRIL, Bax, and caspase-3, AI values, and rates of EC apoptosis decreased in the low-expressed cANRIL group, while HDL (high density lipoprotein) levels and mRNA and protein expression levels of bcl-2 were increased. The changes in expression levels in the over-expressed cANRIL group were the opposite of those in the low-expressed cANRIL group. Conclusions: Our study provides evidence that reduced cANRIL expression could prevent coronary AS by reducing vascular EC apoptosis and inflammatory factor expression.
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