Project description:Arsenic is reportedly a biphasic inorganic compound for its toxicity and anticancer effects in humans. Recent studies have shown that certain arsenic compounds including arsenic hexoxide_x000D_ (AS4O6; hereafter, AS6) induce programmed cell death and cell cycle arrest in human cancer cells and murine cancer models. However, the mechanisms by which AS6 suppresses cancer cells are incompletely understood. In this study, we show markedly differential effects of AS6 on cytotoxicity and gene expression in human mammary epithelial normal cells (HUMEC) and Michigan Cancer Foundation 7 (MCF7), a human mammary epithelial cancer cell line. AS6 selectively arrests cell growth and induces cell death in MCF7 cells without affecting the growth of HUMEC in a dose-dependent_x000D_ manner. AS6 alters the transcription of a large number of protein-coding genes in MCF7 cells, but much fewer genes in HUMEC. Importantly, we found that the cell proliferation, cell cycle, and DNA repair pathways are significantly suppressed whereas cellular stress response and apoptotic pathways_x000D_ increase in AS6-treated MCF7 cells. Together, we provide the first evidence of differential effects of AS6 on normal and cancerous breast epithelial cells, suggesting that AS6 at moderate concentrations induces cell cycle arrest and apoptosis through modulating genome-wide gene expression, leading to compromised DNA repair and increased genome instability selectively in human breast cancer cells
Project description:Breast cancer is a worlwide health problem. One of the factors involved in carcinogenesis is diet. Several studies indicate that resveratrol, a polyphenol present in diet, has several antitumor properties. The purpose of the study is gain an insight of resveratrol effect in cancer by determining the gene expression profile of breast cancer cell lines treated with the compound. MCF7 cell lines were treated for a 48 hour period with two concentrations (150 and 250 uM) of resveratrol. 9 plates were used for each condition. The RNA obtained from 3 plates of the same condition was pooled, processed and hybridized to the Affymetrix Human Gene 1.0 ST array. The arrays were analyzed using Partek Genomics suite software-.
Project description:The proteins from the Fanconi Anemia (FA) pathway of DNA repair maintain DNA replication fork integrity by preventing the unscheduled degradation of nascent DNA at regions of stalled replication forks. Here, we ask if the bacterial pathogen H. pylori exploits the fork stabilisation machinery to generate double stand breaks (DSBs) and genomic instability. Specifically, we study if the H. pylori virulence factor CagA generates host genomic DSBs through replication fork destabilisation and collapse. An inducible gastric cancer model was used to examine global CagA-dependent transcriptomic and proteomic alterations, using RNA sequencing and SILAC-based mass spectrometry, respectively. The transcriptional alterations were confirmed in gastric cancer cell lines infected with H. pylori. Functional analysis was performed using chromatin fractionation, pulsed-field gel electrophoresis (PFGE), and single molecule DNA replication/repair fiber assays. We found a core set of 31 DNA repair factors including the FA genes FANCI, FANCD2, BRCA1, and BRCA2 that were downregulated following CagA expression. H. pylori infection of gastric cancer cell lines showed downregulation of the aforementioned FA genes in a CagA-dependent manner. Consistent with FA pathway downregulation, chromatin purification studies revealed impaired levels of Rad51 but higher recruitment of the nuclease MRE11 on the chromatin of CagA-expressing cells, suggesting impaired fork protection. In line with the above data, fibre assays revealed higher fork degradation, lower fork speed, daughter strands gap accumulation, and impaired re-start of replication forks in the presence of CagA, indicating compromised genome stability. By downregulating the expression of key DNA repair genes such as FANCI, FANCD2, BRCA1, and BRCA2, H. pylori CagA compromises host replication fork stability and induces DNA DSBs through fork collapse. These data unveil an intriguing example of a bacterial virulence factor that induces genomic instability by interfering with the host replication fork stabilisation machinery.
Project description:Intraoperative radiotherapy (IOERT) is a high radiation therapeutic technique which administers a single high dose of ionizing radiation (IR) immediately after surgical tumor removal in order to destroy the residual cancer cells in the site at high risk for recurrence. IR is able to regulate several genes and factors involved in cell-cycle progression, survival and/or cell death, DNA repair and inflammation modulating an intracellular response radiation dependent producing an imbalance in cell fate decision. In this study, we examined changes in gene expression in MCF7 breast cancer cell line exposed to 9Gy and 23Gy high single dose of IR delivered by IOERT. Changes in gene expression in MCF7 breast cancer cell line exposed to 9Gy and 23Gy high single dose of IR (named MCF7_9Gy and MCF7_23Gy respectively), were analyzed as two-color hybridizations using Agilent Technologies whole human genome 4x44K microarrays
Project description:Histone methyltransferase SETD1A is critical for acute myeloid leukemia (AML) cell survival, but the molecular mechanism driving SETD1A gene regulation remains elusive. To delineate the role of SETD1A, we utilize a protein degrader technology to induce rapid SETD1A degradation in AML cell lines. SETD1A degradation results in immediate downregulation of transcripts associated with DNA repair and heme biosynthesis pathways. CRISPR-based functional analyses and metabolomics reveal an essential role of SETD1A to maintain mitochondrial respiration in AML cells. These SETD1A targets are enriched in head-to-head (H2H) genes. SETD1A degradation disrupts a non-enzymatic SETD1A domain-dependent cyclin K function, increases the Ser5P RNA polymerase II (RNAP2) at TSS, and induces the promoter-proximal pausing of RNAP2 in a strand-specific manner. This study reveals a non-enzymatic role for SETD1A in transcriptional pause release and provides insight into the mechanism of RNAP2 pausing and its function in cancer.
Project description:Promoter methylation is able to induce downregulation of gene expression. 5-Aza-2'-deoxycytidine(Aza), methytransferase inhibitor, induce CpG demethylation. Here, 5-Aza-2'-deoxycytidine(Aza) is treated in a human breast cancer cell, MCF7, for detection of gene expression change.
Project description:Treatment of tumors with ionizing radiation for cancer therapy induces biological responses that include changes in cell cycle, activation of DNA repair mechanisms, and induction of apoptosis or senescence programs. What is not known is whether ionizing radiation induces an epigenetic DNA methylation response or whether epigenetic changes occur in genes in pathways classically associated with the radiation response. We exposed breast cancer cells to 0, 2, or 6 Gy and determined global DNA methylation at 1, 2, 4, 8, 24, 48, and 72 hours post-irradiation. We found that radiation treatment resulted in a DNA methylation response and that cell cycle, DNA repair, and apoptosis pathways were enriched in genes are were differentially-methylated. DNA methylation profiling of ionizing radiation treated cells using the Infinium HumanMethylation450 BeadChip.
Project description:Estrogen Receptor ? (ER?) has central role in hormone-dependent breast cancer and its ligand-induced functions have been extensively characterized. However, evidence exists that ER? has functions which are independent of ligands. In the present work, we investigated the binding of ER? to chromatin in absence of ligands, and its function(s) on gene regulation. We demonstrated that in MCF7 breast cancer cells unliganded ER? binds to more than four thousands chromatin sites. Unexpectedly, although almost entirely comprised in the larger group of estrogen-induced binding sites, we found that unliganded-ER? binding is specifically linked to genes with developmental functions, as compared to estrogen-induced binding. Moreover, we found that siRNA-mediated downregulation of ER? in absence of estrogen is accompanied by changes in the expression levels of hundreds of coding and noncoding RNAs. Downregulated mRNAs showed enrichment in genes related to epithelial cell growth and development. Stable ER? downregulation using shRNA, which caused cell-growth arrest, was accompanied by increased H3K27me3 at ER? binding sites. Finally, we found that FOXA1 and AP2? binding to several sites is decreased upon ER? silencing, suggesting that unliganded ER? participates, together with other factors, to the maintenance of the luminal-specific cistrome in breast cancer cells. Examination of unligandend estrogen receptor alpha (apoER?) DNA interactions in control and ER? siRNA treated MCF7 cells.
Project description:Treatment of tumors with ionizing radiation for cancer therapy induces biological responses that include changes in cell cycle, activation of DNA repair mechanisms, and induction of apoptosis or senescence programs. What is not known is whether ionizing radiation induces an epigenetic DNA methylation response or whether epigenetic changes occur in genes in pathways classically associated with the radiation response. We exposed breast cancer cells to 0, 2, or 6 Gy and determined global DNA methylation at 1, 2, 4, 8, 24, 48, and 72 hours post-irradiation. We found that radiation treatment resulted in a DNA methylation response and that cell cycle, DNA repair, and apoptosis pathways were enriched in genes are were differentially-methylated.