Epigenetic events during the process of cell transformation induced by carcinogens (review)

Rose (Rosa gallica) Petal Extract Suppress Proliferation, Migration, and Invasion of Human Lung Adenocarcinoma A549 Cells through via the EGFR Signaling Pathway

We sought to investigate the effect of rose petal extract (RPE) on the proliferation, migration, and invasion of cancer cells. RPE significantly inhibited the growth of lung and colorectal cancer cell lines, with rapid suppression of A549 lung cancer cells at low concentrations. These effects occurred concomitantly with downregulation of the cell proliferation mediators PCNA, cyclin D1, and c-myc. In addition, RPE suppressed the migration and invasion of A549 cells by inhibiting the expression and activity of matrix metalloproteinase-2 and matrix metalloproteinase-9 (MMP-2 and -9). We hypothesize that the suppressive activity of RPE against lung cancer cell proliferation and early metastasis occurs via the EGFR-MAPK and mTOR-Akt signaling pathways. These early results highlight the significant potency of RPE, particularly for lung cancer cells, and warrant further investigation.

Physical modeling of the heritability and maintenance of epigenetic modifications

We develop a predictive theoretical model of the physical mechanisms that govern the heritability and maintenance of epigenetic modifications. This model focuses on a particular modification, methylation of lysine-9 of histone H3 (H3K9), which is one of the most representative and critical epigenetic marks that affects chromatin organization and gene expression. Our model combines the effect of segregation and compaction on chromosomal organization with the effect of the interaction between proteins that compact the chromatin (heterochromatin protein 1) and the methyltransferases that affect methyl spreading. Our chromatin model demonstrates that a block of H3K9 methylations in the epigenetic sequence determines the compaction state at any particular location in the chromatin. Using our predictive model for chromatin compaction, we develop a methylation model to address the reestablishment of the methylation sequence following DNA replication. Our model reliably maintains methylation over generations, thereby establishing the robustness of the epigenetic code.

MicroRNA-582-3p negatively regulates cell proliferation and cell cycle progression in acute myeloid leukemia by targeting cyclin B2

Background

MicroRNAs (miRNAs) function as post-transcriptional gene expression regulators. Some miRNAs, including the recently discovered miR-582–3p, have been implicated in leukemogenesis. This study aimed to reveal the biological function of miR-582–3p in acute myeloid leukemia (AML), which is one of the most frequently diagnosed hematological malignancies.

Methods

The expression of miR-582–3p was determined using quantitative real-time PCR in blood samples from leukemia patients and in cell lines. Cell proliferation and cell cycle distribution were analyzed using the CCK-8, colony formation and flow cytometry assays. The target gene of miR-582–3p was verified using a dual-luciferase reporter assay. The G2/M phase arrest-related molecule contents were measured using western blotting analysis.

Results

We found miR-582–3p was significantly downregulated in the blood samples from leukemia patients and in the cell lines. MiR-582–3p overexpression significantly impaired cell proliferation and induced G2/M cell cycle arrest in THP-1 cells. Furthermore, cyclin B2 (CCNB2) was confirmed as a target gene of miR-582–3p and found to be negatively regulated by miR-582–3p overexpression. More importantly, CCNB2 knockdown showed suppressive effects on cell proliferation and cell cycle progression similar to those caused by miR-582–3p overexpression. The inhibitory effects of miR-582–3p overexpression on cell proliferation and cell cycle progression were abrogated by CCNB2 transfection.

Conclusion

These findings indicate new functions and mechanisms for miR-582–3p in AML development. Further study could clarify if miR-582–3p and CCNB2 are potential therapeutic targets for the treatment of AML.

CEP55 promotes cell proliferation and inhibits apoptosis via the PI3K/Akt/p21 signaling pathway in human glioma U251 cells

Human glioma is one of the major malignancies worldwide with an increased mortality rate. Centrosomal protein of 55 kDa (CEP55) is an essential component of the CEP family and has been identified as a prognostic marker for multiple types of cancer. However, the function of CEP55 during glioma tumorigenesis remains unclear. In the present study, the data derived from the Oncomine database indicated that the expression of CEP55 is increased in glioma tissues compared with normal tissues. Furthermore, the expression of CEP55 was also increased at the level of mRNA and protein in glioma cell lines compared with normal human astrocytes. The knockdown of CEP55 expression inhibited the proliferation of glioma U251 cells, whereas overexpression of CEP55 induced the proliferation of U251 cells. Flow cytometric analysis indicated that the knockdown of CEP55 resulted in an increased number of cells arrested at G₂/M phase, and apoptosis was promoted. Further investigations revealed that the overexpression of CEP55 increased the phosphorylation of Akt and inhibited the activity of p21. By contrast, the knockdown of CEP55 resulted in the opposite effects. Taken together, the results of the present study suggested that CEP55 regulated the proliferation of glioma cells, further attributing to the carcinogenesis and progression of glioma via the PI3K/Akt/p21 signaling pathway. Therefore, CEP55 may be a novel therapeutic target for the treatment of glioma.

Jianpi Huayu Decoction Inhibits Proliferation in Human Colorectal Cancer Cells (SW480) by Inducing G0/G1-Phase Cell Cycle Arrest and Apoptosis

Jianpi Huayu Decoction (JHD), a Chinese medicine formula, is a typical prescription against multiple tumors in the clinical treatment, which can raise quality of life and decrease complications. The aim of this study is to assess the efficacy of JHD against human colorectal carcinoma cells (SW480) and explore its mechanism. MTT assay showed that JHD decreased the cellular viability of SW480 cells in dose-dependent and time-dependent manner. Flow cytometry analysis revealed that JHD induced G0/G1-phase cell cycle arrest in SW480 cells and had a strong apoptosis-inducing effect on SW480 cells. Meanwhile it enhanced the expression of p27, cleaved PARP, cleaved caspase-3, and Bax and decreased the levels of PARP, caspase-3, Bcl-2, CDK2, CDK4, CDK6, cyclin D1, cyclin D2, cyclin D3, and cyclin E1, which was evidenced by RT-qPCR and Western blot analysis. In conclusion, these results indicated that JHD inhibited proliferation in SW480 cells by inducing G0/G1-phase cell cycle arrest and apoptosis, providing a practicaltherapeutic strategy against colorectal cancer.

Curcumin suppresses proliferation of colon cancer cells by targeting CDK2

Curcumin, the yellow pigment of turmeric found in Southeast Indian food, is one of the most popular phytochemicals for cancer prevention. Numerous reports have demonstrated modulation of multiple cellular signaling pathways by curcumin and its molecular targets in various cancer cell lines. To identify a new molecular target of curcumin, we used shape screening and reverse docking to screen the Protein Data Bank against curcumin. Cyclin-dependent kinase 2 (CDK2), a major cell-cycle protein, was identified as a potential molecular target of curcumin. Indeed, in vitro and ex vivo kinase assay data revealed a dramatic suppressive effect of curcumin on CDK2 kinase activity. Furthermore, curcumin induced G1 cell-cycle arrest, which is regulated by CDK2 in HCT116 cells. Although the expression levels of CDK2 and its regulatory subunit, cyclin E, were not changed, the phosphorylation of retinoblastoma (Rb), a well-known CDK2 substrate, was reduced by curcumin. Because curcumin induced cell-cycle arrest, we investigated the antiproliferative effect of curcumin on HCT116 colon cancer cells. In this experiment, curcumin suppressed HCT116 cell proliferation effectively. To determine whether CDK2 is a direct target of curcumin, CDK2 expression was knocked down in HCT116 cells. As expected, HCT116 sh-CDK2 cells exhibited G1 arrest and reduced proliferation. Because of the low levels of CDK2 in HCT116 sh-CDK2 cells, the effects of curcumin on G1 arrest and cell proliferation were not substantially relative to HCT116 sh-control cells. From these results, we identified CDK2 as a direct target of curcumin in colon cancer cells.

Isoangustone A, a novel licorice compound, inhibits cell proliferation by targeting PI3K, MKK4, and MKK7 in human melanoma

Licorice root is known to possess various bioactivities, including anti-inflammatory and anticancer effects. Glycyrrhizin, a triterpene compound, is the most abundant constituent of dried licorice root. However, high intake or long-term consumption of glycyrrhizin causes several side effects, such as hypertension, hypertensive encephalopathy, and hypokalemia. Therefore, finding additional active compounds other than glycyrrhizin in licorice that exhibit anticancer effects is worthwhile. We found that isoangustone A (IAA), a novel flavonoid from licorice root, suppressed proliferation of human melanoma cells. IAA significantly blocked cell-cycle progression at the G1-phase and inhibited the expression of G1-phase regulatory proteins, including cyclins D1 and E in the SK-MEL-28 human melanoma cell line. IAA suppressed the phosphorylation of Akt, GSK-3β, and JNK1/2. IAA also bound to phosphoinositide 3-kinase (PI3K), MKK4, and MKK7, strongly inhibiting their kinase activities in an ATP-competitive manner. Moreover, in a xenograft mouse model, IAA significantly decreased tumor growth, volume, and weight of SK-MEL-28 xenografts. Collectively, these results suggest that PI3K, MKK4, and MKK7 are the primary molecular targets of IAA in the suppression of cell proliferation. This insight into the biologic actions of IAA provides a molecular basis for the potential development of a new chemotherapeutic agent.

Biomarkers and the genetics of early neoplastic lesions

It has become increasingly evident that the study of DNA is inadequate to explain many, if not most, aspects of the development and progression of neoplastic lesions from pre-invasive lesions to metastasis. Thus, the term "genetic" can no longer refer to just the study of the genome. Much of the action in genetic research now shifts to the methods by which the pre-mRNA from one gene is processed to yield multiple different proteins, different quantities of the same protein as well as other forms of regulating RNA. Thus, the age of post-transcriptional processing and epigenetic control of the transfer of information from the genome has arrived. The mechanisms of post-transcriptional processing and epigenetic control that must be characterized in greater detail including alternate splicing, regulation of mRNA degradation, RNA regulatory factors including those factors which extensively edit mRNAs, control of translation, and control of protein stability and degradation. This chapter reviews many of the processes that control information from the genome to proteins and how these factors lead from less than 40,000 genes to more than an order of magnitude increase more proteins which actually control the phenotypes of cells - normal or neoplastic. It is usually the products of genes (e.g., mRNA, microRNA and proteins) that are the molecular markers that will control translational research and ultimately, individualized (personal) medical approaches to disease. This chapter emphasizes how the process of neoplasia "hijacks" the normal processes of cellular operations, especially those processes that are important in the normal development of the organisms - including proliferation, cellular death, angiogenesis, cellular mobility and invasion, and immunoregulation to ensure neoplastic development, survival and progression. This chapter reviews the wide range of processes controlling the information that flows from the genome to proteins and emphasizes how molecular steps in pure processes can be used as biomarkers to study prevention, treatment and/or management of diseases.

6,7,4'-trihydroxyisoflavone inhibits HCT-116 human colon cancer cell proliferation by targeting CDK1 and CDK2

Colon cancer is a common epithelial malignancies worldwide. Epidemiologic evidence has shown that nutrition and dietary components are important environmental factors involved in the development of this disease. We investigated the biological activity of 6,7,4'-trihydroxyisoflavone (6,7,4'-THIF, a metabolite of daidzein) in in vitro and in vivo models of human colon cancer. 6,7,4'-THIF suppressed anchorage-dependent and -independent growth of HCT-116 and DLD1 human colon cancer cells more effectively than daidzein. In addition, 6,7,4'-THIF induced cell cycle arrest at the S and G2/M phases in HCT-116 human colon cancer cells. Western blot analysis revealed that 6,7,4'-THIF effectively suppressed the expression of cyclin-dependent kinase (CDK) 2, but had no effect on other S- or G2/M-phase regulatory proteins such as cyclin A, cyclin B1 or CDK1. Daidzein did not affect the expression of any of these proteins. In kinase and pull-down assays, 6,7,4'-THIF, but not daidzein, inhibited CDK1 and CDK2 activities in HCT-116 cells by directly interacting with CDK1 and CDK2. In a xenograft mouse model, 6,7,4'-THIF significantly decreased tumor growth, volume and weight of HCT-116 xenografts. 6,7,4'-THIF bound directly to CDK1 and CDK2 in vivo, resulting in the suppression of CDK1 and CDK2 activity in tumors corresponding with our in vitro results. Collectively, these results suggest that CDK1 and CDK2 are potential molecular targets of 6,7,4'-THIF to suppress HCT-116 cell proliferation in vitro and in vivo. These findings provide insight into the biological actions of 6,7,4'-THIF and might establish a molecular basis for the development of new cancer therapeutic agents.

Microdamage and apoptosis

Microdamage of healthy bone leads to targeted removal and repair of the damage. This process must involve the production of specific targeting signals. The identity of these signals is unknown but constitutes a legitimate research goal since it is this targeting process which appears to become impaired in ageing and disease. Here we discuss the potential role of the matrix bound osteocyte in the sensing and targeting of microdamage. In particular we will review current understanding concerning the apoptotic death of osteocytes at sites of microdamage and discuss the potential physiological significance of these findings in the light of knowledge of the significance of apoptosis in other cell systems.

Trans, Trans-2,4-Decadienal, a Product Found in Cooking Oil Fumes, Induces Cell Proliferation and Cytokine Production Due to Reactive Oxygen Species in Human Bronchial Epithelial Cells

Dienaldehydes are by-products of peroxidation of polyunsaturated lipids and commonly found in many foods or food-products. Both National Cancer Institute (NCI) and NTP have expressed great concern on the potential genotoxicity and carcinogenicity of dienaldehydes. Trans, trans-2,4-decadienal (tt-DDE or 2,4-De), a specific type of dienaldehyde, is abundant in heated oils and has been associated with lung adenocarcinoma development in women due to their exposure to oil fumes during cooking. Cultured human bronchial epithelial cells (BEAS-2B cells) were exposed to 0.1 or 1.0 microM tt-DDE for 45 days, and oxidative stress, reactive oxygen species (ROS) production, GSH/GSSG ratio, cell proliferation, and expression of TNFalpha and IL-1beta were measured. The results show that tt-DDE induced oxidative stress, an increase in ROS production, and a decrease in GSH/GSSG ratio (glutathione status) in a dose-dependent manner. Treatment of BEAS-2B cells with 1.0 microM tt-DDE for 45 days increased cell proliferation and the expression and release of pro-inflammatory cytokines TNFalpha and IL-1beta. Cotreatment of BEAS-2B cells with antioxidant N-acetylcysteine prevented tt-DDE-induced cell proliferation and release of cytokines. Therefore, these results suggest that tt-DDE-induced changes may be due to increased ROS production and enhanced oxidative stress. Since increased cell proliferation and the release of TNF-alpha and IL-1beta are believed to be involved in tumor promotion, our results suggest that tt-DDE may play a role in cancer promotion. Previous studies on dienaldehydes have focused on their genotoxic or carcinogenic effects in the gastrointestinal tract; the present study suggests a potential new role of tt-DDE as a tumor promoter in human lung epithelial cells.