Hydrangea serrata extract exerts tumor inhibitory activity against hepatocellular carcinoma HepG2 cells via inducing p27/CDK2-mediated cell cycle arrest and apoptosis

Objective:To examine the inhibitory effect of Hydrangea serrata extract against hepatocellular carcinoma HepG2 cells and its underlying mechanisms.Methods:The effects of Hydrangea serrata extract on growth inhibition of tumor cells and spheroids were assessed using MTT and 3D culture assays.Quantitative real-time PCR and Western blot analyses were employed to investigate the changes in mRNA and protein expression levels of molecules related to cell cycle and apoptosis.Results:Hydrangea serrata extract effectively inhibited the growth of both tumor cells and spheroids.The extract also significantly upregulated p27 mRNA expression and downregulated CDK2 mRNA expression,leading to cell cycle arrest.Moreover,increased BAX/Bcl-2 ratio as well as caspase-9 and-3 were observed after treatment with Hydrangea serrata extract,indicating the induction of tumor cell apoptosis.Conclusions:Hydrangea serrata extract has the potential to alleviate tumors by effectively modulating cell-cycle-related gene expressions and inducing apoptosis,thereby inhibiting tumor growth.

Antitumor Effect of Apcin on Endometrial Carcinoma via p21-Mediated Cell Cycle Arrest and Apoptosis

Objective Endometrial carcinoma(EC)is a prevalent gynecological malignancy characterized by increasing incidence and mortality rates.This underscores the critical need for novel therapeutic targets.One such potential target is cell division cycle 20(CDC20),which has been implicated in oncogenesis.This study investigated the effect of the CDC20 inhibitor Apcin on EC and elucidated the underlying mechanism involved.Methods The effects of Apcin on EC cell proliferation,apoptosis,and the cell cycle were evaluated using CCK8 assays and flow cytometry.RNA sequencing(RNA-seq)was subsequently conducted to explore the underlying molecular mechanism,and Western blotting and coimmunoprecipitation were subsequently performed to validate the results.Animal studies were performed to evaluate the antitumor effects in vivo.Bioinformatics analysis was also conducted to identify CDC20 as a potential therapeutic target in EC.Results Treatment with Apcin inhibited proliferation and induced apoptosis in EC cells,resulting in cell cycle arrest.Pathways associated with apoptosis and the cell cycle were activated following treatment with Apcin.Notably,Apcin treatment led to the upregulation of the cell cycle regulator p21,which was verified to interact with CDC20 and consequently decrease the expression of downstream cyclins in EC cells.In vivo experiments confirmed that Apcin treatment significantly impeded tumor growth.Higher CDC20 expression was observed in EC tissue than in nonmalignant tissue,and increased CDC20 expression in EC patients was associated with shorter overall survival and progress free interval.Conclusion CDC20 is a novel molecular target in EC,and Apcin could be developed as a candidate antitumor drug for EC treatment.

NCAPD2 serves as a potential prognostic biomarker for lung adenocarcinoma and promotes cell proliferation,migration,invasion and cell cycle in vitro

Objectives:The pro-oncogenic effects of NCAPD2 have been extensively studied across various tumor types;however,its precise role within the context of lung adenocarcinoma(LUAD)remains elusive.This study aims to elucidate the biological functions of NCAPD2 in LUAD and unravel the underlying mechanistic pathways.Methods:Utilizing bioinformatics methodologies,we explored the differential expression of NCAPD2 between normal and tumor samples,along with its correlations with clinical-pathological characteristics,survival prognosis,and immune infiltration.Results:In the TCGA-LUAD dataset,tumor samples demonstrated significantly elevated levels of NCAPD2 expression compared to normal samples(p<0.001).Clinically,higher NCAPD2 expression was notably associated with advanced T,N,and M stages,pathologic stage,gender,smoking status,and diminished overall survival(OS).Moreover,differentially expressed genes(DEGs)associated with NCAPD2 were predominantly enriched in pathways related to cell division.Immune infiltration analysis revealed that NCAPD2 expression levels were linked to the infiltration of memory B cells,naïve CD4+T cells,activated memory CD4+T cells,and M1 macrophages.In vitro experiments demonstrated that silencing NCAPD2 suppressed LUAD cell proliferation,migration,invasion,epithelial-mesenchymal transition(EMT),and cell cycle progression.Conclusions:In summary,NCAPD2 may represent a promising prognostic biomarker and novel therapeutic target for LUAD.

Cdk5 and aberrant cell cycle activation at the core of neurodegeneration

Neurodegenerative diseases are caused by the progressive loss of specific neurons.The exact mechanisms of action of these diseases are unknown,and many studies have focused on pathways related to abnormal accumulation and processing of proteins,mitochondrial dysfunction,and oxidative stress leading to apoptotic death.However,a growing body of evidence indicates that aberrant cell cycle re-entry plays a major role in the pathogenesis of neurodegeneration.The activation of the cell cycle in mature neurons could be promoted by several signaling mechanisms,including c-Jun N-terminal kinases,p38 mitogen-activated protein kinases,and mitogen-activated protein kinase/extracellular signal-regulated kinase cascades;post-translational modifications such as Tau-phosphorylation;and DNA damage response.In all these events,implicated Cdk5,a proline-directed serine/threonine protein kinase,seems to be responsible for several cellular processes in neurons including axon growth,neurotransmission,synaptic plasticity,neuronal migration,and maintenance of neuronal survival.However,under pathological conditions,Cdk5 dysregulation may lead to cell cycle re-entry in post-mitotic neurons.Thus,Cdk5 hyperactivation,by its physiologic activator p25,hyper-phosphorylates downstream substrates related to neurodegenerative diseases.This review summarizes factors such as oxidative stress,DNA damage response,signaling pathway disturbance,and Ubiquitin proteasome malfunction contributing to cell cycle re-entry in post-mitotic neurons.It also describes how all these factors are linked to a greater or lesser extent with Cdk5.Thus,it offers a global vision of the function of cell cycle-related proteins in mature neurons with a focus on Cdk5 and how this protein contributes to the development of Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral sclerosis,and Huntington’s disease by cell cycle activation.

Wild pink bayberry free phenolic extract induces mitochondria-dependent apoptosis and G0/G1 cell cycle arrest through p38/MAPK and PI3K/Akt pathway in MDA-MB-231 cancer cells

Polyphenol-rich foods have been shown to be good for cancer prevention as powerful antioxidants. In this study, the mechanisms of wild pink bayberry free phenolic extract(WPBFE)inhibiting the proliferation and inducing apoptotic of MDA-MB-231 breast cancer cells was examined. The main phenolic acids and flavonols in WPBFE were gallic acid((18.83 ± 0.44)μg/g FW)and myricetin((1.52 ± 0.05)μg/g FW), respectively. The maximum inhibition rate of WPBFE at non-cytotoxicity dose(below 80 mg/mL)was 81%. Western blotting analysis showed that WPBFE could cause the arrest of cell cycle in G0/G1 phase by down-regulating expression levels of PCNA, CDK4, cyclin D1 and up-regulating the expression level of p21. Meanwhile, WPBFE induced apoptosis through initiating the mitochondrial death pathway by up-regulating cleaved caspase-3 and enhancing the ratio of Bax/Bcl-2, with the maximum expression levels of 1.29 and 2.03 folds that of control group, respectively. Further study of the upstream protein, we found that WPBFE down-regulated TRAF2, while upregulated p-ASK1, p-p38 and p-p53. Furthermore, WPBFE could down-regulate the expression of p-PI3K and p-Akt. These observations indicated that WPBFE might play an anticancer role through regulating the p38 MAPK together with PI3K/Akt pathway.

Combinatorial effect of diclofenac with piperine and D-limonene on inducing apoptosis and cell cycle arrest of breast cancer cells

Objective:To investigate the potential synergistic activity of diclofenac with piperine and D-limonene in inducing apoptosis and cell cycle arrest in breast cancer MCF-7 cells.Methods:Molecular docking study was conducted to evaluate the binding affinity of diclofenac with piperine and D-limonene against p53,Bax,and Bcl-2.The MTT assay was used to determine IC50,and the Chou-Talay method was used to determine the synergistic concentration of the combination treatment of diclofenac plus piperine and diclofenac plus D-limonene.Apoptosis detection,cell cycle arrest,reactive oxygen species production,and mitochondrial membrane potential were also investigated.Results:Diclofenac,piperine,and D-limonene showed potent binding affinity for p53,Bax,and Bcl-2.Diclofenac plus piperine and diclofenac plus D-limonene enhanced the formation of reactive oxygen species,which also had an effect on the mitochondrial membrane’s integrity and caused DNA fragmentation.Diclofenac plus piperine and diclofenac plus D-limonene arrested the cells in the sub-G0phase while drastically lowering the percentage of cells in the G2/M phase.Furthermore,the elevated apoptosis in the combined therapy was confirmed by annexin V/propidium iodide staining.Conclusions:The combined therapy prominently enhanced the antiproliferative and apoptotic effects on MCF-7 cells compared with treatment with diclofenac,piperine,and D-limonene alone.

Expression dynamics of periodic transcripts during cancer cell cycle progression and their correlation with anticancer drug sensitivity

Background:The cell cycle is at the center of cellular activities and is orchestrated by complex regulatory mechanisms,among which transcriptional regulation is one of the most important components.Alternative splicing dramatically expands the regulatory network by producing transcript isoforms of genes to exquisitely control the cell cycle.However,the patterns of transcript isoform expression in the cell cycle are unclear.Therapies targeting cell cycle checkpoints are commonly used as anticancer therapies,but none of them have been designed or evaluated at the alternative splicing transcript level.The utility of these transcripts as markers of cell cycle-related drug sensitivity is still unknown,and studies on the expression patterns of cell cycle-targeting drug-related transcripts are also rare.Methods:To explore alternative splicing patterns during cell cycle progression,we performed sequential transcriptomic assays following cell cycle synchronization in colon cancer HCT116 and breast cancer MDA-MB-231 cell lines,using flow cytometry and reference cell cycle transcripts to confirm the cell cycle phases of samples,and we developed a new algorithm to describe the periodic patterns of transcripts fluctuating during the cell cycle.Genomics of Drug Sensitivity in Cancer(GDSC)drug sensitivity datasets and Cancer Cell Line Encyclopedia(CCLE)transcript datasets were used to assess the correlation of genes and their transcript isoforms with drug sensitivity.We identified transcripts associated with typical drugs targeting cell cycle by determining correlation coefficients.Cytotoxicity assays were used to confirm the effect of ENST00000257904 against cyclin dependent kinase 4/6(CDK4/6)inhibitors.Finally,alternative splicing transcripts associated with mitotic(M)phase arrest were analyzed using an RNA synthesis inhibition assay and transcriptome analysis.Results:We established high-resolution transcriptome datasets of synchronized cell cycle samples from colon cancer HCT116 and breast cancer MDA-MB-231 cells.The results of the cell cycle assessment showed that 43,326,41,578 and 29,244 transcripts were found to be periodically expressed in HeLa,HCT116 and MDA-MB-231 cells,respectively,among which 1280 transcripts showed this expression pattern in all three cancer cell lines.Drug sensitivity assessments showed that a large number of these transcripts displayed a higher correlation with drug sensitivity than their corresponding genes.Cell cycle-related drug screening showed that the level of the CDK4 transcript ENST00000547281 was more significantly associated with the resistance of cells to CDK4/6 inhibitors than the level of the CDK4 reference transcript ENST00000257904.The transcriptional inhibition assay following M phase arrest further confirmed the M-phase-specific expression of the splicing transcripts.Combined with the cell cycle-related drug screening,the results also showed that a set of periodic transcripts,for example,ENST00000314392(a dolichylphosphate mannosyltransferase polypeptide 2 isoform transcript),was more associated with drug sensitivity than the levels of their corresponding gene transcripts.Conclusions:In summary,we identified a panel of cell cycle-related periodic transcripts and found that the levels of transcripts of drug target genes showed different values for predicting drug sensitivity,providing novel insights into alternative splicing-related drug development and evaluation.

Novel coumarone-derived(S,E)-4-(4-fluorobenzylidene)-3-phenylchroman-3-ol inhibits muscle-invasive bladder cancer cells by repressing the S and G2 cell cycle phases

Background:This study aimed to select compounds with unique inhibitory effects on muscle-invasive bladder cancer(MIBC)from coumarone derivatives with similar parent nuclear structures and to reveal their tumor-suppressive effects using various approaches.Methods:Bladder cancer cell lines SW780 and T24,as well as human normal bladder epithelial cell line SV-HUC-1 were selected as the study model,and these urinary system cells were co-incubated with various concentrations of(S,E)-4-(4-methylbenzylidene)-3-phenylchroman-3-ol,(S,E)-4-(4-isocyanobenzylidene)-3-phenylchroman-3-ol,(S,E)-4-(4-fluorobenzylidene)-3-phenylchroman-3-ol(FPO),and(S,E)-3-phenyl-4-(4-(trifluoromethoxy)benzylidene)chroman-3-ol.Cell activity was detected using cell counting kit-8.FPO showed the strongest inhibitory effect on MIBC cells;therefore,it was selected for further experiments.We monitored the FPO-induced T24 cell morphological changes with an inverted microscope.The FPO-inhibited migration of T24 cells was examined using a cell scratch assay.We detected the clonogenic ability of T24 cells through a clone formation test and evaluated their proliferative ability using a 5-ethynyl-2’-deoxyuridine fluorescence staining kit.The inhibitory effect of FPO against the cell cycle was monitored using flow cytometry,and its suppressive effect on the DNA replication ability of T24 cells was detected using double fluorescence staining(Ki67 and phalloidin).Results:Among the four candidate coumarone derivatives,FPO showed the most significant inhibitory effect on MIBC cells and was less toxic to normal urothelial cells.FPO inhibited T24 cell growth in time and dose-dependent manners(the half-inhibitory concentration is 8μM).FPO significantly repressed the proliferation,migration,and clonogenic ability of bladder cancer T24 cells.Cell mobility was significantly inhibited by FPO:30μM FPO almost completely repressed migration occurred at after 24 h treatment.Moreover,FPO significantly suppressed the clonogenicity of bladder cancer cells in a dose-dependent manner.Mechanistically,FPO targeted the cell cycle,arresting the S and G2 phases on bladder cancer T24 cells.Conclusion:We discovered a novel anticancer chemical,FPO,and proposed a potential mechanism,through which it suppresses MIBC T24 cells by repressing the cell cycle in the S and G2 phases.This study contributes to the development of novel anticancer drugs for MIBC.

Induction of apoptosis and G2/M cell cycle arrest by oridonin in human gastric cancer BGC-823 cells

Aim To investigate in vitro apoptosis-induction effects of oridonin on gastric tumor cells BGC-823 and its effects on cell cycle, mitochondrial membrane potential and intracellular Ca^2＋ to shed light on the mode of its anticancer action. Methods The MTT method was used to investigate the inhibitory effect of oridonin on BGC-823 cells. The apoptosis-induction effect was evaluated by confocal laser microscopy and flow cytometry. The change of mitochondrial membrane potential and the increase of intracellular Ca^2＋ were assessed by fluorescence probe rhodamine123 and Fluo 3-AM, respectively, with flow cytometry. The expression of apoptosis and cell cycle related proteins was studied using western blotting. Results Oridonin inhibited BGC-823 cells growth with IC50 of 22.21 p, mol.L^-1. It induced apoptosis in a dose-dependent manner. In addition, it decreased mitochondria membrane potential, increased intracellular Ca^2＋, and activated pro-caspase 3. BGC-823 cells were arrested in G2/M cell cycle phase with lower expression of cyclin A protein. The up-regulation of p53 was observed before apoptosis and cell cycle arrest occurred. Conclusion Oridonin inhibits the proliferation of BGC-823 cells through G2/M cell cycle arrest and apoptosis induction, which is mediated by influx of Ca^2＋, up-regulation of p53, activation of caspase-3, and down-regulation of cyclin A.

Effects of Low Dose Radiation on Tumor Apoptosis, Cell Cycle and Apoptosis-Related Protein Bcl-2 in Tumor-Bearing Mice

To study the effects of low dose radiation (LDR) on tumor apoptosis, cellcycle progression and changes of apoptosis-related protein Bcl-2 in tumor-bearing mice. Methods:Male mice of Kunming strain were implanted subcutaneously with S180 sarcoma cells in the left inguenas an in situ experimental animal model. Seven days later, the mice were subjected to 75 mGywhole-body γ-irradiation. At 24 and 48 h after the irradiation, all mice were sacrificed. The tumorsizes were measured, and tumor cell apoptosis and cell cycle progression were analyzed by flowcytometry. The expression of apoptosis-related protein Bcl-2 and the apoptotic rate of tumor cellswere observed by immunohistochemistry and electron microscopy. Results: Tumors grew significantlyslower after LDR (P 【 0.05). The tumor cells were arrested in G1 phrase and the expression of Bcl-2protein decreased at 24 h. Apoptotic rate of tumor cells was increased significantly at 48 h afterLDR (P 【 0.01). Conclusion: LDR could cause a G1-phase arrest and increase the apoptosis of tumorcells through the low level of apoptosis-related protein bcl-2 in the tumor-bearing mice. Theorganized immune function and anti-tumor ability are markedly increased after LDR. Our studyprovides practical evidence of clinical application to cancer treatment.

Cell Cycle Kinetic Analysis in the Cortical Regions of the Lentil Primary Root During Germination

Cell cycle kinetic activity in the cortical cells of the lentil (Lens culinaris Me-die. cv. Verte du Puy) primary root during germination was examined both temporally and spatially. Immunohistochemical and cytological evidence indicated that DNA replication and cell division started in the cortical cells of tire lentil primary root after around 13 and 17 h of imbibition, respectively. The first cells in DNA synthesis and the First mitotic figures all appeared in the cortical cells about I mm front the root-cap junction, but these divided cells had synthesized their DNA during the maturity of seed instead of during germination. The kinetic pattern of activity of the first cell cycle showed that these cells were not activated synchronously, but re-entered the cell cycle in turn depending on their places in the root tip, However, the adjacent cells partially synchronously proceeded their cell cycle.

Multiple Defects of Cell Cycle Checkpoints in U937-ASPI3K, an U937 Cell Mutant Stably Expressing Anti-Sense ATM Gene cDNA

(Ataxia-telangiectasia mutated gene (ATM) functions in control of cell cycle checkpoints in responding to DNA damage and protects cells from undergoing apoptosis. Knock-out within tumor cells of endogenous ATM will achieve therapeutic benefits and enable a better understanding of the decisive mechanisms of cell death or survival in response to DNA damaging agents. ) In present paper, we sought to characterize the cell cycle checkpoint profiles in U937-ASPI3K, a U937 cell mutant that was previously established with endogenous ATM knock-out phenotype. Syn- chronized U937-ASPI3K was exposed to 137Cs irradiation, G1, S. G2/M cell cycle checkpoint pro- files were evaluated by determining cell cycle kinetics, p53/p21 protein, cyclin dependent kinase 2 (CDK2) and p34CDC2 kinase activity in response to irradiation. U937-ASPI3K exhibited multiple defects in cell cycle checkpoints as defined by failing to arrest cells upon irradiation. The accumulation of cellular p53/p21 protein and inhibition of CDK kinase was also abolished in U937-ASPI3K. It was concluded that the stable expression of anti-sense PI3K cDNA fragment completely abolished multiple cell cycle checkpoints in U937-ASPI3K, and hence U937-ASPI3K with an AT-like phenotype could serves as a valuable model system for investigating the signal transduction pathway in responding to DNA damaging-based cancer therapy.

A Novel Three-parameter Flow Cytometric Analysis for Cell Cycle

To set up a three-parameter method for cell cycle analysis by two-laser flowcy-tometer, which can detect two types of cyclin plus DNA content in one measurement, and thatanalyze unscheduled expression of cyclins. Methods: Three-color fluorescence was used for analysisof two types of cyclins and DNA content simultaneously in individual cells by two-laser flowcytometry. MOLT-4 cells were used to study the expression of major cyclins in mammalian cells. ATriton-X100 permeabilization procedure was optimized for detection of two types of cyclins. Onecyclin was stained directly with a FITC-conjugated monoclonal antibody (mAb), and the other,indirectly with RPE-Cy5-conjugated secondary antibody, while DNA was stained with the fluorochromeDAPI. mAMSA and mimosine treated MOLT-4 cells were used to test this three-parameter method.Results: Permeabilization with 0.5% Triton-XlOO in PBS containing 1% BSA for 5 min on ice providedoptimal conditions for the simultaneous labelling of two cyclins plus DNA in single cells. It wasfound that the emission spectrum of the three dyes (DAPI, FITC and RPE-Cy5) could be measured withno compensation. Based on cyclinA/cyclinE/DNA flow cytometric analysis, asynchronously growingMOLT-4 cells could be divided into 6 compartments (G1o, G1e, G1l, S, G2, and M) simultaneously,allowing for analysis of cell cycle phase specific perturbations without the necessity of cellsynchronization. Unscheduled cyclin B1 expression was observed in G1 cells treated with mimosine andcyclin E in G2 cells treated with mAMSA. We found that unscheduled cyclin expression paralleledexpected cyclin expression. Conclusion: Thus, three-color FCM analysis of cells may not only beapplied to measure unscheduled vs. expected cyclin expression but may also be used to estimate thefraction of cycling cells in up to 6 cell populations.

Berberine induces cell cycle arrest and apoptosis in human gastric carcinoma SNU-5 cell line

AIM： To investigate the relationship between the inhibited growth （cytotoxic activity） of berberine and apoptotic pathway with its molecular mechanism of action. METHODS： The in vitro cytotoxic techniques were complemented by cell cycle analysis and determination of sub-G1 for apoptosis in human gastric carcinoma SNU-5 cells. Percentage of viable cells, cell cycle, and sub431 group （apoptosis） were examined and determined by the flow cytometric methods. The associated proteins for cell cycle arrest and apoptosis were examined by Western blotting. RESULTS： For SNU-5 cell line, the IC （50） was found to be 48 μmol/L of berberine. In SNU-5 cells treated with 25-200 μmol/L berberine, G2/M cell cycle arrest was observed which was associated with a marked increment of the expression of p53, Wee1 and CDk1 proteins and decreased cyclin B. A concentration-dependent decrease of cells in G0/G1 phase and an increase in G2/M phase were detected. In addition, apoptosis detected as sub-Go cell population in cell cycle measurement was proved in 25-200 μmol/L berberine-treated cells by monitoring the apoptotic pathway. Apoptosis was identified by sub-Go cell population, and upregulation of Bax, downregulation of Bcl-2, release of Ca^2＋, decreased the mitochondrial membrane potential and then led to the release of mitochondrial cytochrome C into the cytoplasm and caused the activation of caspase-3, and finally led to the occurrence of apoptosis. CONCLUSION： Berberine induces p53 expression and leads to the decrease of the mitochondrial membrane potential, Cytochrome C release and activation of caspase-3 for the induction of apoptosis.

Regulation of the cell cycle gene, BTG2, by miR-21 in human laryngeal carcinoma

MicroRNAs are short regulatory RNAs that negatively modulate gene expression at the post-transcriptional level, and are deeply involved in the pathogenesis of several types of cancers. To investigate whether specific miRNAs and their target genes participate in the molecular pathogenesis of laryngeal carcinoma, oligonucleotide microarrays were used to assess the differential expression profiles of microRNAs and mRNAs in laryngeal carcinoma tissues compared with normal tissues. The oncogeuic miRNA, microRNA-21 （miR-21）, was found to he npregulated in laryngeal carcinoma tissues. Knockdown of miR-21 by specific antisense oligonucleotides inhibited the proliferation potential of HEp-2 cells, whereas overexpression of miR-21 elevated growth activity of the cells, as detected by the colony formation assay. The cell number reduction caused by miR-21 inhibition was due to the loss of control of the G1-S phase transition, instead of a noticeable increase in apoptosis. Subsequently, a new target gene of miR- 21, BTG2, was found to be downregulated in laryngeal carcinoma tissues. BTG2 is known to act as a pan-cell cycle regulator and tumor suppressor. These findings indicate that aberrant expression of miR-21 may contribute to the malignant phenotype of laryngeal carcinoma by maintaining a low level of BTG2. The identification of the oneogenic miR-21 and its target gene, BTG2, in laryngeal carcinoma is potentially valuable for cancer diagnosis and therapy.

Epigenetic modification regulates both expression of tumor-associated genes and cell cycle progressing in human colon cancer cell lines: Colo-320 and SW1116

The aim of this study is to assess the effects of DNA methylation and historic acetylation, alone or in combination, on the expression of several tumor-associated genes and cell cycle progression in two established human colon cancer cell lines: Colo-320 and SW1116. Treatments with 5-aza-2'-deoxycytidine (5-aza-dC) and trichostatin A, alone or in combination, were applied respectively. The methylation status of the CDKN2A promoter was determined by methyla-tion-specific PCR, and the acetylated status of the histones associated with the p21WAF1 and CDKN2A genes was examined by chromatin immunoprecipitation. The expression of the CDKN2A, p21WAF1, p53, p73, APC, c-myc, c-Ki-ras and survivin genes was detected by real-time RT-PCR and RT-PCR. The cell cycle profile was established by flow cytometry. We found that along with the demethylation of the CDKN2A gene promoter in both cell lines induced by 5-aza-dC alone or in combination with TSA, the expression of both CDKN2A and APC genes increased. The treatment of TSA or sodium butyrate up-regulated the transcription of p21WAF1 significantly by inducing the acetylation of histones H4 and H3, but failed to alter the acetylation level of CDKN2A-associated histones. No changes in transcription of p53, p73, c-myc, c-Ki-ras and survivin genes were observed. In addition, TSA or sodium butyrate was shown to arrest cells at the G1 phase. However, 5-aza-dC was not able to affect the cell cycle progression. In conclusion, regulation by epigenetic modification of the transcription of tumor-associated genes and the cell cycle progression in both human colon cancer cell lines Colo-320 and SW1116 is gene-specific.

Cell cycle arrest and apoptotic cell death in cultured human gastric carcinoma cells mediated by arsenic trioxide

AIM: To investigate the effect of arsenic trioxide on human gastric cancer cell line MKN45 with respect to both cytotoxicity and induction of apoptosis in vitro. METHODS: MKN45 cells were treated with arsenic trioxide (As2O3) at the concentration of 1, 5, and 10 μmol/L, respectively, for three successive days. Cell growth and proliferation were observed by cell counting and trypan blue exclusion. Cytotoxicity of As2O3 was determined by MTT assay. Morphologic changes were studied with light microscopy. Flow cytometry was used to assay cell DNA distribution and apoptotic cells were confirmed with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and DNA electrophoresis. RESULTS: The growth of MKN45 cells was significantly inhibited by As2O3 which was confirmed by colony-forming assay. After 7 d of culture with various concentrations of As2O3, colony-forming capacity of MKN45 cells decreased with As2O3 increment in comparison with that of control group. The inhibitory rate of colony-formation was 38.5%, 99.1%, and 99.5% when the concentration of As2O3 was 1, 5, and 10 μmol/L in culture medium, respectively. The cell number of a single colony in drug treatment groups was less than that of control group. The cell-killing rate of As2O3 to MKN45 cells was both dose- and time-dependent with an IC50 of (11.05±0.25) μmol/L After incubation in 10 μmol/L As2O3 for 24 h, the cell-killing rate was 27.1%, and it was close to 50% after 48 h. The results showed that As2O3 induced time- and dose-dependent apoptosis in MKN45 cells, blocked at G2/M phase. The apoptotic peak (sub-G1 phase) appeared and cell apoptotic rate in MKN45 cells was 18.3-32.5% after treatment by 10 umol/L As2O3 for 48 h. The percentage of G2/M cell of the experimental groups was 2.0-5.0 times than that of the control group. Gel electrophoresis of DNA from cells treated with each concentration of As2O3 for 48 h revealed a 'ladder' pattern, indicating preferential DNA degradation at the internucleosomal, linker DNA sections. TUNEL also demonstrated strand breaks in DNA of MKN45 cells treated with As2O3, while control cells showed negative labeling. CONCLUSION: As2O3 can induce apoptosis of human gastric carcinoma cells MKN45, which is the basis of its effectiveness. It shows great potential in the treatment of gastric carcinoma.

Differential regulation of survivin by p53 contributes to cell cycle dependent apoptosis

Recent studies indicate that cell-cycle checkpoints are tightly correlated with the regulation of apoptosis, in which p53 plays an important role. Our present works show that the expression of E6/E7 oncogenes of human papillomavirus in HeLa cells is inhibited in the presence of anti-tumor reagent tripchlorolide (TC), which results in the up-regulation of p53 in HeLa cells. Interestingly, under the same TC-treatment, the cells at the early S-phase are more susceptible to apoptosis than those at the middle S-phase although p53 protein is stabilized to the same level in both situations. Significant difference is exhibited between the two specified expression profiles. Further analysis demonstrates that anti-apoptotic gene survivin is up-regulated by p53 in the TC-treated middle-S cells, whereas it is down-regulated by p53 in the TC-treated early-S cells. Taken together, the present study indicates that the differential p53-regulated expres- sion of survivin at different stages of the cell cycle results in different cellular outputs under the same apoptosis-inducer.

Overexpression of p27^(KIP1)induced cell cycle arrest in G_1 phase and subsequent apoptosis in HCC-9204 cell line

AIM We have previously reported that inducible over-expresaion of Bak may prolong cell cycle in G1 phase and lead to apoptosis in HCC-9204 cells. This study is to investigate whether p27KIP1 plays an important role in this process. MEHODS In order to elucidate the exact function of p27KIP1 in this process, a zinc inducible p27KIP1 stable transfectant and transient p27KIP1- GFP fusion transfectant were constructed. The effects of inducible p27KIP1 on cell growth, cell cycle arrest and apoptosis were examined in the mock, control pMD vector, and pMD-KIP1 transfected HCC-9204 cells. RESULTS This p27KIP1-GFP transfectant may transiently express the fusion gene. The cell growth was reduced by 35% at 48 h of p27KIP1 induction with zinc treatment as determined by trypan blue exclusion assay. These differences remained the same after 72 h of p27KIP1 expression, p27KIP1 caused cell cycle arrest after 24 h of induction, with 40% increase in G1 population. Prolonged p27KIP1 expression in this cell line induced apoptotic cell death reflected by TUNEL assay. Fourty-eight h and 72 h of p27KIP1 expression showed a characteristic DNA ladder on agarose gel electrophoresis.

Amygdalin inhibits genes related to cell cycle in SNU-C4 human colon cancer cells

AIM： The genes were divided into seven categories according to biological function; apoptosis-related, immune response-related, signal transduction-related, cell cyclerelated, cell growth-related, stress response-related and transcription-related genes. METHODS： We compared the gene expression profiles of SNU-C4 cells between amygdalin-treated （5 mg/mL, 24 h） and non-treated groups using cDNA microarray analysis. We selected genes downregulated in cDNA microarray and investigated mRNA levels of the genes by RT- PC R. RESULTS： Microarray showed that amygdalin downregulated especially genes belonging to cell cycle category： exonuclease 1 （EXO1）, ATP-binding cassette, sub-family F, member 2 （ABCF2）, MRE11 meiotic recombination 11 homolog A （MRE11A）, topoisomerase （DNA） Ⅰ （TOP1）, and FK506 binding protein 12-rapamycin-associated protein 1 （FRAP1）. RT-PCR analysis revealed that mRNA levels of these genes were also decreased by amygdalin treatment in SNU-C4 human colon cancer cells. CONCLUSION： These results suggest that amygdalin have an anticancer effect via downregulation of cell cycle-related genes in SNU-C4 human colon cancer cells, and might be used for therapeutic anticancer drug.