Norcantharidin Inhibits Pre-Replicative Complexes Assembly of HepG2 Cells

Norcantharidin (NCTD) is currently used for anticancer therapy but the exact mechanism of action remains unknown. Pre-replicative complexes (pre-RCs) are essential for cell DNA replication and highly related to malignant proliferation. Here, we examined the inhibitory effect of NCTD on pre-RC components in HepG2 cells. We showed that NCTD induced degradation of Cdc6 and Mcm2 in a dose-dependent manner. Under 100 μM NCTD concentration, about 70% of Cdc6 and 50% of Mcm2 were degraded. In addition, the nuclear translocation of Mcm6 was inhibited by NCTD. Further studies aiming at G1 synchronous cells showed that, NCTD reduced the chromatin-bound Cdc6, Mcm2 and Mcm6. Moreover, the cells were blocked from entering the S phase and accumulated at the G1 phase when released synchronously into the cell cycle. Consistently, the DNA replication was inhibited by NCTD. Finally, the combination NCTD with Cdc6 depletion lead to more severe cytotoxicity (88%) than NCTD (52%) and Cdc6 depletion (39%) alone. A synergic cytotoxicity was observed between Cdc6 depletion and NCTD. In conclusion, our results demonstrate that NCTD inhibits pre-RC assembly; subsequently blocks the G1 to S transition; and inhibits DNA replication in HepG2 cells. Pre-RCs are an intriguing target for cancer therapy, which merits further investigations for anticancer development.

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Interference of the Simian Virus 40 Origin of Replication by the Cytomegalovirus Immediate Early Gene Enhancer: Evidence for Competition of Active Regulatory Chromatin Conformation in a Single Domain

Molecular and Cellular Biology ◽

10.1128/mcb.20.11.4062-4074.2000 ◽

2000 ◽

Vol 20 (11) ◽

pp. 4062-4074 ◽

Cited By ~ 6

Author(s):

Peng-Hui Chen ◽

Wen-Bin Tseng ◽

Yi Chu ◽

Ming-Ta Hsu

Keyword(s):

Dna Replication ◽

Simian Virus 40 ◽

Inhibitory Effect ◽

Simian Virus ◽

Early Gene ◽

Dependent Manner ◽

Gene Enhancer ◽

Sv40 Origin ◽

Cmv Enhancer ◽

Dose Dependent

ABSTRACT Replication origins are often found closely associated with transcription regulatory elements in both prokaryotic and eukaryotic cells. To examine the relationship between these two elements, we studied the effect of a strong promoter-enhancer on simian virus 40 (SV40) DNA replication. The human cytomegalovirus (CMV) immediate early gene enhancer-promoter was found to exert a strong inhibitory effect on SV40 origin-based plasmid replication in Cos-1 cells in a position- and dose-dependent manner. Deletion analysis indicated that the effect was exerted by sequences located in the enhancer portion of the CMV sequence, thus excluding the mechanism of origin occlusion by transcription. Insertion of extra copies of the SV40 origin only partially alleviated the inhibition. Analysis of nuclease-sensitive cleavage sites of chromatin containing the transfected plasmids indicate that the chromatin was cleaved at one of the regulatory sites in the plasmids containing more than one regulatory site, suggesting that only one nuclease-hypersensitive site existed per chromatin. A positive correlation was found between the degree of inhibition of DNA replication and the decrease of P1 cleavage frequency at the SV40 origin. The CMV enhancer was also found to exhibit an inhibitory effect on the CMV enhancer-promoter driving chloramphenicol acetyltransferase expression in a dose-dependent manner. Together these results suggest that inhibition of SV40 origin-based DNA replication by the CMV enhancer is due to intramolecular competition for the formation of active chromatin structure.

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Topotecan Induces -Apoptosis in the Myelodysplastic Syndromes Cell Line MUTZ-1 That Is Associated with down Regulation of IAP Expression.

Blood ◽

10.1182/blood.v104.11.4713.4713 ◽

2004 ◽

Vol 104 (11) ◽

pp. 4713-4713

Author(s):

Zhen Cai ◽

Wenjun Wu Master

Keyword(s):

Cell Cycle ◽

Myelodysplastic Syndromes ◽

S Phase ◽

Mrna Levels ◽

Dependent Manner ◽

Dna Ladder ◽

Down Regulation ◽

Transmission Electron ◽

Induced Apoptosis ◽

Dose Dependent

Abstract Myelodysplastic syndromes (MDS) represent a heterogenous group of clonal stem cell disorders with qualitative and quantitative abnormalities of blood cells and a high probability of evolving to acute leukemia. Intensive induction chemotherapy in order to reduce the malignant clone and reconstruct normal hematopoiesis is a classic therapy of MDS, especially high risk MDS. Topotecan (TPT), a semisynthetic water-soluble derivative of camptothecin, is a potent inhibitor of DNA topoisomerase I and has been extensively studied in hematologic malignances. However, little is known about how TPT acts against neoplastic cells. The aim of this study is to evaluate apoptotic effect of TPT on the MDS cell line MUTZ-1 and its associated changes in the expression of inhibitors of apoptosis protein (IAPs). The effect of TPT on MUTZ-1 growth was determined by using MTT assay. Characteristics associated with apoptosis induced by TPT were evaluated by transmission electron microscope, DNA gel electrophoresis and flow cytometry (FCM). Cell cycle shift were observed by FCM. Semi-quantitative RT-PCR was used to evaluate the mRNA expression of members of IAP gene family, including survivin, XIAP, Bcl-2, Bax, cIAP1 andcIAP2. The potential of mitochondrial membrane potential (MMP) was determined by using JC-1 probe. The results demonstrated that TPT significantly inhibited MUTZ-1 cell growth in a time- and dose-dependent manner with IC50 of 5.011 mmol/L, 1.297mmol/L and 0.483mmol/L at 24h, 48h and 72h respectively. Morphological features associated with TPT-induced apoptosis observed by transmission electron microscopy included cytoplasmic and nuclear shrinkage, karyorrhexis, nuclear convolution, chromatin condensation and margination, cytoplasmic vacuolization, and membrane-bound apoptotic bodies. An ambiguous DNA ladder was observed following treatment with 5mmol/L TPT for 24h, and a typical DNA ladder was observed with 10mmol/L TPT for 24h. The apoptotic rates were 11.69±0.51%, 34.07±1.73%, and 48.59±2.01%, respectively, after 24h culture with TPT as 1, 5, 10 μmol/L, significantly higher than that of the control (3.47%±0.3%; F=31.642, P<0.01). The percentage of MUTZ-1 cells in G2/M phase of the cell cycle decreased while in S and G0/G1 phase increased after treatment with 1mmol/L TPT for 24h,. The majority of the cells were arrested in S phase. After 24h culture with TPT at1, 5, and 10μmol/L, the mRNA levels of survivin, XIAP, cIAP1 and cIAP2 were decreased (P<0.01). This down-regulation was negatively correlated with TPT-induced apoptotic rates(P<0.05). There was no significant change in the Bax and Bcl-2 mRNA levels after TPT treatment (P>0.05). After 24h culture with 1μmol/L TPT, the MMP of TPT treated cells decreased significantly(P<0.01). Together, we conclude TPT can inhibit the growth and induce apoptosis of MUTZ-1 cells in a time- and dose- dependent manner. TPT can also induce the cell cycle changes, with the majoritoy of cells being arrested in S phase. The TPT-induced apoptosis in MUTZ-1 cells is associated with down-regulation of suvivin, XIAP, cIAP1and cIAP2 mRNA expresison. As well, MMP may be play a important role in the apoptotic process of MUTZ-1 cells induced by TPT.

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Valproic Acid Inihibts Histone Deacetylases and Proliferation and Induces Cell Cycle Arrest and Apoptosis in Multiple Myeloma.

Blood ◽

10.1182/blood.v106.11.5165.5165 ◽

2005 ◽

Vol 106 (11) ◽

pp. 5165-5165

Author(s):

Martin Kaiser ◽

Ulrike Heider ◽

Ivana Zavrski ◽

Jan Sterz ◽

Kurt Possinger ◽

...

Keyword(s):

Cell Cycle ◽

Multiple Myeloma ◽

Valproic Acid ◽

Cell Lines ◽

Myeloma Cell ◽

G1 Phase ◽

Dependent Manner ◽

Myeloma Cells ◽

Cycle Arrest ◽

Dose Dependent

Abstract Multiple myeloma remains an incurable disease in the majority of the patients and novel treatment strategies are urgently needed. A new class of drugs, the histone deacetylase (HDAC) inhibitors take influence in epigenetic modifications and have antiproliferative effects in some malignancies. Valproic acid (VPA) is an anticonvulsant drug and was recently shown to inhibit HDACs and suppress tumor growth. The drug is currently being evaluated in clinical studies in acute myeloid leukemia. Its effects on myeloma cells are unknown. The aim of this study was to evaluate the effects of VPA on proliferation, apoptosis and HDAC inhibition in multiple myeloma cell lines as well as in sorted human bone marrow multiple myeloma cells. Myeloma cell lines, OPM-2, NCI-H929, LP-1, and freshly isolated multiple myeloma cells from bone marrow aspirates were exposed to different concentrations of VPA for 4 to 72 hours. Cell proliferation, cell cycle distribution and apoptosis were assayed in reaction to the treatment. Proliferation decreased noticeably and apoptosis was induced in a dose-dependent manner in multiple myeloma cell lines as well as in freshly sorted primary myeloma cells. After 48 hours of incubation with VPA at 1 mM, approximately 46%, 52% and 25% of OPM-2, NCI-H929 and LP-1 cell lines had undergone specific apoptosis, respectively. Freshly sorted primary bone marrow myeloma cells from patients showed also specific apoptosis. In cell cycle analysis by flow cytometry, the population of cells in the G0/G1 phase increased, whereas cells in the S phase decreased in a time and dose dependent manner. Incubation of the cell line OPM-2, for example, with 1 mM VPA for 48 hours decreased the proportion of cells in the S phase from 39 % to 6 % of the total cell count and increased cells in the G0/G1 phase from 49 % to 85 %. Acetylation of histones and expression of cyclin D1 and the cell cycle regulators p21 and p27 were studied by western blot. Histone acetylation and p21 concentrations increased after VPA treatment whereas levels of p27 remained constant. A decrease in cyclin D1 concentrations was observed. Subapoptotic doses of VPA significantly decreased the production of VEGF in OPM-2 cell line. These data show that treatment with valproic acid effectively inhibits histone deacetylase activity, leading to the accumulation of acetylated histones in multiple myeloma cells. Parallel upregulation of cell cycle inhibitors like p21WAF1 was observed, together with a reduction of cyclin D1 levels. Myeloma cell proliferation was inhibited in a time and dose dependent manner and cell cycle arrest in the G0/G1 phase was induced by VPA treatment. VPA potently induced apoptosis in all human myeloma cell lines as well as in sorted primary multiple myeloma cells in a dose and time dependent manner. These results show for the first time that VPA acts as an HDAC inhibitor in multiple myeloma cells, induces G1 cell cycle arrest, potently inhibits tumor growth and markedly induces apoptosis. In addition to its direct antitumor effect, valproic acid may exert an antiangiogenic effect by reducing VEGF production in myeloma cells. These data provide the framework for clinical studies with valproic acid in multiple myeloma.

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Effect of Norcantharidin on N-acetyltransferase Activity in HepG2 Cells

The American Journal of Chinese Medicine ◽

10.1142/s0192415x01000186 ◽

2001 ◽

Vol 29 (01) ◽

pp. 161-172 ◽

Cited By ~ 12

Author(s):

Lii-Tzu Wu ◽

Jing-Gung Chung ◽

Jung-Chou Chen ◽

Wei Tsauer

Keyword(s):

Hepatocellular Carcinoma ◽

Hepg2 Cell ◽

Hepg2 Cells ◽

High Performance ◽

Inhibitory Effect ◽

The Other ◽

Dependent Manner ◽

Hepg2 Cell Line ◽

Aminobenzoic Acid ◽

Dose Dependent

The inhibition of arylamine N-acetyltransferase (NAT) activity by norcantharidin (NCTD), the demethylated form of cantharidin, in human hepatocellular carcinoma HepG2 cells was investigated. By using high performance liquid chromatography, NAT activity on acetylation of 2-aminofluorene (AF) and p-aminobenzoic acid (PABA) were examined. Two assay system were performed, one with cellular cytosols, the other with intact HepG2 cell suspensions. The NAT activity in HepG2 cell line was inhibited by norcantharidin in a dose-dependent manner in both types of examined systems: i.e. the greater the concentration of norcantharidin in the reaction, the greater the inhibition of NAT activities. This report is the first to show that norcantharidin has an inhibitory effect on NAT activity in HepG2 cell.

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Characterization of the S-phase-specific transcription regulatory elements in a DNA replication-independent testis-specific H2B (TH2B) histone gene.

Molecular and Cellular Biology ◽

10.1128/mcb.10.2.585 ◽

1990 ◽

Vol 10 (2) ◽

pp. 585-592 ◽

Cited By ~ 20

Author(s):

I W Hwang ◽

K Lim ◽

C B Chae

Keyword(s):

Cell Cycle ◽

Dna Replication ◽

Biological Significance ◽

Regulatory Elements ◽

S Phase ◽

Phase Cell ◽

Dependent Manner ◽

Base Pairs ◽

Pachytene Spermatocytes ◽

Cloned Gene

The testis-specific H2B histone (TH2B) gene is expressed in pachytene spermatocytes of meiotic prophase I during rat spermatogenesis. The TH2B RNA and histones are not synthesized in any other tissues, and the synthesis is independent of DNA replication. However, the cloned TH2B gene has two DNA sequence elements which stimulate transcription of the cloned gene in an S-phase-dependent manner when introduced into somatic cells. The factors interacting with the two elements, CCAAT at -127 base pairs and octamer ATTTGCAT at -93 base pairs, interact with each other to bring about a maximum stimulation of S-phase-dependent transcription. The level of CCAAT and octamer-binding proteins is unchanged during the cell cycle, and the S-phase-dependent transcription of TH2B and endogenous mouse H2B genes does not require synthesis of new proteins during the S phase. Cell cycle-specific posttranslational modification of regulatory proteins may be responsible for the S-phase-dependent transcription of H2B histone genes. The biological significance of the presence of S-phase-specific transcription regulatory elements in the DNA replication-independent and tissue-specific TH2B gene is not known.

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Modulation of Cell Cycle–specific Gene Expressions at the Onset of S Phase Arrest Contributes to the Robust DNA Replication Checkpoint Response in Fission Yeas

Molecular Biology of the Cell ◽

10.1091/mbc.e06-10-0928 ◽

2007 ◽

Vol 18 (5) ◽

pp. 1756-1767 ◽

Cited By ~ 22

Author(s):

Zhaoqing Chu ◽

Juntao Li ◽

Majid Eshaghi ◽

Xu Peng ◽

R. Krishna M. Karuturi ◽

...

Keyword(s):

Cell Cycle ◽

Dna Replication ◽

S Phase ◽

Expression Level ◽

Specific Gene ◽

Dependent Manner ◽

Replication Checkpoint ◽

Checkpoint Kinases ◽

Phase Arrest ◽

S Phase Arrest

Fission yeast replication checkpoint kinases Rad3p and Cds1p are essential for maintaining cell viability after transient treatment with hydroxyurea (HU), an agent that blocks DNA replication. Although current studies have focused on the cyclin-dependent protein kinase Cdc2p that is regulated by these checkpoint kinases, other aspects of their functions at the onset of S phase arrest have not been fully understood. In this study, we use genome-wide DNA microarray analyses to show that HU-induced change of expression profiles in synchronized G2 cells occurs specifically at the onset of S phase arrest. Induction of many core environmental stress response genes and repression of ribosomal genes happen during S phase arrest. Significantly, peak expression level of the MluI-like cell cycle box (MCB)-cluster (G1) genes is maintained at the onset of S phase arrest in a Rad3p- and Cds1p-dependent manner. Expression level maintenance of the MCB-cluster is mediated through the accumulation of Rep2p, a putative transcriptional activator of the MBF complex. Conversely, the FKH-cluster (M) genes are repressed during the onset of S phase arrest in a Rad3p-dependent manner. Repression of the FKH-cluster genes is mediated through the decreased levels of one of the putative forkhead transcription factors, Sep1p, but not Fkh2p. Together, our results demonstrate that Rad3p and Cds1p modulate transcriptional response during the onset of S phase arrest.

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FOXO1 mediates hypoxia-induced G0/G1 arrest in ovarian somatic granulosa cells via activating the TP53INP1-p53-CDKN1A pathway

Development ◽

10.1242/dev.199453 ◽

2021 ◽

Author(s):

Chengyu Li ◽

Zhaojun Liu ◽

Gang Wu ◽

Ziyu Zang ◽

Jia-Qing Zhang ◽

...

Keyword(s):

Cell Cycle ◽

Granulosa Cells ◽

Nuclear Translocation ◽

Follicular Development ◽

Inhibitory Effect ◽

G1 Phase ◽

G1 Arrest ◽

Female Reproduction

The development of ovarian follicles constitutes the foundation of female reproduction. The proliferation of granulosa cells (GCs) is a basic process required to ensure normal follicular development. However, the mechanisms involved in controlling GC cell cycle are not fully understood. Here, by performing gene expression profiling, we showed that cell cycle arrest at G0/G1 phase is highly correlated with pathways associated with hypoxic stress and FOXO signalling. Specifically, the elevated proportion of GCs at the arrested G0/G1 phase was accompanied by increased nuclear translocation of FOXO1 under conditions of hypoxia both in vivo and in vitro. Actually, phosphorylation of 14-3-3 by the JNK kinase is required for hypoxia-mediated FOXO1 activation and the resultant G0/G1 arrest. Notably, FOXO1 mutant without DNA-binding activity failed to induce G0/G1 arrest of GCs during hypoxia. Importantly, we identified a new target gene of FOXO1, namely TP53INP1, which contributed to the suppression of the G1-S cell cycle transition in response to hypoxia. Furthermore, we demonstrated that the inhibitory effect of the FOXO1-TP53INP1 axis on GC cell cycle is mediated through a p53-CDKN1A-dependent mechanism. These findings might provide avenues for the clinical treatment of human infertility caused by impaired follicular development.

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Characterization of the S-phase-specific transcription regulatory elements in a DNA replication-independent testis-specific H2B (TH2B) histone gene

Molecular and Cellular Biology ◽

10.1128/mcb.10.2.585-592.1990 ◽

1990 ◽

Vol 10 (2) ◽

pp. 585-592

Author(s):

I W Hwang ◽

K Lim ◽

C B Chae

Keyword(s):

Cell Cycle ◽

Dna Replication ◽

Biological Significance ◽

Regulatory Elements ◽

S Phase ◽

Phase Cell ◽

Dependent Manner ◽

Base Pairs ◽

Pachytene Spermatocytes ◽

Cloned Gene

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Proteosome Inhibitor Treatment Down-Regulates S-Phase Kinase-Associated Protein 2 Causing Inhibition of Proliferation and Induces Apoptosis in Primary Effusion Lymphoma.

Blood ◽

10.1182/blood.v108.11.4616.4616 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4616-4616

Author(s):

Azhar R. Hussain ◽

Naif A. Al-Jomah ◽

Mehar Sultana ◽

Manugaran S. Pulicat ◽

Khawla S. Al-Kuraya ◽

...

Keyword(s):

Cell Cycle ◽

Cell Lines ◽

Primary Effusion Lymphoma ◽

S Phase ◽

Dependent Manner ◽

Down Regulation ◽

Inhibition Of Proliferation ◽

Dose Dependent ◽

Inhibitor Treatment

Abstract Proteosome inhibition is a novel approach for treating malignancy and has been approved for clinical use. The proteosome is the primary proteolytic mechanism in eukaryotic cells and inhibition of its catalytic activity initiates a cascade of events affecting cell cycle and apoptotic activities. These activities ultimately lead to cell cycle arrest and apoptosis in malignant cells however, the normal counterpart of these cells are spared. In this study, we used a panel of primary effusion lymphoma cell lines (BC1, BC3, BCBL1 and HBL6) to study the effects of proteosome inhibitor, MG132 on cell proliferation and apoptosis. Our data showed that proteosome inhibitor MG132 decreased cell viability as well as induced apoptosis in a dose dependent manner ranging from 0.5–10μM. Furthermore, treatment with 2.5μM MG132 for 24hours induced 41% apoptosis in BC1, 51% in BC3, 41% in BCBL1 and 48% in HBL6 cell lines as detected by annexinV/PI dual staining. S-phase kinase-associated protein 2 (skp-2) is a proto-oncogene and over expressed in various types of tumors. We sought to determine the role of Skp-2 following proteosome inhibition in PELs. MG132 treatment of PEL cell lines resulted in down-regulation of SKP-2 protein in a dose dependent manner whereas the expression of p-27 was up-regulated demonstrating an inverse relationship between these two proteins. Furthermore, MG132 treatment of PELs led to conformational changes in Bax protein and translocation to the mitochondria leading to the loss of mitochondrial membrane potential with subsequent release of cytochrome c from mitochondria into cytosol. Cytochrome c release caused activation of caspase-3 followed by polyadenosin-5′-diphosphate-ribose polymerase (PARP) cleavage. In addition, proteosome inhibitor treatment also caused down-regulation of inhibitor of apoptosis protein, XIAP. Taken together, our findings show that proteosome inhibition causes down-regulation of skp-2, up-regulation of p-27, inhibition of proliferation as well as caspase-dependent apoptosis in primary effusion lymphoma cells suggesting a role of proteosome inhibitors in the treatment of these aggressive cancers.

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Efficiency and equity in origin licensing to ensure complete DNA replication

Biochemical Society Transactions ◽

10.1042/bst20210161 ◽

2021 ◽

Author(s):

Liu Mei ◽

Jeanette Gowen Cook

Keyword(s):

Cell Cycle ◽

Cell Division ◽

Dna Replication ◽

Genome Stability ◽

S Phase ◽

Replication Initiation ◽

G1 Phase ◽

Dna Replication Initiation ◽

Origin Licensing ◽

Dna Replication Origins

The cell division cycle must be strictly regulated during both development and adult maintenance, and efficient and well-controlled DNA replication is a key event in the cell cycle. DNA replication origins are prepared in G1 phase of the cell cycle in a process known as origin licensing which is essential for DNA replication initiation in the subsequent S phase. Appropriate origin licensing includes: (1) Licensing enough origins at adequate origin licensing speed to complete licensing before G1 phase ends; (2) Licensing origins such that they are well-distributed on all chromosomes. Both aspects of licensing are critical for replication efficiency and accuracy. In this minireview, we will discuss recent advances in defining how origin licensing speed and distribution are critical to ensure DNA replication completion and genome stability.

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