• BMB Reports
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• v.50 no.7
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• pp.379-383
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• 2017

We previously reported that p53 plays a role as a key regulator in the tetraploid G1 checkpoint, which is activated by actin damage-induced cytokinesis blockade and then prevents uncoupled DNA replication and nuclear division without cytokinesis. In this study, we investigated a role of Skp2, which targets CDK2 inhibitor p27/Kip1, in actin damage-induced tetraploid G1 arrest. Expression of Skp2 was reduced, but p27/Kip1 was increased, after actin damage-induced cytokinesis blockade. The role of Skp2 repression in tetraploid G1 arrest was investigated by analyzing the effects of ectopic expression of Skp2. After actin damage, ectopic expression of Skp2 resulted in DNA synthesis and accumulation of multinucleated cells, and ultimately, induction of apoptosis. These results suggest that Skp2 repression is important for sustaining tetraploid G1 arrest after cytokinesis blockade and is required to prevent uncoupled DNA replication and nuclear division without cytokinesis.

• BMB Reports
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• v.46 no.1
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• pp.25-30
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• 2013

Gap junctions and their structural proteins, connexins (Cxs), have been implicated in carcinogenesis. To explore the involvement of Cx32 in gastric carcinogenesis, immunochemical analysis of Cx32 and proliferation marker Ki67 using tissue-microarrayed human gastric cancer and normal tissues was performed. In addition, after Cx32 overexpression in the human gastric cancer cell line AGS, cell proliferation, cell cycle analyses, and $p21^{Cip1}$ and $p27^{Kip1}$ expression levels were examined by bromodeoxyuridine assay, flow cytometry, real-time RT-PCR, and western blotting. Immunohistochemical study noted a strong inverse correlation between Cx32 and Ki67 expression pattern as well as their location. In vitro, overexpression of Cx32 in AGS cells inhibited cell proliferation significantly. $G^1$ arrest, up-regulation of cell cycle-regulatory proteins $p21^{Cip1}$ and $p27^{Kip1}$ was also found at both mRNA and protein levels. Taken together, Cx32 plays some roles in gastric cancer development by inhibiting gastric cancer cell proliferation through cell cycle arrest and cell cycle regulatory proteins.

• Molecules and Cells
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• v.28 no.1
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• pp.37-42
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• 2009

Iron binding lactoferrin (Lf) is involved in the control of cell cycle progression. However, the molecular basis underlying the effects of Lf on cell cycle control, as well as its target genes, remains incompletely understood. In this study, we have demonstrated that a relatively low level of ironsaturated Lf, Lf($Fe^{3+}$), can stimulate S phase cell cycle entry, and requires Akt activation in MCF-7 cells. Lf($Fe^{3+}$) immediately induced Akt phosphorylation at Ser473, which subsequently induced the phosphorylation of two G1-checkpoint Cdk inhibitors, $p21^{Cip/WAF1}$ and $p27^{kip1}$. The Lf($Fe^{3+}$)-induced phosphorylation of Cdk inhibitors impaired their nuclear import behavior, thereby inducing cell cycle progression. However, the treatment of cells with a PI3K inhibitor, LY294002, almost completely blocked Lf($Fe^{3+}$)-stimulated cell cycle progression. LY294002 treatment abrogated Lf($Fe^{3+}$)-induced Akt activation, and prevented the cytoplasmic localization of $p27^{kip1}$. Higher levels of $p21^{Cip/WAF1}$ were also detected in the cytoplasmic sub-cellular compartment as a measure of cellular response to Lf($Fe^{3+}$). Consequently, the degree of phosphorylation of retinoblastoma protein was enhanced in response to Lf($Fe^{3+}$). Therefore, we conclude that Lf($Fe^{3+}$), as a potential antagonist of Cdk inhibitors, can facilitate the functions of E2F during progression to S phase via the Akt signaling pathway.

• Biomolecules & Therapeutics
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• v.19 no.2
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• pp.187-194
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• 2011

Atherosclerosis and post-angiography restenosis are associated with intimal thickening and concomitant vascular smooth muscle cell (VSMC) proliferation. Obovatol, a major biphenolic component isolated from the Magnolia obovata leaf, is known to have anti-inflammatory and anti-tumor activities. The goal of the present study was to enhance the inhibitory effects of obovatol to improve its potential as a preventive or therapeutic agent in atherosclerosis and restenosis. Platelet-derived growth factor (PDGF)-BB-induced proliferation of rat aortic smooth muscle cells (RASMCs) was examined in the presence or absence of a newly synthesized obovatol derivative, OD78. The observed anti-proliferative effect of OD78 was further investigated by cell counting and [$^3H$]-thymidine incorporation assays. Treatment with 1-4 ${\mu}M$ OD78 dose-dependently inhibited the proliferation and DNA synthesis of 25 ng/ml PDGF-BB-stimulated RASMCs. Accordingly, OD78 blocked PDGF-BB-induced progression from the $G_0/G_1$ to S phase of the cell cycle in synchronized cells. OD78 decreased the expression levels of CDK4, cyclin E, and cyclin D1 proteins, as well as the phosphorylation of retinoblastoma protein and proliferating cell nuclear antigen; however, it did not change the CDK2 expression level. In addition, OD78 inhibited downregulation of the cyclin-dependent kinase inhibitor (CKI) $p27^{kip1}$. However, OD78 did not affect the CKI $p21^{cip1}$ or phosphorylation of early PDGF signaling pathway. These results suggest that OD78 may inhibit PDGF-BB-induced RASMC proliferation by perturbing cell cycle progression, potentially through $p27^{kip1}$ pathway activation. Consequently, OD78 may be developed as a potential anti-proliferative agent for the treatment of atherosclerosis and angioplasty restenosis.

• Biomedical Science Letters
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• v.23 no.4
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• pp.327-332
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• 2017

A2B adenosine receptor (A2BAR) is known to be a regulator of bone homeostasis, but the regulatory mechanism of A2BAR on the osteoclast proliferation are poorly explored. Recently, we have shown that stimulation with BAY 60-6583, a specific agonist of A2BAR, significantly reduced macrophage-colony stimulating factor (M-CSF)-induced osteoclast proliferation by inducing cell cycle arrest at G1 phase and increasing the apoptosis of osteoclasts. The objective of this study was to investigate the regulatory mechanisms of cell cycle and apoptosis by A2BAR stimulation. The expression of A2BAR and M-CSF receptor, c-Fms, was not changed by A2BAR stimulation whereas M-CSF effectively induced c-Fms expression during osteoclast proliferation. Interestingly, A2BAR stimulation remarkably increased the expression of $p27^{Kip-1}$, a cell cycle inhibitor, but the expression of Cyclin D1 and cdk4 was not affected. In addition, while BAY 60-6583 treatment reduced the expression of Bcl2, an anti-apoptotic oncogene, it failed to regulate the expression of Bax, a pro-apoptotic marker. Taken together, these results imply that the increase of $p27^{Kip-1}$ inducing cell cycle arrest at G1 phase and the decrease of Bcl2 inducing anti-apoptotic response by A2BAR stimulation contribute to the down-regulation of osteoclast proliferation.

• Laboraroty Animal Research
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• v.34 no.4
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• pp.264-269
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• 2018

Cell cycle dysfunction can cause severe diseases, including neurodegenerative disease and cancer. Mutations in cyclin-dependent kinase inhibitors controlling the G1 phase of the cell cycle are prevalent in various cancers. Mice lacking the tumor suppressors $p16^{Ink4a}$ (Cdkn2a, cyclin-dependent kinase inhibitor 2a), $p19^{Arf}$ (an alternative reading frame product of Cdkn2a,), and $p27^{Kip1}$ (Cdkn1b, cyclin-dependent kinase inhibitor 1b) result in malignant progression of epithelial cancers, sarcomas, and melanomas, respectively. Here, we generated knockout mouse models for each of these three cyclin-dependent kinase inhibitors using engineered nucleases. The $p16^{Ink4a}$ and $p19^{Arf}$ knockout mice were generated via transcription activator-like effector nucleases (TALENs), and $p27^{Kip1}$ knockout mice via clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9 (CRISPR/Cas9). These gene editing technologies were targeted to the first exon of each gene, to induce frameshifts producing premature termination codons. Unlike preexisting embryonic stem cell-based knockout mice, our mouse models are free from selectable markers or other external gene insertions, permitting more precise study of cell cycle-related diseases without confounding influences of foreign DNA.

• The Journal of Korean Obstetrics and Gynecology
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• v.18 no.1
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• pp.169-180
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• 2005

Objective : Spatholobus Suberectus Dunn stems, Chinese vine plants, have been used for the relief of menstrual disorders and rheumatic arthralgia. In this study, we investigated the antitumor effect of Spatholobus Suberectus Dunn on cervical cancer in vitro. Methods : HeLA cervical cancer cell lines were used as targets. We examined the effect of water extract from Spatholobus Suberectus Dunn on cell proliferation, cell cycle regulation and cell cycle-regulating gene expression. Further, we investigated the apoptotic effects of Spatholobus Suberectus Dunn on cervical cancer cell lines. Results : Spatholobus Suberectus Dunn significantly inhibited the proliferation of cervical cancer cell lines in a dose-dependent and time dependent manner. Fluorescence activated cell sorter (FACS) analysis indicated that Spatholobus Suberectus Dunn induced G1 cell cycle arrest. Spatholobus Suberectus Dunn enhanced the expression of $p21^{waf1}$ and $p27^{kip1}$ with cell cycle arrest. Further, Spatholobus Suberectus Dunn stimulated apoptosis via caspase3 pathway. Conclusions : These findings suggest that Spatholobus Suberectus Dunn is a candidate agent for the treatment of cervical cancer. p21waf1 and $p21^{waf1}$ and $p27^{kip1}$ may play an important role in Spatholobus Suberectus Dunn-induced cell cycle arrest and cell growth inhibition.

• Proceedings of the PSK Conference
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• 2000.10a
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• pp.206.3-207
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• 2000

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1640-1647
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• 2015

We recently reported that the antimicrobial peptide Lumbricusin (NH₂-RNRRWCIDQQA), isolated from the earthworm, increases cell proliferation in neuroblastoma SH-SY5Y cells. Here, we investigated whether Lumbricusin has neurotropic activity in mouse neural stem cells (MNSCs) and a protective effect in a mouse model of Parkinson's disease (PD). In MNSCs isolated from mouse brains, Lumbricusin treatment significantly increased cell proliferation (up to 12%) and reduced the protein expression of p27^Kip1 through proteasomal protein degradation but not transcriptional regulation. Lumbricusin inhibited the 6-OHDA-induced apoptosis of MNSCs, and also showed neuroprotective effects in a mouse PD model, ameliorating the motor impairments seen in the pole, elevated body swing, and rotation tests. These results suggest that the Lumbricusin-induced promotion of neural cell proliferation via p27^Kip1 degradation has a protective effect in an experimental PD model. Thus, the antimicrobial peptide Lumbricusin could possibly be developed as a potential therapeutic agent for the treatment of PD.

• The Journal of Internal Korean Medicine
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• v.25 no.4
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• pp.274-288
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• 2004

Objectives : This study was designed to evaluate the effect on cytotoxicity of Bojungikki-tang(BIT) in human lung cancer H460 cells. Methods : BIT-induced cell death was confirmed as apoptosis characterized by chromatin condensation and increase of the $sub-G_1$, DNA content. It was tested whether the water extract of BIT affects the cell cycle regulators such as, p2l/Cipl, p27/Kipl, cyclin $B_1$. Results : The data showed that treatment of BIT decreased the viability of H460 cells in a dose-dependent manner. p2l/Cip1 is gradually decreased by the addition of the cells with BIT extract. Interestingly, p27/Kip1 is not detected for 24 hr after the addition of BIT extract, however, after 24 hr, p27/Kipl markedly increased. In addition, cyclin $B_1$, decreased in a time dependent manner after the addition of the water extract. The activation of caspase -3 protease was further confirmed by degradation of procaspase-8 protease andpoly(ADP-ribose) polymerase(P ARP) by BIT in H460 cells. Moreover, BIT induced the increase of Bak expression. Conclusion : These results suggest that the extract of BIT exerts anticancer effects to induce the death of human lung cancer H460 cells via down regulation of cell cycle regulators such as p2l/Cip1, and cyclin B1 or up regulation of cell cycle regulators such as p27/Kip1. Moerover results suggest that BIT induces an apoptosis in H460 cells via activation of intrinsic caspase cascades.