Inhibition of Cyclin F Promotes Cellular Senescence through Cyclin-dependent Kinase 1-mediated Cell Cycle Regulation

Objective Kidney renal clear cell carcinoma(KIRC)is a common renal malignancy that has a poor prognosis.As a member of the F box family,cyclin F(CCNF)plays an important regulatory role in normal tissues and tumors.However,the underlying mechanism by which CCNF promotes KIRC proliferation still remains unclear.Methods Bioinformatics methods were used to analyze The Cancer Genome Atlas(TCGA)database to obtain gene expression and clinical prognosis data.The CCK8 assay,EdU assay,and xenograft assay were used to detect cell proliferation.The cell senescence and potential mechanism were assessed by SA-β-gal staining,Western blotting,as well as ELISA.Results Our data showed that CCNF was highly expressed in KIRC patients.Meanwhile,downregulation of CCNF inhibited cell proliferation in vivo and in vitro.Further studies showed that the reduction of CCNF promoted cell senescence by decreasing cyclin-dependent kinase 1(CDK1),increasing the proinflammatory factors interleukin(IL)-6 and IL-8,and then enhancing the expression of p21 and p53.Conclusion We propose that the high expression of CCNF in KIRC may play a key role in tumorigenesis by regulating cell senescence.Therefore,CCNF shows promise as a new biomarker to predict the clinical prognosis of KIRC patients and as an effective therapeutic target.

Expression of cyclin-dependent protein kinase 5 in the hippocampus of vascular dementia mice after cerebral ischemia and reperfusion

BACKGROUND： The p25-activated cyclin-dependent protein kinase 5 （Cdk5） may induce neuronal cell death and cause the development of dementia following cerebral ischemia and reperfusion. OBJECTIVE： To observe changes in the expression of Cdk5 and p25 in hippocampal tissue of vascular dementia mice at different time points following cerebral ischemia and reperfusion. DESIGN, TIME AND SETTING： A randomized, controlled animal experiment was performed in the clinical trial center of Hebei Provincial People＇s Hospital between September 2007 and October 2008. MATERIALS： Cdk5 rabbit anti-mouse polyclonal antibody, p35 rabbit anti-mouse polyclonal antibody, and β-actin mouse monoclonal antibody were purchased from Santa Cruz Biotechnology, Inc., USA; horseradish peroxidase-labeled goat anti-rabbit IgG and horseradish peroxidase-labeled goat anti-mice IgG were offered by Beijing Zhongshan Geldenbridye Biotechnology Co.,Ltd., China; the protein quantitative kit was produced by Applygen Gene Technology Corp., Beijing, China; cDNA reverse transcription and PCR amplification reagents were products of TianGen＆ Biotech （Beijing） Co.,Ltd., China. METHODS： One hundred and sixty male Kunming mice were randomly divided into two groups： a sham-operated group （n = 65） and a model group （n = 95）. Vascular dementia was induced with three periods of transient ischemia and reperfusion of the bilateral common carotid arteries. In the sham-operated group, the bilateral common carotid arteries were not blocked. MAIN OUTCOME MEASURES： Behavioral tests were done at four and six weeks post surgery. Pathological changes in the hippocampal CA1 region were observed with hematoxylin-eosin staining Cdk5 mRNA expression was examined by RT-PCR, and Western blots were used to evaluate Cdk5 and p25 expression. Learning and memory performance were assayed using the Morris water maze. RESULTS： Vascular dementia reduced learning and memory performance at 4 and 6 weeks post surgery. Vascular dementia also caused severe, time-dependent neuronal damage and death in the hippocampal CA1 region. Dementia induction also increased mRNA and protein expression of Cdk5 and p25 at both 4 and 6 weeks after surgery. CONCLUSION： Cdk5/p25 is involved in the development of vascular dementia in mice following cerebral ischemia and reperfusion.

Expression of cyclin-dependent kinase inhibitor 2A 16,tumour protein 53 and epidermal growth factor receptor in salivary gland carcinomas is not associated with oncogenic virus infection

It is known that human papillomavirus （HPV） infection can cause squamous cell neoplasms at several sites, such as cervix uteri carcinoma and oral squamous carcinoma. There is little information on the expression of HPV and its predictive markers in tumours of the major and minor salivary glands of the head and neck. We therefore assessed oral salivary gland neoplasms to identify associations between HPV and infection-related epidermal growth factor receptor （EGFR）, cyclin-dependent kinase inhibitor 2A （CDKN2A/p16） and tumour protein p53 （TP53）. Formalin-fixed, paraffin-embedded tissue samples from oral salivary gland carcinomas （n=51） and benign tumours （n=26） were analysed by polymerase chain reaction （PCR） analysis for several HPV species, including high-risk types 16 and 18. Evaluation of EGFR, CDKN2A, TP53 and cytomegalovirus （CMV） was performed by immunohistochemistry. Epstein-Barr virus （EBV） was evaluated by EBV-encoded RNA in situ hybridisation. We demonstrated that salivary gland tumours are not associated with HPV infection. The expression of EGFR, CDKN2A and TP53 may be associated with tumour pathology but is not induced by HPV. CMV and EBV were not detectable. In contrast to oral squamous cell carcinomas, HPV, CMV and EBV infections are not associated with malignant or benign neoplastic lesions of the salivary glands.

Cyclin-dependent kinase 5 is required for suppressing D1-dependent signaling mediated through muscarinic 4 in isolated medium spiny neurons

OBJECTIVE Previous studies have demonstrated acetylcholine muscarinic 4(M4) receptor regulates DARPP-32 phosphorylation at Thr75 in isolated medium spiny neurons(MSNs),indicating antagonistic mechanism with D1 dependent signal cascade,but the exact molecular mechanisms remain unclearly.In this study,we investigated the roles of M4 receptor in modulation D1 dependent signal to integrate striatal DA inputs in isolated MSNs.METHODS(1)Lentivirus technology was employed to genetically knock down the M4 receptor of MSNs;(2) Apomorphine(APO),acts as a dopamine receptor agonist,while SCH23390,acts as a selective antagonist for D1,were used to study the pharmacologically profiles with D1 receptor stimulation or blockade,respectively.Then the no subtype-selective muscarinic agonist oxotremorine M(OX) were used to show that mAchRs activation,in order to dissect the particular function of M4,a selective M4 antagonist,MT3 was used;(3) Intracellular cAMP production of MSNs was measured by using time resolved fluorescence resonance energy transfer detection method;(4) Laser confocal was used to explore the expression of M4 and D1 in MSNs;(5) Immunofluorescence cytochemistry and Western blotting were used to confirm the alteration of signaling molecular including P-CREB,DARPP-32 P-Thr34,DARPP-32 P-Thr75,cyclin-dependent kinase 5(CDK5) as wel as p25/35,which are involved in DA-dependent signaling modulations.RESULTS Firstly,TR-FRET assay revealed APO(10-2 mol·L^(-1))significantly increased the level of intracellular cAMP(vs control,n=3,P<0.01),also Western blotting results showed that APO(10-6 mol · L^(-1))increased DARPP-32 Thr34 phosphorylation(vs control,n=3,P<0.01),and these effect were reversed by D1 receptor antagonist SCH23390(vs APO,n=3,P<0.01).Interestingly,we confirmed that OX(10-6 mol · L^(-1)) down-regulated APO-induced DARPP-32 Thr34 phosphorylation(vs APO,n=3,P<0.01),due to its effects on DARPP-32 phosphorylation at Thr75.The results presented the antagonistic mechanism of mAchRs stimulation with D1 dependent signal cascade in MSNs.Meanwhile,OX(10-7,10-6 and10^(-5) mol·L^(-1)) stimulated DARPP-32 phosphorylation at Thr75,and simultaneously up regulated P25/35 and CDK5 activity(vs control,n=3,P<0.01) by using Western blotting assay.Furthermore,roscovitine(10^(-5) mol · L^(-1)),acts as a CDK5 inhibitor,suppressed CDK5 activity(vs control,n=10,P<0.01),and fully inhibited OX-induced DARPP-32 Thr75 phosphorylation(vs OX,n=10,P<0.01).More important,pretreated with roscovitine(10^(-5) mol·L^(-1)),the effect of APO on DARPP-32 Thr34 phosphorylation was potentiated(vs APO,n=3,P<0.05).The result presented CDK5 is required in suppression of APO on DARPP-32 Thr34 phosphorylation mediated through mAchRs stimulation.In addition,laser confocal results showed that the CDK5 up-regulation was mostly confined to MSNs co-expressing M4,which means that M4 participated in CDK5-mediated phosphorylation of DARPP-32 at Thr75.Consistently,immunofluorescence and Western blotting results confirmed that both genetic knockdown and pharmacologic inhibition of M4 receptors with MT3(10-7 mol · L^(-1)) down-regulated the OX-induced the expression of CDK5(vs OX,n=3,P<0.01) and P25/35(vs OX,n=3,P<0.01)in isolated MSNs.CONCLUSION M4 receptor may play an important role in antagonistic regulation D1 dependent signaling,in which CDK5 is required for suppressing D1-DARPP-32 Thr34 phosphorylation in isolated medium spiny neurons.

Can cyclin-dependent kinase 4/6 inhibitors convert inoperable breast cancer relapse to operability? A case report

BACKGROUND Pathological complete response(pCR) is rare in hormone receptor-positive(HR+)HER2-negative breast cancer(BC) treated with either endocrine therapy(ET) or chemotherapy. Radical resection of locoregional relapse, although potentially curative in some cases, is challenging when the tumor invades critical structures.The oral cyclin-dependent kinase 4/6 inhibitor palbociclib in combination with ET has obtained a significant increase in objective response rates and progression-free survival in patients with advanced BC and is now being evaluated in the neoadjuvant setting. We present a clinical case of a patient with an inoperable locoregional relapse of HR+ HER2-negative BC who experienced p CR after treatment with palbociclib.CASE SUMMARY We report the clinical case of a 60-year-old patient who presented with an inoperable locoregional relapse of HR+, HER2-negative BC 10 years after the diagnosis of the primary tumor. During a routine follow-up visit, breast magnetic resonance imaging and positron emission tomography/computed tomography revealed a 4-cm lesion in the right subclavicular region, infiltrating the chest wall and extending to the subclavian vessels, but without bone or visceral involvement. Treatment was begun with palbociclib plus letrozole, converting the disease to operability over a period of 6 mo. Surgery was performed and a p CR achieved. Of note, during treatment the patient experienced a very uncommon toxicity characterized by burning tongue and glossodynia associated with dysgeusia, paresthesia, dysesthesia, and xerostomia. A reduction in the dose of palbociclib did not provide relief and treatment with the inhibitor was thus discontinued, resolving the tongue symptoms. Laboratory exams were unremarkable. Given that this was a late relapse, the tumor was classified asendocrine-sensitive, a condition associated with high sensitivity to palbociclib.CONCLUSION This case highlights the potential of the cyclin-dependent kinase 4/6 inhibitor plus ET combination to achieve pCR in locoregional relapse of BC, enabling surgical resection of a lesion initially considered inoperable.

Expression of cyclin-dependent kinases in HL-60 cells during differentiation induced by retinoic acid

This study was designed to investigate the relationship of the expression of cyclin-dependent kinases (CDKs) with theeffects of all-trans retinoic acid (ATRA) on the proliferation of HL-cells. HL-60 cells were treated with ATRA for 1-4 d. Then thecapacity of DNA Synthesis was evaluated with 3H-TdR incorporation and the expression of cyclin E, cyclin D, CDK2 and CDK4protein determined with immunocytochemical staining. In addition, the expression Of CDC2, CDK2 and CDK4 mRNA was deter-mined with in situ hybridization. It was found that ATRA suppressed the proliferation of HL-60 cells and decreased their capacityof DNA synthesis to result in a down-regulation of the expression of cyclin E, cyclin D and CDC2 without comcomittant suppressionon the expression of CDK2 and CDK4. It is concluded that the effects of ATRA on the proliferation of HL-60 cells may be relatedto the down-regulation of the expression of cyclin E, cyclin D and CDC2.

Cyclin-dependent kinase inhibitors in brain cancer:current state and future directions

Cyclin-dependent kinases(CDKs)are important regulatory enzymes in the normal physiological processes that drive cell-cycle transitions and regulate transcription.Virtually all cancers harbour genomic alterations that lead to the constitutive activation of CDKs,resulting in the proliferation of cancer cells.CDK inhibitors(CKIs)are currently in clinical use for the treatment of breast cancer,combined with endocrine therapy.In this review,we describe the potential of CKIs for the treatment of cancer with specific focus on glioblastoma(GBM),the most common and aggressive primary brain tumour in adults.Despite intense effort to combat GBM with surgery,radiation and temozolomide chemotherapy,the median survival for patients is 15 months and the majority of patients experience disease recurrence within 6-8 months of treatment onset.Novel therapeutic approaches are urgently needed for both newly diagnosed and recurrent GBM patients.In this review,we summarise the current preclinical and clinical findings emphasising that CKIs could represent an exciting novel approach for GBM treatment.

Cyclin-dependent kinases-based synthetic lethality: Evidence, concept, and strategy

Synthetic lethality is a proven effective antitumor strategy that has attracted great attention.Large-scale screening has revealed many synthetic lethal genetic phenotypes,and relevant smallmolecule drugs have also been implemented in clinical practice.Increasing evidence suggests that CDKs,constituting a kinase family predominantly involved in cell cycle control,are synthetic lethal factors when combined with certain oncogenes,such as MFC,TP53,and RAS,which facilitate numerous antitumor treatment options based on CDK-related synthetic lethality.In this review,we focus on the synthetic lethal phenotype and mechanism related to CDKs and summarize the preclinical and clinical discoveries of CDK inhibitors to explore the prospect of CDK inhibitors as antitumor compounds for strategic synthesis lethality in the future.

Expression of cyclin-dependent kinase inhibitor genes induces apoptosis in human hepatoma cell line

APOPTOSIS is an active, inherently programmed cell death, which has typical morphologicaland biochemical characteristics. Cell death during embryonic development, shaping of the Tand B lymphocyte and tissue dystrophy related to endocrine is designated a physiological apop-tosis by which cell numbers can be effectively controlled. As a process opposite to cell division,there is a balance between apoptosis and cell proliferation. A tumor will develop once the bal-ance is disturbed and the cell division is more rapid than the cell death. Also, apoptosis is un-der the control of multiple molecular components, while cell division is under the control of thecell cycle engine. The precise control of cell proliferation and differentiation is essential for

Discovery of 4-Thiazol-N-(pyridin-2-yl)pyrimidin-2-amine as Novel Cyclin-dependent Kinases 4 and 6 Dual Inhibitors via 3D-QSAR and Molecular Simulation

Cyclin D dependent kinases 4/6 regulate the entry of cells into S phase and are effective target for the discovery of anticancer drugs.In this article,3D-QSAR modeling including comparative molecular field analy-sis(CoMFA)and comparative molecular similarity indices analysis fields(CoMSIA)was implemented on 52 dual CDK4/6 inhibitors.As a result,we obtained a pretty good 3D-QSAR model,which is CoMFACDK4 with q2 to be 0.543 and r^(2) to be 0.967;CoMSIACDK4 with q2 being 0.518 and r^(2) being 0.937;CoMFACDK6 with q2 to be 0.624 and r^(2) to be 0.984;CoMSIACDK6 with q2 being 0.584 and r^(2) being 0.975.Molecular docking confirmed the important residues for interactions.Molecular dynamics simulation further confirmed binding affinity with key residues of protein,such as Lys22,Lys35,Val96 for CDK4 and Lys43,His100,Val101 for CDK6 at the active sites.Then these results offered new directions to explore new inhibitors of CDK4/6.Finally,we designed 10 novel compounds with promising expected activity and ADME/T properties,and provided referable synthetic routes.

Radiosynthesis of N-^(11) C-meisoindigotin as a novel PET agent for imaging of cyclin-dependent kinases and GSK-3β

Meisoindigotin has been demonstrated as a new type of cancer chemotherapeutic agent.N-^（11）C-meisoindigotin was synthesized by N-^（11）C-methyIation of the isoindigotin precursor with ^（11）C-labelled methyl triflate.The decay corrected radiochemical yields were 15-25%,and the specific radioactivity was 1.0-1.2 Ci/μmol at the end of synthesis.The cellular uptake of[N-^（11）C]-meisoindigotin was evaluated in four different lung cancer cell lines.Our results showed that the A549,GLC-82,95D cell lines exhibited higher uptake than 95C cell line after incubation for 60 min.N-^（11）-meisoindigotin was a promising candidate for further development as a novel PET radiotracer for imaging of cyclin-dependent kinases（CDKs） and GSK-3β.

Neuroprotective Effects of Tongmai Yizhi Decoction(通脉益智汤)against Alzheimer's Disease through Attenuating Cyclin-Dependent Kinase-5 Expression

Objectives： To explore the protective effects of Tongmai Yizhi Decoction（通脉益智汤, TYD）, a Chinese herb complex prescription against the impairment of cognitive functions and memory loss in amyloid beta 1–40（Aβ1-40） peptide and ibotenic（IBO）-induced Alzheimer＇s disease（AD） model rats. Methods： The in vivo model was established by injecting Aβ1-40 and IBO into left hippocampal CA1 area of Sprague-Dawley（SD） rat to mimic AD. Totally 32 SD rats were divided into 4 groups, including sham operation group, AD model group, TYD group [AD rats treated with TYD at the dosage of 19.44 g/（kg·d） for 4 weeks] and huperzine A group [AD rats treated with huperzine A at the dosage of 40.5 μg/（kg·d） for 4 weeks]. Spatial learning and memory level was detected by Morris Water Maze test. Histological morphology in the hippocampus was tested by hematoxylin-eosin（HE） staining. Cyclin-dependent kinase-5（Cdk5） protein and gene expression level were investigated by Western blot analysis and real-time quantitative polymerase chain reaction（RT-q PCR）, respectively. Results： Aβ1-40 and IBO treatment induced longer escape latency of rats, compared with sham operation group from day 25（P〈0.01）. However, TYD and huperzine A obviously shortened the escape latency from day 26（P〈0.01）. Moreover, the effect of TYD was similar to huperzine A（P〉0.05）. Furthermore, HE staining also showed that TYD and huperzine A reversed the neuropathological changes in the hippocampus triggered by Aβ1-40 and IBO. TYD and huperzine A effectively reduced the expression levels of Cdk5 protein and gene located in rat hippocampus, compared with the AD model group（P〈0.01）. Conclusion： TYD could be a promising neuroprotective agent for protecting neuron from AD injury through inhibiting Cdk5 expression.

Cyclin-dependent kinase 7 inhibitor THZ1 in cancer therapy

Current cancer therapies have encountered adverse response due to poor therapeutic efficiency,severe side effects and acquired resistance to multiple drugs.Thus,there are urgent needs for finding new cancer-targeted pharmacological strategies.In this review,we summarized the current understanding with THZ1,a covalent inhibitor of cyclin-dependent kinase 7(CDK7),which demonstrated promising anti-tumor activity against different cancer types.By introducing the anti-tumor behaviors and the potential targets for different cancers,this review aims to provide more effective approaches to CDK7 inhibitor-based therapeutic agents and deeper insight into the diverse tumor proliferation mechanisms.

Human cytomegalovirus RNA2.7 inhibits RNA polymeraseⅡ(PolⅡ)Serine-2 phosphorylation by reducing the interaction between PolⅡand phosphorylated cyclin-dependent kinase 9(pCDK9)

Human cytomegalovirus(HCMV)is a ubiquitous pathogen belongs to betaherpesvirus subfamily.RNA2.7 is a highly conserved long non-coding RNA accounting for more than 20%of total viral transcripts.In our study,functions of HCMV RNA2.7 were investigated by comparison of host cellular transcriptomes between cells infected with HCMV clinical strain and RNA2.7 deleted mutant.It was demonstrated that RNA polymeraseⅡ(PolⅡ)-dependent host gene transcriptions were significantly activated when RNA2.7 was removed during infection.A145 nt-in-length motif within RNA2.7 was identified to inhibit the phosphorylation of PolⅡSerine-2(PolⅡS2)by reducing the interaction between PolⅡand phosphorylated cyclin-dependent kinase 9(pCDK9).Due to the loss of PolⅡS2 phosphorylation,cellular DNA pre-replication complex(pre-RC)factors,including Cdt1 and Cdc6,were significantly decreased,which prevented more cells from entering into S phase and facilitated viral DNA replication.Our results provide new insights of HCMV RNA2.7 functions in regulation of host cellular transcription.

Novel insights into D-Pinitol based therapies:a link between tau hyperphosphorylation and insulin resistance

Alzheimer’s disease is a neurodegenerative disorder characterized by the amyloid accumulation in the brains of patients with Alzheimer’s disease.The pathogenesis of Alzheimer’s disease is mainly mediated by the phosphorylation and aggregation of tau protein.Among the multiple causes of tau hyperphosphorylation,brain insulin resistance has generated much attention,and inositols as insulin sensitizers,are currently considered candidates for drug development.The present narrative review revises the interactions between these three elements:Alzheimer’s disease-tau-inositols,which can eventually identify targets for new disease modifiers capable of bringing hope to the millions of people affected by this devastating disease.

Molecular Mechanism of KDM5B Development in Hepatocellular Carcinoma

Objective: To investigate the mechanism of cell cyclin-dependent kinase (KDM5B), a key enzyme driving all cell cycle transitions, promoting HCC progression and metastasis. Methods: The expression of KDM5B in normal liver, HCC and its adjacent tissues was analyzed by RT-PCR and IHC. Lentivirus transfection method was used to construct stable cell lines with KDM5B overexpression and down-regulation, and the role of KDM5B in HCC migration and invasion was detected at cell level and animal level. Western blotting and Transwell experiments were performed to verify the effect of KDM5B and/or CCR2 inhibitors on HCC progression and metastasis by using liver orthotopic transplantation tumor model and immunofluorescence methods. Results: RT-PCR showed that the expression level of KDM5B in HCC was significantly higher than that in adjacent tissues, and the increase of KDM5B was relatively significant. Upregulation of KDM5B in nude mouse liver orthotopic transplantation tumor model can promote the incidence of lung metastasis and shorten the survival time of nude mice, whereas upregulation of KDM5B can reduce the incidence of lung metastasis and prolong the survival time of nude mice. Conclusion: This study clarified the expression of KDM5B in HCC and its function in promoting HCC migration, invasion and metastasis. The molecular mechanism of KDM5B promoting HCC metastasis was revealed, providing a potential therapeutic target for HCC.

Long non-coding RNA H19 promotes proliferation inhepatocellular carcinoma cells via H19/miR-107/CDK6 axis

Hepatocellular carcinoma (HCC) is the leading cause of cancer death worldwide;nevertheless, currenttherapeutic options are limited or ineffective for many patients. Therefore, elucidation of molecular mechanisms inHCC biology could yield important insights for the intervention of novel therapies. Recently, various studies havereported dysregulation of long non-coding RNAs (lncRNAs) in the initiation and progression of HCC, including H19;however, the biological function of H19 in HCC remains unclear. Here, we show that knockdown of H19 disruptedHCC cell growth, impaired the G1-to-S phase transition, and promoted apoptosis, while overexpression of H19yielded the opposite results. Screening for expression of cell cycle-related genes revealed a significant downregulationof CDK6 at both RNA and protein levels upon H19 suppression. Bioinformatic analysis of the H19 sequence and the3′ untranslated region (3′ UTR) of CDK6 transcripts showed several binding sites for microRNA-107 (miR-107), andthe dual luciferase reporter assay confirmed their direct interaction with miR-107. Consistently, blockage of miR-107activity alleviated the growth suppression phenotypes induced by H19 downregulation, suggesting that H19 serves asa molecular sponge for miR-107 to promote CDK6 expression and cell cycle progression. Together, this studydemonstrates a mechanistic function of H19 in driving the proliferation of HCC cells and suggests H19 suppressionas a novel approach for HCC treatment.

P25/CDK5-mediated Tau Hyperphosphorylation in Both Ipsilateral and Contralateral Cerebra Contributes to Cognitive Deficits in Post-stroke Mice

Objective Post-stroke cognitive impairment(PSCI)develops in approximately one-third of stroke survivors and is associated with ingravescence.Nonetheless,the biochemical mechanisms underlying PSCI remain unclear.The study aimed to establish an ischemic mouse model by means of transient unilateral middle cerebral artery occlusions(MCAOs)and to explore the biochemical mechanisms of p25/cyclin-dependent kinase 5(CDK5)-mediated tau hyperphosphorylation on the PSCI behavior.Methods Cognitive behavior was investigated,followed by the detection of tau hyperphosphorylation,mobilization,activation of kinases and/or inhibition of phosphatases in the lateral and contralateral cerebrum of mice following ischemia in MACO mice.Finally,we treated HEK293/tau cells with oxygen-glucose deprivation(OGD)and a CDK5 inhibitor(Roscovitine)or a GSK3βinhibitor(LiCl)to the roles of CDK5 and GSK3βin mediating ischemia-reperfusion-induced tau phosphorylation.Results Ischemia induced cognitive impairments within 2 months,as well as causing tau hyperphosphorylation and its localization to neuronal somata in both ipsilateral and contralateral cerebra.Furthermore,p25 that promotes CDK5 hyperactivation had significantly higher expression in the mice with MCAO than in the shamoperation(control)group,while the expression levels of protein phosphatase 2(PP2A)and the phosphorylation level at Tyr307 were comparable between the two groups.In addition,the CDK5 inhibitor rescued tau from hyperphosphorylation induced by OGD.Conclusion These findings demonstrate that upregulation of CDK5 mediates tau hyperphosphorylation and localization in both ipsilateral and contralateral cerebra,contributing to the pathogenesis of PSCI.

小干扰RNA阻断周期蛋白依赖激酶4对子宫内膜癌细胞生物学行为的影响

背景与目的:细胞周期蛋白依赖激酶4(cyclin-dependent kinase 4,CDK4)是调控细胞周期进程的重要激酶之一,有实验报道其在子宫内膜癌中呈高表达,但是其在子宫内膜癌细胞中的生物学功能及其可能机制还不十分明确。本研究旨在通过小干扰RNA(small interfering RNA,siRNA)沉默CDK4表达,并检测其对人子宫内膜癌HEC-1B细胞生物学行为的影响及其可能机制。方法:将化学合成的CDK4-siRNA转染至HEC-1B细胞;实时荧光定量PCR法检测转染前后细胞中CDK4的mRNA表达量变化;Western blot检测转染前后细胞CDK4、视母细胞瘤基因(retinoblastoma gene,Rb)及其下游p-Rb的蛋白表达量的变化;分别采用CCK-8法、流式细胞仪、Transwell肿瘤细胞侵袭实验检测细胞增殖、周期、凋亡以及侵袭能力的变化。结果:转染后HEC-1B细胞中CDK4 mRNA及蛋白表达均明显下降(P<0.01);抑制CDK4表达后,抑制HEC-1B细胞的增殖及侵袭,转染si-CDK4组细胞发生侵袭数为(117±21)个,而转染si-control组及未处理组分别为(269±39)个和(262±35)个,差异具有统计学意义(P<0.01);细胞转染后早期凋亡率为(21.7±3.5)%,较未处理组[(12.4±2.1)%]和si-control组[(11.8±1.9)%]明显增加(P<0.01);细胞周期分布发生变化,G1期比例增加(P<0.01),S期细胞比例降低(P<0.01);进一步的Western blot结果显示,抑制CDK4表达后,细胞内p-Rb表达下降,但是总Rb表达无明显变化。结论:针对CDK4基因的特异性小RNA干扰片段能够下调CDK4基因在子宫内膜癌细胞中的表达,抑制肿瘤生物学进程。

Promoter methylation status of hMLH1,MGMT,and CDKN2A/p16 in colorectal adenomas

AIM:To investigate aberrant DNA methylation of CpG islands and subsequent low-or high-level DNA microsatellite instability(MSI)which is assumed to drive colon carcinogenesis. METHODS:DNA of healthy individuals,adenoma(tu-bular or villous/tubulovillous)patients,and colorectal carcinoma patients who underwent colonoscopy was used for assessing the prevalence of aberrant DNA methylation of human DNA mismatch repair gene mutator L homologue 1(hMLH1),Cyclin-dependent kinase inhibitor 2A(CDKN2A/p16),and O-6-methylguanine DNA methyltransferase(MGMT),as well as their rela- tion to MSI. RESULTS:The frequency of promoter methylation for each locus increased in the sequence healthy tissue/adenoma/carcinoma.MGMT showed the highest frequency in each group.MGMT and CDKN2A/p16 presented a statistically significant increase in promoter methylation between the less and more tumorigenic forms of colorectal adenomas(tubular vs tubullovillous and villous adenomas).All patients with tubulovillous/villous adenomas,as well as all colorectal cancer patients,showed promoter methylation in at least one of the examined loci.These findings suggest a potentially crucial role for methylation in the polyp/adenoma to cancer progres- sion in colorectal carcinogenesis.MSI and methylation seem to be interdependent,as simultaneous hMLH1, CDKN2A/p16,and MGMT promoter methylation was present in 8/9 colorectal cancer patients showing the MSI phenotype. CONCLUSION:Methylation analysis of hMLH1,CD- KN2A/p16,and MGMT revealed specific methylation profiles for tubular adenomas,tubulovillous/villous adenomas,and colorectal cancers,supporting the use of these alterations in assessment of colorectal tumorigenesis.