Levels Of Cyclin-dependent Kinase Research Articles

PKMYT1: A Potential Target for CCNE1 Amplificated Colorectal Tumors.

Colorectal cancer is a malignant tumor with higher morbidity and mortality. The purpose of this study is to investigate whether inhibition of Protein Kinase, Membrane Associated Tyrosine/Threonine 1 (PKMYT1) affects tumor cell proliferation, survival and migration in colon tumors with high Cyclin E1 (CCNE1) expression. PcDNA3.1-CCNE1 vector and si-PKMYT1 were transfected in SW480 cells by Lipofectamine 2000. Q-PCR and western blot assay were processed to detect the expression. Transwell assay and Edu assay were undertaken to verify the migration and proliferation. CCNE1 promotes the proliferation and migration of SW480. Silencing of PKMYT1 inhibited the proliferation of tumor cells. Silencing the expression of PKMYT1 under the premise of overexpression of CCNE1, the level of Cyclin Dependent Kinase 1 (CDK1)-PT14 was reduced, indicating that the cell cycle was blocked. The expression of γH2AX increased significantly, indicating that the DDR pathway of tumor cells was activated and DNA damage accumulated. The results of immunofluorescence microscopy showed significantly increased expression of DNA damage-associated marker (γH2AX: H2AX Variant Histone). In CCNE1 amplificated colorectal tumor cells, knockdown of PKMYT1 reduced cells in S phase, inhibited cell proliferation and promoted cell apoptosis, confirming that PKMYT1 was a potential therapeutic target for colorectal tumor. This study may verify a potential therapeutic target and provide a new idea for the treatment of colorectal cancer in the future.

Cyclins and CDKs in the regulation of meiosis-specific events.

How eukaryotic cells control their duplication is a fascinating example of how a biological system self-organizes specific activities to temporally order cellular events. During cell cycle progression, the cellular level of CDK (Cyclin-Dependent Kinase) activity temporally orders the different cell cycle phases, ensuring that DNA replication occurs prior to segregation into two daughter cells. CDK activity requires the binding of a regulatory subunit (cyclin) to the core kinase, and both CDKs and cyclins are well conserved throughout evolution from yeast to humans. As key regulators, they coordinate cell cycle progression with metabolism, DNA damage, and cell differentiation. In meiosis, the special cell division that ensures the transmission of genetic information from one generation to the next, cyclins and CDKs have acquired novel functions to coordinate meiosis-specific events such as chromosome architecture, recombination, and synapsis. Interestingly, meiosis-specific cyclins and CDKs are common in evolution, some cyclins seem to have evolved to acquire CDK-independent functions, and even some CDKs associate with a non-cyclin partner. We will review the functions of these key regulators in meiosis where variation has specially flourished.

Role of LncRNA CASC11 in the malignant transformation of 16HBE cells induced by glycidyl methacrylate

To investigate the effect of trending up-regulation LncRNA CASC11 which is differentially expressed during the malignant transformation of human bronchial epithelial cells(16 HBE) induced by glycidyl methacrylate(GMA). After 16 HBE cells were repeatedly exposed to low concentration GMA(8 μg/mL), the 10 th, 20 th and 30 th passage cells of the GMA group and the DMSO solvent control group were collected. High throughput LncRNA microarray were used to screen the differentially expressed LncRNAs at different stages. Short Time-series Expression Miner and bioinformatics tool RPISeq were used to screen and predict the potential targets of specific LncRNA. Real-time fluorescent quantitative PCR(qPCR) and Western blot were used to detect the relative expression of specific LncRNA and the content of its target protein respectively. The specific differential expression of LncRNA CASC11 in the process of GMA-induced malignant transformation of 16 HBE cells showed a trend of up-regulation. Compared with the control cells in the same period, the P10, P20 and P30 generation cells were down-regulated by 1.64 times, up-regulated by 2.01 times, and up-regulated by 2.66 times, respectively. Western blot showed that the levels of cyclin-dependent kinase 1(CDK1), cyclinB1 and cyclinB2 in P10, P20 and P30 cells after exposure were lower than those in DMSO control group during the same period, which was consistent with the microarray results. The differential expression of LncRNA CASC11 in the process of GMA-induced 16 HBE cell malignant transformation was up-regulated trendingly. It is speculated that it may block or delay cell cycle progression by inhibiting CDK1.

Triple-negative breast cancer cells rely on kinase-independent functions of CDK8 to evade NK-cell-mediated tumor surveillance

Triple-negative breast cancer (TNBC) is an aggressive malignant disease that is responsible for approximately 15% of breast cancers. The standard of care relies on surgery and chemotherapy but the prognosis is poor and there is an urgent need for new therapeutic strategies. Recent in silico studies have revealed an inverse correlation between recurrence-free survival and the level of cyclin-dependent kinase 8 (CDK8) in breast cancer patients. CDK8 is known to have a role in natural killer (NK) cell cytotoxicity, but its function in TNBC progression and immune cell recognition or escape has not been investigated. We have used a murine model of orthotopic breast cancer to study the tumor-intrinsic role of CDK8 in TNBC. Knockdown of CDK8 in TNBC cells impairs tumor regrowth upon surgical removal and prevents metastasis. In the absence of CDK8, the epithelial-to-mesenchymal transition (EMT) is impaired and immune-mediated tumor-cell clearance is facilitated. CDK8 drives EMT in TNBC cells in a kinase-independent manner. In vivo experiments have confirmed that CDK8 is a crucial regulator of NK-cell-mediated immune evasion in TNBC. The studies also show that CDK8 is involved in regulating the checkpoint inhibitor programmed death-ligand 1 (PD-L1). The CDK8–PD-L1 axis is found in mouse and human TNBC cells, underlining the importance of CDK8-driven immune cell evasion in these highly aggressive breast cancer cells. Our data link CDK8 to PD-L1 expression and provide a rationale for investigating the possibility of CDK8-directed therapy for TNBC.

Identification of the Effects of Chondroitin Sulfate on Inhibiting CDKs in Colorectal Cancer Based on Bioinformatic Analysis and Experimental Validation.

With a high occurrence rate and high mortality, the treatment of colorectal cancer (CRC) is increasingly attracting the attention of scholars. Hub genes that determine the phenotypes of CRC become essential for targeted therapy. In the present study, the importance of cyclin-dependent kinases (CDKs) on the occurrence of CRC was identified by data mining of The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). The results showed that the gene expression levels of CDK1, CDK4, and CDK6 were obviously changed in different stages of CRC. Among the CDKs, CDK4 was suggested as an independent risk factor for CRC based on Cox analysis. Furthermore, chondroitin sulfate (CS), a kind of dietary supplement to treat osteoarthritis, was predicted to treat CRC based on its chemical structure and GEO datasets. Cell assay experiments with the human CRC cell line HCT-116 also verified this prediction. CS inhibited the gene and protein expression levels of CDKs and increased the ratios of apoptotic or dead HCT-116 cells by regulating mitogen-activated protein (MAP) kinase pathways. Our data highlight the essential roles of CDKs in CRC carcinogenesis and the effects of CS on treating CRC, both of which will contribute to the future CRC treatment.

Synergistic Impact of Xanthorrhizol and d-δ-Tocotrienol on the Proliferation of Murine B16 Melanoma Cells and Human DU145 Prostate Carcinoma Cells

Isoprenoids suppress the mevalonate pathway that provides prenyl groups for the posttranslational modification of growth-regulating proteins. We hypothesize that xanthorrhizol and d-δ-tocotrienol synergistically suppress the growth of murine B16 melanoma and human DU145 prostate carcinoma cells. Xanthorrhizol (0–200 µmol/L; half maximal inhibitory concentration [IC50] = 65 µmol/L) and d-δ-tocotrienol (0–40 µmol/L; IC50 = 20 µmol/L) each induced a concentration-dependent suppression of the proliferation of B16 cells and concurrent cell cycle arrest at the G1 phase. A blend of 16.25 µmol/L xanthorrhizol and 10 µmol/L d-δ-tocotrienol suppressed B16 cell proliferation by 69%, an impact greater than the sum of those induced by xanthorrhizol (15%) and d-δ-tocotrienol (12%) individually. The blend cumulatively reduced the levels of cyclin-dependent kinase four and cyclin D1, key regulators of cell cycle progression at the G1 phase. The expression of RAS and extracellular signal-regulated kinase (ERK1/2) in the proliferation-stimulating RAS-RAF-MEK-ERK pathway was downregulated by the blend. Xanthorrhizol also induced a concentration-dependent suppression of the proliferation of DU145 cells with concomitant morphological changes. Isobologram confirmed the synergistic effect of xanthorrhizol and d-δ-tocotrienol on DU145 cell proliferation with combination index values ranging 0.61-0.94. Novel combinations of isoprenoids with synergistic actions may offer effective approaches in cancer prevention and therapy.

Knockdown of GINS2 inhibits proliferation and promotes apoptosis through the p53/GADD45A pathway in non-small-cell lung cancer.

Lung cancer is a malignant tumour type with the highest morbidity and mortality, and non-small-cell lung cancer (NSCLC) is the most common pathological type. GINS complex subunit 2 (GINS2) is a member of the GINS family and is closely related to DNA replication and damage, participates in cell cycle regulation and plays a key role in cell proliferation and apoptosis. In the present study, we aimed to explore the role and underlying molecular mechanism of GINS2 in the development of NSCLC. The results showed that GINS2 is significantly increased in NSCLC tissues and cell lines. Knockdown of GINS2 significantly decreases cell proliferation, causing G2/M phase cell cycle arrest. Knockdown of GINS2 reverses the effect of nocodazole on the levels of cyclin-dependent kinase 1 (CDK1) and cyclin-B1. Meanwhile, knockdown of GINS2 significantly elevates the apoptosis rate and apoptosis-related protein Bax and decreases Bcl-2. In addition, GINS2 knockdown induces an increase in the levels of p53 and growth arrest and DNA damage 45A (GADD45A). Co-transfection with GINS2-siRNA and siRNA against p53 (p53-siRNA) or co-transfection with GINS2-siRNA and siRNA against GADD45A (GADD45A-siRNA) partially reverses the effects of GINS2 knockdown on cell proliferation and apoptosis. Taken together, these results indicate that GINS2 knockdown down-regulates cell proliferation, induces G2/M phase cell cycle arrest and increases apoptosis, possibly through the p53/GADD45A pathway.

2-(6-Hydroxyhexylthio)-5,8-dimethoxy-1,4-naphthoquinone Induces Apoptosis through ROS-Mediated MAPK, STAT3, and NF-κB Signalling Pathways in Lung Cancer A549 Cells.

Two novel compounds, 2-(2-hydroxyethylthio)-5,8-dimethoxy-1,4-naphthoquinone (HEDMNQ) and 2-(6-hydroxyhexylthio)-5,8-dimethoxy-1,4-naphthoquinone (HHDMNQ), were synthesized to investigate the kill effects and mechanism of 1,4-naphthoquinone derivatives in lung cancer cells. The results of the CCK-8 assay showed that HEDMNQ and HHDMNQ had significant cytotoxic effects on A549, NCI-H23, and NCI-H460 NSCLC cells. Flow cytometry and western blot results indicated that HHDMNQ induced A549 cell cycle arrest at the G2/M phase by decreasing the expression levels of cyclin-dependent kinase 1/2 and cyclin B1. Fluorescence microscopy and flow cytometry results indicated that HHDMNQ could induce A549 cell apoptosis, and western blot analysis showed that HHDMNQ induced apoptosis through regulating the mitochondria pathway, as well as the MAPK, STAT3, and NF-κB signalling pathways. Flow cytometry results showed that intracellular reactive oxygen species (ROS) levels were increased after HHDMNQ treatment, and western blot showed that ROS could modulate the intrinsic pathway and MAPK, STAT3, and NF-κB signalling pathways. These effects were blocked by the ROS inhibitor N-acetyl-L-cysteine in A549 cells. Our findings suggest that compared with HEDMNQ, HHDMNQ had the stronger ability to inhibit the cell viability of lung cancer cells and induce apoptosis by regulating the ROS-mediated intrinsic pathway and MAPK/STAT3/NF-κB signalling pathways. Thus, HHDMNQ might be a potential antitumour compound for treating lung cancer.

Keratin 19 regulates cell cycle pathway and sensitivity of breast cancer cells to CDK inhibitors

Keratin 19 (K19) belongs to the keratin family of proteins, which maintains structural integrity of epithelia. In cancer, K19 is highly expressed in several types where it serves as a diagnostic marker. Despite the positive correlation between higher expression of K19 in tumor and worse patient survival, the role of K19 in breast cancer remains unclear. Therefore, we ablated K19 expression in MCF7 breast cancer cells and found that K19 was required for cell proliferation. Transcriptome analyses of KRT19 knockout cells identified defects in cell cycle progression and levels of target genes of E2F1, a key transcriptional factor for the transition into S phase. Furthermore, proper levels of cyclin dependent kinases (CDKs) and cyclins, including D-type cyclins critical for E2F1 activation, were dependent on K19 expression, and K19-cyclin D co-expression was observed in human breast cancer tissues. Importantly, K19 interacts with cyclin D3, and a loss of K19 resulted in decreased protein stability of cyclin D3 and sensitivity of cells towards CDK inhibitor-induced cell death. Overall, these findings reveal a novel function of K19 in the regulation of cell cycle program and suggest that K19 may be used to predict the efficacy of CDK inhibitors for treatments of breast cancer.

Restoration of Cdk5, TrkB and Soluble N-ethylmaleimide-Sensitive Factor Attachment Protein Receptor Proteins after Chronic Methylphenidate Treatment in Spontaneous Hypertensive Rats, a Model for Attention-Deficit Hyperactivity Disorder.

ObjectiveSynaptic vesicle mobilization and neurite outgrowth regulation molecules were examined in modulation of effects of methylphenidate (MPH) in Spontaneous Hypertensive Rats (SHRs), a model for attention-deficit hyperactivity disorder (ADHD). Methods We compared the changes in the protein expression level of Cyclin dependent kinase 5 (Cdk5) and molecular substrates of Cdk5; tropomyosin receptor kinase B (TrkB), syntaxin 1A (STX1A) and synaptosomal-associated protein 25 (SNAP25). Comparisons were made in prefrontal cortex of vehicle (distilled water i.p. for 7 days)-treated SHRs, vehicle-treated Wistar Kyoto Rats (WKYs) and MPH (2 mg/kg i.p. for 7 days) treated SHRs. ResultsThe Cdk5 level of vehicle-treated SHRs was significantly decreased compared to the Cdk5 level of vehicle-treated WKY rats, but was restored to the expression level of vehicle-treated WKYs in MPH-treated SHR. The ratio of p25/p35 was significantly decreased in MPH-treated SHR compared to vehicle-treated SHR. Moreover, TrkB, STX1A and SNAP25 of vehicle-treated SHRs were significantly decreased compared to vehicle-treated WKY rats, but were restored to the expression level of vehicle-treated WKYs in MPH-treated SHR. ConclusionThe results show that Cdk5, TrkB, STX1A, and SNAP25 were involved in the modulation of MPH effects in prefrontal cortex of SHRs and play important role in treatment of ADHD.

Buforin IIb induced cell cycle arrest in liver cancer

ABSTRACTThe inhibitory effect of buforin IIb on different types of cancer, although not liver cancer, has been demonstrated previously. The aim of the present study was to investigate the effects of buforin IIb on the progression of liver cancer. The human liver cancer cell line HepG2 was treated with purified buforin IIb and the cell activity was determined by MTT, colony formation and transwell assays. The protein expression levels of cyclin-dependent kinases (CDKs) and cyclins were analyzed by western blotting and immunofluorescent cell staining. A tumor growth model was constructed using nude mice, and buforin IIb treatment was administered. The levels of CDK2 and cyclin A in the tumor tissues were detected by western blotting. Buforin IIb treatment depressed cell viability and colony formation and induced apoptosis significantly, and 1.0 µM concentration of buforin IIb was found to be the optimal dosage. The cell cycle was arrested at the G2/M phase following buforin IIb treatment. CDK2 and cyclin A were downregulated by treatment of the cells with 1.0 µM buforin IIb for 24 h. Treatment with buforin IIb also inhibited the migration of liver cancer cells in vitro. Furthermore, 50 nmol buforin IIb injection suppressed HepG2 cell subcutaneous tumor growth in the nude mouse model. Similar to the in vitro results, buforin IIb injection reduced the expression of CDK2 and cyclin A in the tumor tissue. these results demonstrate that buforin IIb inhibited liver cancer cell growth via the regulation of CDK2 and cyclin A expression.

Abstract P1-04-01: Estrogen receptor β agonists inhibits syngeneic mammary tumor growth through cell-cycle arrest by modulating cell-cycle regulators

Abstract Breast Cancer is the main cause of cancer-associated mortality in women worldwide. The estrogen receptors (ER's) play an important role in normal mammary gland development, as well as in breast cancer. Estrogen Receptor α is expressed in 70% of breast cancers, where it contributes to increased cell proliferation and decreased cell death. Endocrine therapies such as anti-estrogens and aromatase inhibitors target ERα signaling and improve outcomes of these patients. Syngeneic, immunocompetent mouse models are essential for elucidating the mechanisms and for evaluating novel strategies for the treatment of breast cancer. In contrast to the tumor-inducing role of ERα, ERβ has been shown to have tumor suppressive activities in various cancer, including the breast cancer. Compounds that selectively activate ERβ hold promise because they could potentially avoid the unwanted effects of ERα activation, while exploiting the tumor-suppressive function of ERβ. In the present study, we assessed the antitumor effects of ERβ agonists using three different syngeneic mouse models; D2A1 (BALB/c) and MM51 (FVB) syngeneic models and ex-vivo culture of highly metastatic cell line E0771 (C57/B6). Effect on in vitro cancer cell growth was evaluated by cell proliferation and clonogenic assays. Cell cycle distribution was analysed by flow cytometry. Our results demonstrate that ERβ agonists LY500307 and S-Equol not only inhibited the growth of all three mouse mammary tumor cell lines, but also reduced the colony formation ability. ERβ agonists also induced the cell-cycle arrest in time and dose-dependent manner. In mechanistic studies, ERβ agonists LY500307 and S-Equol, modulated the protein levels of cyclin-dependent kinases (CDKs) (4, 6, and 2), cyclins (D1 and E), in a differential manner in these three cell lines. Our in vivo studies of D2A1 and MM51 cells demonstrates that ERβ agonist LY500307 inhibited the tumor growth and the effect was more pronounce in combination with aromatase inhibitor letrozole. Ex-vivo model of E0771 cells showed that LY500307 has potential to dramatically reduce the proliferation of mouse mammary tumor growth.Together, these results identify potential molecular targets and anticancer effects of ERβ agonists in mouse mammary tumors. Citation Format: Ramasamy K, Samayoa C, Krishnegowda NK, Thurlapati A, Vadlamudi RK, Tekmal RR. Estrogen receptor β agonists inhibits syngeneic mammary tumor growth through cell-cycle arrest by modulating cell-cycle regulators [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-04-01.

Profound, durable and MGMT-independent sensitivity of glioblastoma cells to cyclin-dependent kinase inhibition.

TG02 is a novel cyclin-dependent kinase (CDK) inhibitor and thought to act mainly via CDK-9 inhibition-dependent depletion of short-lived oncoproteins such as MCL-1 or c-MYC. We studied the activity of TG02 in 9 human long-term glioma cell lines (LTC) and 5 glioma-initiating cell lines (GIC) using various cell death assays in vitro and in the LN-229 LTC and ZH-161 GIC models in vivo. TG02 exhibits strong anti-tumor cell activity with EC50 concentrations in the nanomolar range. Median survival in the LN-229 and ZH-161 models was moderately prolonged by TG02. Neither constitutive CDK levels nor those of MCL-1 or c-MYC correlated with sensitivity to TG02. Cdk-9 or cdk-5 gene silencing alone did not fully reproduce the effects of TG02. C-myc gene silencing inhibited cell growth, but did not modulate TG02 activity. Electron microscopy revealed cell death to be essentially apoptotic. High concentrations of TG02 induced annexin V binding and minor caspase 3 cleavage, but the pan-caspase inhibitor, zVAD-fmk, or BCL-2 or MCL-1 gene transfer only moderately attenuated TG02-induced cell death, and caspase inhibition did not prevent loss of MCL-1 or c-MYC. TG02 activity was independent of O6 -methylguanine DNA methyltransferase expression. Repetitive exposure to TG02 did not generate an acquired TG02 resistance phenotype, but accumulation of MCL-1, loss of c-MYC, or senescence. TG02 is a highly potent apoptosis-inducing agent in glioma cells in vitro. Caspase inhibition does not rescue TG02-treated cells and repetitive exposure fails to confer acquired resistance, supporting the clinical evaluation of TG02 in glioblastoma.

C-glycosyl flavone from Urginea indica inhibits proliferation & angiogenesis & induces apoptosis via cyclin-dependent kinase 6 in human breast, hepatic & colon cancer cell lines.

Background & objectives:Search for novel compounds beneficial to the treatment of cancer attracts a great deal of attention. We earlier demonstrated the isolation of 5,7-dihydroxy-2-[4’-hydroxy-3’-(methoxymethyl)phenyl]-6-C-β-glucopyranosyl flavone, a novel C-glycosyl flavone from Urginea indica bulb. The present study was undertaken to investigate the effect of this novel compound on human normal epithelial and breast, hepatic and colon cancer cell lines.Methods:The maximum non-toxic concentration (MNTC) and cytotoxicity of C-glycosyl flavone were assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Cell cycle was analyzed by flow cytometry. Docking studies were performed to predict possible targets. Levels of cyclin-dependent kinase 1 (CDK1) and CDK6, Bcl2 and BAX and cytochrome c were quantified by specific ELISA. Mitochondrial membrane potential was determined using JC-1 dye. Apoptosis was quantified by Annexin V ELISA method.Results:Flow cytometry analysis demonstrated G0/G1 arrest. In silico docking studies predicted CDK1 and CDK6 as a possible target of C-glycosyl flavone. In vitro study confirmed CDK6 as the main target in C-glycosyl flavone-treated cancer cell lines. C-glycosyl flavone treatment also induced membrane blebbing, chromatin fragmentation and nucleosome formation. C-glycosyl flavone treatment caused marked loss of mitochondrial membrane potential, decrease in Bcl2/BAX ratio and activation of caspase-3 and release of caspase-9 and cytochrome c. In addition, C-glycosyl flavone inhibited the tumour-induced angiogenesis and reduced the vascular endothelial growth factor levels. Similarly, CDK6 inhibitor significantly inhibited proliferation and angiogenesis and induced apoptosis in tested cell lines.Interpretation & conclusions:The results indicate that C-glycosyl flavone may exert induction of apoptosis, cell cycle arrest and inhibition of angiogenesis via CDK6. Thus, targeting CDK6 using C-glycosyl flavone may serve as a novel therapeutic approach for the treatment of breast, hepatic and colon cancers.

Antitumor effect of Quercetin on Y79 retinoblastoma cells via activation of JNK and p38 MAPK pathways

BackgroundQuercetin (QCT) is a flavonol present in many vegetables, it is proved to show chemo preventive effect against lung, cervical, prostate, breast and colon cancer due to its anti-inflammatory, anti-tumor and anti-oxidant property. Looking into the reported chemo-preventive effect we speculated antitumor activity in retinoblastoma (RB) Y79 cells, we also studied the molecular mechanism for antitumor activity.MethodsThe effect of QCT on Y79 cell viability count was done by cell counting kit, cell cycle distribution, apoptosis studies and mitochondrial membrane potential was evaluated by flow cytometry. Protein expression was done by western blot analysis.ResultsThe outcomes of study showed that QCT reduced Y79 cell viability and caused arrest of G1 phase in cell cycle via decreasing the expression levels of cyclin-dependent kinase (CDK)2/6 and cyclin D3 and by increasing the levels of both CDK inhibitor proteins p21 and p27. Apoptosis of Y79 cells mediated by QCT occurred via activation of both caspases-3/-9. Flow cytometry studies showed that QCT caused collapse in mitochondrial membrane potential (ΔΨm) in Y79 cells. Western blot studies confirmed that QCT brought about phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). We also established that inhibitors of JNK and p38 MAPK suppressed QCT mediated activation of both caspases-3/-9 and subdued the apoptosis of cancerous Y79 cells.ConclusionAll the results of the study suggest that QCT induced the apoptosis of Y79 cells via activation of JNK and p38 MAPK pathways, providing a novel treatment approach for human RB.

P1-280 - Phytohemagglutinin chemosensitizes lung cancer cells to Liposomal Cisplatin by cell cycle arrest

Phytohemagglutinin (PHA) has mitogenic and potent cell agglutinating activities. It binds to T-cell membranes and stimulates cell division and metabolic activity. PHA has the ability to stimulate close contacts between cell membranes. Lipoplatin (Liposomal cisplatin) is a nanoparticle of 110 nm average diameter composed of lipids and cisplatin. This new drug has successfully finished Phase I, Phase II and Phase III human clinical trials. It has shown superiority to cisplatin in combination with paclitaxel as a chemotherapy regimen in non-small cell lung cancer (NSCLC) adenocarcinomas. The aim of this study was to investigate whether PHA would be able to enhance the antitumor effects of Lipoplatin in MCF-7 and MDA-MB-231 cells. PHA potentiated the cytotoxic effects of Lipoplatin in human lung cancer cells. This finding was related to the ability of PHA to sensitize MCF-7 cells to Lipoplatin-induced apoptosis. The sensitization by PHA involved the enhancement of p53 levels, the decrease of procaspase 8 and the activation of caspases 7 and 9. Another proposed mechanism for the chemosensitization effect of MCF-7 cells to Lipoplatin by PHA was the cell cycle arrest in the S phase. The treatment with PHA or Lipoplatin increased the levels of p-Chk2. The increase became pronounced in the combined treatments of the compounds. The expression of cyclin A was decreased by treatment with PHA and by the combination of PHA with Lipoplatin. While the levels of cyclin dependent kinase 2 (CDK2) remained unchanged by treatments, its active form (Thr(160) -phosphorylated CDK2) was decreased by treatment with PHA and by the combination of PHA with Lipoplatin. The activity of CDK7, kinase that phosphorylates CDK2 at Thr(160), was inhibited by PHA and by the combination of PHA with Lipoplatin. These results indicate that PHA could be used as an adjuvant agent during lung cancer therapy with Lipoplatin.

Rubiarbonone C inhibits platelet-derived growth factor-induced proliferation and migration of vascular smooth muscle cells through the focal adhesion kinase, MAPK and STAT3 Tyr705 signalling pathways.

The proliferation and migration of vascular smooth muscle cells (VSMCs) induced by platelet-derived growth factor (PDGF) are important steps in cardiovascular diseases, including neointimal lesion formation, myocardial infarction and atherosclerosis. Here, we evaluated the rubiarbonone C-mediated signalling pathways that regulate PDGF-induced VSMC proliferation and migration. Cell proliferation and migration were measured in cells treated with rubiarbonone C followed by PDGF BB using the MTT assay, [3 H]-thymidine incorporation, flow cytometry and wound-healing migration assay, MMP gelatin zymography, a fluorescence assay for F-actin. Western blotting of molecules including MAPK, focal adhesion kinase (FAK) and STAT3 and an immunofluorescence assay using anti-PCNA and -STAT3 antibodies were performed to evaluate rubiarbonone C signalling pathway(s). The medial thickness of the carotid artery was evaluated using a mouse carotid ligation model. Rubiarbonone C inhibited PDGF-induced VSMC proliferation and migration and diminished the ligation-induced increase in medial thickness of the carotid artery. In PDGF-stimulated VSMCs rubiarbonone C decreased the following: (i) levels of cyclin-dependent kinases, cyclins, PCNA and hyperphosphorylated retinoblastoma protein; (ii) levels and activity of MMP2 and MMP9; (iii) activation of MAPK; (iv) F-actin reorganization, by reducing FAK activation; (v) activation of STAT3. These findings suggest that rubiarbonone C inhibits the proliferation and migration of VSMCs by inhibiting the FAK, MAPK and STAT3 signalling pathways. Therefore, rubiarbonone C could be a good candidate for the treatment of cardiovascular disease.

Abstract 5940: The HU177 collagen neo-epitope regulates nuclear YAP accumulation and melanoma tumor growth and metastasis in vivo

Abstract The extracellular matrix (ECM) plays a central role in controlling cellular behavior and integrin receptors play key roles in this process. Significant molecular insight is available on how structurally intact forms of collagen regulate integrin-signaling, however unique collagen neo-epitopes can be generated during tumor development and these neo-epitopes may differentially bind to integrin receptors. These findings raise an interesting question as to whether signaling initiated by collagen neo-epitopes as compared to intact collagen, differentially modify the final signaling out-put. Integrin A10B1 is a receptor for the HU177 collagen neo-epitope, however, little is known about the down stream signaling events stimulated by this receptor-ligand interaction. We provide evidence that melanoma cell interaction with denatured collagen results in enhanced adhesion and migration. Talin is a molecule that facilitates integrin-associated linkages to the cytoskeleton and helps govern adhesive cellular processes. Melanoma cell interactions with denatured as compared to intact collagen, resulted in enhanced Talin phosphorylation and surprisingly increased the levels of Cyclin Dependent Kinase 5 (CDK5), a molecule implicated in Talin phosphorylation and motility. Melanoma cell interactions with denatured collagen also led to elevated nuclear accumulation of the Yes-associated protein YAP. Given these results, we examined the effects of anti-HU177 antibody on adhesion and migration. Targeting the HU177 neo-epitope inhibited cell adhesion and migration on denatured collagen and also inhibited YAP nuclear accumulation. Knocking down YAP in melanoma cells resulted in the generation of cells that were resistant to the inhibitory effects of anti-HU177 antibody, suggesting that part of the inhibitory activity of anti-HU177 antibody may be associated with its ability to alter YAP activity. We next examined the role of the HU177 neo-epitope and its receptor, A10B1, on melanoma tumor growth and metastasis. Targeting the HU177 neo-epitope inhibited tumor-angiogenesis, accumulation of ASMA positive stromal cells in melanomas and tumor growth in vivo. Importantly, knock down of A10B1, or direct targeting of the HU177 neo-epitope inhibited experimental metastasis of melanoma cells. Taken together, these studies provide new insight into the role of the HU177 collagen neo-epitope in melanoma tumor growth and metastasis and provide a novel strategy to inhibit melanoma progression through selective targeting of a A10B1 ligand, rather than the integrin itself. Citation Format: Xianghua Han, Jennifer M. Caron, Peter C. Brooks. The HU177 collagen neo-epitope regulates nuclear YAP accumulation and melanoma tumor growth and metastasis in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5940. doi:10.1158/1538-7445.AM2017-5940

Sevoflurane anesthesia induces apoptosis and cell cycle arrest in NPC-039 nasopharyngeal cells

Purpose: To determine the effects of sevoflurane on NPC-039 nasopharyngeal carcinoma cells. Methods: WST-8 assays and flow cytometry with annexin V/PI staining were used to analyze the effects of sevoflurane on growth and induction of apoptotic changes in NPC-039 cells. Cell viability was performed on a microplate reader. Results: Treatment of NPC-039 cells with 4 – 10 μM sevoflurane significantly inhibited cell growth (p < 0.005) with a median inhibitory concentration of 6 μM. NPC-039 cells incubated with sevoflurane showed prominent nuclear fragmentation and chromatin condensation. NPC-039 cells that exhibited apoptotic symptoms increased from 23.34 to 56.77 % when duration of treatment was increased from 24 to 48 h. Sevoflurane-treated cells also expressed increased levels of Bax and cleaved caspase-3. Reactive oxygen species formation was also higher in sevoflurane-treated NPC-039 cells than in control. Pre-treatment with Z-VAD-FMK followed by incubation with sevoflurane partly reduced the population of apoptotic NPC-039 cells compared with cells treated with sevoflurane alone. The proportion of cells in S- and G0/G1 phases decreased and increased, respectively, when sevoflurane concentration was increased from 2 to 10 μM. Incubating NPC-039 cells with sevoflurane also markedly reduced levels of cyclin-dependent kinases including p15 INK4B, cyclin D1, p16 INK4A, and CDK-6. In contrast, pretreatment with ZVAD-FMK followed by incubation with sevoflurane increased p15 INK4B levels. Conclusion: Sevoflurane inhibits nasopharyngeal carcinoma cell growth, activating apoptosis and inducing cell cycle arrest, thus suggesting its therapeutic potential for the treatment of nasopharyngeal carcinoma. Keywords: Sevoflurane, Nasopharyngeal carcinoma, Chromatin, Condensation

The effects of miRNA-577 on the function of human gastric cancer cells

Objective To investigate the effects of miRNA-577 on the cell proliferation and migration of human gastric cancer cell line SGC-7901, and to explore its mechanism. Methods The expression levels of miRNA-577 in human gastric mucosal epithelial cells GES (gastric epithelial cells) and human gastric cancer cell line SGC-7901 were detected by real-time polymerase chain reaction (RT-PCR). Gastric cancer SGC-7901 cells were infected with transfected with miRNA-577 or control miRNA vector. Transwell assay, methyl thiazolyl tetrazolium (MTT) test, and flow cytometry were used in both groups. Western blot was used to detect the level of cyclin dependent kinase 4 (CDK4) protein. Results Compared to GES, the expression level of miRNA-577 was decreased significantly in gastric cancer cell lines (P<0.01). The ratio of proliferation inhibition, and cells arrested at G1/G0 phase were increased significantly in miRNA-577 lentiviral infected group compared to the negative control group (P<0.05). CDK4 protein expression was lower in the miRNA-577 lentiviral infected group(P<0.01). Conclusions miRNA-577 has lower expression level in gastric caner cell line SGC-7901. miRNA-577 can inhibit proliferation, induce cell cycle arrest of gastric caner cell line SGC-7901, maybe through downregulating expression of CDK4. Key words: MicroRNAs/ME/PD; Stomach neoplasms/ME/DT; Cyclin-dependent kinase 4/ME