Cell cycle and apoptosis

Platelet-rich plasma increases proliferation of tendon cells by modulating Stat3 and p27 to up-regulate expression of cyclins and cyclin-dependent kinases

OBJECTIVES

To investigate effects of platelet-rich plasma on tendon cell proliferation and the underlying molecular mechanisms.

MATERIALS AND METHODS

Platelet-rich plasma was prepared manually by two-step centrifugation. Proliferation was evaluated in cultured rat tendon cells by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Cell cycle progression was assessed by flow cytometry. Messenger RNA expression of proliferating cell nuclear antigen (PCNA), cyclin E1, A2 and B1, and cyclin-dependent kinases (Cdks) 1 and 2 was assessed by real-time polymerase chain reaction. Protein expression of the above cyclins and Cdks and of signal transducer and activator of transcription (Stat) 3 and p27 was evaluated by western blotting.

RESULTS

Platelet-rich plasma used in the present study had concentrations of platelets, TGF-β1 and PDGF over 3-fold higher than normal whole blood. Platelet-rich plasma enhanced tendon cell proliferation (P = 0.008) by promoting G1 /S phase transition in the cell cycle, and increased expression of PCNA, cyclin E1, A2 and B1, Cdks1 and 2, and phosphorylated Stat3, while inhibiting p27 expression.

CONCLUSIONS

Platelet-rich plasma contains high concentrations of TGF-β1 and PDGF that increase tendon cell proliferation by modulating Stat3/p27(Kip1), which enhances expression of cyclin-Cdk complexes that promote cell cycle progression. These results provide molecular evidence for positive effects of platelet-rich plasma on tendon cell proliferation, which can be useful in clinical applications of tendon injury.

Shikonin causes cell-cycle arrest and induces apoptosis by regulating the EGFR-NF-κB signalling pathway in human epidermoid carcinoma A431 cells

Shikonin, a naphthoquinone pigment isolated from the Chinese herbal Zicao, has been shown to exhibit antioxidant and anticancer effects. In the present study, we investigated the antiproliferative and pro-apoptotic effects of shikonin on A431 cells and explored the underlying molecular mechanisms. In the present study, our results showed that shikonin significantly inhibited the growth of A431 cells in a concentration- and time-dependent manner, and caused cell cycle arrest by upregulation of p21 and p27, and downregulation of cyclins and cyclin-dependent kinases. In addition, shikonin evidently induced apoptosis due to decreasing Bcl-2 expression, increasing Bax expression, activating caspase and inactivating NF-κB, while pretreatment with a pan-caspase inhibitor Z-Asp-CH2-DCB abrogated shikonin-induced apoptosis. Moreover, EGF could significantly increase the NF-κB DNA-binding activity and reversed the shikonin-induced inactivation of NF-κB. As anticipated AG1478 (EGFR inhibitor) and Bay11-7082 (NF-κB inhibitor) blocked EGF-reversed the inactivation of NF-κB induced by shikonin. Our data also showed that EGF could evidently reverse the shikonin-induced decreases in cell viability and increases in apoptosis. Then, the NF-κB inhibitors such as Bay11-7082, SN50, Helenalin and the EGFR inhibitor AG1478 and its downstream inhibitor such as PI3K inhibitor LY294002 and STAT3 inhibitor Stattic dramatically blocked EGF-reversed decreases in cell viability and increases in apoptosis induced by shikonin. Collectively, our findings indicated that shikonin inhibited cell growth and caused cell cycle arrest of the A431 cells through the regulation of apoptosis. Moreover, these effects were mediated at least partially by suppressing the activation of the EGFR-NF-κB signaling pathways.

Annotation-based feature extraction from sets of SBML models

Background

Model repositories such as BioModels Database provide computational models of biological systems for the scientific community. These models contain rich semantic annotations that link model entities to concepts in well-established bio-ontologies such as Gene Ontology. Consequently, thematically similar models are likely to share similar annotations. Based on this assumption, we argue that semantic annotations are a suitable tool to characterize sets of models. These characteristics improve model classification, allow to identify additional features for model retrieval tasks, and enable the comparison of sets of models.

Results

In this paper we discuss four methods for annotation-based feature extraction from model sets. We tested all methods on sets of models in SBML format which were composed from BioModels Database. To characterize each of these sets, we analyzed and extracted concepts from three frequently used ontologies, namely Gene Ontology, ChEBI and SBO. We find that three out of the methods are suitable to determine characteristic features for arbitrary sets of models: The selected features vary depending on the underlying model set, and they are also specific to the chosen model set. We show that the identified features map on concepts that are higher up in the hierarchy of the ontologies than the concepts used for model annotations. Our analysis also reveals that the information content of concepts in ontologies and their usage for model annotation do not correlate.

Conclusions

Annotation-based feature extraction enables the comparison of model sets, as opposed to existing methods for model-to-keyword comparison, or model-to-model comparison.

Electronic supplementary material

The online version of this article (doi:10.1186/s13326-015-0014-4) contains supplementary material, which is available to authorized users.

Stress management in cyst-forming free-living protists: programmed cell death and/or encystment

In the face of harsh conditions and given a choice, a cell may (i) undergo programmed cell death, (ii) transform into a cancer cell, or (iii) enclose itself into a cyst form. In metazoans, the available evidence suggests that cellular machinery exists only to execute or avoid programmed cell death, while the ability to form a cyst was either lost or never developed. For cyst-forming free-living protists, here we pose the question whether the ability to encyst was gained at the expense of the programmed cell death or both functions coexist to counter unfavorable environmental conditions with mutually exclusive phenotypes.

Impact of Melatonin on Zeitgeber Time-Dependent Changes in Cell Proliferation and Apoptosis in the Adult Murine Hypothalamic-Hypophyseal System

BACKGROUND/AIMS

Cell proliferation and apoptosis are known to adjust neuroendocrine circuits to the photoperiod. The latter is communicated by melatonin, the hormone secreted by the pineal organ. The present study investigated zeitgeber time (ZT)-dependent changes in cell proliferation and apoptosis in the adult murine neuroendocrine system and their regulation by melatonin.

METHODS

Adult melatonin-proficient (C3H/HeN) and melatonin-deficient (C57Bl/6J) mice, as well as melatonin-proficient (C3H/HeN) mice with targeted deletion of both melatonin receptor types (MT1 and MT2) were adapted to a 12-hour light, 12-hour dark photoperiod and were sacrificed at ZT00, ZT06, ZT12, and ZT18. Immunohistochemistry for Ki67 and activated caspase-3 served to identify and quantify proliferating and apoptotic cells in the median eminence (ME), hypophyseal pars tuberalis, and pars distalis (PD).

RESULTS

ZT-dependent changes in cell proliferation and apoptosis were found exclusively in melatonin-proficient mice with functional MTs. Cell proliferation in the ME and PD showed ZT-dependent changes indicated by an increase at ZT12 (ME) and a decrease at ZT06 (PD). Apoptosis showed ZT-dependent changes in all regions analyzed, indicated by an increase at ZT06. Proliferating and apoptotic cells were found in nearly all cell types residing in the regions analyzed.

CONCLUSIONS

Our results indicate that ZT-dependent changes in cell proliferation are counterbalanced by ZT-dependent changes in apoptosis exclusively in melatonin-proficient mice with functional MTs. Melatonin signaling appears to be crucial in both the generation and timing of proliferation and apoptosis that serve the high rate of physiological cell turnover in the adult neuroendocrine system.

Anti-cancer effects of Kochia scoparia fruit in human breast cancer cells

Background:

The fruit of Kochia scoparia Scharder is widely used as a medicinal ingredient for the treatment of dysuria and skin diseases in China, Japan and Korea. Especially, K. scoparia had been used for breast masses and chest and flank pain.

Objective:

To investigate the anti-cancer effect of K. scoparia on breast cancer.

Materials and Methods:

We investigated the anti-cancer effects of K. scoparia, methanol extract (MEKS) in vitro. We examined the effects of MEKS on the proliferation rate, cell cycle arrest, reactive oxygen species (ROS) generation and activation of apoptosis-associated proteins in MDA-MB-231, human breast cancer cells.

Results:

MTT assay results demonstrated that MEKS decreased the proliferation rates of MDA-MB-231 cells in a dose-dependent manner with an IC₅₀ value of 36.2 μg/ml. MEKS at 25 μg/ml significantly increased the sub-G1 DNA contents of MDA-MB-231 cells to 44.7%, versus untreated cells. In addition, MEKS induced apoptosis by increasing the levels of apoptosis-associated proteins such as cleaved caspase 3, cleaved caspase 8, cleaved caspase 9 and cleaved Poly (ADP-ribose) polymerase (PARP).

Conclusion:

These results suggest that MEKS inhibits cell proliferation and induces apoptosis in breast cancer cells and that MEKS may have potential chemotherapeutic value for the treatment of human breast cancer.

Chaetoglobosin K induces apoptosis and G2 cell cycle arrest through p53-dependent pathway in cisplatin-resistant ovarian cancer cells

Adverse side effects and acquired resistance to conventional platinum based chemotherapy have become major impediments in ovarian cancer treatment, and drive the development of more selective anticancer drugs. Chaetoglobosin K (ChK) was shown to have a more potent growth inhibitory effect than cisplatin on two cisplatin-resistant ovarian cancer cell lines, OVCAR-3 and A2780/CP70, and was less cytotoxic to a normal ovarian cell line, IOSE-364, than to the cancer cell lines. Hoechst 33342 staining and Flow cytometry analysis indicated that ChK induced preferential apoptosis and G2 cell cycle arrest in both ovarian cancer cells with respect to the normal ovarian cells. ChK induced apoptosis through a p53-dependent caspase-8 activation extrinsic pathway, and caused G2 cell cycle arrest via cyclin B1 by increasing p53 expression and p38 phosphorylation in OVCAR-3 and A2780/CP70 cells. DR5 and p21 might play an important role in determining the sensitivity of normal and malignant ovarian cells to ChK. Based on these results, ChK would be a potential compound for treating platinum-resistant ovarian cancer.

Ferulago angulata activates intrinsic pathway of apoptosis in MCF-7 cells associated with G1 cell cycle arrest via involvement of p21/p27

Ferulago angulata is a medicinal plant that is traditionally known for its anti-inflammatory and antiulcer properties. The present study was aimed to evaluate its anticancer activity and the possible mechanism of action using MCF-7 as an in vitro model. F. angulata leaf extracts were prepared using solvents in the order of increasing polarity. As determined by MTT assay, F. angulata leaves hexane extract (FALHE) revealed the strongest cytotoxicity against MCF-7 cells with the half maximal inhibitory concentration (IC₅₀) value of 5.3±0.82 μg/mL. The acute toxicity study of FALHE provided evidence of the safety of the plant extract. Microscopic and flow cytometric analysis using annexin-V probe showed an induction of apoptosis in MCF-7 by FALHE. Treatment of MCF-7 cells with FALHE encouraged the intrinsic pathway of apoptosis, with cell death transducing signals that reduced the mitochondrial membrane potential with cytochrome c release from mitochondria to cytosol. The released cytochrome c triggered the activation of caspase-9. Meanwhile, the overexpression of caspase-8 suggested the involvement of an extrinsic pathway in the induced apoptosis at the late stage of treatment. Moreover, flow cytometric analysis showed that FALHE treatment significantly arrested MCF-7 cells in the G₁ phase, which was associated with upregulation of p21 and p27 assessed by quantitative polymerase chain reaction. Immunofluorescence and the quantitative polymerase chain reaction analysis of MCF-7 cells after treatment with FALHE revealed an upregulation of Bax and a downregulation of Bcl-2 proteins. These findings proposed that FALHE suppressed the proliferation of MCF-7 cells via cell cycle arrest and the induction of apoptosis through intrinsic pathway.

Cyclin-dependent kinases regulate apoptosis of intestinal epithelial cells

Homeostasis of the gastrointestinal epithelium is dependent upon a balance between cell proliferation and apoptosis. Cyclin-dependent kinases (Cdks) are well known for their role in cell proliferation. Previous studies from our group have shown that polyamine-depletion of intestinal epithelial cells (IEC-6) decreases cyclin-dependent kinase 2 (Cdk2) activity, increases p53 and p21Cip1 protein levels, induces G1 arrest, and protects cells from camptothecin (CPT)-induced apoptosis. Although emerging evidence suggests that members of the Cdk family are involved in the regulation of apoptosis, their roles directing apoptosis of IEC-6 cells are not known. In this study, we report that inhibition of Cdk1, 2, and 9 (with the broad range Cdk inhibitor, AZD5438) in proliferating IEC-6 cells triggered DNA damage, activated p53 signaling, inhibited proliferation, and induced apoptosis. By contrast, inhibition of Cdk2 (with NU6140) increased p53 protein and activity, inhibited proliferation, but had no effect on apoptosis. Notably, AZD5438 sensitized, whereas, NU6140 rescued proliferating IEC-6 cells from CPT-induced apoptosis. However, in colon carcinoma (Caco-2) cells with mutant p53, treatment with either AZD5438 or NU6140 blocked proliferation, albeit more robustly with AZD5438. Both Cdk inhibitors induced apoptosis in Caco-2 cells in a p53-independent manner. In serum starved quiescent IEC-6 cells, both AZD5438 and NU6140 decreased TNF-α/CPT-induced activation of p53 and, consequently, rescued cells from apoptosis, indicating that sustained Cdk activity is required for apoptosis of quiescent cells. Furthermore, AZD5438 partially reversed the protective effect of polyamine depletion whereas NU6140 had no effect. Together, these results demonstrate that Cdks possess opposing roles in the control of apoptosis in quiescent and proliferating cells. In addition, Cdk inhibitors uncouple proliferation from apoptosis in a p53-dependent manner.

Annona muricata leaves induced apoptosis in A549 cells through mitochondrial-mediated pathway and involvement of NF-κB

BACKGROUND

Annona muricata leaves have been reported to have antiproliferative effects against various cancer cell lines. However, the detailed mechanism has yet to be defined. The current study was designed to evaluate the molecular mechanisms of A. muricata leaves ethyl acetate extract (AMEAE) against lung cancer A549 cells.

METHODS

The effect of AMEAE on cell proliferation of different cell lines was analyzed by MTT assay. High content screening (HCS) was applied to investigate the suppression of NF-κB translocation, cell membrane permeability, mitochondrial membrane potential (MMP) and cytochrome c translocation from mitochondria to cytosol. Reactive oxygen species (ROS) formation, lactate dehydrogenase (LDH) release and activation of caspase-3/7, -8 and -9 were measured while treatment. The western blot analysis also carried out to determine the protein expression of cleaved caspase-3 and -9. Flow cytometry analysis was used to determine the cell cycle distribution and phosphatidylserine externalization. Quantitative PCR analysis was performed to measure the gene expression of Bax and Bcl-2 proteins.

RESULTS

Cell viability analysis revealed the selective cytotoxic effect of AMEAE towards lung cancer cells, A549, with an IC50 value of 5.09 ± 0.41 μg/mL after 72 h of treatment. Significant LDH leakage and phosphatidylserine externalization were observed in AMEAE treated cells by fluorescence analysis. Treatment of A549 cells with AMEAE significantly elevated ROS formation, followed by attenuation of MMP via upregulation of Bax and downregulation of Bcl-2, accompanied by cytochrome c release to the cytosol. The incubation of A549 cells with superoxide dismutase and catalase significantly attenuated the cytotoxicity caused by AMEAE, indicating that intracellular ROS plays a pivotal role in cell death. The released cytochrome c triggered the activation of caspase-9 followed by caspase-3. In addition, AMEAE-induced apoptosis was accompanied by cell cycle arrest at G0/G1 phase. Moreover, AMEAE suppressed the induced translocation of NF-κB from cytoplasm to nucleus.

CONCLUSIONS

Our data showed for the first time that the ethyl acetate extract of Annona muricata inhibited the proliferation of A549 cells, leading to cell cycle arrest and programmed cell death through activation of the mitochondrial-mediated signaling pathway with the involvement of the NF-kB signalling pathway.

Induction of apoptosis by a peptide from Porphyra yezoensis: regulation of the insulin-like growth factor I receptor signaling pathway in MCF-7 cells

This study examined how PPY, a peptide from Porphyra yezoensis, regulates multiple cell growth-related signaling pathways in MCF-7 cells. This study determined that PPY induces cell cycle arrest and inhibits the IGF-IR signaling pathway. Cell proliferation studies revealed that PPY induced cell death in a dose-dependent manner. Expression levels of IGF-IR were decreased in MCF-7 cells by PPY in a dose-dependent manner. These results indicate that inhibition of the IGF-IR pathway is also involved in PPY induced proliferation of MCF-7 cells. In addition, these data demonstrated that PPY induces cell cycle arrest and activates apoptosis.

A new diterpene from Litsea cubeba fruits: structure elucidation and capability to induce apoptosis in HeLa cells

A new diterpene, identified as (+)-6-(4-hydroxy-4-methyl-2-pentenoyl)-4,6-dimethyl-5-(3-methyl-2-butenyl)-1,3-cyclohexadienecarbaldehyde (1, cubelin), was isolated from a methanol extract of Litsea cubeba fruits by normal phase column chromatography and purified by preparative HPLC. The structure elucidation was conducted by spectroscopic methods (UV, IR, ESI-TOF-MS, 1-D and 2-D NMR). Cubelin exhibited activity against HeLa cell viability and proliferation. The cells also exhibited changes in nuclear morphology which are hallmarks of apoptotic cell death. The presence of cleaved caspase-3/-7, caspase-8 and caspase-9 in the cubelin treated population indicated the potential of the compound to induce apoptosis in HeLa cells via both intrinsic and extrinsic pathways.

Hyperthermia generated with ferucarbotran (Resovist®) in an alternating magnetic field enhances cisplatin-induced apoptosis of cultured human oral cancer cells

Hyperthermia is a promising anti-cancer treatment in which the tissue temperature is increased to 42-45 °C, and which is often used in combination with chemotherapy or radiation therapy. Our aim in the present work was to examine the feasibility of combination therapy for oral cancer with cisplatin and hyperthermia generated with ferucarbotran (Resovist(®); superparamagnetic iron oxide) in an alternating magnetic field (AMF). First, we established that administration of ferucarbotran at the approved dosage for magnetic resonance imaging provides an iron concentration sufficient to increase the temperature to 42.5 °C upon exposure to AMF. Then, we examined the effect of cisplatin combined with ferucarbotran/AMF-induced hyperthermia on cultured human oral cancer cells (HSC-3 and OSC-19). Cisplatin alone induced apoptosis of cancer cells in a dose-dependent manner, as is well known. However, the combination of cisplatin with ferucarbotran/AMF was significantly more effective than cisplatin alone. This result suggests that it might be possible to reduce the clinically effective dosage of cisplatin by administering it in combination with ferucarbotran/AMF-induced hyperthermia, thereby potentially reducing the incidence of serious cisplatin-related side effects. Further work seems justified to evaluate simultaneous thermo-chemotherapy as a new approach to anticancer therapy.

β-elemene reverses the drug resistance of lung cancer A549/DDP cells via the mitochondrial apoptosis pathway

β-elemene (β-ELE) is a new anticancer drug extracted from Curcuma zedoaria Roscoe and has been widely used to treat malignant tumors. Recent studies have demonstrated that β-ELE reverses the drug resistance of tumor cells. To explore the possible mechanisms of action of β-ELE, we investigated its effects on cisplatin-resistant human lung adenocarcinoma A549/DDP cells. The effects of β-ELE on the growth of A549/DDP cells in vitro were determined by MTT assay. Apoptosis was assessed by fluorescence microscopy with Hoechst 33258 staining and flow cytometry with Annexin V-FITC/PI double staining. Mitochondrial membrane potential was assessed using JC-1 fluorescence probe and laser confocal scanning microscopy, and intracellular reactive oxygen species levels were measured by 2',7'-dichlorofluorescein-diacetate staining and flow cytometry. Cytosolic glutathione content was determined using GSH kits. The expression of cytochrome c, caspase-3, procaspase-3 and the Bcl-2 family proteins was assessed by western blotting. The results demonstrated that β-ELE inhibited the proliferation of A549/DDP cells in a time- and dose-dependent manner. Furthermore, β-ELE enhanced the sensitivity of A549/DDP cells to cisplatin and reversed the drug resistance of A549/DDP cells. Consistent with a role in activating apoptosis, β-ELE decreased mitochondrial membrane potential, increased intracellular reactive oxygen species concentration and decreased the cytoplasmic glutathione levels in a time- and dose-dependent manner. The combination of β-ELE and cisplatin enhanced the protein expression of cytochrome c, caspase-3 and Bad, and reduced protein levels of Bcl-2 and procaspase-3 in the A549/DDP lung cancer cells. These results define a pathway of procaspase‑3-β-ELE function that involves decreased mitochondrial membrane potential, leading to apoptosis triggered by the release of cytochrome c into the cytoplasm and the modulation of apoptosis-related genes. The reversal of drug resistance of the A549/DDP cell line by β-ELE may be derived from its effect in inducing apoptosis.

Evaluation of silicon nitride as a substrate for culture of PC12 cells: an interfacial model for functional studies in neurons

Silicon nitride is a biocompatible material that is currently used as an interfacial surface between cells and large-scale integration devices incorporating ion-sensitive field-effect transistor technology. Here, we investigated whether a poly-L-lysine coated silicon nitride surface is suitable for the culture of PC12 cells, which are widely used as a model for neural differentiation, and we characterized their interaction based on cell behavior when seeded on the tested material. The coated surface was first examined in terms of wettability and topography using contact angle measurements and atomic force microscopy and then, conditioned silicon nitride surface was used as the substrate for the study of PC12 cell culture properties. We found that coating silicon nitride with poly-L-lysine increased surface hydrophilicity and that exposing this coated surface to an extracellular aqueous environment gradually decreased its roughness. When PC12 cells were cultured on a coated silicon nitride surface, adhesion and spreading were facilitated, and the cells showed enhanced morphological differentiation compared to those cultured on a plastic culture dish. A bromodeoxyuridine assay demonstrated that, on the coated silicon nitride surface, higher proportions of cells left the cell cycle, remained in a quiescent state and had longer survival times. Therefore, our study of the interaction of the silicon nitride surface with PC12 cells provides important information for the production of devices that need to have optimal cell culture-supporting properties in order to be used in the study of neuronal functions.

In vitro and in vivo assessment of the biocompatibility of an Mg-6Z(n) alloy in the bile

There is a great clinical need for biodegradable bile duct stents. Biodegradable stents made of an Mg-6Zn alloy were investigated in both vivo animal experiment and in vitro cell experiments. During the in vivo experiments, blood biochemical tests were performed to determine serum magnesium, serum creatinine (CREA), blood urea nitro-gen (BUN), serum lipase (LPS), total bilirubin (TB) and glutamic-pyruvic transaminase (GPT) levels. Moreover, tissue samples of common bile duct (CBD), liver and kidney were taken for histological evaluation. In the in vitro experiments, primary mouse extrahepatic bile duct epithelial cells (MEBDECs) were isolated and cultured. Cytotoxicity testing was carried out using the MTT method. Flow cytometry analyses with propidium iodide staining were performed to evaluate the effect of Mg-6Zn alloy extracts on cell cycle. The in vivo experiments revealed no significant differences (P > 0.05) in serum magnesium, CREA, BUN, LPS, TB or GPT before and after the operation. Based on the HE results, hepatocytes, bile duct epithelial cells, renal glomerulus and renal tubule tissues did not present significant necrosis. In the in vitro experiments, the cell relative growth rate curve did not change significantly from 20 to 40 % extracts. In vitro experiments showed that 20-40 % Mg-6Zn extracts are bio-safe for MEBDECs. In vivo experiments showed that Mg-6Zn stents did not affect several important bio-chemical parameters or, harm the function or morphology of the CBD, kidney, pancreas and liver. Our data suggested that this Mg-6Zn alloy is a safe biocompatible material for CBD.

Resistance to cancer in amphibians: a role for apoptosis?

The rarity of spontaneous cancer in amphibians, and the difficulty of inducing cancer in these lower vertebrates, suggest that they possess an effective system for resistance to the development of cancer. The first part of this narrative presents evidence for cancer resistance in amphibians, and then a variety of studies designed to help understand the physiological basis for this resistance are reviewed. Here, our emphasis is on evidence with regard to the role that apoptosis might play.

β-Ionone derived chalcones as potent antiproliferative agents

A series of β-ionone derived chalcones were evaluated for cytotoxic activity against various human cancer cell lines using SRB dye assay. All the compounds displayed moderate to high cytotoxic effect against almost all the cancer cell lines. The results also revealed the effect of substituents of the aromatic ring on their inhibitory potential. In general, compounds bearing electron withdrawing groups such as nitro, fluoro, chloro and bromo showed more inhibitory potential than those bearing electron donating groups. The nitro substituted compound (7h) showed comparatively more inhibitory potential than other derivatives, therefore, it was further investigated for observing its effect on cell morphology in Chinese hamster ovary (CHO) cells by using phase contrast imaging, cell cycle analysis and annexin-FITC apoptosis assay. The treated cells exhibited the characteristics of apoptosis i.e. cell shrinkage, chromatin condensation and nuclear fragmentation, and induced the inhibition of cell proliferation by arresting the cells at G0 phase.

Cytotoxic effect of leaf essential oil of Lippia gracilis Schauer (Verbenaceae)

Medicinal plants are one of the most important sources of drugs used in the pharmaceutical industry. Among traditional medicinal plants, Lippia gracilis Schauer (Verbenaceae) had been used for several medicinal purposes in Brazilian northeastern. In this study, leaf essential oil (EO) of L. gracilis was prepared using hydrodistillation. Followed by GC-MS analysis, its composition was characterized by the presence of thymol (55.50%), as major constituent. The effects of EO on cell proliferation and apoptosis induction were investigated in HepG2 cells. Furthermore, mice bearing Sarcoma 180 tumor cells were used to confirm its in vivo effectiveness. EO and its constituents (thymol, p-cymene, γ-terpinene and myrcene) displayed cytotoxicity to different tumor cell lines. EO treatment caused G1 arrest in HepG2 cells accompanied by the induction of DNA fragmentation without affecting cell membrane integrity. Cell morphology consistent with apoptosis and a remarkable activation of caspase-3 were also observed, suggesting induction of caspase-dependent apoptotic cell death. In vivo antitumor study showed tumor growth inhibition rates of 38.5-41.9%. In conclusion, the tested essential oil of L. gracilis leaves, which has thymol as its major constituent, possesses significant in vitro and in vivo antitumor activity. These data suggest that leaf essential oil of L. gracilis is a potential medicinal resource.

MiR-26a regulates cell cycle and anoikis of human esophageal adenocarcinoma cells through Rb1-E2F1 signaling pathway

Resistance to anoikis, the subtype of apoptosis induced by lack of matrix adhesion, contributes to malignant transformation and development of metastasis. MicroRNAs play key regulatory roles in tumorigenesis and metastasis. In this study, we described that miR-26a, which is usually downregulated in tumor cells, is involved in the acquisition of anoikis-resistance of human esophageal adenocarcinoma (EA) cells. Results of qRT-PCR in clinical samples showed that downregulated miR-26a expression is related to tumorigenesis and metastasis of EA. In vitro experiments determined that miR-26a directly participates in the regulation of cell cycle and anoikis of human EA OE33 cells. Further, we identified that Rb1 is the direct functional target of miR-26a, and revealed that the reduction of miR-26a expression leads to increased Rb1 protein level and thus inhibits the function of E2F1, by which it influences the phenotypes of cell cycle and anoikis. The findings we reported here presented the evidence that miR-26a may be involved in regulation of anoikis-resistance of EA cells. Targeting miR-26a may provide a novel strategy to inhibit metastasis.

Pristimerin causes G1 arrest, induces apoptosis, and enhances the chemosensitivity to gemcitabine in pancreatic cancer cells

Despite rapid advances in chemotherapy and surgical resection strategies, pancreatic cancer remains the fourth leading cause of cancer related deaths in the United States with a 5-year survival rate of less than 5%. Therefore, novel therapeutic agents for the prevention and treatment of pancreatic cancer are urgently needed. The aim of this study was to investigate the effect of pristimerin, a quinonemethide triterpenoid compound isolated from Celastraceae and Hippocrateaceae, on inhibition of cell proliferation and induction of apoptosis in three pancreatic cancer cells, BxPC-3, PANC-1 and AsPC-1, in both monotherapy and in combination with gemcitabine. Treatment with pristimerin decreased the cell proliferation of all three pancreatic cancer cells in a dose- and time-dependent manner. Treatment of pancreatic cancer cells with pristimerin also resulted in G1-phase arrest which was strongly associated with a marked decrease in the level of cyclins (D1 and E) and cyclin-dependent kinases (cdk2, cdk4 and cdk6 ) with concomitant induction of WAF1/p21 and KIP1/p27. Pristimerin treatment also resulted in apoptotic cell death, cleavage of caspase-3, modulation in the expressions of Bcl-2 family proteins, inhibition of the translocation and DNA-binding activity of NF-κB. In addition, pristimerin potentiated the growth inhibition and apoptosis inducing effects of gemcitabine in all three pancreatic cancer cells, at least in part, by inhibiting constitutive as well as gemcitabine-induced activation of NF-κB in both its DNA-binding activity and transcriptional activity. Taken together, these data provide the first evidence that pristimerin has strong potential for development as a novel agent against pancreatic cancer.

Protein-based identification of quantitative trait loci associated with malignant transformation in two HER2+ cellular models of breast cancer

BACKGROUND

A contemporary view of the cancer genome reveals extensive rearrangement compared to normal cells. Yet how these genetic alterations translate into specific proteomic changes that underpin acquiring the hallmarks of cancer remains unresolved. The objectives of this study were to quantify alterations in protein expression in two HER2+ cellular models of breast cancer and to infer differentially regulated signaling pathways in these models associated with the hallmarks of cancer.

RESULTS

A proteomic workflow was used to identify proteins in two HER2 positive tumorigenic cell lines (BT474 and SKBR3) that were differentially expressed relative to a normal human mammary epithelial cell line (184A1). A total of 64 (BT474-184A1) and 69 (SKBR3-184A1) proteins were uniquely identified that were differentially expressed by at least 1.5-fold. Pathway inference tools were used to interpret these proteins in terms of functionally enriched pathways in the tumor cell lines. We observed "protein ubiquitination" and "apoptosis signaling" pathways were both enriched in the two breast cancer models while "IGF signaling" and "cell motility" pathways were enriched in BT474 and "amino acid metabolism" were enriched in the SKBR3 cell line.

CONCLUSION

While "protein ubiquitination" and "apoptosis signaling" pathways were common to both the cell lines, the observed patterns of protein expression suggest that the evasion of apoptosis in each tumorigenic cell line occurs via different mechanisms. Evidently, apoptosis is regulated in BT474 via down regulation of Bid and in SKBR3 via up regulation of Calpain-11 as compared to 184A1.

New insights into the mechanisms of green tea catechins in the chemoprevention of prostate cancer

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer deaths in American men. Its long latency, slow progression, and high incidence rate make prostate cancer ideal for targeted chemopreventative therapies. Therefore, chemoprevention studies and clinical trials are essential for reducing the burden of prostate cancer on society. Epidemiological studies suggest that tea consumption has protective effects against a variety of human cancers, including that of the prostate. Laboratory and clinical studies have demonstrated that green tea components, specifically the green tea catechin (GTC) epigallocatechin gallate, can induce apoptosis, suppress progression, and inhibit invasion and metastasis of prostate cancer. Multiple mechanisms are involved in the chemoprevention of prostate cancer with GTCs; understanding and refining models of fundamental molecular pathways by which GTCs modulate prostate carcinogenesis is essential to apply the utilization of green tea for the chemoprevention of prostate cancer in clinical settings. The objective of this article is to review and summarize the most current literature focusing on the major mechanisms of GTC chemopreventative action on prostate cancer from laboratory, in vitro, and in vivo studies, and clinical chemoprevention trials.

Therapeutic potential of c-Myc inhibition in the treatment of hypertrophic cardiomyopathy

Investigating the pathophysiological importance of the molecular and mechanical development of cardiomyopathy is critical to find new and broader means of protection against this disease that is increasing in prevalence and impact. The current available treatment options for cardiomyopathy mainly focus on treating symptoms and strive to make the patient more comfortable while preventing progression of disease and sudden death. The proto-oncogene c-Myc (Myc) has been shown to be increased in many different types of heart disease, including hypertrophic cardiomyopathy, before any signs of the disease are present. As the mechanisms of action and multiple pathways of dependent actions of Myc are being dissected by many research groups, inhibition of Myc is becoming an attractive paradigm for prevention and treatment of cardiomyopathy and heart failure. Elucidating the role Myc plays in the development, propagation and perpetuation of cardiomyopathy and heart failure will one day translate into potential therapeutics for cardiomyopathy.

Cytotoxic evaluation and induction of mitochondria-mediated apoptosis in human leukaemia HL-60 cells by Carissa spinarum stem isolate

Objective

To evaluate Carissa spinarum stem isolate for its anti-cancer therapeutic potential.

Methods

The n-butanol fraction of aqueous extract from Carissa spinarum stem was assessed for its cytotoxic and pro-apoptotic activity.

Key findings

We report for the first time the anti-cancer potential of C. spinarum stem aqueous extract (CSE) and its n-butanol fraction (CSF). Both inhibited cell proliferation of various human cancer cell lines in which leukaemia HL-60 cells treated with CSF showed maximum growth inhibition having an inhibitory concentration (IC50) value of 34.58 ± 0.91 µg/ml. In addition, CSF induced concentration-dependent apoptosis in HL-60 cells as measured by various end-points (e.g. Annexin V binding, DNA laddering, apoptotic body formation and an increase in hypodiploid subG0 DNA content). Moreover, persistent levels of reactive oxygen species caused translocation of Bax to mitochondria and Bcl-2 degradation, which led to loss of mitochondrial membrane potential and release of cytochrome c to the cytosol. These events were associated with significant activation of caspase-3, caspase-6 and caspase-9 leading to poly (ADP-ribose) polymerase cleavage.

Conclusion

All the above parameters revealed that CSF induced apoptosis through the mitochondrial dependent pathway in HL-60 cells.

Improving anticancer activities of Oplopanax horridus root bark extract by removing water-soluble components

O. horridus is used as a folk medicine by natives in the Northern Pacific coast of North America. This experiment studied the antiproliferative effects of the extract of O. horridus root bark and its fractions chromatographed from Dianion HP20 resin column with water, 30, 50, 70 and 100% ethanol on human breast cancer MCF-7 cells and non-small cell lung cancer (NSCLC) cells. The role of O. horridus in the cell cycle and apoptosis of MCF-7 cells was also investigated. The results showed that the 70% and 100% ethanol fractions demonstrated more potent antiproliferative effects than the total extract on both cell lines. The antiproliferative effects may result from the enrichment of active constituents detected by high performance liquid chromatography (HPLC). The IC(50) of the total extract, 50, 70, and 100% ethanol fractions for antiproliferation on MCF-7 cells were 248.4, 123.1, 44.0, and 31.5 microg/mL, respectively, and on NSCLC cells were 125.3, 271.1, 17.6, and 23.2 microg/mL, respectively. On the other hand, the water and 30% ethanol fractions significantly promoted cell proliferation on MCF-7 cells at concentrations > 100 microg/mL, suggesting that the hydrophilic fractions should be removed from the extract when used for cancer chemoprevention in order to achieve desirable activities. The effects of the total extract on cell cycle and apoptosis were similar to that of the 100% ethanol fraction because of the similarity of their chemical composition. At higher concentrations, the apoptotic effects of the 70% ethanol fraction are more significant. Data from this study suggested that the 70% and 100% ethanol fractions are active antiproliferative fractions and that induction of apoptosis is the mechanism involved in the antiproliferative effect observed.

Activation of caspases and poly (ADP-ribose) polymerase cleavage to induce apoptosis in leukemia HL-60 cells by Inula racemosa

Inula racemosa Hook.f. commonly known as Pushkarmula (Compositae) has been used as a traditional drug in India, China and Europe. In the present study, 95% ethanolic extract of roots and its fractions (n-hexane, chloroform, n-butanol and aqueous) were evaluated for in vitro cytotoxicity against cancer cell lines of colon, ovary, prostate, lung, CNS and leukemia. The n-hexane fraction containing alantolactone and isoalantolactone as its major constituents was further studied for its mode of action in HL-60 cells. The lowest IC(50) value of n-hexane fraction was 10.25 microg/ml for Colo-205, a colon cancer cell line whereas, 17.86 microg/ml was the highest IC(50) value observed against CNS cancer cell line SF-295. Further studies on HL-60 cells treated with n-hexane fraction at 10, 25 and 50 microg/ml for 6h, revealed that it induces apoptosis through intrinsic as well as extrinsic pathways by generating reactive oxygen species (ROS) intermediates. Mitochondrial dysfunction prompted the release of cytochrome c, translocation of pro-apoptotic protein (Bax), activation of caspase cascade, resulting in the cleavage of some specific substrates for caspase-3 such as poly (ADP-ribose) polymerase (PARP), which eventually leads to apoptosis. The results of present study strongly support further research and development of bioactive constituents from Inula racemosa as potential anticancer agent with possible therapeutic implication.

Circadian rhythm and its role in malignancy

Circadian rhythms are daily oscillations of multiple biological processes directed by endogenous clocks. The circadian timing system comprises peripheral oscillators located in most tissues of the body and a central pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Circadian genes and the proteins produced by these genes constitute the molecular components of the circadian oscillator which form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends beyond clock genes to involve various clock-controlled genes (CCGs) including various cell cycle genes. Aberrant expression of circadian clock genes could have important consequences on the transactivation of downstream targets that control the cell cycle and on the ability of cells to undergo apoptosis. This may lead to genomic instability and accelerated cellular proliferation potentially promoting carcinogenesis. Different lines of evidence in mice and humans suggest that cancer may be a circadian-related disorder. The genetic or functional disruption of the molecular circadian clock has been found in various cancers including breast, ovarian, endometrial, prostate and hematological cancers. The acquisition of current data in circadian clock mechanism may help chronotherapy, which takes into consideration the biological time to improve treatments by devising new therapeutic approaches for treating circadian-related disorders, especially cancer.

Recent advances on structure-informed drug discovery of cyclin-dependent kinase-2 inhibitors

Serine and threonine kinases play an important role in signal-transduction pathways. Within this kinase family, cyclin-dependent kinase (CDK)2 is an attractive target for oncology involved in cell cycle regulation. In recent years, kinase inhibition has become a major area for therapeutic involvement. As we discuss here, these efforts have resulted in a considerable increase in the number of available high-resolution structures of CDK2–inhibitor complexes. A large amount of structural-based and computational work has allowed the identification of novel chemical scaffolds and structural motifs to design potent CDK2 inhibitors. Of any kinase, CDK2 has the most structures available from the protein databank, averaging 22 new structures per year since 2002. A protein–ligand interaction fingerprint analysis of the available CDK2 protein–ligand complexes indicates that structural diversity is attainable from the structure-based design of CDK2 inhibitors. Since the first CDK2 structure was published in 1996, seven new chemical entities (NCEs) have been advanced to clinical stages. To date, only three of these NCEs have had their complexes published in the protein databank. This review summarizes the structurally informed efforts in the field of CDK2 inhibitor design.

Effects of carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone on the growth inhibition in human pulmonary adenocarcinoma Calu-6 cells

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) is an uncoupler of mitochondrial oxidative phosphorylation in eukaryotic cells. Here, we evaluated the in vitro effects of FCCP on the growth of Calu-6 lung cancer cells. FCCP inhibited the growth of Calu-6 cells with an IC(50) of approximately 6.64+/-1.84 microM at 72 h, as shown by MTT. DNA flow cytometric analysis indicated that FCCP induced G1 phase arrest below 20 microM of FCCP. Treatment with FCCP decreased the level of CDKs and cyclines in relation to G1 phase. In addition, FCCP not only increased the p27 level but also enhanced its binding with CDK4, which was associated with hypophosphorylation of Rb protein. While transfection of p27 siRNA inhibited G1 phase arrest in FCCP-treated cells, it did not enhance Rb phosphorylation. FCCP also efficiently induced apoptosis. The apoptotic process was accompanied with an increase in sub-G1 cells, annexin V staining cells, mitochondria membrane potential (MMP) loss and cleavage of PARP protein. All of the caspase inhibitors (caspase-3, -8, -9 and pan-caspase inhibitor) markedly rescued the Calu-6 cells from FCCP-induced cell death. However, knock down of p27 protein intensified FCCP-induced cell death. Moreover, FCCP induced the depletion of GSH content in Calu-6 cells, which was prevented by all of the caspase inhibitors. In summary, our results demonstrated that FCCP inhibits the growth of Calu-6 cells in vitro. The growth inhibitory effect of FCCP might be mediated by cell cycle arrest and apoptosis via decrease of CDKs and caspase activation, respectively. These findings now provide a better elucidation of the mechanisms involved in FCCP-induced growth inhibition in lung cancer.

Cell cycle and apoptosis regulatory gene expression in the bone marrow of patients with de novo myelodysplastic syndromes (MDS)

Deregulation of cell cycle and apoptosis pathways are known contributors to the pathogenesis of myelodysplastic syndromes (MDS). However, the underlying mechanisms are not fully clarified. The aim of our study was to examine mRNA expression levels of cell cycle and apoptosis regulatory genes, as well as the percentage of apoptotic and S phase cells and to correlate the findings with clinical characteristics and prognosis. Sixty patients with MDS, classified according to FAB (17 RA, five RARS, 19 RAEB, nine RAEBT, ten CMML) and WHO (ten RA, three RARS, seven RCMD, two RCMD-RS, 11 RAEBI, eight RAEBII, ten CMML, and nine AML) were included in the study. We found increased expression of anti-apoptotic bclxL and mcl1 genes and decreased expression of p21 gene in MDS patients. Moreover, we found increased expression of anti-apoptotic mcl1 gene in patients with higher than Intermediate-1 IPSS group. Multivariate analysis confirmed that combined expression of apoptotic caspases 8, 3, 6, 5, 2, 7, and Granzyme B was decreased in MDS patients. Regarding cell cycle regulatory genes expression, we demonstrated increased expression of cyclin D1 in patients with CMML Increased combined expression of cyclins B, C, D1, and D2 was found in patients with cytogenetic abnormalities. The two pathways seem to be interconnected as shown by the positive correlation between CDKs 1, 2, 4, p21 and the level of apoptosis and positive correlation between apoptotic caspase 3 expression and the percentage of S phase cells. In conclusion, our study showed altered expression of genes involved in apoptosis and cell cycle in MDS and increased expression of cyclin D1 in patients with CMML.

Selenium as an essential micronutrient: roles in cell cycle and apoptosis

Selenium is an essential trace element for humans and animals, and selenium deficiency is associated with several disease conditions such as immune impairment. In addition, selenium intakes that are greater than the recommended daily allowance (RDA) appear to protect against certain types of cancers. In humans and animals, cell proliferation and death must be regulated to maintain tissue homeostasis, and it has been well documented that numerous human diseases are directly related to the control of cell cycle progression and apoptosis. Thus, the elucidation of the mechanisms by which selenium regulates the cell cycle and apoptosis can lead to a better understanding of the nature of selenium's essentiality and its role in disease prevention. This article reviews the status of knowledge concerning the effect of selenium on cell cycle and apoptosis.

The story of human cytomegalovirus and cancer: increasing evidence and open questions

Although human cytomegalovirus (HCMV) is generally not regarded to be an oncogenic virus, HCMV infection has been implicated in malignant diseases from different cancer entities. On the basis of our experimental findings, we developed the concept of "oncomodulation" to better explain the role of HCMV in cancer. Oncomodulation means that HCMV infects tumor cells and increases their malignancy. By this concept, HCMV was proposed to be a therapeutic target in a fraction of cancer patients. However, the clinical relevance of HCMV-induced oncomodulation remains to be clarified. One central question that has to be definitively answered is if HCMV establishes persistent virus replication in tumor cells or not. In our eyes, recent clinical findings from different groups in glioblastoma patients and especially the detection of a correlation between the numbers of HCMV-infected glioblastoma cells and tumor stage (malignancy) strongly increase the evidence that HCMV may exert oncomodulatory effects. Here, we summarize the currently available knowledge about the molecular mechanisms that may contribute to oncomodulation by HCMV as well as the clinical findings that suggest that a fraction of tumors from different entities is indeed infected with HCMV.

Post-translational modification of cyclin A1 is associated with staurosporine and TNFalpha induced apoptosis in leukemic cells

Understanding of molecular mechanisms underlying the effects of cell cycle proteins in response to the chemotherapeutic agents is of great importance for improving the efficacy of targeted therapeutics and overcoming resistance to chemotherapeutic agents. Staurosporine and tumor necrosis factor alpha (TNFalpha) are the therapeutic agents that inhibit tumor cell growth by inducing cell death. Staurosporine induces apoptosis through the intrinsic pathway, while TNFalpha trigger the cell death via the extrinsic apoptotic pathway. We have previously demonstrated that the cell cycle regulatory protein, cyclin A1 played an important role in the development of acute myeloid leukemia (AML), and cyclin A1 expression correlated with disease characteristics and patient outcome in leukemia. However, it remains unknown how cyclin A1 expression is regulated in leukemic cells treated with the therapeutic agents. Here, we demonstrate that cyclin A1 protein is regulated by proteasome-mediated ubiquitination and degradation in untreated U-937 cells. Interestingly, ubiquitination- and proteasomal-mediated degradation of cyclin A1 is prevented in cells treated with staurosporine or TNFalpha. Induction of apoptosis in U-937 cells by staurosporine or TNFalpha resulted in an increase in cyclin A1 protein expression, which correlated well with cyclin A1 protein modification and the activation of caspase-3. Blocking caspases activity by Z-VAD-FMK had no effect on the increased cyclin A1 expression, suggesting that cyclin A1 might be regulated by caspase-3 independent pathways. We further propose that CDC25C may be associated with cyclin A1 protein modification in response to staurosporine or TNFalpha treatment. Our results suggest that cyclin A1 protein is stabilized via post-transcriptional modification in response to apoptosis induced by staurosporine or TNFalpha.