Cyclin B3 is a mitotic cyclin that promotes the metaphase-anaphase transition.

The timing mechanism for mitotic progression is still poorly understood. The spindle assembly checkpoint (SAC), whose reversal upon chromosome alignment is thought to time anaphase [1-3], is functional during the rapid mitotic cycles of the Drosophila embryo; but its genetic inactivation had no consequence on the timing of the early mitoses. Mitotic cyclins-Cyclin A, Cyclin B, and Cyclin B3-influence mitotic progression and are degraded in a stereotyped sequence [4-11]. RNAi knockdown of Cyclins A and B resulted in a Cyclin B3-only mitosis in which anaphase initiated prior to chromosome alignment. Furthermore, in such a Cyclin B3-only mitosis, colchicine-induced SAC activation failed to block Cyclin B3 destruction, chromosome decondensation, or nuclear membrane re-assembly. Injection of Cyclin B proteins restored the ability of SAC to prevent Cyclin B3 destruction. Thus, SAC function depends on particular cyclin types. Changing Cyclin B3 levels showed that it accelerated progress to anaphase, even in the absence of SAC function. The impact of Cyclin B3 on anaphase initiation appeared to decline with developmental progress. Our results show that different cyclin types affect anaphase timing differently in the early embryonic divisions. The early-destroyed cyclins-Cyclins A and B-restrain anaphase-promoting complex/cyclosome (APC/C) function, whereas the late-destroyed cyclin, Cyclin B3, stimulates function. We propose that the destruction schedule of cyclin types guides mitotic exit by affecting both Cdk1 and APC/C, whose activities change as each cyclin type is lost.

Natural borneol enhances bisdemethoxycurcumin-induced cell cycle arrest in the G2/M phase through up-regulation of intracellular ROS in HepG2 cells.

Bisdemethoxycurcumin (BDCur) has been found widely in foods such as cheese, butter, etc., and in curry (powder) as a spice. It has been reported to possess anticancer activity. However, its poor absorption limited its application. Natural borneol (NB) has been used as a promoter of drug absorption and widely used in candies, beverages, baked goods, chewing gum and other foods. Thus, we investigated whether NB could potentiate the cellular uptake of BDCur, and elucidated the molecular mechanisms of their combined inhibitory effects on HepG2 cells. Our results demonstrate that NB significantly enhanced the cellular uptake of BDCur. Induction of cell cycle arrest in HepG2 cells by NB and BDCur in combination was evidenced by accumulation of the G2/M cell population. Further investigation on the molecular mechanism showed that NB and BDCur in combination resulted in a significant decrease in the expression level of Cdc2 and cyclin B. Moreover, studies also found that ROS acted as an upstream mediator in NB/BDCur-induced HepG2 cell growth inhibition and led to DNA damage with up-regulation of the expression level of phosphorylated ATM and p53. Our findings suggest that the strategy of using NB and BDCur in combination may have promising potential applications in cancer chemoprevention.

Delaying mitotic exit downregulates FLIP expression and strongly sensitizes tumor cells to TRAIL.

Many of the current antitumor therapeutic strategies are based on the perturbation of the cell cycle, especially during mitosis. Antimitotic drugs trigger mitotic checkpoint activation, mitotic arrest and eventually cell death. However, mitotic slippage represents a major mechanism of resistance to these treatments. In an attempt to circumvent the process of slippage, targeting mitotic exit has been proposed as a better strategy to kill tumor cells. In this study, we show that treatments that induce mitotic checkpoint activation and mitotic arrest downregulate FLICE-like inhibitory protein (FLIP) levels and sensitize several tumor cell lines to TRAIL (tumor necrosis factor-related apoptosis-inducing ligand)-induced apoptosis. Interestingly, we also demonstrate that in absence of mitotic checkpoint activation, mitotic arrest induced either by Cdc20 knockdown or overexpression of nondegradable cyclin B is sufficient to induce both FLIP downregulation and sensitivity to TRAIL. In summary, our data suggest that a combination of antimitotic drugs targeting cyclin B degradation and TRAIL might prevent mitotic slippage and allow tumor cells to reach the threshold for apoptosis induction, thereby facilitating tumor suppression.

Combined therapeutic potential of nuclear receptors with receptor tyrosine kinase inhibitors in lung cancer.

Cancer heterogeneity is a big hurdle in achieving complete cancer treatment, which has led to the emergence of combinational therapy. In this study, we investigated the potential use of nuclear receptor (NR) ligands for combinational therapy with other anti-cancer drugs. We first profiled all 48 NRs and 48 biological anti-cancer targets in four pairs of lung cell lines, where each pair was obtained from the same patient. Two sets of cell lines were normal and the corresponding tumor cell lines while the other two sets consisted of primary versus metastatic tumor cell lines. Analysis of the expression profile revealed 11 NRs and 15 cancer targets from the two pairs of normal versus tumor cell lines, and 9 NRs and 9 cancer targets from the primary versus metastatic tumor cell lines had distinct expression patterns in each category. Finally, the evaluation of nuclear receptor ligand T0901317 for liver X receptor (LXR) demonstrated its combined therapeutic potential with tyrosine kinase inhibitors. The combined treatment of cMET inhibitor PHA665752 or EGFR inhibitor gefitinib with T0901317 showed additive growth inhibition in both H2073 and H1993 cells. Mechanistically, the combined treatment suppressed cell cycle progression by inhibiting cyclinD1 and cyclinB expression. Taken together, this study provides insight into the potential use of NR ligands in combined therapeutics with other biological anti-cancer drugs.

Differential expression of miR-195 in esophageal squamous cell carcinoma and miR-195 expression inhibits tumor cell proliferation and invasion by targeting of Cdc42.

MicroRNAs (miRNA) have played an important role in carcinogenesis. In this study, Agilent miRNA microarray was used to identify differentially expressed miRNAs in esophageal squamous cell carcinoma (ESCC) tissues and miR-195 was downregulated in ESCC compared with normal esophageal tissues. Moreover, Cdc42 was confirmed as target gene of miR-195. Ectopic expression of miR-195 in ESCC cells significantly downregulated Cdc42 by directly binding its 3' untranslated regions, and induced G1 cell cycle arrest, leading to a significant decrease in cell growth, migration, and invasion in vitro. Therefore, our findings demonstrated that miR-195 may act as a tumor suppressor in ESCC by targeting Cdc42.

Natural aristolactams and aporphine alkaloids as inhibitors of CDK1/cyclin B and DYRK1A.

In an effort to find potent inhibitors of the protein kinases DYRK1A and CDK1/Cyclin B, a systematic in vitro evaluation of 2,500 plant extracts from New Caledonia and French Guyana was performed. Some extracts were found to strongly inhibit the activity of these kinases. Four aristolactams and one lignan were purified from the ethyl acetate extracts of Oxandra asbeckii and Goniothalamus dumontetii, and eleven aporphine alkaloids were isolated from the alkaloid extracts of Siparuna pachyantha, S. decipiens, S. guianensis and S. poeppigii. Among these compounds, velutinam, aristolactam AIIIA and medioresinol showed submicromolar IC50 values on DYRK1A.

Jaceosidin, isolated from dietary mugwort (Artemisia princeps), induces G2/M cell cycle arrest by inactivating cdc25C-cdc2 via ATM-Chk1/2 activation.

Jaceosidin, a flavonoid derived from Artemisia princeps (Japanese mugwort), has been shown to inhibit the growth of several human cancer cells, However, the exact mechanism for the cytotoxic effect of jaceosidin is not completely understood. In this study, we investigated the molecular mechanism involved in the antiproliferative effect of jaceosidin in human endometrial cancer cells. We demonstrated that jaceosidin is a more potent inhibitor of cell growth than cisplatin in human endometrial cancer cells. In contrast, jaceosidin-induced cytotoxicity in normal endometrial cells was lower than that observed for cisplatin. Jaceosidin induced G2/M phase cell cycle arrest and modulated the levels of cyclin B and p-Cdc2 in Hec1A cells. Knockdown of p21 using specific siRNAs partially abrogated jaceosidin-induced cell growth inhibition. Additional mechanistic studies revealed that jaceosidin treatment resulted in an increase in phosphorylation of Cdc25C and ATM-Chk1/2. Ku55933, an ATM inhibitor, reversed jaceosidin-induced cell growth inhibition, in part. Moreover, jaceosidin treatment resulted in phosphorylation of ERK, and pretreatment with the ERK inhibitor, PD98059, attenuated cell growth inhibition by jaceosidin. These data suggest that jaceosidin, isolated from Japanese mugwort, modulates the ERK/ATM/Chk1/2 pathway, leading to inactivation of the Cdc2-cyclin B1 complex, followed by G2/M cell cycle arrest in endometrial cancer cells.

Inducing "cytokinesis" without mitosis in unfertilized Drosophila eggs.

Selection of the cleavage plane during cytokinesis in dividing cells is linked to the position of the mitotic spindle. A major player in cleavage plane positioning is believed to be the anaphase central spindle and its associated signaling complex called centralspindlin, composed of MgcRacGap and MKLP1. Centralspindlin has the capacity to induce furrowing of the cell cortex by promoting the localized activation of RhoA, which in turn promotes assembly of the contractile ring. We have found a way to induce a cytokinesis-like process in unfertilized Drosophila eggs and very early embryos, when spindle structures are few and located far from invaginating egg cortex. The simple injection of a small molecule inhibitor of Cdk1/Cyclin B (either Roscovitin or RO3306) is sufficient to promote membrane invagination near the site of injection. The furrow generated is in many respects similar to a classical cleavage furrow. Actin, myosin, anillin and MKLP1 are all associated with the forming furrow, which in some cases can entirely circumscribe the unfertilized egg. A similar furrow can also be generated by the localized injection of constitutively active RhoA protein, suggesting that Cdk1 is normally an upstream inhibitor of RhoA activation. We show further that this process apparently is not associated with microtubules. Since simple localized inhibition of Cdk1 is sufficient to induce a furrow, we suggest that in real cytokinesis in normal cells, the localized downregulation of Cdk1 activity at the metaphase-anaphase transition may contribute, along with the spindle, to the positioning of the cleavage furrow.

Arsenic trioxide induces G2/M arrest in hepatocellular carcinoma cells by increasing the tumor suppressor PTEN expression.

Arsenic trioxide (As(2)O(3)), an effective agent against acute promyelocytic leukemia, has been reported to inhibit the viability of solid tumors cell lines recently. The detailed molecular mechanism underlying the As(2)O(3)-induced inactivation of the cdc2 and possible functional role of PTEN in the observed G2/M arrest has yet to be elucidated. Here, we assessed the role of PTEN in regulation of As(2)O(3)-mediated G2/M cell cycle arrest in Hepatocellular carcinoma cell lines (HepG2 and SMMC7721). After 24 h following treatment, As(2)O(3) induced a concentration-dependent accumulation of cells in the G2/M phase of the cell cycle. The sustained G2/M arrest by As(2)O(3) is associated with decreased cdc2 protein and increased phospho-cdc2(Tyr15). As(2)O(3) treatment increased Wee1 levels and decreased phospho-Wee1(642). Moreover, As(2)O(3) substantially decreased the Ser473 and Thr308 phosphorylation of Akt and upregulated PTEN expression. Downregulation of PTEN by siRNA in As(2)O(3) -treated cells increased phospho-Wee1(Ser642) while decreased phospho-cdc2(Tyr15), resulting in decreased the G2/M cell cycle arrest. Therefore, induction of G2/M cell cycle arrest by As(2)O(3) involved upregulation of PTEN.

Phosphorylation and ubiquitination of dynamin-related proteins (AtDRP3A/3B) synergically regulate mitochondrial proliferation during mitosis.

The balance between mitochondrial fission and fusion is disrupted during mitosis, but the mechanism governing this phenomenon in plant cells remains enigmatic. Here, we used mitochondrial matrix-localized Kaede protein (mt-Kaede) to analyze the dynamics of mitochondrial fission in BY-2 suspension cells. Analysis of the photoactivatable fluorescence of mt-Kaede suggested that the fission process is dominant during mitosis. This finding was confirmed by an electron microscopic analysis of the size distribution of mitochondria in BY-2 suspension cells at various stages. Cellular proteins interacting with Myc-tagged dynamin-related protein 3A/3B (AtDRP3A and AtDRP3B) were immunoprecipitated with anti-Myc antibody-conjugated beads and subsequently identified by microcapillary liquid chromatography-quadrupole time-of-flight mass spectrometry (CapLC Q-TOF) MS/MS. The identified proteins were broadly associated with cytoskeletal (microtubular), phosphorylation, or ubiquitination functions. Mitotic phosphorylation of AtDRP3A/AtDRP3B and mitochondrial fission at metaphase were inhibited by treatment of the cells with a CdkB/cyclin B inhibitor or a serine/threonine protein kinase inhibitor. The fate of AtDRP3A/3B during the cell cycle was followed by time-lapse imaging of the fluorescence of Dendra2-tagged AtDRP3A/3B after green-to-red photoconversion; this experiment showed that AtDRP3A/3B is partially degraded during interphase. Additionally, we found that microtubules are involved in mitochondrial fission during mitosis, and that mitochondria movement to daughter cell was limited as early as metaphase. Taken together, these findings suggest that mitotic phosphorylation of AtDRP3A/3B promotes mitochondrial fission during plant cell mitosis, and that AtDRP3A/3B is partially degraded at interphase, providing mechanistic insight into the mitochondrial morphological changes associated with cell-cycle transitions in BY-2 suspension cells.

Sic1 plays a role in timing and oscillatory behaviour of B-type cyclins.

Budding yeast cell cycle oscillates between states of low and high cyclin-dependent kinase activity, driven by association of Cdk1 with B-type (Clb) cyclins. Various Cdk1-Clb complexes are activated and inactivated in a fixed, temporally regulated sequence, inducing the behaviour known as "waves of cyclins". The transition from low to high Clb activity is triggered by degradation of Sic1, the inhibitor of Cdk1-Clb complexes, at the entry to S phase. The G(1) phase is characterized by low Clb activity and high Sic1 levels. High Clb activity and Sic1 proteolysis are found from the beginning of the S phase until the end of mitosis. The mechanism regulating the appearance on schedule of Cdk1-Clb complexes is currently unknown. Here, we analyse oscillations of Clbs, focusing on the role of their inhibitor Sic1. We compare mathematical networks differing in interactions that Sic1 may establish with Cdk1-Clb complexes. Our analysis suggests that the wave-like cyclins pattern derives from the binding of Sic1 to all Clb pairs rather than from Clb degradation. These predictions are experimentally validated, showing that Sic1 indeed interacts and coexists in time with Clbs. Intriguingly, a sic1Δ strain looses cell cycle-regulated periodicity of Clbs, which is observed in the wild type, whether a SIC1-0P strain delays the formation of Clb waves. Our results highlight an additional role for Sic1 in regulating Cdk1-Clb complexes, coordinating their appearance.

Functions of the mitotic B-type cyclins CLB1, CLB2, and CLB3 at mitotic exit antagonized by the CDC14 phosphatase.

In the budding yeast Saccharomyces cerevisiae, cell cycle progression and cytokinesis at mitotic exit are proposed to be linked by CDC14 phosphatase antagonizing the function of mitotic B-type cyclin (CLBs). We have isolated a temperature-sensitive mutant, cdc14(A280V), with a mutation in the conserved phosphatase domain. Prolonged arrest in the cdc14(A280V) mutant partially uncoupled cell cycle progression from the completion of cytokinesis as measured by bud re-emergence, in the form of elongated apical projections, and DNA re-replication. In contrast to previous mitotic exit mutants, cdc14(A280V) mutants displayed a strong bias for the first apical projection to form in the mother cell body. Using cdc14(A280V) mutant phenotypes, the functions of the B-type cyclins at mitotic exit were investigated. The preference in mother-daughter apical projection formation was observed to be independent of any individual CLB function. However, cdc14(A280V)clb1Δ cells displayed a pronounced increase in apical projections, while cdc14(A280V)clb3Δ cells were observed to form round cellular chains. While cdc14(A280V) cells arrested at mitotic exit, both cdc14(A280V)clb1Δ and cdc14(A280V)clb3Δ cells completed cytokinesis, but failed cell separation. cdc14(A280V)clb2Δ cells displayed a defect in actin ring assembly. These observations differentiate the functions of CLB1, CLB2, and CLB3 at mitotic exit, and are consistent with the hypothesis that CLB activities are antagonized by the CDC14 phosphatase in order to couple cell cycle progression with cytokinesis at mitotic exit.

NCPMF-60 induces G2/M cell cycle arrest and apoptosis in human hepatocellular carcinoma HepG2 cells.

We recently established that NCPMF-60, a newly synthesized flavonoid, is an active cytotoxic component. The molecular mechanisms by which NCPMF-60 exerts its cytotoxic activity are currently unknown. In this study, we show that NCPMF-60 induces G2/M phase arrest and apoptosis in human hepatocellular carcinoma HepG2 cells. After treatment of HepG2 cells with NCPMF-60, cell cycle-related proteins, such as cyclin B1, cyclin H, CDK7, and p-CDK1 (Thr161), were downregulated, whereas p21 and p-CDK1 (Thr14/Tyr15) were upregulated. The activity of CDK1/cyclinB complex was also inhibited by NCPMF-60. In addition, we observed poly(ADP-ribose) polymerase cleavage and activation of caspase 3 and caspase 9. The expression ratio of Bax/Bcl-2 was increased in the treated cells, in which Bax was also upregulated. We also found that the expression of p53 and its phosphorylation at Ser15 accumulated after the treatment of NCPMF-60. Moreover, upregulation of p21, p53-upregulated modifier of apoptosis, and Bax, three p53-target gene products, and the downregulation of Bcl-2 and MDM2, were observed in NCPMF-60-treated cells. However, p53 is not the only regulator in the stimulation of NCPMF-60 on p21 transcriptional level and posttranscriptional level. These results suggested that NCPMF-60 indeed activated the p53 pathway, which may contribute to its induction of cell cycle arrest and apoptosis in HepG2 cells. Collectively, our findings show that cell cycle arrest and apoptosis induced by NCPMF-60 was associated with the activation of p53 pathway and the inhibition of CDK-activating kinase activity in HepG2 cells.

Bortezomib potentially inhibits cellular growth of vascular endothelial cells through suppression of G2/M transition.

Bortezomib, a selective 26S proteasome inhibitor, has shown clinical benefits against refractory multiple myeloma. The indirect anti-angiogenic activity of bortezomib has been widely recognized; however, the growth-inhibitory mechanism of bortezomib on vascular endothelial cells remains unclear, especially on the cell cycle. Here, we showed that bortezomib (2 nM of the IC(50) value) potently inhibited the cellular growth of human umbilical vascular endothelial cells (HUVECs) via a vascular endothelial growth factor receptor (VEGFR)-independent mechanism resulting in the induction of apoptosis. Bortezomib significantly increased the vascular permeability of HUVECs, whereas a VEGFR-2 tyrosine kinase inhibitor decreased it. Interestingly, a cell cycle analysis using flow cytometry, the immunostaining of phospho-histone H3, and Giemsa staining revealed that bortezomib suppressed the G2/M transition of HUVECs, whereas the mitotic inhibitor paclitaxel induced M-phase accumulation. A further analysis of cell cycle-related proteins revealed that bortezomib increased the expression levels of cyclin B1, the cdc2/cyclin B complex, and the phosphorylation of all T14, Y15, and T161 residues on cdc2. Bortezomib also increased the ubiquitination of cyclin B1 and wee1, but inhibited the kinase activity of the cdc2/cyclin B complex. These protein modifications support the concept that bortezomib suppresses the G2/M transition, rather than causing M-phase arrest. In conclusion, we demonstrated that bortezomib potently inhibits cell growth by suppressing the G2/M transition, modifying G2/M-phase-related cycle regulators, and increasing the vascular permeability of vascular endothelial cells. Our findings reveal a cell cycle-related mode of action and strongly suggest that bortezomib exerts an additional unique vascular disrupting effect as a vascular targeting drug.

Suberoylanilide hydroxamic acid (SAHA) potentiates paclitaxel-induced apoptosis in ovarian cancer cell lines.

OBJECTIVES: To determine if SAHA, a histone deacetylase inhibitor, decreases ovarian cancer cell viability when combined with paclitaxel in vitro, and to explore molecular alterations of combined paclitaxel+SAHA treatment. METHODS: SKOV3 and Hey ovarian cancer cell lines were treated for 24 h with paclitaxel, then re-treated with SAHA or paclitaxel for an additional 48 h. Protein extracts were prepared at 48 h for western blot analysis. Cell viability was assessed at 72 h using the ApoAlert Annexin V Apoptosis Kit. RESULTS: SAHA causes G1 and G2 cell cycle arrest in ovarian cancer cell lines. Cell viability was significantly reduced by combined paclitaxel+SAHA treatment. In Hey cells, viability was reduced to 67% with paclitaxel, and to 48% with paclitaxel+SAHA (p<0.001). In the SKOV3 cell line, viability was reduced to 70% with continuous paclitaxel treatment, and was further reduced to 57% in the combined treatment group (p<0.05). Increased PARP cleavage was noted in the paclitaxel+SAHA groups. SAHA increased expression of p21cip1/waf1 and p27Kip1, down regulated cyclins A and B, and suppressed CDK1. Paclitaxel induced expression of survivin, an inhibitor of apoptosis protein, was reduced to baseline control levels with the addition of SAHA. The pro-apoptotic protein, Bad, was also increased with SAHA. CONCLUSIONS: Paclitaxel+SAHA reduces cell viability in excess of either agent alone in ovarian cancer cell lines. Cell death is mediated via several mechanisms including G1/G2 arrest from CDK1 downregulation, inhibition of paclitaxel-induced survivin accumulation, and from increased Bad expression.

Targeting cyclin B1 through peptide-based delivery of siRNA prevents tumour growth.

The development of short interfering RNA (siRNA), has provided great hope for therapeutic targeting of specific genes responsible for pathological disorders. However, the poor cellular uptake and bioavailability of siRNA remain a major obstacle to their clinical development and most strategies that propose to improve siRNA delivery remain limited for in vivo applications. In this study, we report a novel peptide-based approach, MPG-8 an improved variant of the amphipathic peptide carrier MPG, that forms nanoparticles with siRNA and promotes their efficient delivery into primary cell lines and in vivo upon intra-tumoral injection. Moreover, we show that functionalization of this carrier with cholesterol significantly improves tissue distribution and stability of siRNA in vivo, thereby enhancing the efficiency of this technology for systemic administration following intravenous injection without triggering any non-specific inflammatory response. We have validated the therapeutic potential of this strategy for cancer treatment by targeting cyclin B1 in mouse tumour models, and demonstrate that tumour growth is compromised. The robustness of the biological response achieved through this approach, infers that MPG 8-based technology holds a strong promise for therapeutic administration of siRNA.

N-(indazolyl)benzamido derivatives as CDK1 inhibitors: design, synthesis, biological activity, and molecular docking studies.

A series of N-1H-indazole-1-carboxamides has been synthesized and their effects on both CDK1/cyclin B and the K-562 (human chronic myelogenus leukemia) cell line were evaluated. Using a computational model, we have observed that all the most active compounds 9e, f, i-n exhibited the same binding mode of purvanalol A in the ATP-binding cleft. Although they were able to moderately inhibit the leukemic cell line K-562 and to show inhibitory activity against the Cdc2-Cyclin B kinase in the low micromolar range, they turned out to be non-cytotoxic against HuDe (IZSL) primary cell cultures from human derm. These preliminary results are quite encouraging in view of the low toxicity demonstrated by the above-mentioned compounds.

Emodin induces apoptosis of human tongue squamous cancer SCC-4 cells through reactive oxygen species and mitochondria-dependent pathways.

Emodin was isolated from Rheum palmatum L. and exhibits an anticancer effect on human cancer cell lines, however, the molecular mechanisms of emodin-mediated apoptosis in human tongue cancer cells have not been fully investigated. In this study, treatment of human tongue cancer SCC-4 cells with various concentrations of emodin led to G2/M arrest through promoted p21 and Chk2 expression but inhibited cyclin B1 and cdc2; it also induced apoptosis through the pronounced release of cytochrome c from mitochondria and activations of caspase-9 and caspase-3. These events were accompanied by the generation of reactive oxygen species (ROS), disruption of mitochondrial membrane potential (delta psi(m)) and a decrease in the ratio of mitochondrial Bcl-2 and Bax content; emodin also promoted the levels of GADD153 and GRP78. The free radical scavenger N-acetylcysteine and caspase inhibitors markedly blocked emodin-induced apoptosis. Taken together, these findings suggest that emodin mediated oxidative injury (DNA damage) based on ROS production and ER stress based on the levels of GADD153 and GRP78 that acts as an early and upstream change in the cell death cascade to caspase- and mitochondria-dependent signaling pathways, triggers mitochondrial dysfunction from Bcl-2 and Bax modulation, mitochondrial cytochrome c release and caspase activation, consequently leading to apoptosis in SCC-4 cells.

Synthesis and biological evaluation of novel symmetry bis-enediynes.

A series of acyclic symmetry bis-enediynes have been synthesized successfully and their bioactivities were evaluated. Among them, 1,6-bis(4-((2-(pyridin-2-ylethynyl)phenyl)ethynyl)phenoxy)hexane 8g showed good inhibition activity against the CCRF-CEM (GI(50)=0.04 microM) and HL-60 (GI(50)=0.09 microM) cell lines of human leukemia. The cell cycle analysis shows that compound 8g arrests cell cycle via inhibiting Cyclin A and Cyclin B expressions in low concentration and induces a significant apoptosis progress in high concentration.

EBV-encoded LMP1 regulates Op18/stathmin signaling pathway by cdc2 mediation in nasopharyngeal carcinoma cells.

Oncoprotein 18/stathmin (Op18/stathmin) plays a crucial role in maintaining cell biological characteristics by regulating microtubule dynamics, especially entry into mitosis; phosphorylated Op18/stathmin promotes microtubule polymerization to form the mitotic spindle, which is essential for chromosome segregation and cell division. Cdc2 is a critical kinase in starting M phase events in cell-cycle progression and is a positive regulator of the cell cycle. Latent membrane protein 1 (LMP1) is an Epstein-Barr virus (EBV)-encoded oncogenic protein that is able to induce carcinogenesis via various signaling pathways. This study focused on regulation by LMP1 of Op18/stathmin signaling in nasopharyngeal carcinoma (NPC) cells and showed that LMP1 regulates Op18/stathmin signaling through cdc2 mediation, LMP1 upregulates cdc2 kinase activity, and Op18/stathmin phosphorylation promotes the interaction of cdc2 with Op18/stathmin and microtubule polymerization during mitosis, and inhibition of LMP1 expression attenuates the interaction of cdc2 and Op18/stathmin and promotes microtubule depolymerization. These results reveal a new pathway via which LMP1 regulates Op18/stathmin signaling by cdc2 mediation; this new signaling pathway not only perfects the LMP1 regulation network but also elucidates the molecular mechanism of LMP1 that leads to carcinogenesis.