G2-M Phase Transition Research Articles

Cell-Cycle-Specific Autoencoding Improves Cluster Analysis of Cycling Cardiomyocytes.

Our previous analyses of cardiomyocyte single-nucleus RNA sequencing (snRNAseq) data from the hearts of fetal pigs and pigs that underwent apical resection surgery on postnatal day (P) 1 (ARP1), myocardial infarction (MI) surgery on P28 (MIP28), both ARP1 and MIP28 (ARP1MIP28), or controls (no surgical procedure or CTL) identified 10 cardiomyocyte subpopulations (clusters), one of which appeared to be primed to proliferate in response to MI. However, the clusters composed of primarily proliferating cardiomyocytes still contained noncycling cells, and we were unable to distinguish between cardiomyocytes in different phases of the cell cycle. Here, we improved the precision of our assessments by conducting similar analyses with snRNAseq data for only the 1646 genes included under the Gene Ontology term "cell cycle." Two cardiac snRNAseq datasets, one from mice (GEO dataset number GSE130699) and one from pigs (GEO dataset number GSE185289), were evaluated via our cell-cycle-specific analytical pipeline. Cycling cells were identified via the co-expression of 5 proliferation markers (AURKB, MKI67, INCENP, CDCA8, and BIRC5). The cell-cycle-specific autoencoder (CSA) algorithm identified 7 cardiomyocyte clusters in mouse hearts (mCM1 and mCM3-mCM8), including one prominent cluster of cycling cardiomyocytes in animals that underwent MI or Sham surgery on P1. Five cardiomyocyte clusters (pCM1, pCM3-pCM6) were identified in pig hearts, 2 of which (pCM1 and pCM4) displayed evidence of cell cycle activity; pCM4 was found primarily in hearts from fetal pigs, while pCM1 comprised a small proportion of cardiomyocytes in both fetal hearts and hearts from ARP1MIP28 pigs during the 2 weeks after MI induction, but was nearly undetectable in all other experimental groups and at all other time points. Furthermore, pseudotime trajectory analysis of snRNAseq data from fetal pig cardiomyocytes identified a pathway that began at pCM3, passed through pCM2, and ended at pCM1, whereas pCM3 was enriched for the expression of a cell cycle activator that regulates the G1/S phase transition (cyclin D2), pCM2 was enriched for an S-phase regulator (CCNE2), and pCM1 was enriched for the expression of a gene that regulates the G2M phase transition and mitosis (cyclin B2). We also identified 4 transcription factors (E2F8, FOXM1, GLI3, and RAD51) that were more abundantly expressed in cardiomyocytes from regenerative mouse hearts than from nonregenerative mouse hearts, from the hearts of fetal pigs than from CTL pig hearts, and from ARP1MIP28 pig hearts than from MIP28 pig hearts during the 2 weeks after MI induction. The CSA algorithm improved the precision of our assessments of cell cycle activity in cardiomyocyte subpopulations and enabled us to identify a trajectory across 3 clusters that appeared to track the onset and progression of cell cycle activity in cardiomyocytes from fetal pigs.

Comparative analysis of single-cell transcriptome reveals heterogeneity and commonality in the immune microenvironment of colorectal cancer and inflammatory bowel disease.

During aging, chronic inflammation can promote tumor development and metastasis. Patients with chronic inflammatory bowel diseases (IBD) are at an increased risk of developing colorectal cancer (CRC). However, the molecular mechanism underlying is still unclear. We conducted a large-scale single-cell sequencing analysis comprising 432,314 single cells from 92 CRC and 24 IBD patients. The analysis focused on the heterogeneity and commonality of CRC and IBD with respect to immune cell landscape, cellular communication, aging and inflammatory response, and Meta programs. The CRC and IBD had significantly different propensities in terms of cell proportions, differential genes and their functions, and cellular communication. The progression of CRC was mainly associated with epithelial cells, fibroblasts, and monocyte-macrophages, which displayed pronounced metabolic functions. In particular, monocyte-macrophages were enriched for the aging and inflammation-associated NF-κB pathway. And IBD was enriched in immune-related functions with B cells and T cells. Cellular communication analysis in CRC samples displayed an increase in MIF signaling from epithelial cells to T cells, and an increase in the efferent signal of senescence-associated SPP1 signaling from monocyte-macrophages. Notably, we also found some commonalities between CRC and IBD. The efferent and afferent signals showed that the pro-inflammatory cytokine played an important role. And the activity of aging and inflammatory response with AUCell analysis also showed a high degree of commonality. Furthermore, using the Meta programs (MPs) with the NMF algorithm, we found that the CRC non-malignant cells shared a substantial proportion of the MP genes with CRC malignant cells (68% overlap) and IBD epithelial cells (52% overlap), respectively. And it was extensively involved in functions of cell cycle and immune response, revealing its dual properties of inflammation and cancer. In addition, CRC malignant and non-malignant cells were enriched for the senescence-related cell cycle G2M phase transition and the p53 signaling pathway. Our study highlights the characteristics of aging, inflammation and tumor in CRC and IBD at the single-cell level, and the dual property of inflammation-cancer in CRC non-malignant cells may provide a more up-to-date understanding of disease transformation.

Computational Exploration of Potential Polo-Like Kinase 1 Inhibitors as New Chemotherapeutic Agents

Background and Objective: Polo like kinase-1 (PLK-1) enzyme belongs to serine/threonine protein kinase family that is regarded as a principle mitotic controller of G2-M phase transition. The antimitotic therapies are a cornerstone for the treatment of metastatic as well as benign cancer. Therefore, PLK-1 has recently gained much interest in the field of targeting it by novel and effective inhibitors.
 Materials and Methods: The present study described the used of pharmacophore modelling based on the potent and selective clinical agent, Volasertib and followed by hybrid selection of a kinase inhibitors databank of 4800 diverse compounds by pharmacophore- and docking-based virtual screening.
 Results: The retrieved hits were filtered on the bases of their pharmacophore-fit scores, docking binding affinity scores, ADME-T profiles as well as ligand quality assessments. Among the five hit compounds that fulfil the criterion, three compounds, Z1991791422, Z56115729 and Z1991791176 were selected for binding dynamic analyses by molecular dynamic simulation. The Z1991791422 and Z56115729 compounds illustrated stable binding behaviours at the proposed binding site. Conclusion: Thus, these compounds might emerge as potent inhibitors of PLK1 and could be applied as seeds for designing better PLK1 inhibitors in near future.

Kinome-Wide Screening with Small Interfering RNA Identified Polo-like Kinase 1 as a Key Regulator of Proliferation in Oral Cancer Cells.

Oral squamous cell carcinoma (OSCC) is one of the major leading causes of cancer-related death worldwide, with limited effective markers for diagnosis and therapy, which has caused a low overall survival rate in the past decades. Kinases play important roles in tumor development and malignancy in various types of cancer. However, little is known about the role of kinases in OSCC cells. In this study, an arrayed kinome small interfering RNA (siRNA) library was used to screen oral cancer cell lines and counter assayed with normal fibroblast cells to identify the genes required for cancer cell proliferation. We found that polo-like kinase 1 (PLK1) was one of the most potent genes required for OSCC cell proliferation. The knockdown of PLK1 with a siRNA or antisense oligonucleotide (ASO) consistently diminished cyclin-B1 (CCNB1) expression/phosphorylation and the G2-M phase transition. Similar effects were observed in cells treated with the PLK1 kinase inhibitor BI6727. Besides, The Cancer Genome Atlas (TCGA) analysis revealed that PLK1 was elevated in tumor tissues and associated with short survival in patients with OSCC. We also found that PLK1 expression was highly correlated with the expression of its downstream effector, CCNB1, in patients with OSCC. Coexpression of the two genes resulted in a poor prognosis of OSCC patients, particularly those in the advanced stages of OSCC. Taken together, our results suggest that PLK1 might be a diagnostic or therapeutic marker for OSCC.

E2F is required for STAT3-mediated upregulation of cyclin B1 and Cdc2 expressions and contributes to G2-M phase transition.

Activation of transcription factor STAT3 is involved in cell proliferation, differentiation, and cell survival. Constitutive activation of STAT3 pathway has been associated with the oncogenesis of various types of cancers. It has been reported that STAT3 plays a key role in the G1 to S phase cell cycle transition induced by the cytokine receptor subunit gp130, through the upregulation of cyclins D1, D2, D3, A, and Cdc25A and the concomitant downregulation of p21 and p27. However, its role in mediating G2-M phase transition has not been studied. The cyclin B1/Cdc2 complex is widely accepted as the trigger of mitosis in all organisms and is believed to be necessary for progression through S phase and keep active during the G2-M transition and progression. In the present study, we found that activation of STAT3 stimulates cyclin B1 and Cdc2 expressions. Deletion and site-directed mutations on cyclin B1 and Cdc2 promoters indicated that E2F element mediates the upregulation of these two promoters in a STAT3-dependent manner. The findings reported here demonstrated that STAT3 participates in modulating G2-M phase checkpoint by regulating gene expressions of cyclin B1 and Cdc2 via E2F.

The Role of FOX-1 in FASD.

It is well-known that abusive alcohol exposure in humans induces a wide range of defects including changes to the heart, liver renal function and central nervous system (CNS). In the CNS, repetitive exposure reduces stem cell and neuron numbers and function, in turn reducing the potential for neuroplasticity and altering limbic system signaling. Alcohol-exposed neuronal stem cells, show reduced proliferation and survival through cell cycle mis-regulation and induced cell death. Both the G1-S and the G2-M checkpoints are disrupted through variations in cyclin/cyclin dependent kinase activities. Our lab has demonstrated increased expression of transcription factor E2F1, CDK4/6, and retinoblastoma (Rb) which accelerates G1-S phase transition and inducing premature DNA synthesis. This acceleration into replication can induce apoptosis or hinder the success of the G2-M phase transition. FOXM1 has been demonstrated to regulate a set of genes that are mainly involved in regulating progression of G2-M phase. However, its mechanism and interaction with other proteins is unclear. Therefore, it was hypothesized that FOX-1 is notably upregulated in alcohol induced cells. This upregulation could potentially affect interactions with key regulatory protein that monitor DNA integrity and induce cell death. We examine FOXM1 expression through western blot and immunohistochemistry to determine the extent of mis-regulation. Our results indicate expressional and possible functional changes in FOX1 and potential regulation changes by RB that may induce apoptosis in alcohol induced neuronal stem cells.

Prognostic role of cyclin B1 in solid tumors: a meta-analysis.

Cyclin B1 is a key mitotic cyclin in the G2-M phase transition of the cell cycle and is overexpressed in various malignant tumors. Numerous studies have reported contradictory evidences of the correlation between cyclin B1 expression and prognosis in human solid tumors. To address this discrepancy, we conducted a meta-analysis with 17 published studies searched from PubMed and Medline. Cyclin B1 overexpression was significantly associated with poor 3-year overall survival (OS) (OR = 2.05, 95% CI = 1.20 to 3.50, P = 0.009) and 5-year OS (OR = 2.11, 95% CI = 1.33 to 3.36, P = 0.002) of solid tumors. Subgroup analysis revealed that elevated cyclin B1 expression was associated with worse prognosis of lung cancer and esophageal cancer but better prognosis of colorectal cancer. In summary, overexpression of cyclin B1 is correlated with poor survival in most solid tumors, which suggests that the expression status of cyclin B1 is a significant prognostic parameter in solid tumors.

Different Roles of GRP78 on Cell Proliferation and Apoptosis in Cartilage Development.

Eukaryotic cells possess several mechanisms to adapt to endoplasmic reticulum (ER) stress and thereby survive. ER stress activates a set of signaling pathways collectively termed as the unfolded protein response (UPR). We previously reported that Bone morphogenetic protein 2 (BMP2) mediates mild ER stress and activates UPR signal molecules in chondrogenesis. The mammalian UPR protects the cell against the stress of misfolded proteins in the endoplasmic reticulum. Failure to adapt to ER stress causes the UPR to trigger apoptosis. Glucose regulated protein 78 (GRP78), as an important molecular chaperone in UPR signaling pathways, is responsible for binding to misfolded or unfolded protein during ER stress. However the influence on GRP78 in BMP2-induced chondrocyte differentiation has not yet been elucidated and the molecular mechanism underlyng these processes remain unexplored. Herein we demonstrate that overexpression of GRP78 enhanced cell proliferation in chondrocyte development with G1 phase advance, S phase increasing and G2-M phase transition. Furthermore, overexpression of GRP78 inhibited ER stress-mediated apoptosis and then reduced apoptosis in chondrogenesis induced by BMP2, as assayed by cleaved caspase3, caspase12, C/EBP homologous protein (CHOP/DDIT3/GADD153), p-JNK (phosphorylated c-Jun N-terminal kinase) expression during the course of chondrocyte differentiation by Western blot. In addition, flow cytometry (FCM) assay, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) assay and immune-histochemistry analysis also proved this result in vitro and in vivo. It was demonstrated that GRP78 knockdown via siRNA activated the ER stress-specific caspase cascade in developing chondrocyte tissue. Collectively, these findings reveal a novel critical role of GRP78 in regulating ER stress-mediated apoptosis in cartilage development and the molecular mechanisms involved.

The lamin-A/C-LAP2α-BAF1 protein complex regulates mitotic spindle assembly and positioning.

Some nuclear proteins that are crucial in interphase relocate during the G2/M-phase transition in order to perform their mitotic functions. However, how they perform these functions and the underlying mechanisms remain largely unknown. Here, we report that a fraction of the nuclear periphery proteins lamin-A/C, LAP2α and BAF1 (also known as BANF1) relocate to the spindle and the cell cortex in mitosis. Knockdown of these proteins by using RNA interference (RNAi) induces short and fluffy spindle formation, and disconnection of the spindle from the cell cortex. Disrupting the microtubule assembly leads to accumulation of these proteins in the cell cortex, whereas depolymerizing the actin microfilaments results in the formation of short spindles. We further demonstrate that these proteins are part of a stable complex that links the mitotic spindle to the cell cortex and the spindle matrix by binding to spindle-associated dynein, the actin filaments in the cell cortex and the spindle matrix. Taken together, our findings unveil a unique mechanism where the nuclear periphery proteins lamin-A/C, LAP2α and BAF1 are assembled into a protein complex during mitosis in order to regulate assembly and positioning of the mitotic spindle.

CB-03 * IDENTIFICATION AND CHARACTERISATION OF MicroRNAs INVOLVED IN GLIOBLASTOMA CELL PROLIFERATION AND SURVIVAL USING HIGH-THROUGHPUT SCREENING

INTRODUCTION MicroRNAs, single-stranded non-coding RNAs that function by reducing translation or causing degradation of target mRNAs, have been shown to play roles in multiple hallmarks of GBM, suggesting they may be of therapeutic importance. METHODS: The miRIDIAN mimic library (Dharmacon) that encompasses all human microRNAs annotated in miRBase v16.0 was used with a high-throughput imaging platform (Operetta) to identify microRNAs with potent effects on GBM cell proliferation and survival. Screens were performed in duplicate on U251 (adult) and KNS42 (paediatric) GBM cell lines. Cell number (nuclei count) was assessed 72h post-transfection and expressed as a z-score for each microRNA. MicroRNAs were considered significant candidates if their mean z-score was below zero and if it differed from that of the negative control by at least two standard deviations. Validation included RTqPCR, imaging and flow cytometry based assays. RESULTS: The functional screens resulted in approximately 100 candidates per cell line with 70% overlap between them. Based on available knowledge and potential relevance for GBM therapy, seven initial microRNAs candidates were chosen for further validation in a panel of four adult and two paediatric GBM cell lines: miR-34a-5p, miR-34b-5p, miR-34c-5p, miR-449a-5p, miR-449b-5p which all share a common seed sequence; miR-340-5p and miR-X. Of these candidates miR-X was identified as having the most potent, robust effects. MiR-X consistently caused a G2M cell cycle arrest followed by apoptosis in all cell lines and has predicted targets involved in the induction of the cytoskeleton rearrangement and non-canonical Wnt pathways following the G2M phase transition. This phenotype was specific to mimic-miR-X transfected cells. CONCLUSION: We have identified a novel potent pro-apoptotic microRNA in GBM that may be relevant for therapy. Work is ongoing to characterise the mechanism responsible for this effect and test for efficacy in vivo.

A role for smoothened during murine lens and cornea development.

Various studies suggest that Hedgehog (Hh) signalling plays roles in human and zebrafish ocular development. Recent studies (Kerr et al., Invest Ophthalmol Vis Sci. 2012; 53, 3316–30) showed that conditionally activating Hh signals promotes murine lens epithelial cell proliferation and disrupts fibre differentiation. In this study we examined the expression of the Hh pathway and the requirement for the Smoothened gene in murine lens development. Expression of Hh pathway components in developing lens was examined by RT-PCR, immunofluorescence and in situ hybridisation. The requirement of Smo in lens development was determined by conditional loss-of-function mutations, using LeCre and MLR10 Cre transgenic mice. The phenotype of mutant mice was examined by immunofluorescence for various markers of cell cycle, lens and cornea differentiation. Hh pathway components (Ptch1, Smo, Gli2, Gli3) were detected in lens epithelium from E12.5. Gli2 was particularly localised to mitotic nuclei and, at E13.5, Gli3 exhibited a shift from cytosol to nucleus, suggesting distinct roles for these transcription factors. Conditional deletion of Smo, from ∼E12.5 (MLR10 Cre) did not affect ocular development, whereas deletion from ∼E9.5 (LeCre) resulted in lens and corneal defects from E14.5. Mutant lenses were smaller and showed normal expression of p57Kip2, c-Maf, E-cadherin and Pax6, reduced expression of FoxE3 and Ptch1 and decreased nuclear Hes1. There was normal G1-S phase but decreased G2-M phase transition at E16.5 and epithelial cell death from E14.5-E16.5. Mutant corneas were thicker due to aberrant migration of Nrp2+ cells from the extraocular mesenchyme, resulting in delayed corneal endothelial but normal epithelial differentiation. These results indicate the Hh pathway is required during a discrete period (E9.5–E12.5) in lens development to regulate lens epithelial cell proliferation, survival and FoxE3 expression. Defective corneal development occurs secondary to defects in lens and appears to be due to defective migration of peri-ocular Nrp2+ neural crest/mesenchymal cells.

Research progress of cell division cycle 25 homolog C and tumor radiosensitivity

AsoneoftheCdc25phosphatasefamilymembers,Cdc25Cplaysanimportantroleinregu-lating mitosis of eukaryotic cells.In eukaryotic cells,CDK1-cell cycle protein B （CyclinB）compound mainly control the process of G2-M.The activity of Cdc25 C is the key in cell cycle into M phase.It activates CDK1-cyclinB complexes to promote cells from G2 to M phase .Improving Cdc25 C activity can promote the G2-M phase transition,and remove the G2-M phase retardation induced by ionizing radiation,preventing the damaged DNA from repaired into the phase of cell division,resulting in cell death caused by excessive cell proliferation, thus enhance radiosensitivity. Key words: Cdc25phosphatases; Radiationtolerance; Neoplasms; Cellcycle

Artemisinin derivative artesunate induces radiosensitivity in cervical cancer cells in vitro and in vivo

ObjectiveCervical cancer is the third most common type of cancer in women worldwide and radiotherapy remains its predominant therapeutic treatment. Artesunate (ART), a derivative of artemisinin, has shown radiosensitization effect in previous studies. However, such effects of ART have not yet been revealed for cervical cancer cells.MethodsThe effect of ART on radiosensitivity of human cervical cancer cell lines HeLa and SiHa was assessed using the clonogenic assay. Cell cycle progression and apoptosis alterations were analyzed by flow cytometry. For in vivo study, HeLa or SiHa cells were inoculated into nude mice to establish tumors. Tissues from xenografts were obtained to detect the changes of microvessel density, apoptosis and cell cycle distribution. Microarray was used to analyze differentially expressed genes.ResultsART increased the radiosensitivity of HeLa cells (SER = 1.43, P < 0.001) but not of SiHa cells. Apoptosis and the G2-M phase transition induced by X-ray irradiation (IR) were enhanced by ART via increased Cyclin B1 expression in HeLa cells. Tumor growth of xenografts from HeLa but not SiHa cells was significantly inhibited by irradiation combined with ART (tumor volume reduction of 72.34% in IR + ART group vs. 41.22% in IR group in HeLa cells and 48.79% in IR + ART group vs. 44.03% in IR alone group in SiHa cells). Compared with the irradiated group, cell apoptosis was increased and the G2/M cell cycle arrest was enhanced in the group receiving irradiation combined with ART. Furthermore, compared with radiation alone, X-ray irradiation plus ART affected the expression of 203 genes that function in multiple pathways including RNA transport, the spliceosome, RNA degradation and p53 signaling.ConclusionART potently abrogates the G2 checkpoint control in HeLa cells. ART can induce radiosensitivity of HeLa cells in vitro and in vivo.

A Specific Role for AKT3 in the Genesis of Ovarian Cancer through Modulation of G2-M Phase Transition

Ovarian cancer is the major cause of death from gynecological malignancy, and there is an urgent need for new therapeutic targets. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway has been strongly implicated in the genesis of ovarian cancer. However, to identify and evaluate potential targets for therapeutic intervention, it is critical to understand the mechanism by which the PI3K/AKT pathway facilitates ovarian carcinogenesis. Here, we show that AKT3 is highly expressed in 19 of 92 primary ovarian tumors. Strikingly, purified AKT3 exhibited up to 10-fold higher specific activity than AKT1, potentially amplifying the effects of AKT3 overexpression. Consistent with this finding, AKT3 levels in a range of ovarian cancer cell lines correlated with total AKT activity and proliferation rates, implicating AKT3 as a key mediator of ovarian oncogenesis. Specific silencing of AKT3 using short hairpin RNA markedly inhibited proliferation of the two cell lines with highest AKT3 expression and total AKT activity, OVCA429 and DOV13, by slowing G(2)-M phase transition. These findings are consistent with AKT3 playing a key role in the genesis of at least one subset of ovarian cancers.

Anti‐phosphopeptide antibody, P‐STM as a novel tool for detecting mitotic phosphoproteins: Identification of lamins A and C as two major targets

A polyclonal, phospho-epitope-specific antibody (P-STM) was generated to detect the activated p21-activated kinase 2 (PAK2), based on the regulatory autophosphorylation site Thr(402) of PAK2 [Yu et al., 1998]. In this report, we show that this antibody can also recognize many phosphoproteins in mitotic HeLa and A431 cells. Signal of these phosphoproteins emerged after treating the cells with nocodazole and okadaic acid, and was highly detected in G2-M phase transition of HeLa cells released from double thymidine block. Immunofluorescence analysis revealed that P-STM strongly stained HeLa cells at prometaphase and metaphase, but not at interphase and anaphase. Interestingly, this staining pattern was almost identical to that obtained by staining with MPM2, a monoclonal antibody known to react with phosphoproteins in mitotic HeLa cells. However, the phosphoproteins detected by the two antibodies are quite different. Two-dimensional gel electrophoresis (2DE) and tryptic peptide fingerprint analysis by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry were employed to identify lamins A and C as two of the mitotic cell-specific phosphoproteins recognized by P-STM. Lamins A and C immunoprecipitated from nocodazole-treated cells, but not from untreated cells showed strong reactivity to P-STM, and this reactivity lost completely after protein phosphatase 2A treatment. In summary, our results show that P-STM represents a novel tool for detecting mitotic phosphoproteins, which are different from those recognized by MPM2, and that lamins A and C are the two prominent mitotic phosphoproteins detected by P-STM.

Prognostic Value of Cyclin B1 Protein Expression in Colorectal Cancer

We used immunohistochemical analysis to study the expression and prognostic impact of cyclin B1, a key molecule for G2-M phase transition during the cell cycle, in a series of 342 curatively resected colorectal carcinomas. In 269 tumors (78.7%), high expression of cyclin B1 in more than 10% of tumor cells was observed, but there was no association between cyclin B1 expression and histopathologic tumor features. Univariate analysis revealed no impact on disease-free and overall survival. Multivariate analysis revealed pT and pN categories, extramural blood vessel invasion, and low-grade tumor cell differentiation as independent prognostic predictors for overall survival, and pT and pN categories and tumor site for disease-free survival. According to our results, high expression of cyclin B1 is a frequent and early event in colorectal carcinomas. However, cyclin B1 expression is neither a predictor of prognosis in patients with colorectal cancer nor a suitable tool for identifying subgroups of patients at higher risk for disease recurrence.

The clinical significance of Cyclin B1 and Wee1 expression innon-small-cell lung cancer

Cyclin B1 has an important role in the G2-M phase transition of the cell cycle. Wee1 delays mitosis by suppressing the activity of the Cyclin B1/cdc2 complex. The objective of the present study was to elucidate the clinicopathological and prognostic significance of Cyclin B1 and Wee1 expression in non-small-cell lung cancer (NSCLC). An immunohistochemical assessment of Cyclin B1 and Wee1 expression was performed in 79 patients with NSCLC. The expression of Cyclin B1 was correlated with differentiation (P = 0.0423) and vascular invasion (P = 0.001). Patients with overexpression of Cyclin B1 had higher mean values for both the Ki-67 proliferative index (Ki-Index) (P <0.0001) and proliferating cell nuclear antigen labeling index (PCNA-LI) (P <0.0001), and a poorer prognosis (P = 0.0068). Patients lacking expression of Wee1 had a higher recurrence rate (P = 0.0084) and a poorer prognosis (P = 0.0457), and tended to have higher Ki-Index and PCNA-LI values. Multivariate analysis suggested that both Cyclin B1 (P = 0.0244) and Wee1 (P = 0.0444) expression were significant prognostic factors. These findings suggest that Cyclin B1 expression could be a significant prognostic parameter in NSCLC. The loss of Wee1 expression may have a potential role in promoting tumor progression and may be a significant prognostic indicator in NSCLC.

Prognostic value of cyclin B1 protein expression in colorectal cancer.

We used immunohistochemical analysis to study the expression and prognostic impact of cyclin B1, a key molecule for G2-M phase transition during the cell cycle, in a series of 342 curatively resected colorectal carcinomas. In 269 tumors (78.7%), high expression of cyclin B1 in more than 10% of tumor cells was observed, but there was no association between cyclin B1 expression and histopathologic tumor features. Univariate analysis revealed no impact on disease-free and overall survival. Multivariate analysis revealed pT and pN categories, extramural blood vessel invasion, and low-grade tumor cell differentiation as independent prognostic predictors for overall survival, and pT and pN categories and tumor site for disease-free survival. According to our results, high expression of cyclin B1 is a frequent and early event in colorectal carcinomas. However, cyclin B1 expression is neither a predictor of prognosis in patients with colorectal cancer nor a suitable tool for identifying subgroups of patients at higher risk for disease recurrence.

Cdc25C expression in meiotically competent and incompetent goat oocytes.

Change in Cdc25C expression and localization during maturation and meiotic competence acquisition was investigated in goat oocytes. Western blot analysis revealed that Cdc25C is constitutively expressed throughout meiosis in competent goat oocytes, with changes in its phosphorylation level. Cdc25C was detected at 55 and 70 kDa, representing the nonphosphorylated form and the hyperphosphorylated active form, respectively. During the G2-M transition at meiosis resumption, Cdc25C was hyperphosphorylated as evidenced by a clear shift from 55 to 70 kDa. Okadaic acid which induced premature meiosis resumption associated with MPF activation also involved a premature shift from 55 to 70 kDa in goat competent oocytes. After artificial activation of goat oocytes, Cdc25C returned to its 55 kDa form. By indirect immunofluorescence, Cdc25C was found essentially localized in the nucleus at the germinal vesicle stage, suggesting that Cdc25C functions within the nucleus to regulate MPF activation. Concomitantly with germinal vesicle breakdown, Cdc25C was redistributed throughout the cytoplasm. The amount of Cdc25C, very low in incompetent oocytes, increased with meiosis competence acquisition. On the other hand, during oocyte growth while the expression of Cdc25C increased, its phosphorylation level increased concomitantly as well as its nuclear translocation. These results suggest that meiosis resumption needs a sufficient amount of Cdc25C which must be completely phosphorylated and nuclear and that the amount of Cdc25C may be a limiting factor for meiotic competence acquisition. We could consider that Cdc25C nuclear translocation and phosphorylation, during oocyte growth, prepare the oocytes in advance for the G2-M phase transition occurring during meiosis resumption.

The position of Chk1 in cancer research

Checkpoints have attracted the attention of cancer biologists, especially in the pharmaceutical industry, because these pathways might give a unique means of chemically differentiating between normal and cancerous cells. For the DNA-damage checkpoint, research efforts have focused on Chk1, a protein kinase that acts as the effector of the DNA damage signal to block the cell cycle at the G2–M-phase transition 1xChk1 and cds1: linchpins of the DNA damage and replication checkpoint pathways. Rhind, N. and Russell, P. J. Cell Sci. 2000; 113: 3889–3896PubMedSee all