Role of CCNB1, CENPF, and neutrophils in lung cancer diagnosis and prognosis.

This study aimed to investigate CCNB1, CENPF, and Neutrophils as diagnostic predictors of lung cancer and to explore their association with clinical prognosis. Clinical data were obtained for a total of 52 patients. In addition, we downloaded 555 lung cancer-related samples from the cancer genome atlas (TCGA) database. Differentially expressed genes were further screened. Immune cell infiltration and survival analysis were performed. Immunohistochemistry was used to confirm gene expression. Peripheral blood analysis showed that neutrophil percentages were significantly reduced in patients with lung cancer. The least absolute shrinkage and selection operator and multivariate regression analysis revealed that CCNB1 and CENPF were lung cancer risk factors. Both CCNB1 and CENPF are overexpressed in lung cancer. The clinical diagnostic model constructed using CCNB1, CENPF, and neutrophils had a C-index of 0.994. This model area under the curve (AUC) and internal validation C-index values were 0.994 and 0.993, respectively. The elevated expression of CCNB1 and CENPF showed that the survival rate of lung cancer patients was reduced. CCNB1 and CENPF expression was positively correlated with the clinical stage of lung cancer. Further studies confirmed that CCNB1 and CENPF are overexpressed in lung cancer tissues. The clinically constructed model with high accuracy based on CCNB1, CENPF, and neutrophils demonstrated that these are crucial indicators for lung cancer diagnosis. High expression of CCNB1 and CENPF indicates a poor prognosis in patients with lung cancer.

BMAL1 Suppresses Proliferation, Migration, and Invasion of U87MG Cells by Downregulating Cyclin B1, Phospho-AKT, and Metalloproteinase-9.

Several studies have shown that brain and muscle aryl hydrocarbon receptor nuclear translocator-like 1 (BMAL1), an important molecule for maintaining circadian rhythms, inhibits the growth and metastasis of tumor cells in several types of cancer, including lung, colon, and breast cancer. However, its role in glioblastoma has not yet been established. Here, we addressed the function of BMAL1 in U87MG glioblastoma cells with two approaches-loss and gain of function. In the loss of function experiments, cell proliferation in U87MG cells transfected with small interfering RNA (siRNA) targeting BMAL1 was increased by approximately 24% (small interfering (si)-NC 0.91 ± 0.00 vs. si-BMAL1 1.129 ± 0.08) via upregulation of cyclin B1. In addition, cell migration and invasion of BMAL1 siRNA-treated glioblastoma cells were elevated by approximately 20% (si-NC 51.00 ± 1.53 vs. si-BMAL161.33 ± 0.88) and 209% (si-NC 21.28 ± 1.37 vs. si-BMAL1 44.47 ± 3.48), respectively, through the accumulation of phosphorylated-AKT (p-AKT) and matrix metalloproteinase (MMP)-9. Gain of function experiments revealed that adenovirus-mediated ectopic expression of BMAL1 in U87MG cells resulted in a 19% (Adenovirus (Ad)-vector 0.94± 0.03 vs. Ad-BMAL1 0.76 ± 0.03) decrease in cell proliferation compared with the control via downregulation of cyclin B1 and increased early and late apoptosis due to changes in the levels of BCL2-associated X protein (BAX), B-cell lymphoma 2 (BCL-2), and cleaved caspase-3. Likewise, cell migration and invasion were attenuated by approximately 24% (Ad-vector 55.00 ± 0.00 vs. Ad-BMAL1 41.83 ± 2.90) and 49% (Ad-vector 70.01 ± 1.24 vs. Ad-BMAL1 35.55 ± 1.78), respectively, in BMAL1-overexpressing U87MG cells following downregulation of p-AKT and MMP-9. Taken together, our results suggest that BMAL1 acts as an anti-cancer gene by altering the proliferation, migration, and invasion of glioblastoma cells. Therefore, the BMAL1 gene could be a potential therapeutic target in the treatment of glioblastoma.

Comprehensive analysis of biomarkers for prostate cancer based on weighted gene co-expression network analysis.

BACKGROUND: Prostate cancer (PCa) is one of the leading causes of cancer-related death. In the present research, we adopted a comprehensive bioinformatics method to identify some biomarkers associated with the tumor progression and prognosis of PCa. METHODS: Differentially expressed genes (DEGs) analysis and weighted gene co-expression network analysis (WGCNA) were applied for exploring gene modules correlative with tumor progression and prognosis of PCa. Clinically Significant Modules were distinguished, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to Annotation, Visualization and Integrated Discovery (DAVID). Protein-protein interaction (PPI) networks were used in selecting potential hub genes. RNA-Seq data and clinical materials of prostate cancer from The Cancer Genome Atlas (TCGA) database were used for the identification and validation of hub genes. The significance of these genes was confirmed via survival analysis and immunohistochemistry. RESULTS: 2688 DEGs were filtered. Weighted gene co-expression network was constructed, and DEGs were divided into 6 modules. Two modules were selected as hub modules which were highly associated with the tumor grades. Functional enrichment analysis was performed on genes in hub modules. Thirteen hub genes in these hub modules were identified through PPT networks. Based on TCGA data, 4 of them (CCNB1, TTK, CNN1, and ACTG2) were correlated with prognosis. The protein levels of CCNB1, TTK, and ACTG2 had a degree of differences between tumor tissues and normal tissues. CONCLUSION: Four hub genes were identified as candidate biomarkers and potential therapeutic targets for further studies of exploring molecular mechanisms and individual therapy on PCa.

Mass Cytometric Cell Cycle Analysis.

The regulated proliferation of cells is a critical factor in tumor progression, antineoplastic therapies, immune system regulation, and the cellular developmental of multicellular organisms. While measurement of cell cycle state by fluorescent flow cytometry is well established, mass cytometry allows the cell cycle to be measured along with large numbers of other antigens enabling characterization of the complex interactions between the cell cycle and wide variety of cellular processes. This method describes the use of mass cytometry for the analysis of cell cycle state for cells from three different sources: in vitro cultured cell lines, ex vivo human blood or bone marrow, and in vivo labeling of murine tissues. The method utilizes incorporation of 5-Iodo-2'-deoxyuridine (IdU), combined with measurement of phosphorylated retinoblastoma protein (pRb), Cyclin B1, and phosphorylated Histone H3 (pHH3). These measurements can be integrated into a gating strategy that enables clear separation of all five phases of the cell cycle.

The subcellular location of cyclin B1 and CDC25 associated with the formation of polyploid giant cancer cells and their clinicopathological significance.

Polyploid giant cancer cells (PGCCs) are key contributors to cancer heterogeneity, and the formation of PGCCs is associated with changes in the expression of cell-cycle-related proteins. This study investigated the intracellular localization and expression level of multiple cell-cycle-related proteins in PGCCs derived from BT-549 and HEY cells. In addition, the formation of PGCCs and the clinicopathological significance of cell-cycle-related proteins in human breast and ovarian cancer were examined. The expression levels of cell-cycle-related proteins, including cyclin B1, CDC25B, CDC25C, and other cell cycle phosphoproteins, including Chk2, and Aurora-A kinase, were determined using immunostaining and western blotting both in vitro and in vivo. Migration, invasion, and proliferation in control cells, cyclin B1 knockdown cells and their PGCCs following CoCl2 treatment were compared. In addition, human breast and ovarian cancer samples were collected to determine the correlation of number of PGCCs, expression of cell-cycle-related proteins, and tumor pathologic grade and metastasis. Our results confirm that cyclin B1 was localized in the cytoplasm of PGCCs and in the nuclei of their budding daughter cells. The phosphorylated proteins Chk2 and Aurora-A kinase regulated the expression and subcellular localization of cyclin B1, CDC25B, and CDC25C. The rate of positive cytoplasmic staining of cyclin B1 and positive nuclear staining of both CDC25B and CDC25C increased with increase in tumor grade and lymph node metastasis. Cell-cycle-related proteins, including cyclin B1, CDC25B, and CDC25C play an important role in regulating the formation of PGCCs. The inhibition of cyclinB1 and CoCl2 treatment significantly promoted cell proliferation, invasion, and migration abilities. The subcellular localization of these cell-cycle-related proteins was regulated by other cell cycle phosphoproteins, and was associated with pathologic grade and metastasis of tumors in cases of human breast and ovarian cancer.

Anticancer Mechanism of Lobaplatin as Monotherapy and in Combination with Paclitaxel in Human Gastric Cancer.

OBJECTIVE: To explore the mechanism by which lobaplatin, as monotherapy and in combination with paclitaxel, inhibits the proliferation of human gastric cancer SGC-7901 cells. METHODS: After treatment, the MTT assay was used to assess cell viability; cell cycle distribution was evaluated flow-cytometrically. Western blot was used to quantitate cyclin D1, E1, B1, and Cdk2/4 protein levels. RESULTS: Lobaplatin and paclitaxel inhibited SGC-7901 cell growth in a concentration and timedependent manner, with IC25 values at 48h of 1.97±0.17µg/ml and 1.98±0.19 ng/ml, respectively. Interestingly, both drugs synergistically inhibited SGC-7901 cells (combination index [CI]<0.95). Lobaplatin did not affect cyclin D1 and CDK4 protein expression, while cyclin E1 and CDK2 levels were significantly increased, with cyclin B1 amounts markedly decreased (p<0.05). More S phase cells were observed after lobaplatin treatment compared with controls (60.03±1.25 vs. 18.69±0.96%; p<0.05). After treatment with paclitaxel, cyclin D1 and CDK4 protein levels were similar to control values; meanwhile, cylinE1 and CDK2 protein amounts were reduced, with increased cyclin B1 levels, compared with control values (p<0.05). More G2/M cells were obtained after treatment with paclitaxel compared with control values (74.54±0.92 vs. 18.62±0.44% (p<0.05). Lobaplatin and paclitaxel combination did not affect cyclin D1 and CDK4 protein levels (p>0.05); meanwhile, cyclin E1 and CDK2 levels were increased, with reduced cyclin B1 amounts, compared with control values (p<0.05). Notably, more S (43.23±0.81 vs. 22.32±0.86%) and G2/M (31.22±0.96 vs. 25.81±2.08%) phase cells were obtained after combined treatment compared with control values. CONCLUSION: Lobaplatin and paclitaxel synergistically inhibit SGC-7901 cells.

Cell Cycle Analysis by Mass Cytometry.

The regulated progression of cells through the cell cycle during proliferation is a critical factor in tumor progression, anti-neoplastic therapy response, immune system regulation, and developmental biology. While flow cytometric measurement of cell cycle progression is well established, mass cytometry assays allow the cell cycle to be measured along with up to 39 other antigens enabling characterization of the complex interactions between the cell cycle and a wide variety of cellular processes. This method describes the use of mass cytometry for the analysis of cell cycle state for cells from three different sources: in vitro cultured cell lines, ex vivo human blood or bone marrow, and in vivo labeling and ex vivo analysis of murine tissues. The method utilizes incorporation of 5-Iodo-2'-deoxyuridine (IdU), combined with measurement of phosphorylated retinoblastoma protein (pRb), cyclin B1, and phosphorylated histone H3 (p-HH3). These measurements can be integrated into a gating strategy that allows for clear separation of all five phases of the cell cycle.

Study on the effect of integrin ανß6 on the proliferation and apoptosis of thyroid carcinoma cells.

PURPOSE: To study the effect of integrin αvß6 on the proliferation and apoptosis of thyroid carcinoma cells. METHODS: The experiment was conducted on 3 groups : the control group, the positive observation group (in which the ανß6 on the surface of the thyroid carcinoma cell line SW579 was blocked by monoclonal antibody 10D5) and the negative observation group (in which the ανß6 was dealt with the negative placebo of 10D5-the IgG2a). Cell proliferation was detected by MTT assay, apoptosis by flow cytometry and the protein levels in Caspase-3, CyclinB1 and Bcl-xl as well as the protein levels in ERK, p-ERK, JNK, p-JNK, p38 and p-p38 were detected by Western blot. RESULTS: The cell survival rates of the control group and the negative observation group were prominently higher than those of the positive observation group, following decrease in the apoptosis rates, and the differences were statistically significant (p<0.05). The protein levels in CyclinB1 and Bcl-x1 of the control group and the negative observation group were prominently higher than those of the positive observation group, whereas the levels in Caspase-3 were decreased; the differences were statistically significant (p<0.05). The protein levels in p-ERK, p-JNK and p-p38 of the control group and the negative observation group were prominently higher than those of the positive observation group, while the protein levels of ERK, JNK and p38 showed no difference. CONCLUSION: Integrin ανß6 can mediate the MAPK signal pathway of the cells and regulate the expression of CyclinB1 and the apoptosis-related proteins like Bcl-x1 and Caspase-2, thus affecting the process of the proliferation and apoptosis of thyroid carcinoma cells.

[Knockdown of DNA-PKcs inhibits cell cycle and its mechanism of drug-resistant Bel7402/5-Fu hepatocellular carcinoma cells].

Objective To study the effect of the knock-down of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) on the cell cycle of the multidrug-resistant (MDR) Bel7402/5-Fu hepatocellular carcinoma cells and its MDR mechanism. Methods After cationic liposome-mediated siDNA-PKcs oligonucleotide transfection, the drug sensitivity of Bel7402/5-Fu cells to 5-fluorouracil (5-Fu) and adriamycin (ADM) was determined by MTT assay; the cell cycle were detected by flow cytometry; meanwhile, the protein expressions of cell cycle-related proteins P21, cell cycle protein B1 (cyclin B1), cell cycle division protein 2 (CDC2) were tested by Western blotting; the expressions of ataxia telangiectasia mutated (ATM) and p53 at both mRNA and protein levels were detected by real-time PCR and Western blot analysis. Results The MTT results showed siDNA-PKcs increased the chemotherapeutic sensitivity of Bel7402/5-Fu cells to 5-Fu and ADM. The flow cytometric analysis showed siDNA-PKcs decreased the percentage of S-phase cells but increased the percentage of G2/M phase cells. Western blotting showed siDNA-PKcs increased the protein expression of P21 but decreased cyclinB1 and CDC2 proteins. In addition, siDNA-PKcs also increased the expressions of ATM and p53. Conclusion DNA-PKcs silencing increases P21 while decreases cyclin B1 and CDC2 expressions, and finally induces G2/M phase arrest in Bel7402/5-Fu cells, which may be related to ATM-p53 signaling pathway.

The natural compound gambogic acid radiosensitizes nasopharyngeal carcinoma cells under hypoxic conditions.

AIMS: Hypoxia is an important factor that causes decreased local disease control as well as increased distant metastases and resistance to radiotherapy in patients with advanced nasopharyngeal carcinoma (NPC). Gambogic acid (GA), the major active ingredient of gamboge, exerts antitumor effects in vitro and in vivo. However, the molecular mechanism by which GA inhibits tumor radioresistance remains unclear. The present study aimed to investigate the radiosensitizing effects of GA on NPC and explore the underlying mechanisms. MATERIALS AND METHODS: CNE-1 and CNE-2 cells exposed to hypoxia and radiation were treated with GA at different concentrations. CCK-8 assay, clonogenic assay, and flow cytometry were performed to analyze cell proliferation, colony formation, apoptosis, and cell cycle. The expression levels of hypoxia-inducible factor-1α (HIF-1α), Bcl-2, Bax, caspase-3, cyclin B1/p-cdc2 and γ-H2AX were assessed using Western blot and/or immunofluorescence analysis. RESULTS: Results of the CCK-8 assay, clonogenic assay, and flow cytometry showed that treatment of NPC cells with growth-suppressive concentrations of GA resulted in G2/M phase arrest and apoptosis. Western blot analysis demonstrated that GA-induced cell cycle arrest and apoptosis in CNE-2 cells was associated with upregulated expression of caspase-3 and Bax and downregulated expression of Bcl-2 and cyclin B1/p-cdc2 in hypoxia. Treatment with GA markedly decreased the expression of HIF-1α under hypoxic conditions. CONCLUSIONS: The results of this study suggest that GA efficiently radiosensitizes NPC cells and the effect may be significant in hypoxic conditions.

Cell cycle marker expression in benign and malignant intraductal papillary lesions of the breast.

AIMS: The diagnosis of intraductal papillary lesions of the breast on core biopsy remains challenging in pathology, with most patients requiring formal surgical excision for a definitive diagnosis. The aim of this study was to determine whether a representative panel of proliferative cell cycle immunohistochemical markers (cyclin A2, cyclin B1 and cyclin D1) could improve the specificity of pathological diagnosis of these lesions. METHODS: A series of 68 surgically excised intraductal papillary lesion cases were retrospectively selected, and immunohistochemistry for cyclin A2, cyclin B1 and cyclin D1 was performed. RESULTS: Cyclin B1 (OR 1.80, 95% CI 1.01 to 3.2, p=0.046) and cyclin D1 (OR 1.13, 95% CI 1.05 to 1.22, p=0.002) expression was independently associated with a diagnosis of malignancy in papillary lesions, although expression was frequently heterogeneous and only focal. Cyclin A2 expression (OR 0.76, 95% CI 0.41 to 1.4, p=0.38) was not associated with a malignant diagnosis in multivariable logistic regression models. All three cyclins displayed high sensitivity (80%-95%) for a diagnosis of malignancy, although cyclin B1 showed a superior specificity of 72.7% compared with the low specificity of cyclins A2 and D1. CONCLUSIONS: Our study has identified for the first time that the expression of key cell cycle markers differs between benign and malignant papillary breast lesions and identified changes to the mitotic marker, cyclin B1, as particularly significant. However, given the low level and heterogeneous nature of expression of these markers, there remains a significant risk of undersampling in core biopsies and thus they are unlikely to be useful in routine clinical practice.

Potential diagnostic biomarkers: differential expression of LMP2/ß1i and cyclin B1 in human uterine leiomyosarcoma.

AIMS AND BACKGROUND: Whilst most uterine smooth muscle neoplasms are benign, uterine leiomyosarcoma (Ut-LMS) is extremely malignant with a high incidence of metastasis and recurrence. Gynecological tumors are often associated with female hormone secretion, but no strong link has been detected between human Ut-LMS and the hormonal environment. In fact, the risk factors for Ut-LMS are poorly understood. In addition, no diagnostic biomarkers for differentiating between leiomyoma, a benign tumor, and malignant Ut-LMS have been found. Interestingly, mice that were homozygously deficient for LMP2/ß1i were found to spontaneously develop Ut-LMS and exhibited a Ut-LMS prevalence of ~40% by 14 months of age. Thus, analyzing potential risk factors for Ut-LMS (such as LMP2/ß1i) might aid the development of diagnostic biomarkers and clinical treatments for the condition. METHODS AND STUDY DESIGN: Fifty-seven patients (age range: 32-83 years) who had been diagnosed with uterine mesenchymal tumors were chosen from a pathological archive. Tissue samples from these patients were fixed in 10% buffered formalin, incubated in 4% paraformaldehyde for 8 hours, and embedded in paraffin. Tissue sections were stained with hematoxylin and eosin for standard histological examination or were subjected to further processing for immunohistochemical (IHC) examination. Serial Ut-LMS, bizarre leiomyoma, leiomyoma, and myometrium sections were subjected to IHC staining of ß-smooth muscle actin, estrogen receptor, cyclin B1, LMP2/ß1i, calponin h1, ki-67, tumor protein p53, and progesterone receptor. RESULTS: The Ut-LMS samples were positive for cyclin B1 and negative for LMP2/ß1i, while the opposite result was obtained for bizarre leiomyoma, leiomyoma, and myometrium samples. CONCLUSIONS: The expression pattern of LMP2/ß1i and cyclin B1 might be a diagnostic biomarker for human Ut-LMS. Studies of the biological roles of LMP2/ß1i and/or cyclin B1 could lead to the elucidation of new targets for therapies against Ut-LMS.

The prognostic value of Cyclin B1 in pancreatic cancer.

Pancreatic cancer (PC), a malignancy with very poor prognosis, presents many molecular alterations, including overexpression of Cyclin B1. However, the prognostic value of the protein in PC remains to be elucidated. In the present study, Cyclin B1 expression was detected immunohistochemically in specimens from 241 patients with PC and was correlated with clinicopathological features and patient survival. It was found that Cyclin B1 expression, located in nucleus and/or cytoplasm, was not statistically associated with clinicopathologic variables. However, overall survival of patients with high Cyclin B1 expression was significantly poorer than that of those with low Cyclin B1 expression (P = 0.010). Moreover, Cyclin B1 was identified as an independent prognostic factor by multivariate Cox regression test (P = 0.003). Finally, its independent implication for prognosis was proven in five subgroups of PC, i.e., males, patients aged ≤ 65 years, G1-2 and N0 tumors as well as those with perineural invasion (all P < 0.05). These data indicate that high expression of Cyclin B1 is a valuable molecular marker of unfavorable prognosis in PC.

Cucurbitacin-I, a natural cell-permeable triterpenoid isolated from Cucurbitaceae, exerts potent anticancer effect in colon cancer.

Cucurbitacin-I is a triterpenoids found in medicinal plants and have diverse pharmacological and biological activities. In this study, the antitumor effects of cucurbitacin-I on colon cancer and possible roles in apoptosis and cell cycle arrest were investigated. Treatment of SW480 cells, a human colon cancer cells, with cucurbitacin-I decreased cell viability and cell proliferation in a concentration-dependent manner. Also, cucurbitacin-I induced G2/M phase cell cycle arrest in SW480 cells with a decreased expression of cell cycle proteins including cyclin B1, cyclin A, CDK1, and CDC25C. Moreover, cucurbitacin-I induced increased cleavage of caspase-3, -7, -8, -9, and poly ADP ribose polymerase. When we examined the inhibitory effect of cucurbitacin-I on tumor growth in vivo, cucurbitacin-I effectively inhibited the tumorigenicity and growth of CT-26 cells in syngenic BALB/c mice. In summary, the present study showed that cucurbitacin-I reduced colon cancer cell proliferation by enhancing apoptosis and causing cell cycle arrest at the G2/M phase.

Prediction of Oncotype DX and TAILORx risk categories using histopathological and immunohistochemical markers by classification and regression tree (CART) analysis.

Oncotype DX is an RT-PCR assay used to predict which patients with ER-positive node-negative (NN) disease will benefit from chemotherapy. Each patient is stratified into a risk category based on a recurrence score (RS) and the TAILORx trial is determining the benefit of chemotherapy for patients with mid-range RSs. We tested if Oncotype DX and TAILORx risk categories could be predicted by standard pathological features and protein markers corresponding to 10 genes in the assay (ER, PR, Ki67, HER2, BCL2, CD68, Aurora A kinase, survivin, cyclin B1 and BAG1) on 52 patients who enrolled on TAILORx. Immunohistochemistry for the protein markers was performed on whole tissue sections. Classification and regression tree (CART) analysis correctly classified 69% of cases into Oncotype DX risk categories based on the expression of PR, survivin and nuclear pleomorphism. All tumours with PR staining (Allred score ≥ 2) and marked nuclear pleomorphism were in the high-risk category. No case with PR <2, low survivin (≤ 15.5%) and nuclear pleomorphism <3 was high-risk. Similarly, 77% of cases were correctly classified into TAILORx categories based on nuclear pleomorphism, survivin, BAG1 and cyclin B1. Ki67 was the only variable that predicted the absolute RS with a cut-off for positivity of 15% (p = 0.003). In conclusion, CART revealed key predictors including proliferation markers, PR and nuclear pleomorphism that correctly classified over two thirds of ER-positive NN cancers into Oncotype DX and TAILORx risk categories. These variables could be used as an alternative to the RT-PCR assay to reduce the number of patients requiring Oncotype DX testing.

Expression of cyclin A, B1 and D1 after induction of cell cycle arrest in the Jurkat cell line exposed to doxorubicin.

Jurkat human lymphoblastoid cells were incubated in increasing concentrations of doxorubicin (0.05, 0.1 and 0.15 µM) to induce cell death, and their expression of cyclin A, B1 and D1 was evaluated by flow cytometry (cell cycle progression, Annexin V assay, percentages and levels of each of the cyclins), transmission electron microscopy (ultrastructure) and confocal fluorescence microscopy (expression and intracellular localization of cyclins). After low-dose doxorubicin treatment, Jurkat cells responded mainly by G2/M arrest, which was related to increased cyclin B1, A and D1 levels, a low level of apoptosis and/or mitotic catastrophe. The influence of doxorubicin on levels and/or localization of selected cyclins was confirmed, which may in turn contribute to the G2/M arrest induced by the drug.

Spatial positive feedback at the onset of mitosis.

Mitosis is triggered by the activation of Cdk1-cyclin B1 and its translocation from the cytoplasm to the nucleus. Positive feedback loops regulate the activation of Cdk1-cyclin B1 and help make the process irreversible and all-or-none in character. Here we examine whether an analogous process, spatial positive feedback, regulates Cdk1-cyclin B1 redistribution. We used chemical biology approaches and live-cell microscopy to show that nuclear Cdk1-cyclin B1 promotes the translocation of Cdk1-cyclin B1 to the nucleus. Mechanistic studies suggest that cyclin B1 phosphorylation promotes nuclear translocation and, conversely, nuclear translocation promotes cyclin B1 phosphorylation, accounting for the feedback. Interfering with the abruptness of Cdk1-cyclin B1 translocation affects the timing and synchronicity of subsequent mitotic events, underscoring the functional importance of this feedback. We propose that spatial positive feedback ensures a rapid, complete, robust, and irreversible transition from interphase to mitosis and suggest that bistable spatiotemporal switches may be widespread in biological regulation.

Cyclin A and cyclin B1 overexpression in differentiated thyroid carcinoma.

Approximately 30% of patients with thyroid nodules have indeterminate or suspicious fine-needle aspiration (FNA) biopsy results. These patients usually undergo thyroidectomy because of cancer risk. Our aim was to determine diagnostic value of cyclin A and cyclin B1 immunohistochemistry added to routine cytology and their expression on histological sections. We studied the expression of cyclin A and cyclin B1 in FNA biopsies and resection specimens of 168 indeterminate or suspicious FNA biopsy results retrospectively at an academic hospital using immunohistochemistry. Malignant histopathology consisted 64 of resection specimens (58 papillary, 4 follicular, 1 medullary, and 1 Hürthle cell carcinoma). Cyclin A was overexpressed in 51.5% of malignant cases in contrast to 31.7% of 104 benign pathology specimens (P = 0.025). Cyclin B1 was positive in 39.1% of malignant specimens in contrast to 15.4% of benign cases (P = 0.001). Cyclin A overexpression was not linked to cyclin B1 overexpression. No association was found between overexpression of cyclin A, cyclin B1 and age, thyroiditis, multifocality, tumor size, extra-thyroidal extension, capsule infiltration, lymph node and distant organ metastases and TNM stage in malignant cases. Female patients with thyroid carcinoma overexpressed significantly more cyclin B1 than male patients (P = 0.015). Retrospective analysis of cyclin A and cyclin B1 in FNA biopsies yielded negative results for both benign and malignant cases. In conclusion, cyclin A and cyclin B1 are useful markers in the distinction of benign and malignant thyroid tumors and can increase diagnostic accuracy.

Regulation of mitosis and taxane response by Daxx and Rassf1.

Current theories suggest that mitotic checkpoint proteins are essential for proper cellular response to taxanes, a widely used family of chemotherapeutic compounds. We recently showed that absence or depletion of protein Daxx increases cellular taxol (paclitaxel) resistance-a common trait of patients diagnosed with several malignancies, including breast cancer. Further investigation of Daxx-mediated taxol response revealed that Daxx is important for the proper timing of mitosis progression and cyclin B stability. Daxx interacts with mitotic checkpoint protein RAS-association domain family protein 1 (Rassf1) and partially colocalizes with this protein during mitosis. Rassf1/Daxx depletion or expression of Daxx-binding domain of Rassf1 elevates cyclin B stability and increases taxol resistance in cells and mouse xenograft models. In breast cancer patients, we observed the inverse correlation between Daxx and clinical response to taxane-based chemotherapy. These data suggest that Daxx and Rassf1 define a mitotic stress checkpoint that enables cells to exit mitosis as micronucleated cells (and eventually die) when encountered with specific mitotic stress stimuli, including taxol. Surprisingly, depletion of Daxx or Rassf1 does not change the activity of E3 ubiquitin ligase anaphase promotion complex/C in in vitro settings, suggesting the necessity of mitotic cellular environment for proper activation of this checkpoint. Daxx and Rassf1 may become useful predictive markers for the proper selection of patients for taxane chemotherapy.

Digitoxin and a synthetic monosaccharide analog inhibit cell viability in lung cancer cells.

Mechanisms of digitoxin-inhibited cell growth and induced apoptosis in human non-small cell lung cancer (NCI-H460) cells remain unclear. Understanding how digitoxin or derivate analogs induce their cytotoxic effect below therapeutically relevant concentrations will help in designing and developing novel, safer and more effective anti-cancer drugs. In this study, NCI-H460 cells were treated with digitoxin and a synthetic analog D6-MA to determine their anti-cancer activity. Different concentrations of digitoxin and D6-MA were used and the subsequent changes in cell morphology, viability, cell cycle, and protein expressions were determined. Digitoxin and D6-MA induced dose-dependent apoptotic morphologic changes in NCI-H460 cells via caspase-9 cleavage, with D6-MA possessing 5-fold greater potency than digitoxin. In comparison, non-tumorigenic immortalized bronchial and small airway epithelial cells displayed significantly less apoptotic sensitivity compared to NCI-H460 cells suggesting that both digitoxin and D6-MA were selective for NSCLC. Furthermore, NCI-H460 cells arrested in G(2)/M phase following digitoxin and D6-MA treatment. Post-treatment evaluation of key G2/M checkpoint regulatory proteins identified down-regulation of cyclin B1/cdc2 complex and survivin. Additionally, Chk1/2 and p53 related proteins experienced down-regulation suggesting a p53-independent cell cycle arrest mechanism. In summary, digitoxin and D6-MA exert anti-cancer effects on NCI-H460 cells through apoptosis or cell cycle arrest, with D6-MA showing at least 5-fold greater potency relative to digitoxin.