Diurnal expression of the thrombopoietin gene is regulated by CLOCK

BACKGROUND

Most physiologic processes exhibit diurnal fluctuations controlled by the circadian regulation of sleep-wake behavior and feeding cycles. In addition, many cell types express endogenous circadian rhythms that affect cell-specific processes. Independent reports support the hypothesis that thrombopoietin (TPO) is under circadian control.

OBJECTIVES

The current study tested the hypothesis that CLOCK, a circadian transcription factor, may regulate Thpo, the gene encoding TPO.

METHODS

Circadian gene expression patterns were analyzed in mice and in human cell lines, Small interfering RNA was used to knock down CLOCK expression in cell lines, and gene expression was also examined in Clock(Δ19/Δ19) mutant mice.

RESULTS

It was found that there was a diurnal rhythm in the expression of Thpoin vivo in mice, and that this was associated with concomitant rhythms of protein abundance. Thpo was rhythmically expressed in human cell lines, consistent with the gene being directly or indirectly regulated by the circadian clock. Silencing of CLOCK in the Huh7 human hepatoma cell line led to a significant reduction in the rhythmicity of Thpo expression. The expression of Mpl in murine marrow also displayed diurnal rhythmicity in vivo. In Clock(Δ19/Δ19) mutant mice, Thpo and Mpl expression was disrupted and there was an increase in the number of mature megakaryocytes, but no change in the ploidy distribution within the megakaryocyte population.

CONCLUSIONS

These findings establish that Clock regulates Thpo and Mpl expression in vivo, and demonstrate an important link between the body's circadian timing mechanisms and megakaryopoiesis.

Accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) exposure in the green anole (Anolis carolinensis)

Environmental contamination by energetic compounds is an increasing international concern, although little is known of their accumulation in and affect on wildlife. Reptiles are often good models for contaminants studies due to natural history traits that increase their potential for exposure. We report a study to assess accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, High Melting Explosive) in green anoles (Anolis carolinensis). Acute oral toxicity (LD(50)) was estimated to exceed 2000 mg/kg body weight in adult male and female anoles using a standard up-and-down method. Accumulation of HMX was assessed in adult females via dietary exposure and into eggs by two routes (directly from the soil and via maternal transfer). HMX readily accumulated into adult females in a dose-dependent manner and into eggs following both exposure pathways. However, total HMX in soil-exposed eggs was up to 40-times greater than those exposed via maternal transfer. Although there was a suggestion of an HMX-induced reduction in body weight in adult females, overall there were no effects observed over the 12 week exposure period. The only significant effect on eggs was a 50% reduction in hatching success for eggs exposed to 2000 mg/kg HMX in the soil during incubation. Growth and survival of hatchlings was not affected by HMX exposure. Our results demonstrate that HMX accumulates through the food chain and into eggs from the soil, but likely poses minimal threat to lizards except to hatching success in eggs incubated in soils with HMX levels near maximum environmental concentrations.

Image reconstruction from sparse data in synchrotron-radiation-based microtomography

Synchrotron-radiation-based microcomputed-tomography (SR-μCT) is a powerful tool for yielding 3D structural information of high spatial and contrast resolution about a specimen preserved in its natural state. A large number of projection views are required currently for yielding SR-μCT images by use of existing algorithms without significant artifacts. When a wet biological specimen is imaged, synchrotron x-ray radiation from a large number of projection views can result in significant structural deformation within the specimen. A possible approach to reducing imaging time and specimen deformation is to decrease the number of projection views. In the work, using reconstruction algorithms developed recently for medical computed tomography (CT), we investigate and demonstrate image reconstruction from sparse-view data acquired in SR-μCT. Numerical results of our study suggest that images of practical value can be obtained from data acquired at a number of projection views significantly lower than those used currently in a typical SR-μCT imaging experiment.

Thiazolidenediones induce tumour-cell apoptosis through the Akt-GSK3β pathway

WHAT IS KNOWN AND OBJECTIVE

Prostate cancer is a major health threat for men. Thiazolidenediones (TZDs) are synthetic ligands of the peroxisome proliferator-activated receptor γ (PPARγ), and previous studies have shown that TZDs induce apoptosis of prostate cancer cells independently of PPARγ activation. However, the exact mechanism of these effects remains unknown. Our objective was to investigate the effects of TZDs on apoptosis and on the serine/threonine kinase pathway, Akt, and glycogen synthase kinase 3β (GSK3β).

METHODS

LNCaP cells, a type of prostate cancer cells (derived from left supraclavicular lymph node of human prostrate carcinoma), were cultured in DMEM medium, and cell viability was evaluated with a colorimetric assay using MTT level. The total and phosphorylated protein level of Akt and GSK3β were detected by Western blotting.

RESULTS AND DISCUSSION

The apoptosis-inducing effect of TZDs on prostate cancer cells involves the inhibition of Akt phosphorylation. Furthermore, TZDs induce inactivation of GSK3β, a multifunctional kinase that mediates essential events promoting prostate cancer development and acquisition of androgen independence. In addition, the GSK3β inhibitor lithium chloride sensitizes prostate cancer cells to TZDs cytotoxicity.

WHAT IS NEW AND CONCLUSION

Our data suggest that modulation of Akt-GSK3β pathway is involved in the cell death pathway engaged by TZDs in prostate cancer cells. This reveals another possible mechanism of TZDs on apoptosis in prostate cancer. Inhibition of the Akt-GSK3β cascade may be a useful approach in prostate cancer.

MicroRNA-451 functions as a tumor suppressor in human non-small cell lung cancer by targeting ras-related protein 14 (RAB14)

Accumulating evidence suggests that microRNAs (miRNAs) are important gene regulators, which can have critical roles in diverse biological processes including tumorigenesis. In this study, we analyzed the miRNA expression profiles in non-small cell lung carcinoma (NSCLC) by use of a miRNA microarray platform and identified 40 differentially expressed miRNAs. We showed that miRNA (miR)-451 was the most downregulated in NSCLC tissues. The expression level of miR-451 was found to be significantly correlated with tumor differentiation, pathological stage and lymph-node metastasis. Moreover, low miR-451 expression level was also correlated with shorter overall survival of NSCLC patients (P<0.001). Ectopic miR-451 expression significantly suppressed the in vitro proliferation and colony formation of NSCLC cells and the development of tumors in nude mice by enhancing apoptosis, which might be associated with inactivation of Akt signaling pathway. Interestingly, ectopic miR-451 expression could significantly inhibit RAB14 protein expression and decrease a luciferase-reporter activity containing the RAB14 3'-untranslated region (UTR). In addition,, RNA interference silencing of RAB14 gene could recapitulate the tumor suppressor function of miR-451, whereas restoration of RAB14 expression could partially attenuate the tumor suppressor function of miR-451 in NSCLC cells. Furthermore, we also showed that strong positive immunoreactivity of RAB14 protein was significantly associated with downregulation of miR-451 (P=0.01). These findings suggest that miR-451 regulates survival of NSCLC cells partially through the downregulation of RAB14. Therefore, targeting with the miR-451/RAB14 interaction might serve as a novel therapeutic application to treat NSCLC patients.

Ex vivo expansion of natural killer cells with high cytotoxicity by K562 cells modified to co-express major histocompatibility complex class I chain-related protein A, 4-1BB ligand, and interleukin-15

A large number of natural killer (NK) cells with high function are expected to generate especially in tumor adoptive immunotherapy. Here K562 cells were genetically modified to co-express major histocompatibility complex class I chain-related protein A (MICA), 4-1BB ligand, and IL-15, called K562-MICA-4-1BBL-IL-15. The modified K562 cells not only promoted activation, proliferation, and survival of NK cells, but also enhanced NK cell cytotoxicity. In long-term culture tests, K562-MICA-4-1BBL-IL-15 cells stimulated NK cell to expand mean 550 folds in 24-day culture and to cover from 14.8% of total peripheral blood monoclonal lymphocytes on day 1 to 86.7% on day 24. Prevalent NK cells after expansion enhanced the ability of killing targets and producing interferon gamma (IFN-γ), and kept high expression of activating receptors. The results indicated that K562-MICA-4-1BBL-IL-15 cells would be developed for expansion of NK cells ex vivo and may have important implications for clinical immunotherapy.

Microstructure of and Crystal Defects in Nanocrystalline Tin Dioxide Thin Films

Nanocrystalline SnO2 thin films, prepared by electron beam evaporation from high purity SnO2 and post deposition annealing in air at 700°C with different times, were investigated using HRTEM. The films are composed of nanocrystalline SnO2 crystallites and pores. Many of the crystallites consist of crystal defects, such as crystallographic shearing planes (CSPs), dislocations and twin boundaries (TBs). Atomistic structures of these defects were investigated. These defects interact with each other, resulting in different configurations of crystallites. The local composition at CSP and TB steps at dislocation cores varies with the type of dislocations and CSPs and is different from the stoichiometric composition of SnO2. Thus, the electronic structure at these defects is different from that of the perfect SnO2.

The role of p27(Kip1) phosphorylation at serine 10 in the migration of malignant glioma cells in vitro

Until recently, Cip/Kip members were almost solely viewed as nuclear proteins with a principal function of inhibiting cyclin/cyclin dependent kinase (CDK) activity and hence, inhibiting cell cycle progression. P27(Kip1) (hereafter p27) belongs to the Cip/Kip family that binds and inhibits all the cyclin/CDK complexes, thus often referred as a universal CDK inhibitor. However, emerging studies now suggest that Cip/Kip proteins play additional roles outside of the nucleus. Indeed, previous reports have linked p27 to the regulation of actin dynamics and cell migration. In this study, we constructed a model of migration-activated glioma cells by using the migration-stimulating substrate, a kind of ECM, laminin in vitro. Our results present evidence that laminin drives glioma cell migration without altering cell proliferation. Further, actively migrating cells which expressioned high phosphorylation of p27 at Ser10, and induced its cytoplasmic localization. In this process, Jab1 and CRM1 were also involved. Thus phosphorylation of p27 at Ser10 is necessary for both cytoplasmic localization and induction of cell migration. These observations solidified a genetic role of p27 in cell migration and this was independent of cyclin/CDK inhibition. Eventually, we transiently transfected p27S10A into T98G glioma cells, found that overexpression of p27S10A inhibited cell migration but not cell proliferation. These data linked phosphorylation of p27 at Ser10 and cell motility. Therefore, the major phosphorylation site at Ser10 of p27 played a pivotal role in the migration of malignant glioma cells.

Inhibition of the Signal Transducers and Activators of Transcription (STAT) 3 Signalling Pathway by AG490 in Laryngeal Carcinoma Cells

Signal transducers and activators of transcription (STAT) are important in the development of laryngeal carcinomas and are potential novel molecular targets for therapy to improve survival of patients with this cancer. This study was designed to investigate the influence of the janus activated kinase (JAK)/STAT inhibitor AG490 on proliferation and apoptosis of Hep-2 human laryngeal cancer cells and whether there was any inhibition by AG490 of the JAK/STAT3 signalling pathway. AG490 inhibited cell proliferation in dose-and time-dependent manners and induced apoptosis in Hep-2 cells, with the number of apoptotic cells increasing with time. AG490 inhibited G1 to S cell cycle transition and induced G1 cell cycle arrest as well as significantly down-regulating STAT3, phosphorylated STAT3 and survivin in Hep-2 cells. This study showed that AG490 significantly inhibited proliferation and induced apoptosis of laryngeal carcinoma cells through down-regulation of STAT3 and survivin, suggesting a potential target for laryngeal carcinoma treatment.

Genome-wide reinforcement of cohesin binding at pre-existing cohesin sites in response to ionizing radiation in human cells

The cohesin complex plays a central role in genome maintenance by regulation of chromosome segregation in mitosis and DNA damage response (DDR) in other phases of the cell cycle. The ATM/ATR phosphorylates SMC1 and SMC3, two core components of the cohesin complex to regulate checkpoint signaling and DNA repair. In this report, we show that the genome-wide binding of SMC1 and SMC3 after ionizing radiation (IR) is enhanced by reinforcing pre-existing cohesin binding sites in human cancer cells. We demonstrate that ATM and SMC3 phosphorylation at Ser(1083) regulate this process. We also demonstrate that acetylation of SMC3 at Lys(105) and Lys(106) is induced by IR and this induction depends on the acetyltransferase ESCO1 as well as the ATM/ATR kinases. Consistently, both ESCO1 and SMC3 acetylation are required for intra-S phase checkpoint and cellular survival after IR. Although both IR-induced acetylation and phosphorylation of SMC3 are under the control of ATM/ATR, the two forms of modification are independent of each other and both are required to promote reinforcement of SMC3 binding to cohesin sites. Thus, SMC3 modifications is a mechanism for genome-wide reinforcement of cohesin binding in response to DNA damage response in human cells and enhanced cohesion is a downstream event of DDR.