Functional roles of PC‐PLC and Cdc20 in the cell cycle,proliferation, and apoptosis

Phosphatidylcholine‐specific phospholipase C (PC‐PLC) is the major enzyme in the Phosphatidylcholine (PC) cycle and is involved in many long‐term cellular responses such as activation, proliferation, and differentiation events. Cell division cycle 20 homolog (Cdc20) is an essential cell‐cycle regulator required for the completion of mitosis. Our previous studies identified the interaction between PC‐PLC and Cdc20. Through the interaction, Cdc20 could mediate the degradation of PC‐PLC by Cdc20‐mediated ubiquitin proteasome pathway (UPP). In this study, we found that PC‐PLC might not be involved in cancer metastasis. Inhibition of PC‐PLC by D609 could cause cell proliferation inhibition and apoptosis inhibition in CBRH‐7919 cells. Inhibition of PC‐PLC could also influence the cell cycle by arresting the cells in G1 phase, and Cdc20 might be involved in these processes. Taken together, in this report, we provided new evidence for the functional roles of PC‐PLC and Cdc20 in the cell cycle, proliferation, and apoptosis in CBRH‐7919 cells. Copyright © 2010 John Wiley & Sons, Ltd.     

Prostate cancer stem-like cells proliferate slowly and resist etoposide-induced cytotoxicity via enhancing DNA damage response

Despite the development of chemoresistance as a major concern in prostate cancer therapy, the underlying mechanisms remain elusive. In this report, we demonstrate that DU145-derived prostate cancer stem cells (PCSCs) progress slowly with more cells accumulating in the G1 phase in comparison to DU145 non-PCSCs. Consistent with the important role of the AKT pathway in promoting G1 progression, DU145 PCSCs were less sensitive to growth factor-induced activation of AKT in comparison to non-PCSCs. In response to etoposide (one of the most commonly used chemotherapeutic drugs), DU145 PCSCs survived significantly better than non-PCSCs. In addition to etoposide, PCSCs demonstrated increased resistance to docetaxel, a taxane drug that is commonly used to treat castration-resistant prostate cancer. Etoposide produced elevated levels of γH2AX and triggered a robust G2/M arrest along with a coordinated reduction of the G1 population in PCSCs compared to non-PCSCs, suggesting that elevated γH2AX plays a role in the resistance of PCSCs to etoposide-induced cytotoxicity. We have generated xenograft tumors from DU145 PCSCs and non-PCSCs. Consistent with the knowledge that PCSCs produce xenograft tumors with more advanced features, we were able to demonstrate that PCSC-derived xenograft tumors displayed higher levels of γH2AX and p-CHK1 compared to non-PCSC-produced xenograft tumors. Collectively, our research suggests that the elevation of DNA damage response contributes to PCSC-associated resistance to genotoxic reagents.     

非典型E2F转录因子对细胞周期的调控及其功能

E2F家族转录因子是细胞周期调控网络中的重要环节之一,对细胞的增殖、分化和凋亡进行调节,并参与多种生理和病理过程。近年来,关于哺乳动物中E2F转录因子的生物学作用研究取得了很大进展,并鉴定出两个非典型的E2F家族成员：E2F7和E2F8。与典型的E2F转录因子相比,非典型E2F蛋白结构中含有两个相同的DNA结合域,对靶基因转录的调控不依赖于二聚化蛋白。非典型E2F蛋白进入细胞核后,通过与经典的E2F靶基因启动子结合,发挥转录抑制作用并调节细胞周期的进程,从而对细胞的大小、多倍化、增殖、分化和凋亡进行调控。随着基因敲除模型的建立和完善,使得进一步研究非典型E2F转录因子在不同组织或器官中的生物学作用成为可能。非典型E2F在胚胎发育、血管发生及造血系统中均发挥重要作用。另外,肿瘤细胞中典型E2F和非典型E2F的表达比例发生改变,说明非典型E2F成员还参与肿瘤的发生发展。该文综述了近年来关于非典型E2F转录因子的表达、调节及其生理病理作用的研究进展。     

Cadmium-induced abnormality in strains of Euglena gracilis: morphological alteration and its prevention by zinc and cyanocobalamin

Euglena gracilis is susceptible to cadmium (Cd) at high concentrations. There are no comparative data on cytotoxicity or abnormality of CdCl₂ to E. gracilis Z and its achlorophyllous mutant SMZ. The present study examined the cytotoxicity of CdCl₂ under continual exposure at levels ranging from sub-ppm to ppm, and assessed the effects of zinc (Zn) or cyanocobalamin (VB₁₂) supplementation on the suppression of Cd-induced abnormal cell proliferation and hypertrophy. With Zn levels restricted to 1 ppm [as Zn⁺⁺], cell growth of both E. gracilis strains was reduced in proportion to Cd concentration. More abnormal cells (hypertrophied, V-shape and starfish-shape) were observed in both strains at sub-ppm levels of Cd. ZnSO₄ supplementation from 2 to 63 ppm significantly suppressed the incidence of Cd-induced abnormality. However, a significant increase in abnormal cells was observed following Zn supplementation at levels of 125 and 250 ppm, which produced remarkable differences in cell morphology. The incidence of abnormal cells varied with supplemented VB₁₂ levels ranging from 4 to 250 ppb in both E. gracilis strains.     

Aromatase expression and cell proliferation following injury of the adult zebra finch hippocampus

Estrogens can be neuroprotective following traumatic brain injury. Immediately after trauma to the zebra finch hippocampus, the estrogen-synthetic enzyme aromatase is rapidly upregulated in astrocytes and radial glia around the lesion site. Brain injury also induces high levels of cell proliferation. Estrogens promote neuronal differentiation, migration, and survival naturally in the avian brain. We suspect that glia are a source of estrogens promoting cell proliferation after neural injury. To explore this hypothesis, we examined the spatial and temporal relationship between glial aromatase expression and cell proliferation after neural injury in adult female zebra finches. Birds were ovariectomized and given a blank implant or one filled with estradiol; some birds were also administered an aromatase inhibitor or vehicle. All birds received penetrating injuries to the right hippocampus. Twenty-four hours after lesioning, birds were injected once with BrdU to label mitotically active cells and euthanized 2 h, 24 h, or 7 days later. The brains were processed for double-label BrdU and aromatase immunocytochemistry. Injury-induced glial aromatase expression was unaffected by survival time and aromatase inhibition. BrdU labeling was significantly reduced at 24 h by ovariectomy and by aromatase inhibition; effects were partially reversed by E2 replacement. Irrespective of ovariectomy, the densities of aromatase immunoreactive astrocytes and BrdU-labeled cells at known distances from the lesion site were highly correlated. These data suggest that injury-induced glial aromatization may influence the reorganization of injured tissue by providing a rich estrogenic environment available to influence cellular incorporation.     

长链非编码RNA LINC00885在人食管癌细胞中的作用研究

探讨长链非编码RNA LINC00885对人食管癌细胞EC109增殖、迁移与侵袭的影响。构建LINC00885基因过表达质粒（pcDNA3.1-LINC00885）和shRNA敲低质粒（pLKO.1-LINC00885）。分别采用集落形成实验检测EC109细胞增殖能力;划痕实验检测EC109细胞横向迁移能力;Transwell实验检测EC109细胞纵向迁移能力及侵袭能力;流式实验检测LINC00885对于细胞周期的调控;实时定量PCR方法检测LINC00885 mRNA转录水平;Western blot检测BMP7及上皮间充质转化（epithelial-to-mesenchymal transition,EMT）通路相关蛋白（VIMENTIN、β-catenim和ZO-1）表达水平。在过表达LINC00885的EC109细胞中,细胞的增殖能力、迁移能力及侵袭能力均显著增强,BMP7蛋白表达升高;而在敲低表达LINC00885的EC109细胞中,细胞的增殖能力、迁移能力与侵袭能力均显著降低,BMP7蛋白表达也随之降低。另外,在过表达LINC00885的EC109细胞中,EMT通路蛋白VI...     

Biofilm form and function: carbon availability affects biofilm architecture, metabolic activity and planktonic cell yield

Aims: To investigate carbon transformation by biofilms and changes in biofilm architecture, metabolic activity and planktonic cell yield in response to fluctuating carbon availability. Methods and Results: Pseudomonas sp. biofilms were cultured under alternating carbon‐replete and carbon‐limited conditions. A shift to medium without added carbon led to a 90% decrease in biofilm respiration rate and a 40% reduction in planktonic cell yield within 1 h. Attached cell division and progeny release were shown to contribute to planktonic cell numbers during carbon limitation. Development of a significantly enlarged biofilm surface area during carbon limitation facilitated a rapid increase in whole‐biofilm metabolic activity, cell yield and biomass upon the re‐introduction of carbon after 8 days of limitation. The cumulative number of planktonic cells (>10¹⁰ CFU) released from the biofilm during the cultivation period contained only 1·0% of the total carbon available to the biofilm, with 6·5% of the carbon retained in the biofilm and 54% mineralized to CO₂. Conclusions: Biofilm‐derived planktonic cell yield is a proliferation mechanism. The rapid response of biofilms to environmental perturbations facilitates the optimal utilization of resources to promote both proliferation and survival. Biofilms function as efficient catalysts for environmental carbon transformation and mineralization. Significance and Impact of the study: A greater understanding of the relationship between biofilm form and function can inform strategies intended to control and/or promote biofilm formation.     

Mitotic sympathetic neuroblasts initiate axonal pathfinding in vivo

Neuronal precursor proliferation and axodendritic outgrowth have been traditionally regarded as discrete and sequential developmental stages. However, we recently found that sympathetic neuroblasts in vitro often elaborate long neuritic processes before dividing. Furthermore, these “paramitotic” neurites were maintained during cell division and neuritic morphology was consistently preserved by daughter cells after mitosis. This inheritance of neuritic morphology in vitro raised the possibility that proliferating neuroblasts engage in axodendritic outgrowth. To determine whether mitotic superior cervical ganglion (SCG) neuroblasts are engaged in pathfinding in vivo, we have combined retrograde axonal tracing of efferent nerve trunks with bromodeoxyuridine (BrdU) labeling of cells in S‐phase. In fact, about 13% of BrdU(+) cells were retrogradely labeled, indicating that mitotic neuroblasts often have extraganglionic axonal projections. Moreover, the presence of axons during S‐phase was observed at two developmental ages (E15.5 and E16.5), implicating an ongoing function of paramitotic axons during neuronal ontogeny. Using a calculation to account for experimental limitations, we estimate that virtually all mitotic SCG neuroblasts have direct access to extraganglionic signals during development. We conclude that mitotic neuronal precursors in vivo engage in pathfinding, raising the possibility that interaction of proliferating populations with distant signals actively coordinates cell division and neural connectivity. © 1999 John Wiley & Sons, Inc. J Neurobiol 40: 366–374, 1999     

Role of microRNA-26a in cartilage injury and chondrocyte proliferation and apoptosis in rheumatoid arthritis rats by regulating expression of CTGF

This study is carried out to investigate the role of microRNA-26a (miR-26a) in cartilage injury and chondrocyte proliferation and apoptosis in rats with rheumatoid arthritis (RA) by regulating expression of CTGF. A rat model of RA induced by type II collagen was established. The rats were assigned into normal, RA, RA + mimics negative control (NC), and RA + miR-26a mimics groups, and the cells were classified into blank, mimics NC, and miR-26a mimics groups. The degree of secondary joint swelling and arthritis index, expression of miR-26a, pathological changes, proliferation and apoptosis of chondrocytes, and expression of CTGF, interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α, Bax, and Bcl-2 were also determined through a series of experiments. The targeting relationship between miR-26a and CTGF was verified. Initially, downregulated miR-26a was found in cartilage tissues and inflammatory articular chondrocytes of RA rats. In addition, CTGF was determined as a direct target gene of miR-26a, and upregulation of miR-26a inhibited CTGF expression in cartilage tissues of RA rats. Furthermore, upregulation of miR-26a reduced swelling and inflammation of joints, inhibited cartilage damage, apoptosis of chondrocytes, inflammatory injury, promotes proliferation, and inhibited apoptosis of inflammatory articular chondrocytes, which may be correlated with the targeting inhibition of CTGF expression. Collectively, the results demonstrate that upregulating the expression of miR-26a could attenuate cartilage injury, stimulate the proliferation, and inhibit apoptosis of chondrocytes in RA rats.