Emerging role of exosome signalling in maintaining cancer stem cell dynamic equilibrium

Cancer stem cells (CSCs) are a small subset of heterogeneous cells existed in tumour tissues or cancer cell lines with self‐renewal and differentiation potentials. CSCs were considered to be responsible for the failure of conventional therapy and tumour recurrence. However, CSCs are not a static cell population, CSCs and non‐CSCs are maintained in dynamic interconversion state by their self‐differentiation and dedifferentiation. Therefore, targeting CSCs for cancer therapy is still not enough,exploring the mechanism of dynamic interconversion between CSCs and non‐CSCs and blocking the interconversion seems to be imperative. Exosomes are 30‐100 nm size in diameter extracellular vesicles (EVs) secreted by multiple living cells into the extracellular space. They contain cell‐state‐specific bioactive materials, including DNA, mRNA, ncRNA, proteins, lipids, etc. with their specific surface markers, such as, CD63, CD81, Alix, Tsg101, etc. Exosomes have been considered as information carriers in cell communication between cancer cells and non‐cancer cells, which affect gene expressions and cellular signalling pathways of recipient cells by delivering their contents. Now that exosomes acted as information carriers, whether they played role in maintaining dynamic equilibrium state between CSCs and non‐CSCs and their mechanism of activity are unknown. This review summarized the current research advance of exosomes’ role in maintaining CSC dynamic interconversion state and their possible mechanism of action, which will provide a better understanding the contribution of exosomes to dedifferentiation and stemness acquisition of non‐CSCs, and highlight that exosomes might be taken as the attractive target approaches for cancer therapeutics.     

3D虚拟复原精度的差异对头骨测量数值的影响——以Mimics软牛为例

近年来,根据三维软件虚拟复原的头骨来获取测量数据的方法被越来越多地应用在古生物,特别是古人类学的研究中,然而对于三维软件不同精度虚拟复原的头骨,其测量数值是否有差异,研究者并不是很清楚。本文以Mimics软件为例,根据其复原模型简化规则,选择未精简的最佳精度模型作为标准进行配对t检验或非参数检验,通过对43例云南人头骨的顶骨矢状弦长、颅周长、头盖部面积、乳突小房表面积、颅容量、乳突小房体积等六个测量项目的对比和分析,对Mimics软件低、中、高、最佳四种精度3D虚拟复原头骨间的测量差异进行了研究。结果显示：颅周长、头盖部面积、颅容量、乳突小房体积四项的所有简化精度模型的测量数据均与最佳精度模型测量数据的差异具有显著性;而除高精度组外,顶骨矢状弦长及乳突小房表面积的其余精度组测量数据均与最佳精度组差异具有显著性;此外,顶骨矢状弦长、颅周长、头盖部面积、颅容量的简化精度与最佳精度的测量差异占比均小于3%.而乳突小房表面积的低精度与最佳精度测量差异占比可超过50%,乳突小房体积的低精度与最佳精度测量差异占比可超过120%。这一结果提示我们,在测量Mimics复原的三维模型时,体量大差异小的测量项可以在较低精度的复原模型上进行测量;而对头骨内部腔窦这样体量小表面粗糙的结构,复原模型的精度选择及测量数据比较需要格外谨慎。     

EUI1, encoding a putative cytochrome P450 monooxygenase, regulates internode elongation by modulating gibberellin responses in rice

Elongation of rice internodes is one of the most important agronomic traits, which determines the plant height and underlies the grain yield. It has been shown that the elongation of internodes is under genetic control, and various factors are implicated in the process. Here, we report a detailed characterization of an elongated uppermost internode1 (eui1) mutant, which has been used in hybrid rice breeding. In the eui1-2 mutant, the cell lengths in the uppermost internodes are significantly longer than that of wild type and thus give rise to the elongated uppermost internode. It was found that the level of active gibberellin was elevated in the mutant, whereas its growth in response to gibberellin is similar to that of the wild type, suggesting that the higher level accumulation of gibberellin in the eui1 mutant causes the abnormal elongation of the uppermost internode. Consistently, the expression levels of several genes which encode gibberellin biosynthesis enzymes were altered. We cloned the EUI1 gene, which encodes a putative cytochrome P450 monooxygenase, by map-based cloning and found that EUI1 was weakly expressed in most tissues, but preferentially in young panicles. To confirm its function, transgenic experiments with different constructs of EUI1 were conducted. Overexpression of EUI1 gave rise to the gibberellin-deficient-like phenotypes, which could be partially reversed by supplementation with gibberellin. Furthermore, apart from the alteration of expression levels of the gibberellin biosynthesis genes, accumulation of SLR1 protein was found in the overexpressing transgenic plants, indicating that the expression level of EUI1 is implicated in both gibberellin-mediated SLR1 destruction and a feedback regulation in gibberellin biosynthesis. Therefore, we proposed that EUI1 plays a negative role in gibberellin-mediated regulation of cell elongation in the uppermost internode of rice.     

Heat shock response and mammal adaptation to high elevation (hypoxia)

The mammal's high elevation(hypoxia) adaptation was studied by using the immu-nological and the molecular biological methods to understand the significance of Hsp(hypoxia) ad-aptation in the organic high elevation,through the mammal heat shock response.(1) From high ele-vation to low elevation(natural hypoxia) :Western blot and conventional RT-PCR and real-time fluo-rescence quota PCR were adopted.Expression difference of heat shock protein of 70(Hsp70) and natural expression of brain tissue of Hsp70 gene was determined in the cardiac muscle tissue among the different elevation mammals(yak) .(2) From low elevation to high elevation(hypoxia induction) :The mammals(domestic rabbits) from the low elevation were sent directly to the areas with different high elevations like 2300,3300 and 5000 m above sea level to be raised for a period of 3 weeks be-fore being slaughtered and the genetic inductive expression of the brain tissue of Hsp70 was deter-mined with RT-PCR.The result indicated that all of the mammals at different elevations possessed their heat shock response gene.Hsp70 of the high elevation mammal rose abruptly under stress and might be induced to come into being by high elevation(hypoxia) .The speedy synthesis of Hsp70 in the process of heat shock response is suitable to maintain the cells' normal physiological functions under stress.The Hsp70 has its threshold value.The altitude of 5000 m above sea level is the best condition for the heat shock response,and it starts to reduce when the altitude is over 6000 m above sea level.The Hsp70 production quantity and the cell hypoxia bearing capacity have their direct ratio.     

Monitoring genome-wide changes in gene expression in response to endogenous cytokinin reveals targets in Arabidopsis thaliana

Cytokinins have been implicated in developmental and growth processes in plants including cell division, chloroplast biogenesis, shoot meristem initiation and senescence. The regulation of these processes requires changes in cytokinin-responsive gene expression. Here, we induced the expression of a bacterial isopentenyl transferase gene, IPT, in transgenic Arabidopsis thaliana seedlings to study the regulation of genome-wide gene expression in response to endogenous cytokinin. Using MPSS (massively parallel signature sequencing) we identified 823 and 917 genes that were up- and downregulated, respectively, following 24 h of IPT induction. When comparing the response to cytokinin after 6 and 24 h, we identified different clusters of genes showing a similar course of regulation. Our study provides researchers with the opportunity to rapidly assess whether genes of interest are regulated by cytokinins.     

β-1,4-Galactosyltransferase I involved in Schwann cells proliferation and apoptosis induced by tumor necrosis factor-alpha via the activation of MAP kinases signal pathways

β-1,4-galactosyltransferase-I (β-1,4-GalT-I) plays a critical role in the initiation and maintenance of peripheral nervous system inflammatory reaction. However, the exact function of β-1,4-GalT-I in the regulation of SCs proliferation and apoptosis remains unclear. In this study, we found that low concentration of tumor necrosis factor-alpha (TNF-α) induced SCs proliferation, while high concentration of TNF-α induced SCs apoptosis. Meanwhile, the expressions of β-1,4-GalT-I, TNFR1, and TNFR2 were changed following. When β-1,4-GalT I overexpression, low concentration of TNF-α-induced SCs proliferation was partially repressed. Concurrently, the activity of ERK1/2 was decreased. While knocking down β-1,4-GalT I expression, high concentration of TNF-α-induced SCs apoptosis was partially rescued. Consistent with this, the activity of P38 and JNK were decreased. We also found anti-TNFR2 antibody suppressed low concentration of TNF-α-induced SCs proliferation, while anti-TNFR1 antibody inhibited high concentration of TNF-α-induced SCs apoptosis. Thus, present data show that β-1,4-GalT I may play an important role in SCs proliferation and apoptosis induced by TNF-α via different signal pathways and TNFR.     

Neurodegeneration Induced by PVC-211 Murine Leukemia Virus Is Associated with Increased Levels of Vascular Endothelial Growth Factor and Macrophage Inflammatory Protein 1α and Is Inhibited by Blocking Activation of Microglia

PVC-211 murine leukemia virus (MuLV) is a neuropathogenic retrovirus that has undergone genetic changes from its nonneuropathogenic parent, Friend MuLV, that allow it to efficiently infect rat brain capillary endothelial cells (BCEC). To clarify the mechanism by which PVC-211 MuLV expression in BCEC induces neurological disease, we examined virus-infected rats at various times during neurological disease progression for vascular and inflammatory changes. As early as 2 weeks after virus infection and before any marked appearance of spongiform neurodegeneration, we detected vessel leakage and an increase in size and number of vessels in the areas of the brain that eventually become diseased. Consistent with these findings, the amount of vascular endothelial growth factor (VEGF) increased in the brain as early as 1 to 2 weeks postinfection. Also detected at this early disease stage was an increased level of macrophage inflammatory protein 1α (MIP-1α), a cytokine involved in recruitment of microglia to the brain. This was followed at 3 weeks postinfection by a marked accumulation of activated microglia in the spongiform areas of the brain accompanied by an increase in tissue plasminogen activator, a product of microglia implicated in neurodegeneration. Pathological observations at the end stage of the disease included loss of neurons, decreased myelination, and mild muscle atrophy. Treatment of PVC-211 MuLV-infected rats with clodronate-containing liposomes, which specifically kill microglia, significantly blocked neurodegeneration. Together, these results suggest that PVC-211 MuLV infection of BCEC results in the production of VEGF and MIP-1α, leading to the vascular changes and microglial activation necessary to cause neurodegeneration.PVC-211 murine leukemia virus (MuLV), a highly neuropathogenic variant of the leukemia-inducing virus Friend MuLV (F-MuLV), induces a rapid, age-dependent spongiform neurodegenerative disease in rodents, resulting in paralysis (24, 33). The primary target of PVC-211 MuLV infection within the rat central nervous system (CNS) is brain capillary endothelial cells (BCEC), which are resistant to F-MuLV infection (19). Previous studies using chimeras between PVC-211 MuLV and F-MuLV demonstrated that infection of BCEC is a prerequisite for neurodegeneration induced by PVC-211 MuLV (32). Further studies attributed the ability of PVC-211 MuLV to efficiently infect BCEC to two amino acid changes in the receptor binding domain of its envelope protein (31), which creates a unique heparin binding domain that may allow the virus to bind to proteoglycans on the surface of BCEC (22), aiding infection of this difficult-to-infect cell type. These results suggested that neurodegeneration caused by PVC-211 MuLV is an indirect result of virus infection of blood vessels within the CNS.The spongiform vacuolation observed in PVC-211 MuLV-infected brains is associated with oxidative damage (47), and BCEC isolated from PVC-211 MuLV-infected rats produce inducible nitric oxide synthase (iNOS) (23). However, iNOS was not induced after in vitro infection of primary BCEC, suggesting that expression of the virus in BCEC is insufficient to activate iNOS. Activated microglia, which can be detected in the brains of PVC-211 MuLV-infected rats (47), release inflammatory molecules that are known mediators of iNOS induction, and these molecules may stimulate BCEC to express iNOS and other factors. Microglial activation is thought to play a role in neuron death in a number of diseases (6, 26). Unlike BCEC, microglia in PVC-211 MuLV-infected brains are not infected with the virus, so the mechanism by which microglia are activated is unclear. Since vascular damage has been shown to lead to microglial activation (11), it is possible that PVC-211 MuLV infection of BCEC results in damaged vessels, causing the activation of microglia. Although an earlier study failed to detect enough vessel damage in the brains of PVC-211 MuLV-infected rats to allow entry of horseradish peroxidase across the blood-brain barrier (19), one cannot rule out the possibility that the virus causes more subtle vessel damage that is still sufficient to activate microglia.In this study, we examined the brains of rats at various times after infection with PVC-211 MuLV and found that vascular and inflammatory changes, associated with elevation of the endothelial cell growth factor VEGF and the inflammatory chemokine MIP-1α, occur early in the course of the disease. After spongiform neurodegeneration occurred, we detected loss of neurons, demyelination, axonal degeneration, and muscle atrophy as well as high levels of tissue plasminogen activator (tPA). Treatment of rats with clodronate-containing liposomes, which specifically kill macrophages and microglia, blocked the development of PVC-211 MuLV-induced neurodegeneration.