The IL-6–STAT3 axis mediates a reciprocal crosstalk between cancer-derived mesenchymal stem cells and neutrophils to synergistically prompt gastric cancer progression

Emerging evidence indicate that mesenchymal stem cells (MSCs) affect tumor progression by reshaping the tumor microenvironment. Neutrophils are essential component of the tumor microenvironment and are critically involved in cancer progression. Whether the phenotype and function of neutrophils is influenced by MSCs is not well understood. Herein, we investigated the interaction between neutrophils and gastric cancer-derived MSCs (GC-MSCs) and explored the biological role of this interaction. We found that GC-MSCs induced the chemotaxis of neutrophils and protected them from spontaneous apoptosis. Neutrophils were activated by the conditioned medium from GC-MSCs with increased expression of IL-8, TNFα, CCL2, and oncostatin M (OSM). GC-MSCs-primed neutrophils augmented the migration of gastric cancer cells in a cell contact-dependent manner but had minimal effect on gastric cancer cell proliferation. In addition, GC-MSCs-primed neutrophils prompted endothelial cells to form tube-like structure in vitro. We demonstrated that GC-MSCs stimulated the activation of STAT3 and ERK1/2 pathways in neutrophils, which was essential for the functions of activated neutrophils. We further revealed that GC-MSCs-derived IL-6 was responsible for the protection and activation of neutrophils. In turn, GC-MSCs-primed neutrophils induced the differentiation of normal MSCs into cancer-associated fibroblasts (CAFs). Collectively, our results suggest that GC-MSCs regulate the chemotaxis, survival, activation, and function of neutrophils in gastric cancer via an IL-6–STAT3–ERK1/2 signaling cascade. The reciprocal interaction between GC-MSCs and neutrophils presents a novel mechanism for the role of MSCs in remodeling cancer niche and provides a potential target for gastric cancer therapy.Accumulating evidence suggest that neutrophils are critical for cancer initiation and progression.^{1, 2} The increased presence of intratumoral neutrophils has been linked to a poorer prognosis for patients with renal cancer, hepatocellular carcinoma (HCC), melanoma, head and neck squamous cell carcinoma (HNSCC), pancreatic cancer, colorectal carcinoma, and gastric adenocarcinoma.³ Recent studies using murine tumor models or involving cancer patients have suggested an important functional role of neutrophils during tumor progression.^{4, 5, 6, 7} Neutrophils-derived factors promote genetic mutations leading to tumorigenesis or promote tumor cell proliferation,⁸ migration, and invasion.^{9, 10} Neutrophils have also been demonstrated to induce tumor vascularization by the production of pro-angiogenic factors^{11, 12}The infiltration of neutrophils into tumors has been shown to be mediated by factors produced by both tumor and stromal cells. Recent reports suggest that tumor cells actively modulate the functions of neutrophils. Tumor-derived CXCL5 modulates the chemotaxis of neutrophils, which in turn enhances the migration and invasion of human HCC cells.¹³ HNSCC cells-derived MIF induces the recruitment and activation of neutrophils through a p38-dependent manner.^{14, 15} Neutrophils respond to hyaluronan fragments in tumor supernatants via PI3K/Akt signaling, leading to prolonged survival and stimulating effect on HCC cell motility.¹⁶ Kuang et al.¹⁷ suggest that IL-17 promotes the migration of neutrophils into HCC through epithelial cell-derived CXC chemokines, resulting in increased MMP-9 production and angiogenesis at invading tumor edge However, much less is known about the role of stromal cells in modulating the phenotype and function of neutrophils in cancer thus far.Cancer-associated fibroblasts (CAFs) have a key role in cancer mainly through secretion of soluble factors, as growth factors or inflammatory mediators, as well as production of extracellular matrix proteins and their proteases. These activated fibroblasts are involved in creating a niche for cancer cells, promoting their proliferation, motility and chemoresistance. Activated fibroblasts express several mesenchymal markers such as α-smooth muscle actin (α-SMA), fibroblast activation protein (FAP), and vimentin. CAFs actively participate in reciprocal interaction with tumor cells and with other cell types in the microenvironment, contributing to a tumor-permissive niche and promoting tumor progression.Mesenchymal stem cells (MSCs) are adult stromal cells with self-renewal and pluripotent differentiation abilities. MSCs can be mobilized from bone marrow to the site of damage, respond to the local microenvironment, and exert wound repair and tissue regeneration functions upon injury and inflammation conditions.¹⁸ MSCs have been considered as one of the major components of the tumor stroma and are believed to be the precursors of CAFs.^{19, 20} We have previously demonstrated that human bone marrow MSCs prompt tumor growth in vivo.²¹ In addition, we have recently isolated MSCs-like cells from the gastric cancer tissues (GC) and the adjacent normal tissues (GCN) and shown that the gastric cancer-derived MSCs (GC-MSCs) possess the properties of CAFs.^{22, 23} As tumor-derived MSCs are often exposed to distinct inflammatory cells and factors in the tumor microenvironment, they may acquire novel functions that are not present in normal MSCs, and these unique functions may have a role in reshaping the tumor microenvironment and ultimately affect tumor progression. As neutrophils are key mediators of tumor progression and tumor angiogenesis, it is likely that an intense interaction may exist between the tumor-derived MSCs and tumor-infiltrating neutrophils.The emerging roles of CAFs in cancer immunoeditting led us to investigate whether GC-MSCs are able to regulate the phenotype and function of neutrophils in gastric cancer. We have shown that there is a reciprocal interaction between GC-MSCs and neutrophils. GC-MSCs enhanced the chemotaxis of peripheral blood-derived neutrophils and protected them from spontaneous apoptosis. GC-MSCs induced the activation of neutrophils to highly express IL-8, CCL2, TNFα, and oncostatin M (OSM), leading to the increase of gastric cancer cell migration and angiogenesis in vitro. GC-MSCs exerted this effect through the IL-6–STAT3–ERK1/2 signaling axis, and blockade of the IL-6–IL-6R interaction or pharmacological inhibition of STAT3 and ERK1/2 activation abrogated this role. In turn, GC-MSCs-activated neutrophils could trigger the CAF differentiation of normal MSCs. Therefore, these results establish a bi-directional interaction between GC-MSCs and neutrophils that may be critically involved in the progression of gastric cancer.     

Temporal changes of soil physic‐chemical properties at different soil depths during larch afforestation by multivariate analysis of covariance

Soil physic-chemical properties differ at different depths; however, differences in afforestation-induced temporal changes at different soil depths are seldom reported. By examining 19 parameters, the temporal changes and their interactions with soil depth in a large chronosequence dataset (159 plots; 636 profiles; 2544 samples) of larch plantations were checked by multivariate analysis of covariance (MANCOVA). No linear temporal changes were found in 9 parameters (N, K, N:P, available forms of N, P, K and ratios of N: available N, P: available P and K: available K), while marked linear changes were found in the rest 10 parameters. Four of them showed divergent temporal changes between surface and deep soils. At surface soils, changing rates were 262.1 g·kg⁻¹·year⁻¹ for SOM, 438.9 mg·g⁻¹·year⁻¹ for C:P, 5.3 mg·g⁻¹·year⁻¹ for C:K, and −3.23 mg·cm⁻³·year⁻¹ for bulk density, while contrary tendencies were found in deeper soils. These divergences resulted in much moderated or no changes in the overall 80-cm soil profile. The other six parameters showed significant temporal changes for overall 0–80-cm soil profile (P: −4.10 mg·kg⁻¹·year⁻¹; pH: −0.0061 unit·year⁻¹; C:N: 167.1 mg·g⁻¹·year⁻¹; K:P: 371.5 mg·g⁻¹ year⁻¹; N:K: −0.242 mg·g⁻¹·year⁻¹; EC: 0.169 μS·cm⁻¹·year⁻¹), but without significant differences at different soil depths (P > 0.05). Our findings highlight the importance of deep soils in studying physic-chemical changes of soil properties, and the temporal changes occurred in both surface and deep soils should be fully considered for forest management and soil nutrient balance.     

Twice exploration of tRNA +1 frameshifting in an elongation cycle of protein synthesis

Inducing tRNA +1 frameshifting to read a quadruplet codon has the potential to incorporate a non-natural amino acid into the polypeptide chain. While this strategy is being considered for genome expansion in biotechnology and bioengineering endeavors, a major limitation is a lack of understanding of where the shift occurs in an elongation cycle of protein synthesis. Here, we use the high-efficiency +1-frameshifting SufB2 tRNA, containing an extra nucleotide in the anticodon loop, to address this question. Physical and kinetic measurements of the ribosome reading frame of SufB2 identify twice exploration of +1 frameshifting in one elongation cycle, with the major fraction making the shift during translocation from the aminoacyl-tRNA binding (A) site to the peptidyl-tRNA binding (P) site and the remaining fraction making the shift within the P site upon occupancy of the A site in the +1-frame. We demonstrate that the twice exploration of +1 frameshifting occurs during active protein synthesis and that each exploration is consistent with ribosomal conformational dynamics that permits changes of the reading frame. This work indicates that the ribosome itself is a determinant of changes of the reading frame and reveals a mechanistic parallel of +1 frameshifting with –1 frameshifting.     

Pericytes augment glioblastoma cell resistance to temozolomide through CCL5-CCR5 paracrine signaling

Glioblastoma (GBM) is a prevalent and highly lethal form of glioma, with rapid tumor progression and frequent recurrence. Excessive outgrowth of pericytes in GBM governs the ecology of the perivascular niche, but their function in mediating chemoresistance has not been fully explored. Herein, we uncovered that pericytes potentiate DNA damage repair (DDR) in GBM cells residing in the perivascular niche, which induces temozolomide (TMZ) chemoresistance. We found that increased pericyte proportion correlates with accelerated tumor recurrence and worse prognosis. Genetic depletion of pericytes in GBM xenografts enhances TMZ-induced cytotoxicity and prolongs survival of tumor-bearing mice. Mechanistically, C-C motif chemokine ligand 5 (CCL5) secreted by pericytes activates C-C motif chemokine receptor 5 (CCR5) on GBM cells to enable DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-mediated DDR upon TMZ treatment. Disrupting CCL5-CCR5 paracrine signaling through the brain-penetrable CCR5 antagonist maraviroc (MVC) potently inhibits pericyte-promoted DDR and effectively improves the chemotherapeutic efficacy of TMZ. GBM patient-derived xenografts with high CCL5 expression benefit from combined treatment with TMZ and MVC. Our study reveals the role of pericytes as an extrinsic stimulator potentiating DDR signaling in GBM cells and suggests that targeting CCL5-CCR5 signaling could be an effective therapeutic strategy to improve chemotherapeutic efficacy against GBM.Subject terms: Cancer microenvironment, CNS cancer, Cancer therapy     

Responses of soil respiration to simulated precipitation pulses in semiarid steppe under different grazing regimes

Aims Precipitation pulses and different land use practices (such as grazing) play important roles in regulating soil respiration and carbon balance of semiarid steppe ecosystems in Inner Mongolia. However, the interactive effects of grazing and rain event magnitude on soil respiration of steppe ecosystems are still unknown. We conducted a manipulative experiment with simulated precipitation pulses in Inner Mongolia steppe to study the possible responses of soil respiration to different precipitation pulse sizes and to examine how grazing may affect the responses of soil respiration to precipitation pulses.Methods Six water treatments with different precipitation pulse sizes (0, 5, 10, 25, 50 and 100 mm) were conducted in the ungrazed and grazed sites, respectively. Variation patterns of soil respiration of each treatment were determined continuously after the water addition treatments.Important findings Rapid and substantial increases in soil respiration occurred 1 day after the water treatments in both sites, and the magnitude and duration of the increase in soil respiration depended on pulse size. Significantly positive relationships between the soil respiration and soil moisture in both sites suggested that soil moisture was the most important factor responsible for soil respiration rate during rain pulse events. The ungrazed site maintained significantly higher soil moisture for a longer time, which was the reason that the soil respiration in the ungrazed site was maintained relatively higher rate and longer period than that in the grazed site after a rain event. The significant exponential relationship between soil temperature and soil respiration was found only in the plots with the high water addition treatments (50 and 100 mm). Lower capacity of soil water holding and lower temperature sensitivity of soil respiration in the grazed site indicated that degraded steppe due to grazing might release less CO₂ to the atmosphere through soil respiration under future precipitation and temperature scenarios.     

入侵杂草一年蓬的化感作用研究

用入侵杂草一年蓬(Erigeron annuus)地上部分的水浸提液对几种经济作物种子进行萌发培养实验,分别测定种子的最终萌发率、根长以及苗高来研究一年蓬是否存在他感作用。结果表明:(1)一年蓬的化感作用是存在的;(2)一年蓬水浸提液在高浓度下对作物种子萌发、根长和苗高均有明显的抑制作用,而在低浓度下则对长梗白菜、番茄的苗高具有促进生长的作用。     

硬覆盖对土壤水热传输及作物生长发育影响的试验研究

河北省盐渍区农业水资源非常紧缺 ,农业节水势在必行。覆盖保摘技术是农田节水管理的重要措施之一 ,国内外对此有过不少研究报道。但多集中在地膜、秸秆、砂砾和化学喷涂等覆盖材料上 ,这些覆盖材料在使用中有种种不理想之处 ,如地膜覆盖容易造成残膜的“白色污染” ,并且使用年限短 ,降水不易入渗 ,中耕、除草、施肥困难 ,使作物抗病力差等[1 ] ;秸秆覆盖容易使秸秆中的毒素物质与作物间发生生化它感现象 ,影响作物生长[2 ] 。化学喷涂除了不利于农事作业外 ,还可能造成土壤污染。为此 ,我们在中国科学院南皮试区盐渍土上试用了一种新型覆…     

细胞外基质和细胞粘附分子表达与细支气管肺泡癌淋巴结转移的关系

用免疫组化方法检测50例细支气管肺泡癌（BAC）（其中18例伴有淋巴结转移）及其三个亚型粘液型、非粘液型、硬化型中基底膜细胞外基质（ECM）层粘连蛋白（LN）、Ⅳ型胶原（CollⅣ）、纤粘连蛋白（FN）分布和细胞粘附分子A－CAM（又称N－钙粘素）表达情况。结果发现粘液型、非粘液型、硬化型BAC的淋巴结转移率分别为57％（8／14）、32％（7／22）和21％（3／14）。在BAC及BAC各亚型中,三种ECM在基底膜水平的分布状态与淋巴结转移无关（P均＞0.05）、A－CAM在伴或不伴淋巴结转移的BAC原发瘤中的表达率分别为56％（10／18）和53％（17／32）（P＞0.05）。提示BAC三个亚型中粘液型淋巴结转移率有高于其它两亚型的倾向。基底膜ECM（LN、CollⅣ、FN）分布完整与否及细胞粘附分子A－CAM表达高低与BAC淋巴结转移无关。     

PCR筛选阳性克隆方法的改进

ＰＣＲ筛选阳性克隆具有简便、快速的优点,但常发生假阳性错误。用与载体匹配的引物和目的的基因引物组合进行ＰＣＲ,可以消除假阳性,同时可以判断插入目的基因的方向。     

mRNA靶点筛选方法研究进展

mRNA靶点筛选问题是反义核酸领域的一个难题。近年来出现了多种筛选mRNA上可接近位点以确定靶位点的方法,包括mRNA实测分析法和计算机模拟分析两大类。其中mRNA实测分析法又包括多种针对自然折叠mRNA的实验分析技术;即基因walk技术,RNaseH作图技术、寡核苷酸微阵列技术,酶作图法确定二级结构技术,核酶导向型随机RNA库位点筛选技术和随机寡核苷酸库结合逆转录位点筛选技术。这些方法在鉴定RNA可接近位点及反义核酸的设计方面均有重要作用。