Meizhang Li

microRNA-375 inhibits colorectal cancer cells proliferation by downregulating JAK2/STAT3 and MAP3K8/ERK signaling pathways

MicroRNA-375 is involved in many types of alimentary system cancers. Our previous studies showed that microRNA-375 was significantly down-regulated in carcinoma tissues compared with para-carcinoma tissues, which strongly indicates that microRNA-375 might suppress the occurrence and development of colorectal cancer. However, the mechanism underlying the microRNA-375 regulation in colorectal cancer remains unclear. In this study, we first sorted out jak2, map3k8 and atg7 as microRNA-375 targeted genes from multiple databases, and found that jak2, map3k8 and their downstream genes stat3 and erk were up-regulated in carcinoma tissues. Secondly, we over-expressed microRNA-375 in colorectal cancer cell lines (HCT116, Caco2 and HT29). Our results showed that in microRNA-375 over-expressing cells, JAK2/STAT3 and MAP3K8/ERK proteins were down-regulated, cell proliferation was inhibited, cell migration rate did not change. There was no significant difference on ATG7 expression between the control group and microRNA-375 over-expressing HT29/Caco2 cells, whereas microRNA-375 down-regulated ATG7 specifically in HCT116 cells. Finally, we demonstrated that expressing microRNA-375 suppressed tumor formation in nude mice. In conclusion, microRNA-375 might function as a tumor-repressive gene to inhibit cell proliferation, mainly through targeting both JAK2/STAT3 and MAP3K8/ERK signaling pathways in colorectal cancer. These findings suggest miR-375 as a promising diagnostic marker and a therapeutic drug for colorectal cancer.

Nutrient deprivation-related OXPHOS/glycolysis interconversion via HIF-1α/C-MYC pathway in U251 cells.

Although the Warburg effect is a dominant metabolic phenotype observed in cancers, the metabolic changes and adaptation occurring in tumors have been demonstrated to extend beyond the Warburg effect and thus considered a secondary effect to the transformation process of carcinogenesis, including nutritional deficiencies. However, the role of nutritional deficiencies in this metabolic reprogramming (e. g., oxidative phosphorylation (OXPHOS)/glycolysis interconversion) is not completely known yet. Here, we showed that under regular culture condition, the proliferation of U251 cells, but not other tumor cell lines, preferentially performed the Warburg effect and was remarkably inhibited by oxamic acid which can inhibit the activity of lactate dehydrogenase (LDH); whereas under serum starvation, glycolysis was depressed, tricarboxylic acid cycle (TCA) was enhanced, and the activity of OXPHOS was reinforced to maintain cellular ATP content in a high level, but interestingly, we observed a decreased expression of reactive oxygen species (ROS). Moreover, the upregulated activity of mitochondrial complex I was confirmed by Western blots and showed that the mitochondrial-related protein, NDUFA9, NDUFB8, ND1, and VDAC1 were remarkably increased after serum starved. Mechanistically, nutritional deficiencies could reduce hypoxia-inducible factor α (HIF-1α) protein expression to increase C-MYC protein level, which in turn increased nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) transcription to enhance the activity of OXPHOS, suggesting that metabolic reprogramming by the changes of microenvironment during the carcinogenesis can provide some novel therapeutic clues to traditional cancer treatments.

Mesenchymal Stromal Cells: What Is the Mechanism in Acute Graft-Versus-Host Disease?

After more than a decade of preclinical and clinical development, therapeutic infusion of mesenchymal stromal cells is now a leading investigational strategy for the treatment of acute graft-versus-host disease (GVHD). While their clinical use continues to expand, it is still unknown which of their immunomodulatory properties contributes most to their therapeutic activity. Herein we describe the proposed mechanisms, focusing on the inhibitory activity of mesenchymal stromal cells (MSCs) at immunologic checkpoints. A deeper understanding of the mechanism of action will allow us to design more effective treatment strategies.

CXC chemokine CXCL12 and its receptor CXCR4 in tree shrews (Tupaia belangeri): structure, expression and function.

Chemokines are small secreted proteins functionally involved in the immune systems regulation of lymphocyte migration across numerous mammalian species. Given its growing popularity in immunological models, we investigated the structure and function of chemokine CXCL12 protein in tree shrews. We found that CXCL12 and its receptor CXCR4 in tree shrew had structural similarities to their homologous human proteins. Phylogenetic analysis supports the view that tree shrew is evolutionarily-close to the primates. Our results also showed that the human recombinant CXCL12 protein directly enhanced the migration of tree shrews lymphocytes in vitro, while AMD3100 enhanced the mobilization of hematopoietic progenitor cells (HPCs) from bone marrow into peripheral blood in tree shrew in vivo. Collectively, these findings suggested that chemokines in tree shrews may play the same or similar roles as those in humans, and that the tree shrew is a viable animal model for studying human immunological diseases.

PGC-1α regulates the cell cycle through ATP and ROS in CH1 cells

Peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) is a transcriptional co-activator involved in mitochondrial biogenesis, respiratory capacity, and oxidative phosphorylation (OXPHOS). PGC-1α plays an important role in cellular metabolism and is associated with tumorigenesis, suggesting an involvement in cell cycle progression. However, the underlying mechanisms mediating its involvement in these processes remain unclear. To elucidate the signaling pathways involved in PGC-1α function, we established a cell line, CH1 PGC-1α, which stably overexpresses PGC-1α. Using this cell line, we found that over-expression of PGC-1α stimulated extra adenosine triphosphate (ATP) and reduced reactive oxygen species (ROS) production. These effects were accompanied by up-regulation of the cell cycle checkpoint regulators CyclinD1 and CyclinB1. We hypothesized that ATP and ROS function as cellular signals to regulate cyclins and control cell cycle progression. Indeed, we found that reduction of ATP levels down-regulated CyclinD1 but not CyclinB1, whereas elevation of ROS levels down-regulated CyclinB1 but not CyclinD1. Furthermore, both low ATP levels and elevated ROS levels inhibited cell growth, but PGC-1α was maintained at a constant level. Together, these results demonstrate that PGC-1α regulates cell cycle progression through modulation of CyclinD1 and CyclinB1 by ATP and ROS. These findings suggest that PGC-1α potentially coordinates energy metabolism together with the cell cycle.中文概要目 的探讨在CH1 细胞中过氧化物酶体增殖物受体γ 共激活因子1α(PGC-1α)调控细胞周期时三磷 酸腺苷(ATP)和活性氧(ROS)的作用机制。创新点构建了稳定表达PGC-1α 的CH1 细胞株, 并系统 地研究了PGC-1α 调控细胞周期是通过ATP 和 ROS 调节CyclinD1 和CyclinB1 的行使功能。方 法以慢病毒质粒pBABE 为载体构建了PGC-1α 稳 定表达的CH1 PGC-1α 细胞株(PGC-1α), 同时 转染空质粒pBABE 作为对照(PB), 结合RNA 干扰CH1 PGC-1α 中PGC-1α 的过表达(Si), 测定了ATP 和ROS 水平。用流式细胞术检测了 细胞周期和免疫印迹检测了CyclinB1/D1 的表达, 并进一步分别用寡霉素抑制PGC-1α 细胞中的 ATP 生成, 用H2O2 处理细胞以增加外源ROS 水 平。然后检测ATP 和ROS 改变后, 对CyclinB1/D1 表达及细胞周期的影响, 以明确ATP 和ROS 是 否参与PGC-1α 对细胞周期的调控作用。结 论本实验成功构建了稳定表达PGC-1α 的细胞株 (图1 和图2a), 与PB 对照和RNA 干扰PGC-1α 比较, 过表达PGC-1α 具有升高ATP、降低ROS 和促进细胞周期的作用(图3 和图4)。进一步 用寡霉素抑制ATP 合成后发现CyclinD1 明显下 调(图5), 而加入H2O2 增加外源ROS 后发现 CyclinB1 显著上调(图6)。通过本实验我们提 出PGC-1α调控细胞周期是通过升高ATP水平抑 制CyclinD1 表达和降低ROS 水平促进CyclinB1 表达来实现。

Digital gene expression profiling analysis of DNA repair pathways in colon cancer stem population of HT29 cells

Cancer stem cells (CSCs) contribute to the relapse and development of new neoplasm lesions. While most available clinical approaches, such as chemical and radiation therapies, will kill the majority of cancer cells, they do not kill them all. Some resisting cells, like CSCs, are able to survive due to their excellent self-maintaining capabilities, even in challenging environments. In the present study, we investigated the mRNA level of DNA repair genes of colon CSCs from the HT29 cell line in response to single-strand damage and double-strand breaks, as well as the evident upregulation of key genes in base excision repair, mismatch repair, non-homologous end-joining, and homologous recombination pathways in these cells. Digital gene expression analysis identified upregulated genes in CD44+ HT29 cells that may play important roles in DNA repair. Our results reveal that colon CSCs bear efficient DNA repair abilities, which might explain the survival of colon CSCs after repeated chemical and radiation therapy.

MTERF1 regulates the oxidative phosphorylation activity and cell proliferation in HeLa cells

The mitochondrial transcription termination factor (MTERF) family is a group of highly conserved DNA-binding proteins composed of four key members, MTERF1-4. To date, several studies have investigated the binding sites of MTERF1 on mitochondrial genome and the regulation of mitochondrial gene transcription, but the more intricate connection between mitochondrial genes transcription regulation, mitochondrial oxidative phosphorylation (OXPHOS), and cell proliferation is still poorly understood. In this study, we constructed over-expression and knockdown vectors of MTERF1 that were transfected into HeLa cells to investigate the functions of MTERF1. Results showed that although MTERF1 is a positive regulatory factor of mitochondrial genes transcription, it had no significant effect on the replication of mitochondrial DNA. Over-expression of MTERF1 increased mitochondrial oxidative phosphorylation activity and promoted ATP synthesis, cyclin D1 expression, and cell proliferation, while its knockdown inhibited ATP synthesis, decreased cyclin D1 expression, and slowed the cell growth. These results suggested that MTERF1 may promote cell proliferation by regulating oxidative phosphorylation activity in HeLa cells. Ultimately, these findings create a foundation for further and more conclusive studies on the physiological functions of MTERF family by providing novel insights into the potential mechanisms underlying cell proliferation regulation.

All-Trans Retinoic Acid-Induced Deficiency of the Wnt/β-Catenin Pathway Enhances Hepatic Carcinoma Stem Cell Differentiation.

Retinoic acid (RA) is an important biological signal that directly differentiates cells during embryonic development and tumorigenesis. However, the molecular mechanism of RA-mediated differentiation in hepatic cancer stem cells (hCSCs) is not well understood. In this study, we found that mRNA expressions of RA-biosynthesis-related dehydrogenases were highly expressed in hepatocellular carcinoma. All-trans retinoic acid (ATRA) differentiated hCSCs through inhibiting the function of β-catenin in vitro. ATRA also inhibited the function of PI3K-AKT and enhanced GSK-3β-dependent degradation of phosphorylated β-catenin. Furthermore, ATRA and β-catenin silencing both increased hCSC sensitivity to docetaxel treatment. Our results suggest that targeting β-catenin will provide extra benefits for ATRA-mediated treatment of hepatic cancer patients.

Upregulation of chemokine CXCL10 enhances chronic pulmonary inflammation in tree shrew collagen-induced arthritis

Chronic pulmonary inflammation (CPI) gives rise to serious lung injuries in rheumatoid arthritis (RA) patients. However, the molecular mechanism underlying the pathogenesis of RA-associated CPI remains little understood. Here we established a novel tree shrew-based collagen-induced arthritis (TsCIA) model to study RA-associated CPI. Our results showed that typical CPI but not fibrosis developed pathologically in the TsCIA model. Furthermore, abnormal up-regulation of pulmonary chemokine CXCL10 was directly associated with lung damage. Specific blockage of CXCR3 (a CXCL10 receptor) significantly decreased the severity of CPI by decreasing the recruitment of inflammatory cells. Therefore, CXCL10 is proposed as a key player responsible for the development of TsCIA-associated CPI. Our findings also suggest that CXCR3 could be developed as a potential diagnosis biomarker for RA-associated CPI.

Conserved structure and function of chemokine CXCL8 between Chinese tree shrews and humans

Chemokines represent a superfamily of small secretion proteins that functionally mediate immune cell transmigration in normal or inflammatory conditions. Although anatomic and polygenetic evidence suggests that tree shrews are primate-like species, understanding of the structure and function of tree shrew chemokines has only just commenced. In this study, we cloned tree shrew chemokine CXCL8 and its cognate receptors. Predicted three-dimensional (3D) structures showed that binding domains in CXCL8 and CXCR1/2 were highly conserved between tree shrews and humans. We found that the human CXCL8 (hCXCL8) protein induced migration of tree shrew peripheral blood mononuclear cells (PBMCs) expressed by CXCR1/2 (tsCXCR1/2). Blocking interaction between hCXCL8 and tsCXCR1/2 with allosteric antagonists (reparixin and SB265610) significantly decreased tree shrew PBMC transmigration. Over-expressing tree shrew CXCR1 in human HEK 293 T cells further enhanced cellular in vitro transmigration. Similar to primate species, our findings suggest that CXCL8 and CXCR1/2 constitute a structurally- and functionally-conserved chemotaxis responsible for tree shrew immune activities.