SUMMARY Mesenchymal stromal cells (MSCs) tend to infiltrate into tumors and form a major component of the tumor microenvironment. These tumor-resident MSCs are known to affect tumor growth, but the mechanisms are largely unknown. We found that MSCs isolated from spontaneous lymphomas in mouse (L-MSCs) strikingly enhanced tumor growth in comparison to bone marrow MSCs (BM-MSCs). L-MSCs contributed to greater recruitment of CD11b+Ly6C+ monocytes, F4/80+ macrophages, and CD11b+Ly6G+ neutrophils to the tumor. Depletion of monocytes/macrophages, but not neutrophils, completely abolished tumor promotion of L-MSCs. Furthermore, L-MSCs expressed high levels of CCR2 ligands, and monocyte/macrophage accumulation and L-MSC-mediated tumor promotion were largely abolished in CCR2−/− mice. Intriguingly, TNFα-pretreated BM-MSCs mimicked L-MSCs in their chemokine production profile and ability to promote tumorigenesis of lymphoma, melanoma, and breast carcinoma. Therefore, our findings demonstrate that, in an inflammatory environment, tumor-resident MSCs promote tumor growth by recruiting monocytes/macrophages.

An imbalance between normal adipogenesis and osteogenesis by mesenchymal stem cells (MSCs) has been shown to be related to various human metabolic diseases, such as obesity and osteoporosis; however, the underlying mechanisms remain elusive. We found that the interaction between osteopontin (OPN), an arginine-glycine-aspartate-containing glycoprotein, and integrin αv/β1 plays a critical role in the lineage determination of MSCs. Although OPN is a well established marker during osteogenesis, its role in MSC differentiation is still unknown. Our study reveals that blockade of OPN function promoted robust adipogenic differentiation, while inhibiting osteogenic differentiation. Re-expression of OPN restored a normal balance between adipogenesis and osteogenesis in OPN-/- MSCs. Retarded bone formation by OPN-/- MSCs was also verified by in vivo implantation with hydroxyapatite-tricalcium phosphate (HA-TCP), a bone-forming matrix. The role of extracellular OPN in MSC differentiation was further demonstrated by supplementation and neutralization of OPN. Blocking well-known OPN receptors integrin αv/β1 but not CD44, also affected MSC differentiation. Further studies revealed that OPN inhibits the C/EBPs signaling pathway through integrin αv/β1. Consistent with these in vitro results, OPN-/- mice had a higher fat to total body weight ratio than did wild-type mice. Therefore, our study demonstrates a novel role for OPN-integrin αv/β1 in regulating MSC differentiation.

Cancer is a serious health issue in the world due to a large body of cancer-related human deaths, and there is no current treatment available to efficiently treat the disease as the tumor is often diagnosed at a serious stage. Moreover, Cancer cells are often resistant to chemotherapy, radiotherapy, and molecular-targeted therapy. Upon further knowledge of mechanisms of tumorigenesis, aggressiveness, metastasis, and resistance to treatments, it is necessary to detect the disease at an earlier stage and for a better response to therapy. The hippo pathway possesses the unique capacity to lead to tumorigenesis. Mutations and altered expression of its core components (MST1/2, LATS1/2, YAP and TAZ) promote the migration, invasion, malignancy of cancer cells. The biological significance and deregulation of it have received a large body of interests in the past few years. Further understanding of hippo pathway will be responsible for cancer treatment. In this review, we try to discover the function of hippo pathway in different diversity of cancers, and discuss how Hippo pathway contributes to other cellular signaling pathways. Also, we try to describe how microRNAs, circRNAs, and ZNFs regulate hippo pathway in the process of cancer. It is necessary to find new therapy strategies for cancer.

Mesenchymal stem cells (MSCs) have been demonstrated to be anti-inflammatory against various immune disorders through several factors, including indoleamine 2,3-dioxygenase (IDO) and TNF-stimulated gene 6 (TSG-6). However, little is known about the necessity for both of these key immunosuppressive factors. Here we employed the mouse lipopolysaccharide (LPS)-induced acute lung injury (ALI) model, and found that IDO is necessary to achieve the effect of human umbilical cord-derived MSC (hUC-MSC)-based treatment on ALI. Notably, when IDO was deleted or inhibited, the expression of TSG-6 was decreased. This specific IDO-mediated regulation of TSG-6 expression was found to be exerted through its metabolite, kynurenic acid (KYNA), as inhibition of KYNA production led to decreased TSG-6 expression. Importantly, KYNA pretreatment of human MSCs enhanced their therapeutic effect on ALI. Mechanistically, KYNA activates aryl hydrocarbon receptor (AhR), which directly binds to the TSG-6 promoter to enhance TSG-6 expression. Therefore, our study has uncovered a novel link between IDO and TSG-6, and demonstrates that a metabolite of IDO controls the TSG-6-mediated anti-inflammatory therapeutic effects of human MSCs.

Multiple sclerosis (MS) is a chronic and debilitating autoimmune disease, characterized by chronic inflammatory demyelination in the nervous tissue and subsequent neurological dysfunction. Spermidine, a natural polyamine, has been shown to affect inflammation in some experimental models. We show here that spermidine could alleviate experimental autoimmune encephalomyelitis (EAE), a model for MS, through regulating the infiltration of CD4+ T cells and macrophages in central nervous system. Unexpectedly, we found that spermidine treatment of MOG-specific T cells did not affect their pathogenic potency upon adaptive transfer; however, spermidine diminished the ability of macrophages in activating MOG-specific T cells ex vivo. Depletion of macrophages in diseased mice completely abolished the therapeutic effect of spermidine, indicating a critical role of spermidine-activated macrophages. Mechanistically, spermidine was found to specifically suppress the expression of interleukin-1beta (IL-1β), IL-12 and CD80 while enhance the expression of arginase 1 in macrophages. Interestingly, macrophages from spermidine-treated mice could also reverse EAE progression, while pretreatment of those macrophages with the arginase 1 inhibitor abrogated the therapeutic effect. Therefore, our studies revealed a critical role of macrophages in spermidine-mediated treatment on EAE and provided novel information for better management of MS.

Ethyl pyruvate has been shown to have anti-inflammatory properties in numerous cell culture and animal studies. In this series of experiments, we tested the hypothesis that ethyl pyruvate inhibits signaling by the pro-inflammatory transcription factor, NF-B. Ethyl pyruvate inhibited luciferase expression in lipopolysaccharide-stimulated murine macrophage-like RAW 264.7 cells transfected with an NF-B-dependent luciferase reporter vector. Ethyl pyruvate also decreased NF-B DNA-binding activity in lipopolysaccharide-stimulated RAW 264.7 cells and decreased lipopolysaccharide-induced expression of an NF-B-dependent gene, inducible nitric oxide synthase. Ethyl pyruvate had no effect on the degradation of IB␣ or IB␤ in lipopolysaccharide-stimulated RAW 264.7 cells, suggesting that ethyl pyruvate acts distally to this step in the activation of NF-B. In a cell-free system, binding of p50 homodimers to an NF-B consensus oligonucleotide sequence was unaffected by ethyl pyruvate over a wide range of concentrations, indicating that ethyl pyruvate probably does not modify or interact with the p50 subunit of NF-B. In contrast, ethyl pyruvate inhibited DNA binding by ectopically overexpressed wild-type p65 homodimers. However, ethyl pyruvate failed to inhibit the DNAbinding activity of homodimers of an overexpressed mutant form of a p65 with substitution of serine for cysteine 38. Taken together, these results suggest that ethyl pyruvate inhibits DNA-binding by covalently modifying p65 at Cys 38 . We conclude that some of the beneficial anti-inflammatory effects of ethyl pyruvate may be due to modification of p65, thereby inhibiting signaling via the NF-B pathway.

Shear stress, especially low shear stress (LowSS), plays an important role in vascular remodeling during atherosclerosis. Endothelial cells (ECs), which are directly exposed to shear stress, convert mechanical stimuli into intracellular signals and interact with the underlying vascular smooth muscle cells (VSMCs). The interactions between ECs and VSMCs modulate the LowSS-induced vascular remodeling. With the use of proteomic analysis, the protein profiles of rat aorta cultured under LowSS (5 dyn/cm 2 ) and normal shear stress (15 dyn/cm 2 ) were compared. By using Ingenuity Pathway Analysis to identify protein–protein association, a network was disclosed that involves two secretary molecules, PDGF-BB and TGF-β1, and three other linked proteins, lamin A, lysyl oxidase, and ERK 1/2. The roles of this network in cellular communication, migration, and proliferation were further studied in vitro by a cocultured parallel-plate flow chamber system. LowSS up-regulated migration and proliferation of ECs and VSMCs, increased productions of PDGF-BB and TGF-β1, enhanced expressions of lysyl oxidase and phospho-ERK1/2, and decreased Lamin A in ECs and VSMCs. These changes induced by LowSS were confirmed by using PDGF-BB recombinant protein, siRNA, and neutralizing antibody. TGF-β1 had similar influences on ECs as PDGF-BB, but not on VSMCs. Our results suggest that ECs convert the LowSS stimuli into up-regulations of PDGF-BB and TGF-β1, but these two factors play different roles in LowSS-induced vascular remodeling. PDGF-BB is involved in the paracrine control of VSMCs by ECs, whereas TGF-β1 participates in the feedback control from VSMCs to ECs.

The formin protein formin-like 1 (FMNL1) is highly restrictedly expressed in hematopoietic lineage-derived cells and has been previously identified as a tumor-associated antigen. However, function and regulation of FMNL1 are not well defined. We have identified a novel splice variant (FMNL1␥) containing an intron retention at the C terminus affecting the diaphanous autoinhibitory domain (DAD). FMNL1␥ is specifically located at the cell membrane and cortex in diverse cell lines. Similar localization of FMNL1 was observed for a mutant lacking the DAD domain (FMNL1⌬DAD), indicating that deregulation of autoinhibition is effective in FMNL1␥. Expression of both FMNL1␥ and FMNL1⌬DAD induces polarized nonapoptotic blebbing that is dependent on N-terminal myristoylation of FMNL1 but independent of Src and ROCK activity. Thus, our results describe N-myristoylation as a regulative mechanism of FMNL1 responsible for membrane trafficking potentially involved in a diversity of polarized processes of hematopoietic lineage-derived cells.Formins represent a protein family indispensable for many fundamental actin-dependent processes, including migration, vesicle trafficking, morphogenesis, and cytokinesis (1). Because these polarized processes are also involved in inflammation, deregulated proliferation, and metastasis, formins have been suggested to represent attractive drug targets for inflammatory and malignant diseases. Formin-like 1 (FMNL1) 3 is expressed restrictedly in hematopoietic lineagederived cells and overexpressed in malignant cells of different origin. This restricted expression suggests FMNL1 to be an attractive target for novel immunotherapies in malignant and inflammatory diseases (2, 3). However, function and regulation of FMNL1 are less well characterized. Previous work has shown involvement of FMNL1 in the reorientation of the microtubuleorganizing center toward the immunological synapse and cytotoxicity of T cells (4). The murine homolog FRL, which has 85% homology to the human counterpart, has been additionally shown to be involved in cell adhesion and motility of macrophages as well as Fc␥ receptor-mediated phagocytosis (5, 6). To date, it is not clear how these different membrane-associated processes are regulated.Formins are defined by a unique and highly conserved C-terminal formin homology (FH) 2 domain that mediates the effects on actin (7-11). The FH2 domain is proceeded by a proline-rich FH1 domain that binds with low micromolar affinity to profilin (12, 13). In a conserved subfamily of formins known as diaphanous-related formins (DRFs), the FH1 and FH2 domains are flanked by an array of regulatory domains at the N terminus and by a single C-terminal diaphanous autoregulatory domain (DAD) (14). The large N-terminal regulatory region includes a binding domain for small G proteins like RhoGTPase followed by an adjacent diaphanous-inhibitory domain (DID) and a dimerization domain (13,(15)(16)(17). The DAD, which comprised only a small stretch of amino acid residues, binds to the DID. Interaction of DA...