Membrane-derived vesicles (MV) are released from the surface of activated eucaryotic cells and exert pleiotropic effects on surrounding cells. Since the maintenance of pluripotency and undifferentiated propagation of embryonic stem (ES) cells in vitro requires tight cell to cell contacts and effective intercellular signaling, we hypothesize that MV derived from ES cells (ES-MV) express stem cell-specific molecules that may also support self-renewal and expansion of adult stem cells. To address this hypothesis, we employed expansion of hematopoietic progenitor cells (HPC) as a model. We found that ES-MV (10 μg/ml) isolated from murine ES cells (ES-D3) in serum-free cultures significantly (i) enhanced survival and improved expansion of murine HPC, (ii) upregulated the expression of early pluripotent (Oct-4, Nanog and Rex-1) and early hematopoietic stem cells (Scl, HoxB4 and GATA 2) markers in these cells, and (iii) induced phosphorylation of MAPK p42/44 and serine-threonine kinase AKT. Furthermore, molecular analysis revealed that ES-MV express Wnt-3 protein and are selectively highly enriched in mRNA for several pluripotent transcription factors as compared to parental ES cells. More important, this mRNA could be delivered by ES-MV to target cells and translated into the corresponding proteins. The biological effects of ES-MV were inhibited after heat inactivation or pretreatment with RNAse, indicating a major involvement of protein and mRNA components of ES-MV in the observed phenomena. We postulate that ES-MV may efficiently expand HPC by stimulating them with ES-MV expressed ligands (e.g., Wnt-3) as well as increase their pluripotency after horizontal transfer of ES-derived mRNA.

The alpha-chemokine stromal-derived factor (SDF)-1 and the G-protein-coupled seven-span transmembrane receptor CXCR4 axis regulates the trafficking of various cell types. In this review, we present the concept that the SDF-1-CXCR4 axis is a master regulator of trafficking of both normal and cancer stem cells. Supporting this is growing evidence that SDF-1 plays a pivotal role in the regulation of trafficking of normal hematopoietic stem cells (HSCs) and their homing/retention in bone marrow. Moreover, functional CXCR4 is also expressed on nonhematopoietic tissue-committed stem/progenitor cells (TCSCs); hence, the SDF-1-CXCR4 axis emerges as a pivotal regulator of trafficking of various types of stem cells in the body. Furthermore, because most if not all malignancies originate in the stem/progenitor cell compartment, cancer stem cells also express CXCR4 on their surface and, as a result, the SDF-1-CXCR4 axis is also involved in directing their trafficking/metastasis to organs that highly express SDF-1 (e.g., lymph nodes, lungs, liver, and bones). Hence, we postulate that the metastasis of cancer stem cells and trafficking of normal stem cells involve similar mechanisms, and we discuss here the common molecular mechanisms involved in these processes. Finally, the responsiveness of CXCR4+ normal and malignant stem cells to an SDF-1 gradient may be regulated positively/primed by several small molecules related to inflammation which enhance incorporation of CXCR4 into membrane lipid rafts, or may be inhibited/blocked by small CXCR4 antagonist peptides. Consequently, strategies aimed at modulating the SDF-1-CXCR4 axis could have important clinical applications both in regenerative medicine to deliver normal stem cells to the tissues/organs and in clinical hematology/oncology to inhibit metastasis of cancer stem cells.

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide. Globally, it is currently the most common liver disease and is estimated to affect up to 25% of the population. In the first stage, NAFLD is characterized by simple hepatic steatosis (NAFL, nonalcoholic fatty liver) that might progress to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis or hepatocellular carcinoma. In this review, we discuss the global burden of NAFLD, together with future perspectives on how this epidemic could be restrained. There is also an urgent need for the development of new medical strategies for NAFLD patients. We aim to present the beneficial effects of life-style modifications that should be advised to both non-obese and obese NAFLD patients. Since there are currently no medications directly used for the treatment of more advanced NAFLD stages, the central part of this review summarizes ongoing and recently completed clinical trials testing promising drugs for NASH resolution. The marketing of new therapeutic agents would greatly increase the odds of reducing the global burden of NAFLD.

Rhabdomyosarcoma frequently infiltrates bone marrow and this process involves the stromal-derived factor-1 (SDF-1)–CXCR4 axis. Because leukemia inhibitory factor (LIF), like SDF-1, is secreted by bone marrow stroma and directs the regeneration of skeletal muscles, we examined whether the LIF–LIF receptor (LIF-R) axis affects the biology of rhabdomyosarcoma cells. We found that in rhabdomyosarcoma cells, LIF stimulates the following: (a) phosphorylation of mitogen-activated protein kinase p42/44, AKT, and signal transducers and activators of transcription 3, (b) adhesion and chemotaxis, and (c) increased resistance to cytostatics. To compare the biological effects of LIF versus SDF-1, we examined the RH30 cell line, which is highly responsive to both ligands, and found that the chemotaxis of these cells is significantly reduced when the inhibitors of both receptors (T140 for CXCR4 and gp190 blocking antibody for LIF-R) are added simultaneously. Subsequently, by using repetitive chemotaxis to LIF or SDF-1, we selected from the RH30 line subpopulations of cells that respond to LIF but not SDF-1 (RH30-L) or to SDF-1 but not LIF (RH30-S). We found that (a) RH30-L cells seed better to the bone marrow, liver, and lymph nodes of immunodeficient mice than RH30-S cells and (b) mice inoculated i.m. with the RH30-L cells had more rhabdomyosarcoma cells in the bone marrow and lung after 6 weeks. Thus, we present the first evidence that the LIF–LIF-R axis may direct rhabdomyosarcoma metastasis. Further, because we showed that the in vivo metastasis of RH30 cells is inhibited by small interfering RNA against LIF-R, molecular targeting of this axis could become a new strategy to control the metastasis of rhabdomyosarcoma. [Cancer Res 2007;67(5):2131–40]

Clear cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer and it forms highly vascularized tumors. The monocyte endoribonuclease MCPIP1 negatively regulates inflammation by degrading mRNA encoding proinflammatory cytokines, such as IL6, IL1, and IL12. MCPIP1 is also a negative regulator of NFκB and AP1 activity and it influences a broad range of miRNA activities. Here we report that MCPIP1 protein levels are decreased during renal cancer progression. In patient-derived tumors and xenografts established in NOD-SCID or nude mice, low MCPIP1 levels correlated strongly with increased proliferation, tumor outgrowth, and vascularity. MCPIP1 activity regulated secretion of VEGF, IL8, and CXCL12 leading to chemotaxis of microvascular endothelial cells, phosphorylation of VE-cadherin, and increased vascular permeability. Mechanistic investigations showed that MCPIP1 regulated ccRCC cell motility, lung metastasis, and mesenchymal phenotype by regulating key elements in the EMT signaling axis. Overall, our results illuminate how MCPIP1 serves as a key nodal point in coordinating tumor growth, angiogenesis, and metastatic spread in ccRCC. Cancer Res; 77(18); 4905–20. ©2017 AACR.