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Phosphoinositide 3-kinase (PI3K)-dependent signalling regulates a wide variety of cellular functions including proliferation and differentiation. Disruption of class I(A) PI3K isoforms has implicated PI3K-mediated signalling in development of the early embryo and lymphohaemopoietic system. We have used embryonic stem (ES) cells as an in vitro model to study the involvement of PI3K-dependent signalling during early development and haemopoiesis. Both pharmacological inhibition and genetic manipulation of PI3K-dependent signalling demonstrate that PI3K-mediated signals, most likely via 3-phosphoinositide-dependent protein kinase 1 (PDK1), are required for proliferation of cells within developing embryoid bodies (EBs). Surprisingly, the haemopoietic potential of EB-derived cells was not blocked upon PI3K inhibition but rather enhanced, correlating with modest increases in expression of haemopoietic marker genes. By contrast, PDK1-deficient EB-derived progeny failed to generate terminally differentiated haemopoietic lineages. This deficiency appeared to be due to a requirement for PI3K signalling during the proliferative phase of blast-colony-forming cell (BL-CFC) expansion, rather than as a result of effects on differentiation per se. We also demonstrate that PI3K-dependent signalling is required for optimal generation of erythroid and myeloid progenitors and their differentiation into mature haemopoietic colony types. These data demonstrate that PI3K-dependent signals play important roles at different stages of haemopoietic development.

Ubiquitously acting chromatin opening elements (UCOEs) consist of methylation-free CpG islands encompassing dual divergently transcribed promoters of housekeeping genes that have been shown to confer resistance to transcriptional silencing and to produce consistent and stable transgene expression in tissue culture systems. To develop improved strategies for hematopoietic cell gene therapy, we have assessed the potential of the novel human HNRPA2B1-CBX3 UCOE (A2UCOE) within the context of a self-inactivating (SIN) lentiviral vector. Unlike viral promoters, the enhancer-less A2UCOE gave rise to populations of cells that expressed a reporter transgene at a highly reproducible level. The efficiency of expression per vector genome was also markedly increased in vivo compared with vectors incorporating either spleen focus-forming virus (SFFV) or cytomegalovirus (CMV) promoters, suggesting a relative resistance to silencing. Furthermore, an A2UCOE-IL2RG vector fully restored the IL-2 signaling pathway within IL2RG-deficient human cells in vitro and successfully rescued the X-linked severe combined immunodeficiency (SCID-X1) phenotype in a mouse model of this disease. These data indicate that the A2UCOE displays highly reliable transcriptional activity within a lentiviral vector, largely overcoming insertion-site position effects and giving rise to therapeutically relevant levels of gene expression. These properties are achieved in the absence of classic enhancer activity and therefore may confer a high safety profile.

Disruption of pathways leading to programmed cell death plays a major role in most malignancies, including multiple myeloma (MM). ABT-737 is a BH3 mimetic small-molecule inhibitor that binds with high affinity to Bcl-2 and Bcl-xL, preventing the sequestration of proapoptotic molecules and shifting the cell survival/apoptosis balance toward apoptosis induction. In this study, we show that ABT-737 is cytotoxic to MM cell lines, including those resistant to conventional therapies, and primary tumor cells. Flow cytometric analysis of intracellular levels of Bcl-2 family proteins demonstrates a clear inversion of the Bax/Bcl-2 ratio leading to induction of apoptosis. Activation of the mitochondrial apoptosis pathway was indicated by mitochondrial membrane depolarization and caspase cleavage. Additionally, several signaling pathways known to be important for MM cell survival are disrupted following treatment with ABT-737. The impact of ABT-737 on survival could not be overcome by the addition of interleukin-6, vascular endothelial growth factor or insulin-like growth factor, suggesting that ABT-737 may be effective in preventing the growth and survival signals provided by the microenvironment. These data indicate that therapies targeting apoptotic pathways may be effective in MM treatment and warrant clinical evaluation of ABT-737 and similar drugs alone or in combination with other agents in the setting of MM.

BACKGROUND: ALDH(br) cells express high aldehyde dehydrogenase (ALDH) activity and have progenitor cell activity in several contexts. We characterized human BM ALDH(br) cells to determine whether cell sorting based on ALDH activity isolates potentially useful populations for cell therapy. METHOD: We measured the expression of ALDH and cell-surface Ag by flow cytometry and compared the ability of sorted ALDH(br), and BM populations remaining after ALDH(br) cells were removed (ALDH(dim) populations), to develop into several cell lineages in culture. RESULTS: The ALDH(br) population comprised 1.2+/-0.8% (mean+/-SD, n=30) nucleated cells and was enriched in cells expressing CD34, CD117, CD105, CD127, CD133 and CD166, and in primitive CD34(+) CD38(-) and CD34(+) CD133(+) progenitors. Most of the CD34(+) and CD133(+) cells were ALDH(dim). ALDH(br) populations had 144-fold more hematopoietic colony-forming activity than ALDH(dim) cells and included all megakaryocyte progenitors. ALDH(br) populations readily established endothelial cell monolayers in cultures. Cells generating endothelial colonies in 7 days were 435-fold more frequent in ALDH(br) than ALDH(dim) populations. CFU-F were 9.5-fold more frequent in ALDH(br) than ALDH(dim) cells, and ALDH(br) cells gave rise to multipotential mesenchymal cell cultures that could be driven to develop into adipocytes, osteoblasts and chondrocytes. DISCUSSION: Hematopoietic, endothelial and mesenchymal progenitor cells can be isolated simultaneously from human BM by cell sorting based on ALDH activity. BM ALDH(br) populations may be useful in several cell therapy applications.

UNLABELLED The differentiation capacity of human embryonic stem cells (hESCs) holds great promise for therapeutic applications. We report a novel three-stage method to efficiently direct the differentiation of human embryonic stem cells into hepatic cells in serum-free medium. Human ESCs were first differentiated into definitive endoderm cells by 3 days of Activin A treatment. Next, the presence of fibroblast growth factor-4 and bone morphogenetic protein-2 in the culture medium for 5 days induced efficient hepatic differentiation from definitive endoderm cells. Approximately 70% of the cells expressed the hepatic marker albumin. After 10 days of further in vitro maturation, these cells expressed the adult liver cell markers tyrosine aminotransferase, tryptophan oxygenase 2, phosphoenolpyruvate carboxykinase (PEPCK), Cyp7A1, Cyp3A4 and Cyp2B6. Furthermore, these cells exhibited functions associated with mature hepatocytes including albumin secretion, glycogen storage, indocyanine green, and low-density lipoprotein uptake, and inducible cytochrome P450 activity. When transplanted into CCl4 injured severe combined immunodeficiency mice, these cells integrated into the mouse liver and expressed human alpha-1 antitrypsin for at least 2 months. In addition, we found that the hESC-derived hepatic cells were readily infected by human immunodeficiency virus-hepatitis C virus pseudotype viruses. CONCLUSION We have developed an efficient way to direct the differentiation of human embryonic stem cells into cells that exhibit characteristics of mature hepatocytes. Our studies should facilitate searching the molecular mechanisms underlying human liver development, and form the basis for hepatocyte transplantation and drug tests.

The pancreatic adenocarcinoma is an aggressive and devastating disease, which is characterized by invasiveness, rapid progression, and profound resistance to actual treatments, including chemotherapy and radiotherapy. At the moment, surgical resection provides the best possibility for long-term survival, but is feasible only in the minority of patients, when advanced disease chemotherapy is considered, although the effects are modest. Several studies have shown that thyroid hormone, 3,3',5-triiodo-l-thyronine (T(3)) is able to promote or inhibit cell proliferation in a cell type-dependent manner. The aim of the present study is to investigate the ability of T(3) to reduce the cell growth of the human pancreatic duct cell lines chosen, and to increase the effect of chemotherapeutic drugs at conventional concentrations. Three human cell lines hPANC-1, Capan1, and HPAC have been used as experimental models to investigate the T(3) effects on pancreatic adenocarcinoma cell proliferation. The hPANC-1 and Capan1 cell proliferation was significantly reduced, while the hormone treatment was ineffective for HPAC cells. The T(3)-dependent cell growth inhibition was also confirmed by fluorescent activated cell sorting analysis and by cell cycle-related molecule analysis. A synergic effect of T(3) and chemotherapy was demonstrated by cell kinetic experiments performed at different times and by the traditional isobologram method. We have showed that thyroid hormone T(3) and its combination with low doses of gemcitabine (dFdCyd) and cisplatin (DDP) is able to potentiate the cytotoxic action of these chemotherapic drugs. Treatment with 5-fluorouracil was, instead, largely ineffective. In conclusion, our data support the hypothesis that T(3) and its combination with dFdCyd and DDP may act in a synergic way on adenopancreatic ductal cells.

In order to investigate the biologic processes underlying and resulting from the megakaryocytic hyperplasia that characterizes idiopathic myelofibrosis (IMF), peripheral blood CD34+ cells isolated from patients with IMF, polycythemia vera (PV), and G-CSF-mobilized healthy volunteers were cultured in the presence of stem cell factor and thrombopoietin. IMF CD34+ cells generated 24-fold greater numbers of megakaryocytes (MKs) than normal CD34+ cells. IMF MKs were also shown to have a delayed pattern of apoptosis and to overexpress the antiapoptotic protein bcl-xL. MK hyperplasia in IMF is, therefore, likely a consequence of both the increased ability of IMF progenitor cells to generate MKs and a decreased rate of MK apoptosis. Media conditioned (CM) by CD61+ cells generated in vitro from CD34+ cells were then assayed for the levels of growth factors and proteases. Higher levels of transforming growth factor-beta (TGF-beta) and active matrix metalloproteinase-9 (MMP9) were observed in media conditioned with IMF CD61+ cells than normal or PV CD61+ cells. Both normal and IMF CD61+ cells produced similar levels of VEGF. MK-derived TGF-B and MMP-9, therefore, likely contribute to the development of many pathological epiphenomena associated with IMF.

Aldehyde dehydrogenase (ALDH) activity is used to define normal hematopoietic stem cell (HSC), but its link to leukemic stem cells (LSC) in acute myeloid leukemia (AML) is currently unknown. We hypothesize that ALDH activity in AML might be correlated with the presence of LSC. Fifty-eight bone marrow (BM) samples were collected from AML (n=43), acute lymphoblastic leukemia (ALL) (n=8) and normal cases (n=7). In 14 AML cases, a high SSC(lo)ALDH(br) cell population was identified (ALDH(+)AML) (median: 14.89%, range: 5.65-48.01%), with the majority of the SSC(lo)ALDH(br) cells coexpressing CD34(+). In another 29 cases, there was undetectable (n=23) or rare (textless or =5%) (n=6) SSC(lo)ALDH(br) population (ALDH(-)AML). Among other clinicopathologic variables, ALDH(+)AML was significantly associated with adverse cytogenetic abnormalities. CD34(+) BM cells from ALDH(+)AML engrafted significantly better in NOD/SCID mice (ALDH(+)AML: injected bone 21.11+/-9.07%; uninjected bone 1.52+/-0.75% vs ALDH(-)AML: injected bone 1.77+/-1.66% (P=0.05); uninjected bone 0.23+/-0.23% (P=0.03)) with the engrafting cells showing molecular and cytogenetic aberrations identical to the original clones. Normal BM contained a small SSC(lo)ALDH(br) population (median: 2.92%, range: 0.92-5.79%), but none of the ALL cases showed this fraction. In conclusion, SSC(lo)ALDH(br) cells in ALDH(+)AML might denote primitive LSC and confer an inferior prognosis in patients.

Protein geranylgeranyltransferase type I (GGTase-I) is responsible for the posttranslational lipidation of CAAX proteins such as RHOA, RAC1, and cell division cycle 42 (CDC42). Inhibition of GGTase-I has been suggested as a strategy to treat cancer and a host of other diseases. Although several GGTase-I inhibitors (GGTIs) have been synthesized, they have very different properties, and the effects of GGTIs and GGTase-I deficiency are unclear. One concern is that inhibiting GGTase-I might lead to severe toxicity. In this study, we determined the effects of GGTase-I deficiency on cell viability and K-RAS-induced cancer development in mice. Inactivating the gene for the critical beta subunit of GGTase-I eliminated GGTase-I activity, disrupted the actin cytoskeleton, reduced cell migration, and blocked the proliferation of fibroblasts expressing oncogenic K-RAS. Moreover, the absence of GGTase-I activity reduced lung tumor formation, eliminated myeloproliferative phenotypes, and increased survival of mice in which expression of oncogenic K-RAS was switched on in lung cells and myeloid cells. Interestingly, several cell types remained viable in the absence of GGTase-I, and myelopoiesis appeared to function normally. These findings suggest that inhibiting GGTase-I may be a useful strategy to treat K-RAS-induced malignancies.

A causative relationship between chronic inflammation and cancer has been postulated for many years, and clinical observations and laboratory experiments support the hypothesis that inflammation contributes to tumor onset and progression. However, the precise mechanisms underlying the relationship are not known. We recently reported that the proinflammatory cytokine, interleukin-1beta, induces the accumulation and retention of myeloid-derived suppressor cells (MDSC), which are commonly found in many patients and experimental animals with cancer and are potent suppressors of adaptive and innate immunity. This finding led us to hypothesize that inflammation leads to cancer through the induction of MDSC, which inhibit immunosurveillance and thereby allow the unchecked persistence and proliferation of premalignant and malignant cells. We now report that host MDSC have receptors for prostaglandin E2 (PGE2) and that E-prostanoid receptor agonists, including PGE2, induce the differentiation of Gr1(+)CD11b(+) MDSC from bone marrow stem cells, whereas receptor antagonists block differentiation. BALB/c EP2 knockout mice inoculated with the spontaneously metastatic BALB/c-derived 4T1 mammary carcinoma have delayed tumor growth and reduced numbers of MDSC relative to wild-type mice, suggesting that PGE2 partially mediates MDSC induction through the EP2 receptor. Treatment of 4T1-tumor-bearing wild-type mice with the cyclooxygenase 2 inhibitor, SC58236, delays primary tumor growth and reduces MDSC accumulation, further showing that PGE2 induces MDSC and providing a therapeutic approach for reducing this tumor-promoting cell population.

Here we describe a simple and efficient protocol for derivation of germline chimera-competent mouse embryonic stem cells (mESCs) from embryonic day 3.5 (E3.5) blastocysts. The protocol involves the use of early-passage mouse embryonic fibroblast feeders (MEF) and the alternation of fetal bovine serum- and serum replacement (SR)-containing media. As compared to other available protocols for mESCs derivation, our protocol differs in the combination of commercial availability of all reagents, technical simplicity and high efficiency. mESC lines are derived with approximately 50% efficiency (50 independent mESC lines derived from 96 blastocysts). We believe that this protocol could be a good starting point for (i) setting up the derivation of mESC lines in a laboratory and (ii) incorporating further steps to improve efficiency or adapt the protocol to other applications. The whole process (from blastocyst extraction to the freezing of mESC line) usually takes between 15 and 20 d.

Dendritic cells (DCs) act as a portal for invasion by human immunodeficiency virus type-1 (HIV-1). Here, we investigated whether virion-incorporated host cell membrane proteins can affect virus replication in DC-T-cell cocultures. Using isogenic viruses either devoid of or bearing host-derived leukocyte function-associated antigen 1 (LFA-1), we showed that HIV-1 production is augmented when LFA-1-bearing virions are used compared to that for viral entities lacking this adhesion molecule. This phenomenon was observed in immature monocyte-derived DCs (IM-MDDCs) only and not in DCs displaying a mature phenotype. The increase is not due to higher virus production in responder CD4(+) T cells but rather is linked with a more important productive infection of IM-MDDCs. We provided evidence that virus-associated host LFA-1 molecules do not affect a late event in the HIV-1 life cycle but rather exert an effect on an early step in virus replication. We demonstrated that the enhancement of productive infection of IM-MDDCs that is conferred by virus-anchored host LFA-1 involves the protein kinase A (PKA) and PKC signal transduction pathways. The biological significance of this phenomenon was established by performing experiments with virus stocks produced in primary human cells and anti-LFA-1 antibodies. Together, our results indicate that the association between some virus-bound host proteins and their natural cognate ligands can modulate de novo HIV-1 production by IM-MDDCs. Therefore, the additional interactions between virus-bound host cell membrane constituents and counter receptors on the surfaces of DCs can influence HIV-1 replication in IM-MDDC-T-cell cocultures.