A function-blocking CD47 antibody suppresses stem cell and EGF signaling in triple-negative breast cancer.

CD47 is a signaling receptor for thrombospondin-1 and the counter-receptor for signal-regulatory protein-α (SIRPα). By inducing inhibitory SIRPα signaling, elevated CD47 expression by some cancers prevents macrophage phagocytosis. The anti-human CD47 antibody B6H12 inhibits tumor growth in several xenograft models, presumably by preventing SIRPα engagement.

Variations in Glycogen Synthesis in Human Pluripotent Stem Cells with Altered Pluripotent States.

Human pluripotent stem cells (hPSCs) represent very promising resources for cell-based regenerative medicine. It is essential to determine the biological implications of some fundamental physiological processes (such as glycogen metabolism) in these stem cells. In this report, we employ electron, immunofluorescence microscopy, and biochemical methods to study glycogen synthesis in hPSCs.

CD47 signaling regulates the immunosuppressive activity of VEGF in T cells.

Thrombospondin-1 (TSP1) inhibits angiogenesis, in part, by interacting with the ubiquitous cell-surface receptor CD47. In endothelial cells, CD47 interacts directly with vascular endothelial growth factor receptor (VEGFR)-2, and TSP1 inhibits VEGFR2 phosphorylation and signaling by disrupting this association. We show that CD47 similarly associates with and regulates VEGFR2 in T cells.

Telomerase variant A279T induces telomere dysfunction and inhibits non-canonical telomerase activity in esophageal carcinomas.

Background: Although implicated in the pathogenesis of several chronic inflammatory disorders and hematologic malignancies, telomerase mutations have not been thoroughly characterized in human cancers. The present study was performed to examine the frequency and potential clinical relevance of telomerase mutations in esophageal carcinomas.

Methods: Sequencing techniques were used to evaluate mutational status of telomerase reverse transcriptase (TERT) and telomerase RNA component (TERC) in neoplastic and adjacent normal mucosa from 143 esophageal cancer (EsC) patients.

Wnt and the cancer niche: paracrine interactions with gastrointestinal cancer cells undergoing asymmetric cell division.

Objective: Stem-like cancer cells contribute to cancer initiation and maintenance. Stem cells can self-renew by asymmetric cell division (ACD). ACD with non-random chromosomal cosegregation (ACD-NRCC) is one possible self-renewal mechanism.

Biological profile of the less lipophilic and synthetically more accessible bryostatin 7 closely resembles that of bryostatin 1.

The bryostatins are a group of 20 macrolides isolated by Pettit and co-workers from the marine organism Bugula neritina. Bryostatin 1, the flagship member of the family, has been the subject of intense chemical and biological investigations due to its remarkably diverse biological activities, including promising indications as therapy for cancer, Alzheimer's disease, and HIV. Other bryostatins, however, have attracted far less attention, most probably due to their relatively low natural abundance and associated scarcity of supply.

N-methyl-substituted fluorescent DAG-indololactone isomers exhibit dramatic differences in membrane interactions and biological activity.

N-methyl-substituted diacylglycerol-indololactones (DAG-indololactones) are newly synthesized effectors of protein kinase C (PKC) isoforms and exhibit substantial selectivity between RasGRP3 and PKCα. We present a comprehensive analysis of membrane interactions and biological activities of several DAG-indololactones. Translocation and binding activity assays underline significant variations between the PKC translocation characteristics affected by the ligands as compared to their binding activities.

Molecular basis for failure of "atypical" C1 domain of Vav1 to bind diacylglycerol/phorbol ester.

C1 domains, the recognition motif of the second messenger diacylglycerol and of the phorbol esters, are classified as typical (ligand-responsive) or atypical (not ligand-responsive). The C1 domain of Vav1, a guanine nucleotide exchange factor, plays a critical role in regulation of Vav activity through stabilization of the Dbl homology domain, which is responsible for exchange activity of Vav. Although the C1 domain of Vav1 is classified as atypical, it retains a binding pocket geometry homologous to that of the typical C1 domains of PKCs.

Tumor-initiating label-retaining cancer cells in human gastrointestinal cancers undergo asymmetric cell division.

Label-retaining cells (LRCs) have been proposed to represent adult tissue stem cells. LRCs are hypothesized to result from either slow cycling or asymmetric cell division (ACD). However, the stem cell nature and whether LRC undergo ACD remain controversial.

Exosomes released by K562 chronic myeloid leukemia cells promote angiogenesis in a Src-dependent fashion.

Exosomes, microvesicles of endocytic origin released by normal and tumor cells, play an important role in cell-to-cell communication. Angiogenesis has been shown to regulate progression of chronic myeloid leukemia (CML). The mechanism through which this happens has not been elucidated.

Some phorbol esters might partially resemble bryostatin 1 in their actions on LNCaP prostate cancer cells and U937 leukemia cells.

Phorbol 12-myristate 13-acetate (PMA) and bryostatin 1 are both potent protein kinase C (PKC) activators. In LNCaP human prostate cancer cells, PMA induces tumor necrosis factor alpha (TNFα) secretion and inhibits proliferation; bryostatin 1 does not, and indeed blocks the response to PMA. This difference has been attributed to bryostatin 1 not localizing PKCδ to the plasma membrane.

The synthetic bryostatin analog Merle 23 dissects distinct mechanisms of bryostatin activity in the LNCaP human prostate cancer cell line.

Bryostatin 1 has attracted considerable attention both as a cancer chemotherapeutic agent and for its unique activity. Although it functions, like phorbol esters, as a potent protein kinase C (PKC) activator, it paradoxically antagonizes many phorbol ester responses in cells. Because of its complex structure, little is known of its structure-function relations.

Thrombospondin-1 inhibits VEGF receptor-2 signaling by disrupting its association with CD47.

Thrombospondin-1 (TSP1) can inhibit angiogenic responses directly by interacting with VEGF and indirectly by engaging several endothelial cell TSP1 receptors. We now describe a more potent mechanism by which TSP1 inhibits VEGF receptor-2 (VEGFR2) activation through engaging its receptor CD47. CD47 ligation is known to inhibit downstream signaling targets of VEGFR2, including endothelial nitric-oxide synthase and soluble guanylate cyclase, but direct effects on VEGFR2 have not been examined.

The skin cancer chemotherapeutic agent ingenol-3-angelate (PEP005) is a substrate for the epidermal multidrug transporter (ABCB1) and targets tumor vasculature.

Ingenol-3-angelate (Ing3A), extracted from Euphorbia peplus, is currently in clinical trials for eradicating basal cell carcinoma, actinic keratosis, and squamous cell carcinoma (SCC) in situ by topical application. Although structurally related to phorbol esters and a protein kinase C activator, topical Ing3A, but not phorbol 12-myristate 13-acetate (PMA), inhibited the growth of subcutaneous tumors derived from PAM212 (mouse SCC) and B16 (mouse melanoma). Ing3A and PMA both induced acute neutrophilic inflammation on mouse skin, but only Ing3A caused subcutaneous hemorrhage and vascular damage.

Characterization of the differential roles of the twin C1a and C1b domains of protein kinase C-delta.

Classic and novel protein kinase C (PKC) isozymes contain two zinc finger motifs, designated "C1a" and "C1b" domains, which constitute the recognition modules for the second messenger diacylglycerol (DAG) or the phorbol esters. However, the individual contributions of these tandem C1 domains to PKC function and, reciprocally, the influence of protein context on their function remain uncertain. In the present study, we prepared PKCdelta constructs in which the individual C1a and C1b domains were deleted, swapped, or substituted for one another to explore these issues.

Disruption of microfilaments by cytochalasin B decreases accumulation of cisplatin in human epidermal carcinoma and liver carcinoma cell lines.

Background: Although cisplatin is a frequently used cancer chemotherapeutic drug, its effectiveness is hindered by the development of resistance in cancer cells. In order to understand the reason(s) for this resistance, the mechanism of uptake of cisplatin into cells must be characterized. While several previous studies showed structural differences between cisplatin-sensitive and resistant cells, the influence of microfilaments, known to affect transport of molecules into cells, and the influence of certain biophysical characteristics of the plasma membrane needed clarification.

Conformationally constrained analogues of diacylglycerol (DAG). 28. DAG-dioxolanones reveal a new additional interaction site in the C1b domain of PKC delta.

Diacylglycerol (DAG) lactones have provided a powerful platform for structural exploration of the interactions between ligands and the C1 domains of protein kinase C (PKC). In this study, we report that DAG-dioxolanones, novel derivatives of DAG-lactones, exploit an additional point of contact (glutamine 27) in their binding with the C1b domain of PKC delta. Mutation of this point of contact to glutamate selectively impairs binding of the DAG-dioxolanones compared to that of the corresponding DAG-lactones (1200- to 3000-fold versus 35- to 55-fold, respectively).

Artificially introduced aneuploid chromosomes assume a conserved position in colon cancer cells.

Background: Chromosomal aneuploidy is a defining feature of carcinomas. For instance, in colon cancer, an additional copy of Chromosome 7 is not only observed in early pre-malignant polyps, but is faithfully maintained throughout progression to metastasis. These copy number changes show a positive correlation with average transcript levels of resident genes.

Conformationally constrained analogues of diacylglycerol (DAG). 27. Modulation of membrane translocation of protein kinase C (PKC) isozymes alpha and delta by diacylglycerol lactones (DAG-lactones) containing rigid-rod acyl groups.

Highly rigid and geometrically well-defined rods composed of ethynylene-substituted aromatic spacers [oligo(p-phenyleneethynylene), OPE] were incorporated as acyl moieties on diacylglycerol lactones (DAG-lactones) and investigated for their ability to bind to protein kinase C (PKC) and translocate PKC alpha and delta isoforms to plasma and internal membranes. The kinetics of PKC translocation were correlated with biological responses, viz. ERK phosphorylation, induction of IL-6 secretion, inhibition of cell proliferation, and induction of cellular attachment, that display very different time courses.

Effects on ligand interaction and membrane translocation of the positively charged arginine residues situated along the C1 domain binding cleft in the atypical protein kinase C isoforms.

The C1 domain zinc finger structure is highly conserved among the protein kinase C (PKC) superfamily members. As the interaction site for the second messenger sn-1,2-diacylglycerol (DAG) and for the phorbol esters, the C1 domain has been an important target for developing selective ligands for different PKC isoforms. However, the C1 domains of the atypical PKC members are DAG/phorbol ester-insensitive.

Multispectral imaging of clinically relevant cellular targets in tonsil and lymphoid tissue using semiconductor quantum dots.

Determination of the expression and spatial distribution of molecular epitopes, or antigens, in patient tissue specimens has substantially improved the pathologist's ability to classify disease processes. Certain disease pathophysiologies are marked by characteristic increased or decreased expression of developmentally controlled antigens, defined as Cluster of Differentiation markers, that currently form the foundation for understanding lymphoid malignancies. While chromogens and organic fluorophores have been utilitized for some time in immunohistochemical analyses, developments in synthetic, inorganic fluorophore semiconductors, namely quantum dots, offer a versatile alternative reporter system.

Melanosomal sequestration of cytotoxic drugs contributes to the intractability of malignant melanomas.

Multidrug resistance mechanisms underlying the intractability of malignant melanomas remain largely unknown. In this study, we demonstrate that the development of multidrug resistance in melanomas involves subcellular sequestration of intracellular cytotoxic drugs such as cis-diaminedichloroplatinum II (cisplatin; CDDP). CDDP is initially sequestered in subcellular organelles such as melanosomes, which significantly reduces its nuclear localization when compared with nonmelanoma/KB-3-1 epidermoid carcinoma cells.

Kinetics of penetration influence the apparent potency of vanilloids on TRPV1.

Evidence that the ligand binding site of TRPV1 lies on the inner face of the plasma membrane and that much of the TRPV1 itself is localized to internal membranes suggests that the rate of ligand entry into the cell may be an important determinant of the kinetics of ligand action. In this study, we synthesized a BODIPY TR-labeled fluorescent capsaicin analog (CHK-884) so that we could directly measure ligand entry. We report that CHK-884 penetrated only slowly into Chinese hamster ovary (CHO) cells expressing rat TRPV1, with a t1/2 of 30 +/- 4 min, and localized in the endoplasmic reticulum and Golgi.

ING2 regulates the onset of replicative senescence by induction of p300-dependent p53 acetylation.

ING2 is a candidate tumor suppressor gene that can activate p53 by enhancing its acetylation. Here, we demonstrate that ING2 is also involved in p53-mediated replicative senescence. ING2 protein expression increased in late-passage human primary cells, and it colocalizes with serine 15-phosphorylated p53.

A novel diacylglycerol-lactone shows marked selectivity in vitro among C1 domains of protein kinase C (PKC) isoforms alpha and delta as well as selectivity for RasGRP compared with PKCalpha.

Although multiple natural products are potent ligands for the diacylglycerol binding C1 domain of protein kinase C (PKC), RasGRP, and related targets, the high conservation of C1 domains has impeded the development of selective ligands. We characterized here a diacylglycerol-lactone, 130C037, emerging from a combinatorial chemical synthetic strategy, which showed substantial selectivity. 130C037 gave shallow binding curves for PKC isoforms alpha, beta, gamma, delta, and epsilon, with apparent Ki values ranging from 340 nm for PKCalpha to 29 nm for PKCepsilon.