Cancer stem cells in solid tumors

Cancer stem cells (CSCs) are cells that drive tumorigenesis, as well as giving rise to a large population of differentiated progeny that make up the bulk of the tumor, but that lack tumorigenic potential. CSCs have been identified in a variety of human tumors, as assayed by their ability to initiate tumor growth in immunocompromised mice. Further characterization studies have demonstrated that gene expression profiles in breast cancer correlate with patient prognosis, and brain CSCs are specifically resistant to radiation through DNA damage repair. In addition, specific signaling pathways play a functional role in CSC self renewal and/or differentiation, and early studies indicate that CSCs are associated with a microenvironmental niche. Thus the biological properties of CSCs are just beginning to be revealed, and the continuation of these studies should lead to the development of CSC-targeted therapies for cancer treatment.     

Extracellular mRNA induces dendritic cell activation by stimulating tumor necrosis factor-alpha secretion and signaling through a nucleotide receptor

We previously demonstrated that dendritic cell (DC) pulsing with antigen-encoded mRNA resulted in the loading of both major histocompatibility complex class I and II antigen presentation pathways and the delivery of an activation signal. Coculture of mRNA-pulsed DC with T cells led to the induction of a potent primary immune response. DC, in addition to recognizing foreign antigens through pattern recognition receptors, also must respond to altered self, transformed, or intracellularly infected cells. This occurs through cell surface receptors that recognize products of inflammation and cell death. In this report, we characterize two signaling pathways utilized by extracellular mRNA to activate DC. In addition, a novel ligand, poly(A), is identified that mediates signaling through a receptor that can be inhibited by pertussis toxin and suramin and can be desensitized by ATP and ADP, suggesting a P2Y type nucleotide receptor. The role of this signaling activity in vaccine design and the potential effect of mRNA released by damaged cells in the induction of immune responsiveness is discussed.     

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to MHC region antigens

The maturation sequences of thymocytes is known to some extent: A generative layer of subcapsular large lymphoblasts gives rise to a major population of small cortical thymocytes and a minor population of midsize medullary thymocytes. The relative contribution of these three populations to the peripheral T cell populations is not yet known. In this study, subcapsular lymphoblasts, cortical small cells, medullary cells, and thymic emigrant cells have all been analyzed by immunofluorescence for expression of the antigens H-2D, I-A, H-2K, and TL. H-2D is expressed brightly on all subcapsular large cells, dimly on cortical small cells, and brightly on all migrants, cortisone-resistant thymocytes (CRT), and peripheral T cells. I-A can be detected at low levels on 30 to 50% of cells in all the thymic subpopulations, and on 30 to 50% of migrants and peripheral T cells. Fifty to 80% of small cortical cells do not express detectable H-2K, but all the other subpopulations, both inside and outside the thymus, stain uniformly quite brightly. TL3 is expressed on 70 to 80% of subcapsular and cortical thymocytes, 30 to 40% of CRT, is undetectable on migrants but can be seen at low levels on 10 to 20% of spleen and lymph node T cells. The possibility that some or all of these antigens represent stable markers of separate lineages rather than unstable, stage-specific markers is discussed.     

Assay for ubiquitin ligase activity: high-throughput screen for inhibitors of HDM2

An assay for the autoubiquitination activity of the E3 ligase HDM2 (Mdm2) was developed and adapted to a high-throughput format to identify inhibitors of this activity. The assay can also be used to measure the activity of other E3s and may be useful in finding both inhibitors and activators of a wide range of different ubiquitin ligases.     

Ligand-dependent differences in estrogen receptor beta-interacting proteins identified in lung adenocarcinoma cells corresponds to estrogenic responses

Background

A recent epidemiological study demonstrated a reduced risk of lung cancer mortality in breast cancer patients using antiestrogens. These and other data implicate a role for estrogens in lung cancer, particularly nonsmall cell lung cancer (NSCLC). Approximately 61% of human NSCLC tumors express nuclear estrogen receptor β (ERβ); however, the role of ERβ and estrogens in NSCLC is likely to be multifactorial. Here we tested the hypothesis that proteins interacting with ERβ in human lung adenocarcinoma cells that respond proliferatively to estradiol (E₂) are distinct from those in non-E₂-responsive cells.

Methods

FLAG affinity purification of FLAG-ERβ-interacting proteins was used to isolate ERβ-interacting proteins in whole cell extracts from E₂ proliferative H1793 and non-E₂-proliferative A549 lung adenocarcinoma cell lines. Following trypsin digestion, proteins were identified using liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). Proteomic data were analyzed using Ingenuity Pathway Analysis. Select results were confirmed by coimmunoprecipitation.

Results

LC-MS/MS identified 27 non-redundant ERβ-interacting proteins. ERβ-interacting proteins included hsp70, hsp60, vimentin, histones and calmodulin. Ingenuity Pathway Analysis of the ERβ-interacting proteins revealed differences in molecular and functional networks between H1793 and A549 lung adenocarcinoma cells. Coimmunoprecipitation experiments in these and other lung adenocarcinoma cells confirmed that ERβ and EGFR interact in a gender-dependent manner and in response to E₂ or EGF. BRCA1 interacted with ERβ in A549 cell lines and in human lung adenocarcinoma tumors, but not normal lung tissue.

Conclusion

Our results identify specific differences in ERβ-interacting proteins in lung adenocarcinoma cells corresponding to ligand-dependent differences in estrogenic responses.

     

A novel action of glucocorticosteroid in inhibition of leukotriene C4 production by rat basophilic leukemia cells: suppression of the elevation of cytosolic free Ca2+ induced by antigen

Rat basophilic leukemia (RBL-2H3) cells serve as a model to examine the role of elevated internal Ca2+ concentration ([Ca2+]i), following antigen (DNP10BSA)-induced stimulation of leukotriene C4 (LTC4) formation. A novel action of hydrocortisone (HC), to reduce increased [Ca2+]i and consequently inhibit LTC4 formation is assessed. Half-maximal time for elevation of [Ca2+]i induced by antigen was less than 1 min, and maximal elevation of [Ca2+]i (3-fold increase) was reached within 2-3 min. This high [Ca2+]i level waned gradually by 27% during 20 min of incubation. For induction of LTC4 formation, however, there was a refractory period of about 2 min, and half-maximal elevation was at 11 min. Following pretreatment with HC, the antigen-stimulated increase in [Ca2+]i was stunted by 41% at 2-3 min and by 73% at 20 min. LTC4 formation was almost abolished. There was a lag period of at least 2 h to observe any inhibition in both parameters, and the maximal inhibition was about 4 h. Cycloheximide, and receptor antagonist to glucocorticosteroid (RU486) completely prevented the inhibitory effects of HC on elevated [Ca2+]i and LTC4 formation. Estradiol and aldosterone (each at 2.10(-6) M) were virtually inactive, while another glucocorticosteroid, dexamethasone (2.10(-7) M) markedly suppressed antigen induction in both parameters. It is proposed that the inhibitory effect of HC on the formation of LTC4 could be attributed mainly to its ability to reduce elevated [Ca2+]i.     

Human health risks of metals and metalloids in muscle tissue of Synodontis zambezensis Peters, 1852 from Flag Boshielo Dam,South Africa

Muscle tissue from 63 Synodontis zambezensis collected bimonthly in 2013 at Flag Boshielo Dam were analysed for metals and metalloids in a desktop human health risk assessment. The Hazard Quotient, based on a weekly meal of 67 g of fish muscle, exceeded the maximum acceptable level of one for lead, cobalt, cadmium, mercury, arsenic and selenium. The concentrations of these elements were higher in 2013 than those recorded in 2009 and 2012 in other fish species from Flag Boshielo Dam and these may pose a long-term health risk if consumed regularly by impoverished rural communities reliant on fish as a source of protein.     

J Domain Co-chaperone Specificity Defines the Role of BiP during Protein Translocation

Hsp70 chaperones can potentially interact with one of several J domain-containing Hsp40 co-chaperones to regulate distinct cellular processes. However, features within Hsp70s that determine Hsp40 specificity are undefined. To investigate this question, we introduced mutations into the ER-lumenal Hsp70, BiP/Kar2p, and found that an R217A substitution in the J domain-interacting surface of BiP compromised the physical and functional interaction with Sec63p, an Hsp40 required for ER translocation. In contrast, interaction with Jem1p, an Hsp40 required for ER-associated degradation, was unaffected. Moreover, yeast expressing R217A BiP exhibited defects in translocation but not in ER-associated degradation. Finally, the genetic interactions of the R217A BiP mutant were found to correlate with those of known translocation mutants. Together, our results indicate that residues within the Hsp70 J domain-interacting surface help confer Hsp40 specificity, in turn influencing distinct chaperone-mediated cellular activities.