CSIG-11. KINASE-DIRECTED INHIBITION OF PYRIMIDINE BIOSYNTHESIS IN PTEN-DEFICIENT GLIOBLASTOMA

Targeting pyrimidine biosynthesis has been a mainstay of chemotherapy in oncology, including frontline treatment of pancreatic, breast, and colorectal carcinomas. In glioblastoma, the targeting pyrimidine biosynthesis is a promising emerging approach for counteracting the effects of PTEN-deficiency in glioblastoma. PTEN loss triggers the activation of mTORC1, which in turn phosphorylates and activates the ribosomal protein kinases S6K1 and S6K2. We have previously shown that combination treatment of inhibitors targeting S6K1 and the TYRO3-AXL-MERTK receptor tyrosine kinases (TAM-RTKs) triggers cytotoxic responses in PTEN-deficient glioblastoma cells. Here we show brain-penetrant inactivation of S6K1 and TAM-RTKs using the S6K1 inhibitor LY-2584702 and the TAM-RTK inhibitor BMS-777607, which reduced glioblastoma tumor growth. Pharmacogenetic analysis of signal transduction indicated a key role for S6K2 in sustaining survival signaling in PTEN-deficient glioblastoma cells. Steady-state metabolomics revealed that combined inactivation of S6K1 and TAM-RTKs resulted in decreased nucleotide biosynthesis, and flux analysis indicated reduced flux of glucose to pyrimidines. Altogether the results indicate a kinase-directed therapeutic strategy for targeting S6K1 and TAM-RTKs to reduce pyrimidine biosynthesis and glioblastoma tumor growth.

Comprehensive Evaluation of the Toxicity of the Flame Retardant (decabromodiphenyl ether) in a Bioindicator Fish (Gambusia affinis)

In recent years, polybrominated diphenyl ethers or PBDE have been identified as the new emerging pollutants. These pollutants are derived from e-waste and their adverse effect on biota has been proven. In this work, the adverse effects of BDE-209 on mosquitofish (Gambusia affinis) were evaluated. Acute toxicity bioassays were carried out with daily renewal of solutions, using different concentrations of environmental relevance ranged between 10 and 100 µg.L− 1 of BDE-209. After 48 and 96 h of exposure, mortality, individual activity (swimming), biochemical activity (catalase; thiobarbituric acid reactive substances; and acetylcholinesterase), and cytotoxic responses (micronucleus frequencies) were studied. In addition, integrated biomarker response and multivariate analyses were conducted to study the correlation of biomarkers. The calculated lethal concentrations 50 remained constant after all exposure times (24 to 96 h), and the corresponding value was 27.79 µg.L− 1 BDE-209. Furthermore, BDE-209 induced effects on the swimming activity of this species in relation to acetylcholine, since BDE-209 increased, produced oxidative damage at the biochemical level and genotoxicity after 48 h of sublethal concentrations (10 and 25 µg.L− 1 BDE-209) of exposure. The results show that BDE-209 has biochemical, cytotoxic, neurotoxic and genotoxic potential on G. affinis. In addition, mosquitofish can be used as a good bioindicator to evaluate environmental stressors and flame retardants could be a risk factor to Neotropical species.

Anticytomegalovirus CD4 + T Cells Are Associated With Subclinical Atherosclerosis in Persons With HIV

Objective: Persons with HIV have double the risk of developing cardiovascular disease compared with the general population. A persistent and heightened immune response to cytomegalovirus coinfection may be one contributing factor, but the relationship between cytomegalovirus replication, virus-specific immune cells, and plaque burden is unclear. Approach and Results: We assessed the relationship between CD4 + T-cell subsets and carotid plaque burden in a cohort of 70 HIV-positive participants with sustained viral suppression on a single antiretroviral regimen and without known cardiovascular disease. We evaluated relationships between immune parameters, carotid plaque burden, and brachial artery flow-mediated vasodilation using multivariable linear and logistic regression models. We found that participants with carotid plaque had increased circulating CX3CR1 + ~GPR56 + ~CD57 + (ie, C~G~C) + CD4 + T cells ( P =0.03), which is a marker combination associated with antiviral and cytotoxic responses. In addition, a median of 14.4% (IQR, 4.7%–32.7%) of the C~G~C + CD4 + T-cells expressed antigen receptors that recognized a single cytomegalovirus glycoprotein-B epitope. Using immunofluorescence staining, we found that CX3CR1 + CD4 + T cells were present in coronary plaque from deceased HIV-positive persons. C~G~C + CD4 + T cells were also present in cells isolated from the aorta of HIV-negative donors. Conclusions: HIV-positive persons with carotid atheroma have a higher proportion of circulating CD4 + T-cells expressing the C~G~C surface marker combination associated with antiviral and cytotoxic responses. These cells can be cytomegalovirus-specific and are also present in the aorta.

Exosomes in Immune Regulation

Exosomes, small extracellular vesicles mediate intercellular communication by transferring their cargo including DNA, RNA, proteins and lipids from cell to cell. Notably, in the immune system, they have protective functions. However in cancer, exosomes acquire new, immunosuppressive properties that cause the dysregulation of immune cells and immune escape of tumor cells supporting cancer progression and metastasis. Therefore, current investigations focus on the regulation of exosome levels for immunotherapeutic interventions. In this review, we discuss the role of exosomes in immunomodulation of lymphoid and myeloid cells, and their use as immune stimulatory agents to elicit specific cytotoxic responses against the tumor.

Biosynthesis of Lemongrass Essential Oil and the Underlying Mechanism for Its Insecticidal Activity

Lemongrass (Cymbopogon flexuosus) is an aromatic perennial grass grown extensively for its essential oil. Lemongrass oil is chiefly a mixture of various cyclic and acyclic bioactive monoterpenes. We reviewed lemongrass oil and its biosynthesis in the present chapter along with its biochemical composition. Furthermore, we attempted to explore both the possible routes for essential oil biosynthesis in lemongrass, i.e. mevalonate and non-mevalonate pathways and how these pathways interwind with each other. Lemongrass oil has high commercial potential in medicinal, cosmetic, food and energy industries. Regarding the pharmacological properties, a wide array of biological activities has been observed in lemongrass oil such as antimicrobial, insecticidal, analgesic and anti-cancer properties as well as its efficacy as insect-repellent. The later sections were dedicated for the analysis of insecticidal property of the lemongrass oil and the mechanism working behind this phenomenon where it was observed that in addition to synergistic effects, various components of lemongrass oil can also induce specific neurotoxic and cytotoxic responses in the insects.

Design, Characterization, and Evaluation of scFvCD133/rGelonin: A CD133-Targeting Recombinant Immunotoxin for Use in Combination with Photochemical Internalization

The objective of this study was to develop and explore a novel CD133-targeting immunotoxin (IT) for use in combination with the endosomal escape method photochemical internalization (PCI). scFvCD133/rGelonin was recombinantly constructed by fusing a gene (scFvCD133) encoding the scFv that targets both non-glycosylated and glycosylated forms of both human and murine CD133/prominin-1 to a gene encoding the ribosome-inactivating protein (RIP) gelonin (rGelonin). RIP-activity was assessed in a cell-free translation assay. Selective binding and intracellular accumulation of scFvCD133/rGelonin was evaluated by flow cytometry and fluorescence microscopy. PCI of scFvCD133/rGelonin was explored in CD133high and CD133low cell lines and a CD133neg cell line, where cytotoxicity was evaluated by the MTT assay. scFvCD133/rGelonin exhibited superior binding to and a higher accumulation in CD133high cells compared to CD133low cells. No cytotoxic responses were detected in either CD133high or CD133low cells after 72 h incubation with <100 nM scFvCD133/rGelonin. Despite a severe loss in RIP-activity of scFvCD133/rGelonin compared to free rGelonin, PCI of scFvCD133/rGelonin induced log-fold reduction of viability compared to PCI of rGelonin. Strikingly, PCI of scFvCD133/rGelonin exceeded the cytotoxicity of PCI of rGelonin also in CD133low cells. In conclusion, PCI promotes strong cytotoxic activity of the per se non-toxic scFvCD133/rGelonin in both CD133high and CD133low cancer cells.