Exploiting Zebrafish Xenografts for Testing the in vivo Antitumorigenic Activity of Microcin E492 Against Human Colorectal Cancer Cells.

One of the approaches to address cancer treatment is to develop new drugs not only to obtain compounds with less side effects, but also to have a broader set of alternatives to tackle the resistant forms of this pathology. In this regard, growing evidence supports the use of bacteria-derived peptides such as bacteriocins, which have emerged as promising anti-cancer molecules. In addition to test the activity of these molecules on cancer cells in culture, their in vivo antitumorigenic properties must be validated in animal models. Although the standard approach for such assays employs experiments in nude mice, at the initial stages of testing, the use of high-throughput animal models would permit rapid proof-of-concept experiments, screening a high number of compounds, and thus increasing the possibilities of finding new anti-cancer molecules. A validated and promising alternative animal model are zebrafish larvae harboring xenografts of human cancer cells. Here, we addressed the anti-cancer properties of the antibacterial peptide microcin E492 (MccE492), a bacteriocin produced by Klebsiella pneumoniae, showing that this peptide has a marked cytotoxic effect on human colorectal cancer cells in vitro. Furthermore, we developed a zebrafish xenograft model using these cells to test the antitumor effect of MccE492 in vivo, demonstrating that intratumor injection of this peptide significantly reduced the tumor cell mass. Our results provide, for the first time, evidence of the in vivo antitumoral properties of a bacteriocin tested in an animal model. This evidence strongly supports the potential of this bacteriocin for the development of novel anti-cancer therapies.

Insights into the HyPer biosensor as molecular tool for monitoring cellular antioxidant capacity.

Aerobic metabolism brings inexorably the production of reactive oxygen species (ROS), which are counterbalanced by intrinsic antioxidant defenses avoiding deleterious intracellular effects. Redox balance is the resultant of metabolic functioning under environmental inputs (i.e. diet, pollution) and the activity of intrinsic antioxidant machinery. Monitoring of intracellular hydrogen peroxide has been successfully achieved by redox biosensor advent; however, to track the intrinsic disulfide bond reduction capacity represents a fundamental piece to understand better how redox homeostasis is maintained in living cells. In the present work, we compared the informative value of steady-state measurements and the kinetics of HyPer, a H2O2-sensitive fluorescent biosensor, targeted at the cytosol, mitochondrion and endoplasmic reticulum. From this set of data, biosensor signal recovery from an oxidized state raised as a suitable parameter to discriminate reducing capacity of a close environment. Biosensor recovery was pH-independent, condition demonstrated by experiments on pH-clamped cells, and sensitive to pharmacological perturbations of enzymatic disulfide reduction. Also, ten human cell lines were characterized according their H2O2-pulse responses, including their capacity to reduce disulfide bonds evaluated in terms of their migratory capacity. Finally, cellular migration experiments were conducted to study whether migratory efficiency was associated with the disulfide reduction activity. The migration efficiency of each cell type correlates with the rate of signal recovery measured from the oxidized biosensor. In addition, HyPer-expressing cells treated with N-acetyl-cysteine had accelerated recovery rates and major migratory capacities, both reversible effects upon treatment removal. Our data demonstrate that the HyPer signal recovery offers a novel methodological tool to track the cellular impact of redox active biomolecules.

Glucose Promotes a Pro-Oxidant and Pro-Inflammatory Stromal Microenvironment Which Favors Motile Properties in Breast Tumor Cells.

Chronic inflammation and metabolic reprogramming have been proposed as hallmarks of cancer development. Currently, many of the functional clues between these two phenomena are studied under the integrative view of functional stroma-epithelia interaction. It has been proposed that stromal cells, due to their abundance and avidity for glucose, are able to modify the metabolic behavior of an entire solid tumor. In the present study, using a mammary stromal cell line derived from healthy tissue subjected to long-term culture in low (5 mM) or high (25 mM) glucose, we found that the hyperglycemic condition favors the establishment of a pro-inflammatory and pro-oxidant environment characterized by the induction of the COX-2/PGE2 axis. In this condition, epithelial migration was stimulated. Moreover, we also found that stromal-derived PGE2, acting as a stimulator of IL-1 epithelial expression was one of the factors that promote the acquisition of motile properties by epithelial cells and the maintenance of a COX-2/PGE2-dependent inflammatory condition. Overall, our work provides experimental evidence that glucose stimulates a tumor inflammatory environment that, as a result of a functional cross-talk between stroma and epithelia, may be responsible for tumor progression. J. Cell. Biochem. 118: 994-1002, 2017. © 2016 Wiley Periodicals, Inc.