José María Sánchez-Puelles

Aplidin ™ induces the mitochondrial apoptotic pathway via oxidative stress-mediated JNK and p38 activation and protein kinase C δ

Aplidin™, a new antitumoural drug presently in phase II clinical trials, has shown both in vitro and in vivo activity against human cancer cells. Aplidin™ effectively inhibits cell viability by triggering a canonical apoptotic program resulting in alterations in cell morphology, caspase activation, and chromatin fragmentation. Pro-apoptotic concentrations of Aplidin™ induce early oxidative stress, which results in a rapid and persistent activation of both JNK and p38 MAPK and a biphasic activation of ERK. Inhibition of JNK and p38 MAPK blocks the apoptotic program induced by Aplidin™, demonstrating its central role in the integration of the cellular stress induced by the drug. JNK and p38 MAPK activation results in downstream cytochrome c release and activation of caspases -9 and -3 and PARP cleavage, demonstrating the mediation of the mitochondrial apoptotic pathway in this process. We also demonstrate that protein kinase C delta (PKC-δ) mediates the cytotoxic effect of Aplidin™ and that it is concomitantly processed and activated late in the apoptotic process by a caspase mediated mechanism. Remarkably, cells deficient in PKC-δ show enhanced survival upon drug treatment as compared to its wild type counterpart. PKC-δ thus appears as an important component necessary for full caspase cascade activation and execution of apoptosis, which most probably initiates a positive feedback loop further amplifying the apoptotic process.

FM19G11, a New Hypoxia-inducible Factor (HIF) Modulator, Affects Stem Cell Differentiation Status

The biology of the α subunits of hypoxia-inducible factors (HIFα) has expanded from their role in angiogenesis to their current position in the self-renewal and differentiation of stem cells. The results reported in this article show the discovery of FM19G11, a novel chemical entity that inhibits HIFα proteins that repress target genes of the two α subunits, in various tumor cell lines as well as in adult and embryonic stem cell models from rodents and humans, respectively. FM19G11 inhibits at nanomolar range the transcriptional and protein expression of Oct4, Sox2, Nanog, and Tgf-α undifferentiating factors, in adult rat and human embryonic stem cells, FM19G11 activity occurs in ependymal progenitor stem cells from rats (epSPC), a cell model reported for spinal cord regeneration, which allows the progression of oligodendrocyte cell differentiation in a hypoxic environment, has created interest in its characterization for pharmacological research. Experiments using small interfering RNA showed a significant depletion in Sox2 protein only in the case of HIF2α silencing, but not in HIF1α-mediated ablation. Moreover, chromatin immunoprecipitation data, together with the significant presence of functional hypoxia response element consensus sequences in the promoter region of Sox2, strongly validated that this factor behaves as a target gene of HIF2α in epSPCs. FM19G11 causes a reduction of overall histone acetylation with significant repression of p300, a histone acetyltransferase required as a co-factor for HIF-transcription activation. Arrays carried out in the presence and absence of the inhibitor showed the predominant involvement of epigenetic-associated events mediated by the drug.

Molecular characterization of the safracin biosynthetic pathway from Pseudomonas fluorescens A2‐2: designing new cytotoxic compounds

Safracin is an antibiotic with anti‐tumour activity produced by Pseudomonas fluorescens A2‐2. The entire safracin synthetic gene cluster spanning 17.5 kb has been identified, cloned and sequenced. The safracin cluster comprises 10 open reading frames (ORFs) encoding proteins for three non‐ribosomal peptide synthetases (NRPS), three safracin precursor biosynthetic enzymes, two safracin tailoring enzymes, a safracin resistance protein and a small hypothetical protein of unknown function. These genes are organized in two divergent operons of eight and two genes respectively. This pathway exhibits unusual features when compared with other NRPS systems. We have demonstrated by heterologous expression of the cluster that it is able to direct the synthesis of safracin in other strains. Cross‐feeding experiments have confirmed that 3‐hydroxy‐5‐methyl‐O‐methyltyrosine is the precursor of two amino acids of the molecule. Genetic analyses have allowed us to demonstrate that the bicistronic operon encodes the hydroxylation and N‐methylation activities of the pathway. The cloning and expression of the safracin cluster has settled the basis for the in vivo and in vitro production of a wide variety of compounds, such as the promising ecteinascidins anti‐cancer compounds.

Magnetobiosensors Based on Viral Protein p19 for MicroRNA Determination in Cancer Cells and Tissues

MicroRNAs (miRs) have emerged as important clinical biomarkers with both diagnostic and prognostic value for relevant diseases, such as cancer. MiRs pose unique challenges for detection and are currently detected by northern blotting, real-time PCR, and microarray techniques. These expensive, complicated, and time-consuming techniques are not feasible for on-site miR determination. In this study, amperometric magnetobiosensors involving RNA-binding viral protein p19 as a selective biorecognition element were developed for miR quantification. The p19-based magnetosensors were able to detect 0.4 fmol of a synthetic target and endogenous miR-21 (selected as a model for its role in a wide variety of cancers) in only 2 h in total RNA extracted from cancer cells and human breast-tumor specimens without PCR amplification and sample preprocessing. These results open up formidable perspectives for the diagnosis and prognosis of human cancers and for drug-discovery programs.

Isolation, characterization and physiological properties of an autolytic-deficient mutant of Streptococcus pneumoniae

SummaryA spontaneous mutation in the gene lyt encoding the pneumococcal autolysin has been characterized. This mutation, named lyt-32, which behaves as a high-efficiency marker in pneumococcal transformation, is a single base pair GC deletion causing the appearance of two consecutive termination codons in the amino terminal part of the sequence of the autolysin gene. The mutant lyt gene did not code for a polypeptide of relative molecular mass corresponding to the pneumococcal E form amidase in Escherichia coli maxicells. Pneumococcal cells containing the lyt-32 mutation (M32) were fully transformable, multiplied at a normal growth rate forming small chains and showed a tolerant response when treated with beta-lactam antibiotics. Strain M32 represents the first example of a mutant of Streptococcus pneumoniae completely lacking amidase as a consequence of an alteration in the structural gene coding for the pneumococcal autolysin.

FM19G11: A new modulator of HIF that links mTOR activation with the DNA damage checkpoint pathways.

The network consisting of mTOR and p53 pathways is crucial to understanding a wide variety of physiological and pathological events, including cancer and aging. In addition, the HIF1α protein, a downstream target of mTOR, is a hallmark of different tumor types and was the desired strategy of many drug discovery efforts. Here we present the novel chemical entity FM19G11, a new modulator of HIF1a expression, which was used as a molecular tool to dissect and further characterize the cross-talk between these signaling cascades in human colon carcinoma cell lines. To our knowledge, FM19G11 is the first drug that triggers a DNA damage response (DDR) associated with G1/S-phase arrest in a p53-dependent manner, due to rapid hyper-activation of the growth signaling pathway through mTOR. Assessment of colonies demonstrated that FM19G11 decreases the clonogenicity of HT29, HCT116/p53+/+ and HCT116/p53-/- cells. Moreover, FM19G11 causes significant lower colony growth in soft agar of p53-proficient human colon cancer cells. Consequently, p53 sensitizes human colon cancer cells to FM19G11 by significant reduction of their viability, lessening their colony formation capability and shrinking their anchorage-independent growth. Cell signaling studies served to assign a new mode of action to FM19G11, whose tumor-suppressant activity compromises the survival of functional p53 malignant cells.

Auranofin efficacy against MDR Streptococcus pneumoniae and Staphylococcus aureus infections

BACKGROUND Auranofin is an FDA-approved, gold-containing compound in clinical use for the oral treatment of rheumatoid arthritis and has been recently granted by the regulatory authorities due to its antiprotozoal properties. METHODS A reprofiling strategy was performed with a Streptococcus pneumoniae phenotypic screen and a proprietary library of compounds, consisting of both FDA-approved and unapproved bioactive compounds. Two different multiresistant S. pneumoniae strains were employed in a sepsis mouse model of infection. In addition, an MRSA strain was tested using both the thigh model and a mesh-associated biofilm infection in mice. RESULTS The repurposing approach showed the high potency of auranofin against multiresistant clinical isolates of S. pneumoniae and Staphylococcus aureus in vitro and in vivo. Efficacy in the S. pneumoniae sepsis model was obtained using auranofin by the oral route in the dose ranges used for the treatment of rheumatoid arthritis. Thioglucose replacement by alkyl chains showed that this moiety was not essential for the antibacterial activity and led to the discovery of a new gold derivative (MH05) with remarkable activity in vitro and in vivo. CONCLUSIONS Auranofin and the new gold derivative MH05 showed encouraging in vivo activity against multiresistant clinical isolates of S. pneumoniae and S. aureus. The clinical management of auranofin, alone or in combination with other antibiotics, deserves further exploration before use in patients presenting therapeutic failure caused by infections with multiresistant Gram-positive pathogens. Decades of clinical use mean that this compound is safe to use and may accelerate its evaluation in humans.

FM19G11 reverses endothelial dysfunction in rat and human arteries through stimulation of the PI3K/Akt/eNOS pathway, independently of mTOR/HIF-1α activation

FM19G11 up‐regulates mammalian target of rapamycin (mTOR)/hypoxia inducible factor‐1α (HIF‐1α) and PI3K/Akt pathways, which are involved in endothelial function. We evaluated the effects of FM19G11 on defective endothelial vasodilatation in arteries from rats and humans and investigated the mechanisms involved.

Searching for the Evolutionary Design of the Pneumococcal Cell Wall Lytic Enzymes

Peptidoglycan hydrolases represent one of the enzyme families most widely distributed in nature, since members of this family have been described from bacteriophages to man. Lysozymes, one of the best known group of enzymes at biochemical, structural and evolutionary levels, are included in this family (Jolles and Jolles, 1984). Moreover, bacterial autolysins, enzymes which have been postulated to participate in important physiological functions, are also peptidoglycan hydrolases (Rogers et al., 1980). Probably, the amidase LYTA from Streptococcus pneumoniae is the best characterized autolysin described so far (Holtje and Tomasz, 1976; Tomasz, 1984). The gene lytA encoding this enzyme has been cloned and sequenced (Garcia et al., 1986), allowing us to obtain valuable information about its implication in the process of daugther cell separation (Ronda et al., 1987). The cloning of lytA has also facilitated the isolation of the genes encoding the cell wall lytic enzymes from pneumococcal bacteriophages based on their sequence homologies (Garcia et al. 1987; Garcia et al., 1988; Garcia et al., 1990; Romero et al., 1990 a). The comparison of the sequences of the host and phage genes revealed that pneumococcal cell wall lytic enzymes could be the result of the fusion of two independent functional domains, one containing the active center (N-terminal domain) and the other responsible of the recognition of the teichoic acids of the cell wall (C-terminal domain) (Garcia et al, 1988; Garcia et al., 1990; Romero et al., 1990a;). This hypothesis was based on the observation that the host LYTA and phage HBL amidases, and the phage CPL1 and CPL9 lysozymes, which depend on the presence of choline in the teichoic acids for activity, have homologous C-terminal domains.