Nek1-inhibitor and temozolomide-loaded microfibers as a co-therapy strategy for glioblastoma treatment.

Malignant glioblastoma (GB) is the predominant primary brain tumour in adults, but despite the efforts towards novel therapies, the median survival of GB patients has not significantly improved in the last decades. Therefore, localised approaches that treat GB straight into the tumour site provide an alternative to enhance chemotherapy bioavailability and efficacy, reducing systemic toxicity. Likewise, the discovery of protein targets, such as the NIMA-related kinase 1 (Nek1), which was previously shown to be associated with temozolomide (TMZ) resistance in GB, has stimulated the clinical development of target therapy approaches to treat GB patients. In this study, we report an electrospun polyvinyl alcohol (PVA) microfiber (MF) brain-implant prepared for the controlled release of Nek1 protein inhibitor (iNek1) and TMZ or TMZ-loaded nanoparticles. The formulations revealed adequate stability and drug loading, which prolonged the drugs' release allowing a sustained exposure of the GB cells to the treatment and enhancing the drugs' therapeutic effects. TMZ-loaded MF provided the highest concentration of TMZ within the brain of tumour-bearing rats, and it was statistically significant when compared to TMZ via intraperitoneal (IP). All animals treated with either co-therapy formulation (TMZ + iNek1 MF or TMZ nanoparticles + iNek1 MF) survived until the endpoint (60 days), whereas the Blank MF (drug-unloaded), TMZ MF and TMZ IP-treated rats' median survival was found to be 16, 31 and 25 days, respectively. The tumour/brain area ratio of the rats implanted with either MF co-therapy was found to be reduced by 5-fold when compared to Blank MF-implanted rats. Taken together, our results strongly suggest that Nek1 is an important GB oncotarget and the inhibition of Nek1's activity significantly decreases GB cells' viability and tumour size when combined with TMZ treatment.

Development, Characterization and Cell Viability Inhibition of PVA Spheres Loaded with Doxorubicin and 4'-Amino-1-Naphthyl-Chalcone (D14) for Osteosarcoma.

Chalcones (1,3-diaryl-2-propen-1-ones) are naturally occurring polyphenols with known anticancer activity against a variety of tumor cell lines, including osteosarcoma (OS). In this paper, we present the preparation and characterization of spheres (~2 mm) from polyvinyl alcohol (PVA) containing a combination of 4'-Amino-1-Naphthyl-Chalcone (D14) and doxorubicin, to act as a new polymeric dual-drug anticancer delivery. D14 is a potent inhibitor of osteosarcoma progression and, when combined with doxorubicin, presents a synergetic effect; hence, physically crosslinked PVA spheres loaded with D14 and doxorubicin were prepared using liquid nitrogen and six freeze-thawing cycles. Physical-chemical characterization using a scanning electron microscope (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) presented that the drugs were incorporated into the spheres via weak interactions between the drugs and the polymeric chains, resulting in overall good drug stability. The cytotoxicity activity of the PVA spheres co-encapsulating both drugs was tested against the U2OS human osteosarcoma cell line by 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) assay, and compared to the spheres carrying either D14 or doxorubicin alone. The co-delivery showed a cytotoxic effect 2.6-fold greater than doxorubicin alone, revealing a significant synergistic effect with a coefficient of drug interaction (CDI) of 0.49. The obtained results suggest this developed PVA sphere as a potential dual-drug delivery system that could be used for the prominent synergistic anticancer activity of co-delivering D14 and doxorubicin, providing a new potential strategy for improved osteosarcoma treatment.

Establishing the allosteric mechanism in CRISPR-Cas9.

Allostery is a fundamental property of proteins, which regulates biochemical information transfer between spatially distant sites. Here, we report on the critical role of molecular dynamics (MD) simulations in discovering the mechanism of allosteric communication within CRISPR-Cas9, a leading genome editing machinery with enormous promises for medicine and biotechnology. MD revealed how allostery intervenes during at least three steps of the CRISPR-Cas9 function: affecting DNA recognition, mediating the cleavage and interfering with the off-target activity. An allosteric communication that activates concerted DNA cleavages was found to led through the L1/L2 loops, which connect the HNH and RuvC catalytic domains. The identification of these "allosteric transducers" inspired the development of novel variants of the Cas9 protein with improved specificity, opening a new avenue for controlling the CRISPR-Cas9 activity. Discussed studies also highlight the critical role of the recognition lobe in the conformational activation of the catalytic HNH domain. Specifically, the REC3 region was found to modulate the dynamics of HNH by sensing the formation of the RNA:DNA hybrid. The role of REC3 was revealed to be particularly relevant in the presence of DNA mismatches. Indeed, interference of REC3 with the RNA:DNA hybrid containing mismatched pairs at specific positions resulted in locking HNH in an inactive "conformational checkpoint" conformation, thereby hampering off-target cleavages. Overall, MD simulations established the fundamental mechanisms underlying the allosterism of CRISPR-Cas9, aiding engineering strategies to develop new CRISPR-Cas9 variants for improved genome editing.

Electrospun PVA-Dacarbazine nanofibers as a novel nano brain-implant for treatment of glioblastoma: in silico and in vitro characterization.

Malignant glioblastoma (GB) treatment consists of resection surgery followed by radiotherapy and chemotherapy (CT). Despite several implications, such as systemic toxicity and low efficacy, CT continues to be used for GB therapy. Aiming to overcome the blood-brain barrier (BBB) limitations, one of the most promising approaches is the use of drug delivery systems (DDS) to treat the cancer cells in situ. Dacarbazine (DTIC) is an antitumor agent that has limited application given its high toxicity to healthy cells. However, it is effective against GB recurrent cells. In this study, DTIC polymeric nanofibers (NF) were successfully prepared, characterized and its in vitro anticancer efficacy was determined. This system demonstrated high drug loading of 83.9 ± 6.5%, good stability and mechanical properties and sustained drug release, improved in tumor pH (6.8). This controlled release prolonged the uptake of GB improving DTIC antitumor effects such as DNA damage and cell death by apoptosis. Molecular dynamics simulations revealed that DTIC interacts with PVA, possibly explaining the controlled release of the drug. Therefore, DTIC NF brain-implants show great potential as a promising drug delivery system for GB therapy.

Antithrombin conformational modulation by D-myo-inositol 3,4,5,6-tetrakisphosphate (TMI), a novel scaffold for the development of antithrombotic agents.

Antithrombin (AT) is a serpin that inhibits mainly thrombin and fXa after being activated by binding to glycosaminoglycans as heparin and heparan sulfate. Upon binding, the native AT conformation, relatively inactive as a protease inhibitor, is converted to an activated form. Recently, a new compound, named TMI, was discovered in our group with nanomolar affinity to antithrombin, and shown to be able to induce a partial activation of antithrombin. As TMI represents an original scaffold for structural optimizations aiming the development of new antithrombotic drugs, the present work demonstrated, through a series of molecular dynamics simulations, that TMI is able to modulate AT reactive center loop flexibility similarly to what is observed to heparin, as well as exposing AT P1 residue, Arg393. These results represent the first atomic level indication of AT conformational activation by TMI, and may offer a predictive basis for future studies aiming TMI structural optimization.

In silico Investigation of the PglB Active Site Reveals Transient Catalytic States and Octahedral Metal Ion Coordination.

The last step of the bacterial N-glycosylation pathway involves PglB, an oligosaccharyltransferase, which is responsible for the en bloc transfer of a fully assembled oligosaccharide chain to a protein possessing the extended motif D/E-X-N-X-S/T. Recently, this molecule had its full structure elucidated, enabling the description of its domains and the proposition of a catalytic mechanism. By employing molecular dynamics simulations, we were able to evaluate structural aspects of PglB, suggesting prevalent motions that may bring insights into the mechanism of the glycosylated peptide detachment. Additionally, we identified transient states at the catalytic site, in which the previously described carboxamide twisting mechanism was observed. Aided by quantum mechanics calculations for each different conformational states of the catalytic site, we determined the presence of an octahedral metal coordination, along with the presence of one water molecule at the catalytic site.

2´,3´-Dialdehyde of ATP, ADP, and adenosine inhibit HIV-1 reverse transcriptase and HIV-1 replication.

The 2´3´-dialdehyde of ATP or oxidized ATP (oATP) is a compound known for specifically making covalent bonds with the nucleotide-binding site of several ATP-binding enzymes and receptors. We investigated the effects of oATP and other oxidized purines on HIV-1 infection and we found that this compound inhibits HIV-1 and SIV infection by blocking early steps of virus replication. oATP, oxidized ADP (oADP), and oxidized Adenosine (oADO) impact the natural activity of endogenous reverse transcriptase enzyme (RT) in cell free virus particles and are able to inhibit viral replication in different cell types when added to the cell cultures either before or after infection. We used UFLC-UV to show that both oADO and oATP can be detected in the cell after being added in the extracellular medium. oATP also suppresses RT activity and replication of the HIV-1 resistant variants M184V and T215Y. We conclude that oATP, oADP and oADO display anti HIV-1 activity that is at in least in part due to inhibitory activity on HIV-1 RT.