Development of Pyridazinone Chemotypes Targeting the PDEδ Prenyl Binding Site

The K-Ras GTPase is a major target in anticancer drug discovery. However, direct interference with signaling by K-Ras has not led to clinically useful drugs yet. Correct localization and signaling by farnesylated K-Ras is regulated by the prenyl binding protein PDEδ. Interfering with binding of PDEδ to K-Ras by means of small molecules provides a novel opportunity to suppress oncogenic signaling. Here we describe the identification and structure-guided development of novel K-Ras-PDEδ inhibitor chemotypes based on pyrrolopyridazinones and pyrazolopyridazinones that bind to the farnesyl binding pocket of PDEδ with low nanomolar affinity. We delineate the structure-property relationship and in vivo pharmacokinetic (PK) and toxicokinetic (Tox) studies for pyrazolopyridazinone-based K-Ras-PDEδ inhibitors. These findings may inspire novel drug discovery efforts aimed at the development of drugs targeting oncogenic Ras.

A fully automated procedure for the parallel, multidimensional purification and nucleotide loading of the human GTPases KRas, Rac1 and RalB

Small GTPases regulate many key cellular processes and their role in human disease validates many proteins in this class as desirable targets for therapeutic intervention. Reliable recombinant production of GTPases, often in the active GTP loaded state, is a prerequisite for the prosecution of drug discovery efforts. The preparation of these active forms can be complex and often constricts the supply to the reagent intensive techniques used in structure base drug discovery. We have established a fully automated, multidimensional protein purification strategy for the parallel production of the catalytic G-domains of KRas, Rac1 and RalB GTPases in the active form. This method incorporates a four step chromatography purification with TEV protease-mediated affinity tag cleavage and a conditioning step that achieves the activation of the GTPase by exchanging GDP for the non-hydrolyzable GTP analogue GMPPnP. We also demonstrate that an automated method is efficient at loading of KRas with mantGDP for application in a SOS1 catalysed fluorescent nucleotide exchange assay. In comparison to more conventional manual workflows the automated method offers marked advantages in method run time and operator workload. This reduces the bottleneck in protein production while generating products that are highly purified and effectively loaded with nucleotide analogues.

A PDE6δ-KRas Inhibitor Chemotype with up to Seven H-Bonds and Picomolar Affinity that Prevents Efficient Inhibitor Release by Arl2

Small-molecule inhibition of the interaction between the KRas oncoprotein and the chaperone PDE6δ impairs KRas spatial organization and signaling in cells. However, despite potent binding in vitro (KD <10 nm), interference with Ras signaling and growth inhibition require 5-20 μm compound concentrations. We demonstrate that these findings can be explained by fast release of high-affinity inhibitors from PDE6δ by the release factor Arl2. This limitation is overcome by novel highly selective inhibitors that bind to PDE6δ with up to 7 hydrogen bonds, resulting in picomolar affinity. Their release by Arl2 is greatly decreased, and representative compounds selectively inhibit growth of KRas mutated and -dependent cells with the highest activity recorded yet. Our findings indicate that very potent inhibitors of the KRas-PDE6δ interaction may impair the growth of tumors driven by oncogenic KRas.

Secreted CLIC3 drives cancer progression through its glutathione-dependent oxidoreductase activity

The secretome of cancer and stromal cells generates a microenvironment that contributes to tumour cell invasion and angiogenesis. Here we compare the secretome of human mammary normal and cancer-associated fibroblasts (CAFs). We discover that the chloride intracellular channel protein 3 (CLIC3) is an abundant component of the CAF secretome. Secreted CLIC3 promotes invasive behaviour of endothelial cells to drive angiogenesis and increases invasiveness of cancer cells both in vivo and in 3D cell culture models, and this requires active transglutaminase-2 (TGM2). CLIC3 acts as a glutathione-dependent oxidoreductase that reduces TGM2 and regulates TGM2 binding to its cofactors. Finally, CLIC3 is also secreted by cancer cells, is abundant in the stromal and tumour compartments of aggressive ovarian cancers and its levels correlate with poor clinical outcome. This work reveals a previously undescribed invasive mechanism whereby the secretion of a glutathione-dependent oxidoreductase drives angiogenesis and cancer progression by promoting TGM2-dependent invasion.

Shuttling and sorting lipid-modified cargo into the cilia

Primary cilia are hair-like microtubule-based organelles that can be found on almost all human cell types. Although the cilium is not separated from the cell by membranes, their content is different from that of the cell body and their membrane composition is distinct from that of the plasma membrane. Here, we will introduce a molecular machinery that shuttles and sorts lipid-modified proteins to the cilium, thus contributing in maintaining its distinct composition. The mechanism involves the binding of the GDI-like solubilising factors, uncoordinated (UNC)119a, UNC119b and PDE6D, to the lipid-modified ciliary cargo and the specific release of the cargo in the cilia by the ciliary small G-protein Arl3 in a GTP-dependent manner.

Drug resistance mutations among virological failure HIV-1 infected patients in Malaysia

The determination of HIV drug resistance mutations (DRMs) towards antiretroviral (ARV) drugs among HIV-1 treated patients with virological failure is crucial for further management of the patient. This study aimed to assess the most common genomic mutation and to analyse subtypes among the HIV-1 patients with viral load level > 1,000 copies/mL. A total of 101 virological failure HIV-1 patients from four different regions of Peninsular Malaysia with a viral load measurement facility were included in the study. Majority of patients (89.1%) have at least 1 mutation associated with clinical resistance to either protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs) or nonnucleoside reverse transcriptase inhibitors (NNRTIs). Major resistance mutations among the patients towards NRTIs and NNRTIs were 70.3% and 18.8%, respectively. The most common mutation for NRTIs was M184V while K103N mutation was detected in the majority of patients who were treated with NNRTIs. The most commonly observed mutations for major PI and minor PI seen among the study population were V82A/T and L10V, respectively. In HIV-1 subtype analysis, CRF33_01B was the most predominant HIV-1 subtype in this study group. The vast detection of DRMs in this study emphasized the importance of genotypic resistance test in the management of HIV patients as DRMs can alter patient's susceptibility towards ARV drugs. Further study on larger number of samples is essential for the development of a database on HIV-1 DRMs among patients that experience virological failure in Malaysia.

Identification of pyrazolopyridazinones as PDEδ inhibitors

The prenyl-binding protein PDEδ is crucial for the plasma membrane localization of prenylated Ras. Recently, we have reported that the small-molecule Deltarasin binds to the prenyl-binding pocket of PDEδ, and impairs Ras enrichment at the plasma membrane, thereby affecting the proliferation of KRas-dependent human pancreatic ductal adenocarcinoma cell lines. Here, using structure-based compound design, we have now identified pyrazolopyridazinones as a novel, unrelated chemotype that binds to the prenyl-binding pocket of PDEδ with high affinity, thereby displacing prenylated Ras proteins in cells. Our results show that the new PDEδ inhibitor, named Deltazinone 1, is highly selective, exhibits less unspecific cytotoxicity than the previously reported Deltarasin and demonstrates a high correlation with the phenotypic effect of PDEδ knockdown in a set of human pancreatic cancer cell lines.

PDE6δ-mediated sorting of INPP5E into the cilium is determined by cargo-carrier affinity

The phosphodiesterase 6 delta subunit (PDE6δ) shuttles several farnesylated cargos between membranes. The cargo sorting mechanism between cilia and other compartments is not understood. Here we show using the inositol polyphosphate 5'-phosphatase E (INPP5E) and the GTP-binding protein (Rheb) that cargo sorting depends on the affinity towards PDE6δ and the specificity of cargo release. High-affinity cargo is exclusively released by the ciliary transport regulator Arl3, while low-affinity cargo is released by Arl3 and its non-ciliary homologue Arl2. Structures of PDE6δ/cargo complexes reveal the molecular basis of the sorting signal which depends on the residues at the -1 and -3 positions relative to farnesylated cysteine. Structure-guided mutation allows the generation of a low-affinity INPP5E mutant which loses exclusive ciliary localization. We postulate that the affinity to PDE6δ and the release by Arl2/3 in addition to a retention signal are the determinants for cargo sorting and enrichment at its destination.

Video-assisted thoracic surgery in a Nigerian teaching hospital: Experience and challenges

BACKGROUND

Video-assisted thoracic surgery (VATS) is well established. Its application in Nigeria has however been limited and not been reported. The aim of this study was to describe our institutional experience and challenges with VATS.

MATERIALS AND METHODS

This was a retrospective cross-sectional study of all patients that underwent VATS in our institution between March 2008 and June 2013. Data were extracted from a prospectively maintained database.

RESULTS

Two hundred and sixty-one patients were assessed as potential VATS cases. VATS was initiated in 26 patients, but completed in 25 patients (9.6%) as there was one case of conversion of a planned VATS bullectomy due to the failure of one lung ventilation. There were 12 males and 13 females. Mean age was 40.7 ± 13.9 years. The indication was interstitial lung disease in 9 patients (36%), malignant pleural effusion in 6 patients (24%), spontaneous pneumothorax in 5 patients (20%), indeterminate pulmonary nodule in 2 patients (8%), pleural endometriosis in 2 patients (8%) and bronchogenic cyst in one patient (4%). Procedures performed were lung biopsy in 13 patients (52%), pleural biopsy and pleurodesis in 6 patients (24%), bullectomy and pleurodesis in 5 patients (20%) and excision of bronchogenic cyst in one patient (4%). Mean hospital stay was 4 ± 0.7 days. There were no complications and no mortalities.

CONCLUSION

VATS is being performed in our institution with successful outcomes. The use of VATS in Nigeria is encouraged. The relatively high cost of VATS is, however, a major limitation to more widespread use.

ROBERTS SYNDROME: CLINICAL AND CYTOGENETIC STUDIES IN 8 EGYPTIAN PATIENTS AND MOLECULAR STUDIES IN 4 PATIENTS WITH GENOTYPE/PHENOTYPE CORRELATION

The Roberts syndrome (RBS) is a rare autosomal recessive disorder caused by mutation in ESCO2 gene. Among over 150 reported international cases, 16 cases are Egyptian including the presently reported patients. The current study reports 8 new Egyptian patients from 7 unrelated consanguineous families investigating clinical phenotype as well as cytogenetic changes in all cases and mutational spectrum in 4 cases. Clinical, orodental, cytogenetic and molecular studies were done to investigate genotype/phenotype correlation. Evaluation of the studied 8 patients showed that they all exhibited the main limb and craniofacial features of Roberts syndrome. Cytogenetic studies including centromeric separation and puffing by Giemsa and DAPI stains and for the first time in Egypt analysis for premature centromeric division by FISH showed consistent centromeric separation in all studied cases. Molecular studies of 4 available patients showed that they all have ESCO2 gene mutation. We conclude that RBS has a well-defined clinical spectrum. The cytogenetic changes are due to sister chromatid cohesion defects which lead to mitotic dysfunction. We confirmed previous results of lack of genotype/phenotype correlation. We also confirmed that the severity of limb malformation correlates with craniofacial manifestations. We recommend detailed evaluation of orodental changes for further definition of the phenotype and for proper patient management. We emphasize the need for further studies for the frequency of premature centromeric separation by FISH as a possible indicator of phenotypic severity.

The N- and C-terminal ends of RPGR can bind to PDE6δ

This study shows that the prenylated C‐terminus of RPGR can bind to PDE6δ with high affinity, suggesting two distinct binding sites of the RPGR/PDE6δ complex. The serine residue at the −3 position relative to the prenylated cysteine seems to play a key role in defining the selectivity of PDE6δ towards ciliary prenylated cargo.

Reclamation from palm oil mill effluent using an integrated zero discharge membrane-based process

This research emphasizes eloquently on membrane technology for treatment of palm oil mill effluent (POME) as it is the Malaysia’s largest and most important agro based industry. Findings established significant quality improvement with an efficient recovery of water from palm oil mill via innovative membrane application. Conventional bio-methods, whilst adhering to the Department of Environment’s (DOE) discharge regulations, produces brownish liquid which pales in comparison to the crystal clear water obtained through membrane treatment. The pre-treatment process consists of coagulation-flocculation using green environmental coagulant bases such as Moringa oleifera (MO) seeds. The ultrafiltration polyvinylidene difluoride (PVDF) and thin film composite (TFC) reverse osmosis were vital for the membrane processes. The system gave 99% suspended solids reduction in suspended solid and 78% of water present was successfully recovered. This technology guarantees water recovery with drinking water quality; meeting the US Environmental Protection Agency (USEPA) standard or could be recycled into the plant with sludge utilization for palm oil estates, thus enabling the concept of zero discharge to be executed in the industries. In addition, green and healthy antioxidants such as oil and beta-carotene can be recovered from POME further demonstrate. Silica gel showed better performance in separation of carotenes from oil at temperature 40°C using adsorption chromatography with 1154.55 ppm. The attractiveness of this technology, enabling the utilization of reuse of agricultural waste into potentially value added products.

Summary of the National Advisory Committee on Immunization's Update on the recommended human papillomavirus (HPV) vaccine immunization schedule

BACKGROUND

Human papillomavirus (HPV) infections are the most common sexually transmitted infections. In the absence of vaccination, it is estimated that 75% of sexually active Canadians will have a sexually transmitted HPV infection at some point in their lives. Canada's National Advisory Committee on Immunization (NACI) has recommended a three-dose immunization schedule with HPV vaccine for females 9 years of age and older and for males between 9 and 26 years of age, since 2007 and 2012, respectively.

OBJECTIVE

To outline the evidence on a two-dose HPV vaccine schedule and to make recommendations for the optimal HPV immunization schedule in Canada.

METHODS

NACI reviewed the evidence used by the World Health Organization's (WHO's) Strategic Advisory Group of Experts (SAGE) on Immunization for the two-dose HPV immunization schedule recommended for immunocompetent girls 9 to 14 years of age and conducted an additional review of literature for studies not included in, or published after, the SAGE review. A knowledge synthesis was performed then NACI approved specific recommendations and elucidated the rationale and relevant considerations.

RESULTS

Based on the evidence available to date, a two-dose HPV immunization schedule among immunocompetent 9- to 14-year-olds is expected to provide similar protective efficacy compared to a three-dose schedule in immunocompetent individuals aged 9 to 26 years. While all studies reviewed included only females, there is no reason to believe that the data would be different in males, given that data from three-dose trials demonstrates similar immune responses. Administration of two doses of HPV vaccine rather than three may increase acceptability by students, parents and health care professionals alike, and may lead to improved HPV immunization coverage and efficiencies by public health agencies. The duration of protection of either two doses or three doses of HPV vaccine is not yet known; research is encouraged to determine whether there is need for a booster dose.

CONCLUSION

Based on the evidence available to date, a two-dose HPV immunization schedule (given at least six months apart) among immunocompetent 9- to 14-year-olds may be considered by individuals and jurisdictions to allow for potential cost savings and other individual and programmatic advantages. A three-dose schedule should be used in individuals 15 years of age and older, as well as immunocompromised individuals and immunocompetent HIV-infected individuals. The new and complete set of current recommendations for HPV vaccines will be published in the updated HPV chapter in the Canadian Immunization Guide in the near future.