Pharmacological eEF2K activation promotes cell death and inhibits cancer progression

Activation of the elongation factor 2 kinase (eEF2K) leads to the phosphorylation and inhibition of the elongation factor eEF2, reducing mRNA translation rates. Emerging evidence indicates that the regulation of factors involved in protein synthesis may be critical for controlling diverse biological processes including cancer progression. Here we show that inhibitors of the HIV aspartyl protease (HIV‐PIs), nelfinavir in particular, trigger a robust activation of eEF2K leading to the phosphorylation of eEF2. Beyond its anti‐viral effects, nelfinavir has antitumoral activity and promotes cell death. We show that nelfinavir‐resistant cells specifically evade eEF2 inhibition. Decreased cell viability induced by nelfinavir is impaired in cells lacking eEF2K. Moreover, nelfinavir‐mediated anti‐tumoral activity is severely compromised in eEF2K‐deficient engrafted tumors in vivo. Our findings imply that exacerbated activation of eEF2K is detrimental for tumor survival and describe a mechanism explaining the anti‐tumoral properties of HIV‐PIs.     

PLX3397 inhibits the accumulation of intra‐tumoral macrophages and improves bromodomain and extra‐terminal inhibitor efficacy in melanoma

Bromodomain and extra‐terminal inhibitors (BETi) delay tumor growth, in part, through tumor cell intrinsic alterations and initiation of anti‐tumor CD8+ T‐cell responses. By contrast, BETi effects on pro‐tumoral immune responses remain unclear. Here, we show that the next‐generation BETi, PLX51107, delayed tumor growth to differing degrees in Braf V600E melanoma syngeneic mouse models. These differential responses were associated with the influx of tumor‐associated macrophages during BETi treatment. Tumors that were poorly responsive to PLX51107 showed increased influx of colony‐stimulating factor‐1 receptor (CSF‐1R)‐positive tumor‐associated macrophages. We depleted CSF‐1R+ tumor‐associated macrophages with the CSF‐1R inhibitor, PLX3397, in combination with PLX51107. Treatment with PLX3397 enhanced the efficacy of PLX51107 in poorly responsive Braf V600E syngeneic melanomas in vivo. These findings suggest that tumor‐associated macrophage accumulation limits BETi efficacy and that co‐treatment with PLX3397 can improve response to PLX51107, offering a potential novel combination therapy for metastatic melanoma patients.     

New, potent P1/P2-morpholinone-based HIV-protease inhibitors

We have developed efficient synthesis of morpholinone-based cyclic mimetics of the P1/P2 portion of the HIV-1 protease inhibitor Amprenavir. This effort led to discovery of allyl- and spiro-cyclopropyl-P2-substituted inhibitors 17 and 31, both 500 times more potent than the parent inhibitor 1. These results support morpholinones as novel mimetics of the P1/P2 portion of Amprenavir and potentially of other HIV-protease inhibitors, and thus provide a novel medicinal chemistry template for optimization toward more potent and drug-like inhibitors.     

Role of FAP48 in HIV-associated lipodystrophy

The highly active antiretroviral therapy (HAART) can cause a metabolic syndrome consisting of lipodystropy/lipoatrophy, dyslipidemia, and type 2 diabetes mellitus with an increased cardiovascular risk. The pathogenetic bases of HAART‐associated lipodystrophy are poorly known. A genetic screen was used to evaluate proteins that are modulated in HIV‐1‐infected patients with or without lipodystrophy syndrome, that are routinely treated with HAART regimens. The most significant modulation was represented by FAP48 expression. Stable over‐expression of FAP48 was able to alter, in vitro, adipogenesis, acting both on calcineurin and glucocorticoid pathways. Finally, we demonstrated that FAP48 over‐expression was able to influence the capacity of some HIV drugs, Saquinavir and Efavirenz, but not Stavudine, Amprenavir, and Indinavir to inhibit adipocyte formation. In conclusion, this molecule could be a potential target for novel therapeutic approaches to the HAART related lipodystrophy in HIV patients. J. Cell. Biochem. 113: 3446–3454, 2012. © 2012 Wiley Periodicals, Inc.     

Modulation of the LDL receptor and LRP levels by HIV protease inhibitors

Inhibitors of the human immunodeficiency virus (HIV)-1 protease have proven to be effective antiretroviral drugs. However, patients receiving these drugs develop serious metabolic abnormalities, including hypercholesterolemia. The objective of the present study was to identify mechanisms by which HIV protease inhibitors increase plasma cholesterol levels. We hypothesized that HIV protease inhibitors may affect gene regulation of certain LDL receptor (LDLR) family members, thereby altering the catabolism of cholesterol-containing lipoproteins. In this present study we investigated the effect of several HIV protease inhibitors (ABT-378, Amprenavir, Indinavir, Nelfinavir, Ritonavir, and Saquinavir) on mRNA, protein, and functional levels of LDLR family members. Our results demonstrate that one of these drugs, Nelfinavir, significantly decreases LDLR and LDLR-related protein (LRP) mRNA and protein levels, resulting in the reduced functional activity of these two receptors. Nelfinavir exerts its effect by reducing levels of active SREBP1 in the nucleus. The finding that Nelfinavir reduces the levels of two key receptors (LRP and LDLR) involved in lipoprotein catabolism and maintenance of vessel wall integrity identifies a mechanism that causes hypercholesterolemia complications in HIV patients treated with this drug and raises concerns about the atherogenic nature of Nelfinavir.     

A novel anti‐HIV‐1 bispecific bNAb‐lectin fusion protein engineered in a plant‐based transient expression system

The discovery of broadly neutralizing antibodies (bNAbs) has been a major step towards better prophylactic and therapeutic agents against human immunodeficiency virus type 1 (HIV‐1). However, effective therapy will likely require a combination of anti‐HIV agents to avoid viral evasion. One possible solution to this problem is the creation of bispecific molecules that can concurrently target two vulnerable sites providing synergistic inhibitory effects. Here, we describe the production in plants and anti‐HIV activity of a novel bispecific fusion protein consisting of the antigen‐binding fragment (Fab) of the CD4 binding site‐specific bNAb VRC01 and the antiviral lectin Avaren, which targets the glycan shield of the HIV‐1 envelope (VRC01_Fab‐Avaren). This combination was justified by a preliminary experiment demonstrating the synergistic HIV‐1 neutralization activity of VRC01 and Fc‐fused Avaren dimer (Avaren‐Fc). Using the GENEWARE^® tobacco mosaic virus vector, VRC01_Fab‐Avaren was expressed in Nicotiana benthamiana and purified using a three‐step chromatography procedure. Surface plasmon resonance and ELISA demonstrated that both the Avaren and VRC01_Fab moieties retain their individual binding specificities. VRC01_Fab‐Avaren demonstrated enhanced neutralizing activity against representative HIV‐1 strains from A, B and C clades, compared to equimolar combinations of VRC01_Fab and Avaren. Notably, VRC01_Fab‐Avaren showed significantly stronger neutralizing effects than the bivalent parent molecules VRC01 IgG and Avaren‐Fc, with IC₅₀ values ranging from 48 to 310 pm . These results support the continued development of bispecific anti‐HIV proteins based on Avaren and bNAbs, to which plant‐based transient overexpression systems will provide an efficient protein engineering and production platform.     

Polyethylenimine/small interfering RNA‐mediated knockdown of vascular endothelial growth factor in vivo exerts anti‐tumor effects synergistically with Bevacizumab

Background

RNA interference is a powerful method for the knockdown of pathologically relevant genes. The in vivo delivery of siRNAs, preferably through systemic, nonviral administration, poses the major challenge in the therapeutic application of RNAi. Small interfering RNA (siRNA) complexation with polyethylenimines (PEI) may represent a promising strategy for siRNA‐based therapies and, recently, the novel branched PEI F25‐LMW has been introduced in vitro. Vascular endothelial growth factor (VEGF) is frequently overexpressed in tumors and promotes tumor growth, angiogenesis and metastasis and thus represents an attractive target gene in tumor therapy.

Methods

In subcutaneous tumor xenograft mouse models, we established the therapeutic efficacy and safety of PEI F25‐LMW/siRNA‐mediated knockdown of VEGF. In biodistribution and siRNA quantification studies, we optimized administration strategies and, employing chemically modified siRNAs, compared the anti‐tumorigenic efficacies of: (i) PEI/siRNA‐mediated VEGF targeting; (ii) treatment with the monoclonal anti‐VEGF antibody Bevacizumab (Avastin®); and (iii) a combination of both.

Results

Efficient siRNA delivery is observed upon systemic administration, with the biodistribution being dependent on the mode of injection. Toxicity studies reveal no hepatotoxicity, proinflammatory cytokine induction or other side‐effects of PEI F25‐LMW/siRNA complexes or polyethylenimine, and tumor analyses show efficient VEGF knockdown upon siRNA delivery, leading to reduced tumor cell proliferation and angiogenesis. The determination of anti‐tumor effects reveals that, in pancreas carcinoma xenografts, single treatment with PEI/siRNA complexes or Bevacizumab is already highly efficacious, whereas, in prostate carcinoma, synergistic effects of both treatments are observed.

Conclusions

PEI F25‐LMW/siRNA complexes, which can be stored frozen as opposed to many other carriers, represent an efficient, safe and promising avenue in anti‐tumor therapy, and PEI/siRNA‐mediated, therapeutic VEGF knockdown exerts anti‐tumor effects. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic antitumor effects of novel HDAC inhibitors and paclitaxel in vitro and in vivo

Preclinical studies support the therapeutic potential of histone deacetylases inhibitors (HDACi) in combination with taxanes. The efficacy of combination has been mainly ascribed to a cooperative effect on microtubule stabilization following tubulin acetylation. In the present study we investigated the effect of paclitaxel in combination with two novel HDACi, ST2782 or ST3595, able to induce p53 and tubulin hyperacetylation. A synergistic effect of the paclitaxel/ST2782 (or ST3595) combination was found in wild-type p53 ovarian carcinoma cells, but not in a p53 mutant subline, in spite of a marked tubulin acetylation. Such a synergistic interaction was confirmed in additional human solid tumor cell lines harboring wild-type p53 but not in those expressing mutant or null p53. In addition, a synergistic cytotoxic effect was found when ST2782 was combined with the depolymerising agent vinorelbine. In contrast to SAHA, which was substantially less effective in sensitizing cells to paclitaxel-induced apoptosis, ST2782 prevented up-regulation of p21(WAF1/Cip1) by paclitaxel, which has a protective role in response to taxanes, and caused p53 down-regulation, acetylation and mitochondrial localization of acetylated p53. The synergistic antitumor effects of the paclitaxel/ST3595 combination were confirmed in two tumor xenograft models. Our results support the relevance of p53 modulation as a major determinant of the synergistic interaction observed between paclitaxel and novel HDACi and emphasize the therapeutic interest of this combination.     

Overcoming drug resistance in HIV-1 chemotherapy: the binding thermodynamics of Amprenavir and TMC-126 to wild-type and drug-resistant mutants of the HIV-1 protease

Amprenavir is one of six protease inhibitors presently approved for clinical use in the therapeutic treatment of AIDS. Biochemical and clinical studies have shown that, unlike other inhibitors, Amprenavir is severely affected by the protease mutation I50V, located in the flap region of the enzyme. TMC-126 is a second-generation inhibitor, chemically related to Amprenavir, with a reported extremely low susceptibility to existing resistant mutations including I50V. In this paper, we have studied the thermodynamic and molecular origin of the response of these two inhibitors to the I50V mutation and the double active-site mutation V82F/I84V that affects all existing clinical inhibitors. Amprenavir binds to the wild-type HIV-1 protease with high affinity (5.0 x 10(9) M(-1) or 200 pM) in a process equally favored by enthalpic and entropic contributions. The mutations I50V and V82F/I84V lower the binding affinity of Amprenavir by a factor of 147 and 104, respectively. TMC-126, on the other hand, binds to the wild-type protease with extremely high binding affinity (2.6 x 10(11) M(-1) or 3.9 pM) in a process in which enthalpic contributions overpower entropic contributions by almost a factor of 4. The mutations I50V and V82F/I84V lower the binding affinity of TMC-126 by only a factor of 16 and 11, respectively, indicating that the binding affinity of TMC-126 to the drug-resistant mutants is still higher than the affinity of Amprenavir to the wild-type protease. Analysis of the data for TMC-126 and KNI-764, another second-generation inhibitor, indicates that their low susceptibility to mutations is caused by their ability to compensate for the loss of interactions with the mutated target by a more favorable entropy of binding.     

Visualization of human immunodeficiency virus protease inhibition using a novel Förster resonance energy transfer molecular probe

The in vivo high‐throughput screening (HTS) of human immunodeficiency virus (HIV) protease inhibitors is a significant challenge because of the lack of reliable assays that allow the visualization of HIV targets within living cells. In this study, we developed a new molecular probe that utilizes the principles of Förster resonance energy transfer (FRET) to visualize HIV‐1 protease inhibition within living cells. The probe is constructed by linking two fluorescent proteins: AcGFP1 (a mutant green fluorescent protein) and mCherry (a red fluorescent protein) with an HIV‐1 protease cleavable p2/p7 peptide. The cleavage of the linker peptide by HIV‐1 protease leads to separation of AcGFP1 from mCherry, quenching FRET between AcGFP1 and mCherry. Conversely, the addition of a protease inhibitor prevents the cleavage of the linker peptide by the protease, allowing FRET from AcGFP1 to mCherry. Thus, HIV‐1 protease inhibition can be determined by measuring the FRET signal's change generated from the probe. Both in vitro and in vivo studies demonstrated the feasibility of applying the probe for quantitative analyses of HIV‐1 protease inhibition. By cotransfecting HIV‐1 protease and the probe expression plasmids into 293T cells, we showed that the inhibition of HIV‐1 protease by inhibitors can be visualized or quantitatively determined within living cells through ratiometric FRET microscopy imaging measurement. It is expected that this new probe will allow high‐content screening (HCS) of new anti‐HIV drugs. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011     

Relation between flexibility and positively selected HIV‐1 protease mutants against inhibitors

The antiretroviral chemotherapy helps to reduce the mortality of HIVs infected patients. However, RNA dependant virus replication has a high mutation rate. Human immunodeficiency virus Type 1 protease plays an essential role in viral replication cycle. This protein is an important target for therapy with viral protein inhibitors. There are few works using normal mode analysis to investigate this problem from the structural changes viewpoint. The investigation of protein flexibility may be important for the study of processes associated with conformational changes and state transitions. The normal mode analysis allowed us to investigate structural changes in the protease (such as flexibility) in a straightforward way and try to associate these changes with the increase of fitness for each positively selected HIV‐1 mutant protease of patients treated with several protease inhibitors (saquinavir, indinavir, ritonavir, nelfinavir, lopinavir, fosamprenavir, atazanavir, darunavir, and tripanavir) in combination or separately. These positively selected mutations introduce significant flexibility in important regions such as the active site cavity and flaps. These mutations were also able to cause changes in accessible solvent area. This study showed that the majority of HIV‐1 protease mutants can be grouped into two main classes of protein flexibility behavior. We presented a new approach to study structural changes caused by positively selected mutations in a pathogen protein, for instance the HIV‐1 protease and their relationship with their resistance mechanism against known inhibitors. The method can be applied to any pharmaceutically relevant pathogen proteins and could be very useful to understand the effects of positively selected mutations in the context of structural changes. Proteins 2012; © 2012 Wiley Periodicals, Inc.     

Molecular dissection of an inhibitor targeting the HIV integrase dependent preintegration complex nuclear import

Human immunodeficiency virus (HIV) continues to be a major contributor to morbidity and mortality worldwide, particularly in developing nations where high cost and logistical issues severely limit the use of current HIV therapeutics. This, combined HIV's high propensity to develop resistance, means that new antiviral agents against novel targets are still urgently required. We previously identified novel anti‐HIV agents directed against the nuclear import of the HIV integrase (IN) protein, which plays critical roles in the HIV lifecycle inside the cell nucleus, as well as in transporting the HIV preintegration complex (PIC) into the nucleus. Here we investigate the structure activity relationship of a series of these compounds for the first time, including a newly identified anti‐IN compound, budesonide, showing that the extent of binding to the IN core domain correlates directly with the ability of the compound to inhibit IN nuclear transport in a permeabilised cell system. Importantly, compounds that inhibited the nuclear transport of IN were found to significantly decrease HIV viral replication, even in a dividing cell system. Significantly, budesonide or its analogue flunisolide, were able to effect a significant reduction in the presence of specific nuclear forms of the HIV DNA (2‐LTR circles), suggesting that the inhibitors work though blocking IN, and potentially PIC, nuclear import. The work presented here represents a platform for further development of these specific inhibitors of HIV replication with therapeutic and prophylactic potential.     

Synergistic antitumor effect of a human papillomavirus DNA vaccine harboring E6E7 fusion gene and vascular endothelial growth factor receptor 2 gene

Human papillomavirus (HPV) has been identified as the primary etiological factor in cervical cancer as well as in subsets of anogenital and oropharyngeal cancers. The two HPV viral oncoproteins, E6 and E7, are uniquely and consistently expressed in all HPV‐infected cells and are therefore promising targets for therapeutic vaccination. In order to achieve a synergistic antitumor and anti‐angiogenesis effect, we designed and constructed a novel DNA vaccine that can express the HPV 16 E6E7 fusion protein and VEGFR2 in the same reading frame. A series of DNA plasmids encoding E6E7, VEGFR2 and their conjugates were constructed and injected into mice. The resultant humoral and cellular immune responses were detected by ELISA and enzyme‐linked immunospot (ELISPOT), respectively. To evaluate the antitumor efficacy of these plasmids, tumor‐bearing mice expressing the E6E7 fusion protein were constructed. After injection into the tumor‐bearing mouse model, the plasmid harboring the E6E7 fusion gene and VEGFR2 showed stronger inhibition of tumor growth than the plasmid expressing E6E7 or VEGFR2 alone, which indicated that the combination of E6E7 and VEGFR2 could exert a synergistic antitumor effect. These observations emphasize the potential of a synergistic antitumor and anti‐angiogenesis strategy using a DNA vaccine, which could be a promising approach for tumor immunotherapy.     

HIV protease inhibitors modulate apoptosis signaling <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis>

HIV protease inhibitors are an integral part of effective anti-HIV therapy. The drugs block HIV protease, prevent proper packaging of HIV virions, and decrease the HIV viral burden in the peripheral blood of infected individuals. In addition to direct anti-viral effects, the HIV protease inhibitors also modulate apoptosis. A growing body of work demonstrates the anti-apoptotic effects of HIV protease inhibitors on CD4+ and CD8+ T cells during HIV infection. The mechanism of this apoptosis inhibition is supported by several proposed hypotheses for how they alter the fate of the cell, including preventing adenine nucleotide translocator pore function, which consequently prevents loss of mitochondrial transmembrane potential. More recently, the anti-apoptotic effects of the HIV protease inhibitors have been tested in non-HIV, non-immune cell, whereby protease inhibitors prevent apoptosis, and disease in animal models of sepsis, hepatitis, pancreatitis and stroke. Interestingly, when HIV protease inhibitors are used at supra-therapeutic concentrations, they exert pro-apoptotic effects. This has been demonstrated in a number of tumor models. Although it is unclear how HIV protease inhibitors can induce apoptosis at increased concentrations, future research will define the targets of the immunomodulation and reveal the full clinical potential of this intriguing class of drugs.     

Effects of HIV protease inhibitor therapy on lipid metabolism

Highly active antiretroviral therapy, which includes a combination of protease inhibitors, is highly successful in controlling human immunodeficiency virus (HIV) infection and reducing the morbidity and mortality of autoimmune deficiency syndrome (AIDS). However, the benefits of HIV protease inhibitors are compromised by numerous undesirable side effects. These include peripheral fat wasting and excessive central fat deposition (lipodystrophy), overt hyperlipidemia, and insulin resistance. The mechanism associated with protease inhibitor-induced metabolic abnormalities is multifactorial. One major effect of the protease inhibitor is its suppression of the breakdown of the nuclear form of sterol regulatory element binding proteins (nSREBP) in the liver and adipose tissues. Hepatic accumulation of nSREBP results in increased fatty acid and cholesterol biosynthesis, whereas nSREBP accumulation in adipose tissue causes lipodystrophy, reduces leptin expression, and promotes insulin resistance. The HIV protease inhibitors also suppress proteasome-mediated breakdown of nascent apolipoprotein (apo) B, thus resulting in the overproduction and secretion of triglyceride-rich lipoproteins. Finally, protease inhibitor also suppresses the inhibition of the glucose transporter GLUT-4 activity in adipose and muscle. This latter effect also contributes directly to insulin resistance and diabetes. These adverse effects need to be alleviated for long-term use of protease inhibitor therapy in treatment of HIV infection.     

Oximinoarylsulfonamides as potent HIV protease inhibitors

The need for a potent HIV protease inhibitor (PI) to combat emerging PI-resistant viruses is anticipated. Analogs formulated from the combination of structural fragments of Ritonavir, Lopinavir, and Amprenavir were synthesized. Analogs containing the oxime pharmacophore were found to have improved activities against both wild type and resistant (A17) viruses. The synthesis and structure-activity relationships (SAR) based upon the in vitro IC50 of this series of compounds are reported.     

Treatment of advanced melanoma with laser immunotherapy and ipilimumab

Immunotherapy has become a promising modality for melanoma, especially using checkpoint inhibitors, which revive suppressed T cells against the cancer. Such inhibitors should work better when combined with other treatments which could increase the number and quality of anti‐tumor T cells. We treated one patient with advanced (stage IV) melanoma, using the combination of laser immunotherapy (LIT), a novel immunological approach for metastatic cancers that has been shown to stimulate adaptive immunity, and ipilimumab. The patient was treated with LIT, followed with one course of ipilimumab 3 months after the beginning of LIT. After LIT treatment, all treated cutaneous melanoma in head and neck cleared completely. After the application of ipilimumab, all the tumor nodules in the lungs decreased. The patient had remained tumor free for one year. While anecdotal, the responses seen in this patient support the hypothesis that laser immunotherapy increases the number and quality of anti‐tumor T cells so that ipilimumab and other checkpoint inhibitors are more effective in enhancing the therapeutic effects. Picture : Schematic of treatment using laser immunotherapy and ipilimumab on a stage IV melanoma patient.     

Statins potently reduce the cytokine‐mediated IL‐6 release in SMC/MNC cocultures

Inflammatory pathways are involved in the development of atherosclerosis. Interaction of vessel wall cells and invading monocytes by cytokines may trigger local inflammatory processes. 3‐Hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitors (statins) are standard medications used in cardiovascular diseases. They are thought to have anti‐inflammatory capacities, in addition to their lipid‐lowering effects. We investigated the anti‐inflammatory effect of statins in the cytokine‐mediated‐interaction‐model of human vascular smooth muscle cells (SMC) and human mononuclear cells (MNC). In this atherosclerosis‐related inflammatory model LPS (lipopolysaccharide, endotoxin), as well as high mobility group box 1 stimulation resulted in synergistic (i.e. over‐additive) IL‐6 (interleukin‐6) production as measured in ELISA. Recombinant IL‐1, tumour necrosis factor‐α and IL‐6 mediated the synergistic IL‐6 production. The standard anti‐inflammatory drugs aspirin and indomethacin (Indo) reduced the synergistic IL‐6 production by 60%. Simvastatin, atorvastatin, fluvastatin or pravastatin reduced the IL‐6 production by 53%, 50%, 64% and 60%, respectively. The inhibition by the statins was dose dependent. Combination of statins with aspirin and/or Indo resulted in complete inhibition of the synergistic IL‐6 production. The same inhibitors blocked STAT3 phosphorylation, providing evidence for an autocrine role of IL‐6 in the synergism. MNC from volunteers after 5 day aspirin or simvastatin administration showed no decreased IL‐6 production, probably due to drug removal during MNC isolation. Taken together, the data show that anti‐inflammatory functions (here shown for statins) can be sensitively and reproducibly determined in this novel SMC/MNC coculture model. These data implicate that statins have the capacity to affect atherosclerosis by regulating cytokine‐mediated innate inflammatory pathways in the vessel wall.     

Design and synthesis of novel HIV-1 protease inhibitors incorporating oxyindoles as the P2'-ligands

A series of novel oxyindole-derived HIV-1 protease inhibitors were designed and synthesized based upon our X-ray crystal structure of inhibitor 2 (TMC-114) bound to HIV-1 protease. The effects of substituents, spirocyclic rings, and ring sizes have been investigated. A number of inhibitors exhibited low nanomolar inhibitory potencies against HIV protease.