Predictions of Gibbs free energies for the adsorption of polyaromatic and nitroaromatic environmental contaminants on carbonaceous materials: efficient computational approach

The adsorption of benzene, polycyclic aromatic hydrocarbons (PAHs), and nitroaromatic compounds (NACs) on the carbonaceous surfaces from the gas phase and water solution was investigated. Several different levels of theory were applied, including DFT-, MP2-, and CCSD(T)-based methods, to find an approach that is computationally inexpensive and can provide accurate thermodynamic parameters for studied adsorption phenomena. The methods and techniques used (including cluster and periodic approximations) were evaluated on the basis of comparison with available experimental data. The optimized structures of calculated complexes are obtained, and the interaction energies and Gibbs free energies are predicted. Good agreement was revealed for the theoretical and experimental adsorption energies of benzene and PAHs adsorbed on the carbon surfaces. The adsorption of benzene, PAHs, and NACs on carbon is suggested to be effective from the gas phase for all studied compounds and for PAHs and NACs also from water solution at room temperature.

Targeting cancer cells: controlling the binding and internalization of antibody-functionalized capsules

The development of nanoengineered particles, such as polymersomes, liposomes, and polymer capsules, has the potential to offer significant advances in vaccine and cancer therapy. However, the effectiveness of these carriers has the potential to be greatly improved if they can be specifically delivered to target cells. We describe a general method for functionalizing nanoengineered polymer capsules with antibodies using click chemistry and investigate their interaction with cancer cells in vitro. The binding efficiency to cells was found to be dependent on both the capsule-to-cell ratio and the density of antibody on the capsule surface. In mixed cell populations, more than 90% of target cells bound capsules when the capsule-to-target cell ratio was 1:1. Strikingly, greater than 50% of target cells exhibited capsules on the cell surface even when the target cells were present as less than 0.1% of the total cell population. Imaging flow cytometry was used to quantify the internalization of the capsules, and the target cells were found to internalize capsules efficiently. However, the role of the antibody in this process was determined to enhance accumulation of capsules on the cell surface rather than promote endocytosis. This represents a significant finding, as this is the first study into the role antibodies play in internalization of such capsules. It also opens up the possibility of targeting these capsules to cancer cells using targeting molecules that do not trigger an endocytic pathway. We envisage that this approach will be generally applicable to the specific targeting of a variety of nanoengineered materials to cells.

Prognostic ability of 18F-FDG PET/CT in the assessment of colorectal liver metastases

Modern multidisciplinary therapy for colorectal liver metastases (CRLM) is associated with significant morbidity and must be adapted to the patient's relative risk. The tools currently available to risk-stratify patients are limited. This study assessed the prognostic utility of metabolic measurements derived from(18)F-FDG PET compared with previously proposed prognostic scoring systems.

METHODS

Preoperative (18)F-FDG PET/CT studies from a series of 30 patients who underwent liver resection for CRLM after neoadjuvant chemotherapy were evaluated. Quantitative (18)F-FDG PET analysis calculated the maximum and mean standardized uptake value, metabolic tumor volume (MTV), and tumor glycolytic volume (TGV) as measures of the metabolic activity of tumors. The predictive value of these parameters was compared with that of 4 prognostic scores developed by Fong, Iwatsuki, Nordlinger, and Rees.

RESULTS

High MTV and TGV in patients before metastasectomy were significantly associated with poorer overall survival (MTV: P = 0.001; TGV: P = 0.004) and recurrence-free survival (MTV: P = 0.001, TGV; P = 0.002). Maximum and mean standardized uptake value did not show any significant predictive ability. Of the prognostic scores, prediction of outcome was most accurate using the Basingstoke index (area under the curve, 0.898).

CONCLUSION

Assessment of metabolic tumor burden with volumetric (18)F-FDG PET parameters appears to be a valuable adjunct in determining the biology of CRLM before surgical resection and may enable better risk stratification of patients.

Pharmacodynamic analysis of tumour perfusion assessed by 15O-water-PET imaging during treatment with sunitinib malate in patients with advanced malignancies

Background

We evaluated pharmacodynamic changes in tumour perfusion using positron emission tomography (PET) imaging with ¹⁵O-water to assess biological response to sunitinib, a multitargeted tyrosine kinase inhibitor.

Methods

Patients with advanced malignancies received sunitinib 50 mg/day orally, once daily for 4 weeks on treatment, followed by 2 weeks off treatment, in repeated 6-week cycles. Quantitative measurement of tumour perfusion was assessed using ¹⁵O-water-PET at baseline and after 2 weeks of treatment. At least one reference tumour lesion was included in the fields of view and assessed at both time points. Patients also underwent ¹⁸ F-fluorodeoxyglucose (FDG)-PET imaging at baseline and after 2 and 4 weeks of treatment. Radiological response of the reference tumour lesion and overall radiological response were assessed at week 12. Serum pharmacokinetic and biomarker analyses were also performed.

Results

Data were available for seven patients. Compared with baseline, all patients experienced a decrease in reference tumour blood flow ranging from 20 % to 85 % and also a reduction in the FDG standard uptake value ranging from 29 % to 67 %. Six patients experienced a partial metabolic response based on FDG-PET criteria. Four patients had stable disease defined by radiological response (Response Evaluation Criteria in Solid Tumors) lasting between 4 and 12 cycles. An association between perfusion change and clinical benefit, and biomarker levels including vascular endothelial growth factor was observed.

Conclusion

Administering sunitinib to patients with advanced malignancies is associated with early biological responses, including decreased blood flow in secondary tumour deposits.

Targeting of a conformationally exposed, tumor-specific epitope of EGFR as a strategy for cancer therapy

Epidermal growth factor receptor (EGFR) and its most common extracellular mutant, EGFRvIII, are important therapeutic targets in multiple cancer types. A number of monoclonal antibodies and small-molecule inhibitors against these receptors are now used for anticancer treatments. New insights into the structure and function of these receptors illustrate how they can be targeted in novel ways, with expected improvements in the therapeutic efficacy. Monoclonal antibody 806 (mAb806) is an antibody that targets a conformationally exposed epitope of wild-type EGFR when it is overexpressed on tumor cells or in the presence of oncogenic mutations such as EGFRvIII. The mechanism of action of mAb806, which allows for EGFR inhibition without normal tissue toxicity, creates opportunities for combination therapy and strongly suggests mAb806 will be a superior targeted delivery system for antitumor agents. Targeting of the epitope for mAb806 also appears to be an improved strategy to inhibit tumors that express EGFRvIII. This concept of conformational epitope targeting by antibodies reflects an underlying interplay between the structure and biology of different conformational forms of the EGFR family.

Therapeutic targeting of the epidermal growth factor receptor in human cancer

The epidermal growth factor receptor (EGFR; also referred to as HER1 or ERBB1), is a member of the type 1 receptor tyrosine kinase family known as the ERBB family. Comprising 4 members-ERBB1, ERBB2 (also known as HER2), ERBB3 (HER3), and ERBB4 (HER4)-these receptors play a principal role in allowing cells to integrate and respond correctly to diverse external stimuli, ranging from soluble endocrine and paracrine factors to signaling molecules on neighboring cells. The cell must interpret these extracellular signals to produce an appropriate developmental or proliferative response, and aberrant activation of the kinase activity of these receptors, particularly EGFR and ERBB2, is important in the development and progression of human cancer. Given its roles in signal transduction and development of the malignant phenotype, EGFR has emerged as a critical target for therapeutic development against various forms of cancer. This review focuses on the current therapeutic approaches directed against EGFR, the emerging challenges of EGFR therapy resistance, and how our increasing knowledge of EGFR biology is driving more targeted or alternative approaches to cancer therapies.

Non-agonistic bivalent antibodies that promote c-MET degradation and inhibit tumor growth and others specific for tumor related c-MET

The c-MET receptor has a function in many human cancers and is a proven therapeutic target. Generating antagonistic or therapeutic monoclonal antibodies (mAbs) targeting c-MET has been difficult because bivalent, intact anti-Met antibodies frequently display agonistic activity, necessitating the use of monovalent antibody fragments for therapy. By using a novel strategy that included immunizing with cells expressing c-MET, we obtained a range of mAbs. These c-MET mAbs were tested for binding specificity and anti-tumor activity using a range of cell-based techniques and in silico modeling. The LMH 80 antibody bound an epitope, contained in the small cysteine-rich domain of c-MET (amino acids 519–561), that was preferentially exposed on the c-MET precursor. Since the c-MET precursor is only expressed on the surface of cancer cells and not normal cells, this antibody is potentially tumor specific. An interesting subset of our antibodies displayed profound activities on c-MET internalization and degradation. LMH 87, an antibody binding the loop connecting strands 3d and 4a of the 7-bladed β-propeller domain of c-MET, displayed no intrinsic agonistic activity but promoted receptor internalization and degradation. LMH 87 inhibited HGF/SF-induced migration of SK-OV-3 ovarian carcinoma cells, the proliferation of A549 lung cancer cells and the growth of human U87MG glioma cells in a mouse xenograft model. These results indicate that c-MET antibodies targeting epitopes controlling receptor internalization and degradation provide new ways of controlling c-MET expression and activity and may enable the therapeutic targeting of c-MET by intact, bivalent antibodies.

Antibody therapy of cancer

The use of monoclonal antibodies (mAbs) for cancer therapy has achieved considerable success in recent years. Antibody-drug conjugates are powerful new treatment options for lymphomas and solid tumours, and immunomodulatory antibodies have also recently achieved remarkable clinical success. The development of therapeutic antibodies requires a deep understanding of cancer serology, protein-engineering techniques, mechanisms of action and resistance, and the interplay between the immune system and cancer cells. This Review outlines the fundamental strategies that are required to develop antibody therapies for cancer patients through iterative approaches to target and antibody selection, extending from preclinical studies to human trials.

Dual targeting of the epidermal growth factor receptor using the combination of cetuximab and erlotinib: preclinical evaluation and results of the phase II DUX study in chemotherapy-refractory, advanced colorectal cancer

PURPOSE

This preclinical and phase II study evaluated the efficacy and safety of the combination of cetuximab and erlotinib in metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

The activity and mechanism of action of the combination of cetuximab plus erlotinib were investigated in vitro in colorectal cancer cell lines. In the clinical study, patients with chemotherapy-refractory mCRC were treated with cetuximab 400 mg/m(2) as a loading dose and then weekly cetuximab 250 mg/m(2) with erlotinib 100 mg orally daily. The primary end point was response rate (RR), which was evaluated separately in KRAS wild-type (WT) versus KRAS mutant tumors. Secondary end points included toxicity, progression-free survival (PFS), and overall survival. Target accrual was 50 patients, with a one-stage design.

RESULTS

Preclinical studies demonstrated synergistic activity of cetuximab and erlotinib cotreatment on growth inhibition of colon cancer cell lines both as a result of enhanced inhibition of the epidermal growth factor receptor pathway and differential effects on STAT3. In the clinical study, 50 patients were enrolled, with 48 patients evaluable for response. The overall RR was 31% (95% CI, 26% to 57%), with a median PFS of 4.6 months (95% CI, 2.8 to 5.6 months). RR was 41% (95% CI, 26% to 57%) in KRAS WT tumors, with a median PFS of 5.6 months (95% CI, 2.9 to 5.6 months). There was no response in 11 patients with KRAS mutations. Frequent grade 3 and 4 toxicities were rash (48%), hypomagnesaemia (18%), and fatigue (10%).

CONCLUSION

The combination of cetuximab and erlotinib synergistically inhibits growth of colon cancer cell lines, achieves promising efficacy in patients with KRAS WT mCRC, and merits evaluation in further randomized studies.

Activation of Src induces mitochondrial localisation of de2-7EGFR (EGFRvIII) in glioma cells: implications for glucose metabolism

A common mutation of the epidermal growth factor receptor in glioma is the de2-7EGFR (or EGFRvIII). Glioma cells expressing de2-7EGFR contain an intracellular pool of receptor with high levels of mannose glycosylation, which is consistent with delayed processing. We now show that this delay occurs in the Golgi complex. Low levels of de2-7EGFR were also seen within the mitochondria. Src activation dramatically increased the amount of mitochondrial de2-7EGFR, whereas its pharmacological inhibition caused a significant reduction. Because de2-7EGFR is phosphorylated by Src at Y845, we generated glioma cells expressing a Y845F-modified de2-7EGFR. The de2-7EGFR(845F) mutant failed to show mitochondrial localisation, even when co-expressed with constitutive active Src. Low levels of glucose enhanced mitochondrial localisation of de2-7EGFR, and glioma cells expressing the receptor showed increased survival and proliferation under these conditions. Consistent with this, de2-7EGFR reduced glucose dependency by stimulating mitochondrial oxidative metabolism. Thus, the mitochondrial localisation of de2-7EGFR contributes to its tumorigenicity and might help to explain its resistance to some EGFR-targeted therapeutics.

Macromolecule functionalization of disulfide-bonded polymer hydrogel capsules and cancer cell targeting

We present a generic and versatile method for functionalization of disulfide-stabilized PMA hydrogel capsules (HCs) with macromolecules, including a number of specific antibodies to cancer cells. Functionalization was achieved by reversible addition-fragmentation chain transfer (RAFT) polymerization of poly(N-vinyl pyrrolidone) (PVPON), which introduced biorelevant heterotelechelic end groups (thiol and amine) to the polymer chain. The PVPON with heterotelechelic end groups was conjugated to the outermost layer of PMA HCs through the thiol groups and reacted with biotin via the amine groups to generate PMA/PVPON(biotin) HCs. On the basis of the high specific interaction and high affinity between biotin and avidin, and its derivates, such as NeutrAvidin (NAv), we functionalized the PMA HCs with biotinylated antibodies. We demonstrate significantly enhanced cellular binding and internalization of the antibody (Ab)-functionalized capsules compared with control human immunoglobulin (IgG)-functionalized capsules, suggesting these capsules can specifically interact with cells through antibody/antigen recognition. We anticipate that the versatility of the functionalization approach reported in this study will assist in targeted therapeutic delivery applications.

Humanized Lewis-Y specific antibody based delivery of STAT3 siRNA

The clinical application of siRNA is limited largely by the lack of efficient, cell-specific delivery systems. Antibodies are attractive delivery vehicles for targeted therapy due to their high specificity. In this study we describe the use of a humanized monoclonal antibody (mAb), hu3S193, against Lewis-Y (Le(y)), as a delivery vehicle for STAT3 siRNA. This mAb is rapidly internalized into Le(y)-expressing cancer cells via antigen recognition, and when coupled to STAT3 siRNA, a potentially powerful molecularly targeted delivery agent is created. Selective silencing of STAT3 is associated with tumor suppression. Two hu3S193 based siRNA delivery systems using STAT3 siRNA as a prototype were developed and tested in Le(y)-positive cancer cells: (a) a covalent construct based on a reductive disulfide linker that is expected to undergo cleavage within cells and (b) a noncovalent construct based on (d-arginine)(9) (9r) modified hu3S193. Le(y)-specific binding and internalization of both the covalent and noncovalent constructs were confirmed by flow cytometry and confocal microscopy. Both the covalent and the noncovalent system led to efficient STAT3 silencing in Le(y)-positive cancer cells (A431) but not in Le(y)-negative cancer cells (MDA-MB-435). The covalent construct, however, required co-treatment with reagents such as chloroquine or 9r that facilitate the escape of the siRNA from endosomes to achieve significant gene silencing. The 9r modified noncovalent construct induced ∼70% STAT3 knockdown at submicromolar siRNA concentrations when used at an optimal vehicle-to-siRNA ratio of 5:1. The STAT3 knockdown also led to ∼50% inhibition of cell proliferation of Le(y)-positive cells. Noncovalent linked STAT3 siRNA-hu3S193 has great promise for targeted knockdown of STAT3 in tumor cells.

Structural basis for Fc gammaRIIa recognition of human IgG and formation of inflammatory signaling complexes

The interaction of Abs with their specific FcRs is of primary importance in host immune effector systems involved in infection and inflammation, and are the target for immune evasion by pathogens. FcγRIIa is a unique and the most widespread activating FcR in humans that through avid binding of immune complexes potently triggers inflammation. Polymorphisms of FcγRIIa (high responder/low responder [HR/LR]) are linked to susceptibility to infections, autoimmune diseases, and the efficacy of therapeutic Abs. In this article, we define the three-dimensional structure of the complex between the HR (arginine, R134) allele of FcγRIIa (FcγRIIa-HR) and the Fc region of a humanized IgG1 Ab, hu3S193. The structure suggests how the HR/LR polymorphism may influence FcγRIIa interactions with different IgG subclasses and glycoforms. In addition, mutagenesis defined the basis of the epitopes detected by FcR blocking mAbs specific for FcγRIIa (IV.3), FcγRIIb (X63-21), and a pan FcγRII Ab (8.7). The epitopes detected by these Abs are distinct, but all overlap with residues defined by crystallography to contact IgG. Finally, crystal structures of LR (histidine, H134) allele of FcγRIIa and FcγRIIa-HR reveal two distinct receptor dimers that may represent quaternary states on the cell surface. A model is presented whereby a dimer of FcγRIIa-HR binds Ag-Ab complexes in an arrangement that possibly occurs on the cell membrane as part of a larger signaling assembly.

Glioma Specific Extracellular Missense Mutations in the First Cysteine Rich Region of Epidermal Growth Factor Receptor (EGFR) Initiate Ligand Independent Activation

The epidermal growth factor receptor (EGFR) is overexpressed or mutated in glioma. Recently, a series of missense mutations in the extracellular domain (ECD) of EGFR were reported in glioma patients. Some of these mutations clustered within a cysteine-rich region of the EGFR targeted by the therapeutic antibody mAb806. This region is only exposed when EGFR activates and appears to locally misfold during activation. We expressed two of these mutations (R324L and E330K) in NR6 mouse fibroblasts, as they do not express any EGFR-related receptors. Both mutants were autophosphorylated in the absence of ligand and enhanced cell survival and anchorage-independent and xenograft growth. The ECD truncation that produces the de2-7EGFR (or EGFRvIII), the most common EGFR mutation in glioma, generates a free cysteine in this same region. Using a technique optimized for detecting disulfide-bonded dimers, we definitively demonstrated that the de2-7EGFR is robustly dimerized and that ablation of the free cysteine prevents dimerization and activation. Modeling of the R324L mutation suggests it may cause transient breaking of disulfide bonds, leading to similar disulfide-bonded dimers as seen for the de2-7EGFR. These ECD mutations confirm that the cysteine-rich region of EGFR around the mAb806 epitope has a significant role in receptor activation.

Differential and synergistic effects of epidermal growth factor receptor antibodies on unliganded ErbB dimers and oligomers

Antibodies directed against the epidermal growth factor receptor (EGFR) offer a potentially powerful therapeutic approach against cancers driven by the EGFR pathway. EGFR antibodies are believed to halt cell surface activation by blocking ligand-induced receptor tyrosine kinase activation, i.e., ligand binding, a change in conformation, or the monomer-dimer transition. In this work, we demonstrate that wild-type EGFR and the truncated de2-7-EGFR (tumor-associated mutant) formed unliganded homo-oligomers and examined the effects of two clinically relevant antibodies on the conformation and quaternary state of these ligand-free EGFR oligomers on the surface of cells. The EGFR antibodies were mAb528, a ligand-blocking antibody that binds domain III, and mAb806, a conformationally sensitive antibody that binds near the dimer interface in domain II. We used a model cellular system, BaF/3 cells, with GFP-tagged receptors in the absence of interference from secreted ligands or other erbB receptor members. Different antibody-mediated effects (conformational transition, receptor cross-linking, or receptor dissociation) were distinguished by combining two complementary biophysical techniques: image correlation spectroscopy (submicrometer scale clustering) and homo-Forster resonance energy transfer (association and/or conformation on a 1-10 nm scale). mAb528 cross-linked EGFR into an inactive EGFR dimer of dimers but had no effect when added to de2-7-EGFR oligomers. mAb806 had a minor effect on EGFR dimers as expected from its poor binding to a conformationally shielded epitope on wtEGFR but bound de2-7-EGFR oligomers, causing a conformational change in the intracellular C-terminal GFP-tagged tail. The combination of the two antibodies had synergistic effects, increasing the level of cross-linking of de2-7-EGFR, but did not lead to enhanced cross-linking of EGFR. The results reveal new modes of receptor-antibody interactions for EGFR and de2-7-EGFR.

Abstract 5318: Optimizing pharmacokinetics and targeting properties of recombinant anti-Lewis Y antibody hu3S193 in A431 tumor-bearing mice

Aim: The humanized monoclonal antibody 3S193 (hu3S193) specifically binds the Lewis Y (Ley) antigen and has shown a long half-life in Phase I first-in-man trials. Previous results have shown that mutations in residues I253, H310 and H435 of the Fc region interfere with the neonatal receptor (FcRn) binding. We have generated a hu3S193 antibody with an alanine mutation in residue I253 (I253A) that shows a shorter half-life than parental hu3S193. The objective of this pilot study was to evaluate the radiolabeling properties of 89Zr-labelled hu3S193_I253A compared to its parent hu3S193 and evaluate them as small-animal positron emission tomography (PET) imaging agents.

Methods: Site-directed mutagenesis was performed using a QuickChange XL II site-directed mutagenesis kit (Stratagene) to generate the hu3S193_I253A. The LONZA Glutamine Synthetase expression system was used for eukaryotic expression of antibody heavy and kappa light chain vectors. Mutants were produced in transient (Freestyle 293, Invitrogen) cells and tested for Ley binding using ELISA, FACS and BIAcore analysis. Parental hu3S193 and hu3S193_I253A were radiolabelled with 89Zr after conjugation to deferroxamine-p-SCN (Df). The 89Zr-Df-labelled antibodies were evaluated in small-animal PET studies at 4, 24, 48, and 72 hours post injection. At 72 hours after injection, animals were sacrificed. Blood samples were taken via cardiac puncture and organs were removed. Blood and organ samples were counted for radioactivity.

Results: Analysis of hu3S193_I253A mutant by ELISA, BIAcore and FACS showed retention of Ley antigen binding ability. PET imaging demonstrated specific tumor uptake of both 89Zr-Df-labeled parental and hu3S193_I253A at 24 hours post injection and this uptake was maintained for 6 days after injection. Lesions as small as 16 mm3 were clearly detected with both agents. Higher uptake in the liver was detected when using 89Zr-Df-labeled hu3S193_I253A. The 72 hour biodistribution data displayed a higher non-specific uptake in the liver with hu3S193_I253A versus parental (i.e. 15 %ID/g versus 6 %ID/g respectively). For comparison, using 111In-CHX-A”-hu3S193_I253A liver uptake was 7 ± 0.3 %ID/g. This observation indicates that improvement to the 89Zr-labelling chemistry could reduce the liver uptake of faster clearing hu3S193 constructs.

Conclusion: The pilot study of 89Zr-labelled hu3S193 and hu3S193_I253A demonstrated excellent tumor uptake of both agents, with high-contrast images generated of lesions as small as 16mm3. Improvements in 89Zr radiolabelling chemistry may be required to optimize imaging of fast clearing recombinant antibodies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5318. doi:10.1158/1538-7445.AM2011-5318