Monoclonal antibody 14C5 targets integrin alphavbeta5

Probing the recognition specificity of αVβ1 integrin and syndecan-4 using force spectroscopy

The knowledge on how cells interact with microenvironment is particularly important in understanding the interaction of cancer cells with surrounding stroma, which affects cell migration, adhesion, and metastasis. The main cell surface receptors responsible for the interaction with extracellular matrix (ECM) are integrins, however, they are not the only ones. Integrins are accompanied to other molecules such as syndecans. The role of the latter has not yet been fully established. In our study, we would like to answer the question of whether integrins and syndecans, possessing similar functions, share also similar unbinding properties. By using single molecule force spectroscopy (SMFS), we conducted measurements of the unbinding properties of α_Vβ₁ and syndecan-4 in the interaction with vitronectin (VN), which, as each ECM protein, possesses two binding sites specific to integrins and syndecans. The unbinding force and the kinetic off rate constant derived from SMFS describe the stability of single molecular complex. Obtained data show one barrier transition for each complex. The proposed model shows that the unbinding of α_Vβ₁ from VN proceeds before the unbinding of SDC-4. However, despite different unbinding kinetics, the access to both receptors is needed for cell growth and proliferation.

In Vivo Tumor Growth Inhibition and Antiangiogenic Effect of Cyclic NGR Peptide-Daunorubicin Conjugates Developed for Targeted Drug Delivery

Among various homing devices, peptides containing the NGR tripeptide sequence represent a promising approach to selectively recognize CD13 receptor isoforms on the surface of tumor cells. They have been successfully used for the delivery of various chemotherapeutic drugs to tumor vessels. Here, we report on the murine plasma stability, in vitro and in vivo antitumor activity of our recently described bioconjugates containing daunorubicin as payload. Furthermore, CD13 expression of KS Kaposi’s Sarcoma cell line and HT-29 human colon carcinoma cell line was investigated. Flow cytometry studies confirm the fast cellular uptake resulting in the rapid delivery of the active metabolite Dau = Aoa-Gly-OH to tumor cells. The increased in vitro antitumor effect might be explained by the faster rearrangement from NGR to isoDGR in case of conjugate 2 (Dau = Aoa-GFLGK(c[NleNGRE]-GG)-NH₂) in comparison with conjugate 1 (Dau = Aoa-GFLGK(c[KNGRE]-GG)-NH₂). Nevertheless, results indicated that both conjugates showed significant effect on inhibition of proliferation in the primary tumor and also on blood vessel formation making them a potential candidate for targeting angiogenesis processes in tumors where CD13 and integrins are involved.

NGR-peptide-drug conjugates with dual targeting properties

Peptides containing the asparagine-glycine-arginine (NGR) motif are recognized by CD13/aminopeptidase N (APN) receptor isoforms that are selectively overexpressed in tumor neovasculature. Spontaneous decomposition of NGR peptides can result in isoAsp derivatives, which are recognized by RGD-binding integrins that are essential for tumor metastasis. Peptides binding to CD13 and RGD-binding integrins provide tumor-homing, which can be exploited for dual targeted delivery of anticancer drugs. We synthesized small cyclic NGR peptide-daunomycin conjugates using NGR peptides of varying stability (c[KNGRE]-NH2, Ac-c[CNGRC]-NH2 and the thioether bond containing c[CH2-CO-NGRC]-NH2, c[CH2-CO-KNGRC]-NH2). The cytotoxic effect of the novel cyclic NGR peptide-Dau conjugates were examined in vitro on CD13 positive HT-1080 (human fibrosarcoma) and CD13 negative HT-29 (human colon adenocarcinoma) cell lines. Our results confirm the influence of structure on the antitumor activity and dual acting properties of the conjugates. Attachment of the drug through an enzyme-labile spacer to the C-terminus of cyclic NGR peptide resulted in higher antitumor activity on both CD13 positive and negative cells as compared to the branching versions.

Inhibiting Integrin αvβ5 Reduces Ischemia-Reperfusion Injury in an Orthotopic Lung Transplant Model in Mice

Primary graft dysfunction after lung transplantation is the leading cause of morbidity and mortality in the immediate posttransplant period and is characterized by endothelial and epithelial barrier disruption and the leakage of protein-rich edema fluid. Integrins are cell surface receptors that have an important role in maintenance of the cell barrier, and inhibition of integrins, such as αvβ5, can diminish alveolar flooding in lung injury models. We hypothesized that inhibition of αvβ5 during donor lung cold ischemia would reduce endothelial permeability during reperfusion. Using an orthotopic single lung transplantation model with and without cold ischemia, donor lungs were perfused with αvβ5-blocking antibody (ALULA) or control antibody at the time of collection, followed by transplantation, 8 h of reperfusion, and the measurement of lung injury parameters. Prolonged cold ischemia (18 h) produced increases in extravascular lung water, protein permeability, and neutrophilic alveolitis and decreased oxygenation compared with lungs without cold ischemia. Perfusion of lungs with αvβ5 antibody versus control antibody protected donor lungs from injury and significantly improved oxygenation. In summary, αvβ5 integrin blockade protects from the development of ischemia-reperfusion lung injury and is a promising approach to preventing primary graft dysfunction in human lung transplant procedures.

FERM domain-containing protein FRMD5 regulates cell motility via binding to integrin β5 subunit and ROCK1

FRMD5 is a novel FERM domain-containing protein depicted in tumor progression. However, the mechanisms underlying FRMD5 inhibition of cell migration is largely unknown. Here, we show that FRMD5 regulates cell migration by interacting with integrin β5 cytoplasmic tail and ROCK1 in human lung cancer cells. FRMD5 promotes cell-matrix adhesion and cell spreading on vitronectin, and thus inhibits cell migration. Furthermore, FRMD5 interacts with ROCK1 and inhibits its activation that leads to the inhibition of myosin light chain phosphorylation and the actin stress fiber formation. Taken together, these findings demonstrate that the putative tumor suppressive protein FRMD5 regulates tumor cell motility via a dual pathway involving FRMD5 binding to integrin β5 tail and to ROCK1.

Generation and in vivo characterization of a chimeric αvβ5-targeting antibody 14C5 and its derivatives

Background

Previous studies showed that radiolabeled murine monoclonal antibody (mAb) 14C5 and its Fab and F(ab')₂ fragments, targeting α_vβ₅ integrin, have promising properties for diagnostic and therapeutic applications in cancer. To diminish the risk of generating a human anti-mouse antibody response in patients, chimeric variants were created. The purpose of this study was to recombinantly produce chimeric antibody (chAb) derivatives of the murine mAb 14C5 and to evaluate the in vitro and in vivo characteristics.

Methods

In vitro stability, specificity, and affinity of radioiodinated chAb and fragments (Iodo-Gen method) were examined on high-expressing α_vβ₅ A549 lung tumor cells. In vivo biodistribution and pharmacokinetic characteristics were studied in A549 lung tumor-bearing Swiss Nu/Nu mice.

Results

Saturation binding experiments revealed high in vitro affinity of radioiodinated chAb, F(ab')₂, and Fab, with dissociation constants (K_D) of 1.19 ± 0.19, 0.68 ± 0.10, and 2.11 ± 0.58 nM, respectively. ChAb 14C5 showed highest tumor uptake (approximately 10%ID/g) at 24 h post injection, corresponding with other high-affinity Abs. ChF(ab')₂ and chFab fragments showed faster clearance from the blood compared to the intact Ab.

Conclusions

The chimerization of mAb 14C5 and its fragments has no or negligible effect on the properties of the antibody. In vitro and in vivo properties show that the chAb 14C5 is promising for radioimmunotherapy, due to its high maximum tumor uptake and its long retention in the tumor. The chF(ab')₂ fragment shows a similar receptor affinity and a faster blood clearance, causing less non-specific retention than the chAb. Due to their fast blood clearance, the fragments show high potential for radioimmunodiagnosis.

Guiding plant virus particles to integrin-displaying cells

Viral nanoparticles (VNPs) are structurally regular, highly stable, tunable nanomaterials that can be conveniently produced in high yields. Unmodified VNPs from plants and bacteria generally do not show tissue specificity or high selectivity in binding to or entry into mammalian cells. They are, however, malleable by both genetic and chemical means, making them useful scaffolds for the display of large numbers of cell- and tissue-targeting ligands, imaging moieties, and/or therapeutic agents in a well-defined manner. Capitalizing on this attribute, we modified the genetic sequence of the Cowpea mosaic virus (CPMV) coat protein to display an RGD oligopeptide sequence derived from human adenovirus type 2 (HAdV-2). Concurrently, wild-type CPMV was modified via NHS acylation and Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry to attach an integrin-binding cyclic RGD peptide. Both types of particles showed strong and selective affinity for several different cancer cell lines that express RGD-binding integrin receptors.

Colon cancer molecular subtypes identified by expression profiling and associated to stroma, mucinous type and different clinical behavior

Background

Colon cancer patients with the same stage show diverse clinical behavior due to tumor heterogeneity. We aimed to discover distinct classes of tumors based on microarray expression patterns, to analyze whether the molecular classification correlated with the histopathological stages or other clinical parameters and to study differences in the survival.

Methods

Hierarchical clustering was performed for class discovery in 88 colon tumors (stages I to IV). Pathways analysis and correlations between clinical parameters and our classification were analyzed. Tumor subtypes were validated using an external set of 78 patients. A 167 gene signature associated to the main subtype was generated using the 3-Nearest-Neighbor method. Coincidences with other prognostic predictors were assesed.

Results

Hierarchical clustering identified four robust tumor subtypes with biologically and clinically distinct behavior. Stromal components (p < 0.001), nuclear β-catenin (p = 0.021), mucinous histology (p = 0.001), microsatellite-instability (p = 0.039) and BRAF mutations (p < 0.001) were associated to this classification but it was independent of Dukes stages (p = 0.646). Molecular subtypes were established from stage I. High-stroma-subtype showed increased levels of genes and altered pathways distinctive of tumour-associated-stroma and components of the extracellular matrix in contrast to Low-stroma-subtype. Mucinous-subtype was reflected by the increased expression of trefoil factors and mucins as well as by a higher proportion of MSI and BRAF mutations. Tumor subtypes were validated using an external set of 78 patients. A 167 gene signature associated to the Low-stroma-subtype distinguished low risk patients from high risk patients in the external cohort (Dukes B and C:HR = 8.56(2.53-29.01); Dukes B,C and D:HR = 1.87(1.07-3.25)). Eight different reported survival gene signatures segregated our tumors into two groups the Low-stroma-subtype and the other tumor subtypes.

Conclusions

We have identified novel molecular subtypes in colon cancer with distinct biological and clinical behavior that are established from the initiation of the tumor. Tumor microenvironment is important for the classification and for the malignant power of the tumor. Differential gene sets and biological pathways characterize each tumor subtype reflecting underlying mechanisms of carcinogenesis that may be used for the selection of targeted therapeutic procedures. This classification may contribute to an improvement in the management of the patients with CRC and to a more comprehensive prognosis.

Matched rabbit monoclonal antibodies against αv-series integrins reveal a novel αvβ3-LIBS epitope, and permit routine staining of archival paraffin samples of human tumors

The relationship between integrin expression and function in pathologies is often contentious as comparisons between human pathological expression and expression in cell lines is difficult. In addition, the expression of even integrins αvβ6 and αvβ8 in tumor cell lines is not comprehensively documented. Here, we describe rabbit monoclonal antibodies (RabMabs) against the extracellular domains of αv integrins that react with both native integrins and formalin fixed, paraffin embedded (FFPE) human tissues. These RabMabs, against αvβ3 (EM22703), αvβ5 (EM09902), αvβ6 (EM05201), αvβ8 (EM13309), and pan-αv (EM01309), recognize individual integrin chains in Western blots and in flow cytometry. EM22703 detected a ligand-induced binding site (LIBS), reporting an epitope enhanced by the binding of an RGD-peptide to αvβ3. αvβ8 was rarely expressed in human tumor specimens, and weakly expressed in non-small-cell lung carcinoma (NSCLC). However, ovarian carcinoma cell lines expressed αvβ8, as did some melanoma cells, whereas U87MG glioma lacked αvβ8 expression. We observed an unexpected strong expression of αvβ6 in tumor samples of invasive ductal breast adenoma, colorectal carcinoma (CRC), and NSCLC. αvβ3 was strongly expressed in some invasive NSCLC cohorts. Interestingly, PC3 prostate cell and human prostate tumors did not express αvβ3. The RabMabs stained plasma membranes in FFPE-immunohistochemistry (IHC) samples of tumor cell lines from lung, ovary, colon, prostate, squamous cell carcinoma of head and neck (SCCHN), breast, and pancreas carcinomas. The RabMabs are unique tools for probing αv integrin biology, and suggest that especially αvβ6 and αvβ8 biologies still have much to reveal.

Clearance of apoptotic cells: implications in health and disease

Recent advances in defining the molecular signaling pathways that regulate the phagocytosis of apoptotic cells have improved our understanding of this complex and evolutionarily conserved process. Studies in mice and humans suggest that the prompt removal of dying cells is crucial for immune tolerance and tissue homeostasis. Failed or defective clearance has emerged as an important contributing factor to a range of disease processes. This review addresses how specific molecular alterations of engulfment pathways are linked to pathogenic states. A better understanding of the apoptotic cell clearance process in healthy and diseased states could offer new therapeutic strategies.

Preclinical evaluation of monoclonal antibody 14C5 for targeting pancreatic cancer

The use of radiolabeled antibodies that are able to target primary tumors as well as metastatic tumor sites with minimal reactivity to normal tissues is a promising approach for treating pancreatic cancer. In this study, the integrin alpha(v)beta(5) is studied as a target for the diagnosis of and potential therapy for human pancreatic cancer by using the radiolabeled murine monoclonal antibody (mAb) 14C5. Biopsy specimens from human pancreatic tumors were examined for the expression of the integrin alpha(v)beta(5). The pancreatic tumor cell line Capan-1 was used to test the in vitro targeting potency of mAb 14C5 labeled with 125/131-iodine and 111-indium. Internalization, retention, and metabolism were investigated in cellular radioimmunoassays. Biodistribution and tumor-targeting characteristics were studied in Capan-1 xenografts. All tumor sections were positive for the integrin alpha(v)beta(5), with an extensive positive staining of the stroma. Saturation binding experiments showed high affinity with comparable K(d)s. In vitro internalization experiments showed a longer intracellular retention of (111)In-p-benzyl isothiocyanate-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (p-SCN-Bz-DOTA)-14C5 in comparison to (125)I-14C5 and (111)In-p-isothiocyanatobenzyl diethylenetriaminepentaacetic acid (p-SCN-Bz-DTPA)-14C5. In vivo radioisotope tumor uptake was maximum at 48-72 hours, with the uptake of (111)In-p-SCN-Bz-DOTA-14C5 (35.84 +/- 8.64 percentage of injected dose per g [%ID/g]) being 3.9- and 2.2-folds higher than (131)I-14C5 (12.16 +/- 1.03%ID/g) and (111)In-p-SCN-Bz-DTPA-14C5 (14.30 +/- 3.76%ID/g), respectively. Planar gamma imaging with mAb 14C5 indicated clear localization of the pancreatic tumors versus minimal normal tissue uptake. mAb 14C5 is a promising new antibody for targeting the integrin alpha(v)beta(5) for the diagnosis of and potential therapy for pancreatic cancer.

In vitro evaluation of pan-PI3-kinase inhibitor SF1126 in trastuzumab-sensitive and trastuzumab-resistant HER2-over-expressing breast cancer cells

Purpose

The purpose of the current study is to determine the in vitro cytotoxic effects of the novel pan-PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells.

Methods

Cell proliferation and cytotoxicity were examined by MTS colorimetric assay, FACS analysis, colony formation assay, and immunoblotting. Phosphoinositol-3-kinase signaling was assessed by immunoblotting for phosphorylated Akt. Combination effects of trastuzumab and SF1126 were examined in resistant cells by MTS and soft agar assay.

Results

SF1126 inhibited proliferation, and induced G1 arrest and apoptosis of SKBR3 and BT474 parental and trastuzumab-resistant HER2-over-expressing cells. Colony formation was inhibited by SF1126, caspase 3 and PARP proteins were cleaved, and survivin was down-regulated. Inhibition of PI3-kinase was confirmed by reduced phosphorylation of Akt. Finally, the combination of SF1126 and trastuzumab synergistically inhibited proliferation of resistant cells, with SF1126-treated cells showing reduced anchorage-independent growth.

Conclusions

These results provide evidence that a clinically relevant pan-PI-3 kinase inhibitor can reverse trastuzumab resistance in breast cancer cells, and support further study of PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells, including those that have progressed on trastuzumab.