Extracellular vesicles from oral mucosa stem cells promote lipid raft formation in human microglia through TLR4, P2X4R, and αVβ3/αVβ5 signaling pathways

Targeting of disease-associated microglia represents a promising therapeutic approach that can be used for the prevention or slowing down neurodegeneration. In this regard, the use of extracellular vesicles (EVs) represents a promising therapeutic approach. However, the molecular mechanisms by which EVs regulate microglial responses remain poorly understood. In the present study, we used EVs derived from human oral mucosa stem cells (OMSCs) to investigate the effects on the lipid raft formation and the phagocytic response of human microglial cells. Lipid raft labeling with fluorescent cholera toxin subunit B conjugates revealed that both EVs and lipopolysaccharide (LPS) by more than two times increased lipid raft formation in human microglia. By contrast, combined treatment with LPS and EVs significantly decreased lipid raft formation indicating possible interference of EVs with the process of LPS-induced lipid raft formation. Specific inhibition of Toll-like receptor 4 (TLR4) with anti-TLR4 antibody as well as inhibition of purinergic P2X4 receptor (P2X4R) with selective antagonist 5-BDBD inhibited EVs- and LPS-induced lipid raft formation. Selective blockage of αvβ3/αvβ5 integrins with cilengitide suppressed EV- and LPS-induced lipid raft formation in microglia. Furthermore, inhibition of TLR4 and P2X4R prevented EV-induced phagocytic activity of human microglial cells. We demonstrate that EVs induce lipid raft formation in human microglia through interaction with TLR4, P2X4R, and αVβ3/αVβ5 signaling pathways. Our results provide new insights about the molecular mechanisms regulating EV/microglia interactions and could be used for the development of new therapeutic strategies against neurological disorders.

Inhibition of TGFβ1 activation prevents radiation-induced lung fibrosis

BACKGROUND

Radiotherapy is the main treatment modality for thoracic tumours, but it may induce pulmonary fibrosis. Currently, the pathogenesis of radiation-induced pulmonary fibrosis (RIPF) is unclear, and effective treatments are lacking. Transforming growth factor beta 1 (TGFβ1) plays a central role in RIPF. We found that activated TGFβ1 had better performance for radiation pneumonitis (RP) risk prediction by detecting activated and total TGFβ1 levels in patient serum. αv integrin plays key roles in TGFβ1 activation, but the role of αv integrin-mediated TGFβ1 activation in RIPF is unclear. Here, we investigated the role of αv integrin-mediated TGFβ1 activation in RIPF and the application of the integrin antagonist cilengitide to prevent RIPF.

METHODS

ItgavloxP/loxP ;Pdgfrb-Cre mice were generated by conditionally knocking out Itgav in myofibroblasts, and wild-type mice were treated with cilengitide or placebo. All mice received 16 Gy of radiation or underwent a sham radiation procedure. Lung fibrosis was measured by a modified Ashcroft score and microcomputed tomography (CT). An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum TGFβ1 concentration, and total Smad2/3 and p-Smad2/3 levels were determined via Western blotting.

RESULTS

Conditional Itgav knockout significantly attenuated RIPF (p < .01). Hounsfield units (HUs) in the lungs were reduced in the knockout mice compared with the control mice (p < .001). Conditional Itgav knockout decreased active TGFβ1 secretion and inhibited fibroblast p-Smad2/3 expression. Exogenous active TGFβ1, but not latent TGFβ1, reversed these reductions. Furthermore, cilengitide treatment elicited similar results and prevented RIPF.

CONCLUSIONS

The present study revealed that conditional Itgav knockout and cilengitide treatment both significantly attenuated RIPF in mice by inhibiting αv integrin-mediated TGFβ1 activation.

HIGHLIGHTS

Activated TGFβ1 has a superior capacity in predicting radiation pneumonitis (RP) risk and plays a vital role in the development of radiation-induced pulmonary fibrosis (RIPF). Conditional knock out Itgav in myofibroblasts prevented mice from developing RIPF. Cilengitide alleviated the development of RIPF by inhibiting αv integrin-mediated TGFβ1 activation and may be used in targeted approaches for preventing RIPF.

Simultaneous inhibition of discoidin domain receptor 1 and integrin αVβ3 radiosensitizes human glioblastoma cells

Glioblastomas (GBM) are the most common primary brain tumors in adults and associated with poor clinical outcomes due to therapy resistances and destructive growth. Interactions of cancer cells with the extracellular matrix (ECM) play a pivotal role in therapy resistances and tumor progression. In this study, we investigate the functional dependencies between the discoidin domain receptor 1 (DDR1) and the integrin family of cell adhesion molecules for the radioresponse of human glioblastoma cells. By means of an RNA interference screen on DDR1 and all known integrin subunits, we identified co-targeting of DDR1/integrin β3 to most efficiently reduce clonogenicity, enhance cellular radiosensitivity and diminish repair of DNA double strand breaks (DSB). Simultaneous pharmacological inhibition of DDR1 with DDR1-IN-1 and of integrins αVβ3/αVβ5 with cilengitide resulted in confirmatory data in a panel of 2D grown glioblastoma cultures and 3D gliospheres. Mechanistically, we found that key DNA repair proteins ATM and DNA-PK are altered upon DDR1/integrin αVβ3/integrin αVβ5 inhibition, suggesting a link to DNA repair mechanisms. In sum, the radioresistance of human glioblastoma cells can effectively be declined by co-deactivation of DDR1, integrin αVβ3 and integrin αVβ5.

Very long-term survival of an older glioblastoma patient after treatment with cilengitide: a case report

Glioblastoma (GBM) is the most common malignant brain tumor. Less than 1% of patients survive longer than 10 years. A 77-year-old woman was diagnosed with MGMT-methylated GBM in 2009. The patient received cilengitide as part of the CENTRIC clinical trial in conjunction with standard radiation and chemotherapy. Though the study was halted in 2013, our patient received cilengitide until 2016 with no radiographic evidence of recurrence thus far. This is the oldest reported GBM patient with greater than 10-year survival. Her exceptional response may have been influenced by MGMT promoter methylation status and PTEN expression.

Combination Effect of Cilengitide with Erlotinib on TGF-β1-Induced Epithelial-to-Mesenchymal Transition in Human Non-Small Cell Lung Cancer Cells

The epithelial-to-mesenchymal transition (EMT) is important for morphogenesis during development and is mainly induced by transforming growth factor (TGF)-β. In lung cancer, EMT is characterized by the transformation of cancer cells into a mobile, invasive form that can transit to other organs. Here, using a non–small cell lung cancer (NSCLC) cell line, we evaluated the EMT-related effects of the epidermal growth factor receptor inhibitor erlotinib alone and in combination with cilengitide, a cyclic RGD-based integrin antagonist. Erlotinib showed anti-proliferative and inhibitory effects against the TGF-β1–induced EMT phenotype in NSCLC cells. Compared with erlotinib alone, combination treatment with cilengitide led to an enhanced inhibitory effect on TGF-β1–induced expression of mesenchymal markers and invasion in non–small cell lung cancer A549 cells. These results suggest that cilengitide could improve anticancer drug efficacy and contribute to improved treatment strategies to inhibit and prevent EMT-based cancer progression.

Cilengitide, an αvβ3-integrin inhibitor, enhances the efficacy of anti-programmed cell death-1 therapy in a murine melanoma model

Integrins play an important role in multiple stages of tumor progression and metastasis. Previous studies have shown synergistic effects of combined αvβ6-integrin and αvβ8-integrin inhibitors with immunotherapy. However, the role of αvβ3-integrin inhibitor in tumor immunity is still unclear. In this study, we aimed to elucidate the impact of the αvβ3-integrin inhibitor on PD-L1 expression and sensitivity to immune checkpoint blockade in melanoma. We investigated the effects of cilengitide, an αvβ3-integrin inhibitor, on cell viability and apoptosis of melanoma cell lines. And we explored how cilengitide regulated the expression of PD-L1 in melanoma cells in vitro and in vivo, using immunofluorescence, flow cytometry, Western blotting, and immunohistochemistry. A subcutaneous B16 murine melanoma model was utilized to determine whether combining cilengitide with anti-PD1 therapy inhibited tumor growth and positively regulated tumor microenvironment (TME). Our results showed that cilengitide inhibited cell viability and induced apoptosis in B16 and A375 cell lines. Furthermore, cilengitide decreased PD-L1 expression by reducing STAT3 phosphorylation in two melanoma cell lines. Cilengitide also reduced subcutaneous tumor PD-L1 expression in the B16 murine melanoma model. Accordingly, cilengitide positively regulated antitumor immune responses and provided durable therapy when combined with anti-PD1 monoclonal antibody in the murine melanoma model. This combination therapy reduced tumor growth and extended survival. Our study highlights that cilengitide enhances the efficacy of anti-PD1 therapy and produces a stronger antitumor immune response. This combination therefore represents a novel therapeutic regimen that may improve immunotherapy treratment.

Antagonizing αvβ3 Integrin Improves Ischemia-Mediated Vascular Normalization and Blood Perfusion by Altering Macrophages

Background: αVβ3 integrin has been implicated in the physiological processes and pathophysiology of important angiogenesis-related disorders; however, the preclinical and clinical data on integrin αVβ3 antagonists have not demonstrated improved outcomes. Our goal was to test the hypothesis that inhibition of αVβ3 integrin improves blood flow in a mouse hindlimb ischemia model.

Methods: In this study, we examined the effect of cilengitide, an αVβ3/αVβ5 integrin-specific RGD-mimetic cyclic peptide, on blood perfusion and angiogenesis after hindlimb ischemia. Blood flow was measured using Laser Doppler Scanner. Vascular density, and macrophages infiltration were examined by immunofluorescence. Macrophage polarization was measured by quantitative real time PCR.

Results: We found that low-dose, not high-dose, cilengitide increased blood flow perfusion, capillary formation, and pericyte coverage, accompanied by an accumulation of macrophages and increased expression of the chemokine (C-C motif) ligand 2 (CCL2) in ischemic muscles. Macrophage depletion using clodronate liposomes resulted in a reduction in low-dose cilengitide-induced blood flow perfusion, macrophage accumulation, pericyte coverage, and CCL2 expression. Finally, in vitro assays showed that low-dose, not high-dose, cilengitide increased macrophage migration.

Conclusion: These studies identified a novel role of the inhibition of αVβ3 integrin in modulating ischemia-induced angiogenesis, possibly through effects on macrophage infiltration and polarization, and revealed αVβ3 integrin inhibition to be a promising therapeutic strategy for peripheral artery disease.

Type V Collagen in Scar Tissue Regulates the Size of Scar after Heart Injury

Scar tissue size following myocardial infarction is an independent predictor of cardiovascular outcomes, yet little is known about factors regulating scar size. We demonstrate that collagen V, a minor constituent of heart scars, regulates the size of heart scars after ischemic injury. Depletion of collagen V led to a paradoxical increase in post-infarction scar size with worsening of heart function. A systems genetics approach across 100 in-bred strains of mice demonstrated that collagen V is a critical driver of postinjury heart function. We show that collagen V deficiency alters the mechanical properties of scar tissue, and altered reciprocal feedback between matrix and cells induces expression of mechanosensitive integrins that drive fibroblast activation and increase scar size. Cilengitide, an inhibitor of specific integrins, rescues the phenotype of increased post-injury scarring in collagen-V-deficient mice. These observations demonstrate that collagen V regulates scar size in an integrin-dependent manner.

Integrin αvβ3-Akt signalling plays a role in radioresistance of melanoma

Melanoma is a deadly type of skin cancer that is particularly difficult to treat owing to its resistance to radiation therapy. Here, we attempted to determine the key proteins responsible for melanoma radioresistance, with the aim of improving disease response to radiation therapy. Two melanoma cell lines, SK-Mel5 and SK-Mel28, with different radiosensitivities were analysed via RNA-Seq (Quant-Seq) and target proteins with higher abundance in the more radioresistant cell line, SK-Mel28, identified. Among these proteins, integrin αvβ3, a well-known molecule in cell adhesion, was selected for analysis. Treatment of SK-Mel28 cells with cilengitide, an integrin αvβ3 inhibitor, as well as γ-irradiation resulted in more significant cell death than γ-irradiation alone. In addition, Akt, a downstream signal transducer of integrin αvβ3, showed high basic activation in SK-Mel28 and was significantly decreased upon co-treatment with cilengitide and γ-irradiation. MK-2206, an Akt inhibitor, exerted similar effects on the SK-Mel28 cell line following γ-irradiation. Our results collectively demonstrate that the integrin αvβ3-Akt signalling pathway contributes to radioresistance in SK-Mel28 cells, which may be manipulated to improve therapeutic options for melanoma.

Protective effects of cilengitide on inflammation in chondrocytes under excessive mechanical stress

Chondrocytes constantly receive external stimuli, which regulates remodeling. An optimal level of mechanical stress is essential for maintaining chondrocyte homeostasis, however, excessive mechanical stress induces inflammatory cytokines and protease, such as matrix metalloproteinases (MMPs). Therefore, excessive mechanical stress is considered to be one of the main causes to cartilage destruction leading to osteoarthritis (OA). Integrins are well-known as cell adhesion molecules and act as receptors for extracellular matrix (ECM), and are believed to control intracellular signaling pathways both physically and chemically as a mechanoreceptor. However, few studies have focused on the roles and functions of integrins in inflammation caused by excessive mechanical stress. In this study, we examined the relationship between integrins (αVβ3 and αVβ5) and the expression of inflammatory factors under mechanical loading in chondrocytes by using an integrin receptor antagonist (cilengitide). Cilengitide suppressed the gene expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), matrix metalloproteinase-3 (MMP-3), and MMP-13 induced by excessive mechanical stress. In addition, the protein expression of IL1-β and MMP-13 was also inhibited by the addition of cilengitide. Next, we investigated the involvement of intracellular signaling pathways in stress-induced integrin signaling in chondrocytes by using western blotting. The levels of p-FAK, p-ERK, p-JNK, and p-p38 were enhanced by excessive mechanical stress and the enhancement was suppressed by treatment with cilengitide. In conclusion, this study revealed that excessive mechanical stress may activate integrins αVβ3 and αVβ5 on the surface of chondrocytes and thereby induce an inflammatory reaction by upregulating the expression of IL-1β, TNF-α, MMP-3, and MMP-13 through phosphorylation of FAK and MAPKs.

ITGAV targeting as a therapeutic approach for treatment of metastatic breast cancer

During tumorigenesis and metastasis, integrins regulate localization and activity of proteolytic enzymes that remodel the extracellular matrix. Previous studies have demonstrated blocking of α_Vβ₃ to effectively inhibit proliferation, angiogenesis, and the survival of various cancer cell types. However, little is known about the functional role of the integrin subunit alpha-V gene (ITGAV) in metastatic breast cancer. In this study, ITGAV knockdown was used to identify the molecular mechanism by which ITGAV promotes tumorigenesis, metastasis, proliferation, invasion, and cellular self-renewal. The effectiveness of an ITGAV antagonist, cilengitide, for breast cancer treatment was investigated in vivo. Analysis of publicly available data demonstrated that overexpression of ITGAV was associated with poor relapse free survival of breast cancer patients. Silencing of ITGAV inhibited cell proliferation, invasion, and self-renewal of breast cancer cell lines by altering expression of BCL2 and PXN. The use of cilengitide significantly reduced lung metastasis in a metastatic breast cancer animal model. In conclusion, overexpression of ITGAV contributes to breast cancer metastasis through upregulation of PXN. Targeting ITGAV is a potential treatment for metastatic breast cancer as well as primary breast tumors with high ITGAV expression. ITGAV expression levels may be useful predictors of patient treatment and outcome responses.

Repurposing an anti-cancer agent for the treatment of hypertrophic heart disease

Coronary microvascular dysfunction combined with maladaptive cardiomyocyte morphology and energetics is a major contributor to heart failure advancement. Thus, dually enhancing cardiac angiogenesis and targeting cardiomyocyte function to slow, or reverse, the development of heart failure is a logical step towards improved therapy. We present evidence for the potential to repurpose a former anti-cancer Arg-Gly-Asp (RGD)-mimetic pentapeptide, cilengitide, here used at low doses. Cilengitide targets αvβ3 integrin and this protein is upregulated in human dilated and ischaemic cardiomyopathies. Treatment of mice after abdominal aortic constriction (AAC) surgery with low-dose cilengitide (ldCil) enhances coronary angiogenesis and directly affects cardiomyocyte hypertrophy with an associated reduction in disease severity. At a molecular level, ldCil treatment has a direct effect on cardiac endothelial cell transcriptomic profiles, with a significant enhancement of pro-angiogenic signalling pathways, corroborating the enhanced angiogenic phenotype after ldCil treatment. Moreover, ldCil treatment of Angiotensin II-stimulated AngII-stimulated cardiomyocytes significantly restores transcriptomic profiles similar to those found in normal human heart. The significance of this finding is enhanced by transcriptional similarities between AngII-treated cardiomyocytes and failing human hearts. Taken together, our data provide evidence supporting a possible new strategy for improved heart failure treatment using low-dose RGD-mimetics with relevance to human disease. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Exploring the role of defective fibronectin matrix assembly in the VHL-associated CNS hemangioblastoma

Background:

Central nervous system (CNS) hemangioblastoma (HB) is the most common tumor in the von Hippel Lindau (VHL) disorder, the hereditary tumor syndrome caused by the biallelic mutations of theVHLgene. The disrupted VHL and Elongin protein interaction on hypoxia-inducible factor-1α (HIF-1α) induces a set of hypoxia-inducible genes, resulting in an unchecked endothelial cell proliferation that then leads to hemangioblastoma formation. However, recent studies have shown that disruptive germline mutations ofVHLneed not result in hemangioblastoma, though it can cause other manifestations of the VHL syndrome. Similarly, sporadic hemangioblastoma can occur rarely without a somatic biallelicVHLmutation. The VHL protein was earlier found to be associated with the deposition of matrix fibronectin (FN) protein in the renal extracellular matrix.

Methods:

The present study was designed to investigate the deposition of the matrix FN protein in VHL-associated hemangioblastoma.

Results:

Seven HB tumor samples from the VHL syndrome had lower expressions of tissue FN compared to the control cerebellum samples or the control blood vessel sample. On comparing the VHL and FN protein expressions in a timed endothelial tube assay, the VHL protein expression was absent during the initial phase of tube formation but started expressing after 6 h. The levels of matrix form of FN gradually increased along with the VHL expression during the maturation of tube formation. Tube formation was found to be enhanced with extraneously added soluble FN and inhibited by matrix FN. Similarly, tube formation was inhibited by a modified tripeptide (RGD) inhibitor of integrin (-αVβ3), namely, Cyclo-Ala-Arg-Gly-Asp-3-aminomethylbenzoyl.

Conclusions:

Our study implicates that the extracellular deposition and matrix formation of FN is important for vascular endothelial proliferation, and that its absence has roles in the development of hemangioblastoma in the VHL syndrome.

The Evolving Role of the Oncologic Neurosurgeon: Looking Beyond Extent of Resection in the Modern Era

Neurosurgeons have played an essential role in glioma management and research for over a century. While the past twenty years have played witness to many exciting developments in glioma biology, diagnosis, and classification, relatively few novel, effective treatment strategies have been introduced. The role of neurosurgery in glioma management has been clarified, with a large body of evidence in support of maximal safe resection. However, neurosurgeons have also played a critical role in translational research during this period. The development of new MRI technologies has benefited greatly from validation with stereotactically-targeted human tissue. Careful banking of surgically acquired tissue was key to the development of a new classification scheme for glioma. Similarly, we have garnered a considerably deeper understanding of molecular and genetic properties of glioma through analysis of large surgical specimens. As our classification schemes become more sophisticated, incorporating targeted tissue sampling into the development of novel treatment strategies becomes essential. Such ex vivo analysis could be instrumental in determining mechanisms of treatment failure or success. Modern tumor neurosurgeons should consider themselves surgical neuro-oncologists, with engagement in translational research essential to furthering the field and improving outlooks for our patients.

Fibronectin Promotes the Malignancy of Glioma Stem-Like Cells Via Modulation of Cell Adhesion, Differentiation, Proliferation and Chemoresistance

Glioma stem-like cells (GSCs) are regarded as the sources of oncogenesis, recurrence, invasion and chemoresistance in malignant gliomas. Growing evidence suggests that the microenvironment surrounding GSCs interacts with tumor cells to influence biological behavior; however, the functional mechanisms involved are still unclear. In the present study, we investigated the modulation of GSCs triggered by fibronectin (FN), a main component of the extracellular matrix (ECM), in terms of cell adhesion, differentiation, proliferation and chemoresistance. We demonstrated that pre-coated FN prompted increased adherence by GSCs, with increased matrix metallopeptidases (MMPs)-2 and -9 expression, in a concentration-dependent manner. Decreases in sox-2 and nestin levels, and increased levels of glial fibrillary acidic protein (GFAP) and β-tubulin were also found in GSCs, indicating cell differentiation driven by FN. Further investigation revealed that FN promoted cell growth, as demonstrated by the elevation of Ki-67, with the activation of p-ERK1/2 and cyclin D1 also evident. In addition, FN suppressed p53-mediated apoptosis and upregulated P-glycoprotein expression, making GSCs more chemoresistant to alkylating agents such as carmustine. In contrast, this effect was reversed by an integrin inhibitor, cilengitide. Activation of the focal adhesion kinase/paxillin/AKT signaling pathway was involved in the modulation of GSCs by FN. Focusing on the interactions between tumor cells and the ECM may be an encouraging aspect of research on novel chemotherapeutic therapies in future.

Targeting αvβ3 and αvβ5 integrins inhibits pulmonary metastasis in an intratibial xenograft osteosarcoma mouse model

Osteosarcoma is an aggressive bone cancer that has a high propensity for metastasis to the lungs. Patients with metastatic disease face a very poor prognosis. Therefore, novel therapeutics, efficiently suppressing the metastatic process, are urgently needed. Integrins play a pivotal role in tumor cell adhesion, motility and metastasis. Here, we evaluated αvβ3 and αvβ5 integrin inhibition with cilengitide as a novel metastasis-suppressive therapeutic approach in osteosarcoma. Immunohistochemical analysis of αvβ3 and αvβ5 integrins expression in a tissue microarray of tumor specimens collected from osteosarcoma patients revealed that αvβ5 integrin is mainly found on tumor cells, whereas αvβ3 is predominantly expressed by stromal cells. In vitro functional assays demonstrated that cilengitide dose-dependently inhibited de novo adhesion, provoked detachment and inhibited migration of osteosarcoma cell lines. Cilengitide induced a decline in cell viability, blocked the cell cycle in the G1 phase and caused anoikis by activation of the Hippo pathway. In a xenograft orthotopic mouse model cilengitide minimally affected intratibial primary tumor growth but, importantly, suppressed pulmonary metastasis. The data demonstrate that targeting αvβ3 and αvβ5 integrins in osteosarcoma should be considered as a novel therapeutic option for patients with metastatic disease.

CD44 drives aggressiveness and chemoresistance of a metastatic human osteosarcoma xenograft model

Background

Osteosarcoma is the most common primary malignant bone tumor with a 5 year survival rate of up to 70%. However, patients with metastatic disease have still a very poor prognosis. Osteosarcoma metastasis models are essential to develop novel treatment strategies for advanced disease.

Methods

Based on a serial transplantation approach, we have established a U-2 OS osteosarcoma xenograft model with increased metastatic potential and compared it to other metastatic osteosarcoma models from international sources. Subclones with differing invasive potential were compared for genomic gains and losses as well as gene expression changes by several bioinformatic approaches. Based on the acquired results, the effects of a shRNA-mediated CD44 mRNA knockdown on migration, invasion and chemosensitivity were evaluated.

Results

The CD44 gene was part of an amplified region at chromosome 11p found in both U-2 OS subclones with enhanced metastatic potential but not in parental U-2 OS cells, corresponding with distinct CD44 overexpression. Accordingly, shRNA-mediated CD44 knockdown significantly attenuated osteosarcoma cell migration, invasion, and viability especially in the metastatic subclones of U-2 OS and Saos-2 cells. Metastatic subclones generally were hypersensitive against the integrin inhibitor cilengitide paralleled by alterations in integrin expression pattern following CD44 knock-down. Additionally, attenuation of CD44 expression sensitized these cell models against osteosarcoma chemotherapy with doxorubicin but not methotrexate and cisplatin.

Conclusions

The osteosarcoma xenograft models with increased metastatic potential developed in this study can be useful for identification of mechanisms driving metastasis and resistance towards clinically used and novel therapeutic regimens.

Integrin Beta 3 Regulates Cellular Senescence by Activating the TGF-β Pathway

Cellular senescence is an important in vivo mechanism that prevents the propagation of damaged cells. However, the precise mechanisms regulating senescence are not well characterized. Here, we find that ITGB3 (integrin beta 3 or β3) is regulated by the Polycomb protein CBX7. β3 expression accelerates the onset of senescence in human primary fibroblasts by activating the transforming growth factor β (TGF-β) pathway in a cell-autonomous and non-cell-autonomous manner. β3 levels are dynamically increased during oncogene-induced senescence (OIS) through CBX7 Polycomb regulation, and downregulation of β3 levels overrides OIS and therapy-induced senescence (TIS), independently of its ligand-binding activity. Moreover, cilengitide, an αvβ3 antagonist, has the ability to block the senescence-associated secretory phenotype (SASP) without affecting proliferation. Finally, we show an increase in β3 levels in a subset of tissues during aging. Altogether, our data show that integrin β3 subunit is a marker and regulator of senescence.

Reduced Cytokine Release in Ex Vivo Response to Cilengitide and Cetuximab Is a Marker for Improved Survival of Head and Neck Cancer Patients

Targeting of α_Vβ3 and α_Vβ5 integrins by cilengitide may reduce growth of solid tumors including head and neck squamous cell carcinoma (HNSCC). Preclinical investigations suggest increased activity of cilengitide in combination with other treatment modalities. The only published trial in HNSCC (ADVANTAGE) investigated cisplatin, 5-fluorouracil, and cetuximab (PFE) without or with once (PFE+CIL1W) or twice weekly cilengitide (PFE+CIL2W) in recurrent/metastatic HNSCC. ADVANTAGE showed good tolerability of the cilengitide arms and even lower adverse events (AEs) compared to PFE but not the benefit in overall survival expected based on preclinical data. As we found in the FLAVINO assay, a short-time ex vivo assay for prediction of chemosensitivity, only a subgroup of HNSCC had an increased suppressive effect of cilengitide containing combination therapies on colony formation of epithelial cells (CF_ec) and release of pro-angiogenetic and pro-inflammatory cytokines, whereas other HNSCC failed to respond. Response to α_Vβ3 and α_Vβ5 integrin targeting by cilengitide classifies HNSCC regarding outcome. We present FLAVINO data arguing for further development of cilengitide plus cetuximab in treatment of a subgroup of HNSCC potentially identified by the FLAVINO assay using a set of biomarkers for response evaluation.

Cilengitide and Cetuximab Reduce Cytokine Production and Colony Formation of Head and Neck Squamous Cell Carcinoma Cells Ex Vivo

BACKGROUND/AIM

To analyze ex vivo effects of combined targeting of the epidermal growth factor-receptor (EGFR) by cetuximab (E) plus αVβ3 and αVβ5 integrins by cilengitide (Cil) on colony formation of epithelial cells (CF_ec) and release of pro-angiogenetic and pro-inflammatory cytokines in head and neck squamous cell carcinoma (HNSCC) cells.

MATERIALS AND METHODS

Collagenase-IV digests of 43 histopathological confirmed HNSCC cases were seeded into laminin-coated 96-well plates containing E, Cil, or Cil+E in final concentrations of 66.7 μg/ml, 10 μM, and 10 μM+66.7 μg/ml, respectively. Following the FLAVINO-assay protocol, supernatants were harvested after 3 days and adherent cells fixed in ethanol. Counting of CF_ec was facilitated by FITC-labeled pan-cytokeratin antibodies. Out of 43 HNSCC cases, 39 had adherent growth (mean CF_ec≥4/well in triplicate controls). Cytokines in supernatants were measured using ELISA were interleukin 6 (IL-6), monocyte chemoattractant protein 1 (MCP-1) and vascular endothelial growth factor A (VEGFA).

RESULTS

CF_ec on laminin was significantly reduced by Cil, E, and Cil+E. Cytokine measurements also revealed significant suppression of MCP-1, IL-6 and VEGFA. The strongest suppression of CF_ec, MCP-1 and VEGFA release was exerted by Cil and E combined. Efficacy of Cil+E exceeded those of the solely applied pharmaceutics but failed regarding significant synergism of both treatments as E was unable to significantly boost the effects of Cil. In contrast, IL-6 release was significantly suppressed by E but not by Cil, while their combination strongly reduced it.

CONCLUSION

Combined targeting of EGFR and integrins with E and Cil heightens their suppressive effects regarding CF_ec as well as release of pro-angiogenetic and pro-inflammatory cytokines.

In vitro and in vivo drug disposition of cilengitide in animals and human

Cilengitide is very low permeable (1.0 nm/sec) stable cyclic pentapeptide containing an Arg-Gly-Asp motif responsible for selective binding to αvβ3 and αvβ5 integrins administered intravenously (i.v.). In vivo studies in the mouse and Cynomolgus monkeys showed the major component in plasma was unchanged drug (>85%). These results, together with the absence of metabolism in vitro and in animals, indicate minimal metabolism in both species. The excretion of [(14)C]-cilengitide showed profound species differences, with a high renal excretion of the parent drug observed in Cynomolgus monkey (50% dose), but not in mouse (7 and 28%: m/f). Consistently fecal (biliary) secretion was high in mouse (87 and 66% dose: m/f) but low in Cynomolgus monkey (36.5%). Human volunteers administrated with [(14)C]-cilengitide showed that most of the dose was recovered in urine as unchanged drug (77.5%, referred to Becker et al. 2015), indicating that the Cynomolgus monkey was the closer species to human. In order to better understand the species difference between human and mouse, the hepatobiliary disposition of [(14)C]-cilengitide was determined in sandwich-cultured hepatocytes. Cilengitide exhibited modest biliary efflux (30-40%) in mouse, while in human hepatocytes this was negligible. Furthermore, it was confirmed that the uptake of cilengitide into human hepatocytes was minor and appeared to be passive. In summary, the extent of renal and biliary secretion of cilengitide appears to be highly species specific and is qualitatively well explained using sandwich hepatocyte culture models.

The effect of antagonizing RGD-binding integrin activity in papillary thyroid cancer cell lines

Patients with papillary thyroid cancer (PTC) generally have good prognosis, but inoperable and radioactive iodine–refractory PTC still poses significant clinical challenges due to lack of effective treatment and higher mortality rates. Given the important role of integrins in multiple steps of tumor development, integrin-targeting therapy could be an effective strategy for PTC therapy. In this study, we investigated the antitumor effect of antagonizing Arg-Gly-Asp (RGD)-binding integrin activity in several PTC cell lines. Two RGD-binding integrin heterodimers αvβ3 and αvβ5 were first determined with fluorescence-activated cell sorting (FACS) and immunofluorescence assay. Cell proliferation and apoptosis were examined by Cell Counting Kit-8 assay and FACS, respectively. Cell migration and invasion were determined by transwell assays. All three PTC cell lines examined (BCPAP, K1, and TPC1) showed a moderate-to-high expression of αvβ3 and αvβ5 (P<0.05). Antagonizing the two heterodimers with the RGD-containing antagonist showed moderate inhibitory effect on cell viability of K1 and BCPAP cells, while the inhibitory effect was more significant in TPC1 cells. Similarly, the apoptotic effect induced by antagonizing αvβ3 and αvβ5 was much stronger in TPC1 cells than in BCPAP and K1 cells. Cell migration and invasion were significantly inhibited by αvβ3 and αvβ5 antagonism in all three PTC cell lines. Our results suggested that the demonstrated expression of RGD-binding integrin on PTC cells provides the possibility of integrin-targeting treatment in PTC. The strong apoptotic effect observed in TPC1 cells indicated that a subgroup of PTC patients may benefit from the cytotoxic effect of RGD-binding integrin antagonism, while the strong inhibitory effect on migration and invasion in all three PTC cells by antagonizing αvβ3 and αvβ5 showed there is an exciting possibility that targeting RGD-binding integrin may serve a potential therapeutic approach for metastatic PTC patients.

Small Cause, Great Impact: Modification of the Guanidine Group in the RGD Motif Controls Integrin Subtype Selectivity

Due to its unique role as a hydrogen-bond donor and its positive charge, the guanidine group is an important pharmacophoric group and often used in synthetic ligands. The chemical modification of the guanidine group is often considered to destroy its function. Herein, we show that the N-methylation, N-alkylation, or N-acylation of the guanidine group can be used to modify the receptor subtype specificity of the integrin ligand cilengitide. Using the αvβ6/α5β1-biselective ligand c(isoDGRkphg) and the αvβ6-specific ligand c(FRGDLAFp(NMe)K(Ac) as examples, we show that the binding affinities of the ligands can be fine-tuned by this method to enhance the selectivity for αvβ6. Furthermore, we describe a new strategy for the functionalization of integrin ligands. By introducing longer N-alkylguanidine and N-acylguanidine groups, we are able to simultaneously identify a hitherto unknown anchoring point and enhance the subtype selectivity of the ligand.

Current status and future directions of anti-angiogenic therapy for gliomas

Molecular targets for the pathological vasculature are the vascular endothelial growth factor (VEGF)/VEGF receptor axis, integrins, angiopoietins, and platelet-derived growth factor receptor (PDGFR), as well as several intracellular or downstream effectors like protein kinase C beta and mammalian target of rapamycin (mTOR). Besides hypoxic damage or tumor cell starvation, preclinical models imply vessel independent tumor regression and suggest differential effects of anti-angiogenic treatments on tumorous and nontumorous precursor cells or the immune system. Despite compelling preclinical data and positive data in other cancers, the outcomes of clinical trials with anti-angiogenic agents in gliomas by and large have been disappointing and include VEGF blockage with bevacizumab, integrin inhibition with cilengitide, VEGF receptor inhibition with sunitinib or cediranib, PDGFR inhibition with imatinib or dasatinib, protein kinase C inhibition with enzastaurin, and mTOR inhibition with sirolimus, everolimus, or temsirolimus. Importantly, there is a lack of real understanding for this negative data. Anti-angiogenic therapies have stimulated the development of standardized imaging assessment and the integration of functional MRI sequences into daily practice. Here, we delineate directions in the identification of molecularly or image-based defined subgroups, anti-angiogenic cotreatment for immunotherapy, and the potential of ongoing trials or modified targets to change the game.

Cilengitide combined with cetuximab and platinum-based chemotherapy as first-line treatment in advanced non-small-cell lung cancer (NSCLC) patients: results of an open-label, randomized, controlled phase II study (CERTO)

BACKGROUND

This multicentre, open-label, randomized, controlled phase II study evaluated cilengitide in combination with cetuximab and platinum-based chemotherapy, compared with cetuximab and chemotherapy alone, as first-line treatment of patients with advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients were randomized 1:1:1 to receive cetuximab plus platinum-based chemotherapy alone (control), or combined with cilengitide 2000 mg 1×/week i.v. (CIL-once) or 2×/week i.v. (CIL-twice). A protocol amendment limited enrolment to patients with epidermal growth factor receptor (EGFR) histoscore ≥200 and closed the CIL-twice arm for practical feasibility issues. Primary end point was progression-free survival (PFS; independent read); secondary end points included overall survival (OS), safety, and biomarker analyses. A comparison between the CIL-once and control arms is reported, both for the total cohorts, as well as for patients with EGFR histoscore ≥200.

RESULTS

There were 85 patients in the CIL-once group and 84 in the control group. The PFS (independent read) was 6.2 versus 5.0 months for CIL-once versus control [hazard ratio (HR) 0.72; P = 0.085]; for patients with EGFR histoscore ≥200, PFS was 6.8 versus 5.6 months, respectively (HR 0.57; P = 0.0446). Median OS was 13.6 for CIL-once versus 9.7 months for control (HR 0.81; P = 0.265). In patients with EGFR ≥200, OS was 13.2 versus 11.8 months, respectively (HR 0.95; P = 0.855). No major differences in adverse events between CIL-once and control were reported; nausea (59% versus 56%, respectively) and neutropenia (54% versus 46%, respectively) were the most frequent. There was no increased incidence of thromboembolic events or haemorrhage in cilengitide-treated patients. αvβ3 and αvβ5 expression was neither a predictive nor a prognostic indicator.

CONCLUSIONS

The addition of cilengitide to cetuximab/chemotherapy indicated potential clinical activity, with a trend for PFS difference in the independent-read analysis. However, the observed inconsistencies across end points suggest additional investigations are required to substantiate a potential role of other integrin inhibitors in NSCLC treatment.

CLINICAL TRIAL REGISTRATION ID NUMBER

NCT00842712.

Metabolism and disposition of the αv-integrin ß3/ß5 receptor antagonist cilengitide, a cyclic polypeptide, in humans

Cilengitide (EMD 121974, manufactured by Merck KGaA, Darmstadt, Germany) is an αv-integrin receptor antagonist showing high affinity for αvβ3 and αvβ5.This study determined the mass balance of cilengitide in healthy volunteers receiving a single intravenous infusion of 2.1 MBq (14) C-cilengitide spiked into 250 mL of 2000 mg of cilengitide. Blood, urine, and feces were collected up to day 15 or until excretion of radioactivity was below 1% of the administered dose. Total radioactivity derived from the administration of (14) C-cilengitide and unlabeled cilengitide levels were determined and used for calculation of pharmacokinetic parameters.(14) C-cilengitide-related radioactivity was completely recovered (94.5%; 87.4%-100.6%) and was mainly excreted into urine (mean, 79.0%; range, 70.3%-88.2%) and to a lesser extent into feces (mean, 15.5%; range, 9.3%-20.3%). Of the administered dose, 77.5% was recovered as unchanged cilengitide in urine. The concentration profiles of cilengitide and total radioactivity in plasma were comparable. No circulating metabolites were identified in plasma and urine. Two metabolites,M606-1 and M606-2, were identified in feces considered to be formed by intestinal peptidases or by peptidases from fecal bacteria. In conclusion, the data show that following intravenous administration, (14) C-cilengitide was completely recovered, was excreted mainly via renal elimination, and was not metabolized systemically.

Two cilengitide regimens in combination with standard treatment for patients with newly diagnosed glioblastoma and unmethylated MGMT gene promoter: results of the open-label, controlled, randomized phase II CORE study

BACKGROUND

Survival outcomes for patients with glioblastoma remain poor, particularly for patients with unmethylated O(6)-methylguanine-DNA methyltransferase (MGMT) gene promoter. This phase II, randomized, open-label, multicenter trial investigated the efficacy and safety of 2 dose regimens of the selective integrin inhibitor cilengitide combined with standard chemoradiotherapy in patients with newly diagnosed glioblastoma and an unmethylated MGMT promoter.

METHODS

Overall, 265 patients were randomized (1:1:1) to standard cilengitide (2000 mg 2×/wk; n = 88), intensive cilengitide (2000 mg 5×/wk during wk 1-6, thereafter 2×/wk; n = 88), or a control arm (chemoradiotherapy alone; n = 89). Cilengitide was administered intravenously in combination with daily temozolomide (TMZ) and concomitant radiotherapy (RT; wk 1-6), followed by TMZ maintenance therapy (TMZ/RT→TMZ). The primary endpoint was overall survival; secondary endpoints included progression-free survival, pharmacokinetics, and safety and tolerability.

RESULTS

Median overall survival was 16.3 months in the standard cilengitide arm (hazard ratio [HR], 0.686; 95% CI: 0.484, 0.972; P = .032) and 14.5 months in the intensive cilengitide arm (HR, 0.858; 95% CI: 0.612, 1.204; P = .3771) versus 13.4 months in the control arm. Median progression-free survival assessed per independent review committee was 5.6 months (HR, 0.822; 95% CI: 0.595, 1.134) and 5.9 months (HR, 0.794; 95% CI: 0.575, 1.096) in the standard and intensive cilengitide arms, respectively, versus 4.1 months in the control arm. Cilengitide was well tolerated.

CONCLUSIONS

Standard and intensive cilengitide dose regimens were well tolerated in combination with TMZ/RT→TMZ. Inconsistent overall survival and progression-free survival outcomes and a limited sample size did not allow firm conclusions regarding clinical efficacy in this exploratory phase II study.

Cilengitide downmodulates invasiveness and vasculogenic mimicry of neuropilin 1 expressing melanoma cells through the inhibition of αvβ5 integrin

During melanoma progression, tumour cells show increased adhesiveness to the vascular wall, invade the extracellular matrix (ECM) and frequently form functional channels similar to vascular vessels (vasculogenic mimicry). These properties are mainly mediated by the interaction of integrins with ECM components. Since we had previously identified neuropilin 1 (NRP-1), a coreceptor of vascular endothelial growth factor A (VEGF-A), as an important determinant of melanoma aggressiveness, aims of this study were to identify the specific integrins involved in the highly invasive phenotype of NRP-1 expressing cells and to investigate their role as targets to counteract melanoma progression. Melanoma aggressiveness was evaluated in vitro as cell ability to migrate through an ECM layer and to form tubule-like structures using transfected cells. Integrins relevant to these processes were identified using specific blocking antibodies. The αvβ5 integrin was found to be responsible for about 80% of the capability of NRP-1 expressing cells to adhere on vitronectin. In these cells αvβ5 expression level was twice higher than in low-invasive control cells and contributed to the ability of melanoma cells to form tubule-like structures on matrigel. Cilengitide, a potent inhibitor of αν integrins activation, reduced ECM invasion, vasculogenic mimicry and secretion of VEGF-A and metalloproteinase 9 by melanoma cells. In conclusion, we demonstrated that ανβ5 integrin is involved in the highly aggressive phenotype of melanoma cells expressing NRP-1. Moreover, we identified a novel mechanism that contributes to the antimelanoma activity of the αv integrin inhibitor cilengitide based on the inhibition of vasculogenic mimicry.

Discontinued in 2013: oncology drugs

Introduction: Attrition in clinical development is widely recognised as a key factor negatively impacting overall R&D efficiency. Gaining an understanding of the reasons for candidate failure may lead to improvements in success rates and return on R&D investment. Areas covered: This report provides an analysis of reasons for discontinuation of development of 40 drugs dropped from the global oncology pipeline in 2013 - the largest number of terminations reported since this annual analysis began in 2005. The article also provides discussion on the observations in the context of contemporary views of anticancer drug development. Expert opinion: Twelve drugs (30% of the 2013 discontinuations) failed in Phase III development. None of the pivotal trials investigating these agents incorporated molecular biomarkers for patient stratification. The largest number of drug terminations (20 out of 40) occurred in Phase I development with reasons for termination commonly reported as strategic or undisclosed. Raising the bar in terms of requirements for progression from preclinical development, including the identification of robust pharmacodynamic biomarkers and biomarkers potentially predictive of clinical benefit may lead to an increase in success rates in clinical development and of overall R&D efficiency.

Differential growth inhibition of cerebral metastases by anti-angiogenic compounds

BACKGROUND

The formation of brain metastases is intrinsically linked to concomitant angiogenesis. The purpose of the present study was to investigate the combined effects of interleukin-12 (IL-12) and EMD121974 on the growth and distribution of melanoma brain metastases since both substances may interact with important steps in the cascade of brain metastases formation.

MATERIALS AND METHODS

Brain metastases were induced by either stereotactic implantation of cells to the brain parenchyma or by injection of the melanoma cells into the internal carotid artery to mimic hematogenous metastatic spread in mice. Naive or IL-12-overexpressing murine K1735 melanoma cells were used either alone or in combination with intraperitoneal anti-integrin treatment using EMD121974.

RESULTS

Solid melanoma metastases were more susceptible to daily low-dose treatment of EMD121974 than multiple hematogenous metastases. Interleukin-12 had a profound effect on both types of brain metastases. After 21 days, a marked reduction of vascularity was observed in both tumor types.

CONCLUSION

The combination of endogenous IL-12 production with integrin blockade resulted in additive effects for murine hematogenous brain metastases but not for focal brain metastases.

Population pharmacokinetics of cilengitide in adult and pediatric cancer patients from a nonlinear mixed-effects analysis

Cilengitide is an αvβ3/αvβ5-integrin inhibitor investigated as an anticancer agent. This study aimed to develop a cilengitide population pharmacokinetic model using nonlinear mixed-effects modeling of 136 adult patients with advanced solid tumors and to scale the pharmacokinetic parameters to the pediatric population. A stepwise approach was used, beginning with exploratory analyses checking database/target covariate relationships. A two-compartment structural model was developed to describe cilengitide's concentration-time profile and assess covariates' impact on pharmacokinetic parameters. A bootstrap procedure validated the base/final model stability. A two-compartment model best described concentration-time data. Estimated structural model parameters were: 2.79 L h(-) (1)  m(-) (2) central compartment mean systemic clearance, 6.75 L m(-) (2) central compartment volume of distribution, 1.3 L h(-) (1)  m(-) (2) intercompartmental clearance, and 3.85 L m(-) (2) peripheral compartment volume of distribution. Mean half-life was 0.9 and 3.8 h (α/β-phase). Co-medications and study populations had no impact, as the different studies were not significant model covariates. Weight and body surface area correlated with the pharmacokinetic parameters (r = 0.95, P < 0.01). Pharmacokinetic parameters were consistent with individual study-derived parameters; their allometric scaling enabled pediatric pharmacokinetic profile predictions as corroborated by independent data. This model provides the basis for pharmacokinetic profile simulations of different dosages/regimens in different populations.

Cisplatin, 5-fluorouracil, and cetuximab (PFE) with or without cilengitide in recurrent/metastatic squamous cell carcinoma of the head and neck: results of the randomized phase I/II ADVANTAGE trial (phase II part)

BACKGROUND

Recurrent and/or metastatic squamous cell carcinoma of the head and neck (R/M-SCCHN) overexpresses αvβ5 integrin. Cilengitide selectively inhibits αvβ3 and αvβ5 integrins and is investigated as a treatment strategy.

PATIENTS AND METHODS

The phase I/II study ADVANTAGE evaluated cilengitide combined with cisplatin, 5-fluorouracil, and cetuximab (PFE) in R/M-SCCHN. The phase II part reported here was an open-label, randomized, controlled trial investigating progression-free survival (PFS). Patients received up to six cycles of PFE alone or combined with cilengitide 2000 mg once (CIL1W) or twice (CIL2W) weekly. Thereafter, patients received maintenance therapy (cilengitide arms: cilengitide plus cetuximab; PFE-alone arm: cetuximab only) until disease progression or unacceptable toxicity.

RESULTS

One hundred and eighty-two patients were treated. Median PFS per investigator read was similar for CIL1W + PFE, CIL2W + PFE, and PFE alone (6.4, 5.6, and 5.7 months, respectively). Accordingly, median overall survival and objective response rates were not improved with cilengitide (12.4 months/47%, 10.6 months/27%, and 11.6 months/36%, respectively). No clinically meaningful safety differences were observed between groups. None of the tested biomarkers (expression of integrins, CD31, Ki-67, vascular endothelial growth factor receptor 2, vascular endothelial-cadherin, type IV collagen, epidermal growth factor receptor, or p16 for human papillomavirus) were predictive of outcome.

CONCLUSION

Neither of the cilengitide-containing regimens demonstrated a PFS benefit over PFE alone in R/M-SCCHN patients.

The integrin antagonist, cilengitide, is a weak inhibitor of αIIbβ3 mediated platelet activation and inhibits platelet adhesion under flow

The RGD cyclic pentapetide, cilengitide, is a selective inhibitor of αvβ3 and αvβ5 integrins and was developed for antiangiogenic therapy. Since cilengitide interacts with platelet αIIbβ3 and platelets express αv integrins, the effect of cilengitide on platelet pro-coagulative response and adhesion is of interest. Flow-based adhesion assays were performed to evaluate platelet adhesion and rolling on von Willebrand factor (vWf), on fibrinogen and on human umbilical vein endothelial cells (HUVECs). Flow cytometry was used to detect platelet activation (PAC1) and secretion (CD62P) by cilengitide and light transmission aggregometry was used to detect cilengitide-dependent platelet aggregation. Cilengitide inhibited platelet adhesion to fibrinogen at concentrations above 250 µM [which is the Cmax in human studies] and adhesion to vWf and HUVECs at higher concentrations under physiologic flow conditions. Platelet aggregation was already impaired at cilengitide concentrations >10 µM. Activation of αIIbβ3 integrin was inhibited by 250 µM cilengitide, whereas platelet secretion was unaffected by cilengitide. No evidence of cilengitide-induced platelet activation was found at all tested concentrations (0.01-1500 µM). At higher concentrations, platelet activation was inhibited, predominantly due to αIIbβ3 inhibition.

Phase II study of cilengitide in the treatment of refractory or relapsed high-grade gliomas in children: a report from the Children's Oncology Group

BACKGROUND

Cilengitide, an αv integrin antagonist, has demonstrated activity in recurrent adult glioblastoma (GBM). The Children's Oncology Group ACNS0621 study thus evaluated whether cilengitide is active as a single agent in the treatment of children with refractory high-grade glioma (HGG). Secondary objectives were to investigate the pharmacokinetics and pharmacogenomics of cilengitide in this population.

METHODS

Cilengitide (1800 mg/m(2)/dose intravenous) was administered twice weekly until evidence of disease progression or unacceptable toxicity. Thirty patients (age range, 1.1-20.3 years) were enrolled, of whom 24 were evaluable for the primary response end point.

RESULTS

Toxicity was infrequent and mild, with the exception of one episode of grade 2 pain possibly related to cilengitide. Two intratumoral hemorrhages were reported, but only one (grade 2) was deemed to be possibly related to cilengitide and was in the context of disease progression. One patient with GBM received cilengitide for 20 months and remains alive with continuous stable disease. There were no other responders, with median time to tumor progression of 28 days (range, 11-114 days). Twenty-one of the 24 evaluable patients died, with a median time from enrollment to death of 172 days (range, 28-325 days). The 3 patients alive at the time of this report had a follow-up time of 37, 223, and 1068 days, respectively.

CONCLUSIONS

We conclude that cilengitide is not effective as a single agent for refractory pediatric HGG. However, further study evaluating combination therapy with cilengitide is warranted before a role for cilengitide in the treatment of pediatric HGG can be excluded.

The differentiation of pancreatic tumor-initiating cells by vitronectin can be blocked by cilengitide

OBJECTIVE

Pancreatic cancer is a leading cancer type and its molecular pathology is poorly understood. The only potentially curative therapeutic option available is complete surgical resection; however, this is inadequate as most of the patients are diagnosed at an advanced or metastatic stage. Tumor-initiating cells (TICs) constitute a subpopulation of cells within a solid tumor that sustain tumor growth, metastasis, and chemo/radioresistance. Within pancreatic cancer, TICs have been identified based on the expression of specific cell surface markers.

METHODS

We use a sphere formation assay to enrich putative TICs and use human serum as a driver of differentiation. We demonstrate by using specific blocking reagents that we can inhibit the differentiation process and maintain TIC-associated markers and genes.

RESULTS

We can induce differentiation of pancreatospheres with the addition of human serum, and we identified vitronectin as an inducer of differentiation. We inhibit differentiation by human serum using an arginine-glycine-aspartate-specific peptide, which is Cilengitide; hence, demonstrating this differentiation is mediated via specific integrin receptors.

CONCLUSIONS

Overall, our studies further the definition of pancreatic TICs and provide further insight into both the maintenance and differentiation of this lethal population.

αv-Integrin isoform expression in primary human tumors and brain metastases

To determine whether metastasis to brain is associated with altered expression patterns of integrins, we investigated the expression of αvβ3, αvβ5, αvβ6 and αvβ8 integrins in primary malignancies and metastases to brain of breast, lung and renal carcinomas and in malignant melanoma. Inhibitors of αv integrins are currently in clinical trials for glioblastoma. The role of integrins in the process of brain metastasis from other human tumors is unknown. Immunohistochemistry with novel integrin subtype specific rabbit monoclonal antibodies was performed on tissue microarrays of archival material of surgical biopsies taken from primary tumors and brain metastases. Integrin αvβ3 expression was increased in brain metastases compared to primary tumors of breast adenocarcinoma, non-small cell lung cancer, renal clear cell cancer and malignant cutaneous melanoma (all p < 0.01). Similarly, integrin αvβ8 expression was increased in brain metastases compared to primary tumors of breast cancer (p < 0.0001), lung cancer (p < 0.01) and renal cancer (p < 0.0001), with a similar trend in metastatic melanoma. Integrin αvβ5 was expressed in most primary tumors (98% breast cancer; 67% lung cancer; 90% renal cancer; 89% melanoma) and showed a stronger expression in brain metastases compared to primary tumors from lung cancer and melanoma (p < 0.05). Also integrin αvβ6 expression was increased in brain metastases compared to primary breast cancer (p < 0.001).

CONCLUSIONS

The stronger αv-integrin expression in brain metastases, especially of αvβ3 and αvβ8 integrins, suggests that certain αv integrin are involved in the process of brain metastasis. αv Integrins may be therapeutic targets for patients with metastatic cancer in brain.

Integrin targeted therapeutics

Integrins are heterodimeric, transmembrane receptors that function as mechanosensors, adhesion molecules and signal transduction platforms in a multitude of biological processes. As such, integrins are central to the etiology and pathology of many disease states. Therefore, pharmacological inhibition of integrins is of great interest for the treatment and prevention of disease. In the last two decades several integrin-targeted drugs have made their way into clinical use, many others are in clinical trials and still more are showing promise as they advance through preclinical development. Herein, this review examines and evaluates the various drugs and compounds targeting integrins and the disease states in which they are implicated.