A novel aminopeptidase N/CD13 inhibitor selectively targets an endothelial form of CD13 after coupling to proteins

Aminopeptidase N/CD13, a membrane-bound enzyme upregulated in tumor vasculature and involved in angiogenesis, can be used as a receptor for the targeted delivery of drugs to tumors through ligand-directed targeting approaches. We describe a novel peptide ligand (VGCARRYCS, called "G4") that recognizes CD13 with high affinity and selectivity. Enzymological and computational studies showed that G4 is a competitive inhibitor that binds to the catalytic pocket of CD13 through its N-terminal region. Fusing the peptide C-terminus to tumor necrosis factor-alpha (TNF) or coupling it to a biotin/avidin complex causes loss of binding and inhibitory activity against different forms of CD13, including natural or recombinant ectoenzyme and a membrane form expressed by HL60 promyelocytic leukemia cells (likely due to steric hindrance), but not binding to a membrane form of CD13 expressed by endothelial cells (ECs). Furthermore, G4-TNF systemically administered to tumor-bearing mice exerted anticancer effects through a CD13-targeting mechanism, indicating the presence of a CD13 form in tumor vessels with an accessible binding site. Biochemical studies showed that most CD13 molecules expressed on the surface of ECs are catalytically inactive. Other functional assays showed that these molecules can promote endothelial cell adhesion to plates coated with G4-avidin complexes, suggesting that the endothelial form of CD13 can exert catalytically independent biological functions. In conclusion, ECs express a catalytically inactive form of CD13 characterized by an accessible conformation that can be selectively targeted by G4-protein conjugates. This form of CD13 may represent a specific target receptor for ligand-directed targeted delivery of therapeutics to tumors.

A simple and robust nanosystem for photoacoustic imaging of bladder cancer based on α5β1-targeted gold nanorods

BACKGROUND

Early detection and removal of bladder cancer in patients is crucial to prevent tumor recurrence and progression. Because current imaging techniques may fail to detect small lesions of in situ carcinomas, patients with bladder cancer often relapse after initial diagnosis, thereby requiring frequent follow-up and treatments.

RESULTS

In an attempt to obtain a sensitive and high-resolution imaging modality for bladder cancer, we have developed a photoacoustic imaging approach based on the use of PEGylated gold nanorods (GNRs) as a contrast agent, functionalized with the peptide cyclic [CphgisoDGRG] (Iso4), a selective ligand of α5β1 integrin expressed by bladder cancer cells. This product (called GNRs@PEG-Iso4) was produced by a simple two-step procedure based on GNRs activation with lipoic acid-polyethyleneglycol(PEG-5KDa)-maleimide and functionalization with peptide Iso4. Biochemical and biological studies showed that GNRs@PEG-Iso4 can efficiently recognize purified integrin α5β1 and α5β1-positive bladder cancer cells. GNRs@PEG-Iso4 was stable and did not aggregate in urine or in 5% sodium chloride, or after freeze/thaw cycles or prolonged exposure to 55 °C, and, even more importantly, do not settle after instillation into the bladder. Intravesical instillation of GNRs@PEG-Iso4 into mice bearing orthotopic MB49-Luc bladder tumors, followed by photoacoustic imaging, efficiently detected small cancer lesions. The binding to tumor lesions was competed by a neutralizing anti-α5β1 integrin antibody; furthermore, no binding was observed to healthy bladders (α5β1-negative), pointing to a specific targeting mechanism.

CONCLUSION

GNRs@PEG-Iso4 represents a simple and robust contrast agent for photoacoustic imaging and diagnosis of small bladder cancer lesions.

Abstract 2381: Gold nanorods functionalized with an alpha5beta1 ligand: a simple and robust nanosystem for early bladder cancer detection

Early detection and removal of bladder cancer (BC) is crucial to prevent tumor recurrence and progression. Various imaging modalities have been used to diagnose BC, including computed tomography urography, intravenous urography, ultrasound echography, multiparametric magnetic resonance imaging, cystoscopy, and cystoscopy in conjunction with intravesical instillation of hexaminolaevulinic acid, a photodynamic diagnostic agent. However, all these imaging techniques show a very poor detection rate of small (<5mm) and flattened cancer lesions. Because of this limitation, patients with BC frequently relapse after initial diagnosis and need frequent follow-ups and treatments, resulting in a poor quality of life. For the same reason, BC has the highest cost/patient among all cancers. We have recently developed a new methodology to detect bladder cancer lesions based on bladder instillation with GNRs@Chit-Iso4, a nanosystem consisting of gold nanorods (GNRs) decorated with chitosan and functionalized with the head-to-tail cyclized [CphgisoDGRG] peptide (Iso4, a selective ligand of alpha5beta1-integrin expressed by BC cells), followed by low-frequency ultrasound-assisted shaking of nanoparticles necessary to prevent their sedimentation, and photoacoustic imaging of targeted tumor lesions. In murine models, this procedure can detect orthotopic BC lesions <0.5 mm, undetectable by standard imaging modalities (Alchera et al., Photoacoustic, 2022). In the attempt to develop a simpler and more effective imaging modality of BC, we have produced and preclinically evaluated new GNRs decorated with lipoic acid-polyethylene glycol (PEG -5KDa) and functionalized with Iso4. The resulting product, obtained by a simple 2-step procedure and called GNRs@PEG5K-Iso4, efficiently recognized alpha5beta1- and alpha5beta1-expressing cells, was stable in 90% urine, and was resistant to freezing- or salt-induced aggregation.GNRs@PEG5K-Iso4 did not undergo sedimentation after instillation into the bladder, thereby avoiding the need of the complex ultrasound-assisted shaking of nanoparticles and could efficiently detect BC lesions smaller than <0.5 mm in murine models. These results suggest that GNRs@PEG5K-Iso4 represents a simple and robust contrast agent for photoacoustic imaging and early diagnosis of small BC lesions.

Citation Format: Massimo Alfano, Elisa Alchera, Angelina Sacchi, Alessandro Gori, Irene Locatelli, Anna Maria Gasparri, Barbara Colombo, Giulia Anderluzzi, Paolo Armanetti, Luca Minichetti, Andrea Salonia, Angelo Corti, Flavio Curnis. Gold nanorods functionalized with an alpha5beta1 ligand: a simple and robust nanosystem for early bladder cancer detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2381.

A stapled chromogranin A-derived peptide homes in on tumors that express αvβ6 or αvβ8 integrins

Rationale: The αvβ6- and αvβ8-integrins, two cell-adhesion receptors upregulated in many tumors and involved in the activation of the latency associated peptide (LAP)/TGFβ complex, represent potential targets for tumor imaging and therapy. We investigated the tumor-homing properties of a chromogranin A-derived peptide containing an RGDL motif followed by a chemically stapled alpha-helix (called "5a"), which selectively recognizes the LAP/TGFβ complex-binding site of αvβ6 and αvβ8. Methods: Peptide 5a was labeled with IRDye 800CW (a near-infrared fluorescent dye) or with ¹⁸F-NOTA (a label for positron emission tomography (PET)); the integrin-binding properties of free peptide and conjugates were then investigated using purified αvβ6/αvβ8 integrins and various αvβ6/αvβ8 single - or double-positive cancer cells; tumor-homing, biodistribution and imaging properties of the conjugates were investigated in subcutaneous and orthotopic αvβ6-positive carcinomas of the pancreas, and in mice bearing subcutaneous αvβ8-positive prostate tumors. Results: In vitro studies showed that 5a can bind both integrins with high affinity and inhibits cell-mediated TGFβ activation. The 5a-IRDye and 5a-NOTA conjugates could bind purified αvβ6/αvβ8 integrins with no loss of affinity compared to free peptide, and selectively recognized various αvβ6/αvβ8 single- or double-positive cancer cells, including cells from pancreatic carcinoma, melanoma, oral mucosa, bladder and prostate cancer. In vivo static and dynamic optical near-infrared and PET/CT imaging and biodistribution studies, performed in mice with subcutaneous and orthotopic αvβ6-positive carcinomas of the pancreas, showed high target-specific uptake of fluorescence- and radio-labeled peptide by tumors and low non-specific uptake in other organs and tissues, except for excretory organs. Significant target-specific uptake of fluorescence-labeled peptide was also observed in mice bearing αvβ8-positive prostate tumors. Conclusions: The results indicate that 5a can home to αvβ6- and/or αvβ8-positive tumors, suggesting that this peptide can be exploited as a ligand for delivering imaging or anticancer agents to αvβ6/αvβ8 single- or double-positive tumors, or as a tumor-homing inhibitor of these TGFβ activators.

Quantification of Chromogranin A and Its Fragments in Biological Fluids

Human chromogranin A (CgA), a 439-residue long neurosecretory protein, can serve as a circulating biomarker for a wide range of neuroendocrine tumors. Increased levels of immunoreactive CgA are also present in the blood of patients with cardiovascular, gastrointestinal, or inflammatory diseases with, in certain cases, important diagnostic and prognostic implications. A growing body of evidence suggest that CgA and various CgA-derived fragments have complex roles in the regulation of cardiovascular system, metabolism, innate immunity, angiogenesis, and tissue repair, sometime with opposite biological effects. For example, while full-length CgA (CgA_1-439) inhibits angiogenesis, the CgA_1-373 fragment, at certain doses, is proangiogenic. Thus, the selective quantification of CgA and its fragments in the blood of patients (and in other biological fluids) is of great experimental and clinical interest. Here, we describe methods to produce CgA_1-439 and CgA_1-373 and to develop ELISAs capable of detecting these polypeptides in a very selective manner. The same approach can be used, in principle, also for developing assays for other fragments.

Early diagnosis of bladder cancer by photoacoustic imaging of tumor-targeted gold nanorods

Detection and removal of bladder cancer lesions at an early stage is crucial for preventing tumor relapse and progression. This study aimed to develop a new technological platform for the visualization of small and flat urothelial lesions of high-grade bladder carcinoma in situ (CIS). We found that the integrin α5β1, overexpressed in bladder cancer cell lines, murine orthotopic bladder cancer and human bladder CIS, can be exploited as a receptor for targeted delivery of GNRs functionalized with the cyclic CphgisoDGRG peptide (Iso4). The GNRs@Chit-Iso4 was stable in urine and selectively recognized α5β1 positive neoplastic urothelium, while low frequency ultrasound-assisted shaking of intravesically instilled GNRs@Chit-Iso4 allowed the distribution of nanoparticles across the entire volume of the bladder. Photoacoustic imaging of GNRs@Chit-Iso4 bound to tumor cells allowed for the detection of neoplastic lesions smaller than 0.5 mm that were undetectable by ultrasound imaging and bioluminescence.

Neuropilin-1 and Integrins as Receptors for Chromogranin A-Derived Peptides

Human chromogranin A (CgA), a 439 residue-long member of the "granin" secretory protein family, is the precursor of several peptides and polypeptides involved in the regulation of the innate immunity, cardiovascular system, metabolism, angiogenesis, tissue repair, and tumor growth. Despite the many biological activities observed in experimental and preclinical models for CgA and its most investigated fragments (vasostatin-I and catestatin), limited information is available on the receptor mechanisms underlying these effects. The interaction of vasostatin-1 with membrane phospholipids and the binding of catestatin to nicotinic and b2-adrenergic receptors have been proposed as important mechanisms for some of their effects on the cardiovascular and sympathoadrenal systems. Recent studies have shown that neuropilin-1 and certain integrins may also work as high-affinity receptors for CgA, vasostatin-1 and other fragments. In this case, we review the results of these studies and discuss the structural requirements for the interactions of CgA-related peptides with neuropilin-1 and integrins, their biological effects, their mechanisms, and the potential exploitation of compounds that target these ligand-receptor systems for cancer diagnosis and therapy. The results obtained so far suggest that integrins (particularly the integrin avb6) and neuropilin-1 are important receptors that mediate relevant pathophysiological functions of CgA and CgA fragments in angiogenesis, wound healing, and tumor growth, and that these interactions may represent important targets for cancer imaging and therapy.

Targeting the Blood–Brain Tumor Barrier with Tumor Necrosis Factor-α

The blood–brain tumor barrier represents a major obstacle for anticancer drug delivery to brain tumors. Thus, novel strategies aimed at targeting and breaching this structure are of great experimental and clinical interest. This review is primarily focused on the development and use of a derivative of tumor necrosis factor-α (TNF) that can target and alter the blood–brain-tumor-barrier. This drug, called NGR-TNF, consists of a TNF molecule fused to the Cys-Asn-Gly-Arg-Cys-Gly (CNGRCG) peptide (called NGR), a ligand of aminopeptidase N (CD13)-positive tumor blood vessels. Results of preclinical studies suggest that this peptide-cytokine fusion product represents a valuable strategy for delivering TNF to tumor vessels in an amount sufficient to break the biological barriers that restrict drug penetration in cancer lesions. Moreover, clinical studies performed in patients with primary central nervous system lymphoma, have shown that an extremely low dose of NGR-TNF (0.8 µg/m²) is sufficient to promote selective blood–brain-tumor-barrier alteration, increase the efficacy of R-CHOP (a chemo-immunotherapy regimen) and improve patient survival. Besides reviewing these findings, we discuss the potential problems related to the instability and molecular heterogeneity of NGR-TNF and review the various approaches so far developed to obtain more robust and homogeneous TNF derivatives, as well as the pharmacological properties of other peptide/antibody-TNF fusion products, muteins and nanoparticles that are potentially useful for targeting the blood–brain tumor barrier. Compared to other TNF-related drugs, the administration of extremely low-doses of NGR-TNF or its derivatives appear as promising non-immunogenic approaches to overcome TNF counter-regulatory mechanism and systemic toxicity, thereby enabling safe breaking of the BBTB.

DIPG-21. DIPG cells alter the permeability of the blood-brain barrier in the brainstem leading to treatment failure

Diffuse Intrinsic Pontine Glioma (DIPG) is an aggressive paediatric high-grade glioma with no effective therapies. The blood-brain barrier (BBB) presents a significant obstacle for delivery of therapeutics into the brain, especially in the brainstem. This study aims to investigate the effect of DIPG cells on the BBB in the brainstem. We hypothesized that the location of DIPG may result in a less permeable BBB than other brain regions. We compared two independent orthotopic models with the same DIPG cells injected in the cortical region or brainstem. We found that treatment with mTOR inhibitor, temsirolimus, significantly extended survival for cortical tumors compared with the same tumor in the brainstem (p=0.0097). Immunohistochemical analysis showed significant reduction of mTOR target, P-p70S6K, in the cortical region compared to brainstem in treated animals, with pharmacokinetic analysis confirming significantly higher temsirolimus levels in the cortical region. These findings suggest that cortical tumors respond better than brainstem tumors, and that a less permeable BBB in brainstem tumors contributes to treatment failure. To understand whether DIPG cells affect the BBB in the brainstem, single-cell RNA sequencing experiments were conducted on vasculature isolated from DIPG and matrigel-injected mice. Gene-ontology overrepresentation analyses identified downregulation in the P38MAPK pathway in endothelial cells from DIPG-injected mice, suggesting the potential for therapeutic manipulation with cytokines. Treatment with SNGR-TNFα, a derivative of an agent successfully used in improving drug penetration in CNS lymphoma patients, in an in vitro BBB/DIPG model significantly reduced transendothelial resistance, and further exploration into the effects on the BBB in vivo is currently being undertaken. Our studies indicate that the intact BBB in the brainstem in DIPG is a major reason for treatment failure, and DIPG cells directly influence the vasculature and response to treatment. This may lead to a novel DIPG treatment strategy and for other brain tumors.

Role of chromogranin A-derived fragments after resection of nonfunctioning pancreatic neuroendocrine tumors

PURPOSE

No single reliable biomarker is available for nonfunctioning pancreatic neuroendocrine tumors (NF-PanNETs). Vasostatin-1 (VS-1), the N-terminal fragment of chromogranin A (CgA), seems to be a more accurate biomarker compared to its precursor. Primary aim was to investigate the ability of VS-1, compared to total-CgA, to assess the effectiveness of surgical resection performed for NF-PanNETs. Secondary aim was to evaluate two additional CgA-derived fragments, pancreastatin (PST) and vasostatin-2 (VS-2), as possible biomarkers for NF-PanNETs.

METHODS

Consecutive patients who underwent surgery for NF-PanNETs at San Raffaele Scientific Institute were included (n = 35). Plasma levels of CgA and CgA-derived fragments were measured by Enzyme-Linked ImmunoSorbent Assay (ELISA), preoperatively and postoperatively.

RESULTS

Preoperative VS-1 was significantly higher compared to VS-1 measured on postoperative day 5 (POD5) (pre: 0.338 nM versus POD5: 0.147 nM, P < 0.001), whereas total-CgA significantly increased after surgery (pre: 1.123 nM versus POD5: 1.949 nM, P = 0.006). Overall, 24 patients showed ≥ 1 feature of tumor aggressiveness (T3-T4, nodal/distant metastases, Ki67 > 5%, microvascular/perineural invasion, necrosis). The median percentage decrease in VS-1 plasma levels was 63% (IQR 28-88%) among patients with aggressive tumors, compared to 13% (IQR 0-57%) in the remaining population (P = 0.033). No significant differences in terms of PST (P = 0.870) and VS-2 (P = 0.909) were observed between preoperative and postoperative time.

CONCLUSION

VS-1 provides an early assessment of surgical efficacy in patients who undergo resection for NF-PanNETs, especially in those with aggressive neoplasms. Total-CgA, PST and VS-2 have no clinical utility in this setting.

Chromogranin A plasma levels predict mortality in COVID-19

Background

Chromogranin A (CgA) and its fragment vasostatin I (VS-I) are secreted in the blood by endocrine/neuroendocrine cells and regulate stress responses. Their involvement in Coronavirus 2019 disease (COVID-19) has not been investigated.

Methods

CgA and VS-I plasma concentrations were measured at hospital admission from March to May 2020 in 190 patients. 40 age- and sex-matched healthy volunteers served as controls. CgA and VS-I levels relationship with demographics, comorbidities and disease severity was assessed through Mann Whitney U test or Spearman correlation test. Cox regression analysis and Kaplan Meier survival curves were performed to investigate the impact of the CgA and VS-I levels on in-hospital mortality.

Results

Median CgA and VS-I levels were higher in patients than in healthy controls (CgA: 0.558 nM [interquartile range, IQR 0.358–1.046] vs 0.368 nM [IQR 0.288–0.490] respectively, p = 0.0017; VS-I: 0.357 nM [IQR 0.196–0.465] vs 0.144 nM [0.144–0.156] respectively, p<0.0001). Concentration of CgA, but not of VS-I, significantly increased in patients who died (n = 47) than in survivors (n = 143) (median 0.948 nM [IQR 0.514–1.754] vs 0.507 nM [IQR 0.343–0.785], p = 0.00026). Levels of CgA were independent predictors of in-hospital mortality (hazard ratio 1.28 [95% confidence interval 1.077–1.522], p = 0.005) when adjusted for age, number of comorbidities, respiratory insufficiency degree, C-reactive protein levels and time from symptom onset to sampling. Kaplan Meier curves revealed a significantly increased mortality rate in patients with CgA levels above 0.558 nM (median value, log rank test, p = 0.001).

Conclusion

Plasma CgA levels increase in COVID-19 patients and represent an early independent predictor of mortality.

A Novel RGD-4C-Saporin Conjugate Inhibits Tumor Growth in Mouse Models of Bladder Cancer

Although toxin may have some advantages compared to chemotherapeutic drugs in cancer therapy, e.g. a potent cytotoxic activity and a reduced risk of resistance, their successful application in the treatments to solid tumors still remains to be fully demonstrated. In this study, we genetically modified the structure of the plant-derived single-chain ribosome inactivating protein saporin (SAP) by fusing its N-terminus to the ACDCRGDCFCG peptide (RGD-4C), an αv-integrin ligand, and explored the anti-tumor activity of the resulting protein (called RGD-SAP) in vitro and in vivo, using a model of muscle invasive bladder cancer. We found that the RGD-4C targeting domain enhances the cytotoxic activity of SAP against various tumor cell lines, in a manner dependent on αv-integrin expression levels. In a subcutaneous syngeneic model of bladder cancer, RGD-SAP significantly reduced tumor growth in a dose-dependent manner. Furthermore, systemic administration of RGD-SAP in combination with mitomycin C, a chemotherapeutic drug currently used to treat patients with bladder cancer, increased the survival of mice bearing orthotopic bladder cancer with no evidence of systemic toxicity. Overall, the results suggest that RGD-SAP represents an efficient drug that could be exploited, either alone or in combination with the state-of-the-art therapies, for the treatment of bladder cancer and, potentially, of other solid tumors.

Nanogold Functionalized With Lipoamide-isoDGR: A Simple, Robust and Versatile Nanosystem for αvβ3-Integrin Targeting

Gold nanoparticles functionalized with isoDGR, a tripeptide motif that recognizes αvβ3 integrin overexpressed in tumor vessels, have been used as nano-vectors for the delivery of cytokines to tumors. Functionalization of nanogold with this peptide has been achieved by coating nanoparticles with a peptide-albumin conjugate consisting of heterogeneous molecules with a variable number of linkers and peptides. To reduce nanodrug heterogeneity we have designed, produced and preclinically evaluated a homogeneous and well-defined reagent for nanogold functionalization, consisting of a head-to-tail cyclized CGisoDGRG peptide (iso1) coupled via its thiol group to maleimide-PEG₁₁-lipoamide (LPA). The resulting iso1-PEG₁₁-LPA compound can react with nanogold via lipoamide to form a stable bond. In vitro studies have shown that iso1, after coupling to nanogold, maintains its capability to bind purified αvβ3 and αvβ3-expressing cells. Nanogold functionalized with this peptide can also be loaded with bioactive tumor necrosis factor-α (TNF) to form a bi-functional nanodrug that can be stored for three days at 37°C or >1 year at low temperatures with no loss αvβ3-binding properties and TNF-cytolytic activity. Nanoparticles functionalized with both iso1 and TNF induced tumor eradication in WEHI-164 fibrosarcoma-bearing mice more efficiently than nanoparticles lacking the iso1 targeting moiety. These results suggest that iso1-PEG₁₁-LPA is an efficient and well-defined reagent that can be used to produce robust and more homogeneous nano-vectors for the delivery of TNF and other cytokines to αvβ3 positive cells.

Breaching the Blood-Brain Tumor Barrier for Tumor Therapy

Tumors affecting the central nervous system (CNS), either primary or secondary, are highly prevalent and represent an unmet medical need. Prognosis of these tumors remains poor, mostly due to the low intrinsic chemo/radio-sensitivity of tumor cells, a meagerly known role of the microenvironment and the poor CNS bioavailability of most used anti-cancer agents. The BBTB is the main obstacle for anticancer drugs to achieve therapeutic concentrations in the tumor tissues. During the last decades, many efforts have been devoted to the identification of modalities allowing to increase drug delivery into brain tumors. Until recently, success has been modest, as few of these approaches reached clinical testing and even less gained regulatory approval. In recent years, the scenario has changed, as various conjugates and drug delivery technologies have advanced into clinical testing, with encouraging results and without being burdened by a heavy adverse event profile. In this article, we review the different approaches aimed at increasing drug delivery to brain tumors, with particular attention to new, promising approaches that increase the permeability of the BBTB or exploit physiological transport mechanisms.

Enhancement of doxorubicin anti-cancer activity by vascular targeting using IsoDGR/cytokine-coated nanogold

Background

Gold nanospheres tagged with peptides containing isoDGR (isoAsp-Gly-Arg), an αvβ3 integrin binding motif, represent efficient carriers for delivering pro-inflammatory cytokines to the tumor vasculature. We prepared bi- or trifunctional nanoparticles bearing tumor necrosis factor-α (TNF) and/or interleukin-12 (IL12) plus a peptide containing isoDGR, and we tested their anti-cancer effects, alone or in combination with doxorubicin, in tumor-bearing mice.

Results

In vitro biochemical studies showed that both nanodrugs were monodispersed and functional in terms of binding to TNF and IL12 receptors and to αvβ3. In vivo studies performed in a murine model of fibrosarcoma showed that low doses of bifunctional nanoparticles bearing isoDGR and TNF (corresponding to few nanoparticles per cell) delayed tumor growth and increased the efficacy of doxorubicin without worsening its toxicity. Similar effects were obtained using trifunctional nanoparticles loaded with isoDGR, TNF and IL12. Mechanistic studies showed that nanoparticles bearing isoDGR and TNF could increase doxorubicin penetration in tumors a few hours after injection and caused vascular damage at later time points.

Conclusion

IsoDGR-coated gold nanospheres can be exploited as a versatile platform for single- or multi-cytokine delivery to cells of the tumor vasculature. Extremely low doses of isoDGR-coated nanodrugs functionalized with TNF or TNF plus IL12 can enhance doxorubicin anti-tumor activity.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00871-y.

The chromogranin A1-373 fragment reveals how a single change in the protein sequence exerts strong cardioregulatory effects by engaging neuropilin-1

AIM

Chromogranin A (CgA), a 439-residue long protein, is an important cardiovascular regulator and a precursor of various bioactive fragments. Under stressful/pathological conditions, CgA cleavage generates the CgA_1-373 proangiogenic fragment. The present work investigated the possibility that human CgA_1-373 influences the mammalian cardiac performance, evaluating the role of its C-terminal sequence.

METHODS

Haemodynamic assessment was performed on an ex vivo Langendorff rat heart model, while mechanistic studies were performed using perfused hearts, H9c2 cardiomyocytes and in silico.

RESULTS

On the ex vivo heart, CgA_1-373 elicited direct dose-dependent negative inotropism and vasodilation, while CgA_1-372 , a fragment lacking the C-terminal R₃₇₃ residue, was ineffective. Antibodies against the PGPQLR₃₇₃ C-terminal sequence abrogated the CgA_1-373 -dependent cardiac and coronary modulation. Ex vivo studies showed that CgA_1-373 -dependent effects were mediated by endothelium, neuropilin-1 (NRP1) receptor, Akt/NO/Erk1,2 pathways, nitric oxide (NO) production and S-nitrosylation. In vitro experiments on H9c2 cardiomyocytes indicated that CgA_1-373 also induced eNOS activation directly on the cardiomyocyte component by NRP1 targeting and NO involvement and provided beneficial action against isoproterenol-induced hypertrophy, by reducing the increase in cell surface area and brain natriuretic peptide (BNP) release. Molecular docking and all-atom molecular dynamics simulations strongly supported the hypothesis that the C-terminal R₃₇₃ residue of CgA_1-373 directly interacts with NRP1.

CONCLUSION

These results suggest that CgA_1-373 is a new cardioregulatory hormone and that the removal of R₃₇₃ represents a critical switch for turning "off" its cardioregulatory activity.

Circulating Chromogranin A Is Cleaved Into Vasoregulatory Fragments in Patients With Pancreatic Ductal Adenocarcinoma

Chromogranin A (CgA), a secretory protein released in the blood by the neuroendocrine system, consists of a mixture of full-length molecules and fragments endowed of vasoregulatory activity. The extent and the role of CgA fragmentation were investigated in patients with locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC, n=172). Multivariate analysis showed that full-length CgA was associated with better progression free and overall survival, whereas CgA C-terminal fragmentation was associated with worse prognosis. In vitro studies showed that PDAC cells can promote the cleavage of CgA C-terminal region by activating plasminogen to plasmin. Limited digestion of full-length CgA with plasmin abolished its anti-angiogenic activity and generated pro-angiogenic molecules. The fragmentation of CgA C-terminal region was increased also in murine models of PDAC. In these models, the inhibition of CgA fragmentation with aprotinin, an inhibitor of plasmin and other serine proteases, or the blockade of pro-angiogenic fragments with specific antibodies inhibited the growth of PDAC implanted subcutaneously in mice. Finally, administration of full-length CgA to mice bearing orthotopic PDAC reduced tumor perfusion, as measured by contrast-enhanced ultrasound. These findings suggest that PDAC can promote the cleavage of circulating CgA C-terminal region to generate fragments that regulate the tumor vascular biology and that may represent new potential therapeutic targets.

NGR-TNF Engineering with an N-Terminal Serine Reduces Degradation and Post-Translational Modifications and Improves Its Tumor-Targeting Activity

The therapeutic index of cytokines in cancer therapy can be increased by targeting strategies based on protein engineering with peptides containing the CNGRC (NGR) motif, a ligand that recognizes CD13-positive tumor vessels. We show here that the targeting domain of recombinant CNGRC-cytokine fusion proteins, such as NGR-TNF (a CNGRC-tumor necrosis factor-α (TNF) conjugate used in clinical studies) and NGR-EMAP-II, undergoes various post-translational modification and degradation reactions that lead to the formation of markedly heterogeneous products. These modifications include N-terminal cysteine acetylation or the formation of various asparagine degradation products, the latter owing to intramolecular interactions of the cysteine α-amino group with asparagine and/or its succinimide derivative. Blocking the cysteine α-amino group with a serine (SCNGRC) reduced both post-translational and degradation reactions. Furthermore, the serine residue reduced the asparagine deamidation rate to isoaspartate (another degradation product) and improved the affinity of NGR for CD13. Accordingly, genetic engineering of NGR-TNF with the N-terminal serine produced a more stable and homogeneous drug (called S-NGR-TNF) with improved antitumor activity in tumor-bearing mice, either when used alone or in combination with chemotherapy. In conclusion, the targeting domain of NGR-cytokine conjugates can undergo various untoward modification and degradation reactions, which can be markedly reduced by fusing a serine to the N-terminus. The SCNGRC peptide may represent a ligand for cytokine delivery to tumors more robust than conventional CNGRC. The S-NGR-TNF conjugate (more stable, homogeneous, and active than NGR-TNF) could be rapidly developed for clinical trials.

A stapled chromogranin A-derived peptide is a potent dual ligand for integrins αvβ6 and αvβ8

Combining 2D STD-NMR, computation, biochemical assays and click-chemistry, we have identified a chromogranin-A derived compound (5) that has high affinity and bi-selectivity for αvβ6 and αvβ8 integrins and is stable in microsomal preparations. 5 is suitable for nanoparticle functionalization and delivery to cancer cells, holding promise for diagnostic and/or therapeutic applications.

Boosting Interleukin-12 Antitumor Activity and Synergism with Immunotherapy by Targeted Delivery with isoDGR-Tagged Nanogold

The clinical use of interleukin-12 (IL12), a cytokine endowed with potent immunotherapeutic anticancer activity, is limited by systemic toxicity. The hypothesis is addressed that gold nanoparticles tagged with a tumor-homing peptide containing isoDGR, an αvβ3-integrin binding motif, can be exploited for delivering IL12 to tumors and improving its therapeutic index. To this aim, gold nanospheres are functionalized with the head-to-tail cyclized-peptide CGisoDGRG (Iso1) and murine IL12. The resulting nanodrug (Iso1/Au/IL12) is monodispersed, stable, and bifunctional in terms of αvβ3 and IL12-receptor recognition. Low-dose Iso1/Au/IL12, equivalent to 18-75 pg of IL12, induces antitumor effects in murine models of fibrosarcomas and mammary adenocarcinomas, with no evidence of toxicity. Equivalent doses of Au/IL12 (a nanodrug lacking Iso1) fail to delay tumor growth, whereas 15 000 pg of free IL12 is necessary to achieve similar effects. Iso1/Au/IL12 significantly increases tumor infiltration by innate immune cells, such as NK and iNKT cells, monocytes, and neutrophils. NK cell depletion completely inhibits its antitumor effects. Low-dose Iso1/Au/IL12 can also increase the therapeutic efficacy of adoptive T-cell therapy in mice with autochthonous prostate cancer. These findings indicate that coupling IL12 to isoDGR-tagged nanogold is a valid strategy for enhancing its therapeutic index and sustaining adoptive T-cell therapy.

Chromogranin A and its fragments in cardiovascular, immunometabolic, and cancer regulation

Chromogranin A (CgA)-the index member of the chromogranin/secretogranin secretory protein family-is ubiquitously distributed in endocrine, neuroendocrine, and immune cells. Elevated levels of CgA-related polypeptides, consisting of full-length molecules and fragments, are detected in the blood of patients suffering from neuroendocrine tumors, heart failure, renal failure, hypertension, rheumatoid arthritis, and inflammatory bowel disease. Full-length CgA and various CgA-derived peptides, including vasostatin-1, pancreastatin, catestatin, and serpinin, are expressed at different relative levels in normal and pathological conditions and exert diverse, and sometime opposite, biological functions. For example, CgA is overexpressed in genetic hypertension, whereas catestatin is diminished. In rodents, the administration of catestatin decreases hypertension, cardiac contractility, obesity, atherosclerosis, and inflammation, and it improves insulin sensitivity. By contrast, pancreastatin is elevated in diabetic patients, and the administration of this peptide to obese mice decreases insulin sensitivity and increases inflammation. CgA and the N-terminal fragment of vasostatin-1 can enhance the endothelial barrier function, exert antiangiogenic effects, and inhibit tumor growth in animal models, whereas CgA fragments lacking the CgA C-terminal region promote angiogenesis and tumor growth. Overall, the CgA system, consisting of full-length CgA and its fragments, is emerging as an important and complex player in cardiovascular, immunometabolic, and cancer regulation.

A Pilot Study on Continuous Infusion of 4% Albumin in Critically Ill Patients: Impact on Nosocomial Infection via a Reduction Mechanism for Oxidized Substrates

Care-related infections affect up to 11% of ICU patients. Running therapeutic albumin is sometimes associated to less infection: whether a specific method of its infusion is of any interest to modulate innate defense is unknown. Our objectives were: 1) to test whether the method for albumin infusion is important to prevent care-related infections and 2) to analyze in vitro the antioxidative role of albumin on host defense proteins during shock (using vasostatin-I as an example).

Design

In a prospective, randomized, open-label trial, shock patients were allocated to receive either continuously 4% albumin or intermittently 20% albumin, as long as they were infused with norepinephrine. A translational study including in vivo and in vitro analyses of albumin-vasostatin-I interactions is reported.

Setting

A tertiary ICU caring for 1,000 patients per year.

Patients

Fifty shock patients with serum albumin less than 20 g/L.

Interventions

In vivo colonization and nosocomial infections were recorded and time-dependent changes in serum albumin, chromogranin A, and vasostatin-I concentrations as well. In vitro, we studied biochemical albumin-vasostatin-I relationship using biochemical methods.

Measurements and Main Results

Over 18 days, we recorded a decrease in colonization (four vs 12 episodes; p = 0.035) and nosocomial infection frequency (two vs 13 episodes; p = 0.002) in patients infused continuously 4% albumin versus controls. In vitro, albumin interacts with the disulfide loop vasostatin-I (residues 17-40) and continuous 4% albumin infusion restores its oxidative status required for antimicrobial activity.

Conclusions

Continuous 4% albumin is effective in reducing care-related infections in shock patients by increasing the availability of antimicrobial vasostatin-I. This might guide future care of shock patients.

Real-time cellular impedance monitoring and imaging of biological barriers in a dual-flow membrane bioreactor

The generation of physiologically relevant in-vitro models of biological barriers can play a key role in understanding human diseases and in the development of more predictive methods for assessing toxicity and drug or nutrient absorption. Here, we present an advanced cell culture system able to mimic the dynamic environment of biological barriers while monitoring cell behaviour through real-time impedance measurements and imaging. It consists of a fluidic device with an apical and a basal flow compartment separated by a semi-permeable membrane. The main features of the device are the integration of sensing through transepithelial electrical impedance (TEEI) measurements and transparent windows for optical monitoring within a dual flow system. Caco-2 cells were cultured in the TEEI bioreactor under both flow and static conditions. Although no differences in the expression of peripheral actin and occludin were visible, the cells in dynamic conditions developed higher impedance values at low frequencies, indicative of a higher paracellular electrical impedance with respect to the static cultures. TEEI measurements at high frequency also enabled monitoring monolayer formation, which can be correlated with the observation of an RC behaviour in the impedance spectra. In particular, the cells subject to flow showed accelerated barrier formation and increased vitality with respect to the static controls, again highlighting the importance of dynamic conditions for epithelial cells.

Physiological levels of chromogranin A prevent doxorubicin-induced cardiotoxicity without impairing its anticancer activity

The clinical use of doxorubicin (Doxo), a widely used anticancer chemotherapeutic drug, is limited by dose-dependent cardiotoxicity. We have investigated whether chromogranin A (CgA), a cardioregulatory protein released in the blood by the neuroendocrine system and by the heart itself, may contribute to regulation of the cardiotoxic and antitumor activities of Doxo. The effects of a physiologic dose of full-length recombinant CgA on Doxo-induced cardiotoxicity and antitumor activity were investigated in rats using in vivo and ex vivo models and in murine models of melanoma, fibrosarcoma, lymphoma, and lung cancer, respectively. The effect of Doxo on circulating levels of CgA was also investigated. In vivo and ex vivo mechanistic studies showed that CgA can prevent Doxo-induced heart inflammation, oxidative stress, apoptosis, fibrosis, and ischemic injury. On the other hand, CgA did not impair the anticancer activity of Doxo in all the murine models investigated. Furthermore, we observed that Doxo can reduce the intracardiac expression and release of CgA in the blood (i.e., an important cardioprotective agent). These findings suggest that administration of low-dose CgA to patients with low levels of endogenous CgA might represent a novel approach to prevent Doxo-induced adverse events without impairing antitumor effects.-Rocca, C., Scavello, F., Colombo, B., Gasparri, A. M., Dallatomasina, A., Granieri, M. C., Amelio, D., Pasqua, T., Cerra, M. C., Tota, B., Corti, A., Angelone, T. Physiological levels of chromogranin A prevent doxorubicin-induced cardiotoxicity without impairing its anticancer activity.

Overcoming Biological Barriers in Neuroblastoma Therapy: The Vascular Targeting Approach with Liposomal Drug Nanocarriers

Neuroblastoma is a rare pediatric cancer characterized by a wide clinical behavior and adverse outcome despite aggressive therapies. New approaches based on targeted drug delivery may improve efficacy and decrease toxicity of cancer therapy. Furthermore, nanotechnology offers additional potential developments for cancer imaging, diagnosis, and treatment. Following these lines, in the past years, innovative therapies based on the use of liposomes loaded with anticancer agents and functionalized with peptides capable of recognizing neuroblastoma cells and/or tumor-associated endothelial cells have been developed. Studies performed in experimental orthotopic models of human neuroblastoma have shown that targeted nanocarriers can be exploited for not only decreasing the systemic toxicity of the encapsulated anticancer drugs, but also increasing their tumor homing properties, enhancing tumor vascular permeability and perfusion (and, consequently, drug penetration), inducing tumor apoptosis, inhibiting angiogenesis, and reducing tumor glucose consumption. Furthermore, peptide-tagged liposomal formulations are proved to be more efficacious in inhibiting tumor growth and metastatic spreading of neuroblastoma than nontargeted liposomes. These findings, herein reviewed, pave the way for the design of novel targeted liposomal nanocarriers useful for multitargeting treatment of neuroblastoma.

Spatiotemporal Regulation of Tumor Angiogenesis by Circulating Chromogranin A Cleavage and Neuropilin-1 Engagement

The unbalanced production of pro- and antiangiogenic factors in tumors can lead to aberrant vasculature morphology, angiogenesis, and disease progression. In this study, we report that disease progression in various murine models of solid tumors is associated with increased cleavage of full-length chromogranin A (CgA), a circulating vasoregulatory neurosecretory protein. Cleavage of CgA led to the exposure of the highly conserved PGPQLR site, which corresponds to residues 368-373 of human CgA_1-373, a fragment that has proangiogenic activity. Antibodies against this site, unable to bind full-length CgA, inhibited angiogenesis and reduced tumor perfusion and growth. The PGPQLR sequence of the fragment, but not of the precursor, bound the VEGF-binding site of neuropilin-1; the C-terminal arginine (R₃₇₃) of the sequence was crucial for binding. The proangiogenic activity of the CgA_1-373 was blocked by anti-neuropilin-1 antibodies as well as by nicotinic acetylcholine receptor antagonists, suggesting that these receptors, in addition to neuropilin-1, play a role in the proangiogenic activity of CgA_1-373. The R₃₇₃ residue was enzymatically removed in plasma, causing loss of neuropilin-1 binding and gain of antiangiogenic activity. These results suggest that cleavage of the R₃₇₃R₃₇₄ site of circulating human CgA in tumors and the subsequent removal of R₃₇₃ in the blood represent an important "on/off" switch for the spatiotemporal regulation of tumor angiogenesis and may serve as a novel therapeutic target. SIGNIFICANCE: This work reveals that the interaction between fragmented chromogranin A and neuropilin-1 is required for tumor growth and represents a novel potential therapeutic target.

Association between preoperative Vasostatin-1 and pathological features of aggressiveness in localized nonfunctioning pancreatic neuroendocrine tumors (NF-PanNET)

BACKGROUND

A reliable and accessible biomarker for nonfunctioning pancreatic neuroendocrine tumors (NF-PanNET) is currently unavailable. Chromogranin A (CgA) represents the best-described neuroendocrine biomarker, but its accuracy is low. Vasostatin-1 (VS-1), a fragment derived from the cleavage of CgA, was recently investigated and found to be more accurate as tumor biomarker in a cohort of patients affected by mainly metastatic small intestinal NET.

METHODS

Patients submitted to surgery for sporadic localized NF-PanNET at San Raffaele Hospital were included. Preoperative plasma samples were prospectively collected. Circulating levels of total-CgA and VS-1 were retrospectively investigated by sandwich Enzyme-Linked ImmunoSorbent Assays.

RESULTS

Overall, 50 patients were included. VS-1 value (P=0.0001) was the only preoperatively retrievable factor independently associated with NF-PanNET size. No significant correlation between CgA and tumor diameter was found (P = 0.057). A VS-1 value of 0.39 nM was identified as the optimal VS-1 cut-off accurately associated with NF-PanNET larger than 4 cm. Patients with VS-1 > 0.39 nM had a significantly higher frequency of microvascular invasion (P = 0.005) and nodal metastasis (P = 0.027). Median VS-1 plasma level was significantly higher in the presence of microvascular invasion (P = 0.001) and nodal metastasis (P = 0.012). PPI assumption significantly increased total-CgA levels, but not those of VS-1 (P = 0.111).

CONCLUSIONS

In localized, non-metastatic NF-PanNET, VS-1 is strongly associated to tumor dimension and its plasma levels are significantly higher in the presence of microvascular invasion and nodal metastases; moreover, VS-1 value is not affected by the PPI use.

Catestatin regulates vesicular quanta through modulation of cholinergic and peptidergic (PACAPergic) stimulation in PC12 cells

We have previously shown that the chromogranin A (CgA)-derived peptide catestatin (CST: hCgA_352-372) inhibits nicotine-induced secretion of catecholamines from the adrenal medulla and chromaffin cells. In the present study, we seek to determine whether CST regulates dense core (DC) vesicle (DCV) quanta (catecholamine and chromogranin/secretogranin proteins) during acute (0.5-h treatment) or chronic (24-h treatment) cholinergic (nicotine) or peptidergic (PACAP, pituitary adenylyl cyclase activating polypeptide) stimulation of PC12 cells. In acute experiments, we found that both nicotine (60 μM) and PACAP (0.1 μM) decreased intracellular norepinephrine (NE) content and increased ³H-NE secretion, with both effects markedly inhibited by co-treatment with CST (2 μM). In chronic experiments, we found that nicotine and PACAP both reduced DCV and DC diameters and that this effect was likewise prevented by CST. Nicotine or CST alone increased expression of CgA protein and together elicited an additional increase in CgA protein, implying that nicotine and CST utilize separate signaling pathways to activate CgA expression. In contrast, PACAP increased expression of CgB and SgII proteins, with a further potentiation by CST. CST augmented the expression of tyrosine hydroxylase (TH) but did not increase intracellular NE levels, presumably due to its inability to cause post-translational activation of TH through serine phosphorylation. Co-treatment of CST with nicotine or PACAP increased quantal size, plausibly due to increased synthesis of CgA, CgB and SgII by CST. We conclude that CST regulates DCV quanta by acutely inhibiting catecholamine secretion and chronically increasing expression of CgA after nicotinic stimulation and CgB and SgII after PACAPergic stimulation.

Enhancement of Tumor Homing by Chemotherapy-Loaded Nanoparticles

Targeted delivery of anticancer drugs with nanocarriers can reduce side effects and ameliorate therapeutic efficacy. However, poorly perfused and dysfunctional tumor vessels limit the transport of the payload into solid tumors. The use of tumor-penetrating nanocarriers might enhance tumor uptake and antitumor effects. A peptide containing a tissue-penetrating (TP) consensus motif, capable of recognizing neuropilin-1, is here fused to a neuroblastoma-targeting peptide (pep) previously developed. Neuroblastoma cell lines and cells derived from both xenografts and high-risk neuroblastoma patients show overexpression of neuropilin-1. In vitro studies reveal that TP-pep binds cell lines and cells derived from neuroblastoma patients more efficiently than pep. TP-pep, after coupling to doxorubicin-containing stealth liposomes (TP-pep-SL[doxorubicin]), enhances their uptake by cells and cytotoxic effects in vitro, while increasing tumor-binding capability and homing in vivo. TP-pep-SL[doxorubicin] treatment enhances the Evans Blue dye accumulation in tumors but not in nontumor tissues, pointing to selective increase of vascular permeability in tumor tissues. Compared to pep-SL[doxorubicin], TP-pep-SL[doxorubicin] shows an increased antineuroblastoma activity in three neuroblastoma animal models mimicking the growth of neuroblastoma in humans. The enhancement of drug penetration in tumors by TP-pep-targeted nanoparticles may represent an innovative strategy for neuroblastoma.

Purification and Characterization of Single-Chain Urokinase-Type Plasminogen Activator (Pro-Urokinase) from Human A431 Cells

A single-chain urokinase-type plasminogen activator (A431sc-uPA) was purified ˜18,000-fold from A431 human epidermoid carcinoma cell supernatants by monoclonal antibody immunoaffinity chromatography on 5B4-agarose and ion-exchange FPLC (overall yield 63%). More than 100 jig of A431sc-uPA can be recovered per liter of supernatant. The product is homogeneous by SDS-PAGE and reverse phase FPLC analysis while two main isoelectric forms of pi 9.05 and pi 9.20 were observed by IEF. SDS-PAGE in reducing and non-reducing conditions, Western blot analysis and zymography showed that A431sc-uPA is a single-chain protein of about 50,000 Mr immunologically related to urokinase (uPA) and distinct from tissue plasminogen activator (tPA). The N-terminal aminoacid sequence of A431sc-uPA (27 residues) is identical to that of human kidney single-chain uPA. A431sc-uPA does not incorporate 3H-diisopropylfluorophosphate and is virtually inactive on the synthetic substrate S-2444. Plasmin treatment converts A431sc-uPA into a two-chain active form with a fibrinolytic specific activity of 123,000 I.U./mg.

A Monoclonal Antibody that Recognizes the Receptor Binding Region of Human Urokinase Plasminogen Activator

An anti-urokinase monoclonal antibody 5B4 (MAB 5B4) was obtained by fusing the murine myeloma cell line X63-Ag8.653 with the spleen cells from a female BALB/c mouse immunized with high-molecular-weight urokinase (HMW-uPA).

MAB 5B4 is an IgGl that binds selectively to the single-chain form of uPA (sc-uPA), to HMW-uPA and to the 17,000 Mr aminoterminal fragment of the A-chain (ATF) but not to the low-molecular-weight urokinase (LMW-uPA) nor to the reduced form of HMW-uPA. This strongly suggests that MAB 5B4 recognizes a conformational determinant on the A-chain.

The antibody has an affinity constant for uPA-Sepharose of 1.42 × 107 M−1, calculated from equilibrium binding data, and can be used for one step purification of HMW-uPA by immunoaffinity chromatography.

MAB 5B4 and the previously obtained antibody 105IF10 (16) recognize the A-chain: the epitopes, however, are distinct as shown by double-antibody-sandwich enzyme immunoassay.

Finally MAB 5B4 inhibits the binding of ATF to the uPA receptor of different human cells, whereas 105IF10 does not. Thus this antibody represents a potentially, useful tool for the study of uPA receptor physiology.

Differential Detection of Single-Chain and Two-Chain Urokinase-Type Plasminogen Activator by a New Immunoadsorbent-Amidolytic Assay (IAA)

A new immunoadsorbent-amidolytic assay (IAA) for the specific differential detection of two-chain urokinase-type plasminogen activator (tcu-PA) and its single-chain precursor (scu-PA) in cell culture supernatants has been developed. The assay combines the selectivity of immunoassays with the specificity of enzyme activity assays exploiting both the antigenic and enzymatic properties of the two proteins. tcu-PA and scu-PA are selectively immunoadsorbed on the wells of a microtiterplate coated with the monoclonal antibody 5B4 and tested for enzymatic activity before and after activation by plasmin treatment. Both proteins are determined with similar efficiency since overlapping dose-response curves were obtained in the range between 12.5-200 ng/ml. The assay has been used to determine tcu-PA and scu-PA in A431 human epidermoid carcinoma cell supernatants. The analytical recoveries for tcu-PA and scu-PA added to A431 cell supernatants were 95.2% and 96.9% respectively. The intra- and inter-assay variations (CV) were 5.5% and 9.0% for tcu-PA and 9.7% and 9.8% for scu-PA respectively.

Abstract 3879: Enhancement of tumor penetration by drug-loaded nanoparticles: An innovative targeted strategy for neuroblastoma

Background: Anti-cancer drugs-loaded targeted nanocarriers can reduce side-effects and improve therapeutic efficacy in preclinical studies. However, poorly perfused and dysfunctional tumour vessels limit the transport of the payload into the parenchyma of solid tumours. The use of tumour-penetrating nanocarriers might enhance tumour penetration and anti-tumour effects.

Methods: A consensus motif, mediator of tissue penetration (TP) was added to a previously characterized neuroblastoma (NB)-targeting peptide (pep). In vitro NB cell association and internalization of TP-pep, either free or coupled to Stealth Liposomes (SL), were tested by FACS and confocal microscopy. In vitro cytotoxic potential of a novel doxorubicin (DXR)-loaded liposomal (TP-pep-SL[DXR]) was evaluated by MTS assay. Three mouse xenograft models mimicking the growth and spread of NB in humans (injection routes: subcutaneous; adrenal gland; tail vein) were enrolled to examine in vivo penetration, vascular permeability, tumour glucose consumption and sensitivity in response to TP-pep-SL[DXR].

Results: Compared to pep, TP-pep increases its cellular association in vitro on cell lines and cells derived from NB patients. When coupled to SL, TP-pep enhances liposomes penetration and cytotoxic effects in vitro and increases binding and penetration in a mouse model of NB. Moreover, in vivo accumulation of Evans Blue dye within the tumour mass reveals that TP-pep-SL[DXR] increases the tumour vascular permeability into NB tumour mass, but not in non-tumour tissues. Compared to pep-targeted liposomes, TP-pep-SL[DXR] leads to an increased anti-NB effect towards all the animal models tested.

Conclusion: Our findings demonstrate that the enhancement of tumour penetration by drug-loaded nanoparticles might represent an innovative targeted strategy for NB.

Citation Format: Mirco Ponzoni, Chiara Brignole, Laura Emionite, Silvia Bruno, Daniela Guarnieri, Leopoldo Sitia, Matteo Bauckneht, Ambra Buschiazzo, Andrea Rossi, Daniela Di Paolo, Patrizia Perri, Flavio Curnis, Alessandro Gori, Angela Rita Sementa, Michele Cilli, Pier Paolo Pompa, Gianmario Sambuceti, Angelo Corti, Fabio Pastorino. Enhancement of tumor penetration by drug-loaded nanoparticles: An innovative targeted strategy for neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3879.

Epitope Mapping of the Anti-Urokinase Monoclonal Antibody 5B4 by Isolated Domains of Urokinase

The amino terminal fragment (ATF) of urokinase-type plasminogen activator (uPA) is a degradation product comprising the entire growth factor-like and kringle domains. It has been previously shown that ATF is able to bind to the u-PA receptor through the growth factor-like domain and that the anti u-PA monoclonal antibody 5B4 (Mab 5B4) binds to ATF preventing u-PA receptor binding. To localize more precisely the epitope recognized by Mab 5B4, ATF was subfragmented by controlled enzymatic proteolysis with V8 protease.

Three subfragments of 4,000 Mr (F-4k), 11,000 Mr (F-llk) and 12,0 Mr (F-12k) were purified from the reaction mixture and characterized. SDS-PAGE under reducing and non-reducing conditions, N-terminal aminoacid sequence analysis and C-terminal aminoacid analysis of each fragment indicate that F-4k and F-llk correspond to intact growth factor-like domain and kringle domain (residues 4-43 and 44-135 respectively) while F-12k corresponds to the kringle. domain cleaved in the first loop at the glu52-gly53 bond.

By Western blot and competitive binding experiments we show that Mab 5B4 recognizes an epitope located on the kringle domain of u-PA and that the binding is strongly reduced when the kringle contains an additional cleavage in its first loop.

Since the receptor binding site of u-PA has been previously shown to be located on the growth factor-like domain, Mab 5B4 inhibits the binding of uPA to its cellular receptor likely by steric hindrance.

Besides the proven utility in epitope localization of anti u-PA monoclonal antibodies, these u-PA fragments may represent powerful tools for studies of structure-function relationship of u-PA.

Succinimide-Based Conjugates Improve IsoDGR Cyclopeptide Affinity to αvβ3 without Promoting Integrin Allosteric Activation

The isoDGR sequence is an integrin-binding motif that has been successfully employed as a tumor-vasculature-homing molecule or for the targeted delivery of drugs and diagnostic agents to tumors. In this context, we previously demonstrated that cyclopeptide 2, the product of the conjugation of c(CGisoDGRG) (1) to 4-( N-maleimidomethyl)cyclohexane-1-carboxamide, can be successfully used as a tumor-homing ligand for nanodrug delivery to neoplastic tissues. Here, combining NMR, computational, and biochemical methods, we show that the succinimide ring contained in 2 contributes to stabilizing interactions with α_vβ₃, an integrin overexpressed in the tumor vasculature. Furthermore, we demonstrate that various cyclopeptides containing the isoDGR sequence embedded in different molecular scaffolds do not induce α_vβ₃ allosteric activation and work as pure integrin antagonists. These results could be profitably exploited for the rational design of novel isoDGR-based ligands and tumor-targeting molecules with improved α_vβ₃-binding properties and devoid of adverse integrin-activating effects.

Catestatin Inhibits Obesity-Induced Macrophage Infiltration and Inflammation in the Liver and Suppresses Hepatic Glucose Production, Leading to Improved Insulin Sensitivity

The activation of Kupffer cells (KCs) and monocyte-derived recruited macrophages (McMΦs) in the liver contributes to obesity-induced insulin resistance and type 2 diabetes. Mice with diet-induced obesity (DIO mice) treated with chromogranin A peptide catestatin (CST) showed several positive results. These included decreased hepatic/plasma lipids and plasma insulin, diminished expression of gluconeogenic genes, attenuated expression of proinflammatory genes, increased expression of anti-inflammatory genes in McMΦs, and inhibition of the infiltration of McMΦs resulting in improvement of insulin sensitivity. Systemic CST knockout (CST-KO) mice on normal chow diet (NCD) ate more food, gained weight, and displayed elevated blood glucose and insulin levels. Supplementation of CST normalized glucose and insulin levels. To verify that the CST deficiency caused macrophages to be very proinflammatory in CST-KO NCD mice and produced glucose intolerance, we tested the effects of (sorted with FACS) F4/80⁺Ly6C^- cells (representing KCs) and F4/80^-Ly6C⁺ cells (representing McMΦs) on hepatic glucose production (HGP). Both basal HGP and glucagon-induced HGP were markedly increased in hepatocytes cocultured with KCs and McMΦs from NCD-fed CST-KO mice, and the effect was abrogated upon pretreatment of CST-KO macrophages with CST. Thus, we provide a novel mechanism of HGP suppression through CST-mediated inhibition of macrophage infiltration and function.

Regulation of tumor growth by circulating full-length chromogranin A

Chromogranin A (CgA), a neuroendocrine secretory protein, and its fragments are present in variable amounts in the blood of normal subjects and cancer patients. We investigated whether circulating CgA has a regulatory function in tumor biology and progression. Systemic administration of full-length CgA, but not of fragments lacking the C-terminal region, could reduce tumor growth in murine models of fibrosarcoma, mammary adenocarcinoma, Lewis lung carcinoma, and primary and metastatic melanoma, with U-shaped dose-response curves. Tumor growth inhibition was associated with reduction of microvessel density and blood flow in neoplastic tissues. Neutralization of endogenous CgA with antibodies against its C-terminal region (residues 410-439) promoted tumor growth. Structure-function studies showed that the C-terminal region of CgA contains a bioactive site and that cleavage of this region causes a marked loss of anti-angiogenic and anti-tumor potency. Mechanistic studies showed that full-length CgA could induce, with a U-shaped dose-response curve, the production of protease nexin-1 in endothelial cells, a serine protease inhibitor endowed of anti-angiogenic activity. Gene silencing or neutralization of protease nexin-1 with specific antibodies abolished both anti-angiogenic and anti-tumor effects of CgA. These results suggest that circulating full-length CgA is an important inhibitor of angiogenesis and tumor growth, and that cleavage of its C-terminal region markedly reduces its activity. Pathophysiological changes in CgA blood levels and/or its fragmentation might regulate disease progression in cancer patients.

Inhibition of chronic lymphocytic leukemia progression by full-length chromogranin A and its N-terminal fragment in mouse models

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of leukemic B cells in peripheral blood, bone marrow (BM) and lymphoid tissues, and by their recirculation between these compartments. We observed that circulating chromogranin A (CgA) and its N-terminal fragment (called vasostatin-1, CgA_1-76), two neuroendocrine secretory polypeptides that enhance the endothelial barrier function, are present in variable amounts in the blood of CLL patients. Studies in animal models showed that daily administration of full-length human CgA_1-439 (0.3 μg, i.v., or 1.5 μg/mouse, i.p.) can reduce the BM/blood ratio of leukemic cells in Eμ-TCL1 mice, a transgenic model, and decrease BM, lung and kidney infiltration in Rag2^−/−γc^−/− mice engrafted with human MEC1 CLL cells, a xenograft model. This treatment also reduced the loss of body weight and improved animal motility. In vitro, CgA enhanced the endothelial barrier integrity and the trans-endothelial migration of MEC1 cells, with a bimodal dose-response curve. Vasostatin-1, but not a larger fragment consisting of N-terminal and central regions of CgA (CgA_1-373), inhibited CLL progression in the xenograft model, suggesting that the C-terminal region is crucial for CgA activity and that the N-terminal domain contains a site that is activated by proteolytic cleavage. These findings suggest that circulating full-length CgA and its fragments may contribute to regulate leukemic cell trafficking and reduce tissue infiltration in CLL.

Tumor cell-associated immune checkpoint molecules - Drivers of malignancy and stemness

Inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor cells in different tumor types. It was thought that the main function of tumor cell-associated immune checkpoint molecules would be the modulation (down- or upregulation) of antitumor immune responses. In recent years, however, it has become clear that the expression of immune checkpoint molecules on tumor cells has important consequences on the biology of the tumor cells themselves. In particular, a causal relationship between the expression of these molecules and the acquisition of malignant traits has been demonstrated. Thus, immune checkpoint molecules have been shown to promote the epithelial-mesenchymal transition of tumor cells, the acquisition of tumor-initiating potential and resistance to apoptosis and antitumor drugs, as well as the propensity to disseminate and metastasize. Herein, we review this evidence, with a main focus on PD-L1, the most intensively investigated tumor cell-associated immune checkpoint molecule and for which most information is available. Then, we discuss more concisely other tumor cell-associated immune checkpoint molecules that have also been shown to induce the acquisition of malignant traits, such as PD-1, B7-H3, B7-H4, Tim-3, CD70, CD28, CD137, CD40 and CD47. Open questions in this field as well as some therapeutic approaches that can be derived from this knowledge, are also addressed.

Circulating chromogranin A and its fragments as diagnostic and prognostic disease markers

Chromogranin A (CgA), a secretory protein released in the blood by neuroendocrine cells and neurons, is the precursor of various bioactive fragments involved in the regulation of the cardiovascular system, metabolism, innate immunity, angiogenesis, and tissue repair. After the original demonstration that circulating CgA can serve as a biomarker for a wide range of neuroendocrine tumors, several studies have shown that increased levels of CgA can be present also in the blood of patients with cardiovascular, gastrointestinal, and inflammatory diseases with, in certain cases, important diagnostic and prognostic implications. Considering the high structural and functional heterogeneity of the CgA system, comprising precursor and fragments, it is not surprising that the different immunoassays used in these studies led, in some cases, to discrepant results. Here, we review these notions and we discuss the importance of measuring total-CgA, full-length CgA, specific fragments, and their relative levels for a more thorough assessment of the pathophysiological function and diagnostic/prognostic value of the CgA system.

Glycine N-methylation in NGR-Tagged Nanocarriers Prevents Isoaspartate formation and Integrin Binding without Impairing CD13 Recognition and Tumor Homing

NGR (asparagine-glycine-arginine) is a tumor vasculature-homing peptide motif widely used for the functionalization of drugs, nanomaterials and imaging compounds for cancer treatment and diagnosis. Unfortunately, this motif has a strong propensity to undergo rapid deamidation. This reaction, which converts NGR into isoDGR, is associated with receptor switching from CD13 to integrins, with potentially important manufacturing, pharmacological and toxicological implications. It is found that glycine N-methylation of NGR-tagged nanocarriers completely prevents asparagine deamidation without impairing CD13 recognition. Studies in animal models have shown that the methylated NGR motif can be exploited for delivering radiolabeled compounds and nanocarriers, such as tumor necrosis factor-α (TNF)-bearing nanogold and liposomal doxorubicin, to tumors with improved selectivity. These findings suggest that this NGR derivative is a stable and efficient tumor-homing ligand that can be used for delivering functional nanomaterials to tumor vasculature.