In vivo NIRF imaging-guided delivery of a novel NGR-VEGI fusion protein for targeting tumor vasculature

Modulating tumour vascular normalisation using triptolide-loaded NGR-functionalized liposomes for enhanced cancer radiotherapy

Radiotherapy is an effective therapy in tumour treatment. However, the characteristics of the tumour microenvironment, including hypoxia, low pH, and interstitial fluid pressure bring about radioresistance. To improve the anti-tumour effect of radiotherapy, it has been demonstrated that antiangiogenic therapy can be employed to repair the structural and functional defects of tumour angiogenic vessels, thereby preventing radioresistance or poor therapeutic drug delivery. In this study, we prepared triptolide (TP)-loaded Asn-Gly-Arg (NGR) peptide conjugated mPEG2000-DSPE-targeted liposomes (NGR-PEG-TP-LPs) to induce tumour blood vessel normalisation, to the end of increasing the sensitivity of tumour cells to radiotherapy. Further, to quantify the tumour vessel normalisation window, the structure and functionality of tumour blood vessels post NGR-PEG-TP-LPs treatment were evaluated. Thereafter, the anti-tumour effect of radiotherapy following these treatments was evaluated using HCT116 xenograft-bearing mouse models based on the tumour vessel normalisation period window. The results obtained showed that NGR-PEG-TP-LPs could modulate tumour vascular normalisation to increase the oxygen content of the tumour microenvironment and enhance the efficacy of radiotherapy. Further, liver and kidney toxicity tests indicated that NGR-PEG-TP-LPs are safe for application in cancer treatment.

Conjugation to PEG as a Strategy to Limit the Uptake of Drugs by the Placenta: Potential Applications for Drug Administration in Pregnancy

Here, we evaluated the feasibility of non-prodrug PEG-drug conjugates to decrease the accumulation of drugs within the placental tissues. The results showed that PEG was biocompatible with the human placenta with no alteration of the basal rate of proliferation or apoptosis in term placental explants. No significant changes in the released levels of lactate dehydrogenase and the human chorionic gonadotropin were observed after PEG treatment. The cellular uptake studies revealed that conjugating Cy5.5 and haloperidol to PEG significantly reduced (by up to ∼40-fold) their uptake by the placenta. These findings highlight the viability of novel non-prodrug polymer-drug conjugates to avoid the accumulation of drugs within the placenta.

Targeted imaging of esophageal adenocarcinoma with a near-infrared fluorescent peptide

BACKGROUND

Targeted optical imaging offers a noninvasive and accurate method for the early detection of gastrointestinal tumors, especially for flat appearances. In our previous study, a sequence of SNFYMPL (SNF) was identified as a specific peptide to bind to esophageal carcinoma using phage-display technology. This study aimed to evaluate the tumor-targeting efficacy of Cy5.5-conjugated SNF probe for imaging of esophageal carcinoma in vitro and in vivo.

METHODS

The SNF-Cy5.5 probe was synthesized and then identified using High Performance Liquid Chromatography (HPLC) and mass spectrometry (MS). Confocal fluorescence imaging and Flow cytometry analysis were performed to evaluate the binding specificity and the receptor binding affinity of SNF-Cy5.5 to OE33. In vivo imaging was performed to evaluate the targeting ability of SNF-Cy5.5 to esophageal carcinoma.

RESULTS

The confocal imaging and flow cytometry analysis showed that SNF-Cy5.5 bound specifically to the plasma membrane of OE33 cells with a high affinity. In vivo, for non-block group, SNF-Cy5.5 probe exhibited rapid OE33 tumor targeting during 24 h p.i. and excellent tumor-to-background contrast at 2 h p.i. For the block group, SNF-Cy5.5 was not observed in the mice after 4 h p.i. Ex vivo imaging also revealed that a higher fluorescent signal intensity value of the tumors was clearly observed in the non-block group than that in the block group (2.6 ± 0.32 × 10⁹ vs. 0.8 ± 0.08 × 10⁹, p < 0.05).

CONCLUSIONS

SNF-Cy5.5 was synthesized and characterized with a high efficiency and purity. The higher affinity, specificity, and tumor targeting efficacy of SNF-Cy5.5 were confirmed by in vitro and in vivo tests. SNF-Cy5.5 is a promising optical probe for the imaging of esophageal adenocarcinoma.

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.

Transferrin receptor 1 targeted optical imaging for identifying glioma margin in mouse models

OBJECTIVE

Optical molecular imaging technology that indiscriminately detects intracranial glioblastoma (GBM) can help neurosurgeons effectively remove tumor masses. Transferrin receptor 1 (TfR 1) is a diagnostic and therapeutic target in GBM. A TfR 1-targeted peptide, CRTIGPSVC (CRT), was shown to cross the blood brain barrier (BBB) and accumulate at high levels in GBM tissues. In this study, we synthesized a TfR 1-targeted near-infrared fluorescent (NIRF) probe, Cy5-CRT, for identifying the GBM tissue margin in mouse models.

METHODS

We initially confirmed the overexpression of TfR 1 in GBM and the tumor-specific homing ability of Cy5-CRT in subcutaneous and orthotopic GBM mouse models. We then examined the feasibility of Cy5-CRT for identifying the tumor margin in orthotopic GBM xenografts. Finally, we compared Cy5-CRT with the clinically used fluorescein sodium in identifying tumor margins.

RESULTS

Cy5-CRT specifically accumulated in GBM tissues and detected the tumor burden with exceptional contrast in mice with orthotopic GBM, enabling fluorescence-guided GBM resection under NIRF live imaging conditions. Importantly, Cy5-CRT recognized the GBM tissue margin more clearly than fluorescein sodium.

CONCLUSIONS

The TfR 1-targeted optical probe Cy5-CRT specifically differentiates tumor tissues from the surrounding normal brain with high sensitivity, indicating its potential application for the precise surgical removal of GBM.

A Uniquely Modified DKL-based Peptide Probe for Positron Emission Tomography Imaging

Peptides containing the asparagine-glycine-arginine (NGR) motif can target the tumor neovascular biomarker CD13/aminopeptidase N receptor. D-K6L9 is a tumor-selective anti-cancer peptide. To improve the capacity of NGR peptides to target tumors, we joined the NGR and D-K6L9 peptides to form NKL. Next, we linked 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to NKL and labeled it with gallium 68 (68Ga, t1/2 = 67.7 min) to form 68Ga-DOTA-NKL. This novel probe was characterized in vitro. 68Ga-DOTA-NKL was stable in phosphate buffered saline at room temperature and in human serum at 37°C. We determined that the uptake rate of 68Ga-DOTA-NKL in CD13 receptor-positive 22Rv1 tumor cells was 3.15% ± 0.04 after 2 h, and tested 68Ga-DOTA-NKL using positron emission tomography (PET)/computed tomography imaging in vivo. MicroPET imaging results revealed that 22Rv1 tumor uptake of 68Ga-DOTA-NKL was 8.69 ± 0.20, 6.61 ± 0.22, 3.85 ± 0.06, and 1.41 ± 0.23 percentage injected dose per gram of tissue (%ID/g) at 0.5, 1, 2, and 3 h postinjection (pi), respectively. The tumor-to-background contrast in the subcutaneous human prostate cancer 22Rv1 mouse model was 9.97 ± 1.90. The 68Ga-DOTA-NKL probe has combined tumor-targeting and tumor-selective properties, and may be used to diagnose CD13-positive tumors.

Aminopeptidase N (CD13): Expression, Prognostic Impact, and Use as Therapeutic Target for Tissue Factor Induced Tumor Vascular Infarction in Soft Tissue Sarcoma

Aminopeptidase N (CD13) is expressed on tumor vasculature and tumor cells. It represents a candidate for targeted therapy, e.g., by truncated tissue factor (tTF)-NGR, binding to CD13, and causing tumor vascular thrombosis. We analyzed CD13 expression by immunohistochemistry in 97 patients with STS who were treated by wide resection and uniform chemo-radio-chemotherapy. Using a semiquantitative score with four intensity levels, CD13 was expressed by tumor vasculature, or tumor cells, or both (composite value, intensity scores 1-3) in 93.9% of the STS. In 49.5% tumor cells, in 48.5% vascular/perivascular cells, and in 58.8%, composite value showed strong intensity score 3 staining. Leiomyosarcoma and synovial sarcoma showed low expression; fibrosarcoma and undifferentiated pleomorphic sarcoma showed high expression. We found a significant prognostic impact of CD13, as high expression in tumor cells or vascular/perivascular cells correlated with better relapse-free survival and overall survival. CD13 retained prognostic significance in multivariable analyses. Systemic tTF-NGR resulted in significant growth reduction of CD13-positive human HT1080 sarcoma cell line xenografts. Our results recommend further investigation of tTF-NGR in STS patients. CD13 might be a suitable predictive biomarker for patient selection.

Molecular Imaging of Aminopeptidase N in Cancer and Angiogenesis

This review focuses on recent advances in the molecular imaging of aminopeptidase N (APN, also known as CD13), a zinc metalloenzyme that cleaves N-terminal neutral amino acids. It is overexpressed in multiple cancer types and also on the surface of vasculature undergoing angiogenesis, making it a promising target for molecular imaging and targeted therapy. Molecular imaging probes for APN are divided into two large subgroups: reactive and nonreactive. The structures of the reactive probes (substrates) contain a reporter group that is cleaved and released by the APN enzyme. The nonreactive probes are not cleaved by the enzyme and contain an antibody, peptide, or nonpeptide for targeting the enzyme exterior or active site. Multivalent homotopic probes utilize multiple copies of the same targeting unit, whereas multivalent heterotopic molecular probes are equipped with different targeting units for different receptors. Several recent preclinical cancer imaging studies have shown that multivalent APN probes exhibit enhanced tumor specificity and accumulation compared to monovalent analogues. The few studies that have evaluated APN-specific probes for imaging angiogenesis have focused on cardiac regeneration. These promising results suggest that APN imaging can be expanded to detect and monitor other diseases that are associated with angiogenesis.

Combinatorial effects of doxorubicin and retargeted tissue factor by intratumoral entrapment of doxorubicin and proapoptotic increase of tumor vascular infarction

Truncated tissue factor (tTF), retargeted to tumor vasculature by GNGRAHA peptide (tTF-NGR), and doxorubicin have therapeutic activity against a variety of tumors. We report on combination experiments of both drugs using different schedules. We have tested fluorescence- and HPLC-based intratumoral pharmacokinetics of doxorubicin, flow cytometry for cellular phosphatidylserine (PS) expression, and tumor xenograft studies for showing in vivo apoptosis, proliferation decrease, and tumor shrinkage upon combination therapy with doxorubicin and induced tumor vascular infarction. tTF-NGR given before doxorubicin inhibits the uptake of the drug into human fibrosarcoma xenografts in vivo. Reverse sequence does not influence the uptake of doxorubicin into tumor, but significantly inhibits the late wash-out phase, thus entrapping doxorubicin in tumor tissue by vascular occlusion. Incubation of endothelial and tumor cells with doxorubicin in vitro increases PS concentrations in the outer layer of the cell membrane as a sign of early apoptosis. Cells expressing increased PS concentrations show comparatively higher procoagulatory efficacy on the basis of equimolar tTF-NGR present in the Factor X assay. Experiments using human M21 melanoma and HT1080 fibrosarcoma xenografts in athymic nude mice indeed show a combinatorial tumor growth inhibition applying doxorubicin and tTF-NGR in sequence over single drug treatment. Combination of cytotoxic drugs such as doxorubicin with tTF-NGR-induced tumor vessel infarction can improve pharmacodynamics of the drugs by new mechanisms, entrapping a cytotoxic molecule inside tumor tissue and reciprocally improving procoagulatory activity of tTF-NGR in the tumor vasculature via apoptosis induction in tumor endothelial and tumor cells.

A case-control study about the association between vascular endothelial growth inhibitor gene polymorphisms and breast cancer risk in female patients in Northeast China

Objective

The inhibition of the neovascularization in tumors is a potential therapeutic target of cancer. Vascular endothelial growth inhibitor (VEGI) is a member of the TNF superfamily which has the ability to suppress the formation of new vessels in tumors. In order to study the association between VEGI gene polymorphisms and breast cancer risk, a case-control study was conducted in Chinese Han women in Northeast China.

Methods

Our study involved 708 female breast cancer patients and 685 healthy volunteers. Four SNPs of VEGI gene were analyzed through the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The association between VEGI gene polymorphisms and breast cancer risk was analyzed in our study. The relation between VEGI gene variants and clinical features of breast cancer including lymph node (LN) metastasis, estrogen receptor (ER), progestrogen receptor (PR), tumor protein 53 (p53), human epidermal growth factor receptor 2 (Her-2) and triple negative (ER-/PR-/Her-2-) status was analyzed as well.

Results

We found that the CT genotype and T allele of rs6478106 were more frequent in patients than in controls. There was also a statistical difference in the distribution of C_rs6478106G_rs4263839 haplotype between patients and controls. In addition, SNP rs6478106 and rs4979462 were related with the Her-2 status.

Conclusions

Our results suggest that VEGI gene variants may be related to the breast cancer risk and the clinical features of breast cancer in Chinese Han women in Northeast China.

Evaluation of (188)Re-labeled NGR-VEGI protein for radioimaging and radiotherapy in mice bearing human fibrosarcoma HT-1080 xenografts

Vascular endothelial growth inhibitor (VEGI) is an anti-angiogenic protein, which includes three isoforms: VEGI-174, VEGI-192, and VEGI-251. The NGR (asparagine-glycine-arginine)-containing peptides can specifically bind to CD13 (Aminopeptidase N) receptor which is overexpressed in angiogenic blood vessels and tumor cells. In this study, a novel NGR-VEGI fusion protein was prepared and labeled with (188)Re for radioimaging and radiotherapy in mice bearing human fibrosarcoma HT-1080 xenografts. Single photon emission computerized tomography (SPECT) imaging results revealed that (188)Re-NGR-VEGI exhibits good tumor-to-background contrast in CD13-positive HT-1080 tumor xenografts. The CD13 specificity of (188)Re-NGR-VEGI was further verified by significant reduction of tumor uptake in HT-1080 tumor xenografts with co-injection of the non-radiolabeled NGR-VEGI protein. The biodistribution results demonstrated good tumor-to-muscle ratio (4.98 ± 0.25) of (188)Re-NGR-VEGI at 24 h, which is consistent with the results from SPECT imaging. For radiotherapy, 18.5 MBq of (188)Re-NGR-VEGI showed excellent tumor inhibition effect in HT-1080 tumor xenografts with no observable toxicity, which was confirmed by the tumor size change and hematoxylin and eosin (H&E) staining of major mouse organs. In conclusion, these data demonstrated that (188)Re-NGR-VEGI has the potential as a theranostic agent for CD13-targeted tumor imaging and therapy.

Tumor Growth Inhibition via Occlusion of Tumor Vasculature Induced by N-Terminally PEGylated Retargeted Tissue Factor tTF-NGR

tTF-NGR retargets the extracellular domain of tissue factor via a C-terminal peptide GNGRAHA, a ligand of the surface protein aminopeptidase N (CD13) and upon deamidation of integrin αvβ3, to tumor vasculature. tTF-NGR induces tumor vascular infarction with consecutive antitumor activity against xenografts and selectively inhibits tumor blood flow in cancer patients. Since random PEGylation resulted in favorable pharmacodynamics of tTF-NGR, we performed site-directed PEGylation of PEG units to the N-terminus of tTF-NGR to further improve the antitumor profile of the molecule. Mono-PEGylation to the N-terminus did not change the procoagulatory activity of the tTF-NGR molecule as measured by Factor X activation. Experiments to characterize pharmacokinetics in mice showed a more than 1 log step higher mean area under the curve of PEG20k-tTF-NGR over tTF-NGR. Acute (24 h) tolerability upon intravenous application for the mono-PEGylated versus non-PEGylated tTF-NGR compounds was comparable. PEG20k-tTF-NGR showed clear antitumor efficacy in vivo against human tumor xenografts when systemically applied. However, site-directed mono-PEGylation to the N-terminus does not unequivocally improve the therapeutic profile of tTF-NGR.