Tumor angiogenesis: methods to analyze tumor vasculature and vessel normalization in mouse models of cancer

Superparamagnetic Iron Oxide Nanoparticles Carrying Chemotherapeutics Improve Drug Efficacy in Monolayer and Spheroid Cell Culture by Enabling Active Accumulation

Cytotoxic and cytostatic chemotherapeutics act by attacking rapidly dividing tumor cells, predominantly affecting malignant tissue and to a certain degree preserving healthy cells. Nonetheless, severe side effects are caused as quickly proliferating healthy cells such as hematopoietic precursors and mucous membranes are impaired as well. This limits the administered dose and eventually allows tumor cells to escape treatment. In order to increase intratumoral drug concentration and simultaneously reduce systemic side effects, nanoparticles have come into focus as drug carriers. The functionalization of superparamagnetic iron oxide nanoparticles (SPIONs) with chemotherapeutics such as mitoxantrone (MTO) enables targeted drug transport by using magnetic forces. Here, we investigate SPIONs consisting of individual iron oxide cores of 10 nm in diameter and a total hydrodynamic diameter of 53 ± 0.8 nm as a transporting system for MTO. Comparing the killing efficacy in monolayer cell culture and multicellular tumor spheroids of HT-29 cells, we show that spheroids tolerate considerably higher doses of nanoparticle-loaded MTO. Therefore, dose predictions from conventional monolayer cell cultures are often misleading for in vivo applications. This was true for both soluble and nanoparticle-bound MTO. Using flow chambers mimicking in vivo blood flow, we furthermore demonstrate that SPIONs can magnetically accumulate MTO. We conclude that SPIONs can function as an effective delivery platform to increase local drug concentrations, thereby potentially overcoming chemotherapy resistance of cells.

Dual inhibition of PFKFB3 and VEGF normalizes tumor vasculature, reduces lactate production, and improves chemotherapy in glioblastoma: insights from protein expression profiling and MRI

Rationale: Tumor vascular normalization (TVN) is emerging to enhance the efficacy of anticancer treatment in many cancers including glioblastoma (GBM). However, a common and severe challenge being currently faced is the transient TVN effect, hampering the sustained administration of anticancer therapy during TVN window. Additionally, the lack of non-contrast agent-based imaging biomarkers to monitor TVN process postpones the clinical translation of TVN strategy. In this study, we investigated whether dual inhibition of VEGF and the glycolytic activator PFKFB3 could reinforce the TVN effect in GBM. Dynamic contrast-enhanced-magnetic resonance imaging (DCE-MRI) and intravoxel incoherent motion (IVIM)-MRI were performed to monitor TVN process and to identify whether IVIM-MRI is a candidate or complementary imaging biomarker for monitoring TVN window without exogenous contrast agent administration. Methods: Patient-derived orthotopic GBM xenografts in mice were established and treated with bevacizumab (BEV), 3PO (PFKFB3 inhibitor), BEV+3PO dual therapy, or saline. The vascular morphology, tumor hypoxia, and lactate level were evaluated before and at different time points after treatments. Doxorubicin was used to evaluate chemotherapeutic efficacy and drug delivery. Microarray of angiogenesis cytokines and western blotting were conducted to characterize post-treatment molecular profiling. TVN process was monitored by DCE- and IVIM-MRI. Correlation analysis of pathological indicators and MRI parameters was further analyzed. Results: Dual therapy extended survival and delayed tumor growth over each therapy alone, concomitant with a decrease of cell proliferation and an increase of cell apoptosis. The dual therapy reinforces TVN effect, thereby alleviating tumor hypoxia, reducing lactate production, and improving the efficacy and delivery of doxorubicin. Mechanistically, several angiogenic cytokines and pathways were downregulated after dual therapy. Notably, dual therapy inhibited Tie1 expression, the key regulator of TVN, in both endothelial cells and tumor cells. DCE- and IVIM-MRI data showed that dual therapy induced a more homogenous and prominent TVN effect characterized by improved vascular function in tumor core and tumor rim. Correlation analysis revealed that IVIM-MRI parameter D* had better correlations with TVN pathological indicators compared with the DCE-MRI parameter Ktrans. Conclusions: Our results propose a rationale to overcome the current limitation of BEV monotherapy by integrating the synergistic effects of VEGF and PFKFB3 blockade to enhance chemotherapy efficacy through a sustained TVN effect. Moreover, we unveil IVIM-MRI parameter D* has much potential as a complementary imaging biomarker to monitor TVN window more precisely without exogenous contrast agent injection.

Morphometric analysis of the branching of the vascular tree in the chick embryo area vasculosa

The chick embryo includes the area vasculosa is subdivided into 2 concentric zones, the inner transparent area pellucida vasculosa and the surrounding less transparent area opaca vasculosa, peripherally limited by the sinus terminalis. In this study, we have analyzed by a modern morphometric approach the total length of the vascular network, the number of vascular branches, of the branching points density, the modality of vessel ramification, and spatial arrangement of the vascular network in four consecutive stages of development of the area vasculosa. The results have shown that there is a significant 15% increase in the total length of the vascular network associated with a progressive increase of the number of vascular branches and of the branching points density. Moreover, the results indicated that vascular spatial disorder significantly decreased during development in area vasculosa, suggesting a more uniform occupancy of the tissue by the vascular pattern. Finally, a more regular pattern of branching was observed, as indicated by the significant decrease of topological disorder of the vascular tree.

Tumor vasculature remolding by thalidomide increases delivery and efficacy of cisplatin

Background

A promising strategy to overcome the chemoresistance is the tumor blood vessel normalization, which restores the physiological perfusion and oxygenation of tumor vasculature. Thalidomide (Thal) has been shown to increase the anti-tumor effect of chemotherapy agents in solid tumors. However, it is not yet known whether the synergistic effect of Thal combined with other cytotoxic drugs is attributable to tumor vascular normalization.

Methods

We used two homograft mice models (4 T1 breast tumor model and CT26 colorectal tumor model) to investigate the effect of Thal on tumor growth, microvessel density, vascular physiology, vascular maturity and function, drug delivery and chemosensitivity. Immunofluorescence, immunohistochemistry and scanning electron microscopy were performed to determine the vessel changes. Protein array assay, qPCR and western blotting were used to detect the molecular mechanism by which Thal regulates tumor vascular.

Results

Here we report that Thal potently suppressed tumor growth, angiogenesis, hypoxia, and vascular permeability in animal models. Thal also induced a regular monolayer of endothelial cells in tumor vessels, inhibiting vascular instability, and normalized tumor vessels by increasing vascular maturity, pericyte coverage and endothelial junctions. The tumor vessel stabilization effect of Thal resulted in a decrease in tumor vessel tortuosity and leakage, and increased vessel thickness and tumor perfusion. Eventually, the delivery of cisplatin was highly enhanced through the normalized tumor vasculature, thus resulting in profound anti-tumor and anti-metastatic effects. Mechanistically, the effects of Thal on tumor vessels were caused in part by its capability to correct the imbalance between pro-angiogenic factors and anti-angiogenic factors.

Conclusions

Our findings provide direct evidence that Thal remodels the abnormal tumor vessel system into a normalized vasculature. Our results may lay solid foundation for the development of Thal as a novel candidate agent to maximize the therapeutic efficacy of chemotherapeutic drugs for solid tumors.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1366-x) contains supplementary material, which is available to authorized users.

Dual Inhibition of Angiopoietin-TIE2 and MET Alters the Tumor Microenvironment and Prolongs Survival in a Metastatic Model of Renal Cell Carcinoma

Receptor tyrosine kinase inhibitors have shown clinical benefit in clear cell renal cell carcinoma (ccRCC), but novel therapeutic strategies are needed. The angiopoietin/Tie2 and MET pathways have been implicated in tumor angiogenesis, metastases, and macrophage infiltration. In our study, we used trebananib, an angiopoietin 1/2 inhibitor, and a novel small-molecule MET kinase inhibitor in patient-derived xenograft (PDX) models of ccRCC. Our goal was to assess the ability of these compounds to alter the status of tumor-infiltrating macrophages, inhibit tumor growth and metastases, and prolong survival. Seven-week-old SCID mice were implanted subcutaneously or orthotopically with human ccRCC models. One month postimplantation, mice were treated with angiopoietin 1/2 inhibitor trebananib (AMG 386), MET kinase inhibitor, or combination. In our metastatic ccRCC PDX model, RP-R-02LM, trebananib alone, and in combination with a MET kinase inhibitor, significantly reduced lung metastases and M2 macrophage infiltration (P = 0.0075 and P = 0.0205, respectively). Survival studies revealed that treatment of the orthotopically implanted RP-R-02LM tumors yielded a significant increase in survival in both trebananib and combination groups. In addition, resection of the subcutaneously implanted primary tumor allowed for a significant survival advantage to the combination group compared with vehicle and both single-agent groups. Our results show that the combination of trebananib with a MET kinase inhibitor significantly inhibits the spread of metastases, reduces infiltrating M2-type macrophages, and prolongs survival in our highly metastatic ccRCC PDX model, suggesting a potential use for this combination therapy in treating patients with ccRCC.

Chondromodulin‑I suppresses tumorigenesis of human osteosarcoma cells

Osteosarcoma is the most common type of bone cancer, and accounts for ~3% of cancers that occurring in children. Chondromodulin‑I (ChM-I) is a 25 kDa glycoprotein that is expressed mainly in cartilage. ChM-I demonstrates anti‑angiogenic activity and has been suggested to inhibit endothelial cells from invading cartilage, and then has been shown to be an inhibitor of tumorigenesis. However, it remains unclear if ChM‑I has any direct anti‑tumorigenesis role on osteosarcoma. Therefore, the present study aimed to identify whether ChM‑I has any direct inhibit effect on human osteosarcoma cells. A bromodeoxyuridine incorporation assay was performed on the Saos‑2 human osteosarcoma cell line treated with or without recombinant human ChM‑I, to evaluate its impact on DNA synthesis. An adenovirus carrier for the expression of ChM‑I was constructed and transfected into tumor cells in vitro to evaluate the effect of ChM‑I on tumor cells. Additionally, ChM‑I was knocked down by using small interfering RNA to downregulate the expression of ChM‑I. Cell invasion, migration and cell‑colony formation assays, and xenograft tumor experiments were performed to evaluate the effects of ChM‑I on tumor cells in vitro and in vivo. The results demonstrated that ChM‑I could suppress DNA synthesis of human osteosarcoma cells, and it also exerted an inhibitory effect on the proliferation and colony formation abilities of human osteosarcoma cells. In addition, ChM‑I inhibited cell invasion and migration in vitro and suppressed osteosarcoma cell growth significantly in vivo. In conclusion, ChM‑I directly suppressed the proliferation and growth of osteosarcoma cells in an anchorage‑independent manner, and may therefore be a promising drug for the treatment of osteosarcoma.

Lenalidomide normalizes tumor vessels in colorectal cancer improving chemotherapy activity

Background

Angiogenesis inhibition is a promising approach for treating metastatic colorectal cancer (mCRC). Recent evidences support the seemingly counterintuitive ability of certain antiangiogenic drugs to promote normalization of residual tumor vessels with important clinical implications. Lenalidomide is an oral drug with immune-modulatory and anti-angiogenic activity against selected hematologic malignancies but as yet little is known regarding its effectiveness for solid tumors. The aim of this study was to determine whether lenalidomide can normalize colorectal cancer neo-vessels in vivo, thus reducing tumor hypoxia and improving the benefit of chemotherapy.

Methods

We set up a tumorgraft model with NOD/SCID mice implanted with a patient-derived colorectal cancer liver metastasis. The mice were treated with oral lenalidomide (50 mg/Kg/day for 28 days), intraperitoneal 5-fluorouracil (5FU) (20 mg/Kg twice weekly for 3 weeks), combination (combo) of lenalidomide and 5FU or irrelevant vehicle. We assessed tumor vessel density (CD146), pericyte coverage (NG2; alphaSMA), in vivo perfusion capability of residual vessels (lectin distribution essay), hypoxic areas (HP2-100 Hypoxyprobe) and antitumor activity in vivo and in vitro.

Results

Treatment with lenalidomide reduced tumor vessel density (p = 0.0001) and enhanced mature pericyte coverage of residual vessels (p = 0.002). Perfusion capability of tumor vessels was enhanced in mice treated with lenalidomide compared to controls (p = 0.004). Accordingly, lenalidomide reduced hypoxic tumor areas (p = 0.002) and enhanced the antitumor activity of 5FU in vivo. The combo treatment delayed tumor growth (p = 0.01) and significantly reduced the Ki67 index (p = 0.0002). Lenalidomide alone did not demonstrate antitumor activity compared to untreated controls in vivo or against 4 different mCRC cell lines in vitro.

Conclusions

We provide the first evidence of tumor vessel normalization and hypoxia reduction induced by lenalidomide in mCRC in vivo. This effect, seemingly counterintuitive for an antiangiogenic compound, translates into indirect antitumor activity thus enhancing the therapeutic index of chemotherapy. Our findings suggest that further research should be carried out on synergism between lenalidomide and conventional therapies for treating solid tumors that might benefit from tumor vasculature normalization.