The role of imaging in the clinical development of antiangiogenic agents

Bispecific Antibodies Progression in Malignant Melanoma

The discovery of oncogenes and immune checkpoints has revolutionized the treatment of melanoma in the past 10 years. However, the current PD-L1 checkpoints lack specificity for tumors and target normal cells expressing PD-L1, thus reducing the efficacy on malignant melanoma and increasing the side effects. In addition, the treatment options for primary or secondary drug-resistant melanoma are limited. Bispecific antibodies bind tumor cells and immune cells by simultaneously targeting two antigens, enhancing the anti-tumor targeting effect and cytotoxicity and reducing drug-resistance in malignant melanoma, thus representing an emerging strategy to improve the clinical efficacy. This review focused on the treatment of malignant melanoma by bispecific antibodies and summarized the effective results of the experiments that have been conducted, also discussing the different aspects of these therapies. The role of the melanoma epitopes, immune cell activation, cell death and cytotoxicity induced by bispecific antibodies were evaluated in the clinical or preclinical stage, as these therapies appear to be the most suitable in the treatment of malignant melanoma.

Local extraction and detection of early stage breast cancers through a microneedle and nano-Ag/MBL film based painless and blood-free strategy

Early diagnosis is the key to the good prognosis of breast cancer. At present, clinical tumor diagnosis is mainly through serum analysis, which is painful and can only detect relatively advanced tumors that have already metastasized from the glands into the blood circulation. Here, we developed an earlier diagnostic method (before tumor cells entering the blood) of breast cancers through a convenient and painless process with blood-free samples. The microneedles were utilized to insert into the animals' testing areas, while the tissue fluid was collected through our synthesized breathable thin film. The obtained tissue fluid sample was then incubated to form blue products. In the area where tumors occurred, the blue changes were more obvious than the healthy area, a semi-localization and semi-quantitative detection of the tumorous area thus could be realized. The results of corresponding animal experiments showed that, after the injection of tumor cells, the proposed nano-Ag based colorimetric method can detect the occurrence of breast cancers in 7 days. What is more, these early tumors could be effectively suppressed through classical DOX treatment. For comparison, the classical blood test needed 14 days to validate the occurrence of breast cancers. The subsequent human tests further demonstrated the feasibility of the present method. The development of this work could provide a more convenient, accurate and comfortable technology to support for the early screening and diagnosis of cancer patients, so as to fundamentally reduce the mortality of the breast cancers.

The Effect of Sunitinib Treatment in Human Melanoma Xenografts: Associations with Angiogenic Profiles

The effect of antiangiogenic agents targeting the vascular endothelial growth factor A (VEGF-A) pathway has been reported to vary substantially in preclinical studies. The purpose of this study was to investigate the effect of sunitinib treatment on tumor vasculature and oxygenation in melanoma xenografts with different angiogenic profiles. A-07, U-25, D-12, or R-18 melanoma xenografts were grown in dorsal window chambers and given daily treatments of sunitinib (40 mg/kg) or vehicle. Morphologic parameters of tumor vascular networks were assessed from high-resolution transillumination images, and tumor blood supply times (BSTs) were assessed from first-pass imaging movies. Tumor hypoxia was assessed with immunohistochemistry by using pimonidazole as hypoxia marker, and the gene expression and the protein secretion rate of angiogenic factors were assessed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The melanoma lines differed substantially in the expression of VEGF-A, VEGF-C, and platelet-derived growth factor A. Sunitinib treatment reduced vessel densities and induced hypoxia in all melanoma lines, and the magnitude of the effect was associated with the gene expression and protein secretion rate of VEGF-A. Sunitinib treatment also increased vessel segment lengths, reduced the number of small-diameter vessels, and inhibited growth-induced increases in the diameter of surviving vessels but did not change BST. In conclusion, sunitinib treatment did not improve vascular function but reduced vessel density and induced hypoxia in human melanoma xenografts. The magnitude of the treatment-induced effect was associated with the VEGF-A expression of the melanoma lines.

Early effects of low dose bevacizumab treatment assessed by magnetic resonance imaging

Background

Antiangiogenic treatments have been shown to increase blood perfusion and oxygenation in some experimental tumors, and to reduce blood perfusion and induce hypoxia in others. The purpose of this preclinical study was to investigate the potential of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted MRI (DW-MRI) in assessing early effects of low dose bevacizumab treatment, and to investigate intratumor heterogeneity in this effect.

Methods

A-07 and R-18 human melanoma xenografts, showing high and low expression of VEGF-A, respectively, were used as tumor models. Untreated and bevacizumab-treated tumors were subjected to DCE-MRI and DW-MRI before treatment, and twice during a 7-days treatment period. Tumor images of K^trans (the volume transfer constant of Gd-DOTA) and v_e (the fractional distribution volume of Gd-DOTA) were produced by pharmacokinetic analysis of the DCE-MRI data, and tumor images of ADC (the apparent diffusion coefficient) were produced from DW-MRI data.

Results

Untreated A-07 tumors showed higher K^trans, v_e, and ADC values than untreated R-18 tumors. Untreated tumors showed radial heterogeneity in K^trans, i.e., K^trans was low in central tumor regions and increased gradually towards the tumor periphery. After the treatment, bevacizumab-treated A-07 tumors showed lower K^trans values than untreated A-07 tumors. Peripherial tumor regions showed substantial reductions in K^trans, whereas little or no effect was seen in central regions. Consequently, the treatment altered the radial heterogeneity in K^trans. In R-18 tumors, significant changes in K^trans were not observed. Treatment induced changes in tumor size, v_e, and ADC were not seen in any of the tumor lines.

Conclusions

Early effects of low dose bevacizumab treatment may be highly heterogeneous within tumors and can be detected with DCE-MRI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1918-1) contains supplementary material, which is available to authorized users.

Application of a compact magnetic resonance imaging system for toxicologic pathology: evaluation of lithium-pilocarpine-induced rat brain lesions

Magnetic resonance imaging (MRI) is a useful noninvasive tool used to detect lesions in clinical and veterinary medicine. The present study evaluated the suitability of a new easy-to-use compact MRI platform (M2 permanent magnet system, Aspect Imaging, Shoham, Israel) for assisting with preclinical toxicologic pathology examination of lesions in the rat brain. In order to induce brain lesions, male Sprague-Dawley rats were treated once with lithium chloride (127 mg/kg, intraperitoneal [i.p.]) followed by pilocarpine (30 mg/kg, i.p.). One week after dosing, the perfused, fixed brains were collected, analyzed by the MRI system and examined histopathologically. MRI of the brain of treated rats revealed areas of high T1 and middle to low T2 signals, when compared with the controls, in the piriform cortex, lateral thalamic nucleus, posterior paraventricular thalamic nucleus and posterior hypothalamic nucleus of the cerebrum. The altered MRI signal areas were consistent with well-circumscribed foci of neuronal cell degeneration/necrosis accompanied by glial cell proliferation. The present data demonstrated that quick analysis of fixed organs by the MRI system can detect the presence and location of toxicologic lesions and provide useful temporal information for selection of appropriate sections for histopathologic examination before routine slide preparation, especially in complex and functionally heterogeneous organs such as the brain.

Practical Applications of in Vivo and ex Vivo MRI in Toxicologic Pathology Using a Novel High-performance Compact MRI System

Magnetic resonance imaging (MRI) is widely used in preclinical research and drug development and is a powerful noninvasive method for assessment of phenotypes and therapeutic efficacy in murine models of disease. In vivo MRI provides an opportunity for longitudinal evaluation of tissue changes and phenotypic expression in experimental animal models. Ex vivo MRI of fixed samples permits a thorough examination of multiple digital slices while leaving the specimen intact for subsequent conventional hematoxylin and eosin (H&E) histology. With the advent of new compact MRI systems that are designed to operate in most conventional labs without the cost, complexity, and infrastructure needs of conventional MRI systems, the possibility of MRI becoming a practical modality is now viable. The purpose of this study was to investigate the capabilities of a new compact, high-performance MRI platform (M2™; Aspect Imaging, Israel) as it relates to preclinical toxicology studies. This overview will provide examples of major organ system pathologies with an emphasis on how compact MRI can serve as an important adjunct to conventional pathology by nondestructively providing 3-dimensional (3-D) digital data sets, detailed morphological insights, and quantitative information. Comparative data using compact MRI for both in vivo and ex vivo are provided as well as validation using conventional H&E.

Magnetic resonance imaging identifies early effects of sunitinib treatment in human melanoma xenografts

BACKGROUND

Antiangiogenic treatment may change the tumor microenvironment and hence influence the effect of conventional therapies. The potential of diffusion weighted magnetic resonance imaging (DW-MRI) and dynamic contrast enhanced MRI (DCE-MRI) in assessing microenvironmental effects of sunitinib treatment was investigated in this preclinical study.

METHODS

Sunitinib-treated and untreated A-07 tumors were subjected to DW-MRI and DCE-MRI, and parametric images of ADC and Ktrans were produced. Microvascular density, hypoxic fraction, and necrotic fraction were assessed from immunohistochemical preparations, and tumor interstitial fluid pressure (IFP) was assessed with probe measurement.

RESULTS

Sunitinib-treated tumors showed reduced microvascular density, increased hypoxic fraction, increased necrotic fraction, increased ADC, and reduced Ktrans, but did not differ from untreated tumors in growth rate and IFP.

CONCLUSIONS

Sunitinib treatment affected the tumor microenvironment without affecting tumor size. DW-MRI and DCE-MRI were sensitive to the sunitinib-induced changes in the tumor microenvironment.

Sunitinib treatment does not improve blood supply but induces hypoxia in human melanoma xenografts

Background

Antiangiogenic agents that disrupt the vascular endothelial growth factor pathway have been demonstrated to normalize tumor vasculature and improve tumor oxygenation in some studies and to induce hypoxia in others. The aim of this preclinical study was to investigate the effect of sunitinib treatment on the morphology and function of tumor vasculature and on tumor oxygenation.

Methods

A-07-GFP and R-18-GFP human melanoma xenografts grown in dorsal window chambers were used as preclinical tumor models. Morphologic parameters of tumor vascular networks were assessed from high-resolution transillumination images, and tumor blood supply time was assessed from first-pass imaging movies recorded after a bolus of 155 kDa tetramethylrhodamine isothiocyanate-labeled dextran had been administered intravenously. Tumor hypoxia was assessed from immunohistochemical preparations of the imaged tissue by use of pimonidazole as a hypoxia marker.

Results

Sunitinib treatment reduced vessel densities, increased vessel segment lengths, did not affect blood supply times, and increased hypoxic area fractions.

Conclusion

Sunitinib treatment did not improve vascular function but induced hypoxia in A-07-GFP and R-18-GFP tumors.

Novel molecular imaging platform for monitoring oncological kinases

Recent advances in oncology have lead to identification of a plethora of alterations in signaling pathways that are critical to oncogenesis and propagation of malignancy. Among the biomarkers identified, dysregulated kinases and associated changes in signaling cascade received the lion's share of scientific attention and have been under extensive investigations with goal of targeting them for anti-cancer therapy. Discovery of new drugs is immensely facilitated by molecular imaging technology which enables non-invasive, real time, dynamic imaging and quantification of kinase activity. Here, we review recent development of novel kinase reporters based on conformation dependent complementation of firefly luciferase to monitor kinase activity. Such reporter system provides unique insights into the pharmacokinetics and pharmacodynamics of drugs that modulate kinase signaling and have a huge potential in drug discovery, validation, and drug-target interactions.

Preclinical evaluation of tumor microvascular response to a novel antiangiogenic/antitumor agent RO0281501 by dynamic contrast-enhanced MRI at 1.5 T

Inhibition of tumor angiogenesis is a promising approach in cancer treatment. The purpose of this study was to evaluate the vascular response of human lung tumor xenografts in vivo to RO0281501, an inhibitor of tyrosine kinase receptors, including vascular endothelial growth factor receptor 2, fibroblast growth factor receptor, and platelet-derived growth factor receptor, using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Human non-small cell lung carcinoma (H460a) xenografts grown s.c. in athymic nu/nu mice were treated p.o. with the antiangiogenic agent RO0281501. Treatment-induced changes in tumor volume, epiphyseal growth plate thickness, and microvessel density assessed by CD31 immunohistochemistry were analyzed. Tumor vascular permeability and perfusion were measured in tumors using DCE-MRI with gadopentetate dimeglumine on a 1.5 T clinical scanner to assess vascular function. Treatment with RO0281501 resulted in significant growth retardation of H460a tumors. RO0281501-treated tumors showed histologic evidence of growth plate thickening and relatively lower microvessel density compared with the controls. Regarding DCE-MRI variables, the initial slope of contrast uptake and Ak(ep) were significantly decreased on day 7 of treatment. RO0281501 is a novel antiangiogenic/antitumor agent, which is active in the H460a xenograft model. Its effects on tumor vasculature can be monitored and assessed by DCE-MRI on a 1.5 T human MR scanner with clinically available gadopentetate dimeglumine contrast, which will facilitate clinical trials with this or similar agents.

A simple, reproducible method for monitoring the treatment of tumours using dynamic contrast-enhanced MR imaging

Dynamic contrast-enhanced MR imaging (DCE-MRI) may act as a biomarker for successful cancer therapy. Simple, reproducible techniques may widen this application. This paper demonstrates a single slice imaging technique. The image acquisition is performed in less than 500 ms making it relatively insensitive to respiratory motion. Data from phantom studies and a reproducibility study in solid human tumours are presented. The reproducibility study showed a coefficient of variation (CoV) of 19.1% for K^trans and 15.8% for the initial area under the contrast enhancement curve (IAUC). This was improved to 16 and 13.9% if tumours of diameter less than 3 cm were excluded. The individual repeatability (the range within which individual measurements are expected to fall) was 30.6% for K^trans and 26.5% for IAUC for tumours greater than 3 cm diameter. This approach to DCE–MRI image acquisition can be performed with standard clinical scanners, and data analysis is straightforward. For treatment trials with 10 patients in a cohort, the CoV implies that the method would be sensitive to a treatment effect of greater than 18%. The individual repeatability is well inside the 40% change shown to be important in clinical studies using this DCE–MRI technique.