Dynamic PET evaluation of elevated FLT level after sorafenib treatment in mice bearing human renal cell carcinoma xenograft

Non-invasive molecular imaging of kidney diseases

In nephrology, differential diagnosis or assessment of disease activity largely relies on the analysis of glomerular filtration rate, urinary sediment, proteinuria and tissue obtained through invasive kidney biopsies. However, currently available non-invasive functional parameters, and most serum and urine biomarkers, cannot capture intrarenal molecular disease processes specifically. Moreover, although histopathological analyses of kidney biopsy samples enable the visualization of pathological morphological and molecular alterations, they only provide information about a small part of the kidney and do not allow longitudinal monitoring. These limitations not only hinder understanding of the dynamics of specific disease processes in the kidney, but also limit the targeting of treatments to active phases of disease and the development of novel targeted therapies. Molecular imaging enables non-invasive and quantitative assessment of physiological or pathological processes by combining imaging technologies with specific molecular probes. Here, we discuss current preclinical and clinical molecular imaging approaches in nephrology. Non-invasive visualization of the kidneys through molecular imaging can be used to detect and longitudinally monitor disease activity and can therefore provide companion diagnostics to guide clinical trials, as well as the safe and effective use of drugs.

Eribulin improves tumor oxygenation demonstrated by 18F-DiFA hypoxia imaging, leading to radio-sensitization in human cancer xenograft models

PURPOSE

Eribulin, an inhibitor of microtubule dynamics, is known to show antitumor effects through its remodeling activity in the tumor vasculature. However, the extent to which the improvement of tumor hypoxia by eribulin affects radio-sensitivity remains unclear. We utilized 1-(2,2-dihydroxymethyl-3-¹⁸F-fluoropropyl)-2-nitroimidazole (¹⁸F-DiFA), a new PET probe for hypoxia, to investigate the effects of eribulin on tumor hypoxia and evaluate the radio-sensitivity during eribulin treatment.

METHODS

Mice bearing human breast cancer MDA-MB-231 cells or human lung cancer NCI-H1975 cells were administered a single dose of eribulin. After administration, mice were injected with ¹⁸F-DiFA and pimonidazole, and tumor hypoxia regions were analyzed. For the group that received combined treatment with radiation, ¹⁸F-DiFA PET/CT imaging was performed before tumors were locally X-irradiated. Tumor size was measured every other day after irradiation.

RESULTS

Eribulin significantly reduced ¹⁸F-DiFA accumulation levels in a dose-dependent manner. Furthermore, the reduction in ¹⁸F-DiFA accumulation levels by eribulin was most significant 7 days after treatment. These results were also supported by reduction of the pimonidazole-positive hypoxic region. The combined treatment showed significant retardation of tumor growth in comparison with the control, radiation-alone, and drug-alone groups. Importantly, tumor growth after irradiation was inversely correlated with ¹⁸F-DiFA accumulation.

CONCLUSION

These results demonstrated that ¹⁸F-DiFA PET/CT clearly detected eribulin-induced tumor oxygenation and that eribulin efficiently enhanced the antitumor activity of radiation by improving tumor oxygenation.

Choosing The Right Animal Model for Renal Cancer Research

The increase in the life expectancy of patients with renal cell carcinoma (RCC) in the last decade is due to changes that have occurred in the area of preclinical studies. Understanding cancer pathophysiology and the emergence of new therapeutic options, including immunotherapy, would not be possible without proper research. Before new approaches to disease treatment are developed and introduced into clinical practice they must be preceded by preclinical tests, in which animal studies play a significant role. This review describes the progress in animal model development in kidney cancer research starting from the oldest syngeneic or chemically-induced models, through genetically modified mice, finally to xenograft, especially patient-derived, avatar and humanized mouse models. As there are a number of subtypes of RCC, our aim is to help to choose the right animal model for a particular kidney cancer subtype. The data on genetic backgrounds, biochemical parameters, histology, different stages of carcinogenesis and metastasis in various animal models of RCC as well as their translational relevance are summarized. Moreover, we shed some light on imaging methods, which can help define tumor microstructure, assist in the analysis of its metabolic changes and track metastasis development.

Elimination of tumor hypoxia by eribulin demonstrated by 18F-FMISO hypoxia imaging in human tumor xenograft models

BACKGROUND

Eribulin, an inhibitor of microtubule dynamics, shows antitumor potency against a variety of solid cancers through its antivascular activity and remodeling of tumor vasculature. ¹⁸F-Fluoromisonidazole (¹⁸F-FMISO) is the most widely used PET probe for imaging tumor hypoxia. In this study, we utilized ¹⁸F-FMISO to clarify the effects of eribulin on the tumor hypoxic condition in comparison with histological findings.

MATERIAL AND METHODS

Mice bearing a human cancer cell xenograft were intraperitoneally administered a single dose of eribulin (0.3 or 1.0 mg/kg) or saline. Three days after the treatment, mice were injected with ¹⁸F-FMISO and pimonidazole (hypoxia marker for immunohistochemistry), and intertumoral ¹⁸F-FMISO accumulation levels and histological characteristics were determined. PET/CT was performed pre- and post-treatment with eribulin (0.3 mg/kg, i.p.).

RESULTS

The ¹⁸F-FMISO accumulation levels and percent pimonidazole-positive hypoxic area were significantly lower, whereas the number of microvessels was higher in the tumors treated with eribulin. The PET/CT confirmed that ¹⁸F-FMISO distribution in the tumor was decreased after the eribulin treatment.

CONCLUSIONS

Using ¹⁸F-FMISO, we demonstrated the elimination of the tumor hypoxic condition by eribulin treatment, concomitantly with the increase in microvessel density. These findings indicate that PET imaging using ¹⁸F-FMISO may provide the possibility to detect the early treatment response in clinical patients undergoing eribulin treatment.

Assessment of glucose metabolism and cellular proliferation in multiple myeloma: a first report on combined 18F-FDG and 18F-FLT PET/CT imaging

Background

Despite the significant upgrading in recent years of the role of ¹⁸F-FDG PET/CT in multiple myeloma (MM) diagnostics, there is a still unmet need for myeloma-specific radiotracers. 3′-Deoxy-3′-[¹⁸F]fluorothymidine (¹⁸F-FLT) is the most studied cellular proliferation PET agent, considered a potentially new myeloma functional imaging tracer. The aim of this pilot study was to evaluate ¹⁸F-FLT PET/CT in imaging of MM patients, in the context of its combined use with ¹⁸F-FDG PET/CT.

Results

Eight patients, four suffering from symptomatic MM and four suffering from smoldering MM (SMM), were enrolled in the study. All patients underwent ¹⁸F-FDG PET/CT and ¹⁸F-FLT PET/CT imaging by means of static (whole body) and dynamic PET/CT of the lower abdomen and pelvis (dPET/CT) in two consecutive days. The evaluation of PET/CT studies was based on qualitative evaluation, semi-quantitative (SUV) calculation, and quantitative analysis based on two-tissue compartment modeling. ¹⁸F-FDG PET/CT demonstrated focal, ¹⁸F-FDG avid, MM-indicative bone marrow lesions in five patients. In contrary, ¹⁸F-FLT PET/CT showed focal, ¹⁸F-FLT avid, myeloma-indicative lesions in only two patients. In total, 48 ¹⁸F-FDG avid, focal, MM-indicative lesions were detected with ¹⁸F-FDG PET/CT, while 17 ¹⁸F-FLT avid, focal, MM-indicative lesions were detected with ¹⁸F-FLT PET/CT. The number of myeloma-indicative lesions was significantly higher for ¹⁸F-FDG PET/CT than for ¹⁸F-FLT PET/CT. A common finding was a mismatch of focally increased ¹⁸F-FDG uptake and reduced ¹⁸F-FLT uptake (lower than the surrounding bone marrow). Moreover, ¹⁸F-FLT PET/CT was characterized by high background activity in the bone marrow compartment, further complicating the evaluation of bone marrow lesions. Semi-quantitative evaluation revealed that both SUV_mean and SUV_max were significantly higher for ¹⁸F-FLT than for ¹⁸F-FDG in both MM lesions and reference tissue. SUV values were higher in MM lesions than in reference bone marrow for both tracers.

Conclusions

Despite the limited number of patients analyzed in this pilot study, the first results of the trial indicate that ¹⁸F-FLT does not seem suitable as a single tracer in MM diagnostics. Further studies with a larger patient population are warranted to generalize the herein presented results.

Electronic supplementary material

The online version of this article (10.1186/s13550-018-0383-7) contains supplementary material, which is available to authorized users.

Establishment of a bioluminescent Renca cell line for renal carcinoma research

PURPOSE

Luciferase modification of tumour cells enables early and non-invasive imaging to detect tumour growth in situ and could provide sensitive and effective detection of carcinoma during research and therapy.

METHODS

Renca cells, a murine renal carcinoma cell line, were infected with lentivirus expressing luciferase to obtain Renca-luc. The proliferation, invasion, and migration of Renca and Renca-luc cell lines were compared using colorimetric, Boyden chamber, and wound-healing assays. Orthotopic tumour models were established in BALB/c mice using Renca and Renca-luc cells, and tumour growth in vivo was detected using bioluminescence imaging and magnetic resonance imaging (MRI).

RESULTS

Intensity of luciferase signals from Renca-luc was positively correlated with cell number. Bioluminescence signal was detected 1 day after the establishment of the renal carcinoma model using Renca-luc and was significantly increased after 7 days. Tumour size at 7 days following the establishment of renal carcinoma models using Renca and Renca-luc was determined using MRI. The presence of renal model tumours was confirmed by histological staining. The expression of luciferase did not affect Renca cell characteristics in vitro or tumour growth in vivo.

CONCLUSION

Luciferase labelling could provide a sensitive and non-invasive evaluation method for immunological and tumour therapy of renal carcinomas.