Assessment of 213Bi-anti-EGFR-MAb treatment response in malignant cancer cells

Evaluation of response to treatment is among the major challenges in oncology. Using a targeted therapy approach with an alpha-particle emitting radionuclide we investigated two different tumor cell lines with regard to alterations in glycolysis as measure of therapy response. Hereby, in vitro assays represent a valuable tool to provide necessary information about therapeutic efficacy.JRC.G.I.5-Advanced Nuclear Knowledg

Assessment of 213Bi-anti-EGFR MAb treatment efficacy in malignant cancer cells with [1-13C]pyruvate and [18F]FDG

Evaluation of response to therapy is among the key objectives of oncology. A new method to evaluate this response includes magnetic resonance spectroscopy (MRS) with hyperpolarized 13C-labelled metabolites, which holds promise to provide new insights in terms of both therapeutic efficacy and tumor cell metabolism. Human EJ28Luc urothelial carcinoma and LN18 glioma cells were treated with lethal activity concentrations of a 213Bi-anti-EGFR immunoconjugate. Treatment efficacy was controlled via analysis of DNA double-strand breaks (immunofluorescence γH2AX staining) and clonogenic survival of cells. To investigate changes in metabolism of treated cells vs controls we analyzed conversion of hyperpolarized [1-13C]pyruvate to [1-13C]lactate via MRS as well as viability of cells, lactate formation and lactate dehydrogenase activity in the cellular supernatants and [18F]FDG uptake in treated cells vs controls, respectively. Treatment of malignant cancer cells with 213Bi-anti-EGFR-MAb induced intense DNA double-strand breaks, resulting in cell death as monitored via clonogenic survival. Moreover, treatment of EJ28Luc bladder cancer cells resulted in decreased cell viability, [18F]FDG-uptake and an increased lactate export. In both EJ28Luc and LN18 carcinoma cells treatment with 213Bi-anti-EGFR-MAb triggered a significant increase in lactate/pyruvate ratios, as measured with hyperpolarized [1-13C]pyruvate. Treatment with 213Bi-anti-EGFR-MAb resulted in an effective induction of cell death in EJ28Luc and LN18 cells. Lactate/pyruvate ratios of hyperpolarized [1-13C]pyruvate proved to detect early treatment response effects, holding promise for future clinical applications in early therapy monitoring.JRC.G.I.5-Advanced Nuclear Knowledg

Fractionated intravesical radioimmunotherapy with 213Bi-anti-EGFR-MAb is effective without toxic side-effects in a nude mouse model of advanced human bladder carcinoma

Gold standard in therapy of superficial, non-muscle invasive urothelial tumors is transurethral resection followed by intravesical instillation therapies. However, relapse is commonly observed and therefore new therapeutic approaches are needed. Application of 213Bi-immunoconjugates targeting EGFR had shown promising results in early tumor stages. The aim of this study was the evaluation of fractionated application of 213Bi-anti-EGFR-MAb in advanced tumor stages in a nude mouse model. Luciferase-transfected EJ28 human bladder carcinoma cells were instilled intravesically into nude mice following electrocautery. Tumor development was monitored via bioluminescence imaging. One day after tumor detection mice were treated intravesically either two times with 0.93 MBq or three times with 0.46 MBq of 213Bi-anti-EGFR-MAb. Therapeutic efficacy was evaluated via overall survival and toxicity towards normal urothelium by histopathological analysis. Mice without treatment and those treated with the native anti-EGFR-MAb showed mean survivals of 65.4 and 57.6 d, respectively. After fractionated treatment with 0.93 MBq of 213Bi-anti-EGFR-MAb animals reached a mean survival of 141.5 d and 33% of the animals survived at least 268 d. Fractionated treatment with 0.46 MBq 213Bi-anti-EGFR-MAb resulted in a mean survival of 131.8 d and 30% of the animals survived longer than 300 d. Significant differences were only observed between the control groups and the group treated twice with 0.93 MBq of 213Bi-anti-EGFR-MAb. No toxic side-effects on the normal urothelium were observed even after treatment with 3.7 MBq of 213Bi-anti-EGFR-MAb. The study demonstrates that the fractionated intravesical radioimmunotherapy with 213Bi-anti-EGFR-MAb is a promising approach in advanced bladder carcinoma.JRC.E.5-Nuclear chemistr

Safety and efficacy of Ac-225-PSMA-617 in mCRPC after failure of Lu-177-PSMA

Despite the approval of several new agents metastatic castration resistant prostate cancer is still a major medical challenge. The beta-emitting Lu-177-PSMA radioligand therapy (RLT) is a new option but its antitumor effect can decrease over time. The aim of this retrospective analysis was to investigate safety and efficacy of the alpha emitting Ac-225-PSMA-617 RLT in mCRPC after Lu-177-PSMA failure.JRC.G.I.5-Advanced Nuclear Knowledg

Imaging of pH in vivo using hyperpolarized 13C-labelled zymonic acid.

Natural pH regulatory mechanisms can be overruled during several pathologies such as cancer, inflammation and ischaemia, leading to local pH changes in the human body. Here we demonstrate that 13C-labelled zymonic acid (ZA) can be used as hyperpolarized magnetic resonance pH imaging sensor. ZA is synthesized from [1-13C]pyruvic acid and its 13C resonance frequencies shift up to 3.0 p.p.m. per pH unit in the physiological pH range. The long lifetime of the hyperpolarized signal enhancement enables monitoring of pH, independent of concentration, temperature, ionic strength and protein concentration. We show in vivo pH maps within rat kidneys and subcutaneously inoculated tumours derived from a mammary adenocarcinoma cell line and characterize ZA as non-toxic compound predominantly present in the extracellular space. We suggest that ZA represents a reliable and non-invasive extracellular imaging sensor to localize and quantify pH, with the potential to improve understanding, diagnosis and therapy of diseases characterized by aberrant acid-base balance

Deuteration of hyperpolarized 13 c-labelled zymonic and enables sensitivity-enhanced dynamic MRI of pH

Aberrant pH is characteristic of many pathologies such as ischemia, inflammation or cancer. Therefore, a non-invasive and spatially resolved pH determination is valuable for disease diagnosis, characterization of response to treatment and the design of pH-sensitive drug-delivery systems. We recently introduced hyperpolarized [1,5-13C2]zymonic acid (ZA) as a novel MRI probe of extracellular pH utilizing dissolution dynamic polarization (DNP) for a more than 10000-fold signal enhancement of the MRI signal. Here we present a strategy to enhance the sensitivity of this approach by deuteration of ZA yielding [1,5-13C2, 3,6,6,6-D4]zymonic acid (ZAd), which prolongs the liquid state spin lattice relaxation time (T1) by up to 39 % in vitro. Measurements with ZA and ZAd on subcutaneous MAT B III adenocarcinoma in rats show that deuteration increases the signal-to-noise ratio (SNR) by up to 46 % in vivo. Furthermore, we demonstrate a proof of concept for real-time imaging of dynamic pH changes in vitro using ZAd, potentially allowing for the characterization of rapid acidification/basification processes in vivo

Proof of concept of a multimodal intravital molecular imaging system for tumour transpathology investigation.

BACKGROUND Transpathology highlights the interpretation of the underlying physiology behind molecular imaging. However, it remains challenging due to the discrepancies between in vivo and in vitro measurements and difficulties of precise co-registration between trans-scaled images. This study aims to develop a multimodal intravital molecular imaging (MIMI) system as a tool for in vivo tumour transpathology investigation. METHODS The proposed MIMI system integrates high-resolution positron imaging, magnetic resonance imaging (MRI) and microscopic imaging on a dorsal skin window chamber on an athymic nude rat. The window chamber frame was designed to be compatible with multimodal imaging and its fiducial markers were customized for precise physical alignment among modalities. The co-registration accuracy was evaluated based on phantoms with thin catheters. For proof of concept, tumour models of the human colorectal adenocarcinoma cell line HT-29 were imaged. The tissue within the window chamber was sectioned, fixed and haematoxylin-eosin (HE) stained for comparison with multimodal in vivo imaging. RESULTS The final MIMI system had a maximum field of view (FOV) of 18 mm × 18 mm. Using the fiducial markers and the tubing phantom, the co-registration errors are 0.18 ± 0.27 mm between MRI and positron imaging, 0.19 ± 0.22 mm between positron imaging and microscopic imaging and 0.15 ± 0.27 mm between MRI and microscopic imaging. A pilot test demonstrated that the MIMI system provides an integrative visualization of the tumour anatomy, vasculatures and metabolism of the in vivo tumour microenvironment, which was consistent with ex vivo pathology. CONCLUSIONS The established multimodal intravital imaging system provided a co-registered in vivo platform for trans-scale and transparent investigation of the underlying pathology behind imaging, which has the potential to enhance the translation of molecular imaging