Biology subjects

Pratx, G.

Publications and source records attributed to Pratx, G..

7 recordsLinked to original sources

bioRxiv2025

A Lung Tumor-on-a-Chip Model Recapitulates the Effect of Hypoxia on Radiotherapy Response and FDG-PET Imaging

Most solid tumors contain regions of hypoxia that pose a significant challenge to the efficacy of radiation therapy. This study introduces a novel 3D lung tumor-on-a-chip (ToC) model designed to replicate the hypoxic tumor microenvironment in vitro while also providing a platform for clinically relevant interventions such as radiotherapy and positron emission tomography (PET) imaging. To simulate the heterogeneous oxygen distribution found in tumors, the ToC model incorporates an oxygen gradient achieved through a straightforward chemical oxygen scavenging system. A unique innovation of this device is the integration of a thin scintillator plate, which enables high-resolution radioluminescence microscopy imaging of tumor metabolism under hypoxia and normoxia conditions using clinically approved PET tracers such as fluorodeoxyglucose (FDG). The response of this hypoxic model to radiation therapy (10 Gy X-ray) demonstrated [~]4-fold higher radioresistance compared to the normoxic ToC model, as assessed by colony formation potential. Additionally, DNA damage observed in the normoxic ToC model was [~]5-fold higher than that in the hypoxic model. Furthermore, the metabolic consumption of glucose was found to mirror the localization of hypoxia, validating the use of this biomarker for planning radiation therapy. The integration of high-resolution radionuclide imaging within ToC models enables on-chip PET imaging and facilitates oncology research and discovery, offering innovative capabilities for the preclinical testing of novel cancer therapies in a clinically relevant environment.

bioengineering↗

bioRxiv2020

High-resolution radioluminescence microscopy of FDG uptake in an engineered 3D tumor-stoma model

PURPOSEThe increased glucose metabolism of cancer cells is the basis for 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). However, due to its coarse image resolution, PET is unable to resolve the metabolic role of cancer-associated stroma, which often influences the metabolic reprogramming of a tumor. This study investigates the feasibility of imaging engineered 3D tumor models with high resolution using FDG. METHODMulticellular tumor spheroids (A549 lung adenocarcinoma) were co-cultured with GFP-expressing human umbilical vein endothelial cells (HUVECs) within an artificial extracellular matrix to mimic a tumor and its surrounding stroma. The tumor model was constructed as a thin 3D layer over a transparent CdWO4 scintillator plate to allow high-resolution imaging of the cultured cells. The radioluminescence signal was collected by a highly sensitive microscope and camera. Fluorescence microscopy was performed in the same instrument to localize endothelial and tumor cells. RESULTSSimultaneous brightfield and fluorescence imaging, co-localized with radioluminescence signal, provided high-resolution information on FDG accumulation in the engineered tissue. The microvascular stromal compartment took up a large fraction of FDG, comparable to the tumor spheroids. In vitro gamma counting also revealed that both A549 and HUVEC cells were highly glycolytic and characterized by rapid FDG-uptake kinetics. CONCLUSIONOur study demonstrates the feasibility of imaging FDG distribution in tumor and stromal components separately with high spatial resolution in engineered in vitro tumor models. Our imaging method is safe, simple, rapid, and can be easily used for other in vitro cancer models, surgical tissue slices, and tumor biopsies to interrogate PET radiotracer uptake at high resolution.

bioengineering↗

bioRxiv2020

High-resolution positron emission microscopy of patient-derived tumor organoids

Organoid tumor models have found application in a growing array of cancer studies due to their ability to closely recapitulate the structural and functional characteristics of solid tumors. However, organoids are too small to be compatible with common radiological tools used in oncology clinics. Here, we present a microscopy method to image 18F-fluorodeoxyglucose in patient-derived tumor organoids with spatial resolution up to 100-fold better than that of clinical positron emission tomography (PET). When combined with brightfield imaging, this metabolic imaging approach functionally mirrors clinical PET/CT scans and provides a quantitative readout of cell glycolysis. In particular, the specific avidity of a tumor for FDG, or lack thereof, was maintained when the tumor cells were grown ex vivo as tumor organoids. In addition, cisplatin treatment caused a dose-dependent decrease in the metabolic activity of these organoids, with the exception of one patient whose tumor was also resistant to cisplatin treatment. Thus, FDG-imaging of organoids could be used to predict the response of individual patients to different treatments and provide a more personalized approach to cancer care.

cancer biology↗

bioRxiv2020

Highly Sensitive Identification of Lymphatic and Hematogenous Metastasis Routes of Novel Radiolabeled Exosomes Using Non-invasive PET Imaging

Clinically, there has been significant interest in the use of exosomes for diagnostic applications as promising biomarkers and therapeutic applications as therapeutic vehicles. However, knowledge of in vivo physiological biodistribution of exosomes was difficult to assess until now. Physiological distribution of exosomes in the body must be elucidated for clinical application. In this study, we aimed to develop reliable and novel methods to monitor biodistribution of exosomes using in vivo PET and optical imaging. MethodsExosomes were isolated from cultured medium of 4T1, mouse breast cancer cells. Exosomes were labeled with Cy7 and 64Cu (or 68Ga). In mice, radio/fluorescent dye-labeled exosomes were injected through the lymphatic routes (footpad injection) and hematogenous metastatic routes (tail vein injection). Fluorescence and PET images were obtained and quantified. Radio-activity of ex vivo organs was measured by gamma counter. ResultsPET signals from exosomes in the lymphatic metastatic route were observed in the draining lymph nodes, which are not distinguishable with optical imaging. Immunohistochemistry revealed greater uptake of exosomes in brachial and axillary lymph nodes than inguinal lymph node. After administration through the hematogenous metastasis pathway, accumulation of exosomes was clearly observed in PET images in the lungs, liver, and spleen, showing results similar to ex vivo gamma counter data. ConclusionExosomes from tumor cells were successfully labeled with 64Cu (or 68Ga) and visualized by PET imaging. These results suggest that this cell type-independent, quick, and easy exosome labeling method using PET isotopes could provide valuable information for further application of exosomes in the clinic.

cancer biology↗

bioRxiv2019

CellGPS: Whole-body tracking of single cells by positron emission tomography

In vivo molecular imaging tools are critically important for determining the role played by cell trafficking in biological processes and cellular therapies. However, existing tools measure average cell behavior and not the kinetics and migration routes of individual cells inside the body. Furthermore, efflux and non-specific accumulation of contrast agents are confounding factors, leading to inaccurate estimation of cell distribution in vivo. In view of these challenges, we report the development of a \"cellular GPS\" capable of tracking single cells inside living subjects with exquisite sensitivity. We use mesoporous silica nanoparticles (MSN) to concentrate 68Ga radioisotope into live cells and inject these cells into live mice. From the pattern of annihilation photons detected by positron emission tomography (PET), we infer, in real time, the position of individual cells with respect to anatomical landmarks derived from X-ray computed tomography (CT). To demonstrate this technique, a single human breast cancer cell was tracked in a mouse model of experimental metastasis. The cell arrested in the lungs 2-3 seconds after tail-vein injection. Its average velocity was estimated at around 50 mm/s, consistent with blood flow rate. Other cells were tracked after injection through other routes, but no motion was detected within 10 min of acquisition. Single-cell tracking could be applied to determine the kinetics of cell trafficking and arrest during the earliest phase of the metastatic cascade, the trafficking of immune cells during cancer immunotherapy, or the distribution of cells after transplantation in regenerative medicine.

bioengineering↗

bioRxiv2019

Single-cell radioluminescence microscopy with two-fold higher sensitivity using dual scintillator configuration

Radioluminescence microscopy (RLM) is an imaging technique that allows quantitative analysis of clinical radiolabeled drugs and probes in single cells. However, the modality suffers from slow data acquisition (10 - 15 minutes), thus critically affecting experiments with short-lived radioactive drugs. To overcome this issue, we suggest an approach that significantly accelerates data collection. Instead of using a single scintillator to image the decay of radioactive molecules, we sandwiched the radiolabeled cells between two scintillators. As proof of concept, we imaged cells labeled with [18F]FDG, a radioactive glucose popularly used in oncology to image tumors. Results show that the double scintillator configuration increases the microscope sensitivity by two-fold, thus reducing the image acquisition time by half to achieve the same result as the single scintillator approach. The experimental results were also compared with Geant4 Monte Carlo simulation to confirm the two-fold increase in sensitivity with only minor degradation in spatial resolution. Overall, these findings suggest that the double scintillator configuration can be used to perform time-sensitive studies such as cell pharmacokinetics or cell uptake of short-lived radiotracers.

bioengineering↗

bioRxiv2019

Dependence of fluorodeoxyglucose (FDG) uptake on cell cycle and dry mass: a single-cell study using a multi-modal radiography platform

High glucose uptake by cancer compared to normal tissues has long been utilized in fluorodeoxyglucose-based positron emission tomography (FDG-PET) as a contrast mechanism. The FDG uptake rate has been further related to the proliferative potential of cancer, specifically the proliferation index (PI) - the proportion of cells in S, G2 or M phases. The underlying hypothesis was that the cells preparing for cell division would consume more energy and metabolites as building blocks for biosynthesis. Despite the wide clinical use, mixed reports exist in the literature on the relationship between FDG uptake and PI. This may be due to the large variation in cancer types or methods adopted for the measurements. Of note, the existing methods can only measure the average properties of a tumor mass or cell population with highly-heterogeneous constituents. In this study, we have built a multi-modal live-cell radiography system and measured the [18F]FDG uptake by single HeLa cells together with their dry mass and cell cycle phase. The results show that HeLa cells take up twice more [18F]FDG in S, G2 or M phases than in G1 phase, which confirms the association between FDG uptake and PI at a single-cell level. Importantly, we show that [18F]FDG uptake and cell dry mass have a positive correlation in HeLa cells, which suggests that high [18F]FDG uptake in S, G2 or M phases can be largely attributed to increased dry mass, rather than the activities preparing for cell division. This interpretation is consistent with recent observations that the energy required for the preparation of cell division is much smaller than that for maintaining house-keeping proteins.

biophysics↗