Diffusion of hyperpolarized ¹³C‐metabolites in tumor cell spheroids using real‐time NMR spectroscopy

Abstract

The detection of tumors noninvasively, the characterization of their progression by defined markers and the monitoring of response to treatment are goals of medical imaging techniques. In this article, a method which measures the apparent diffusion coefficients (ADCs) of metabolites using hyperpolarized (13) C diffusion-weighted spectroscopy is presented. A pulse sequence based on the pulsed gradient spin echo (PGSE) was developed that encodes both kinetics and diffusion information. In experiments with MCF-7 human breast cancer cells, we detected an ADC of intracellularly produced lactate of 1.06 ± 0.15 µm(2) /ms, which is about one-half of the value measured with pyruvate in extracellular culture medium. When monitoring tumor cell spheroids during progressive membrane permeabilization with Triton X-100, the ratio of lactate ADC to pyruvate ADC increases as the fraction of dead cells increases. Therefore, (13) C ADC detection can yield sensitive information on changes in membrane permeability and subsequent cell death. Our results suggest that both metabolic label exchange and (13) C ADCs can be acquired simultaneously, and may potentially serve as noninvasive biomarkers for pathological changes in tumor cells.

Changes in Pyruvate Metabolism Detected by Magnetic Resonance Imaging Are Linked to DNA Damage and Serve as a Sensor of Temozolomide Response in Glioblastoma Cells

“…Given the previously described connection between reduced intracellular lactate levels and decreased conversion of 13 Cpyruvate to 13 C lactate (21), it seems reasonable that the TMZ-induced decreases in intracellular lactate levels noted here resulted in the decreased pyruvate to lactate conversion in TMZ-treated animals. While direct proof of this linkage would require more complex methods such as diffusion-weighted spectroscopy to measure intracellular lactate levels in vivo (48, 49), the present data clearly show that PKM2 plays a key role in linking the DNA damage response to monitorable changes in pyruvate metabolism that in turn relate to drug efficacy.…”

Separation of extra- and intracellular metabolites using hyperpolarized 13C diffusion weighted MR

“…Previous studies have quantified these non-diffusion related signal changes and corrected the diffusion weighted acquisitions accordingly [10,11]. To simplify the quantification of the diffusion coefficients, multiple interspersed normalization scans were acquired temporally close to the diffusion weighted scans and thereby eliminate the effects of these non-diffusion weighted signal changes.…”

“…Recently, there have been several publications that have used diffusion weighted MR to measure the diffusion coefficients of hyperpolarized 13 C metabolites, in solution [10], in cell suspensions [11] and in vivo [12–14]. These studies showed how changes in the ADCs could indicate the extra- and intracellular localization of the hyperpolarized 13 C metabolites.…”

Imaging Renal Urea Handling in Rats at Millimeter Resolution Using Hyperpolarized Magnetic Resonance Relaxometry

“…In addition to chemical shift [16, 73, 74, 75, 76, 77] and diffusion [78, 13, 79, 72, 80] sensitive imaging techniques, T 2 relaxometry could be a very useful tool for probing the microenvironment of hyperpolarized 13 C molecules in vivo since it yields high signal thus allowing for high resolution encoding.…”