In-Cell Determination of Lactate Dehydrogenase Activity in a Luminal Breast Cancer Model – ex vivo Investigation of Excised Xenograft Tumor Slices Using dDNP Hyperpolarized [1-13C]pyruvate

Abstract

[1-13C]pyruvate, the most widely used compound in dissolution-dynamic nuclear polarization (dDNP) magnetic resonance (MR), enables the visualization of lactate dehydrogenase (LDH) activity. This activity had been demonstrated in a wide variety of cancer models, ranging from cultured cells, to xenograft models, to human tumors in situ. Here we quantified the LDH activity in precision cut tumor slices (PCTS) of breast cancer xenografts. The Michigan Cancer Foundation-7 (MCF7) cell-line was chosen as a model for the luminal breast cancer type which is hormone responsive and is highly prevalent. The LDH activity, which was manifested as [1-13C]lactate production in the tumor slices, ranged between 3.8 and 6.1 nmole/nmole adenosine tri-phosphate (ATP) in 1 min (average 4.6 ± 1.0) on three different experimental set-ups consisting of arrested vs. continuous perfusion and non-selective and selective RF pulsation schemes and combinations thereof. This rate was converted to an expected LDH activity in a mass ranging between 3.3 and 5.2 µmole/g in 1 min, using the ATP level of these tumors. This indicated the likely utility of this approach in clinical dDNP of the human breast and may be useful as guidance for treatment response assessment in a large number of tumor types and therapies ex vivo.

Correlation between lactate dehydrogenase/pyruvate dehydrogenase activities ratio and tissue pH in the perfused mouse heart: A potential noninvasive indicator of cardiac pH provided by hyperpolarized magnetic resonance

“…While LDH is also present extracellularly in the living animal, in the isolated perfused heart its extracellular activity likely cannot be recorded due to wash out of all metabolites by the perfusing buffer. The hyperpolarized product selective saturating-excitations approach applied here 63,82 enabled us to determine enzymatic activity in a manner that is independent of variations in T 1 of…”

“…The final composition of the injected medium (after mixing) contained 4.7 mM KCl, 1.2 mM MgSO 4 , 70 mM NaCl, 25 mM NaHCO 3 , 1.2 mM KH 2 PO 4 , 10 mM glucose, 1.2 mM CaCl 2 and 72 U/L insulin. The injection of the resulting hyperpolarized [1‐ 13 C]pyruvate solution to the isolated heart was carried out using a continuous flow set‐up 82 such that the heart perfusion was not interrupted at any point during the experiment and the hyperpolarized medium was administered at a known rate and duration.…”

“…To be able to determine the time points at which the hyperpolarized [1-13 C]pyruvate concentration was maximal and constant, the [1-13 C]pyruvate signal was corrected for apparent T 1 decay using an apparent T 1 of 53.4 seconds. 82 This value was previously determined for hyperpolarized [1-13 C]pyruvate in the same spectrometer, at the same pH, temperature and osmolarity, using the same perfusion system, under perfusion arrest, and therefore sums up the effective decay due to T 1 relaxation, RF pulsation, and C]bicarbonate production for these time points were used for the calculation of metabolite production rates using Equations 3A and 3B. A typical example of such a selection of time points is shown in Figure 3C (highlighted temporal window).…”

Differentiation of Heterogeneous Mouse Liver from HCC by Hyperpolarized 13C Magnetic Resonance

“…The entire data set described in Table 1 was used to reach the results described in Figure 3 in the text. The product-selective RF pulse profiles and the determination of the relative responses of the product and the substrate (ρ in Table 1) were previously described by Adler-Levi et al [40] (2.5 ms Sinc pulse) and Lev-Cohain et al [21] (3 ms Gaussian pulse). The enzymatic rates obtained from healthy animals (Mice number 1-3 in Table 1) were published previously in Lev-Cohain et al [21].…”

Differentiation of Heterogeneous Mouse Liver from HCC by Hyperpolarized 13C Magnetic Resonance

“…The entire data set described in Table 1 was used to reach the results described in Figure 3 in the text. The product-selective RF pulse profiles and the determination of the relative responses of the product and the substrate (ρ in Table 1) have been previously described in Adler-Levi et al [40] (2.5 ms Sinc pulse) and Lev-Cohain et al [21] (3 ms Gaussian pulse). The enzymatic rates obtained from healthy animals (Mice number 1-3 in Table 1) were published previously in Lev-Cohain et al [21].…”