Non-Invasive Assessment of Lactate Production and Compartmentalization in Renal Cell Carcinomas Using Hyperpolarized 13C Pyruvate MRI

Abstract

Optimal treatment selection for localized renal tumors is challenging due to their variable biological behavior and limited ability to pre-operatively assess their aggressiveness. We investigated hyperpolarized (HP) 13C pyruvate MRI to noninvasively assess tumor lactate production and compartmentalization, which are strongly associated with renal tumor aggressiveness. Orthotopic tumors were created in mice using human renal cell carcinoma (RCC) lines (A498, 786-O, UOK262) with varying expression of lactate dehydrogenase A (LDHA) which catalyzes the pyruvate-to-lactate conversion, and varying expression of monocarboxylate transporter 4 (MCT4) which mediates lactate export out of the cells. Dynamic HP 13C pyruvate MRI showed that the A498 tumors had significantly higher 13C pyruvate-to-lactate conversion than the UOK262 and 786-O tumors, corresponding to higher A498 tumor LDHA expression. Additionally, diffusion-weighted HP 13C pyruvate MRI showed that the A498 tumors had significantly higher 13C lactate apparent diffusion coefficients compared to 786-O tumors, with corresponding higher MCT4 expression, which likely reflects more rapid lactate export in the A498 tumors. Our data demonstrate the feasibility of HP 13C pyruvate MRI to inform on tumor lactate production and compartmentalization, and provide the scientific premise for future clinical investigation into the utility of this technique to noninvasively interrogate renal tumor aggressiveness and to guide treatment selection.

Elevated Tumor Lactate and Efflux in High-grade Prostate Cancer demonstrated by Hyperpolarized 13C Magnetic Resonance Spectroscopy of Prostate Tissue Slice Cultures

“…For in vivo studies, the HP [1-13 C]lactate that effluxes out of the cell will remain predominately in the tumor microenvironment and should add rather than subtract from the HP [1-13 C]lactate signal, providing a large increase in hyperpolarized lactate with the presence of Gleason grade 4 and 5 cancer. This supposition is consistent with prior studies involving renal cell cancer cells implanted under the renal capsule [49]. The ability to assess the percentage of Gleason grade 4 and 5 cancer in a tumor has significant implications for selection of the appropriate therapy for patients since cancers with a Gleason score of ≤ 3 + 3 are considered indolent and appropriate for active surveillance while a Gleason score of 7 or higher portends more aggressive cancer.…”

“…One approach for estimating lactate efflux in vivo is based on the concept that the compartmental (intra-versus extra-cellular) difference in mean free diffusion path length would be reflected by the apparent diffusion constant (ADC). While the clinical feasibility of measuring HP lactate ADC is still under development, there are numerous preclinical studies that have shown that it can be measured and used to stratify tumor aggressiveness [49,[55][56][57][58][59]].…”

“…The pathologist also marked regions of benign epithelium and cancer on the sections which were used as guidelines to scrape the respective tissue from the OCT embedding for further RNA extraction in case of biopsy and LDH activity for the tissue slices. Furthermore, the tissue slices were stained with anti-MCT4 antibody (rabbit polyclonal primary antibody SC-376140 from Santa Cruz Biotechnology Inc., Dallas, TX, USA) in 1:100 dilution at 4 • C overnight, followed by incubation with rabbit secondary antibody/ HRP at 1:200 dilution for 20 min at room temperature as before [49], to detect MCT4 at the cell membrane.…”

Modeling hyperpolarized lactate signal dynamics in cells, patient‐derived tissue slice cultures and murine models

“…This was attributed to the lower cell density of the A498 tumors contributing to the lactate signal (for the same voxel volume). Prior work in Sriram et al 16 has demonstrated that cellular density and proton ADC are inversely correlated (cellular density ~ 1/ADC) for these RCC tumors. Thus, using the same rationale and data, cell density‐normalized k PL values can be calculated by using the k PL x ADC product.…”

NMR quantification of lactate production and efflux and glutamate fractional enrichment in living human prostate biopsies cultured with [1,6‐13C2]glucose

“…In tissues, automated cell counting and/or protein quantification requires tissue digestion, making it impossible to obtain high‐quality histopathology. It is possible to estimate tissue cellularity using automated image analysis of histopathology slides; however, given the heterogeneity of human prostate tissue, this approach might yield inaccurate results unless the fixed, embedded, and stained tissue is comprehensively sliced to yield a 3D image stack. Another possibility is to analyze the metabolites of interest in terms of their ratios to a reference metabolite .…”