Lonidamine Induced Selective Acidification and De-Energization of Prostate Cancer Xenografts: Enhanced Tumor Response to Radiation Therapy.

Prostate cancer is a multi-focal disease that can be treated using surgery, radiation, androgen deprivation, and chemotherapy, depending on its presentation. Standard dose-escalated radiation therapy (RT) in the range of 70-80 Gray (GY) is a standard treatment option for prostate cancer. It could be used at different phases of the disease (e.g., as the only primary treatment when the cancer is confined to the prostate gland, combined with other therapies, or as an adjuvant treatment after surgery). Unfortunately, RT for prostate cancer is associated with gastro-intestinal and genitourinary toxicity. We have previously reported that the metabolic modulator lonidamine (LND) produces cancer sensitization through tumor acidification and de-energization in diverse neoplasms. We hypothesized that LND could allow lower RT doses by producing the same effect in prostate cancer, thus reducing the detrimental side effects associated with RT. Using the Seahorse XFe96 and YSI 2300 Stat Plus analyzers, we corroborated the expected LND-induced intracellular acidification and de-energization of isolated human prostate cancer cells using the PC3 cell line. These results were substantiated by non-invasive 31P magnetic resonance spectroscopy (MRS), studying PC3 prostate cancer xenografts treated with LND (100 mg/kg, i.p.). In addition, we found that LND significantly increased tumor lactate levels in the xenografts using 1H MRS non-invasively. Subsequently, LND was combined with radiation therapy in a growth delay experiment, where we found that 150 µM LND followed by 4 GY RT produced a significant growth delay in PC3 prostate cancer xenografts, compared to either control, LND, or RT alone. We conclude that the metabolic modulator LND radio-sensitizes experimental prostate cancer models, allowing the use of lower radiation doses and diminishing the potential side effects of RT. These results suggest the possible clinical translation of LND as a radio-sensitizer in patients with prostate cancer.

Metabolic Imaging Biomarkers of Response to Signaling Inhibition Therapy in Melanoma.

Dabrafenib therapy for metastatic melanoma focuses on blocking growth-promoting signals produced by a hyperactive BRAF protein. We report the metabolic differences of four human melanoma cell lines with diverse responses to dabrafenib therapy (30 mg/kg; oral): WM3918 < WM9838BR < WM983B < DB-1. Our goal was to determine if metabolic changes produced by the altered signaling pathway due to BRAF mutations differ in the melanoma models and whether these differences correlate with response to treatment. We assessed metabolic changes in isolated cells using high-resolution proton magnetic resonance spectroscopy (1H MRS) and supplementary biochemical assays. We also noninvasively studied mouse xenografts using proton and phosphorus (1H/31P) MRS. We found consistent changes in lactate and alanine, either in isolated cells or mouse xenografts, correlating with their relative dabrafenib responsiveness. In xenografts, we also observed that a more significant response to dabrafenib correlated with higher bioenergetics (i.e., increased ßNTP/Pi). Notably, our noninvasive assessment of the metabolic status of the human melanoma xenografts by 1H/31P MRS demonstrated early metabolite changes preceding therapy response (i.e., tumor shrinkage). Therefore, this noninvasive methodology could be translated to assess in vivo predictive metabolic biomarkers of response in melanoma patients under dabrafenib and probably other signaling inhibition therapies.

pH-dependent structural characteristics of lonidamine: 1H and 13C NMR study.

Lonidamine (LND) is an anti-cancer drug with great potential as a metabolic modulator of chemotherapy, radiotherapy, hyperthermia, and photodynamic therapy in cancer treatment. LND affects several important aspects of cancer cell metabolism: it inhibits Complex I and II of the electron transport chain (ETC) and pyruvate carriers (mitochondrial), and monocarboxylate transporters in the plasma membrane of the cell. Cancer cells are affected by changes in pH on the molecular level, and so are the drugs used to treat cancer, thus it is important to understand how pH affects their structures and LND is no exception. LND dissolves at a pH of 8.3 in tris-glycine buffer but has limited solubility at pH 7. To understand how pH affects the structure of LND, and its effect as a metabolic modulator on cancer therapy, we made up samples of LND at pH 2, pH 7, and pH 13, and analyzed these samples using 1H and 13C NMR. We looked for ionization sites to explain the behavior of LND in solution. Our results showed considerable chemical shifts between the extremes of our experimental pH range. LND was ionized at its indazole α-nitrogen, however, we did not directly observe the protonation of the carboxyl group oxygen that is expected at pH 2, which may be the result of a chemical-exchange phenomenon.

In vivo assessment of ß-hydroxybutyrate metabolism in mouse brain using deuterium (2 H) MRS.

PURPOSE: To monitor the metabolic turnover of ß-hydroxybutyrate (BHB) oxidation using 2 H-MRS in conjunction with intravenous administration of 2 H labeled BHB. METHODS: Nine-month-old mice were infused with [3,4,4,4]-2 H4 -BHB (d4 -BHB; 3.11 g/kg) through the tail vein using a bolus variable infusion rate for a period of 90 min. The labeling of downstream cerebral metabolites from the oxidative metabolism of d4 -BHB was monitored using 2 H-MRS spectra acquired with a home-built 2 H surface coil on a 9.4T preclinical MR scanner with a temporal resolution of 6.25 min. An exponential model was fit to the BHB and glutamate/glutamine (Glx) turnover curves to determine rate constants of metabolite turnover and to aid in the visualization of metabolite time courses. RESULTS: Deuterium label was incorporated into Glx from BHB metabolism through the tricarboxylic acid (TCA) cycle, with an increase in the level of [4,4]-2 H2 -Glx (d2 -Glx) over time and reaching a quasi-steady state concentration of ∼0.6 ± 0.1 mM following 30 min of infusion. Complete oxidative metabolic breakdown of d4 -BHB also resulted in the formation of semi-heavy water (HDO), with a four-fold (10.1 to ∼42.1 ± 7.3 mM) linear (R2  = 0.998) increase in its concentration by the end of infusion. The rate constant of Glx turnover from d4 -BHB metabolism was determined to be 0.034 ± 0.004 min-1 . CONCLUSION: 2 H-MRS can be used to monitor the cerebral metabolism of BHB with its deuterated form by measuring the downstream labeling of Glx. The integration of 2 H-MRS with deuterated BHB substrate provides an alternative and clinically promising MRS tool to detect neurometabolic fluxes in healthy and disease conditions.

Bonded cumomer analysis of tumor metabolism based on 13 C magnetic resonance spectroscopy.

Bonded cumomers are sets of isotopomers of 13 C-labeled metabolites containing a particular sequence of contiguously or singly labeled carbon atoms. Only these isotopomers contribute to multiplet structure in the 13 C NMR spectrum. We discuss the application of this technique to the study of quantitative tumor metabolism, bioenergetics, and the Warburg effect. The advantages and sensitivity of bonded cumomer analysis over positional enrichment analysis are discussed. When sensitivity requirements are met, bonded cumomer analysis enables the extraction of fluxes through specific metabolic pathways with higher precision. In conjunction with isotopomer control analysis, we evaluate the sensitivity of experimentally measurable metabolite multiplets to determine the robustness of flux analysis in 13 C spectra of tumors. This review examines the role of glycolytic and tricarboxylic acid cycle metabolism with special emphasis on flux through the pentose phosphate pathway (PPP). The impact of reversibility of the nonoxidative branch of the PPP with various 13 C glucose tracers on fine-structure multiplets is analyzed.

Feasibility of Non-invasive Measurement of Tumour NAD(H) by In Vivo Phosphorus-31 Magnetic Resonance Spectroscopy.

Importance of the redox status of nicotinamide adenine dinucleotide (NAD), including its oxidized (NAD+) and reduced (NADH) forms, has been shown in many biological processes. However, NAD(H) redox status assessment is traditionally limited to biochemical assays in vitro or optical redox imaging (ORI) for superficial tissues in vivo and for deep tissues ex vivo. In recent years, phosphorous-31 magnetic resonance spectroscopy (31P-MRS) was utilized to quantify NAD+, NADH, and the redox ratio NAD+/NADH in normal tissues in vivo. The quantification is based on the spectral fitting of the upfield shoulder of the αATP peak that contains signals of NAD+ (a quartet) and NADH (a singlet), assuming pH-independence of peak positions. To evaluate the feasibility of measuring tumour NAD(H) redox status in vivo, we fitted single voxel 31P-MR spectra of subcutaneous mouse xenografts of human breast cancer cell lines acquired on a 9.4-T horizontal bore preclinical MR scanner. We found larger variations in the chemical shift offsets of NAD+ and NADH from αATP in these tumours than the literature values of normal tissues. Furthermore, our 31P-MR spectra of αATP, NAD+, and NADH solution phantoms indicated that the chemical shift of αATP and thus the offsets between NAD(H) and αATP were pH dependent. Therefore, whether tumour pH should be incorporated into the spectral fitting model should be further evaluated. Additionally, spectral resolution and signal-to-noise ratio should be improved by optimising 31P-MRS protocols, increasing data acquisition time, and using a more sensitive coil for signal detection.

Assessment of Nicotinamide Adenine Dinucleotide in Human Tissues by In Vivo Phosphorus-31 Magnetic Resonance Spectroscopic Imaging at 1.5 Tesla.

As a phosphorus-containing molecule, nicotinamide adenine dinucleotide is visible by phosphorus magnetic resonance spectroscopy (31P-MRS). However, the relatively low cellular levels of its oxidised (NAD+) and reduced (NADH) forms and a significant peak overlap hinder their evaluation in live tissues. This problem is critical when using 31P-MR spectroscopic imaging, where signals are localised from limited tissue volumes. We have reported improvements in spectral resolution of 31P-MRSI of human tissues in situ using a strict optimisation of the static magnetic field (B0 shimming) and 1H-irradiation during 31P acquisition. Given this, we aimed to demonstrate if these improvements allowed us to measure the in vivo intracellular levels of NAD+ and NADH at the relatively low magnetic field of 1.5 tesla (T). Our results show the feasibility of the in vivo determination of NAD+ and NADH from relatively small volumes of human tissues studied at 1.5 T. These results are clinically relevant as the currently available systems for human use mainly operate at 1.5 or 3.0.

In-phase simultaneous spectral editing of lactate and alanine with suppression of J-coupled lipids by the modified selective multiple quantum coherence sequences.

1H magnetic resonance spectroscopy (MRS) with the multiple quantum coherence (MQC) technique allows for the detection of lactate, an end product of glycolysis, in the environment of lipids. The method can also be used to detect alanine, a byproduct of glutaminolysis. An issue is that when both lactate and alanine are detected together by the MQC technique, a phase mismatch arises between lactate and alanine signals due to off-resonance rotations and the difference in double quantum coherence frequencies between the two molecules. Such phase mismatch can cause errors in spectral fitting and metabolite quantification. In this study, we designed two pulse sequences that eliminate such phase differences of lactate and alanine while suppressing lipid signals by modifications of the Selective Multiple Quantum Coherence (Sel-MQC) sequence, a well-known MQC technique. Using the product operator formalism and the off-resonance rotation matrices, the phase evolutions of lactate and alanine during the spectrally selective pulses and the free precession times of the sequence at the single quantum, double quantum and zero quantum coherence states of these molecules were calculated. The multiple quantum (MQ) evolution time t1 that can remove the phase difference of lactate and alanine at the echo was calculated and fine-tuned with experiments. The lactate and alanine signal intensities and the editing efficiencies from the two modified Sel-MQC sequences were theoretically predicted by using the product operator evolutions and compared with the experimental data. The J-coupled lipid signals were successfully suppressed by both sequences. One of the two developed sequences was applied to a human body with a phantom of lactate and alanine, which resulted in successful in-phase editing of lactate and alanine and suppression of the lipid signals from the body. The study sets an important foundation for the noninvasive detection of lactate and alanine from tumors of cancer patients.

Emerging MR Imaging and Spectroscopic Methods to Study Brain Tumor Metabolism.

Proton magnetic resonance spectroscopy (1H-MRS) provides a non-invasive biochemical profile of brain tumors. The conventional 1H-MRS methods present a few challenges mainly related to limited spatial coverage and low spatial and spectral resolutions. In the recent past, the advent and development of more sophisticated metabolic imaging and spectroscopic sequences have revolutionized the field of neuro-oncologic metabolomics. In this review article, we will briefly describe the scientific premises of three-dimensional echoplanar spectroscopic imaging (3D-EPSI), two-dimensional correlation spectroscopy (2D-COSY), and chemical exchange saturation technique (CEST) MRI techniques. Several published studies have shown how these emerging techniques can significantly impact the management of patients with glioma by determining histologic grades, molecular profiles, planning treatment strategies, and assessing the therapeutic responses. The purpose of this review article is to summarize the potential clinical applications of these techniques in studying brain tumor metabolism.

Metabolic and physiologic magnetic resonance imaging in distinguishing true progression from pseudoprogression in patients with glioblastoma.

Pseudoprogression (PsP) refers to treatment-related clinico-radiologic changes mimicking true progression (TP) that occurs in patients with glioblastoma (GBM), predominantly within the first 6 months after the completion of surgery and concurrent chemoradiation therapy (CCRT) with temozolomide. Accurate differentiation of TP from PsP is essential for making informed decisions on appropriate therapeutic intervention as well as for prognostication of these patients. Conventional neuroimaging findings are often equivocal in distinguishing between TP and PsP and present a considerable diagnostic dilemma to oncologists and radiologists. These challenges have emphasized the need for developing alternative imaging techniques that may aid in the accurate diagnosis of TP and PsP. In this review, we encapsulate the current state of knowledge in the clinical applications of commonly used metabolic and physiologic magnetic resonance (MR) imaging techniques such as diffusion and perfusion imaging and proton spectroscopy in distinguishing TP from PsP. We also showcase the potential of promising imaging techniques, such as amide proton transfer and amino acid-based positron emission tomography, in providing useful information about the treatment response. Additionally, we highlight the role of "radiomics", which is an emerging field of radiology that has the potential to change the way in which advanced MR techniques are utilized in assessing treatment response in GBM patients. Finally, we present our institutional experiences and discuss future perspectives on the role of multiparametric MR imaging in identifying PsP in GBM patients treated with "standard-of-care" CCRT as well as novel/targeted therapies.

Coherence pathway analysis of J-coupled lipids and lactate and effective suppression of lipids upon the selective multiple quantum coherence lactate editing sequence.

Objective.The selective multiple quantum coherence (Sel-MQC) sequence is a magnetic resonance spectroscopy (MRS) technique used to detect lactate and suppress co-resonant lipid signalsin vivo. The coherence pathways of J-coupled lipids upon the sequence, however, have not been studied, hindering a logical design of the sequence to fully attenuate lipid signals. The objective of this study is to elucidate the coherence pathways of J-coupled lipids upon the Sel-MQC sequence and find a strategy to effectively suppress lipid signals from these pathways while keeping the lactate signal.Approach.The product operator formalism was used to express the evolutions of the J-coupled spins of lipids and lactate. The transformations of the product operators by the spectrally selective pulses of the sequence were calculated by using the off-resonance rotation matrices. The coherence pathways and the conversion rates of the individual pathways were derived from them. Experiments were performed on phantoms and two human subjects at 3 T.Main results.The coherence pathways contributing to the various lipid resonance signals by the Sel-MQC sequence depending on the gradient ratios and RF pulse lengths were identified. Theoretical calculations of the signals from the determined coherence pathways and signal attenuations by gradients matched the experimental data very well. Lipid signals from fatty tissues of the subjects were successfully suppressed to the noise level by using the gradient ratio -0.8:-1:2 or 1:0.8:2. The new gradient ratios kept the lactate signal the same as with the previously used gradient ratio 0:-1:2.Significance.The study has elucidated the coherence pathways of J-coupled lipids upon the Sel-MQC sequence and demonstrated how lipid signals can be effectively suppressed while keeping lactate signals by using information from the coherence pathway analysis. The findings enable applying the Sel-MQC sequence to lactate detection in an environment of high concentrations of lipids.

Advanced magnetic resonance imaging and spectroscopy in a case of neurocysticercosis from North America.

Neurocysticercosis (NCC) is a parasitic infection caused by Cysticercus cellulosae, the metacestode of pork tapeworm (Taenia solium). NCC is one of the most common public health problems worldwide. We present a patient harboring a bilobed ring-enhancing lesion with a presumed diagnosis of brain metastasis, who returned to the USA after traveling to an endemic region. The diagnosis of NCC was established based on a characteristic resonance of succinate on proton magnetic resonance spectroscopy. Also, higher mean diffusivity and lower fractional anisotropy along with relative cerebral blood volume were observed from the lesion compared to contralateral normal brain regions. Multiparametric analysis may improve the differential diagnosis of ring-enhancing intracranial lesions such as NCC.

Noninvasive urine metabolomics of prostate cancer and its therapeutic approaches: a current scenario and future perspective.

INTRODUCTION: The sensitive, specific, fast, robust and noninvasive biomarkers for the evaluation of prostate cancer (PC) remain elusive in medical research. However, efforts are in full sway to investigate and resolve these puzzles for clinical practice. Advances in modern analytical techniques, sample processing, and the emergence of multiple omics approaches have created a great hope for the development of better detection modalities for PC. The objective of the present review is to provide a concise overview of the PC metabolomics-based potential discriminating molecules in urine samples using nuclear magnetic resonance spectroscopy and mass spectrometry. AREA COVERED: A literature search was executed to find the studies reporting the noninvasive urine-based biomarkers for the diagnosis and prognosis of underlying disease. Most studies have extensivelyreported PC discriminating molecules with their respective controls. Additionally, pathophysiology and the treatment paradigm of PC are summarized and related to the insights underpinning the therapeutic intervention of PC. EXPERT OPINION: With multi-centric, global, comprehensive omics approaches via either a non- or least-invasive bio-matrix may open new avenues of research for PC biomarker discovery, backed by a molecular mechanistic outline.

Physiological Imaging Methods for Evaluating Response to Immunotherapies in Glioblastomas.

Glioblastoma (GBM) is the most malignant brain tumor in adults, with a dismal prognosis despite aggressive multi-modal therapy. Immunotherapy is currently being evaluated as an alternate treatment modality for recurrent GBMs in clinical trials. These immunotherapeutic approaches harness the patient's immune response to fight and eliminate tumor cells. Standard MR imaging is not adequate for response assessment to immunotherapy in GBM patients even after using refined response assessment criteria secondary to amplified immune response. Thus, there is an urgent need for the development of effective and alternative neuroimaging techniques for accurate response assessment. To this end, some groups have reported the potential of diffusion and perfusion MR imaging and amino acid-based positron emission tomography techniques in evaluating treatment response to different immunotherapeutic regimens in GBMs. The main goal of these techniques is to provide definitive metrics of treatment response at earlier time points for making informed decisions on future therapeutic interventions. This review provides an overview of available immunotherapeutic approaches used to treat GBMs. It discusses the limitations of conventional imaging and potential utilities of physiologic imaging techniques in the response assessment to immunotherapies. It also describes challenges associated with these imaging methods and potential solutions to avoid them.

Role of metabolomics-derived biomarkers to identify renal cell carcinoma: a comprehensive perspective of the past ten years and advancements.

Introduction: Renal cell carcinoma (RCC) is one of the most prevalent metabolic diseases and a leading cause of utmost mortality among men globally. In spite of extensive development in technology for biomarker discovery during the last 10 years, the currently used clinical biomarkers are still unable to detect RCC at early and progression stages. Hence, the development of new and precise biomarkers is most important to improve the clinical management of RCC and reduce the level of mortality.Area covered: For the detection of RCC at an early stage; a new branch of omics technology - metabolomics - has been introduced. Mainly two techniques (mass spectrometry and nuclear magnetic resonance spectroscopy) have been exploited to execute metabolomics. Precisely, metabolomics showed promising and powerful approach to identify novel RCC biomarker. The present review discussed and the literature search to narrate the outcomes of the past 10 years of studies related to RCC pathophysiology, metabolomics, advancements, and shortcomings.Expert opinion: Although, compared to mass spectrometric tactic, nuclear magnetic resonance is moving fast to achieve the aim and in vivo application for diagnosis and management of RCC, metabolomics-based research in RCC is still in its infancy stage.

Cutting Edge: ROR1/CD19 Receptor Complex Promotes Growth of Mantle Cell Lymphoma Cells Independently of the B Cell Receptor-BTK Signaling Pathway.

Inhibitors of Bruton tyrosine kinase (BTK), a kinase downstream of BCR, display remarkable activity in a subset of mantle cell lymphoma (MCL) patients, but the drug resistance remains a considerable challenge. In this study, we demonstrate that aberrant expression of ROR1 (receptor tyrosine kinase-like orphan receptor 1), seen in a large subset of MCL, results in BCR/BTK-independent signaling and growth of MCL cells. ROR1 forms a functional complex with CD19 to persistently activate the key cell signaling pathways PI3K-AKT and MEK-ERK in the BCR/BTK-independent manner. This study demonstrates that ROR1/CD19 complex effectively substitutes for BCR-BTK signaling to promote activation and growth of MCL cells. Therefore, ROR1 expression and activation may represent a novel mechanism of resistance to inhibition of BCR/BTK signaling in MCL. Our results provide a rationale to screen MCL patients for ROR1 expression and to consider new therapies targeting ROR1 and/or CD19 or their downstream signaling pathways for MCL-expressing ROR1.

Metabolic Detection of Bruton's Tyrosine Kinase Inhibition in Mantle Cell Lymphoma Cells.

Current methods to evaluate effects of kinase inhibitors in cancer are suboptimal. Analysis of changes in cancer metabolism in response to the inhibitors creates an opportunity for better understanding of the interplay between cell signaling and metabolism and, from the translational perspective, potential early evaluation of response to the inhibitors as well as treatment optimization. We performed genomic, metabolomic, and fluxomic analyses to evaluate the mechanism of action of the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib (IBR) in mantle cell lymphoma (MCL) cells. Our comprehensive analysis of the data generated by these diverse technologies revealed that IBR profoundly affected key metabolic pathways in IBR-sensitive cells including glycolysis, pentose phosphate pathway, TCA cycle, and glutaminolysis while having much less effects on IBR-poorly responsive cells. Changes in 1H magnetic resonance spectroscopy (MRS)-detectable lactate and alanine concentrations emerged as promising biomarkers of response and resistance to IBR as demonstrated from experiments on various MCL cell lines. The metabolic network analysis on the 13C MRS and 13C LC/MS experimental data provided quantitative estimates of various intracellular fluxes and energy contributions. Glutaminolysis contributed over 50% of mitochondrial ATP production. Administration of the glutaminase inhibitor CB-839 induced growth suppression of the IBR-poorly responsive cells. IMPLICATIONS: Our study demonstrates application of the advanced metabolomic/fluxomic techniques for comprehensive, precise, and prompt evaluations of the effects of kinase inhibition in MCL cells and has strong translational implications by potentially permitting early evaluation of cancer patient response versus resistance to kinase inhibitors and on design of novel therapies for overcoming the resistance.

Optical Redox Imaging of Lonidamine Treatment Response of Melanoma Cells and Xenografts.

PURPOSE: Fluorescence of co-enzyme reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins (Fp) provides a sensitive measure of the mitochondrial redox state and cellular metabolism. By imaging NADH and Fp, we investigated the utility of optical redox imaging (ORI) to monitor cellular metabolism and detect early metabolic response to cancer drugs. PROCEDURES: We performed ORI of human melanoma DB-1 cells in culture and DB-1 mouse xenografts to detect the redox response to lonidamine (LND) treatment. RESULTS: For cultured cells, LND treatment for 45 min significantly lowered NADH levels with no significant change in Fp, resulting in a significant increase in the Fp redox ratio (Fp/(NADH+Fp)); 3-h prolonged treatment led to a decrease in NADH and an increase in Fp and a more oxidized redox state compared to control. Significant decrease in the mitochondrial redox capacity of LND-treated cells was observed for the first time. For xenografts, 45-min LND treatment resulted in a significant reduction of NADH content, no significant changes in Fp content, and a trend of increase in the Fp redox ratio. Intratumor redox heterogeneity was observed in both control and LND-treated groups. CONCLUSION: Our results support the utility of ORI for evaluating cellular metabolism and monitoring early metabolic response to cancer drugs.

Effect of Differences in Metabolic Activity of Melanoma Models on Response to Lonidamine plus Doxorubicin.

Lonidamine (LND), a metabolic modulator, sensitizes DB-1 human melanoma to doxorubicin (DOX) chemotherapy by acidifying and de-energizing the tumor. This report compares the effects of LND on two human melanoma lines, DB-1 and WM983B, which exhibit different metabolic properties. Using liquid chromatography mass spectrometry and Seahorse analysis, we show that DB-1 was more glycolytic than WM983B in vitro. 31P magnetic resonance spectroscopy (MRS) indicates that LND (100 mg/kg, i.p.) induces similar selective acidification and de-energization of WM983B xenografts in immunosuppressed mice. Over three hours, intracellular pH (pHi) of WM983B decreased from 6.91 ± 0.03 to 6.59 ± 0.10 (p = 0.03), whereas extracellular pH (pHe) of this tumor changed from 7.03 ± 0.05 to 6.89 ± 0.06 (p = 0.19). A decline in bioenergetics (ß-NTP/Pi) of 55 ± 5.0% (p = 0.03) accompanied the decline in pHi of WM983B. Using 1H MRS with a selective multiquantum pulse sequence and Hadamard localization, we show that LND induced a significant increase in tumor lactate levels (p < 0.01). LND pre-treatment followed by DOX (10 mg/kg, i.v.) produced a growth delay of 13.7 days in WM983B (p < 0.01 versus control), a growth delay significantly smaller than the 25.4 days that occurred with DB-1 (p = 0.03 versus WM983B). Differences in relative levels of glycolysis may produce differential therapeutic responses of DB-1 and WM983B melanomas.

Glutamate-Weighted Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Detects Glutaminase Inhibition in a Mouse Model of Triple-Negative Breast Cancer.

Glutamate is an important metabolite of glutaminolysis, a metabolic pathway used by many aggressive cancers, including triple-negative breast cancer (TNBC). With the exception of the brain, in vivo detection of glutamate in tissues using 1H magnetic resonance spectroscopy (MRS) is challenging. Compared with MRS, glutamate-weighted chemical exchange saturation transfer MR imaging (GluCEST MRI) offers a more sensitive detection mechanism that is free of glutamine interference. Here, we developed a robust, highly repeatable GluCEST MRI protocol in mice bearing human TNBC xenografts and treated with a potent glutaminase inhibitor, CB-839. In paired studies, treatment with CB-839 for 2 days reduced the GluCEST asymmetry value compared with baseline (P < 0.05, n = 10). The absolute change of the GluCEST asymmetry value was -2.5 percent points after CB-839 treatment versus +0.3 after vehicle (P < 0.01). Correspondingly, treatment with CB-839 reduced tumor glutamate concentrations by 1.5 mmol/L, consistent with prior calibration between changes of the GluCEST value versus tissue glutamate concentration; CB-839, however, did not change tumor intracellular pH. These results demonstrate in a mouse model of breast cancer the utility of GluCEST MRI to detect the early response to glutaminase inhibition.Significance: A sensitive method enables noninvasive detection of tumor response to inhibitors of glutamine metabolism. Cancer Res; 78(19); 5521-6. ©2018 AACR.