1H MRS detects polyunsaturated fatty acid accumulation during gene therapy of glioma: implications for the in vivo detection of apoptosis

A silent echo-planar spectroscopic imaging readout with high spectral bandwidth MRSI using an ultrasonic gradient axis

PURPOSE

We present a novel silent echo-planar spectroscopic imaging (EPSI) readout, which uses an ultrasonic gradient insert to accelerate MRSI while producing a high spectral bandwidth (20 kHz) and a low sound level.

METHODS

The ultrasonic gradient insert consisted of a single-axis (z-direction) plug-and-play gradient coil, powered by an audio amplifier, and produced 40 mT/m at 20 kHz. The silent EPSI readout was implemented in a phase-encoded MRSI acquisition. Here, the additional spatial encoding provided by this silent EPSI readout was used to reduce the number of phase-encoding steps. Spectroscopic acquisitions using phase-encoded MRSI, a conventional EPSI-readout, and the silent EPSI readout were performed on a phantom containing metabolites with resonance frequencies in the ppm range of brain metabolites (0-4 ppm). These acquisitions were used to determine sound levels, showcase the high spectral bandwidth of the silent EPSI readout, and determine the SNR efficiency and the scan efficiency.

RESULTS

The silent EPSI readout featured a 19-dB lower sound level than a conventional EPSI readout while featuring a high spectral bandwidth of 20 kHz without spectral ghosting artifacts. Compared with phase-encoded MRSI, the silent EPSI readout provided a 4.5-fold reduction in scan time. In addition, the scan efficiency of the silent EPSI readout was higher (82.5% vs. 51.5%) than the conventional EPSI readout.

CONCLUSIONS

We have for the first time demonstrated a silent spectroscopic imaging readout with a high spectral bandwidth and low sound level. This sound reduction provided by the silent readout is expected to have applications in sound-sensitive patient groups, whereas the high spectral bandwidth could benefit ultrahigh-field MR systems.

Lipid droplets provide metabolic flexibility for cancer progression

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation of LDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Early pseudoprogression and progression lesions in glioblastoma patients are both metabolically heterogeneous

The standard treatment in glioblastoma includes maximal safe resection followed by concomitant radiotherapy plus chemotherapy and adjuvant temozolomide. The first follow-up study to evaluate treatment response is performed 1 month after concomitant treatment, when contrast-enhancing regions may appear that can correspond to true progression or pseudoprogression. We retrospectively evaluated 31 consecutive patients at the first follow-up after concomitant treatment to check whether the metabolic pattern assessed with multivoxel MRS was predictive of treatment response 2 months later. We extracted the underlying metabolic patterns of the contrast-enhancing regions with a blind-source separation method and mapped them over the reference images. Pattern heterogeneity was calculated using entropy, and association between patterns and outcomes was measured with Cramér's V. We identified three distinct metabolic patterns-proliferative, necrotic, and responsive, which were associated with status 2 months later. Individually, 70% of the patients showed metabolically heterogeneous patterns in the contrast-enhancing regions. Metabolic heterogeneity was not related to the regions' size and only stable patients were less heterogeneous than the rest. Contrast-enhancing regions are also metabolically heterogeneous 1 month after concomitant treatment. This could explain the reported difficulty in finding robust pseudoprogression biomarkers.

Correlation of MR-Based Metabolomics and Molecular Profiling in the Tumor Microenvironment of Temozolomide-Treated Orthotopic GL261 Glioblastoma in Mice

The tumor microenvironment in glioblastoma (GB) is considered to be "cold", i.e., the fraction of cytotoxic T cells, for instance, is low. Instead, macrophages are the major immune cell population in GB, which stem either from tissue response (resident microglia) or recruitment of macrophages from the periphery, thereby undergoing tumor-dependent "imprinting" mechanisms by which macrophages can adapt a tumor-supportive phenotype. In this regard, it is important to describe the nature of macrophages associated with GB, in particular under therapy conditions using the gold standard chemotherapy drug temozolomide (TMZ). Here, we explored the suitability of combining information from in vivo magnetic resonance spectroscopic (MRS) approaches (metabolomics) with in vitro molecular analyses to assess therapy response and characterize macrophage populations in mouse GB using an isogenic GL261 model. For macrophage profiling, expression levels of matrix metalloproteinases (MMPs) and A disintegrin and metalloproteinases (ADAMs) were determined, since their gene products affect macrophage-tumor cell communication by extensive cleavage of immunomodulatory membrane proteins, such as PD-L1. In tumor mice with an overall therapy response, expression of genes encoding the proteases ADAM8, ADAM10, and ADAM17 was increased and might contribute to the immunosuppressive phenotype of GB and immune cells. In tumors responding to therapy, expression levels of ADAM8 were upregulated by TMZ, and higher levels of PD-L1 were correlated significantly. Using a CRISPR/Cas9 knockout of ADAM8 in GL261 cells, we demonstrated that soluble PD-L1 (sPD-L1) is only generated in the presence of ADAM8. Moreover, primary macrophages from WT and ADAM8-deficient mice showed ADAM8-dependent release of sPD-L1, independent of the macrophage polarization state. Since ADAM8 expression is induced in responding tumors and PD-L1 shedding is likely to decrease the anti-tumor activities of T-cells, we conclude that immunotherapy resistance is caused, at least in part, by the increased presence of proteases, such as ADAM8.

Tracking Therapy Response in Glioblastoma Using 1D Convolutional Neural Networks

BACKGROUND

Glioblastoma (GB) is a malignant brain tumour that is challenging to treat, often relapsing even after aggressive therapy. Evaluating therapy response relies on magnetic resonance imaging (MRI) following the Response Assessment in Neuro-Oncology (RANO) criteria. However, early assessment is hindered by phenomena such as pseudoprogression and pseudoresponse. Magnetic resonance spectroscopy (MRS/MRSI) provides metabolomics information but is underutilised due to a lack of familiarity and standardisation.

METHODS

This study explores the potential of spectroscopic imaging (MRSI) in combination with several machine learning approaches, including one-dimensional convolutional neural networks (1D-CNNs), to improve therapy response assessment. Preclinical GB (GL261-bearing mice) were studied for method optimisation and validation.

RESULTS

The proposed 1D-CNN models successfully identify different regions of tumours sampled by MRSI, i.e., normal brain (N), control/unresponsive tumour (T), and tumour responding to treatment (R). Class activation maps using Grad-CAM enabled the study of the key areas relevant to the models, providing model explainability. The generated colour-coded maps showing the N, T and R regions were highly accurate (according to Dice scores) when compared against ground truth and outperformed our previous method.

CONCLUSIONS

The proposed methodology may provide new and better opportunities for therapy response assessment, potentially providing earlier hints of tumour relapsing stages.

Exploring the Potential of Broadband Complementary Metal Oxide Semiconductor Micro-Coil Nuclear Magnetic Resonance for Environmental Research

With sensitivity being the Achilles' heel of nuclear magnetic resonance (NMR), the superior mass sensitivity offered by micro-coils can be an excellent choice for tiny, mass limited samples such as eggs and small organisms. Recently, complementary metal oxide semiconductor (CMOS)-based micro-coil transceivers have been reported and demonstrate excellent mass sensitivity. However, the ability of broadband CMOS micro-coils to study heteronuclei has yet to be investigated, and here their potential is explored within the lens of environmental research. Eleven nuclei including 7Li, 19F, 31P and, 205Tl were studied and detection limits in the low to mid picomole range were found for an extended experiment. Further, two environmentally relevant samples (a sprouting broccoli seed and a D. magna egg) were successfully studied using the CMOS micro-coil system. 13C NMR was used to help resolve broad signals in the 1H spectrum of the 13C enriched broccoli seed, and steady state free precession was used to improve the signal-to-noise ratio by a factor of six. 19F NMR was used to track fluorinated contaminants in a single D. magna egg, showing potential for studying egg-pollutant interactions. Overall, CMOS micro-coil NMR demonstrates significant promise in environmental research, especially when the future potential to scale to multiple coil arrays (greatly improving throughput) is considered.

Ensheathing glia promote increased lifespan and healthy brain aging

Glia have an emergent role in brain aging and disease. In the Drosophila melanogaster brain, ensheathing glia function as phagocytic cells and respond to acute neuronal damage, analogous to mammalian microglia. We previously reported changes in glia composition over the life of ants and fruit flies, including a decline in the relative proportion of ensheathing glia with time. How these changes influence brain health and life expectancy is unknown. Here, we show that ensheathing glia but not astrocytes decrease in number during Drosophila melanogaster brain aging. The remaining ensheathing glia display dysregulated expression of genes involved in lipid metabolism and apoptosis, which may lead to lipid droplet accumulation, cellular dysfunction, and death. Inhibition of apoptosis rescued the decline of ensheathing glia with age, improved the neuromotor performance of aged flies, and extended lifespan. Furthermore, an expanded ensheathing glia population prevented amyloid-beta accumulation in a fly model of Alzheimer's disease and delayed the premature death of the diseased animals. These findings suggest that ensheathing glia play a vital role in regulating brain health and animal longevity.

Metabolic changes in glioblastomas in response to choline kinase inhibition: In vivo MRS in rodent models

Changes in glioblastoma (GBM) metabolism was investigated in response to JAS239, a choline kinase inhibitor, using MRS. In addition to the inhibition of phosphocholine synthesis, we investigated changes in other key metabolic pathways associated with GBM progression and treatment response. Three syngeneic rodent models of GBM were used: F98 (N = 12) and 9L (N = 8) models in rats and GL261 (N = 10) in mice. Rodents were intracranially injected with GBM cells in the right cortex and tumor growth was monitored using T₂ -weighted images. Animals were treated once daily with intraperitoneal injections of 4 mg/kg JAS239 (F98 rats, n = 6; 9L rats, n = 6; GL261 mice, n = 5) or saline (control group, F98 rats, n = 6; 9L rats, n = 2; GL261 mice, n = 5) for five consecutive days. Single voxel spectra were acquired on Days 0 (T0, baseline) and 6 (T6, end of treatment) from the tumor as well as the contralateral normal brain using a PRESS sequence. Changes in metabolite ratios (tCho/tCr, tCho/NAA, mI/tCr, Glx/tCr and (Lip + Lac)/Cr) were used to assess metabolic pathway alterations in response to JAS239. Tumor growth arrest was noted in all models in response to JAS239 treatment compared with saline-treated animals, with a significant reduction (p < 0.05) in the F98 model. A reduction in tCho/tCr was observed with JAS239 treatment in all GBM models, indicating reduced phospholipid metabolism, with the highest reduction in 9L followed by GL261 and F98 tumors. A significant reduction (p < 0.05) in the tCho/NAA ratio was observed in the 9L model. A significant reduction in mI/tCr (p < 0.05) was found in JAS239-treated F98 tumors compared with the saline-treated animals. A non-significant trend of reduction in Glx/tCr was observed only in F98 and 9L tumors. JAS239-treated F98 tumors also showed a significant increase in Lip + Lac (p < 0.05), indicating increased cell death. This study demonstrated the utility of MRS in assessing metabolic changes in GBM in response to choline kinase inhibition.

Pien Tze Huang regulates phosphorylation of metabolic enzymes in mice of hepatocellular carcinoma

The Chinese medicine formula Pien Tze Huang (PZH) has been applied to the treatment of various diseases, the reported anti-tumor mechanisms included regulation of inflammation-associated cytokine secretion and cancer growth pathways. However, the potential influence of PZH on tumor metabolism remains unclear. This study aimed to investigate the global effect of PZH on hepatocellular carcinoma (HCC) compared with the anti-tumor agent sorafenib based on tandem mass tag (TMT) label proteomic and phosphoproteomic analysis in addition to parallel reaction monitoring (PRM) verification. It was observed that PZH could inhibit tumor weight by 59-69% in different concentrations. TMT proteomic studies indicated that fructose/mannose metabolism and glucagon signaling pathway in PZH group, and arachidonic acid metabolism and PPAR signaling pathway in sorafenib group, were significantly enriched, while glycolysis/gluconeogenesis pathway was found to be enriched remarkably both in PZH and sorafenib groups in TMT phosphoproteomic study. PRM verification further indicated that both PZH and sorafenib could down-regulate phosphorylations of the glycolytic enzymes phosphofructokinases 1, fructose-bisphosphate Aldolase A, phosphoglycerate mutase 2 and lactate dehydrogenase A chain, while phosphorylations of long chain fatty acid CoA ligase in fatty acid activation and acetyl-coenzyme A synthetase in glycolysis were significantly inhibited by PZH and sorafenib, respectively. This study proposed that PZH shared a similar anti-tumor mechanism of metabolic regulation to sorafenib, but differed in the regulation of some metabolic nodes. This is the first time to uncover the relationship between the anti-tumor effect of PZH and metabolic related enzymes, which distinguished from the known mechanisms of PZH. These data provided the potential molecular basis for PZH acting as a therapeutic drug for HCC, and offered cues of manipulation on Warburg effect under the treatment of PZH.

Establishing Imaging Biomarkers of Host Immune System Efficacy during Glioblastoma Therapy Response: Challenges, Obstacles and Future Perspectives

This hypothesis proposal addresses three major questions: (1) Why do we need imaging biomarkers for assessing the efficacy of immune system participation in glioblastoma therapy response? (2) Why are they not available yet? and (3) How can we produce them? We summarize the literature data supporting the claim that the immune system is behind the efficacy of most successful glioblastoma therapies but, unfortunately, there are no current short-term imaging biomarkers of its activity. We also discuss how using an immunocompetent murine model of glioblastoma, allowing the cure of mice and the generation of immune memory, provides a suitable framework for glioblastoma therapy response biomarker studies. Both magnetic resonance imaging and magnetic resonance-based metabolomic data (i.e., magnetic resonance spectroscopic imaging) can provide non-invasive assessments of such a system. A predictor based in nosological images, generated from magnetic resonance spectroscopic imaging analyses and their oscillatory patterns, should be translational to clinics. We also review hurdles that may explain why such an oscillatory biomarker was not reported in previous imaging glioblastoma work. Single shot explorations that neglect short-term oscillatory behavior derived from immune system attack on tumors may mislead actual response extent detection. Finally, we consider improvements required to properly predict immune system-mediated early response (1–2 weeks) to therapy. The sensible use of improved biomarkers may enable translatable evidence-based therapeutic protocols, with the possibility of extending preclinical results to human patients.

NMR spectroscopy of a single mammalian early stage embryo

The resolving power, chemical sensitivity and non-invasive nature of NMR have made it an established technique for in vivo studies of large organisms both for research and clinical applications. NMR would clearly be beneficial for analysis of entities at the microscopic scale of about 1 nL (the nanoliter scale), typical of early development of mammalian embryos, microtissues and organoids: the scale where the building blocks of complex organisms could be observed. However, the handling of such small samples (about 100 µm) and sensitivity issues have prevented a widespread adoption of NMR. In this article we show how these limitations can be overcome to obtain NMR spectra of a mammalian embryo in its early stage. To achieve this we employ ultra-compact micro-chip technologies in combination with 3D-printed micro-structures. Such device is packaged for use as plug & play sensor and it shows sufficient sensitivity to resolve NMR signals from individual bovine pre-implantation embryos. The embryos in this study are obtained through In Vitro Fertilization (IVF) techniques, transported cryopreserved to the NMR laboratory, and measured shortly after thawing. In less than 1 h these spherical samples of just 130-190 µm produce distinct spectral peaks, largely originating from lipids contained inside them. We further observe how the spectra vary from one sample to another despite their optical and morphological similarities, suggesting that the method can further develop into a non-invasive embryo assay for selection prior to embryo transfer.

Assessing fatty acid-induced lipotoxicity and its therapeutic potential in glioblastoma using stimulated Raman microscopy

Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. The effectiveness of traditional therapies for GBM is limited and therefore new therapies are highly desired. Previous studies show that lipid metabolism reprogramming may be a potential therapeutic target in GBM. This study aims to evaluate the therapeutic potential of free fatty acid-induced lipotoxicity for the suppression of glioma growth. U87 glioma cells are treated with three fatty acids (FAs): palmitic acid (PA), oleic acid (OA), and eicosapentaenoic acid (EPA). Uptake of the FAs and formation of lipid droplets (LDs) are imaged and quantified using a lab-built stimulated Raman scattering (SRS) microscope. Our results show that a supply of 200 µM PA, OA, and EPA leads to efficient LDs accumulation in glioma cells. We find that inhibition of triglycerides (TAGs) synthesis depletes LDs and enhances lipotoxicity, which is evidenced by the reduced cell proliferation rates. In particular, our results suggest that EPA treatment combined with depletion of LDs significantly reduces the survival rate of glioma cells by more than 50%, indicating the therapeutic potential of this approach. Future work will focus on understanding the metabolic mechanism of EPA-induced lipotoxicity to further enhance its anticancer effects.

Fat Composition Measured by Proton Spectroscopy: A Breast Cancer Tumor Marker?

Altered metabolism including lipids is an emerging hallmark of breast cancer. The purpose of this study was to investigate if breast cancers exhibit different magnetic resonance spectroscopy (MRS)-based lipid composition than normal fibroglandular tissue (FGT). MRS spectra, using the stimulated echo acquisition mode sequence, were collected with a 3T scanner from patients with suspicious lesions and contralateral normal tissue. Fat peaks at 1.3 + 1.6 ppm (L13 + L16), 2.1 + 2.3 ppm (L21 + L23), 2.8 ppm (L28), 4.1 + 4.3 ppm (L41 + L43), and 5.2 + 5.3 ppm (L52 + L53) were quantified using LCModel software. The saturation index (SI), number of double bods (NBD), mono and polyunsaturated fatty acids (MUFA and PUFA), and mean chain length (MCL) were also computed. Results showed that mean concentrations of all lipid metabolites and PUFA were significantly lower in tumors compared with that of normal FGT (p ≤ 0.002 and 0.04, respectively). The measure best separating normal and tumor tissues after adjusting with multivariable analysis was L21 + L23, which yielded an area under the curve of 0.87 (95% CI: 0.75–0.98). Similar results were obtained between HER2 positive versus HER2 negative tumors. Hence, MRS-based lipid measurements may serve as independent variables in a multivariate approach to increase the specificity of breast cancer characterization.

Unraveling response to temozolomide in preclinical GL261 glioblastoma with MRI/MRSI using radiomics and signal source extraction

Glioblastoma is the most frequent aggressive primary brain tumor amongst human adults. Its standard treatment involves chemotherapy, for which the drug temozolomide is a common choice. These are heterogeneous and variable tumors which might benefit from personalized, data-based therapy strategies, and for which there is room for improvement in therapy response follow-up, investigated with preclinical models. This study addresses a preclinical question that involves distinguishing between treated and control (untreated) mice bearing glioblastoma, using machine learning techniques, from magnetic resonance-based data in two modalities: MRI and MRSI. It aims to go beyond the comparison of methods for such discrimination to provide an analytical pipeline that could be used in subsequent human studies. This analytical pipeline is meant to be a usable and interpretable tool for the radiology expert in the hope that such interpretation helps revealing new insights about the problem itself. For that, we propose coupling source extraction-based and radiomics-based data transformations with feature selection. Special attention is paid to the generation of radiologist-friendly visual nosological representations of the analyzed tumors.

Conformational States of the Cytoprotective Protein Bcl-xL

Bcl-xL is a major inhibitor of apoptosis, a fundamental homeostatic process of programmed cell death that is highly conserved across evolution. Because it plays prominent roles in cancer, Bcl-xL is a major target for anticancer therapy and for studies aimed at understanding its structure and activity. Although Bcl-xL is active primarily at intracellular membranes, most studies have focused on soluble forms of the protein lacking both the membrane-anchoring C-terminal tail and the intrinsically disordered loop, and this has resulted in a fragmented view of the protein's biological activity. Here, we describe the conformation of full-length Bcl-xL. Using NMR spectroscopy, molecular dynamics simulations, and isothermal titration calorimetry, we show how the three structural elements affect the protein's structure, dynamics, and ligand-binding activity in both its soluble and membrane-anchored states. The combined data provide information about the molecular basis for the protein's functionality and a view of its complex molecular mechanisms.

Lipid-Based Nanovesicles for Simultaneous Intracellular Delivery of Hydrophobic, Hydrophilic, and Amphiphilic Species

Lipid nanovesicles (NVs) are the first nanoformulation that entered the clinical use in oncology for the treatment of solid tumors. They are indeed versatile systems which can be loaded with either hydrophobic or hydrophilic molecules, for both imaging and drug delivery, and with high biocompatibility, and limited immunogenicity. In the present work, NVs with a lipid composition resembling that of natural vesicles were prepared using the ultrasonication method. The NVs were successfully loaded with fluorophores molecules (DOP-F-DS and a fluorescent protein), inorganic nanoparticles (quantum dots and magnetic nanoparticles), and anti-cancer drugs (SN-38 and doxorubicin). The encapsulation of such different molecules showed the versatility of the developed systems. The size of the vesicles varied from 100 up to 300 nm depending on the type of loaded species, which were accommodated either into the lipid bilayer or into the aqueous core according to their hydrophobic or hydrophilic nature. Viability assays were performed on cellular models of breast cancer (MCF-7 and MDA-MB-231). Results showed that NVs with encapsulated both drugs simultaneously led to a significant reduction of the cellular activity (up to 22%) compared to the free drugs or to the NVs encapsulated with only one drug. Lipidomic analysis suggested that the mechanism of action of the drugs is the same, whether they are free or encapsulated, but administration of the drugs by means of nanovesicles is more efficient in inducing cellular damage, likely because of a quicker internalization and a sustained release. This study confirms the versatility and the potential of lipid NVs for cancer treatment, as well as the validity of the ultrasound preparation method for their preparation.

Lipid droplets: platforms with multiple functions in cancer hallmarks

Lipid droplets (also known as lipid bodies) are lipid-rich, cytoplasmic organelles that play important roles in cell signaling, lipid metabolism, membrane trafficking, and the production of inflammatory mediators. Lipid droplet biogenesis is a regulated process, and accumulation of these organelles within leukocytes, epithelial cells, hepatocytes, and other nonadipocyte cells is a frequently observed phenotype in several physiologic or pathogenic situations and is thoroughly described during inflammatory conditions. Moreover, in recent years, several studies have described an increase in intracellular lipid accumulation in different neoplastic processes, although it is not clear whether lipid droplet accumulation is directly involved in the establishment of these different types of malignancies. This review discusses current evidence related to the biogenesis, composition and functions of lipid droplets related to the hallmarks of cancer: inflammation, cell metabolism, increased proliferation, escape from cell death, and hypoxia. Moreover, the potential of lipid droplets as markers of disease and targets for novel anti-inflammatory and antineoplastic therapies will be discussed.

Imaging of cancer lipid metabolism in response to therapy

Lipids represent a diverse array of molecules essential to the cell's structure, defense, energy, and communication. Lipid metabolism can often become dysregulated during tumor development. During cancer therapy, targeted inhibition of cell proliferation can likewise cause widespread and drastic changes in lipid composition. Molecular imaging techniques have been developed to monitor altered lipid profiles as a biomarker for cancer diagnosis and treatment response. For decades, MRS has been the dominant non-invasive technique for studying lipid metabolite levels. Recent insights into the oncogenic transformations driving changes in lipid metabolism have revealed new mechanisms and signaling molecules that can be exploited using optical imaging, mass spectrometry imaging, and positron emission tomography. These novel imaging modalities have provided researchers with a diverse toolbox to examine changes in lipids in response to a wide array of anticancer strategies including chemotherapy, radiation therapy, signal transduction inhibitors, gene therapy, immunotherapy, or a combination of these strategies. The understanding of lipid metabolism in response to cancer therapy continues to evolve as each therapeutic method emerges, and this review seeks to summarize the current field and areas of unmet needs.

In vivo magnetic resonance imaging of treatment-induced apoptosis

Imaging apoptosis could provide an early and specific means to monitor tumor responses to treatment. To date, despite numerous attempts to develop molecular imaging approaches, there is still no widely-accepted and reliable method for in vivo imaging of apoptosis. We hypothesized that the distinct cellular morphologic changes associated with treatment-induced apoptosis, such as cell shrinkage, cytoplasm condensation, and DNA fragmentation, can be detected by temporal diffusion spectroscopy imaging (TDSI). Cetuximab-induced apoptosis was assessed in vitro and in vivo with cetuximab-sensitive (DiFi) and insensitive (HCT-116) human colorectal cancer cell lines by TDSI. TDSI findings were complemented by flow cytometry and immunohistochemistry. Cell cycle analysis and flow cytometry detected apoptotic cell shrinkage in cetuximab-treated DiFi cells, and significant apoptosis was confirmed by histology. TDSI-derived parameters quantified key morphological changes including cell size decreases during apoptosis in responsive tumors that occurred earlier than gross tumor volume regression. TDSI provides a unique measurement of apoptosis by identifying cellular characteristics, particularly cell shrinkage. The method will assist in understanding the underlying biology of solid tumors and predict tumor response to therapies. TDSI is free of any exogenous agent or radiation, and hence is very suitable to be incorporated into clinical applications.

The effect of FASN inhibition on the growth and metabolism of a cisplatin-resistant ovarian carcinoma model

Overexpression of fatty acid synthase (FASN), a key regulator of the de novo synthesis of fatty acids, has been demonstrated in a variety of cancers and is associated with poor prognosis and increased multidrug resistance. Inhibition of FASN with the anti-obesity drug orlistat has been shown to have significant anti-tumourigenic effects in many cancers, notably breast and prostate. In our study, we investigated whether FASN inhibition using orlistat is an effective adjunctive treatment for ovarian cancers that have become platinum resistant using a cisplatin-resistant ovarian tumour xenograft model in mice. Mice were treated with orlistat or cisplatin or a combination and metabolite analysis and histopathology were performed on the tumours ex vivo. Orlistat decreased tumour fatty acid metabolism by inhibiting FASN, cisplatin reduced fatty acid β-oxidation, and combination treatment delayed tumour growth and induced apoptotic and necrotic cell death in cisplatin-resistant ovarian cancer cells over and above that with either treatment alone. Combination treatment also decreased glutamine metabolism, nucleotide and glutathione biosynthesis and fatty acid β-oxidation. Our data suggest that orlistat chemosensitised platinum-resistant ovarian cancer to treatment with platinum and resulted in enhanced efficacy.

Lipoprotein Particle Formation by Proapoptotic tBid

The interactions of Bcl-2 family proteins with intracellular lipids are essential for the regulation of apoptosis, a mechanism of programmed cell death that is central to the health and development of multicellular organisms. Bid and its caspase-8 cleavage product, tBid, promote the permeabilization of the mitochondrial outer membrane and sequester antiapoptotic Bcl-2 proteins to counter their cytoprotective activity. Bid and tBid also promote lipid exchange, a characteristic trait of apoptosis. Here, we show that tBid is capable of associating with phospholipids to form soluble, nanometer-sized lipoprotein particles that retain binding affinity for the antiapoptotic protein Bcl-xL. The tBid lipoprotein particles form with a lipid/protein stoichiometry in the range of 20/1 and have a diameter of ∼11.5 nm. Lipoparticle-bound tBid retains an α-helical structure and binds Bcl-xL through its third Bcl-2 homology motif, forming a soluble, lipid-associated heteroprotein complex. The results shed light on the role of lipids in mediating Bcl-2 protein mobility and interactions.

Autophagy in Traumatic Brain Injury: A New Target for Therapeutic Intervention

Traumatic brain injury (TBI) is one of the most devastating forms of brain injury. Many pathological mechanisms such as oxidative stress, apoptosis and inflammation all contribute to the secondary brain damage and poor outcomes of TBI. Current therapies are often ineffective and poorly tolerated, which drive the explore of new therapeutic targets for TBI. Autophagy is a highly conserved intracellular mechanism during evolution. It plays an important role in elimination abnormal intracellular proteins or organelles to maintain cell stability. Besides, autophagy has been researched in various models including TBI. Previous studies have deciphered that regulation of autophagy by different molecules and pathways could exhibit anti-oxidative stress, anti-apoptosis and anti-inflammation effects in TBI. Hence, autophagy is a promising target for further therapeutic development in TBI. The present review provides an overview of current knowledge about the mechanism of autophagy, the frequently used methods to monitor autophagy, the functions of autophagy in TBI as well as its potential molecular mechanisms based on the pharmacological regulation of autophagy.

Study of lipid metabolism by estimating the fat fraction in different breast tissues and in various breast tumor sub-types by in vivo 1H MR spectroscopy

PURPOSE

To evaluate the utility of fat fraction (FF) for the differentiation of different breast tissues and in various breast tumor subtypes using in vivo proton (¹H) magnetic resonance spectroscopy (MRS).

METHODS

¹H MRS was performed on 68 malignant, 35 benign, and 30 healthy volunteers at 1.5 T. Malignant breast tissues of patients were characterized into different subtypes based on the differences in the expression of hormone receptors and the FF was calculated. Further, the sensitivity and specificity of FF to differentiate malignant from benign and from normal breast tissues of healthy volunteers was determined using receiver operator curve (ROC) analysis.

RESULTS

A significantly lower FF of malignant (median 0.12; range 0.01-0.70) compared to benign lesions (median 0.28; range 0.02-0.71) and normal breast tissue of healthy volunteers (median 0.39; range 0.06-0.76) was observed. No significant difference in FF was seen between benign lesions and normal breast tissues of healthy volunteers. Sensitivity and specificity of 75% and 68.6%, respectively was obtained to differentiate malignant from benign lesions. For the differentiation of malignant from healthy breast tissues, 76% sensitivity and 74.5% specificity was achieved. Higher FF was seen in patients with ER-/PR- status as compared to ER+/PR+ patients. Similarly, FF of HER2neu+ tumors were significantly higher than in HER2neu- breast tumors.

CONCLUSION

The results showed the potential of in vivo ¹H MRS in providing insight into the changes in the fat content of different types of breast tissues and in various breast tumor subtypes.

Metabolomics facilitates the discrimination of the specific anti-cancer effects of free- and polymer-conjugated doxorubicin in breast cancer models

Metabolomics is becoming a relevant tool for understanding the molecular mechanisms involved in the response to new drug delivery systems. The applicability of this experimental approach to cell cultures and animal models makes metabolomics a useful tool for establishing direct connections between in vitro and in vivo data, thus providing a reliable platform for the characterization of chemotherapeutic agents. Herein, we used metabolomic profiles based on nuclear magnetic resonance (NMR) spectroscopy to evaluate the biochemical pathways involved in the response to a chemotherapeutic anthracycline drug (Doxorubicin, Dox) and an N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-conjugated form (HPMA-Dox) in an in vitro cell culture model and an in vivo orthotopic breast cancer model. We also used protein expression and flow cytometry studies to obtain a better coverage of the biochemical alterations associated with the administration of these compounds. The overall analysis revealed that polymer conjugation leads to increased apoptosis, reduced glycolysis, and reduced levels of phospholipids when compared to the free chemotherapeutic drug. Our results represent a first step in the application of integrated in vitro and in vivo metabolomic studies to the evaluation of drug delivery systems.

Near infrared fluorescent imaging of choline kinase alpha expression and inhibition in breast tumors

Choline kinase alpha (ChoKα) overexpression is associated with an aggressive tumor phenotype. ChoKα inhibitors induce apoptosis in tumors, however validation of their specificity is difficult in vivo. We report the use of optical imaging to assess ChoKα status in cells and in vivo using JAS239, a carbocyanine-based ChoKα inhibitor with inherent near infrared fluorescence. JAS239 attenuated choline phosphorylation and viability in a panel of human breast cancer cell lines. Antibody blockade prevented cellular retention of JAS239 indicating direct interaction with ChoKα independent of the choline transporters and catabolic choline pathways. In mice bearing orthotopic MCF7 breast xenografts, optical imaging with JAS239 distinguished tumors overexpressing ChoKα from their empty vector counterparts and delineated tumor margins. Pharmacological inhibition of ChoK by the established inhibitor MN58b led to a growth inhibition in 4175-Luc+ tumors that was accompanied by concomitant reduction in JAS239 uptake and decreased total choline metabolite levels as measured using magnetic resonance spectroscopy. At higher therapeutic doses, JAS239 was as effective as MN58b at arresting tumor growth and inducing apoptosis in MDA-MB-231 tumors, significantly reducing tumor choline below baseline levels without observable systemic toxicity. These data introduce a new method to monitor therapeutically effective inhibitors of choline metabolism in breast cancer using a small molecule companion diagnostic.

Metabolomics of Therapy Response in Preclinical Glioblastoma: A Multi-Slice MRSI-Based Volumetric Analysis for Noninvasive Assessment of Temozolomide Treatment

Glioblastoma (GBM) is the most common aggressive primary brain tumor in adults, with a short survival time even after aggressive therapy. Non-invasive surrogate biomarkers of therapy response may be relevant for improving patient survival. Previous work produced such biomarkers in preclinical GBM using semi-supervised source extraction and single-slice Magnetic Resonance Spectroscopic Imaging (MRSI). Nevertheless, GBMs are heterogeneous and single-slice studies could prevent obtaining relevant information. The purpose of this work was to evaluate whether a multi-slice MRSI approach, acquiring consecutive grids across the tumor, is feasible for preclinical models and may produce additional insight into therapy response. Nosological images were analyzed pixel-by-pixel and a relative responding volume, the Tumor Responding Index (TRI), was defined to quantify response. Heterogeneous response levels were observed and treated animals were ascribed to three arbitrary predefined groups: high response (HR, n = 2), TRI = 68.2 ± 2.8%, intermediate response (IR, n = 6), TRI = 41.1 ± 4.2% and low response (LR, n = 2), TRI = 13.4 ± 14.3%, producing therapy response categorization which had not been fully registered in single-slice studies. Results agreed with the multi-slice approach being feasible and producing an inverse correlation between TRI and Ki67 immunostaining. Additionally, ca. 7-day oscillations of TRI were observed, suggesting that host immune system activation in response to treatment could contribute to the responding patterns detected.

In vivo imaging techniques: a new era for histochemical analysis

In vivo imaging techniques can be integrated with classical histochemistry to create an actual histochemistry of water. In particular, Magnetic Resonance Imaging (MRI), an imaging technique primarily used as diagnostic tool in clinical/preclinical research, has excellent anatomical resolution, unlimited penetration depth and intrinsic soft tissue contrast. Thanks to the technological development, MRI is not only capable to provide morphological information but also and more interestingly functional, biophysical and molecular. In this paper we describe the main features of several advanced imaging techniques, such as MRI microscopy, Magnetic Resonance Spectroscopy, functional MRI, Diffusion Tensor Imaging and MRI with contrast agent as a useful support to classical histochemistry.

MRSI-based molecular imaging of therapy response to temozolomide in preclinical glioblastoma using source analysis

Characterization of glioblastoma (GB) response to treatment is a key factor for improving patients' survival and prognosis. MRI and magnetic resonance spectroscopic imaging (MRSI) provide morphologic and metabolic profiles of GB but usually fail to produce unequivocal biomarkers of response. The purpose of this work is to provide proof of concept of the ability of a semi-supervised signal source extraction methodology to produce images with robust recognition of response to temozolomide (TMZ) in a preclinical GB model. A total of 38 female C57BL/6 mice were used in this study. The semi-supervised methodology extracted the required sources from a training set consisting of MRSI grids from eight GL261 GBs treated with TMZ, and six control untreated GBs. Three different sources (normal brain parenchyma, actively proliferating GB and GB responding to treatment) were extracted and used for calculating nosologic maps representing the spatial response to treatment. These results were validated with an independent test set (7 control and 17 treated cases) and correlated with histopathology. Major differences between the responder and non-responder sources were mainly related to the resonances of mobile lipids (MLs) and polyunsaturated fatty acids in MLs (0.9, 1.3 and 2.8 ppm). Responding tumors showed significantly lower mitotic (3.3 ± 2.9 versus 14.1 ± 4.2 mitoses/field) and proliferation rates (29.8 ± 10.3 versus 57.8 ± 5.4%) than control untreated cases. The methodology described in this work is able to produce nosological images of response to TMZ in GL261 preclinical GBs and suitably correlates with the histopathological analysis of tumors. A similar strategy could be devised for monitoring response to treatment in patients. Copyright © 2016 John Wiley & Sons, Ltd.

Bacterial-excreted small volatile molecule 2-aminoacetophenone induces oxidative stress and apoptosis in murine skeletal muscle

Oxidative stress induces mitochondrial dysfunction and facilitates apoptosis, tissue damage or metabolic alterations following infection. We have previously discovered that the Pseudomonas aeruginosa (PA) quorum sensing (QS)-excreted small volatile molecule, 2-aminoacetophenone (2-AA), which is produced in infected human tissue, promotes bacterial phenotypes that favor chronic infection, while also compromising muscle function and dampens the pathogen-induced innate immune response, promoting host tolerance to infection. In this study, murine whole-genome expression data have demonstrated that 2-AA affects the expression of genes involved in reactive oxygen species (ROS) homeostasis, thus producing an oxidative stress signature in skeletal muscle. The results of the present study demonstrated that the expression levels of genes involved in apoptosis signaling pathways were upregulated in the skeletal muscle of 2-AA-treated mice. To confirm the results of our transcriptome analysis, we used a novel high-resolution magic-angle-spinning (HRMAS), proton (¹H) nuclear magnetic resonance (NMR) method and observed increased levels of bisallylic methylene fatty acyl protons and vinyl protons, suggesting that 2-AA induces skeletal muscle cell apoptosis. This effect was corroborated by our results demonstrating the downregulation of mitochondrial membrane potential in vivo in response to 2-AA. The findings of the present study indicate that the bacterial infochemical, 2-AA, disrupts mitochondrial functions by inducing oxidative stress and apoptosis signaling and likely promotes skeletal muscle dysfunction, which may favor chronic/persistent infection.

Brain maturation in neonatal rodents is impeded by sevoflurane anesthesia

BACKGROUND

A wealth of data shows neuronal demise after general anesthesia in the very young rodent brain. Herein, the authors apply proton magnetic resonance spectroscopy (1HMRS), testing the hypothesis that neurotoxic exposure during peak synaptogenesis can be tracked via changes in neuronal metabolites.

METHODS

1HMRS spectra were acquired in the brain (thalamus) of neonatal rat pups 24 and 48 h after sevoflurane exposure on postnatal day (PND) 7 and 15 and in unexposed, sham controls. A repeated measure ANOVA was performed to examine whether changes in metabolites were different between exposed and unexposed groups. Sevoflurane-induced neurotoxicity on PND7 was confirmed by immunohistochemistry.

RESULTS

In unexposed PND7 pups (N = 21), concentration of N-acetylaspartate (NAA; [NAA]) increased by 16% from PND8 to PND9, whereas in exposed PND7 pups (N = 19), [NAA] did not change and concentration of glycerophosphorylcholine and phosphorylcholine ([GPC + PCh]) decreased by 25%. In PND15 rats, [NAA] increased from PND16 to PND17 for both the exposed (N = 14) and the unexposed (N = 16) groups. Two-way ANOVA for PND7 pups demonstrated that changes over time observed in [NAA] (P = 0.031) and [GPC + PCh] (P = 0.024) were different between those two groups.

CONCLUSIONS

The authors demonstrated that normal [NAA] increase from PND8 to PND9 was impeded in sevoflurane-exposed rats when exposed at PND7; however, not impeded when exposed on PND15. Furthermore, the authors showed that noninvasive 1HMRS is sufficiently sensitive to detect subtle differences in developmental time trajectory of [NAA]. This is potentially clinically relevant because 1HMRS can be applied across species and may be useful in providing evidence of neurotoxicity in the human neonatal brain.

Magnetic resonance spectroscopy and imaging on fresh human brain tumor biopsies at microscopic resolution

The metabolic composition and concentration knowledge provided by magnetic resonance spectroscopy (MRS) liquid and high-resolution magic angle spinning spectroscopy (HR-MAS) has a relevant impact in clinical practice during magnetic resonance imaging (MRI) monitoring of human tumors. In addition, the combination of morphological and chemical information by MRI and MRS has been particularly useful for diagnosis and prognosis of tumor evolution. MRI spatial resolution reachable in human beings is limited for safety reasons and the demanding necessary conditions are only applicable on experimental model animals. Nevertheless, MRS and MRI can be performed on human biopsies at high spatial resolution, enough to allow a direct correlation between the chemical information and the histological features observed in such biopsies. Although HR-MAS is nowadays a well-established technique for spectroscopic analysis of tumor biopsies, with this approach just a mean metabolic profile of the whole sample can be obtained and thus the high histological heterogeneity of some important tumors is mostly neglected. The value of metabolic HR-MAS data strongly depends on a wide statistical analysis and usually the microanatomical rationale for the correlation between histology and spectroscopy is lost. We present here a different approach for the combined use of MRI and MRS on fresh human brain tumor biopsies with native contrast. This approach has been designed to achieve high spatial (18 × 18 × 50 μm) and spectral (0.031 μL) resolution in order to obtain as much spatially detailed morphological and metabolical information as possible without any previous treatment that can alter the sample. The preservation of native tissue conditions can provide information that can be translated to in vivo studies and additionally opens the possibility of performing other techniques to obtain complementary information from the same sample.

1H HR-MAS NMR Based Metabolic Profiling of Cells in Response to Treatment with a Hexacationic Ruthenium Metallaprism as Potential Anticancer Drug

(1)H high resolution magic angle spinning (HR-MAS) NMR spectroscopy was applied in combination with multivariate statistical analyses to study the metabolic response of whole cells to the treatment with a hexacationic ruthenium metallaprism [1](6+) as potential anticancer drug. Human ovarian cancer cells (A2780), the corresponding cisplatin resistant cells (A2780cisR), and human embryonic kidney cells (HEK-293) were each incubated for 24 h and 72 h with [1](6+) and compared to untreated cells. Different responses were obtained depending on the cell type and incubation time. Most pronounced changes were found for lipids, choline containing compounds, glutamate and glutathione, nucleotide sugars, lactate, and some amino acids. Possible contributions of these metabolites to physiologic processes are discussed. The time-dependent metabolic response patterns suggest that A2780 cells on one hand and HEK-293 cells and A2780cisR cells on the other hand may follow different cell death pathways and exist in different temporal stages thereof.

In vivo and ex vivo magnetic resonance spectroscopy of the infarct and the subventricular zone in experimental stroke

Ex vivo high-resolution magic-angle spinning (HRMAS) provides metabolic information with higher sensitivity and spectral resolution than in vivo magnetic resonance spectroscopy (MRS). Therefore, we used both techniques to better characterize the metabolic pattern of the infarct and the neural progenitor cells (NPCs) in the ipsilateral subventricular zone (SVZi). Ischemic stroke rats were divided into three groups: G0 (non-stroke controls, n = 6), G1 (day 1 after stroke, n = 6), and G7 (days 6 to 8 after stroke, n = 12). All the rats underwent MRS. Three rats per group were analyzed by HRMAS. The remaining rats were used for immunohistochemical studies. In the infarct, both techniques detected significant metabolic changes. The most relevant change was in mobile lipids (2.80 ppm) in the G7 group (a 5.53- and a 3.95-fold increase by MRS and HRMAS, respectively). In the SVZi, MRS did not detect any significant metabolic change. However, HRMAS detected a 2.70-fold increase in lactate and a 0.68-fold decrease in N-acetylaspartate in the G1 group. None of the metabolites correlated with the 1.37-fold increase in NPCs detected by immunohistochemistry in the G7 group. In conclusion, HRMAS improves the metabolic characterization of the brain in experimental ischemic stroke. However, none of the metabolites qualifies as a surrogate biomarker of NPCs.

Lipid metabolism emerges as a promising target for malignant glioma therapy

Malignant gliomas are one of the most treatment-refractory cancers. Development of resistance to chemo- and radio-therapies contributes to these tumors' aggressive phenotypes. Elevated lipid levels in gliomas have been reported for the last 50 years. However, the molecular mechanisms of how tumor tissues obtain lipids and utilize them are not well understood. Recently, the oncogenic signaling EGFR/PI3K/Akt pathway has been shown to enhance lipid synthesis and uptake by upregulating SREBP-1, a master transcriptional factor, to control lipid metabolism. This article discusses the analytical chemistry results of lipid components in glioma tissues from different research groups. The molecular mechanisms that link oncogenes with lipid programming, and identification of the key molecular targets and development of effective drugs to inhibit lipid metabolism in malignant gliomas will be discussed.

Magnetic resonance spectroscopy for detection of choline kinase inhibition in the treatment of brain tumors

Abnormal choline metabolism is a hallmark of cancer and is associated with oncogenesis and tumor progression. Increased choline is consistently observed in both preclinical tumor models and in human brain tumors by proton magnetic resonance spectroscopy (MRS). Thus, inhibition of choline metabolism using specific choline kinase inhibitors such as MN58b may be a promising new strategy for treatment of brain tumors. We demonstrate the efficacy of MN58b in suppressing phosphocholine production in three brain tumor cell lines. In vivo MRS studies of rats with intracranial F98-derived brain tumors showed a significant decrease in tumor total choline concentration after treatment with MN58b. High-resolution MRS of tissue extracts confirmed that this decrease was due to a significant reduction in phosphocholine. Concomitantly, a significant increase in poly-unsaturated lipid resonances was also observed in treated tumors, indicating apoptotic cell death. MRI-based volume measurements demonstrated a significant growth arrest in the MN58b-treated tumors in comparison with saline-treated controls. Histologically, MN58b-treated tumors showed decreased cell density, as well as increased apoptotic cells. These results suggest that inhibition of choline kinase can be used as an adjuvant to chemotherapy in the treatment of brain tumors and that decreases in total choline observed by MRS can be used as an effective pharmacodynamic biomarker of treatment response.

Magnetic resonance imaging characteristics of hepatocyte apoptosis (induced by right portal vein ligation) and necrosis (induced by combined right portal vein and right hepatic artery ligation) in rats

Objective

Using magnetic resonance imaging (MRI), this study aimed to demonstrate the appearance of hepatocytes following ligation of the right portal vein or combined ligation of the right portal vein and right hepatic artery, in a rat model.

Methods

Ninety adult Sprague–Dawley rats (body weight 250–300 g) were divided into three groups ( n = 30 per group): ligation of the right portal vein (Group A); combined ligation of the right portal vein and right hepatic artery (Group B); no intervention to obstruct blood supply (control group). Rats were then randomly subdivided into five groups that underwent examination at 3 h and 1, 3, 7 and 14 days postprocedure ( n = 6 per group). Livers were examined by routine MRI, diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS). After examination, each group of rats was sacrificed. Right hepatic lobes were removed and examined by pathology in six rats per timepoint; transmission electron microscopy (TEM) was undertaken in up to three rats per timepoint.

Results

Hepatocyte apoptosis and necrosis, by right portal vein ligation and combined right portal vein and right hepatic artery ligation respectively, were confirmed by pathology and TEM. In Group A, there were slight increases in intensity of T1- and T2-weighted images and in the apparent diffusion coefficient (ADC). In addition there were larger areas under the lactic acid and lipid peaks on MRS. In Group B, there were increased T1 and T2 signals, a decrease in the ADC and an increase of the area under the lactic acid peaks on MRS.

Conclusions

Hepatocyte apoptosis and necrosis induced by ligation procedures exhibited specific changes that were evident on MRI, DWI and MRS, and could be detected in vivo by MRI, in a rat model.

Molecular imaging coupled to pattern recognition distinguishes response to temozolomide in preclinical glioblastoma

Non-invasive monitoring of response to treatment of glioblastoma (GB) is nowadays carried out using MRI. MRS and MR spectroscopic imaging (MRSI) constitute promising tools for this undertaking. A temozolomide (TMZ) protocol was optimized for GL261 GB. Sixty-three mice were studied by MRI/MRS/MRSI. The spectroscopic information was used for the classification of control brain and untreated and responding GB, and validated against post-mortem immunostainings in selected animals. A classification system was developed, based on the MRSI-sampled metabolome of normal brain parenchyma, untreated and responding GB, with a 93% accuracy. Classification of an independent test set yielded a balanced error rate of 6% or less. Classifications correlated well both with tumor volume changes detected by MRI after two TMZ cycles and with the histopathological data: a significant decrease (p < 0.05) in the proliferation and mitotic rates and a 4.6-fold increase in the apoptotic rate. A surrogate response biomarker based on the linear combination of 12 spectral features has been found in the MRS/MRSI pattern of treated tumors, allowing the non-invasive classification of growing and responding GL261 GB. The methodology described can be applied to preclinical treatment efficacy studies to test new antitumoral drugs, and begets translational potential for early response detection in clinical studies.

Slow-MAS NMR: A new technology for in vivo metabolomic studies

Obtaining detailed in vivo metabolic information has been identified as key elements of better understanding the efficacy and toxicity of new therapies. A new nuclear magnetic resonance (NMR) technology called LOCMAT is reported in this paper that yields substantially increased spectral resolution in spatially localized in vivo H NMR metabolite spectra, as illustrated by measurements in the liver of a live mouse. LOCMAT promises to significantly enhance the utility of NMR spectroscopy for biomedical research.:

Current opportunities and challenges of magnetic resonance spectroscopy, positron emission tomography, and mass spectrometry imaging for mapping cancer metabolism in vivo

Cancer is known to have unique metabolic features such as Warburg effect. Current cancer therapy has moved forward from cytotoxic treatment to personalized, targeted therapies, with some that could lead to specific metabolic changes, potentially monitored by imaging methods. In this paper we addressed the important aspects to study cancer metabolism by using image techniques, focusing on opportunities and challenges of magnetic resonance spectroscopy (MRS), dynamic nuclear polarization (DNP)-MRS, positron emission tomography (PET), and mass spectrometry imaging (MSI) for mapping cancer metabolism. Finally, we highlighted the future possibilities of an integrated in vivo PET/MR imaging systems, together with an in situ MSI tissue analytical platform, may become the ultimate technologies for unraveling and understanding the molecular complexities in some aspects of cancer metabolism. Such comprehensive imaging investigations might provide information on pharmacometabolomics, biomarker discovery, and disease diagnosis, prognosis, and treatment response monitoring for clinical medicine.

Definition and quantification of acute inflammatory white matter injury in the immature brain by MRI/MRS at high magnetic field

BACKGROUND

Lipopolysaccharide (LPS) injection in the corpus callosum (CC) of rat pups results in diffuse white matter injury similar to the main neuropathology of preterm infants. The aim of this study was to characterize the structural and metabolic markers of acute inflammatory injury by high-field magnetic resonance imaging (MRI) magnetic resonance spectroscopy (MRS) in vivo.

METHODS

Twenty-four hours after a 1-mg/kg injection of LPS in postnatal day 3 rat pups, diffusion tensor imaging and proton nuclear magnetic spectroscopy ((1)H NMR) were analyzed in conjunction to determine markers of cell death and inflammation using immunohistochemistry and gene expression.

RESULTS

MRI and MRS in the CC revealed an increase in lactate and free lipids and a decrease of the apparent diffusion coefficient. Detailed evaluation of the CC showed a marked apoptotic response assessed by fractin expression. Interestingly, the degree of reduction in the apparent diffusion coefficient correlated strongly with the natural logarithm of fractin expression, in the same region of interest. LPS injection further resulted in increased activated microglia clustered in the cingulum, widespread astrogliosis, and increased expression of genes for interleukin (IL)-1, IL-6, and tumor necrosis factor.

CONCLUSION

This model was able to reproduce the typical MRI hallmarks of acute diffuse white matter injury seen in preterm infants and allowed the evaluation of in vivo biomarkers of acute neuropathology after inflammatory challenge.

Tumour T1 changes in vivo are highly predictive of response to chemotherapy and reflect the number of viable tumour cells--a preclinical MR study in mice

Background

Effective chemotherapy rapidly reduces the spin–lattice relaxation of water protons (T₁) in solid tumours and this change (ΔT₁) often precedes and strongly correlates with the eventual change in tumour volume (TVol). To understand the biological nature of ΔT₁, we have performed studies in vivo and ex vivo with the allosteric mTOR inhibitor, everolimus.

Methods

Mice bearing RIF-1 tumours were studied by magnetic resonance imaging (MRI) to determine TVol and T₁, and MR spectroscopy (MRS) to determine levels of the proliferation marker choline and levels of lipid apoptosis markers, prior to and 5 days (endpoint) after daily treatment with vehicle or everolimus (10 mg/kg). At the endpoint, tumours were ablated and an entire section analysed for cellular and necrotic quantification and staining for the proliferation antigen Ki67 and cleaved-caspase-3 as a measure of apoptosis. The number of blood-vessels (BV) was evaluated by CD31 staining. Mice bearing B16/BL6 melanoma tumours were studied by MRI to determine T₁ under similar everolimus treatment. At the endpoint, cell bioluminescence of the tumours was measured ex vivo.

Results

Everolimus blocked RIF-1 tumour growth and significantly reduced tumour T₁ and total choline (Cho) levels, and increased polyunsaturated fatty-acids which are markers of apoptosis. Immunohistochemistry showed that everolimus reduced the %Ki67⁺ cells but did not affect caspase-3 apoptosis, necrosis, BV-number or cell density. The change in T₁ (ΔT₁) correlated strongly with the changes in TVol and Cho and %Ki67⁺. In B16/BL6 tumours, everolimus also decreased T₁ and this correlated with cell bioluminescence; another marker of cell viability. Receiver-operating-characteristic curves (ROC) for everolimus on RIF-1 tumours showed that ΔT₁ had very high levels of sensitivity and specificity (ROC_AUC = 0.84) and this was confirmed for the cytotoxic patupilone in the same tumour model (ROC_AUC = 0.97).

Conclusion

These studies suggest that ΔT₁ is not a measure of cell density but reflects the decreased number of remaining viable and proliferating tumour cells due to perhaps cell and tissue destruction releasing proteins and/or metals that cause T₁ relaxation. ΔT₁ is a highly sensitive and specific predictor of response. This MRI method provides the opportunity to stratify a patient population during tumour therapy in the clinic.

Initial studies on mechanism of action and cell death of active N-oxide-containing heterocycles in Trypanosoma cruzi epimastigotes in vitro

Chagas disease, endemic in 21 countries across Latin America, kills more people in the region each year than any other parasite-borne disease. Therapeutic options have problems ranging from toxicity, poor efficacy, drug resistance and high cost. Thus, cheaper and less toxic treatments are necessary. From our in-house chemical library of agents against Trypanosoma cruzi the most relevant N-oxide-containing heterocycles were selected for mode of action and type of death studies. Also included in these studies were two active nitrofuranes. Epimastigotes of T. cruzi were used as the biological model in this study. The metabolic profile was studied by 1H NMR in association with the MTT assay. Excreted catabolites data, using 1H NMR spectroscopy, showed that most of the studied N-oxides were capable of decreasing both the release of succinate and acetate shedding, the compounds therefore possibly acting on mitochondria. Only quinoxalines and the nitrofurane Nf1 showed significant mitochondrial dehydrogenase inhibitions, but with different dose-time profiles. In the particular case of quinoxaline Qx2 the glucose uptake study revealed that the integrity of some pathways into the glycosome could be affected. Optic, fluorescence (TUNEL and propidium iodide) and transmission electron microscopy (TEM) were employed for type of death studies. These studies were complemented with 1H NMR to visualize mobile lipids. At low concentrations none of the selected compounds showed a positive TUNEL assay. However, both quinoxalines, one furoxan and one benzofuroxan showed a necrotic effect at high concentrations. Curiously, one furoxan, Fx1, one benzofuroxan, Bfx1, and one nitrofurane, Nf1, caused a particular phenotype, with a big cytoplasmatic vacuole being observed while the parasite was still alive. Studies of TEM and employing a protease inhibitor (3-methyladenine) suggested an autophagic phenotype for Bfx1 and Nf1 and a 'BigEye' phenotype for Fx1.

Whole brain mapping of water pools and molecular dynamics with rotating frame MR relaxation using gradient modulated low-power adiabatic pulses

Nuclear magnetic resonance (NMR) relaxation in the rotating frame is sensitive to molecular dynamics on the time scale of water molecules interacting with macromolecules or supramolecular complexes, such as proteins, myelin and cell membranes. Hence, longitudinal (T1ρ) and transverse (T2ρ) relaxation in the rotating frame may have a great potential to probe the macromolecular fraction of tissues. This stimulated a large interest in using this MR contrast to image brain under healthy and disease conditions. However, experimental challenges related to the use of intense radiofrequency irradiation have limited the widespread use of T1ρ and T2ρ imaging. Here, we present methodological development to acquire 3D high-resolution or 2D (multi-)slice selective T1ρ and T2ρ maps of the entire human brain within short acquisition times. These improvements are based on a class of gradient modulated adiabatic pulses that reduce the power deposition, provide slice selection, and mitigate artifacts resulting from inhomogeneities of B1 and B0 magnetic fields. Based on an analytical model of the T1ρ and T2ρ relaxation we compute the maps of macromolecular bound water fraction, correlation and exchange time constants as quantitative biomarkers informative of tissue macromolecular content. Results obtained from simulations, phantoms and five healthy subjects are included.

Monitoring response to cytostatic cisplatin in a HER2(+) ovary cancer model by MRI and in vitro and in vivo MR spectroscopy

Background:

Limited knowledge is available on alterations induced by cytostatic drugs on magnetic resonance spectroscopy (MRS) and imaging (MRI) parameters of human cancers, in absence of apoptosis or cytotoxicity. We here investigated the effects of a cytostatic cisplatin (CDDP) treatment on ¹H MRS and MRI of HER2-overexpressing epithelial ovarian cancer (EOC) cells and in vivo xenografts.

Methods:

High-resolution MRS analyses were performed on in vivo passaged SKOV3.ip cells and cell/tissue extracts (16.4 or 9.4 T). In vivo MRI/MRS quantitative analyses (4.7 T) were conducted on xenografts obtained by subcutaneous implantation of SKOV3.ip cells in SCID mice. The apparent diffusion coefficient (ADC) and metabolite levels were measured.

Results:

CDDP-induced cytostatic effects were associated with a metabolic shift of cancer cells towards accumulation of MRS-detected neutral lipids, whereas the total choline profile failed to be perturbed in both cultured cells and xenografts. In vivo MRI examinations showed delayed tumour growth in the CDDP-treated group, associated with early reduction of the ADC mean value.

Conclusion:

This study provides an integrated set of information on cancer metabolism and physiology for monitoring the response of an EOC model to a cytostatic chemotherapy, as a basis for improving the interpretation of non-invasive MR examinations of EOC patients.

Cell survival during complete nutrient deprivation depends on lipid droplet-fueled β-oxidation of fatty acids

Cells exposed to stress of different origins synthesize triacylglycerols and generate lipid droplets (LD), but the physiological relevance of this response is uncertain. Using complete nutrient deprivation of cells in culture as a simple model of stress, we have addressed whether LD biogenesis has a protective role in cells committed to die. Complete nutrient deprivation induced the biogenesis of LD in human LN18 glioblastoma and HeLa cells and also in CHO and rat primary astrocytes. In all cell types, death was associated with LD depletion and was accelerated by blocking LD biogenesis after pharmacological inhibition of Group IVA phospholipase A2 (cPLA2α) or down-regulation of ceramide kinase. Nutrient deprivation also induced β-oxidation of fatty acids that was sensitive to cPLA2α inhibition, and cell survival in these conditions became strictly dependent on fatty acid catabolism. These results show that, during nutrient deprivation, cell viability is sustained by β-oxidation of fatty acids that requires biogenesis and mobilization of LD.

Quantitative (31)P HR-MAS MR spectroscopy for detection of response to PI3K/mTOR inhibition in breast cancer xenografts

PURPOSE

Phospholipid metabolites are of importance in cancer studies, and have been suggested as candidate metabolic biomarkers for response to targeted anticancer drugs. The purpose of this study was to develop a phosphorus ((31) P) high resolution magic angle spinning magnetic resonance spectroscopy protocol for quantification of phosphorylated metabolites in intact cancer tissue.

METHODS

(31) P spectra were acquired on a 14.1 T spectrometer with a triplet (1) H/(13) C/(31) P MAS probe. Quantification of metabolites was performed using the PULCON principle. Basal-like and luminal-like breast cancer xenografts were treated with the dual PI3K/mTOR inhibitor BEZ235, and the impact of treatment on the concentration of phosphocholine, glycerophosphocholine, phosphoethanolamine and glycerophosphoethanolamine was evaluated.

RESULTS

In basal-like xenografts, BEZ235 treatment induced a significant decrease in phosphoethanolamine (-25.6%, P = 0.01) whilst phosphocholine (16.5%, P = 0.02) and glycerophosphocholine (37.3%, P < 0.001) were significantly increased. The metabolic changes could partially be explained by increased levels of phospholipase A2 group 4A (PLA2G4A).

CONCLUSION

(31) P high resolution magic angle spinning magnetic resonance spectroscopy is a useful method for quantitative assessment of metabolic responses to PI3K inhibition. Using the PULCON principle for quantification, the levels of phosphocholine, glycerophosphocholine, phosphoethanolamine, and glycerophosphoethanolamine could be evaluated with high precision and accuracy.