THEM6-mediated reprogramming of lipid metabolism supports treatment resistance in prostate cancer

Despite the clinical benefit of androgen-deprivation therapy (ADT), the majority of patients with advanced prostate cancer (PCa) ultimately develop lethal castration-resistant prostate cancer (CRPC). In this study, we identified thioesterase superfamily member 6 (THEM6) as a marker of ADT resistance in PCa. THEM6 deletion reduces in vivo tumour growth and restores castration sensitivity in orthograft models of CRPC. Mechanistically, we show that the ER membrane-associated protein THEM6 regulates intracellular levels of ether lipids and is essential to trigger the induction of the ER stress response (UPR). Consequently, THEM6 loss in CRPC cells significantly alters ER function, reducing de novo sterol biosynthesis and preventing lipid-mediated activation of ATF4. Finally, we demonstrate that high THEM6 expression is associated with poor survival and correlates with high levels of UPR activation in PCa patients. Altogether, our results highlight THEM6 as a novel driver of therapy resistance in PCa as well as a promising target for the treatment of CRPC.

Noninvasive Detection of Ischemic Vascular Damage in a Pig Model of Liver Donation After Circulatory Death

BACKGROUND AND AIMS

Liver graft quality is evaluated by visual inspection prior to transplantation, a process highly dependent on the surgeon's experience. We present an objective, noninvasive, quantitative way of assessing liver quality in real time using Raman spectroscopy, a laser-based tool for analyzing biomolecular composition.

APPROACH AND RESULTS

A porcine model of donation after circulatory death (DCD) with normothermic regional perfusion (NRP) allowed assessment of liver quality premortem, during warm ischemia (WI) and post-NRP. Ten percent of circulating blood volume was removed in half of experiments to simulate blood recovery for DCD heart removal. Left median lobe biopsies were obtained before circulatory arrest, after 45 minutes of WI, and after 2 hours of NRP and analyzed using spontaneous Raman spectroscopy, stimulated Raman spectroscopy (SRS), and staining. Measurements were also taken in situ from the porcine liver using a handheld Raman spectrometer at these time points from left median and right lateral lobes. Raman microspectroscopy detected congestion during WI by measurement of the intrinsic Raman signal of hemoglobin in red blood cells (RBCs), eliminating the need for exogenous labels. Critically, this microvascular damage was not observed during WI when 10% of circulating blood was removed before cardiac arrest. Two hours of NRP effectively cleared RBCs from congested livers. Intact RBCs were visualized rapidly at high resolution using SRS. Optical properties of ischemic livers were significantly different from preischemic and post-NRP livers as measured using a handheld Raman spectrometer.

CONCLUSIONS

Raman spectroscopy is an effective tool for detecting microvascular damage which could assist the decision to use marginal livers for transplantation. Reducing the volume of circulating blood before circulatory arrest in DCD may help reduce microvascular damage.

A new class of ratiometric small molecule intracellular pH sensors for Raman microscopy

Intracellular pH (pH_i) homeostasis is intertwined with a myriad of normal cellular behaviors as well as pathological processes. As such, small molecule probes for the measurement of pH_i are invaluable tools for chemical biology, facilitating the study of the role of pH in cellular function and disease. The field of small molecule pH_i sensors has traditionally been dominated with probes based on fluorescent scaffolds. In this study, a series of low molecular weight (<260) oligoyne compounds have been developed which exhibit pH sensitive alkyne stretching frequencies (ν_alkyne) in Raman spectroscopy. The modular design of the compounds enabled tuneability of their pK_a(H) through simple structural modification, such that continuous pH sensitivity is achieved over the range 2-10. Alkyne stretching bands reside in the 'cell-silent' region of the Raman spectrum (1800-2600 cm^-1) and are readily detectable in a cellular environment with subcellular spatial resolution. This enabled the application of a pH sensitive oligoyne compound to the ratiometric sensing of pH_i in prostate cancer (PC3) cells in response to drug treatment. We propose that probes based on Alkyne Tag Raman Imaging offer an entirely new platform for the sensing of pH_i, complementary to fluorescence microscopy.

2,4-dienoyl-CoA reductase regulates lipid homeostasis in treatment-resistant prostate cancer

Despite the clinical success of Androgen Receptor (AR)-targeted therapies, reactivation of AR signalling remains the main driver of castration-resistant prostate cancer (CRPC) progression. In this study, we perform a comprehensive unbiased characterisation of LNCaP cells chronically exposed to multiple AR inhibitors (ARI). Combined proteomics and metabolomics analyses implicate an acquired metabolic phenotype common in ARI-resistant cells and associated with perturbed glucose and lipid metabolism. To exploit this phenotype, we delineate a subset of proteins consistently associated with ARI resistance and highlight mitochondrial 2,4-dienoyl-CoA reductase (DECR1), an auxiliary enzyme of beta-oxidation, as a clinically relevant biomarker for CRPC. Mechanistically, DECR1 participates in redox homeostasis by controlling the balance between saturated and unsaturated phospholipids. DECR1 knockout induces ER stress and sensitises CRPC cells to ferroptosis. In vivo, DECR1 deletion impairs lipid metabolism and reduces CRPC tumour growth, emphasizing the importance of DECR1 in the development of treatment resistance.

Decay of Thermal Tolerance in Queensland Fruit Fly Eggs (Bactrocera tryoni, Diptera: Tephritidae) Following Non-Lethal Heat Hardening

Quarantine disinfestation treatments for Queensland fruit fly (Bactrocera tryoni (Froggatt)) have been developed which use high temperatures to kill preimaginal life stages within fruit prior to export. However, thermal tolerance of individuals can be increased if they are exposed to elevated temperatures before disinfestation treatment. The rate that this thermal conditioning decays after exposure, and the effect of temperature on this decay process, were investigated. Eggs of B. tryoni were exposed to a nonlethal hot water treatment at 38°C for 15 min, 1 or 3 h, then held in air at 25°C for times ranging from 15 min to 12 h, before being exposed to hot water disinfestation at 46°C for various times. From each of these cohorts, the lethal time for 99% mortality (LT99) was calculated. The LT99 of B. tryoni eggs increased with longer conditioning times at 38°C. For each conditioning time, the LT99 decreased with longer delay periods at 25°C prior to disinfestation. The rate of decrease was greatest during the first hour of delay, after which the rate of decrease slowed and tended toward zero. This induction and decay was modeled using a double-exponential equation. These experiments show that thermal conditions prior to disinfestation, and the time delay before the procedure commences, both influence the response of the insect to the disinfestation treatment. These results have implications for the specification of postharvest quarantine treatments, which are usually expressed only in terms of a fruit-center target temperature.

NMR chemical shifts of urea loaded copper benzoate. A joint solid-state NMR and DFT study

We report solid-state ¹³C NMR spectra of urea-loaded copper benzoate, Cu₂(C₆H₅CO₂)₄·2(urea), a simplified model for copper paddlewheel-based metal-organic frameworks (MOFs), along with first-principles density functional theory (DFT) computation of the paramagnetic NMR (pNMR) chemical shifts. Assuming a Boltzmann distribution between a diamagnetic open-shell singlet ground state (in a broken-symmetry Kohn-Sham DFT description) and an excited triplet state, the observed δ(¹³C) values are reproduced reasonably well at the PBE0-⅓/IGLO-II//PBE0-D3/AE1 level. Using the proposed assignments of the signals, the mean absolute deviation between computed and observed ¹³C chemical shifts is below 30 ppm over a range of more than 1100 ppm.

Raman spectroscopy investigation of biochemical changes in tumor spheroids with aging and after treatment with staurosporine

There has been increasing use of in vitro cell culture models that more realistically replicate the three-dimensional (3D) environment found in vivo. Multicellular tumor spheroids (MTS) using cell lines or patient-derived organoids have become an important in vitro drug development tool, where cells are grown in a 3D "sphere" that exhibits many of the characteristics found in vivo. Significantly, MTS develop gradients in nutrients and oxygen, commonly found in tumors that contribute to therapy resistance. While MTS show promise as a more realistic in vitro culture model, there is a massive need to improve imaging technologies for assessing biochemical characteristics and drug response in such models to maximize their translation into useful applications such as high throughput screening (HTS). In this study, we investigate the potential for Raman spectroscopy to unveil biochemical information in MTS and have investigated how spheroid age influences drug response, shedding light on increased therapy resistance in developing tumors. The wealth of molecular level information delivered by Raman spectroscopy in a noninvasive manner, could aid translation of these 3D models into HTS applications.

Ratiometric analysis using Raman spectroscopy as a powerful predictor of structural properties of fatty acids

Raman spectroscopy has been used extensively for the analysis of biological samples in vitro, ex vivo and in vivo. While important progress has been made towards using this analytical technique in clinical applications, there is a limit to how much chemically specific information can be extracted from a spectrum of a biological sample, which consists of multiple overlapping peaks from a large number of species in any particular sample. In an attempt to elucidate more specific information regarding individual biochemical species, as opposed to very broad assignments by species class, we propose a bottom-up approach beginning with a detailed analysis of pure biochemical components. Here, we demonstrate a simple ratiometric approach applied to fatty acids, a subsection of the lipid class, to allow the key structural features, in particular degree of saturation and chain length, to be predicted. This is proposed as a starting point for allowing more chemically and species-specific information to be elucidated from the highly multiplexed spectrum of multiple overlapping signals found in a real biological sample. The power of simple ratiometric analysis is also demonstrated by comparing the prediction of degree of unsaturation in food oil samples using ratiometric and multivariate analysis techniques which could be used for food oil authentication.

Multiplex imaging of live breast cancer tumour models through tissue using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Through utilizing the depth penetration capabilities of SESORS, multiplexed imaging and classification of three singleplex nanotags and a triplex of nanotags within breast cancer tumour models is reported for the first time through depths of 10 mm using a handheld SORS instrument.

Ratiometric Raman imaging reveals the new anti-cancer potential of lipid targeting drugs

De novo lipid synthesis is upregulated in cancer cells and inhibiting these pathways has displayed anti-tumour activity. Here we use Raman spectroscopy, focusing solely on high wavenumber spectra, to detect changes in lipid composition in single cells in response to drugs targeting de novo lipid synthesis. Unexpectedly, the beta-blocker propranolol showed selectively towards cancerous PC3 compared to non-cancerous PNT2 prostate cells, demonstrating the potential of this approach to identify new anti-cancer drug leads. A unique and simple ratiometric approach for intracellular lipid investigation is reported using statistical analysis to create phenotypic 'barcodes', a globally applicable strategy for Raman drug-cell studies. High wavenumber spectral analysis is compatible with low cost glass substrates, easily translatable into the cytological work stream. The analytical strength of this technique could have a significant impact on cancer treatment through vastly improved understanding of cancer cell metabolism, and thus guide drug design and enhance personalised medicine strategies.

Tracking intracellular uptake and localisation of alkyne tagged fatty acids using Raman spectroscopy

Intracellular uptake, distribution and metabolism of lipids are tightly regulated characteristics in healthy cells. An analytical technique capable of understanding these characteristics with a high level of species specificity in a minimally invasive manner is highly desirable in order to understand better how these become disrupted during disease. In this study, the uptake and distribution of three different alkyne tagged fatty acids in single cells were monitored and compared, highlighting the ability of Raman spectroscopy combined with alkyne tags for better understanding of the fine details with regard to uptake, distribution and metabolism of very chemically specific lipid species. This indicates the promise of using Raman spectroscopy directly with alkyne tagged lipids for cellular studies as opposed to subsequently clicking of a fluorophore onto the alkyne for fluorescence imaging.

SERS as a tool for in vitro toxicology

Measuring markers of stress such as pH and redox potential are important when studying toxicology in in vitro models because they are markers of oxidative stress, apoptosis and viability. While surface enhanced Raman spectroscopy is ideally suited to the measurement of redox potential and pH in live cells, the time-intensive nature and perceived difficulty in signal analysis and interpretation can be a barrier to its broad uptake by the biological community. In this paper we detail the development of signal processing and analysis algorithms that allow SERS spectra to be automatically processed so that the output of the processing is a pH or redox potential value. By automating signal processing we were able to carry out a comparative evaluation of the toxicology of silver and zinc oxide nanoparticles and correlate our findings with qPCR analysis. The combination of these two analytical techniques sheds light on the differences in toxicology between these two materials from the perspective of oxidative stress.

Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS)

Detection of a live 3D tumour model through 15 mm of tissue using SESORRS.

In order to improve patient survival and reduce the amount of unnecessary and traumatic biopsies, non-invasive detection of cancerous tumours is of imperative and urgent need. Multicellular tumour spheroids (MTS) can be used as an ex vivo cancer tumour model, to model in vivo nanoparticle (NP) uptake by the enhanced permeability and retention (EPR) effect. Surface enhanced spatially offset Raman spectroscopy (SESORS) combines both surface enhanced Raman spectroscopy (SERS) and spatially offset Raman spectroscopy (SORS) to yield enhanced Raman signals at much greater sub-surface levels. By utilizing a reporter that has an electronic transition in resonance with the laser frequency, surface enhanced resonance Raman scattering (SERRS) yields even greater enhancement in Raman signal. Using a handheld SORS spectrometer with back scattering optics, we demonstrate the detection of live breast cancer 3D MTS containing SERRS active NPs through 15 mm of porcine tissue. False color 2D heat intensity maps were used to determine tumour model location. In addition, we demonstrate the tracking of SERRS-active NPs through porcine tissue to depths of up to 25 mm. This unprecedented performance is due to the use of red-shifted chalcogenpyrylium-based Raman reporters to demonstrate the novel technique of surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) for the first time. Our results demonstrate a significant step forward in the ability to detect vibrational fingerprints from a tumour model at depth through tissue. Such an approach offers significant promise for the translation of NPs into clinical applications for non-invasive disease diagnostics based on this new chemical principle of measurement.

Surface enhanced resonance Raman spectroscopy (SERRS) for probing through plastic and tissue barriers using a handheld spectrometer

Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced resonance Raman spectroscopy (SERRS).

Towards establishing a minimal nanoparticle concentration for applications involving surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) in vivo

Detection of SERRS nanotags at picomolar concentrations through 5 mm of tissue using SESORS.

Bioanalytical Measurements Enabled by Surface-Enhanced Raman Scattering (SERS) Probes

Since its discovery in 1974, surface-enhanced Raman scattering (SERS) has gained momentum as an important tool in analytical chemistry. SERS is used widely for analysis of biological samples, ranging from in vitro cell culture models, to ex vivo tissue and blood samples, and direct in vivo application. New insights have been gained into biochemistry, with an emphasis on biomolecule detection, from small molecules such as glucose and amino acids to larger biomolecules such as DNA, proteins, and lipids. These measurements have increased our understanding of biological systems, and significantly, they have improved diagnostic capabilities. SERS probes display unique advantages in their detection sensitivity and multiplexing capability. We highlight key considerations that are required when performing bioanalytical SERS measurements, including sample preparation, probe selection, instrumental configuration, and data analysis. Some of the key bioanalytical measurements enabled by SERS probes with application to in vitro, ex vivo, and in vivo biological environments are discussed.

Targeted SERS nanosensors measure physicochemical gradients and free energy changes in live 3D tumor spheroids

Use of multicellular tumor spheroids (MTS) to investigate therapies has gained impetus because they have potential to mimic factors including zonation, hypoxia and drug-resistance. However, analysis remains difficult and often destroys 3D integrity. Here we report an optical technique using targeted nanosensors that allows in situ 3D mapping of redox potential gradients whilst retaining MTS morphology and function. The magnitude of the redox potential gradient can be quantified as a free energy difference (ΔG) and used as a measurement of MTS viability. We found that by delivering different doses of radiotherapy to MTS we could correlate loss of ΔG with increasing therapeutic dose. In addition, we found that resistance to drug therapy was indicated by an increase in ΔG. This robust and reproducible technique allows interrogation of an in vitro tumor-model's bioenergetic response to therapy, indicating its potential as a tool for therapy development.

SERS-based monitoring of the intracellular pH in endothelial cells: the influence of the extracellular environment and tumour necrosis factor-α

The intracellular pH plays an important role in various cellular processes. In this work, we describe a method for monitoring of the intracellular pH in endothelial cells by using surface enhanced Raman spectroscopy (SERS) and 4-mercaptobenzoic acid (MBA) anchored to gold nanoparticles as pH-sensitive probes. Using the Raman microimaging technique, we analysed changes in intracellular pH induced by buffers with acid or alkaline pH, as well as in endothelial inflammation induced by tumour necrosis factor-α (TNFα). The targeted nanosensor enabled spatial pH measurements revealing distinct changes of the intracellular pH in endosomal compartments of the endothelium. Altogether, SERS-based analysis of intracellular pH proves to be a promising technique for a better understanding of intracellular pH regulation in various subcellular compartments.

Simultaneous intracellular redox potential and pH measurements in live cells using SERS nanosensors

Intracellular redox potential is a highly regulated cellular characteristic and is critically involved in maintaining cellular health and function. The dysregulation of redox potential can result in the initiation and progression of numerous diseases. Redox potential is determined by the balance of oxidants and reductants in the cell and also by pH. For this reason a technique for quantitative measurement of intracellular redox potential and pH is highly desirable. In this paper we demonstrate how surface enhanced Raman scattering (SERS) nanosensors can be used for multiplexed measurement of both pH and redox potential in live single cells.

Chemical analysis of multicellular tumour spheroids

Conventional two dimensional (2D) monolayer cell culture has been considered the 'gold standard' technique for in vitro cellular experiments. However, the need for a model that better mimics the three dimensional (3D) architecture of tissue in vivo has led to the development of Multicellular Tumour Spheroids (MTS) as a 3D tissue culture model. To some extent MTS mimic the environment of in vivo tumours where, for example, oxygen and nutrient gradients develop, protein expression changes and cells form a spherical structure with regions of proliferation, senescence and necrosis. This review focuses on the development of techniques for chemical analysis of MTS as a tool for understanding in vivo tumours and a platform for more effective drug and therapy discovery. While traditional monolayer techniques can be translated to 3D models, these often fail to provide the desired spatial resolution and z-penetration for live cell imaging. More recently developed techniques for overcoming these problems will be discussed with particular reference to advances in instrument technology for achieving the increased spatial resolution and imaging depth required.

Communication disruption of guava moth (Coscinoptycha improbana) using a pheromone analog based on chain length

The guava moth, Coscinoptycha improbana, an Australian species that infests fruit crops in commercial and home orchards, was first detected in New Zealand in 1997. A four-component pheromone blend was identified but is not yet commercially available. Using single sensillum recordings from male antennae, we established that the same olfactory receptor neurons responded to two guava moth sex pheromone components, (Z)-11-octadecen-8-one and (Z)-12-nonadecen-9-one, and to a chain length analog, (Z)-13-eicosen-10-one, the sex pheromone of the related peach fruit moth, Carposina sasakii. We then field tested whether this non-specificity of the olfactory neurons might enable disruption of sexual communication by the commercially available analog, using male catch to synthetic lures in traps in single-tree, nine-tree and 2-ha plots. A disruptive pheromone analog, based on chain length, is reported for the first time. Trap catches for guava moth were disrupted by three polyethylene tubing dispensers releasing the analog in single-tree plots (86% disruption of control catches) and in a plots of nine trees (99% disruption). Where peach fruit moth pheromone dispensers were deployed at a density of 1000/ha in two 2-ha areas, pheromone traps for guava moth were completely disrupted for an extended period (up to 470 days in peri-urban gardens in Mangonui and 422 days in macadamia nut orchards in Kerikeri). In contrast, traps in untreated areas over 100 m away caught 302.8 ± 128.1 moths/trap in Mangonui and 327.5 ± 78.5 moths/ trap in Kerikeri. The longer chain length in the pheromone analog has greater longevity than the natural pheromone due to its lower volatility. Chain length analogs may warrant further investigation for mating disruption in Lepidoptera, and screening using single-sensillum recording is recommended.

Sex pheromone of the citrus flower moth Prays nephelomima: pheromone identification, field trapping trials, and phenology

Analysis of sex pheromone gland extract of the citrus flower moth, Prays nephelomima (Lepidoptera: Yponomeutidae) by coupled gas chromatography-electroantennogram detection, revealed one electrophysiologically active compound. Structural analysis using gas chromatography, gas chromatography-mass spectrometry, and dimethyldisulfide derivatization identified this as the monounsaturated aldehyde (Z)-7-tetradecenal. Field trials in commercial citrus orchards on the North Island of New Zealand showed that (Z)-7-tetradecenal was highly attractive to male P. nephelomima. Phenology data, collected over 19 months in three commercial orchards, from traps baited with the sex pheromone at a lure loading of 300 microg on a red rubber septum, indicated that male moths may be present throughout the year, with numbers peaking in late summer and autumn.

Pre- and postharvest effects of lufenuron on Epiphyas postvittana (Lepidoptera: Tortricidae)

First-, third-, and fifth-instar Epiphyas postvittana (Walker) were exposed to a range of lufenuron concentrations (0-200 ppm) incorporated into synthetic diet and their subsequent development and mortality responses were determined. For all instars the greatest change in mortality response occurred over lufenuron concentrations < or = 3 ppm. However, third and fifth instars displayed an increase in mortality earlier than first instars, and were more sensitive to the lower lufenuron concentrations in this range. Only first and third instars subjected to < or = 2.5 ppm lufenuron survived the 26-d exposure trial. No larvae first exposed to lufenuron as first or third instars survived to pupation if ingesting concentrations of > or = 1 and > or = 3 ppm, respectively. Consumption of lower lufenuron concentrations by these larvae delayed pupation and resulted in pupal deformity. In contrast, fifth instars subjected to 100 ppm were capable of surviving the 26-d trial period and displayed a slower progressive reduction in survival to pupation with increase in lufenuron concentration. Also in contrast to more immature stages, fifth instars exposed to lufenuron developed more rapidly to pupation than larvae not exposed to the insect growth regulator (IGR), and all resulting pupae were normal. Third instars were exposed to sublethal lufenuron concentrations (0-3 ppm) for 4 d and the fourth-instar survivors subjected to a controlled atmosphere cold storage treatment (2% O2, 2% CO2, 0.6 degree C). Larvae ingesting diet containing 0.5 ppm (and to a lesser extent 1 ppm) lufenuron required longer exposure to the postharvest treatment to achieve > or = 95% mortality than larvae not ingesting the IGR. However, the analogous mortality response of larvae exposed to 3 ppm lufenuron was comparable to the control.