Probing the Mechanism of Action of Bis(phenolato) Amine (ONO Donor Set) Titanium(IV) Anticancer Agents

The need for anticancer therapies that overcome metallodrug resistance while minimizing adverse toxicities is targeted, herein, using titanium coordination complexes. Octahedral titanium(IV) trans,mer-[Ti{R1N(CH2-2-MeO-4-R1-C6H2)2}2] [R1 = Et, allyl, n-Pr, CHO, F, CH2(morpholino), the latter from the formyl derivative; R2 = Me, Et; not all combinations] are attained from Mannich reactions of commercial 2-methoxyphenols (27-74% overall yield, 2 steps). These crystalline (four X-ray structures) Ti(IV)-complexes are active against MCF-7, HCT-116, HT-29, PANC-1, and MDA-MB-468 cancer cell lines (GI50 = 0.5-38 μM). Their activity and cancer selectivity (vs nontumor MRC-5 cells) typically exceeds that of cisplatin (up to 16-fold). Proteomic analysis (in MCF-7) supported by other studies (G2/M cell cycle arrest, ROS generation, γH2AX production, caspase activation, annexin positivity, western blot, and kinase screens in MCF-7 and HCT-116) suggest apoptosis elicited by more than one mechanism of action. Comparison of these data to the modes of action proposed for salan Ti(IV) complexes is made.

Differential expression of genes controlling lymphocyte differentiation and migration in two distinct endotypes of type 1 diabetes

AIMS

Morphological studies of pancreas samples obtained from young people with recent-onset type 1 diabetes have revealed distinct patterns of immune cell infiltration of the pancreatic islets suggestive of two age-associated type 1 diabetes endotypes that differ by inflammatory responses and rates of disease progression. The objective of this study was to investigate whether these proposed disease endotypes are associated with pathological differences in immune cell activation and cytokine secretion by applying multiplexed gene expression analysis to pancreatic tissue from recent-onset type 1 diabetes cases.

METHODS

RNA was extracted from samples of fixed, paraffin-embedded pancreas tissue from type 1 diabetes cases characterised by endotype and from controls without diabetes. Expression levels of 750 genes associated with autoimmune inflammation were determined by hybridisation to a panel of capture and reporter probes and these were counted as a measure of gene expression. Normalised counts were analysed for differences in expression between 29 type 1 diabetes cases and 7 controls without diabetes, and between the two type 1 diabetes endotypes.

RESULTS

Ten inflammation-associated genes, including INS, were significantly under-expressed in both endotypes and 48 genes were more highly expressed. A different set of 13 genes associated with the development, activation and migration of lymphocytes was uniquely overexpressed in the pancreas of people developing diabetes at younger age.

CONCLUSIONS

The results provide evidence that histologically defined type 1 diabetes endotypes differ in their immunopathology and identify inflammatory pathways specifically involved in disease developing at a young age, essential for a better understanding of disease heterogeneity.

PARP1 mediated PARylation contributes to myogenic progression and glucocorticoid transcriptional response

The ADP-ribosyltransferase, PARP1 enzymatically generates and applies the post-translational modification, ADP-Ribose (ADPR). PARP1 roles in genome maintenance are well described, but recent work highlights roles in many fundamental processes including cellular identity and energy homeostasis. Herein, we show in both mouse and human skeletal muscle cells that PARP1-mediated PARylation is a regulator of the myogenic program and the muscle transcriptional response to steroid hormones. Chemical PARP1 modulation impacts the expression of major myocellular proteins, including troponins, key in dictating muscle contractile force. Whilst PARP1 in absence of DNA damage is often assumed to be basally inactive, we show PARylation to be acutely sensitive to extracellular glucose concentrations and the steroid hormone class, glucocorticoids which exert considerable authority over muscle tissue mass. Specifically, we find during myogenesis, a transient and significant rise in PAR. This early-stage differentiation event, if blocked with PARP1 inhibition, reduced the abundance of important muscle proteins in the fully differentiated myotubes. This suggests that PAR targets during early-stage differentiation are central to the proper development of the muscle contractile unit. We also show that reduced PARP1 in myoblasts impacts a variety of metabolic pathways in line with the recorded actions of glucocorticoids. Currently, as both regulators of myogenesis and muscle mass loss, glucocorticoids represent a clinical conundrum. Our work goes on to identify that PARP1 influences transcriptional activation by glucocorticoids of a subset of genes critical to human skeletal muscle pathology. These genes may therefore signify a regulatory battery of targets through which selective glucocorticoid modulation could be achieved. Collectively, our data provide clear links between PARP1-mediated PARylation and skeletal muscle homeostatic mechanisms crucial to tissue mass maintenance and endocrine response.

Small extracellular vesicles released from germinated kiwi pollen (pollensomes) present characteristics similar to mammalian exosomes and carry a plant homolog of ALIX

INTRODUCTION

In the last decade, it has been discovered that allergen-bearing extracellular nanovesicles, termed "pollensomes", are released by pollen during germination. These extracellular vesicles (EVs) may play an important role in pollen-pistil interaction during fertilization, stabilizing the secreted bioactive molecules and allowing long-distance signaling. However, the molecular composition and the biological role of these EVs are still unclear. The present study had two main aims: (I) to clarify whether pollen germination is needed to release pollensomes, or if they can be secreted also in high humidity conditions; and (II) to investigate the molecular features of pollensomes following the most recent guidelines for EVs isolation and identification.

METHODS

To do so, pollensomes were isolated from hydrated and germinated kiwi (Actinidia chinensis Planch.) pollen, and characterized using imaging techniques, immunoblotting, and proteomics.

RESULTS

These analyses revealed that only germinated kiwi pollen released detectable concentrations of nanoparticles compatible with small EVs for shape and protein content. Moreover, a plant homolog of ALIX, which is a well-recognized and accepted marker of small EVs and exosomes in mammals, was found in pollensomes.

DISCUSSION

The presence of this protein, along with other proteins involved in endocytosis, is consistent with the hypothesis that pollensomes could comprehend a prominent subpopulation of plant exosome-like vesicles.

A Proteomic Approach Reveals That miR-423-5p Modulates Glucidic and Amino Acid Metabolism in Prostate Cancer Cells

Recently, we have demonstrated that miR-423-5p modulates the growth and metastases of prostate cancer (PCa) cells both in vitro and in vivo. Here, we have studied the effects of miR-423-5p on the proteomic profile in order to identify its intracellular targets and the affected pathways. Applying a quantitative proteomic approach, we analyzed the effects on the protein expression profile of miR-423-5p-transduced PCa cells. Moreover, a computational analysis of predicted targets of miR-423-5p was carried out by using several target prediction tools. Proteomic analysis showed that 63 proteins were differentially expressed in miR-423-5-p-transfected LNCaP cells if compared to controls. Pathway enrichment analysis revealed that stable overexpression of miR-423-5p in LNCaP PCa cells induced inhibition of glycolysis and the metabolism of several amino acids and a parallel downregulation of proteins involved in transcription and hypoxia, the immune response through Th17-derived cytokines, inflammation via amphorin signaling, and ion transport. Moreover, upregulated proteins were related to the S phase of cell cycle, chromatin modifications, apoptosis, blood coagulation, and calcium transport. We identified seven proteins commonly represented in miR-423-5p targets and differentially expressed proteins (DEPs) and analyzed their expression and influence on the survival of PCa patients from publicly accessible datasets. Overall, our findings suggest that miR-423-5p induces alterations in glucose and amino acid metabolism in PCa cells paralleled by modulation of several tumor-associated processes.

Multi-Omic Analysis of Two Common P53 Mutations: Proteins Regulated by Mutated P53 as Potential Targets for Immunotherapy

Simple Summary

TP53 is the most frequently mutated gene in many cancers, but it has failed to be a very effective target for treatment to date. To overcome this, we have examined what else changes in cells when the TP53 gene is mutated. We modified cells that had no TP53 expression to have one of the two most common mutations, either R175H or R273H. We examined how the presence of these TP53 mutations caused cellular changes including microscopic, gene expression and peptide presentation to the immune system. This has allowed us to identify new (secondary) targets that could be used to facilitate the treatment of tumors that harbor p53 mutations.

Abstract

The p53 protein is mutated in more than 50% of human cancers. Mutated p53 proteins not only lose their normal function but often acquire novel oncogenic functions, a phenomenon termed mutant p53 gain-of-function. Mutant p53 has been shown to affect the transcription of a range of genes, as well as protein–protein interactions with transcription factors and other effectors; however, no one has intensively investigated and identified these proteins, or their MHC presented epitopes, from the viewpoint of their ability to act as targets for immunotherapeutic interventions. We investigated the molecular changes that occurred after the TP53 null osteosarcoma cells, SaOS-2, were transfected with one of two conformational p53-mutants, either R175H or R273H. We then examined the phenotypic and functional changes using macroscopic observations, proliferation, gene expression and proteomics alongside immunopeptidome profiling of peptide antigen presentation in the context of major histocompatibility complex (MHC) class I molecules. We identified several candidate proteins in both TP53 mutant cell lines with differential expression when compared to the TP53 null vector control, SaOS-V. Quantitative SWATH proteomics combined with immune-peptidome analysis of the class-I eluted peptides identified several epitopes presented on pMHC and in silico analysis shortlisted which antigens were expressed in a range of cancerous but not adjacent healthy tissues. Out of all the candidates, KLC1 and TOP2A showed high levels of expression in every tumor type examined. From these proteins, three A2 and four pan HLA-A epitopes were identified in both R175H and R273H from TOP2A. We have now provided a short list of future immunotherapy targets for the treatment of cancers harboring mutated TP53.

Extracellular transglutaminase-2, nude or associated with astrocytic extracellular vesicles, modulates neuronal calcium homeostasis

We have uncovered a novel role for astrocytes-derived extracellular vesicles (EVs) in controlling intraneuronal Ca²⁺ concentration ([Ca²⁺]_i) and identified transglutaminase-2 (TG2) as a surface-cargo of astrocytes-derived EVs. Incubation of hippocampal neurons with primed astrocyte-derived EVs have led to an increase in [Ca²⁺]_i, unlike EVs from TG2-knockout astrocytes. Exposure of neurons or brain slices to extracellular TG2 promoted a [Ca²⁺]_i rise, which was reversible upon TG2 removal and was dependent on Ca²⁺ influx through the plasma membrane. Patch-clamp and calcium imaging recordings revealed TG2-dependent neuronal membrane depolarization and activation of inward currents, due to the Na⁺/Ca²⁺-exchanger (NCX) operating in the reverse mode and indirect activation of L-type VOCCs, as indicated by VOCCs/NCX pharmacological inhibitors. A subunit of Na⁺/K⁺-ATPase was selected by comparative proteomics and identified as being functionally inhibited by extracellular TG2, implicating Na⁺/K⁺-ATPase inhibition in NCX reverse mode-switching leading to Ca²⁺ influx and higher basal [Ca²⁺]_i. These data suggest that reactive astrocytes control intraneuronal [Ca²⁺]_i through release of EVs with TG2 as responsible cargo, which could have a significant impact on synaptic activity in brain inflammation.

The Transglutaminase-2 Interactome in the APP23 Mouse Model of Alzheimer's Disease

Amyloid-beta (Aβ) deposition in the brain is closely linked with the development of Alzheimer’s disease (AD). Unfortunately, therapies specifically targeting Aβ deposition have failed to reach their primary clinical endpoints, emphasizing the need to broaden the search strategy for alternative targets/mechanisms. Transglutaminase-2 (TG2) catalyzes post-translational modifications, is present in AD lesions and interacts with AD-associated proteins. However, an unbiased overview of TG2 interactors is lacking in both control and AD brain. Here we aimed to identify these interactors using a crossbreed of the AD-mimicking APP23 mouse model with wild type and TG2 knock-out (TG2^−/−) mice. We found that absence of TG2 had no (statistically) significant effect on Aβ pathology, soluble brain levels of Aβ_1–40 and Aβ_1–42, and mRNA levels of TG family members compared to APP23 mice at 18 months of age. Quantitative proteomics and network analysis revealed a large cluster of TG2 interactors involved in synaptic transmission/assembly and cell adhesion in the APP23 brain typical of AD. Comparative proteomics of wild type and TG2^−/− brains revealed a TG2-linked pathological proteome consistent with alterations in both pathways. Our data show that TG2 deletion leads to considerable network alterations consistent with a TG2 role in (dys)regulation of synaptic transmission and cell adhesion in APP23 brains.

MiR-423-5p prevents MALAT1-mediated proliferation and metastasis in prostate cancer

BACKGROUND

The long non-coding RNA (lncRNA), MALAT1, plays a key role in the development of different cancers, and its expression is associated with worse prognosis in patients. However, its mechanism of action and its regulation are not well known in prostate cancer (PCa). A general mechanism of action of lncRNAs is their interaction with other epigenetic regulators including microRNAs (miRNAs).

METHODS

Using lentiviral stable miRNA transfection together with cell biology functional assays and gene expression/target analysis, we investigated the interaction between MALAT1 and miR-423-5p, defined as a target with in silico prediction analysis, in PCa.

RESULTS

Through bioinformatic analysis of data available from TCGA, we have found that MALAT1 expression correlates with high Gleason grade, metastasis occurrence, and reduced survival in PCa patients. These findings were validated on a TMA of PCa showing a significant correlation between MALAT1 expression with both stage and grading. We report that, in PCa cells, MALAT1 expression and activity is regulated by miR-423-5p that binds MALAT1, downregulates its expression and inhibits its activity in promoting proliferation, migration, and invasion. Using NanoString analysis, we unraveled downstream cell pathways that were affected by miR-423-5p expression and MALAT1 downregulation and identified several alterations in genes that are involved in metastatic response and angiogenic pathways. In addition, we showed that the overexpression of miR-423-5p increases survival and decreases metastases formation in a xenograft mouse model.

CONCLUSIONS

We provide evidence on the role of MALAT1 in PCa tumorigenesis and progression. Also, we identify a direct interaction between miR-423-5p and MALAT1, which results in the suppression of MALAT1 action in PCa.

Carnosine protects stimulus-secretion coupling through prevention of protein carbonyl adduction events in cells under metabolic stress

Type 2 diabetes is characterised by failure to control glucose homeostasis, with numerous diabetic complications attributable to the resulting exposure of cells and tissues to chronic elevated concentrations of glucose and fatty acids. This, in part, results from formation of advanced glycation and advanced lipidation end-products that are able to modify protein, lipid, or DNA structure, and disrupt normal cellular function. Herein we used mass spectrometry to identify proteins modified by two such adduction events in serum of individuals with obesity, type 2 diabetes, and gestational diabetes, along with similar analyses of human and mouse skeletal muscle cells and mouse pancreatic islets exposed to glucolipotoxic stress. We also report that carnosine, a histidine containing dipeptide, prevented 65-90% of 4-hydroxynonenal and 3-nitrotyrosine adduction events, and that this in turn preserved mitochondrial function and protected stimulus-secretion coupling in cells exposed to metabolic stress. Carnosine therefore offers significant therapeutic potential against metabolic diseases.

Supramolecular Chromatographic Separation of C60 and C70 Fullerenes: Flash Column Chromatography vs. High Pressure Liquid Chromatography

A silica-bound C-butylpyrogallol[4]arene chromatographic stationary phase was prepared and characterised by thermogravimetric analysis, scanning electron microscopy, NMR and mass spectrometry. The chromatographic performance was investigated by using C60 and C70 fullerenes in reverse phase mode via flash column and high-pressure liquid chromatography (HPLC). The resulting new stationary phase was observed to demonstrate size-selective molecular recognition as postulated from our in-silico studies. The silica-bound C-butylpyrogallol[4]arene flash and HPLC stationary phases were able to separate a C60- and C70-fullerene mixture more effectively than an RP-C18 stationary phase. The presence of toluene in the mobile phase plays a significant role in achieving symmetrical peaks in flash column chromatography.

A supramolecular cavitand for selective chromatographic separation of peptides using LC-MS/MS: a combined in silico and experimental approach

The chromatographic separation of proteomic standards via a silica immobilized pillararene cavitand has been designed in silico using host–guest binding energy studies and realized experimentally to selectively interact with peptides.

Alterations in the chondrocyte surfaceome in response to pro-inflammatory cytokines

Background

Chondrocytes are exposed to an inflammatory micro-environment in the extracellular matrix (ECM) of articular cartilage in joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). In OA, degenerative changes and low-grade inflammation within the joint transform the behaviour and metabolism of chondrocytes, disturb the balance between ECM synthesis and degradation, and alter the osmolality and ionic composition of the micro-environment. We hypothesize that chondrocytes adjust their physiology to the inflammatory microenvironment by modulating the expression of cell surface proteins, collectively referred to as the ‘surfaceome’. Therefore, the aim of this study was to characterize the surfaceome of primary equine chondrocytes isolated from healthy joints following exposure to the pro-inflammatory cytokines interleukin-1-beta (IL-1β) and tumour necrosis factor-alpha (TNF-α). We employed combined methodology that we recently developed for investigating the surfaceome in stem cells. Membrane proteins were isolated using an aminooxy-biotinylation technique and analysed by mass spectrometry using high throughput shotgun proteomics. Selected proteins were validated by western blotting.

Results

Amongst the 431 unique cell surface proteins identified, a high percentage of low-abundance proteins, such as ion channels, receptors and transporter molecules were detected. Data are available via ProteomeXchange with identifier PXD014773. A high number of proteins exhibited different expression patterns following chondrocyte stimulation with pro-inflammatory cytokines. Low density lipoprotein related protein 1 (LPR-1), thrombospondin-1 (TSP-1), voltage dependent anion channel (VDAC) 1–2 and annexin A1 were considered to be of special interest and were analysed further by western blotting.

Conclusions

Our results provide, for the first time, a repository for proteomic data on differentially expressed low-abundance membrane proteins on the surface of chondrocytes in response to pro-inflammatory stimuli.

Exercise Training in Obese Rats Does Not Induce Browning at Thermoneutrality and Induces a Muscle-Like Signature in Brown Adipose Tissue

Aim: Exercise training elicits diverse effects on brown (BAT) and white adipose tissue (WAT) physiology in rodents housed below their thermoneutral zone (i.e., 28-32°C). In these conditions, BAT is chronically hyperactive and, unlike human residence, closer to thermoneutrality. Therefore, we set out to determine the effects of exercise training in obese animals at 28°C (i.e., thermoneutrality) on BAT and WAT in its basal (i.e., inactive) state. Methods: Sprague-Dawley rats (n = 12) were housed at thermoneutrality from 3 weeks of age and fed a high-fat diet. At 12 weeks of age half these animals were randomized to 4-weeks of swim-training (1 h/day, 5 days per week). Following a metabolic assessment interscapular and perivascular BAT and inguinal (I)WAT were taken for analysis of thermogenic genes and the proteome. Results: Exercise attenuated weight gain but did not affect total fat mass or thermogenic gene expression. Proteomics revealed an impact of exercise training on 2-oxoglutarate metabolic process, mitochondrial respiratory chain complex IV, carbon metabolism, and oxidative phosphorylation. This was accompanied by an upregulation of multiple proteins involved in skeletal muscle physiology in BAT and an upregulation of muscle specific markers (i.e., Myod1, CkM, Mb, and MyoG). UCP1 mRNA was undetectable in IWAT with proteomics highlighting changes to DNA binding, the positive regulation of apoptosis, HIF-1 signaling and cytokine-cytokine receptor interaction. Conclusion: Exercise training reduced weight gain in obese animals at thermoneutrality and is accompanied by an oxidative signature in BAT which is accompanied by a muscle-like signature rather than induction of thermogenic genes. This may represent a new, UCP1-independent pathway through which BAT physiology is regulated by exercise training.

Silica bound co-pillar[4+1]arene as a novel supramolecular stationary phase

A novel co-pillar[4+1]arene incorporating two bromo-octyl substituents has been synthesised for the first time, using microwave irradiation in high yield (88%) in under four minutes, and bound to the surface of chromatographic silica particles. The resulting new stationary phase has been successfully utilised to separate xylene isomers via liquid chromatographic techniques.

PYK2 promotes HER2-positive breast cancer invasion

BACKGROUND

Metformin, a biguanide, is one of the most commonly prescribed treatments for type 2 diabetes and has recently been recommended as a potential drug candidate for advanced cancer therapy. Although Metformin has antiproliferative and proapoptotic effects on breast cancer, the heterogenous nature of this disease affects the response to metformin leading to the activation of pro-invasive signalling pathways that are mediated by the focal adhesion kinase PYK2 in pure HER2 phenotype breast cancer.

METHODS

The effect of metformin on different breast cancer cell lines, representing the molecular heterogenicity of the disease was investigated using in vitro proliferation and apoptosis assays. The activation of PYK2 by metformin in pure HER2 phenotype (HER2+/ER-/PR-) cell lines was investigated by microarrays, quantitative real time PCR and immunoblotting. Cell migration and invasion PYK2-mediated and in response to metformin were determined by wound healing and invasion assays using HER2+/ER-/PR- PYK2 knockdown cell lines. Proteomic analyses were used to determine the role of PYK2 in HER2+/ER-/PR- proliferative, migratory and invasive cellular pathways and in response to metformin. The association between PYK2 expression and HER2+/ER-/PR- patients' cancer-specific survival was investigated using bioinformatic analysis of PYK2 expression from patient gene expression profiles generated by the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) study. The effect of PYK2 and metformin on tumour initiation and invasion of HER2+/ER-/PR- breast cancer stem-like cells was performed using the in vitro stem cell proliferation and invasion assays.

RESULTS

Our study showed for the first time that pure HER2 breast cancer cells are more resistant to metformin treatment when compared with the other breast cancer phenotypes. This drug resistance was associated with the activation of PTK2B/PYK2, a well-known mediator of signalling pathways involved in cell proliferation, migration and invasion. The role of PYK2 in promoting invasion of metformin resistant HER2 breast cancer cells was confirmed through investigating the effect of PYK2 knockdown and metformin on cell invasion and by proteomic analysis of associated cellular pathways. We also reveal a correlation between high level of expression of PYK2 and reduced survival in pure HER2 breast cancer patients. Moreover, we also report a role of PYK2 in tumour initiation and invasion-mediated by pure HER2 breast cancer stem-like cells. This was further confirmed by demonstrating a correlation between reduced survival in pure HER2 breast cancer patients and expression of PYK2 and the stem cell marker CD44.

CONCLUSIONS

We provide evidence of a PYK2-driven pro-invasive potential of metformin in pure HER2 cancer therapy and propose that metformin-based therapy should consider the molecular heterogeneity of breast cancer to prevent complications associated with cancer chemoresistance, invasion and recurrence in treated patients.

Monoamine oxidase-A promotes protective autophagy in human SH-SY5Y neuroblastoma cells through Bcl-2 phosphorylation

Monoamine oxidases (MAOs) are located on the outer mitochondrial membrane and are drug targets for the treatment of neurological disorders. MAOs control the levels of neurotransmitters in the brain via oxidative deamination and contribute to reactive oxygen species (ROS) generation through their catalytic by-product H2O2. Increased ROS levels may modulate mitochondrial function and mitochondrial dysfunction is implicated in a vast array of disorders. However, the downstream effects of MAO-A mediated ROS production in a neuronal model has not been previously investigated. In this study, using MAO-A overexpressing neuroblastoma cells, we demonstrate that higher levels of MAO-A protein/activity results in increased basal ROS levels with associated increase in protein oxidation. Increased MAO-A levels result in increased Lysine-63 linked ubiquitination of mitochondrial proteins and promotes autophagy through Bcl-2 phosphorylation. Furthermore, ROS generated locally on the mitochondrial outer membrane by MAO-A promotes phosphorylation of dynamin-1-like protein, leading to mitochondrial fragmentation and clearance without complete loss of mitochondrial membrane potential. Cellular ATP levels are maintained following MAO-A overexpression and complex IV activity/protein levels increased, revealing a close relationship between MAO-A levels and mitochondrial function. Finally, the downstream effects of increased MAO-A levels are dependent on the availability of amine substrates and in the presence of exogenous substrate, cell viability is dramatically reduced. This study shows for the first time that MAO-A generated ROS is involved in quality control signalling, and increase in MAO-A protein levels leads to a protective cellular response in order to mediate removal of damaged macromolecules/organelles, but substrate availability may ultimately determine cell fate. The latter is particularly important in conditions such as Parkinson's disease, where a dopamine precursor is used to treat disease symptoms and highlights that the fate of MAO-A containing dopaminergic neurons may depend on both MAO-A levels and catecholamine substrate availability.

The vitamin D binding protein axis modifies disease severity in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare disease of women. Decline in lung function is variable, making appropriate targeting of therapy difficult. We used unbiased serum proteomics to identify markers associated with outcome in LAM.101 women with LAM and 22 healthy controls were recruited from the National Centre for LAM in the UK. 152 DNA and serum samples with linked lung function and outcome data were obtained from patients in the National Heart, Lung and Blood Institute LAM Registry in the USA. Proteomic analysis was performed on a discovery cohort of 50 LAM and 20 control serum samples using a SCIEX SWATH mass spectrometric workflow. Protein levels were quantitated by ELISA and single nucleotide polymorphisms in GC (group-specific component) encoding vitamin D binding protein (VTDB) were genotyped.Proteomic analysis showed VTDB was 2.6-fold lower in LAM than controls. Serum VTDB was lower in progressive compared with stable LAM (p=0.001) and correlated with diffusing capacity of the lung for carbon monoxide (p=0.01). Median time to death or lung transplant was reduced by 46 months in those with CC genotypes at rs4588 and 38 months in those with non-A-containing haplotypes at rs7041/4588 (p=0.014 and 0.008, respectively).The VTDB axis is associated with disease severity and outcome, and GC genotype could help predict transplant-free survival in LAM.

A novel spontaneous model of epithelial-mesenchymal transition (EMT) using a primary prostate cancer derived cell line demonstrating distinct stem-like characteristics

Cells acquire the invasive and migratory properties necessary for the invasion-metastasis cascade and the establishment of aggressive, metastatic disease by reactivating a latent embryonic programme: epithelial-to-mesenchymal transition (EMT). Herein, we report the development of a new, spontaneous model of EMT which involves four phenotypically distinct clones derived from a primary tumour-derived human prostate cancer cell line (OPCT-1), and its use to explore relationships between EMT and the generation of cancer stem cells (CSCs) in prostate cancer. Expression of epithelial (E-cadherin) and mesenchymal markers (vimentin, fibronectin) revealed that two of the four clones were incapable of spontaneously activating EMT, whereas the others contained large populations of EMT-derived, vimentin-positive cells having spindle-like morphology. One of the two EMT-positive clones exhibited aggressive and stem cell-like characteristics, whereas the other was non-aggressive and showed no stem cell phenotype. One of the two EMT-negative clones exhibited aggressive stem cell-like properties, whereas the other was the least aggressive of all clones. These findings demonstrate the existence of distinct, aggressive CSC-like populations in prostate cancer, but, importantly, that not all cells having a potential for EMT exhibit stem cell-like properties. This unique model can be used to further interrogate the biology of EMT in prostate cancer.

Cytoplasmic PML promotes TGF-β-associated epithelial-mesenchymal transition and invasion in prostate cancer

Epithelial-mesenchymal transition (EMT) is a key event that is involved in the invasion and dissemination of cancer cells. Although typically considered as having tumour-suppressive properties, transforming growth factor (TGF)-β signalling is altered during cancer and has been associated with the invasion of cancer cells and metastasis. In this study, we report a previously unknown role for the cytoplasmic promyelocytic leukaemia (cPML) tumour suppressor in TGF-β signalling-induced regulation of prostate cancer-associated EMT and invasion. We demonstrate that cPML promotes a mesenchymal phenotype and increases the invasiveness of prostate cancer cells. This event is associated with activation of TGF-β canonical signalling pathway through the induction of Sma and Mad related family 2 and 3 (SMAD2 and SMAD3) phosphorylation. Furthermore, the cytoplasmic localization of promyelocytic leukaemia (PML) is mediated by its nuclear export in a chromosomal maintenance 1 (CRM1)-dependent manner. This was clinically tested in prostate cancer tissue and shown that cytoplasmic PML and CRM1 co-expression correlates with reduced disease-specific survival. In summary, we provide evidence of dysfunctional TGF-β signalling occurring at an early stage in prostate cancer. We show that this disease pathway is mediated by cPML and CRM1 and results in a more aggressive cancer cell phenotype. We propose that the targeting of this pathway could be therapeutically exploited for clinical benefit.

Phenyl Saligenin Phosphate Induced Caspase-3 and c-Jun N-Terminal Kinase Activation in Cardiomyocyte-Like Cells

At present, little is known about the effect(s) of organophosphorous compounds (OPs) on cardiomyocytes. In this study, we have investigated the effects of phenyl saligenin phosphate (PSP), two organophosphorothioate insecticides (diazinon and chlorpyrifos), and their acutely toxic metabolites (diazoxon and chlorpyrifos oxon) on mitotic and differentiated H9c2 cardiomyoblasts. OP-induced cytotoxicity was assessed by monitoring MTT reduction, LDH release, and caspase-3 activity. Cytotoxicity was not observed with diazinon, diazoxon, or chlorpyrifos oxon (48 h exposure; 200 μM). Chlorpyrifos-induced cytotoxicity was only evident at concentrations >100 μM. In marked contrast, PSP displayed pronounced cytotoxicity toward mitotic and differentiated H9c2 cells. PSP triggered the activation of JNK1/2 but not ERK1/2, p38 MAPK, or PKB, suggesting a role for this pro-apoptotic protein kinase in PSP-induced cell death. The JNK1/2 inhibitor SP 600125 attenuated PSP-induced caspase-3 and JNK1/2 activation, confirming the role of JNK1/2 in PSP-induced cytotoxicity. Fluorescently labeled PSP (dansylated PSP) was used to identify novel PSP binding proteins. Dansylated PSP displayed cytotoxicity toward differentiated H9c2 cells. 2D-gel electrophoresis profiles of cells treated with dansylated PSP (25 μM) were used to identify proteins fluorescently labeled with dansylated PSP. Proteomic analysis identified tropomyosin, heat shock protein β-1, and nucleolar protein 58 as novel protein targets for PSP. In summary, PSP triggers cytotoxicity in differentiated H9c2 cardiomyoblasts via JNK1/2-mediated activation of caspase-3. Further studies are required to investigate whether the identified novel protein targets of PSP play a role in the cytotoxicity of this OP, which is usually associated with the development of OP-induced delayed neuropathy.

Data Mining of Gene Arrays for Biomarkers of Survival in Ovarian Cancer

The expected five-year survival rate from a stage III ovarian cancer diagnosis is a mere 22%; this applies to the 7000 new cases diagnosed yearly in the UK. Stratification of patients with this heterogeneous disease, based on active molecular pathways, would aid a targeted treatment improving the prognosis for many cases. While hundreds of genes have been associated with ovarian cancer, few have yet been verified by peer research for clinical significance. Here, a meta-analysis approach was applied to two carefully selected gene expression microarray datasets. Artificial neural networks, Cox univariate survival analyses and T-tests identified genes whose expression was consistently and significantly associated with patient survival. The rigor of this experimental design increases confidence in the genes found to be of interest. A list of 56 genes were distilled from a potential 37,000 to be significantly related to survival in both datasets with a FDR of 1.39859 × 10⁻¹¹, the identities of which both verify genes already implicated with this disease and provide novel genes and pathways to pursue. Further investigation and validation of these may lead to clinical insights and have potential to predict a patient’s response to treatment or be used as a novel target for therapy.

Controlling the dynamics of cell transition in heterogeneous cultures using surface chemistry

Developing materials that can preferentially select defined cancer cell populations for biological characterization will greatly enhance our understanding of cancer cell growth, differentiation, and invasion. The transitional events between epithelial and mesenchymal phenotypes are particularly crucial, as primary tumors and secondary metastasis are generally epithelial in nature, whereas circulating mesenchymal cells derived from primary epithelial cells appear to facilitate the spread of disease and its resistance to therapy. This study describes an amino-functionalized material, which promotes the enrichment of an epithelial phenotype from a single cell line containing both epithelial and mesenchymal subpopulations of cancer cells. The isolation and transitional control of such subpopulations using functional materials will advance understanding of the disease process, have a significant impact on the downstream development of new targeted cancer therapeutics, and also be applicable to tissue engineering and regenerative medicine.

Biomarker identification in breast cancer: Beta-adrenergic receptor signaling and pathways to therapeutic response

Recent preclinical studies have associated beta-adrenergic receptor (β-AR) signaling with breast cancer pathways such as progression and metastasis. These findings have been supported by clinical and epidemiological studies which examined the effect of beta-blocker therapy on breast cancer metastasis, recurrence and mortality. Results from these studies have provided initial evidence for the inhibition of cell migration in breast cancer by beta-blockers and have introduced the beta-adrenergic receptor pathways as a target for therapy. This paper analyzes gene expression profiles in breast cancer patients, utilising Artificial Neural Networks (ANNs) to identify molecular signatures corresponding to possible disease management pathways and biomarker treatment strategies associated with beta-2-adrenergic receptor (ADRB2) cell signaling. The adrenergic receptor relationship to cancer is investigated in order to validate the results of recent studies that suggest the use of beta-blockers for breast cancer therapy. A panel of genes is identified which has previously been reported to play an important role in cancer and also to be involved in the beta-adrenergic receptor signaling.

A simpler method of preprocessing MALDI-TOF MS data for differential biomarker analysis: stem cell and melanoma cancer studies

INTRODUCTION

Raw spectral data from matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) with MS profiling techniques usually contains complex information not readily providing biological insight into disease. The association of identified features within raw data to a known peptide is extremely difficult. Data preprocessing to remove uncertainty characteristics in the data is normally required before performing any further analysis. This study proposes an alternative yet simple solution to preprocess raw MALDI-TOF-MS data for identification of candidate marker ions. Two in-house MALDI-TOF-MS data sets from two different sample sources (melanoma serum and cord blood plasma) are used in our study.

METHOD

Raw MS spectral profiles were preprocessed using the proposed approach to identify peak regions in the spectra. The preprocessed data was then analysed using bespoke machine learning algorithms for data reduction and ion selection. Using the selected ions, an ANN-based predictive model was constructed to examine the predictive power of these ions for classification.

RESULTS

Our model identified 10 candidate marker ions for both data sets. These ion panels achieved over 90% classification accuracy on blind validation data. Receiver operating characteristics analysis was performed and the area under the curve for melanoma and cord blood classifiers was 0.991 and 0.986, respectively.

CONCLUSION

The results suggest that our data preprocessing technique removes unwanted characteristics of the raw data, while preserving the predictive components of the data. Ion identification analysis can be carried out using MALDI-TOF-MS data with the proposed data preprocessing technique coupled with bespoke algorithms for data reduction and ion selection.

Phase I dose escalation pharmacokinetic study in healthy volunteers of resveratrol, a potential cancer chemopreventive agent

The red grape constituent resveratrol possesses cancer chemopreventive properties in rodents. The hypothesis was tested that, in healthy humans, p.o. administration of resveratrol is safe and results in measurable plasma levels of resveratrol. A phase I study of oral resveratrol (single doses of 0.5, 1, 2.5, or 5 g) was conducted in 10 healthy volunteers per dose level. Resveratrol and its metabolites were identified in plasma and urine by high-performance liquid chromatography-tandem mass spectrometry and quantitated by high-performance liquid chromatography-UV. Consumption of resveratrol did not cause serious adverse events. Resveratrol and six metabolites were recovered from plasma and urine. Peak plasma levels of resveratrol at the highest dose were 539 +/- 384 ng/mL (2.4 micromol/L, mean +/- SD; n = 10), which occurred 1.5 h post-dose. Peak levels of two monoglucuronides and resveratrol-3-sulfate were 3- to 8-fold higher. The area under the plasma concentration curve (AUC) values for resveratrol-3-sulfate and resveratrol monoglucuronides were up to 23 times greater than those of resveratrol. Urinary excretion of resveratrol and its metabolites was rapid, with 77% of all urinary agent-derived species excreted within 4 h after the lowest dose. Cancer chemopreventive effects of resveratrol in cells in vitro require levels of at least 5 micromol/L. The results presented here intimate that consumption of high-dose resveratrol might be insufficient to elicit systemic levels commensurate with cancer chemopreventive efficacy. However, the high systemic levels of resveratrol conjugate metabolites suggest that their cancer chemopreventive properties warrant investigation.

Tamoxifen forms DNA adducts in human colon after administration of a single [14C]-labeled therapeutic dose

Tamoxifen is widely prescribed for the treatment of breast cancer and is also licensed in the United States for the prevention of this disease. However, tamoxifen therapy is associated with an increased occurrence of endometrial cancer in women, and there is also evidence that it may elevate the risk of colorectal cancer. The underlying mechanisms responsible for tamoxifen-induced carcinogenesis in women have not yet been elucidated, but much interest has focused on the role of DNA adduct formation. We investigated the propensity of tamoxifen to bind irreversibly to colorectal DNA when given to 10 women as a single [(14)C]-labeled therapeutic (20 mg) dose, approximately 18 h before undergoing colon resections. Using the sensitive technique of accelerator mass spectrometry, coupled with high-performance liquid chromatography separation of enzymatically digested DNA, a peak corresponding to authentic dG-N(2)-tamoxifen adduct was detected in samples from three patients, at levels ranging from 1 to 7 adducts/10(9) nucleotides. No [(14)C]-radiolabel associated with tamoxifen or its major metabolites was detected. The presence of detectable CYP3A4 protein in all colon samples suggests that this tissue has the potential to activate tamoxifen to alpha-hydroxytamoxifen, in addition to that occurring in the systemic circulation, and direct interaction of this metabolite with DNA could account for the binding observed. Although the level of tamoxifen-induced damage displayed a degree of interindividual variability, when present, it was approximately 10 to 100 times higher than that reported for other suspect human colon carcinogens such as 2-amino-1-methyl-6-phenyimidazo[4,5-b]pyridine. These findings provide a mechanistic basis through which tamoxifen could increase the incidence of colon cancers in women.

Quantitation of silibinin, a putative cancer chemopreventive agent derived from milk thistle (Silybum marianum), in human plasma by high-performance liquid chromatography and identification of possible metabolites

Silibinin has recently received attention as a potential cancer chemopreventive agent because of its antiproliferative and anticarcinogenic effects. A simple and specific reversed-phase high-performance liquid chromatography method was developed and validated for the quantitation of silibinin in human plasma. Sample preparation involved simple protein precipitation, and separation was achieved on a Waters Atlantis C18 column with flow rate of 1.0 mL/min at 40 degrees C and UV detection at 290 nm. Silibinin was detected as two peaks corresponding to trans-diastereoisomers. The peak area was linear over the investigated concentration range (0-5000 ng/mL). The limits of detection were 2 and 1 ng/mL for the two diastereoisomers (d1 and d2), with a recovery of 53-58%. This method was utilized to detect silibinin in plasma of colorectal patients after 7 days of treatment with silipide (silibinin formulated with phosphatidyl choline).

Quantitation of trans-resveratrol and detection of its metabolites in human plasma and urine by high performance liquid chromatography

We describe a reversed-phase HPLC method that uses gradient elution and UV detection (325 nm) to determine levels of resveratrol and identify six major conjugated metabolites in the plasma and urine of human volunteers after administration of a single oral dose of 1g. Waters Atlantis C18 3 microm served as the stationary phase. The gradient was formed using ammonium acetate and methanol, containing 2% propan-2-ol. Detection is linear between 5 ng/mL and 500 ng/mL in plasma (5-1000 ng/mL in urine). The coefficient of variation for intra- and inter-day variation is <10%. The average recovery of resveratrol from plasma and urine is 58+/-3%. The data presented in this report demonstrate a rapid, sensitive and accurate method for the analysis of resveratrol and its metabolites in human plasma and urine for pharmacokinetic studies.

Tissue distribution in mice and metabolism in murine and human liver of apigenin and tricin, flavones with putative cancer chemopreventive properties

PURPOSE

The flavones apigenin and tricin, which occur in leafy vegetables and rice bran, respectively, possess cancer chemopreventive properties in preclinical rodent models. Their pharmacology is only poorly understood. We compared their tissue levels in mice in vivo and their metabolism in liver fractions in vitro.

METHODS

Mice received apigenin or tricin (0.2%) with their diet for 5-7 days, and flavone levels were compared in the plasma, liver and gastrointestinal mucosa using HPLC-UV. Flavone metabolism was investigated in murine and human liver microsomes or cytosol in vitro co-incubated with uridine 5'-diphosphoglucuronic acid or 3'-phosphoadenosine-5' phosphosulfate. Flavone metabolites were characterized by on-line HPLC-mass spectrometry.

RESULTS

After dietary administration of flavones for 7 days, levels of tricin in plasma, liver and mucosa exceeded those of apigenin by 350, 33 and 100%, respectively. Apigenin was more rapidly glucuronidated than tricin in liver microsomes, whilst tricin underwent swifter sulfonation than apigenin in liver cytosol. For either flavone the rate of glucuronidation was much faster than that of sulfonation. Flavone monoglucuronides and monosulfates were identified as metabolites in microsomal and cytosolic incubations, respectively.

CONCLUSIONS

When consumed with the diet in mice tricin seems to be more available than apigenin in blood and tissues. Differences in their glucuronidation may account for their differential availability. Thus tricin may have a pharmacokinetic advantage over apigenin. This type of information may help decide which flavonoids to select for clinical development.

Development of analyses by high-performance liquid chromatography and liquid chromatography/tandem mass spectrometry of bilberry (Vaccinium myrtilus) anthocyanins in human plasma and urine

Anthocyanins are potent antioxidants that may possess chronic disease preventive properties. Here, rapid, reliable, and reproducible solid-phase extraction, high-performance liquid chromatography (HPLC), and mass spectrometry techniques are described for the isolation, separation, and identification of anthocyanins in human plasma and urine. Recoveries of cyanidin-3-glucoside (C3G) were 91% from water, 71% from plasma, and 81% from urine. Intra- and interday variations for C3G extraction were 9 and 9.1% in plasma and 7.1 and 9.1% in urine and were less than 15% for all anthocyanins from a standardized bilberry extract (mirtoselect). Analysis of mirtoselect by HPLC with UV detection produced spectra with 15 peaks compatible with anthocyanin components found in mirtoselect within a total run time of 15 min. Chromatographic analysis of human urine obtained after an oral dose of mirtoselect yielded 19 anthocyanin peaks. Mass spectrometric analysis employing multiple reaction monitoring suggests the presence of unchanged anthocyanins and anthocyanidin glucuronide metabolites.

Tamoxifen DNA damage detected in human endometrium using accelerator mass spectrometry

This study was aimed to establish whether tamoxifen binds irreversibly to uterine DNA when given to women. Patients were given a single therapeutic dose of [(14)C]tamoxifen citrate orally (20 mg, 0.37 or 1.85 MBq) approximately 18 h prior to hysterectomy or breast surgery. Nonmalignant uterine tissue was separated into myometrium and endometrium. DNA and protein were isolated and bound radiolabel determined by the sensitive technique of accelerator mass spectrometry. Levels of irreversible DNA binding of tamoxifen in the endometrium of treated patients were 237 +/- 77 adducts/10(12) nucleotides (mean +/- SE, n = 10). In myometrial tissues, a similar extent of DNA binding was detected (492 +/- 112 adducts/10(12) nucleotides). Binding of tamoxifen to endometrial and myometrial proteins was 10 +/- 3 and 20 +/- 4 fmol/mg, respectively. In breast tissue, sufficient DNA could not be extracted but protein binding was an order of magnitude higher than that seen with endometrial proteins (358 +/- 81 fmol/mg). These results demonstrate that after oral administration, tamoxifen forms adducts in human uterine DNA but at low numbers relative to those previously reported in women after long-term tamoxifen treatment where levels, when detected, ranged from 15000 to 130000 adducts/10(12) nucleotides. Our findings support the hypothesis that the low level of DNA adducts in human uterus is unlikely to be involved with endometrial cancer development.

Identification of human CYP forms involved in the activation of tamoxifen and irreversible binding to DNA

This study investigates which CYP forms are responsible for the conversion of tamoxifen to its putative active metabolite alpha-hydroxytamoxifen and irreversible binding to DNA. We have used eight different baculovirus expressed recombinant human CYP forms and liquid chromatography-mass spectrometry to show that only CYP3A4 is responsible for the NADPH-dependent alpha-hydroxylation of tamoxifen. Surprisingly, this CYP did not catalyse the formation of 4-hydroxytamoxifen. We demonstrate for the first time, by means of accelerator mass spectrometry, that CYP3A4 also catalysed the activation of [(14)C]tamoxifen to intermediates that irreversibly bind to exogenous DNA. Incubation of [(14)C]tamoxifen (20.6 kBq, 100 micro M) with CYP3A4, in the presence of NADPH for 60 min led to levels of DNA binding of 39.0+/-9.0 adducts/10(8) nucleotides (mean +/- SE, n = 6). While CYP3A4 converted tamoxifen to N-desmethyltamoxifen (38.3 +/- 7.20 pmol/20 min/pmol CYP, n = 4), the polymorphic CYP2D6 showed the highest activity for producing this metabolite (48.6+/-1.52pmol/20 min/pmol CYP). CYP2D6 was also the most active in catalysing 4-hydroxylation of tamoxifen, although an order of magnitude lower level was also detected with CYP2C19. With tamoxifen as substrate, no 3,4-dihydroxytamoxifen could be detected with any CYP form. CYP2B6 did not catalyse the metabolism or the binding of tamoxifen to DNA. It is concluded that CYP3A4 is the only P450 of those tested that converts tamoxifen to alpha-hydroxytamoxifen and the only one that results in appreciable levels of irreversible binding of tamoxifen to DNA.

Metabolism of the cancer chemopreventive agent curcumin in human and rat intestine

Curcumin, the yellow pigment in turmeric, prevents malignancies in the intestinal tract of rodents. It is under clinical evaluation as a potential colon cancer chemopreventive agent. The systemic bioavailability of curcumin is low, perhaps attributable, at least in part, to metabolism. Indirect evidence suggests that curcumin is metabolized in the intestinal tract. To investigate this notion further, we explored curcumin metabolism in subcellular fractions of human and rat intestinal tissue, compared it with metabolism in the corresponding hepatic fractions, and studied curcumin metabolism in situ in intact rat intestinal sacs. Analysis by high-performance liquid chromatography, with detection at 420 or 280 nm, permitted characterization of curcumin conjugates and reduction products. Chromatographic inferences were corroborated by mass spectrometry. Curcumin glucuronide was identified in intestinal and hepatic microsomes, and curcumin sulfate, tetrahydrocurcumin, and hexahydrocurcumin were found as curcumin metabolites in intestinal and hepatic cytosol from humans and rats. The extent of curcumin conjugation was much greater in intestinal fractions from humans than in those from rats, whereas curcumin conjugation was less extensive in hepatic fractions from humans than in those from rats. The curcumin-reducing ability of cytosol from human intestinal and liver tissue exceeded that observed with the corresponding rat tissue by factors of 18 and 5, respectively. Curcumin sulfate was identified in incubations of curcumin with intact rat gut sacs. Curcumin was sulfated by human phenol sulfotransferase isoenzymes SULT1A1 and SULT1A3. Equine alcohol dehydrogenase catalyzed the reduction of curcumin to hexahydrocurcumin. The results show that curcumin undergoes extensive metabolic conjugation and reduction in the gastrointestinal tract and that there is more metabolism in human than in rat intestinal tissue. The pharmacological implications of the intestinal metabolism of curcumin should be taken into account in the design of future chemoprevention trials of this dietary constituent.

Major inter-species differences in the rates of O-sulphonation and O-glucuronylation of alpha-hydroxytamoxifen in vitro: a metabolic disparity protecting human liver from the formation of tamoxifen-DNA adducts

Tamoxifen is a hepatic genotoxin in rats and mice but a hepatocarcinogen only in rats. It is not associated with DNA adducts and liver tumours in patients. The proposed major pathway for its bioactivation in rats involves alpha-hydroxylation, O-sulphonation and generation of a carbocation that reacts with DNA. Rat liver microsomes catalyse alpha-hydroxylation at approximately 2- and 4-fold the rate achieved by human and murine liver microsomes, respectively. O-glucuronylation will deactivate alpha-hydroxytamoxifen and compete with sulphonation. Rates of O-sulphonation of alpha-hydroxytamoxifen in hepatic cytosol have been determined by a HPLC assay of substrate-dependent 3'-phosphoadenosine 5'-phosphate production. The rank order of O-glucuronylation in hepatic microsomes was estimated by HPLC-mass spectrometry. The rate of sulphonation of trans-alpha-hydroxytamoxifen (25 microM) in cytosol from adult female Sprague-Dawley rats and CD1 mice was 5.3 +/- 0.8 and 3.9 +/- 0.5 pmol/min/mg protein (mean +/- SD, n = 3), respectively. In cytosol fractions from women aged 40-65 years, the rate was 1.1 +/- 0.4 pmol/min/mg protein (mean +/- SD, n = 6). The K(m) for trans-alpha-hydroxytamoxifen in rat, mouse and human cytosol was 84. 6 +/- 3.8, 81.4 +/- 4.6 and 104.3 +/- 5.6 microM (mean +/- SD, n = 3), respectively; the corresponding V:(max) values were 22.4 +/- 3.4, 17.1 +/- 3.1 and 6.3 +/- 1.9 pmol/min/mg protein. These K:(m) were similar to a value obtained by others using purified rat liver hydroxysteroid sulphotransferase a. Turnover of the cis epimer was too slow for accurate determination of rates. Sulphonation of trans-alpha-hydroxytamoxifen in human uterine cytosol was undetectable. The rank order of O-glucuronylation of trans-alpha-hydroxy- tamoxifen in liver microsomes was human > > mouse > rat. In combination, lower rates of alpha-hydroxylation and O-sulphonation and a higher rate of O-glucuronylation in human liver would protect patients from the formation of tamoxifen-DNA adducts.

Alpha-hydroxytamoxifen, a genotoxic metabolite of tamoxifen in the rat: identification and quantification in vivo and in vitro

The metabolic formation of a-hydroxytamoxifen, a reactive metabolite of tamoxifen in rat liver, was characterized and quantified in vitro (hepatic microsomal incubations) and in vivo (bile-duct cannulated animals). This minor metabolite was identified by chromatographic and mass spectral comparisons with the authentic compound. The rates of formation of alpha-hydroxytamoxifen in incubations (30 min) of tamoxifen (25 microM) with liver microsomal preparations from women (pool of six), female CD1 mice or female Sprague-Dawley rats, as quantified by liquid chromatography-mass spectrometry (LC-MS), were 1.15+/-0.03, 0.30+/-0.05 and 2.70+/-0.35 pmol/min/mg protein, respectively. Selective inhibition of microsomal P450 indicated that alpha-hydroxylation was catalysed predominantly by CYP3A in humans. Bile-duct cannulated and anaesthetized female rats and mice given [14C]tamoxifen (43 micromol/kg, i.v.) excreted, respectively, 24 and 21% of the administered radioactivity in bile over 5 and 3.5 h. The major radiolabelled biliary metabolite in rats, characterized by LC-MS after enzymic hydrolysis of conjugates, was the glucuronide of 4-hydroxytamoxifen (10% of dose) and only 0.1% of the dose was recovered as alpha-hydroxytamoxifen. After administration of alpha-hydroxytamoxifen (43 micromol/kg, i.v.) to rats, only 1.19% of the administered compound was recovered from a glucuronide metabolite in bile, indicating a possible 0.84% alpha-hydroxylation of tamoxifen in vivo. There was, however, no indication of the presence in bile of either O-sulphonate or glutathione conjugates derived from alpha-hydroxytamoxifen. This study shows for the first time that alpha-hydroxytamoxifen can be glucuronylated in rat liver. Whereas sulphonation results in electrophilic genotoxic intermediates, glucuronidation may represent a means of detoxifying alpha-hydroxytamoxifen.