Genomic characterization of IDH-mutant astrocytoma progression to grade 4 in the treatment setting

As the progression of low-grade diffuse astrocytomas into grade 4 tumors significantly impacts patient prognosis, a better understanding of this process is of paramount importance for improved patient care. In this project, we analyzed matched IDH-mutant astrocytomas before and after progression to grade 4 from six patients (discovery cohort) with genome-wide sequencing, 21 additional patients with targeted sequencing, and 33 patients from Glioma Longitudinal AnalySiS cohort for validation. The Cancer Genome Atlas data from 595 diffuse gliomas provided supportive information. All patients in our discovery cohort received radiation, all but one underwent chemotherapy, and no patient received temozolomide (TMZ) before progression to grade 4 disease. One case in the discovery cohort exhibited a hypermutation signature associated with the inactivation of the MSH2 and DNMT3A genes. In other patients, the number of chromosomal rearrangements and deletions increased in grade 4 tumors. The cell cycle checkpoint gene CDKN2A, or less frequently RB1, was most commonly inactivated after receiving both chemo- and radiotherapy when compared to other treatment groups. Concomitant activating PDGFRA/MET alterations were detected in tumors that acquired a homozygous CDKN2A deletion. NRG3 gene was significantly downregulated and recurrently altered in progressed tumors. Its decreased expression was associated with poorer overall survival in both univariate and multivariate analysis. We also detected progression-related alterations in RAD51B and other DNA repair pathway genes associated with the promotion of error-prone DNA repair, potentially facilitating tumor progression. In our retrospective analysis of patient treatment and survival timelines (n = 75), the combination of postoperative radiation and chemotherapy (mainly TMZ) outperformed radiation, especially in the grade 3 tumor cohort, in which it was typically given after primary surgery. Our results provide further insight into the contribution of treatment and genetic alterations in cell cycle, growth factor signaling, and DNA repair-related genes to tumor evolution and progression.

A Multi-Stain Breast Cancer Histological Whole-Slide-Image Data Set from Routine Diagnostics

The analysis of FFPE tissue sections stained with haematoxylin and eosin (H&E) or immunohistochemistry (IHC) is essential for the pathologic assessment of surgically resected breast cancer specimens. IHC staining has been broadly adopted into diagnostic guidelines and routine workflows to assess the status of several established biomarkers, including ER, PGR, HER2 and KI67. Biomarker assessment can also be facilitated by computational pathology image analysis methods, which have made numerous substantial advances recently, often based on publicly available whole slide image (WSI) data sets. However, the field is still considerably limited by the sparsity of public data sets. In particular, there are no large, high quality publicly available data sets with WSIs of matching IHC and H&E-stained tissue sections from the same tumour. Here, we publish the currently largest publicly available data set of WSIs of tissue sections from surgical resection specimens from female primary breast cancer patients with matched WSIs of corresponding H&E and IHC-stained tissue, consisting of 4,212 WSIs from 1,153 patients.

Interobserver reproducibility of cribriform cancer in prostate needle biopsies and validation of International Society of Urological Pathology criteria

AIMS

There is strong evidence that cribriform morphology indicates a worse prognosis of prostatic adenocarcinoma. Our aim was to investigate its interobserver reproducibility in prostate needle biopsies.

METHODS AND RESULTS

A panel of nine prostate pathology experts from five continents independently reviewed 304 digitised biopsies for cribriform cancer according to recent International Society of Urological Pathology criteria. The biopsies were collected from a series of 702 biopsies that were reviewed by one of the panellists for enrichment of high-grade cancer and potentially cribriform structures. A 2/3 consensus diagnosis of cribriform and noncribriform cancer was reached in 90% (272/304) of the biopsies with a mean kappa value of 0.56 (95% confidence interval 0.52-0.61). The prevalence of consensus cribriform cancers was estimated to 4%, 12%, 21%, and 20% of Gleason scores 7 (3 + 4), 7 (4 + 3), 8, and 9-10, respectively. More than two cribriform structures per level or a largest cribriform mass with ≥9 lumina or a diameter of ≥0.5 mm predicted a consensus diagnosis of cribriform cancer in 88% (70/80), 84% (87/103), and 90% (56/62), respectively, and noncribriform cancer in 3% (2/80), 5% (5/103), and 2% (1/62), respectively (all P < 0.01).

CONCLUSION

Cribriform prostate cancer was seen in a minority of needle biopsies with high-grade cancer. Stringent diagnostic criteria enabled the identification of cribriform patterns and the generation of a large set of consensus cases for standardisation.

Spatial analysis of histology in 3D: quantification and visualization of organ and tumor level tissue environment

Histological changes in tissue are of primary importance in pathological research and diagnosis. Automated histological analysis requires ability to computationally separate pathological alterations from normal tissue. Conventional histopathological assessments are performed from individual tissue sections, leading to the loss of three-dimensional context of the tissue. Yet, the tissue context and spatial determinants are critical in several pathologies, such as in understanding growth patterns of cancer in its local environment. Here, we develop computational methods for visualization and quantitative assessment of histopathological alterations in three dimensions. First, we reconstruct the 3D representation of the whole organ from serial sectioned tissue. Then, we proceed to analyze the histological characteristics and regions of interest in 3D. As our example cases, we use whole slide images representing hematoxylin-eosin stained whole mouse prostates in a Pten+/- mouse prostate tumor model. We show that quantitative assessment of tumor sizes, shapes, and separation between spatial locations within the organ enable characterizing and grouping tumors. Further, we show that 3D visualization of tissue with computationally quantified features provides an intuitive way to observe tissue pathology. Our results underline the heterogeneity in composition and cellular organization within individual tumors. As an example, we show how prostate tumors have nuclear density gradients indicating areas of tumor growth directions and reflecting varying pressure from the surrounding tissue. The methods presented here are applicable to any tissue and different types of pathologies. This work provides a proof-of-principle for gaining a comprehensive view from histology by studying it quantitatively in 3D.

Artificial intelligence for diagnosis and Gleason grading of prostate cancer: the PANDA challenge

Artificial intelligence (AI) has shown promise for diagnosing prostate cancer in biopsies. However, results have been limited to individual studies, lacking validation in multinational settings. Competitions have been shown to be accelerators for medical imaging innovations, but their impact is hindered by lack of reproducibility and independent validation. With this in mind, we organized the PANDA challenge-the largest histopathology competition to date, joined by 1,290 developers-to catalyze development of reproducible AI algorithms for Gleason grading using 10,616 digitized prostate biopsies. We validated that a diverse set of submitted algorithms reached pathologist-level performance on independent cross-continental cohorts, fully blinded to the algorithm developers. On United States and European external validation sets, the algorithms achieved agreements of 0.862 (quadratically weighted κ, 95% confidence interval (CI), 0.840-0.884) and 0.868 (95% CI, 0.835-0.900) with expert uropathologists. Successful generalization across different patient populations, laboratories and reference standards, achieved by a variety of algorithmic approaches, warrants evaluating AI-based Gleason grading in prospective clinical trials.

Virtual reality for 3D histology: multi-scale visualization of organs with interactive feature exploration

Background

Virtual reality (VR) enables data visualization in an immersive and engaging manner, and it can be used for creating ways to explore scientific data. Here, we use VR for visualization of 3D histology data, creating a novel interface for digital pathology to aid cancer research.

Methods

Our contribution includes 3D modeling of a whole organ and embedded objects of interest, fusing the models with associated quantitative features and full resolution serial section patches, and implementing the virtual reality application. Our VR application is multi-scale in nature, covering two object levels representing different ranges of detail, namely organ level and sub-organ level. In addition, the application includes several data layers, including the measured histology image layer and multiple representations of quantitative features computed from the histology.

Results

In our interactive VR application, the user can set visualization properties, select different samples and features, and interact with various objects, which is not possible in the traditional 2D-image view used in digital pathology. In this work, we used whole mouse prostates (organ level) with prostate cancer tumors (sub-organ objects of interest) as example cases, and included quantitative histological features relevant for tumor biology in the VR model.

Conclusions

Our application enables a novel way for exploration of high-resolution, multidimensional data for biomedical research purposes, and can also be used in teaching and researcher training. Due to automated processing of the histology data, our application can be easily adopted to visualize other organs and pathologies from various origins.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08542-9.

Predicting Molecular Phenotypes from Histopathology Images: A Transcriptome-Wide Expression-Morphology Analysis in Breast Cancer

Molecular profiling is central in cancer precision medicine but remains costly and is based on tumor average profiles. Morphologic patterns observable in histopathology sections from tumors are determined by the underlying molecular phenotype and therefore have the potential to be exploited for prediction of molecular phenotypes. We report here the first transcriptome-wide expression-morphology (EMO) analysis in breast cancer, where individual deep convolutional neural networks were optimized and validated for prediction of mRNA expression in 17,695 genes from hematoxylin and eosin-stained whole slide images. Predicted expressions in 9,334 (52.75%) genes were significantly associated with RNA sequencing estimates. We also demonstrated successful prediction of an mRNA-based proliferation score with established clinical value. The results were validated in independent internal and external test datasets. Predicted spatial intratumor variabilities in expression were validated through spatial transcriptomics profiling. These results suggest that EMO provides a cost-efficient and scalable approach to predict both tumor average and intratumor spatial expression from histopathology images. SIGNIFICANCE: Transcriptome-wide expression morphology deep learning analysis enables prediction of mRNA expression and proliferation markers from routine histopathology whole slide images in breast cancer.

ANHIR: Automatic Non-Rigid Histological Image Registration Challenge

Automatic Non-rigid Histological Image Registration (ANHIR) challenge was organized to compare the performance of image registration algorithms on several kinds of microscopy histology images in a fair and independent manner. We have assembled 8 datasets, containing 355 images with 18 different stains, resulting in 481 image pairs to be registered. Registration accuracy was evaluated using manually placed landmarks. In total, 256 teams registered for the challenge, 10 submitted the results, and 6 participated in the workshop. Here, we present the results of 7 well-performing methods from the challenge together with 6 well-known existing methods. The best methods used coarse but robust initial alignment, followed by non-rigid registration, used multiresolution, and were carefully tuned for the data at hand. They outperformed off-the-shelf methods, mostly by being more robust. The best methods could successfully register over 98% of all landmarks and their mean landmark registration accuracy (TRE) was 0.44% of the image diagonal. The challenge remains open to submissions and all images are available for download.

Abstract 1634: Orthotopic and bone metastasis prostate cancer models using the 22Rv1 cell line

Prostate cancer is the most common cancer in men. Upon diagnosed malignancy the growth of the tumors is androgen driven in a majority of the cases. For that reason, the tumors are treated with androgen deprivation therapy (ADT) to stop or reduce tumor growth. Later, the tumors often become resistant to ADT and at this stage the disease is described as castration-resistant prostate cancer (CRPC). Bone metastasis is one of the hallmark of disease progression. Metastatic disease can be either androgen sensitive or castration resistant (mCRPC) in which the mortality rate is over 50%. Prostate cancer metastases are commonly formed in bones.

The 22Rv1 human prostate carcinoma cell line is androgen sensitive and shown to express androgen receptor (AR). The 22Rv1 cells are an invaluable model system to study AR function, the efficacy of existing drugs and to design novel anti-AR therapies that also target non-truncated regions of AR. The aim of this study was to establish predictive orthotopic and intratibial preclinical in vivo prostate cancer models that can be used in drug development when targeting cancer cells and their local environment.

Male athymic nude mice (5-6 weeks old) and NOG mice (over 20 weeks old) were used in the study. 2.5 × 105 22Rv1 cells were inoculated orthotopically into the prostate of NOG mice, and 0.5 × 106 cells were inoculated intratibially into the bone marrow cavity of athymic nude mice. 22Rv1 human prostate cancer cells (ATCC) were cultured in RPMI 1640 medium supplemented with 10% iFBS, 2 mM L-Glutamine, 10 mM HEPES, 1 mM sodium pyruvate, 4500 mg/l D-Glucose and P/S. Tumor growth was followed by PSA measurements using Human PSA ELISA assay. In addition, in the intratibial model, tumor-induced bone changes were monitored by X-ray imaging of the hind limbs. Prostates and hind limbs were collected at sacrifice, fixed in 10% NBF, and processed to paraffin blocks for further histological analysis. Sections of prostate were stained with hematoxylin-eosin (HE) and AR. Tumor-bearing and contralateral (healthy) tibias were stained with HE - OrangeG, MGT, TRAP, and AR. For enhanced visualization of tumor models in 3D, we reconstructed the tissue from serial sections using a tailored computational pipeline based on applying a deformable model for corresponding points from adjacent sections.

The observed tumor take rate was 100% in both models. Confirmed by IHC, tumors formed in both the orthotopic and intratibial models expressed AR. 22Rv1 cells formed osteoblastic - lytic mixed bone lesions in the intratibial model. Based on lesion areas, randomization of the tumor bearing mice in the intratibial model can be done after 2 weeks from cancer cell inoculation. In conclusion, both presented models are suited to test the anticancer efficacy of new drug candidates. In addition, the intratibial model can be used to test the efficacy of novel drug candidates on prostate cancer cells in bone metastatic microenvironment.

Citation Format: Justyna Zdrojewska, Tiina E. Kähkönen, Jenni H. Mäki-Jouppila, Masi Valkonen, Pekka Ruusuvuori, Jussi M. Halleen, Jenni Bernoulli. Orthotopic and bone metastasis prostate cancer models using the 22Rv1 cell line [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1634.

Microbial characteristics in homes of asthmatic and non-asthmatic adults in the ECRHS cohort

Microbial exposures in homes of asthmatic adults have been rarely investigated; specificities and implications for respiratory health are not well understood. The objectives of this study were to investigate associations of microbial levels with asthma status, asthma symptoms, bronchial hyperresponsiveness (BHR), and atopy. Mattress dust samples of 199 asthmatics and 198 control subjects from 7 European countries participating in the European Community Respiratory Health Survey II study were analyzed for fungal and bacterial cell wall components and individual taxa. We observed trends for protective associations of higher levels of mostly bacterial markers. Increased levels of muramic acid, a cell wall component predominant in Gram-positive bacteria, tended to be inversely associated with asthma (OR's for different quartiles: II 0.71 [0.39-1.30], III 0.44 [0.23-0.82], and IV 0.60 [0.31-1.18] P for trend .07) and with asthma score (P for trend .06) and with atopy (P for trend .02). These associations were more pronounced in northern Europe. This study among adults across Europe supports a potential protective effect of Gram-positive bacteria in mattress dust and points out that this may be more pronounced in areas where microbial exposure levels are generally lower.

Insight to Nanoparticle Size Analysis-Novel and Convenient Image Analysis Method Versus Conventional Techniques

The aim of this paper is to introduce a new image analysis program "Nanoannotator" particularly developed for analyzing individual nanoparticles in transmission electron microscopy images. This paper describes the usefulness and efficiency of the program when analyzing nanoparticles, and at the same time, we compare it to more conventional nanoparticle analysis techniques. The techniques which we are concentrating here are transmission electron microscopy (TEM) linked with different image analysis methods and X-ray diffraction techniques. The developed program appeared as a good supplement to the field of particle analysis techniques, since the traditional image analysis programs suffer from the inability to separate the individual particles from agglomerates in the TEM images. The program is more efficient, and it offers more detailed morphological information of the particles than the manual technique. However, particle shapes that are very different from spherical proved to be problematic also for the novel program. When compared to X-ray techniques, the main advantage of the small-angle X-ray scattering (SAXS) method is the average data it provides from a very large amount of particles. However, the SAXS method does not provide any data about the shape or appearance of the sample.

Endotoxin, extracellular polysaccharides, and β(1-3)-glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project

Early-life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early-life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early-life levels of endotoxin, extracellular polysaccharides (EPS), and β(1-3)-glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1-3)-glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1-3)-glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early-life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries.

PRACTICAL IMPLICATIONS

This study adds evidence of variability in the levels of indoor endotoxin, extracellular polysaccharide, and β(1-3)-glucans across four geographically spread European regions. Furthermore, we observed heterogeneity across regions in the effect of exposure determinants. We hypothesize that the variations observed in our study may play a role in the differences in asthma and allergies prevalences across countries.

The ire1 and ptc2 genes involved in the unfolded protein response pathway in the filamentous fungus Trichoderma reesei

A signal transduction pathway called the unfolded protein response is activated when increased levels of misfolded proteins or incorrectly assembled subunits accumulate in the endoplasmic reticulum (ER). The expression of several genes for ER-resident foldases and chaperones, as well as genes encoding proteins that are involved in functions associated with the secretory process, are induced by this pathway. This paper describes the cloning and characterisation of genes for two components of the pathway, ire1 and ptc2, from the filamentous fungus Trichoderma reesei (Hypocrea jecorina). The data presented demonstrates that the T. reesei genes can complement Saccharomyces cerevisiae mutants that are deficient in the corresponding homologues. The T. reesei IREI protein has intrinsic kinase activity, as revealed by an in vitro autophosphorylation assay. Overexpression of ire1 in a T. reesei strain that expresses a foreign protein (laccase 1 from Phlebia radiata), results in up-regulation of the UPR pathway, as indicated by the increased expression levels of the known UPR target genes bip1 and pdi1. Splicing of the mRNA encoding the transcription factor HAC1 is also observed. Other genes encoding proteins from different parts of the secretory pathway also respond to ire1 overexpression.

Bioelectromagnetic localization of a pacing catheter in the heart

The accuracy of localizing source currents within the human heart by non-invasive magneto- and electrocardiographic methods was investigated in 10 patients. A non-magnetic stimulation catheter inside the heart served as a reference current source. Biplane fluoroscopic imaging with lead ball markers was used to record the catheter position. Simultaneous multichannel magnetocardiographic (MCG) and body surface potential mapping (BSPM) recordings were performed during catheter pacing. Equivalent current dipole localizations were computed from MCG and BSPM data, employing standard and patient-specific boundary element torso models. Using individual models with the lungs included, the average MCG localization error was 7+/-3 mm, whereas the average BSPM localization error was 25+/-4 mm. In the simplified case of a single homogeneous standard torso model, an average error of 9+/-3 mm was obtained from MCG recordings. The MCG localization accuracies obtained in this study imply that the capability of multichannel MCG to locate dipolar sources is sufficient for clinical purposes, even without constructing individual torso models from x-ray or from magnetic resonance images.

Intense physical training decreases circulating antioxidants and endothelium-dependent vasodilatation in vivo

Physical training increases free radical production and consumes antioxidants. It has previously been shown that acute exercise markedly increases the susceptibility of LDL to oxidation but whether such changes are observed during physical training is unknown. We measured circulating antioxidants, lipids and lipoproteins, and blood flow responses to intrabrachial infusions of endothelium-dependent (acetylcholine, ACh, L-N-monomethyl-arginine, L-NMMA) and -independent (sodium nitroprusside, SNP) vasoactive agents, before and after 3 months of running in 9 fit male subjects. Maximal aerobic power increased from 53 +/- 1 to 58 +/- 2 ml/kg min (P < 0.02). All circulating antioxidants (uric acid, SH-groups, alpha-tocopherol, beta-carotene, retinol) except ascorbate decreased significantly during training. Endothelium-dependent vasodilatation in forearm vessels decreased by 32-35% (P < 0.05), as determined from blood flow responses to both a low (10.8 +/- 2.1 vs. 7.3 +/- 1.5 ml/dl min, 0 vs. 3 months) and a high (14.8 +/- 2.6 vs. 9.6 +/- 1.8) ACh dose. The % endothelium-dependent blood flow (% decrease in basal flow by L-NMMA), decreased through training from 37 +/- 3 to 22 +/- 7% (P < 0.05). Blood flow responses to SNP remained unchanged. The decrease in uric acid was significantly correlated with the change in the % decrease in blood flow by L-NMMA (r = 0.74, P < 0.05). The lag time for the susceptibility of plasma LDL to oxidation in vitro, LDL size and the concentration of LDL cholestetol remained unchanged. We conclude that relatively intense aerobic training decreases circulating antioxidant concentrations and impairs endothelial function in forearm vessels.

A marathon run increases the susceptibility of LDL to oxidation in vitro and modifies plasma antioxidants

Physical activity increases the production of oxygen free radicals, which may consume antioxidants and oxidize low-density lipoprotein (LDL). To determine whether this occurs during strenuous aerobic exercise, we studied 11 well-trained runners who participated in the Helsinki City Marathon. Blood samples were collected before, immediately after, and 4 days after the race to determine its effect on circulating antioxidants and LDL oxidizability in vitro. LDL oxidizability was increased as determined from a reduction in the lag time for formation of conjugated dienes both immediately after (180 +/- 7 vs. 152 +/- 4 min, P < 0.001) and 4 days after (155 +/- 7 min, P < 0.001) the race. No significant changes in lipid-soluble antioxidants in LDL or in the peak LDL particle size were observed after the race. Total peroxyl radical trapping antioxidant capacity of plasma (TRAP) and uric acid concentrations were increased after the race, but, except for TRAP, these changes disappeared within 4 days. Plasma thiol concentrations were reduced after the race. No significant changes were observed in plasma ascorbic acid, alpha-tocopherol, beta-carotene, and retinol concentrations after the marathon race. We conclude that strenuous aerobic exercise increases the susceptibility of LDL to oxidation in vitro for up to 4 days. Although the increase in the concentration of plasma TRAP reflects an increase of plasma antioxidant capacity, it seems insufficient to prevent the increased susceptibility of LDL to oxidation in vitro, which was still observed 4 days after the race.

Passive smoking induces atherogenic changes in low-density lipoprotein

BACKGROUND

According to the American Heart Association, passive smoking is an important risk factor for coronary heart disease (CHD), but the mechanisms underlying this association are not fully understood. We studied the acute effect of passive smoking on the factors that influence the development of CHD: the antioxidant defense of human serum, the extent of lipid peroxidation, and the accumulation of LDL cholesterol in cultured human macrophages, the precursors of foam cells in atherosclerotic lesions.

METHODS AND RESULTS

Blood samples were collected during 2 ordinary working days from healthy, nonsmoking subjects (n=10) before and after (up to 5.5 hours) spending half an hour in a smoke-free area (day 1) or in a room for smokers (day 2). Passive smoking caused an acute decrease (1.5 hours after exposure) in serum ascorbic acid (P<.001) and in serum antioxidant defense (P<.001), a decreased capacity of LDL to resist oxidation (P<.01), and the appearance of increased amounts of lipid peroxidation end products in serum (P<.01). Finally, LDL isolated from subjects after passive smoking was taken up by cultured macrophages at an increased rate (P<.05).

CONCLUSIONS

Exposure of nonsmoking subjects to secondhand smoke breaks down the serum antioxidant defense, leading to accelerated lipid peroxidation, LDL modification, and accumulation of LDL cholesterol in human macrophages. These data provide the pathophysiological background for the recent epidemiological evidence about the increased CHD risk among passive smokers.

Spectrophotometric assay for total peroxyl radical-trapping antioxidant potential in human serum

Antioxidants prevent modification of low density lipoprotein (LDL) by free radicals and possibly also atheroma formation. The capacity of human serum to resist attacks by free radicals is measured by the total peroxyl radical-trapping potential (TRAP). Its measurement has thus far required equipment not available in many clinical laboratories such as a thermostated oxygen electrode cell or a luminometer. To develop a simpler method we used a free radical probe, dichlorofluorescin-diacetate (DCFH-DA), described before in studies of respiratory burst in inflammatory cells. Its oxidation by radicals from thermal decomposition of 2,2'-diazobis(2-amidinopropane)dihydrochloride (AAPH) converts this compound to highly fluorescent dichlorofluorescein (DCF). The DCF also has absorbance at 504 nm thus enabling the determination of TRAP either fluorometrically or spectrophotometrically. Increasing the concentration of AAPH enables the measurement of DCF formation and its inhibition by serum samples at room temperature. The intra- and interassay coefficients of variation of this assay are 3.4% and 4.6%, respectively. The mean value for serum TRAP of healthy subjects is 1155 mumol/l (n = 38). The TRAP in human serum can be increased by adding various antioxidant substances to the assay in vitro or by dietary supplementation of healthy subjects with vitamin E in vivo (P < 0.025). An increase was also found in serum vitamin E levels (P < 0.0001) and in the length of the time human LDL is able to resist oxidation (P < 0.05). Thus the determination of TRAP by this method, which requires only commercially available chemicals, can be used for the evaluation of phenomena associated with lipid accumulation in human artery wall.