Background:Proteins released by tumor cells can bind to serum albumin, leading to structural and functional modifications. We used electron spin resonance (ESR) spectroscopy to measure these changes in serum albumin and evaluate their utility for the diagnosis and monitoring of cancer. Methods: We used an ESR spectrometer and 16-doxyl stearic acid as spin probe to measure conformational changes in albumin in blood samples from a population of healthy donors and volunteers (n ؍ 349), patients with a wide variety of hematologic and nonhematologic malignancy (n ؍ 135), and patients with chronic diseases such as gastrointestinal and pulmonary disease, diabetes, and cirrhosis (n ؍ 91). We added differing amounts of 16-doxyl stearic acid spin probe in ethanol to 50 L of serum from each patient to create 3 different aliquots that differed in concentration of spin probe and ethanol, then incubated the aliquots for 10 min at 37°C with continuous shaking. We measured the ESR spectra of each aliquot in triplicate and used proprietary software (MedInnovation GmbH) to evaluate the ESR spectrum for differences between cancer patients and the other groups. Results: The diagnostic sensitivity and specificity of this test were 87.4% and 95.7%, respectively, for differentiating healthy individuals from cancer patients and 87.4%, and 85.7% for differentiating cancer patients
Human serum albumin accumulates low molecular weight biomarkers related to cancer. This accumulation can lead to allosteric modification of albumin and change its ability to bind essential fatty acids. Using 16-doxyl-stearic acid spin probe, which is specific for albumin, the serum samples of 98 patients with a variety of cancer types and 86 cancer free individuals were analysed by electron spin resonance (ESR) spectroscopy in order to evaluate cancer-induced modifications that occur to albumin. The ESR spectra showed significant differences between the investigated groups. These differences were most apparent in the intensities and widths of the spectral lines corresponding to the different types of albumin binding sites.
Diagnostic medicine has seen significant changes during the past decade. The emergence of proteomics and genomics has significantly increased our understanding of disease. These fields have also revealed the vast array of proteins that are expressed in various disease processes, such as cancer. Measurement of these unique proteins expressed in certain diseases may offer diagnostic clues or allow patient prognosis to be assessed. Another approach is to measure the effects that these ligands have on the structure and function of albumin. Albumin is known to play an important role in modulating the serum concentrations of various proteins produced by tumor cells. In this review, we introduce the reader to the technique of spin labeling followed by electron paramagnetic resonance spectroscopy. This method is a powerful tool for evaluating the structural and functional changes that can occur to albumin following the binding of various ligands. We describe the utility of this technique for the diagnosis of cancer and sepsis, as well as some other novel potential applications.
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