Reliable chromatographic assay for measuring of indoleamine 2,3-dioxygenase 1 (IDO1) activity in human cancer cells

Derivative spectrophotometry-assisted determination of tryptophan metabolites emerges host and intestinal flora dysregulations during sepsis

Sepsis is a life-threatening condition characterized by organ dysfunction resulting from a dysregulated host response to infection. Dysregulated tryptophan (TRP) metabolites serve as significant indicators for endogenous immune turnovers and abnormal metabolism in the intestinal microbiota during sepsis. Therefore, a high coverage determination of TRP and its metabolites in sepsis is beneficial for the diagnosis and prognosis of sepsis, as well as for understanding the underlying mechanism of sepsis development. However, similar structures in TRP metabolites make it challenging for separation and metabolite identification. Here, high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) was developed to determine TRP metabolites in rat serum. The first-order derivative spectrophotometry of targeted metabolites in the serum was investigated and proved to be promising for chromatographic peak annotation across different columns and systems. The established method separating the targeted metabolites was optimized and validated to be sensitive and accurate. Application of the method revealed dysregulated TRP metabolites, associated with immune disorders and NAD + metabolism in both the host and gut flora in septic rats. Our findings indicate that the derivative spectrophotometry-assisted method enhances metabolite identifications for the chromatographic systems based on DAD detectors and holds promise for precision medicine in sepsis.

The unique monoclonal antibodies and immunochemical assay for comprehensive determination of the cell-bound and soluble HER2 in different biological samples

The expression of the HER2 (human epidermal growth factor receptor 2) protein in cancer cells is a well-established cancer marker used for diagnostic and therapeutic purposes in modern treatment protocols, especially in breast cancer. The gold-standard immunohistochemical diagnostic methods with the specific anti-HER2 antibodies are utilized in the clinic to measure expression level of the membrane-bound receptor. However, a soluble extracellular domain (ECD) of HER2 is released to the extracellular matrix, thus the blood assays for HER2 measurements present an attractive way for HER2 level determination. There is a need for accurate and validated assays that can be used to correlate the concentration of the circulating HER2 protein with disease clinical manifestations. Here we describe two monoclonal antibodies binding HER2 with a unique sequence of the complementarity-determining regions that recognize HER2 ECD. Development and validation of the sandwich enzyme-linked immunosorbent assay (ELISA) for quantification of the soluble HER2 in a variety of biological samples is also presented. The assay provides HER2 quantitation within a concentrations range from 1.56 to 100 ng/ml with sensitivity at the level of 0.5 ng/ml that meets the expectations for measurements of HER2 in the blood and tumor tissue samples. The method presents satisfactory intra- and inter-assay precision and accuracy for immunochemical quantification of biomarkers in biological samples. The utility of the generated monoclonal anti-HER2 antibodies has been confirmed for use in the precise measurement of HER2 (both cell-bound and soluble) in several types of biological material, including serum, solid tumor tissue, and cell culture medium. Additionally, the developed immunochemical tools have a potential for HER2 detection, not only in a wide range of sample types but also independently of the sample storage/pre-processing, allowing for comprehensive HER2 analysis in tissue (IHC), cultured cells (immunofluorescence) and blood (ELISA).

Involvement of the kynurenine pathway in breast cancer: updates on clinical research and trials

Breast cancer (BrCa) is the leading cause of cancer incidence and mortality in women worldwide. While BrCa treatment has been shown to be highly successful if detected at an early stage, there are few effective strategies to treat metastatic tumours. Hence, metastasis remains the main cause in most of BrCa deaths, highlighting the need for new approaches in this group of patients. Immunotherapy has been gaining attention as a new treatment for BrCa metastasis and the kynurenine pathway (KP) has been suggested as one of the potential targets. The KP is the major biochemical pathway in tryptophan (TRP) metabolism, catabolising TRP to nicotinamide adenine dinucleotide (NAD+). The KP has been reported to be elevated under inflammatory conditions such as cancers and that its activity suppresses immune surveillance. Dysregulation of the KP has previously been reported implicated in BrCa. This review aims to discuss and provide an update on the current mechanisms involved in KP-mediated immune suppression and cancer growth. Furthermore, we also provide a summary on 58 studies about the involvement of the KP and BrCa and five clinical trials targeting KP enzymes and their outcome.

Improved Voltammetric Determination of Kynurenine at the Nafion Covered Glassy Carbon Electrode - Application in Samples Delivered from Human Cancer Cells

Nowadays, development of analytical methods responding to a need for rapid and accurate determination of human metabolites is highly desirable. Herein, an electrochemical method employing a Nafion-coated glassy carbon electrode (Nafion/GCE) has been developed for reliable determination of kynurenine (a key tryptophan metabolite) using a differential pulse adsorptive stripping voltammetry. To our knowledge, this is the first analytical method to allow for kynurenine determination at the Nafion-coated electrode. The methodology involves kynurenine pre-concentration in 0.1 M H₂SO₄ in the Nafion film at the potential of +0.5 V and subsequent stripping from the electrode by differential pulse voltammetry. Under optimal conditions, the sensor can detect 5 nM kynurenine (for the accumulation time of 60 seconds), but the limit of detection can be easily lowered to 0.6 nM by prolonging the accumulation time to 600 seconds. The sensor shows sensitivity of 36.25 μAμM⁻¹cm⁻² and 185.50 μAμM⁻¹cm⁻² for the accumulation time of 60 and 600 seconds, respectively. The great advantage of the proposed method is easy sensor preparation, employing drop coating method, high sensitivity, short total analysis time, and no need for sample preparation. The method was validated for linearity, precision, accuracy (using a high-performance liquid chromatography), selectivity (towards tryptophan metabolites and different amino acids), and recovery. The comprehensive microscopic and electrochemical characterization of the Nafion/GCE was also conducted with different methods including atomic force microscopy (AFM), optical profilometry, time-of-flight secondary ion mass spectrometry (TOF-SIMS), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The method has been applied with satisfactory results for determination of kynurenine concentration in a culture medium collected from the human ovarian carcinoma cells SK-OV-3 and to measure IDO enzyme activity in the cancer cell extracts.