Nucleosomes Indicate the in vitro Radiosensitivity of Irradiated Bronchoepithelial and Lung Cancer Cells

Circulating nucleosomes as potential biomarkers for cancer diagnosis and treatment monitoring

Nucleosomes play a crucial role in regulating gene expression through their composition and post-translational modifications. When cells die, intracellular endonucleases are activated and cleave chromatin into oligo- and mono-nucleosomes, which are then released into the body fluids. Studies have shown that the levels of nucleosomes are increased in serum and plasma in various cancer types, suggesting that analysis of circulating nucleosomes can provide an initial assessment of carcinogenesis. However, it should be noted that elevated serum nucleosome levels may not accurately diagnose certain tumor types, as increased cell death may occur in different pathological conditions. Nevertheless, detection of circulating nucleosomes and their histone modifications, along with specific tumor markers, can help diagnose certain types of cancer. Furthermore, monitoring changes in circulating nucleosome levels during chemotherapy or radiotherapy in patients with malignancies can provide valuable insights into clinical outcomes and therapeutic efficacy. The utilization of circulating nucleosomes as biomarkers is an exciting and emerging area of research, with the potential for early detection of various diseases and monitoring of treatment response. Integrating nucleosome-based biomarkers with existing ones may improve the specificity and sensitivity of current assays, offering the possibility of personalized precision medical treatment for patients.

Circulating nucleosomes and biomarkers of immunogenic cell death as predictive and prognostic markers in cancer patients undergoing cytotoxic therapy

INTRODUCTION

Immunogenic cell death markers are released from apoptotic and necrotic cells upon pathologic or therapeutic causes and stimulate the innate and adaptive immune system. Cell death products such as nucleosomes, damage-associated molecular pattern (DAMP) molecules such as the high-mobility group box 1 protein (HMGB1) and its receptor of advanced glycation end products (sRAGE) are supposed to play an essential role in driving this process. However, this immunogenic activation may have dual effects, either by sensitizing the immune system for more efficient tumor cell removal or by creating a favorable tumor microenvironment that facilitates tumor growth, proliferation and invasiveness.

AREAS COVERED

Here, we review recent findings on the relevance of serum nucleosomes, DNAse activity, HMGB1 and sRAGE as biomarkers for the diagnosis, prognosis and therapy prediction in cancer disease.

EXPERT OPINION

In comparison with healthy controls, cancer patients demonstrated elevated serum levels of nucleosomes and HMGB1 while sRAGE levels were decreased. During locoregional and systemic cytotoxic therapies, a high release of nucleosomes and HMGB1 as well as low release of sRAGE before and during the initial phase of the treatment was found to be associated with poor response to the therapy and patient survival. Therefore, immunogenic cell death markers are promising tools for the prognosis, therapy prediction and monitoring in cancer patients.

In vitro molecular magnetic resonance imaging detection and measurement of apoptosis using superparamagnetic iron oxide + antibody as ligands for nucleosomes

Recent research in cell biology as well as oncology research has focused on apoptosis or programmed cell death as a means of quantifying the induced effects of treatment. A hallmark of late-stage apoptosis is nuclear fragmentation in which DNA is degraded to release nucleosomes with their associated histones. In this work, a method was developed for detecting and measuring nucleosome concentration in vitro with magnetic resonance imaging (MRI). The indirect procedure used a commercially available secondary antibody-superparamagnetic iron oxide (SPIO) particle complex as a contrast agent that bound to primary antibodies against nucleosomal histones H4, H2A and H2B. Using a multiple-echo spin-echo sequence on a 1.5 T clinical MRI scanner, significant T₂ relaxation enhancement as a function of in vitro nucleosomal concentration was measured. In addition, clustering or aggregation of the contrast agent was demonstrated with its associated enhancement in T₂ effects. The T₂ clustering enhancement showed a complex dependence on relative concentrations of nucleosomes, primary antibody and secondary antibody + SPIO. The technique supports the feasibility of using MRI measurements of nucleosome concentration in blood as a diagnostic, prognostic and predictive tool in the management of cancer.

Screening for circulating nucleic acids and caspase activity in the peripheral blood as potential diagnostic tools in lung cancer

The focus of the current investigational study was to examine whether circulating nucleic acids (i.e., DNA and microRNAs) have the potential to become suitable blood-based markers for diagnosis and progression of lung cancer. The concentrations of cell-free DNA and four circulating microRNAs (miR10b, miR34a, miR141 and miR155) as well as the caspase activity were measured in serum of 35 lung cancer patients (19 non-small-cell lung cancer, 8 small cell lung cancer patients and 8 patients with indefinite cancer type), 7 patients with benign lung tumors and 28 healthy individuals by PicoGreen, TaqMan MicroRNA, and Caspase-Glo®3/7 assay, respectively. The data were correlated with the established risk factors for lung cancer progression. The concentrations of cell-free DNA (p = 0.0001), serum microRNAs (p = 0.0001) and caspase activities (p = 0.0001) significantly discriminated cancer patients from healthy individuals. Serum DNA, caspase activities and RNA levels could not distinguish between patients with benign lung disease and cancer patients. However, the levels of miR10b (p = 0.002), miR141 (p = 0.0001) and miR155 (p = 0.007) were significantly higher in lung cancer patients than those in patients with benign disease. As determined by the Spearman-Rho test, high levels of cell-free DNA significantly correlated with elevated circulating caspase activities (p = 0.0001). In lung cancer patients high serum miR10b values associated with lymph node metastasis (p < 0.03) and elevated levels of TPA (tissue polypeptide antigen, p = 0.01), whereas high serum miR141 values associated with elevated levels of uPA (urokinase plasminogen activator, p = 0.02). The findings of our pilot study suggest that the assays for circulating DNA, microRNAs and caspase activities in blood might become novel minimally invasive diagnostic tools for detection and risk assessment of lung cancer, provided that their clinical utility can be confirmed in larger prospective trials.

Clinical use of circulating nucleosomes

Nucleosomes, complexes of DNA and histone proteins, are released from dying and stressed cells into the blood circulation. Concentrations of circulating nucleosomes in plasma and serum are frequently found to be elevated in various cancers, and also in such acute conditions as stroke, trauma, and sepsis as well as in autoimmune diseases. The first part of this review focuses on the structural and functional properties of nucleosomes, the potential sources of nucleosome release into the circulation, the metabolism of circulating nucleosomes, and their pathophysiological role in disease. It goes on to describe the relevance of circulating nucleosomes in the diagnosis and prognosis of non-malignant conditions such as sepsis, stroke, and autoimmune disease. Finally, it describes the clinical value of nucleosomes in the diagnosis, staging, prognosis, and monitoring of therapy in cancer; in particular, their potential as a new diagnostic tool for the early estimation of response to cytotoxic cancer therapy is emphasized.

Clinical relevance of circulating nucleosomes in cancer

Nucleosomes, complexes of DNA and histone proteins, are released during cell death into the blood circulation. Elevated serum and plasma levels have been found in various forms of cancer, but also in autoimmune diseases and acute situations such as stroke, trauma, and during sepsis. Here, the clinical relevance of circulating nucleosomes for diagnosis, staging, prognosis, and therapeutic monitoring of cancer is reviewed. Several studies have shown that levels of nucleosomes are significantly higher in serum and plasma of cancer patients in comparison to healthy controls. However, because of elevations of nucleosome levels in patients with benign diseases relevant for differential diagnosis, they are not suitable for cancer diagnosis. Concerning tumor staging, nucleosome levels correlate with tumor stage and presence of metastases in gastrointestinal cancer, but not in other tumor types. Prognostic value of circulating nucleosomes is found in lung cancer in univariate analyses, but not in multivariate analyses. Circulating nucleosomes are most informative for the monitoring of cytotoxic therapy. Strongly decreasing levels are mainly found in patients with remission of disease, whereas constantly high or increasing values are associated with progressive disease during chemo- and radiotherapy. In addition, therapy outcome is already indicated by the nucleosomal course during the first week of chemo- and radiotherapy in patients with lung, pancreatic, and colorectal cancer as well as in hematologic malignancies. Despite their non-tumor-specificity, kinetics of nucleosomes are valuable markers for the early estimation of therapeutic efficacy and may be helpful to adapting early cancer therapy in the future.

Early and specific prediction of the therapeutic efficacy in non-small cell lung cancer patients by nucleosomal DNA and cytokeratin-19 fragments

Facing an era of promising new antitumor therapies, predictors of therapy response are needed for the individual management of treatment. In sera collected prospectively from 311 patients with advanced non-small cell lung cancer receiving first-line chemotherapy, changes in nucleosomal DNA fragments, cytokeratin-19 fragments (CYFRA 21-1), carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), and progastrin-releasing peptide (ProGRP) were investigated and correlated with therapy response. In univariate analysis, high levels, slower and incomplete decline in nucleosomal DNA, CYFRA 21-1, and CEA predicted poor outcome. DNA concentrations at day 8 of the first therapeutic cycle and CYFRA 21-1 before start of the second cycle were identified as best predictive variables. In multivariate analysis, they predicted progression with a specificity of 100% in 29% of the cases earlier than imaging techniques. Thus, nucleosomal DNA and CYFRA 21-1 specifically identify a subgroup of patients with insufficient therapy response at the early treatment phase and showed to be valuable for disease management.

Nucleosomes in colorectal cancer patients during radiochemotherapy

Apoptotic markers and tumor-associated antigens might be suitable to indicate the response to radiochemotherapy early. We analyzed the courses of nucleosomes, CEA, CA 19-9 and CYFRA 21-1 in 25 colorectal cancer patients during radiochemotherapy (4 postoperative, 13 preoperative, 8 local relapse therapy). Blood was taken before therapy, daily during the first week, once weekly during the following weeks, and at the end of the radiochemotherapy. After a temporary decline 6 h after the first irradiation, nucleosomes rose in most patients rapidly reaching a maximum during the first days which was followed by a subsequent decrease. In patients receiving postoperative therapy after complete resection of tumor, nucleosome levels generally were lower than in patients with preoperative or relapse therapy. Correspondingly, CEA, CA 19-9 and CYFRA 21-1 levels of postoperatively treated patients were the lowest whereas those with tumor relapse had the highest ones. During preoperative therapy, lower nucleosome concentrations were found in patients with response to therapy resulting in a smaller area under the curve of days 1-3 (AUC) than in those with progressive disease (p = 0.028). The other parameters did not indicate the response to therapy at the initial treatment phase. In conclusion, the course of nucleosomes (AUC) might be valuable for the early prediction of therapy response in preoperatively treated colorectal cancer patients.

Nucleosomes in pancreatic cancer patients during radiochemotherapy

Nucleosomes appear spontaneously in elevated concentrations in the serum of patients with malignant diseases as well as during chemo- and radiotherapy. We analyzed whether their kinetics show typical characteristics during radiochemotherapy and enable an early estimation of therapy efficacy. We used the Cell Death Detection Elisa plus (Roche Diagnostics) and investigated the course of nucleosomes in the serum of 32 patients with a local stage of pancreatic cancer who were treated with radiochemotherapy for several weeks. Ten of them received postsurgical therapy, 21 received primary therapy and 1 received therapy for local relapse. Blood was taken before the beginning of therapy, daily during the first week, once weekly during the following weeks and at the end of radiochemotherapy. The response to therapy was defined according to the kinetics of CA 19-9: a decrease of CA 19-9 > or =50% after radiochemotherapy was considered as 'remission'; an increase of > or =100% (which was confirmed by two following values) was defined as 'progression'. Patients with 'stable disease' ranged intermediately. Most of the examined patients showed a decrease of the concentration of nucleosomes within 6 h after the first dose of radiation. Afterwards, nucleosome levels increased rapidly, reaching their maximum during the following days. Patients receiving postsurgery, primary or relapse therapies did not show significant differences in nucleosome values during the time of treatment. Single nucleosome values, measured at 6, 24 and 48 h after the application of therapy, could not discriminate significantly between patients with no progression and those with progression of disease. However, the area under the curve of the first 3 days, which integrated all variables of the initial therapeutic phase, showed a significant correlation with the progression-free interval (p=0.008). Our results indicate that the area under the curve of nucleosomes during the initial phase of radiochemotherapy could be valuable for the early prediction of the progression-free interval.