Laser-driven accelerated particle beams have revolutionized the field of cancer treatment by enabling the delivery of extremely high dose-rates of radiation to solid tumors in a matter of femto- to picoseconds. In this study, radiobiological effectiveness of ultrashort pulsed electron beams generated by Advanced Research Electron Accelerator Laboratory (AREAL) accelerator and conventional X-rays were compared on two non-small cell lung cancer (NSCLC) cell lines, A549 (wild-type p53) and H1299 (p53-deficient). NSCLC cells were irradiated at using a AREAL accelerator (a peak dose rate of 1.6 × 1010 Gy/s, pulse duration of 4.5 × 10–13 s, repetition rate of 20 Hz) or X-ray unit at an absorbed dose rate of 0.85 Gy/min. Clonogenic survival analysis, γH2AX foci enumeration and genome-wide transcriptome analysis were performed. Clonogenic survival curves showed increased ra-diosensitivity of A549 cells after AREAL exposure compared to X-rays (RBEs=1.2), while H1299 radiosensitivity has not changed. AREAL exposure caused higher linear dose–dependent increase in the number of residual γH2AX foci in both A549 and H1299 cells compared to X-rays. The DNA double-strand breaks in H1299 cells were mainly repaired through homologous recombination following AREAL exposure. However, the gene ex-pression analysis of pathway activation levels revealed a down-regulation of the same pathways in A549 cells. This resulted in activation of Integrin-linked kinase-dependent apoptosis, G2 and proliferation arrest of A549 cells.

Laser-driven accelerated particle beams have significantly advanced cancer treatment by facilitating the delivery of exceptionally high dose rates of radiation to solid tumors within femto- to picosecond timescales. This investigation compared the radiobiological effectiveness of ultrashort pulsed electron beams, generated by the Advanced Research Electron Accelerator Laboratory (AREAL) accelerator, with conventional X-rays on two non-small cell lung cancer (NSCLC) cell lines: A549 (wild-type p53) and H1299 (p53-deficient). NSCLC cells were irradiated using either the AREAL accelerator (with a peak dose rate of 1.6 × 1010 Gy/s, a pulse duration of 4.5 × 10-13 s, and a repetition rate of 20 Hz) or an X-ray unit at an absorbed dose rate of 0.85 Gy/min. Clonogenic survival analysis, γH2AX foci enumeration, and genome-wide transcriptome analysis were conducted. Clonogenic survival curves showed increased radiosensitivity of A549 cells following AREAL exposure compared to X-rays (RBE = 1.2), whereas H1299 radiosensitivity remained unchanged. In both cell lines, AREAL exposure resulted in a greater dose-dependent accumulation of residual γH2AX foci 24 h after irradiation than conventional X-rays, suggesting more persistent DNA damage signaling. Transcriptomic analyses revealed broader gene expression changes after AREAL irradiation and suggested distinct p53-related responses. Pathway-level analysis demonstrated that A549 cells exhibited reduced DNA repair activity, accompanied by dysregulation of cell cycle progression and apoptosis, whereas H1299 cells displayed transcriptomic signatures consistent with enhanced homologous recombination activity. Overall, these findings indicate that ultrashort pulsed electron beams induce p53-related responses distinct from those of conventional X-rays and warrant further investigation of this technology as a potential radiotherapy modality.

Purpose: 1) Synthesis and characterization of β-cyclodextrin stabilized silver and gold nanoparticles. 2) Evaluation of the effect of the synthesized nanoparticles on the severity of radiobiological effects in irradiated breast cancer (BC) cells. Material and methods: Gold and silver nanoparticles were synthesized using β-cyclodextrin as a reducing agent and stabilizer. Human BC cell lines MDA-MB-231 (ER-/PR-/ EGFR+/ HER2-) and MCF7 (ER+/ PR+/ EGFR-/ HER2-) were used in the work. The cells were irradiated on a RUB RUST-M1 (Russia) X-ray irradiation facility, equipped with two X-ray emitters, at a dose rate of 0.85 mGy/min, 200 kV voltage, 5.0 mA current, 1.5 mm Al filter. Nanoparticles were added 24 h before irradiation at a concentration of 0.5 mg/l. Cells without nanoparticles were used as a control. To assess radiobiological effects, foci of the DNA damage marker protein (γH2AX) were analyzed 1 and 24 hours after irradiation. Statistical and mathematical data analysis was performed using GraphPad Prism 9.0.2.161 software (GraphPad Software). Statistical significance was assessed using analysis of variance (ANOVA). Results: Effective radiosensitization of BC cell lines MDA-MB-231 and MCF7 using β-cyclodextrin stabilized gold and silver nanoparticles (AuNPs and AgNPs) was shown. The results obtained indicate the achievement of statistically significant results already at a concentration of 0.5 mg/l, which is at least 20 times less than the concentrations previously used to achieve a significant effect.

Purpose: Radiation therapy can treat non-small cell lung cancer (NSCLC), but its effectiveness is limited by the development of tumor radioresistance. Studies have shown that radiation can affect tumor aggressiveness, either reducing or increasing the invasiveness of remaining cancer cells, depending on the cell lines and radiation type. However, the effect of tumor cell migration in the confined porous space of tumor tissue on their phenotypic characteristics is not well understood. This study aimed to investigate how migration in confined spaces affects the phenotypic traits of two NSCLC isogenic cell lines with varying levels of radioresistance, invasiveness, and repopulation ability. Material and methods: The biophysical impact on the A549 cell line and its isogenic radioresistant subline A549IR was carried out by their sequential triple migration in a limited space of membrane pores with a diameter of 8 μm in Boyden chambers, following the concentration gradient of fetal bovine serum. The ability to repopulate cell populations migrated across membranes was characterized using clonogenic analysis. We assessed markers such as Ki67 (cell cycle activity), vimentin (a cytoskeletal protein linked to migration and metastasis), and fluorescent nanosensor uptake (indicating metastasis potential) through quantitative analysis of digital images from high-content imaging of individual cells. A standard method for determining cell mass with the dye sulphorodamine B after exposure to different concentrations of cisplatin was used to assess the chemosensitivity of tumor cells before and after migration. Results and Conclusion: The study shows that repeated migration through an 8 μm pore, which simulates conditions cancer cells experience during metastasis, deforms the nuclei of non-small cell lung cancer (NSCLC) cells. This deformation reduces Ki67-related chromatin reorganization and alters gene expression, notably increasing vimentin. This results in increased chemoresistance and a greater likelihood of repopulation and metastasis in these cells, regardless of their initial ability to migrate or their sensitivity to chemotherapy and radiation.

Radiotherapy is a crucial treatment option for various cancers. However, the results of radiotherapy can vary widely across different cancer types and even among patients with the same type of cancer. This variability presents a major challenge in optimizing treatment strategies and improving patient survival. Here, we collected radiotherapy phenotype and expression data from 32 TCGA cancer datasets and performed overall survival analysis for 32 cancer types. Additionally, we conducted a signaling pathway enrichment analysis to identify key pathways involved in radiotherapy resistance and sensitivity. Our findings show that radiotherapy improves survival outcomes in certain cancer types, such as glioblasoma multiforme (GBM), while worsening outcomes in others, such as low-grade glioma (LGG). Next, we focused on exploring the differences in radiotherapy outcomes between GBM and LGG, focusing on the molecular mechanisms contributing to these variations. We identify differential regulation of pathways related to programmed cell death, DNA repair, telomere maintenance, chromosome condensation, antiviral responses, and interferon signaling between GBM and LGG patients perhaps explaining radiotherapy efficacy. A genetic analysis confirmed the importance of immune response and radiotherapy outcome for LGG patients. These insights underscore the importance of personalized treatment approaches and the need for further research to improve radiotherapy outcomes in cancer patients.

Purpose: Lung cancer is the leading cause of death worldwide, with non-small cell lung cancer (NSCLC) accounting for 85 % of all lung cancers. Combined chemoradiotherapy is one of options in the treatment of patients with inoperable NSCLC. However, the prognosis of NSCLC remains unsatisfactory due to the development of radio- and chemo-resistance of cancer cells. This study aimed to investigate how the overexpression of miR-16, miR-16-1-3p, and miR-16-2-3p influences clonogenic survival, migration, and sensitivity to cisplatin in both radiosensitive and radioresistant non-small cell lung cancer (NSCLC) cells. Material and methods: This study involved the application of single proton beam irradiation to A549 NSCLC cells, resulting in the emergence of a subline of resilient radioresistant daughter cells, designated as A549IR. To explore the functional role of the miR-16, miR-16-1-3p, and miR-16-2-3p in NSCLC, we overexpressed the “leader” miR-16 as well as the “passenger” miR-16-1-3p and miR-16-2-3p strands in both the parental A549 and their radioresistant variant, A549IR cells. The impact of microRNA overexpression on cell viability was evaluated through a clonogenic assay. Additionally, cisplatin sensitivity was measured by calculating the total mass of surviving cells via the sulforhodamine B method. Furthermore, the capacity for cell migration and invasion was investigated using Boyden chambers. Results: Overexpressing miR-16, miR-16-1-3p, and miR-16-2-3p significantly reduced the ability of A549 and radioresistant A549IR NSCLC cells to survive, clone, migrate, and invade, compared to cells with normal levels of these microRNAs. Moreover, the stable overexpression of these microRNAs markedly enhanced the sensitivity of A549 and A549IR cells to the cytotoxic effects of cisplatin, allowing for a nearly threefold reduction in the concentration needed to achieve 50 % cell death. Conclusion: An increase in the expression of “passenger” miR-16-1-3p and miR-16-2-3p, as well as the “leader” miR-16, exhibits a robust tumor-suppressive and cisplatin-sensitizing activities in both the radiation-sensitive parental and the radiation-resistant daughter cells in the human NSCLC A549 lineage.

We compared the influence of X-rays generated at the peak anode voltages of 50, 100, and 200 kVp on the quantitative yield of foci (localized dynamic microclusters) of proteins involved in repair critical radiation-induced DNA damage, double-strand breaks (γH2AX and 53BP1), in cultured human mesenchymal stem stromal cells. Calculations of the relative biological effectiveness (RBE) based on the experimentally obtained dose curves of changes in the number of γH2AX and 53BP1 foci indicate that relative to the standard 200 kVp X-ray radiation taken as 1, the RBE of 100 kVp radiation is ~1.15, and that of 50 kVp is ~1.50. The obtained results indicate the necessity for thorough fundamental studies for evaluation of the real RBE of low-energy X-rays with subsequent correction of the weighting factor values.

BackgroundEnumeration of residual DNA repair foci 24 hours or more after exposure to ionizing radiation (IR) is often used to assess the efficiency of DNA double-strand break repair. However, the relationship between the number of residual foci in irradiated cells and the radiation dose is still poorly understood. The aim of this work was to investigate the dose responses for residual DNA repair foci in normal human fibroblasts after X-ray exposure in the absorbed dose range from 0.1 to 5 Gy.Materials and MethodsFibroblasts were irradiated using a X-ray unit at an absorbed dose rate of 0.2 Gy/min. Irradiated cells were incubated for 0.5, 24, 48 and 72 h. Immunofluorescence visualized gamma H2AX, 53BP1, pATM and p-p53 (Ser-15) foci were enumerated using DARFI software and by manual scoring. Additionally, clonogenic survival analysis was performed.ResultsThe data analysis performed with the hockey stick model showed the presence of a dose threshold for the residual foci of all proteins studied. The estimated threshold doses are close to the quasi-threshold dose (Dq = 0.99 +/- 0.09 Gy) calculated from the cell survival curve.ConclusionThe excellent agreement between the calculated values of the threshold dose and Dq in irradiated fibroblasts proves that residual foci are sites, where cells are still attempting to repair potentially lethal DNA damage.

An open question in radiobiology concerns whether low doses of radiation are harmful or if cells are able to tolerate such exposure with minimal or no disruption. This issue is relevant for evaluating public health risks associated with the increasing number of medical computed tomography (CT) diagnostic procedures. This study evaluated the impact of CT scan-level exposure on human adipose mesenchymal stem cells (hMSCs) by measuring DNA damage responses (γH2AX, 53BP1, pATM foci), proliferation (Ki-67), senescence (β-galactosidase), and multiple gene expressions. Responses to one or five CT exposures were compared to a 2 Gy X-ray dose at intervals from 1 h to 10 passages post-irradiation. It was shown that CT scan briefly increased DNA damage markers but showed no significant long-term effects. A high dose of 2 Gy X-ray exposure caused sustained DNA damage, decreased proliferation, increased senescence, and significant changes in hundreds of genes even after several cell generations. After a single CT exposure, gene expression changes were minimal, while high-dose exposure led to strong activation of DNA repair and stress response pathways. Five CT scans caused a slight activation of LIF and HSPA1B genes, but these effects were minor compared to the high-dose group. All detected effects from CT scans were not observed by ten cell passages, whereas high-dose effects persisted. In conclusion, typical CT scan exposures have only short-term, mild effects on hMSCs, while high-dose radiation causes lasting cellular and genetic changes.

The effects of low- and medium-dose X-rays on mitochondrial function in mesenchymal stem (stromal) cells (MSCs) were compared. Irradiation at a dose of 80 mGy did not lead to mitochondrial disorders in MSCs by all analyzed parameters, while 24 h after irradiation at a dose of 2000 mGy, damage to mitochondrial and nuclear DNA was recorded, as well as the initiation of replicative synthesis of mitochondrial DNA involving damaged molecules, which led to an increase in the level of heteroplasmy. The increased level of mitochondrial DNA heteroplasmy after irradiation at a dose of 2000 mGy was accompanied by a decrease in the expression of genes involved in the process of oxidative phosphorylation and regulating mitochondrial dynamics.

Purpose: To evaluate radioresistance of human non-small cell lung cancer (NSCLC) cells that survived and showed sustained growth after exposure to cisplatin. Material and methods: The work used the NSCLC cell line A549, which was exposed to cisplatin at a concentration of 2.5 μg/ml four times to obtain a cell population that survives and produces stable growth after exposure to cisplatin, A549Pt. Cell irradiation was carried out on a RUB RUST-M1 X-ray biological installation (Russia) at a dose rate of 0.85 Gy/min. Cell death was assessed using flow cytometry. To analyze the effectiveness of DNA repair from double-strand breaks (DSBs), we used a quantitative assessment of the foci of DNA DSB marker proteins γH2AX and 53BP1. Results: A549Pt NSCLC cells that survived and grew robustly after exposure to cisplatin exhibited reduced activation of apoptosis and produced less 53BP1 in response to additional cisplatin exposure compared to parental A549 cells. A549Pt also exhibit resistance to X-ray radiation, manifested in a decrease in the quantitative yield of foci of DNA DSB marker proteins γH2AX and 53BP1. The resistance of A549Pt cells to the effects of ionizing radiation, revealed in this work, can significantly reduce the effectiveness of neoadjuvant chemoradiation therapy for malignant neoplasms. Further research is needed to identify the detailed cellular and molecular mechanisms of the resistance of surviving cells to radiation therapy acquired during chemotherapy. In the future, this will increase the effectiveness of treatment of malignant neoplasms and avoid relapses.

Radiotherapy (RT) has been shown to be a cornerstone of both palliative and curative tumor care. RT has generally been reported to be sharply limited by ionizing radiation (IR)-induced toxicity, thereby constraining the control effect of RT on tumor growth. FLASH-RT is the delivery of ultra-high dose rate (UHDR) several orders of magnitude higher than what is presently used in conventional RT (CONV-RT). The FLASH-RT clinical trials have been designed to examine the UHDR deliverability, the effectiveness of tumor control, the dose tolerance of normal tissue, and the reproducibility of treatment effects across several institutions. Although it is still in its infancy, FLASH-RT has been shown to have potential to rival current RT in terms of safety. Several studies have suggested that the adoption of FLASH-RT is very limited, and the incorporation of this new technique into routine clinical RT will require the use of accurate dosimetry methods and reproducible equipment that enable the reliable and robust measurements of doses and dose rates. The purpose of this review is to highlight the advantages of this technology, the potential mechanisms underpinning the FLASH-RT effect, and the major challenges that need to be tackled in the clinical transfer of FLASH-RT.

The effects of low-dose radiation exposure remain a controversial topic in radiation biology. This study compares early (0.5, 4, 24, 48, and 72 h) and late (5, 10, and 15 cell passages) post-irradiation changes in γH2AX, 53BP1, pATM, and p-p53 (Ser-15) foci, proliferation, autophagy, and senescence in primary fibroblasts exposed to 100 and 2000 mGy X-ray radiation. The results show that exposure to 100 mGy significantly increased γH2AX, 53BP1, and pATM foci only at 0.5 and 4 h post irradiation. There were no changes in p-p53 (Ser-15) foci, proliferation, autophagy, or senescence up to 15 passages post irradiation at the low dose.

Purpose: To analyze the relationship between cellular aging and changes in the number and size of phosphorylated histone H2AX (γH2AX) foci in human fibroblasts and their descendants (up to 15 passages) after exposure to low and high doses of X-ray radiation. Material and methods: The work was performed on a culture of human skin fibroblasts. Cells were irradiated in the exponential growth phase on an X-ray biological unit RUB RUST-M1 (Russia), equipped with two X-ray emitters, at a dose rate of 40 mGy/min (dose 100 mGy) or 850 mGy/min (doses 2000 and 5000 mGy) and temperature 4˚C. Immunocytochemical staining was used to assess the number and size of γH2AX foci and the proportion of proliferating cells using antibodies to γH2AX and Ki67 (a cell proliferation marker protein), respectively. To assess cellular senescence, the proportion of cells positive for senescence-associated β-galactosidase (CA-β-gal(+)) was analyzed. Statistical and mathematical analysis of the obtained data was carried out using the statistical software package Statistica 8.0 (StatSoft). Results: The studies showed that irradiation of cultured human fibroblasts at a low dose (100 mGy) does not lead to statistically significant changes in the number and size of γH2AX foci, as well as the proportion of non-proliferating and senescent cells in the progenies of irradiated cells up to the 15th passage after irradiation. The phenomenon of aging-associated persistence of an increased number and size of γH2AX foci in passages of cells irradiated at a dose of 5000 mGy was discovered. Mathematical analysis of the relationship between changes in the proportion of CA-β-gal(+) cells, the number and size of γH2AX foci in populations of irradiated cells indicates that radiation-induced cellular aging is more associated with the size, rather than the number, of γH2AX foci.

Aim: To study the patterns of changes in the number of foci of phosphorylated DNA double-strand break repair proteins H2AX (γH2AX) and ATM (pATM) in cultured human mesenchymal stem cells (MSCs) 1‒48 hours after exposure to X-ray radiation at doses of 40, 80, 160 and 250 mGy. Material and methods: We used the primary culture of human MSCs, obtained from the collection of LLC “BioloT” (Russia). Cells were irradiated using a RUB RUST-M1 X-ray biological unit (Diagnostika-M LLC, Moscow, Russia) equipped with two X-ray emitters at a dose rate of 40 mGy/min (voltage of 100 kV, an anode current of 8 mA, and a 1.5 mm Al filter) and 4 °C temperature. To quantify the yield of γH2AX and pATM foci immunocytochemical staining was carried out with the use of γH2AX and pATM antibody respectively. Statistical analysis of the obtained data was carried out using the statistical software package Statistica 8.0 (StatSoft). To assess the significance of differences between samples, Student’s t-test was used. Results: It was shown that the kinetics of changes in the number of γH2AX foci after irradiation at doses of 160 and 250 mGy and low (40‒80 mGy) doses are significantly different. In contrast to the significant (50‒60 %) decrease in the number of γH2AX foci observed 6 hours after irradiation at doses of 160 and 250 mGy, after irradiation at low doses, no significant decrease in γH2AX foci was observed at this time point. Analysis of the colocalization of γH2AX foci with pATM foci indicates that the mechanisms for maintaining a high number of γH2AX foci 24‒48 hours after low-dose irradiation are ATM independent. A hypothesis has been put forward to explain the phenomenon of maintaining the number of γH2AX foci 24‒48 hours after irradiation in low doses by replicative stress caused by stimulation of proliferation against the background of hyperproduction of free radicals, resulting in additional formation of DNA double-strand breaks and phosphorylation of H2AX by ATR kinase.

Radioresistance is a major obstacle for the successful therapy of many cancers, including non-small cell lung cancer (NSCLC). To elucidate the mechanism of radioresistance of NSCLC cells and to identify key molecules conferring radioresistance, the radioresistant subclones of p53 wild-type A549 and p53-deficient H1299 cell cultures were established. The transcriptional changes between parental and radioresistant NSCLC cells were investigated by RNA-seq. In total, expression levels of 36,596 genes were measured. Changes in the activation of intracellular molecular pathways of cells surviving irradiation relative to parental cells were quantified using the Oncobox bioinformatics platform. Following 30 rounds of 2 Gy irradiation, a total of 322 genes were differentially expressed between p53 wild-type radioresistant A549IR and parental A549 cells. For the p53-deficient (H1299) NSCLC cells, the parental and irradiated populations differed in the expression of 1628 genes and 1616 pathways. The expression of genes associated with radioresistance reflects the complex biological processes involved in clinical cancer cell eradication and might serve as a potential biomarker and therapeutic target for NSCLC treatment.

Purpose: To evaluate the frequency and spectrum of chromosome aberrations under X-Ray exposure at doses of 80, 250, and 1000 mGy in a human multipotent mesenchymal stromal cell (MMSC) cell line during long-term cultivation. Material and methods: MMSCs were isolated from human gingival mucosa by an enzymatic method and cultured in a serum-free medium. The presence of surface antigens was determined using the method of flow cytometry. The ability of the cell line to differentiate in the osteogenic, adipogenic, and chondrogenic directions was studied using induction media. Authentication was performed by genotyping of polymorphic STR loci, cytogenetic analysis was performed by multicolor fluorescent in situ hybridization (mFISH). Irradiation was carried out on an X-ray biological unit RUB RUST-M1 (Russia) at a dose rate of 40 mGy/min, a voltage of 100 kV, and a current of 0.8 mA. Results: At the first passage after irradiation, a statistically significant increase in the frequency of non-clonal CA compared with the control was recorded at a dose of 80, but not 250 and 1000 mGy. At the late stages of cultivation, the average frequency of breaks per chromosome in the group of non-irradiated cells did not differ from the values obtained after irradiation at doses of 80, 250, and 1000 mGy (p > 0.05). However, in MMSCs irradiated at a dose of 80 mGy, damage occurred more often in pairs of chromosomes 6 and 10, and at a dose of 1000 mGy, in a pair of chromosomes 9. A single irradiation of MMSCs in vitro did not affect the growth and progression of MMSCs characteristic of the studied primary cell line, of clonal cells with chromosome translocations and monosomy X, but led to an increase in the representation of a clone with tetrasomy 8. The total number of random clones with chromosome translocations that arose de novo increased after irradiation at a dose of 1000 mGy. Conclusion: Minor fluctuations in the proportion of cells with non-clonal CA, depending on the dose received in the early stages after irradiation (passage 1–4), disappeared at the later stages of cultivation (passage 8–14). There were no differences in mean frequencies between irradiated and non-irradiated MMSCs, but after irradiation, damage to some chromosomes could occur more frequently than others. A single X-ray irradiation of MMSCs can promote the growth and progression of primary pathological cytogenetic clones, regardless of the dose received, as well as an increase in the total number of de novo cell clones with chromosomal translocations that have arisen. A single X-ray irradiation of MMSCs can promote the growth and progression of primary pathological cytogenetic clones, regardless of the dose received, as well as an increase in the total number of de novo cell clones with chromosomal translocations that have arisen.

Resistance to chemo- or radiotherapy is the main obstacle to consistent treatment outcomes in oncology patients. A deeper understanding of the mechanisms driving the development of resistance is required. This review focuses on secretory factors derived from chemo- and radioresistant cancer cells, cancer-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), and cancer stem cells (CSCs) that mediate the development of resistance in unexposed cells. The first line of evidence considers the experiments with conditioned media (CM) from chemo- and radioresistant cells, CAFs, MSCs, and CSCs that elevate resistance upon the ionizing radiation or anti-cancer drug exposure of previously untreated cells. The composition of CM revealed factors such as circular RNAs; interleukins; plasminogen activator inhibitor; and oncosome-shuttled lncRNAs, mRNAs, and miRNAs that aid in cellular communication and transmit signals inducing the chemo- and radioresistance of sensitive cancer cells. Data, demonstrating that radioresistant cancer cells become resistant to anti-neoplastic drug exposure and vice versa, are also discussed. The mechanisms driving the development of cross-resistance between chemotherapy and radiotherapy are highlighted. The secretion of resistance-mediating factors to intercellular fluid and blood brings attention to its diagnostic potential. Highly stable serum miRNA candidates were proposed by several studies as prognostic markers of radioresistance; however, clinical studies are needed to validate their utility. The ability to predict a treatment response with the help of the miRNA resistance status database will help with the selection of an effective therapeutic strategy. The possibility of miRNA-based therapy is currently being investigated with ongoing clinical studies, and such approaches can be used to alleviate resistance in oncology patients.

Purpose: Comparative study of changes in the number of foci of DNA (DSB) marker proteins (γH2AX and 53BP1) in human mesenchymal stromal cells (MSCs) incubated with 3H-thymidine or HTO for 24, 48, and 72 h. Material and methods: We used the primary culture of human MSCs of passage 5–6, obtained from the collection of LLC “BioloT” (Russia). A sterile solution of 3H-thymidine or HTO with a specific activity of 100 to 400 MBq/l was added to the nutrient medium and incubated under standard conditions of a CO2 incubator for 24, 48, and 72 hours. To quantify γH2AX foci and the proportion of proliferating cells using antibodies to γH2AX, 53BP1 and Ki67 (a marker protein for cell proliferation), were used, respectively. Statistical analysis of the obtained data was carried out using the statistical software package Statistica 8.0 (StatSoft). To assess the significance of differences between samples, Student’s t-test was used. Results: Incubation of MSCs with 3H-thymidine with a specific radioactivity of 100-400 MBq/l in the first 24 hours leads to a dose-dependent increase in the number of γH2AX and 53BP1 foci. With a further increase in the incubation time to 48 h and 72 h, a saturation effect is observed ‒ the number of foci reaches a plateau. A statistically significant increase in the number of γH2AX and 53BP1 foci in MSCs incubated with HTO was observed only in actively proliferating cells during the first 24 h of incubation in a medium with specific radioactivity of 300 and 400 MBq/l, after which, with a decrease in proliferative activity, it decreased to control values. Calculations made on the basis of the results of a quantitative analysis of γH2AX and 53BP1 foci after 24 h of incubation of MSCs with tritium compounds obtained in the course of the work show, that under the influence of 3H-thymidine ~ 6 times more DNA double-strand breaks are induced than under the influence of HTO.

CONTENTS Introduction Factors and mechanisms of Stress-Associated Secretory Phenotype (SASP) Morphological and transcriptional signatures of SASP Radiation-induced signaling pathways associated with premature senescence Conclusion