Search Results (87)

C1QBP (Complement Component 1 Q Subcomponent-Binding Protein) plays a critical role in maintaining cellular metabolism, but its function in radiation-induced damage remains unclear. In this study, we generated C1QBP-deficient Huh-7 hepatocellular carcinoma (HCC) cells using CRISPR/Cas9 technology and observed that C1QBP deficiency significantly enhanced radiation-induced damage, as indicated by reduced cell proliferation, impaired colony formation, and increased γ-H2AX foci, a marker of DNA double-strand breaks. Additionally, C1QBP deficiency resulted in elevated phosphorylation of key DNA damage response (DDR) molecules, ATM and CHK2, and caused pronounced S phase cell cycle arrest. Mechanistic investigations revealed that C1QBP modulates NF-κB nuclear activity via the AMPK signaling pathway. The loss of C1QBP reduced NF-κB nuclear translocation, further exacerbating radiation-induced damage. Reintroducing C1QBP alleviated DNA damage, enhanced cell proliferation, and improved survival following radiation exposure. These findings highlight the critical role of C1QBP in modulating HCC cells radiosensitivity and underscore its potential as a therapeutic target to enhance radiotherapy outcomes. Full article

Platinum-based radiochemotherapy is associated with hematologic side effects, impacting patient outcomes. However, the clinical mechanisms of cisplatin and its interaction with ionizing radiation (IR), including in biodosimetry for radiotherapy, have not yet been fully clarified. For this purpose, healthy donors’ peripheral blood lymphocytes (PBLs) were pretreated with cisplatin in a pulse (1–4 h) or continuous (24 h) regimen followed by X-rays. DNA damage was assessed as DNA double-strand breaks using repair foci of γH2AX and 53BP1 after 0.5 h and 24 h in G1 PBLs and a proliferation-based cytokinesis-block micronucleus assay. Additionally, cell death and proliferation activity were measured. Unlike a 1 h pulse, a 24 h cisplatin pretreatment caused a concentration-dependent increase in cisplatin-induced foci while decreasing IR-induced foci, especially 24 h after irradiation. This was accompanied by increased apoptosis, with cisplatin and IR having additive effects. Both genotoxins alone caused a dose-dependent increase in micronuclei, while cisplatin significantly reduced binuclear cells, especially after the 24 h treatment, leading to lower micronuclei frequencies post-irradiation. Our results show that prolonged cisplatin exposure, even at low concentrations, impacts the vitality and division activity of PBLs, with significantly stronger effects post-irradiation. This has major implications and must be considered for the detection of DNA damage-associated biomarkers in PBLs used in clinical prediction or biodosimetry during radiotherapy. Full article

Global disparities in cancer prevention, detection, and treatment demand a unified international effort to reduce the disease’s burden and improve outcomes. Despite advances in chemotherapy and radiotherapy, many tumors remain resistant to these treatments. Gold nanoparticles (AuNPs) have shown promise as radiosensitizers, enhancing the effectiveness of low-energy X-rays by emitting Auger electrons that cause localized cellular damage. In this study, spherical AuNPs of 5 nm and 10 nm were characterized and tested on various cell lines, including malignant breast cells (MCF-7), non-malignant cells (CHO-K1 and MCF-10A), and human lymphocytes. Cells were treated with AuNPs and irradiated with attenuated 6 megavoltage (MV) X-rays or p(66)/Be neutron radiation to assess DNA double-strand break (DSB) damage, cell viability, and cell cycle progression. The combination of AuNPs and neutron radiation induced higher levels of γ-H2AX foci and micronucleus formation compared to treatments with AuNPs or X-ray radiation alone. AuNPs alone reduced cellular kinetics and increased the accumulation of cells in the G2/M phase, suggesting a block of cell cycle progression. For cell proliferation, significant effects were only observed at the concentration of 50 μg/mL of AuNPs, while lower concentrations had no inhibitory effect. Further research is needed to quantify internalized AuNPs and correlate their concentration with the observed cellular effects to unravel the biological mechanisms of their radioenhancement. Full article

Survivin is known for its dual biological role in apoptosis inhibition and mitotic progression. In addition to its being part of the chromosomal passenger complex (CPC), recent findings suggest additional roles for Survivin in the DNA damage response, further contributing to therapy resistance. In this study, we investigated the role of Survivin and the CPC proteins in the cellular response to irradiation with a focus on DNA replication processes. As is known, ionizing radiation leads to an increased expression of Survivin and its accumulation in nuclear foci, which we now know to be specifically localized to centromeric heterochromatin. The depletion of Survivin and Aurora B increases the DNA damage marker γH2AX, indicative of an impaired repair capacity. The presence of Survivin and the CPC in nuclear foci that we already identified during the S phase co-localize with the proliferating cell nuclear antigen (PCNA), further implying a potential role during replication. Indeed, Survivin knockdown reduced replication fork speed as assessed via DNA fiber assays. Mechanistically, we identified a PIP-box motif in INCENP mediating the interaction with PCNA to assist in managing damage-induced replication stress. Survivin depletion forces cells to undergo unphysiological genome replication via mitotic DNA synthesis (MiDAS), resulting in chromosome breaks. Finally, we revealed that Aurora B kinase liberates Pol η by phosphorylating polymerase delta-interacting protein 2 (POLDIP2) to resume the replication of damaged sites via translesion synthesis. In this study, we assigned a direct function to the CPC in the transition from stalled replication forks to translesion synthesis, further emphasizing the ubiquitous overexpression of Survivin particularly in tumors. This study, for the first time, assigns a direct function to the chromosomal passenger complex, CPC, including Survivin, Aurora B kinase, Borealin, and INCENP, in the transition from stalled replication forks (involving PCNA binding) to translesion synthesis (liberating Pol η by phosphorylating POLDIP2), and thus in maintaining genomic integrity. Full article

Our previous study demonstrated that the acute high-dose-rate (3.3 Gy/min) γ-ray irradiation (γ-irradiation) of postnatal day-3 (P3) mice with 5 Gy induced depression and drastic neuropathological changes in the dentate gyrus of the hippocampus of adult mice. The present study investigated the effects of chronic low-dose-rate (1.2 mGy/h) γ-irradiation from P3 to P180 with a cumulative dose of 5 Gy on animal behaviour, hippocampal cellular change, and miRNA and mRNA expression in the hippocampus and blood in female mice. The radiation exposure did not significantly affect the animal’s body weight, and neuropsychiatric changes such as anxiety and depression were examined by neurobehavioural tests, including open field, light-dark box, elevated plus maze, tail suspension, and forced swim tests. Immunohistochemical staining did not detect any obvious loss of mature and immature neurons (NeuN and DCX) or any inflammatory glial response (IBA1, GFAP, and PDGFRα). Nevertheless, γH2AX foci in the stratum granulosum of the dentate gyrus were significantly increased, suggesting the chronic low-dose-rate irradiation induced persistent DNA damage foci in mice. miRNA sequencing and qRT-PCR indicated an increased expression of miR-448-3p and miR-361-5p but decreased expression of miR-193a-3p in the mouse hippocampus. Meanwhile, mRNA sequencing and qRT-PCR showed the changed expression of some genes, including Fli1, Hs3st5, and Eif4ebp2. Database searching by miRDB and TargetScan predicted that Fli1 and Hs3st5 are the targets of miR-448-3p, and Eif4ebp2 is the target of miR-361-5p. miRNA/mRNA sequencing and qRT-PCR results in blood showed the increased expression of miR-6967-3p and the decreased expression of its target S1pr5. The interactions of these miRNAs and mRNAs may be related to the chronic low-dose-rate radiation-induced persistent DNA damage. Full article

Lung cancer continues to have one of the highest morbidity and mortality rates of any cancer. Although radiochemotherapy, in combination with immunotherapy, has significantly improved overall survival, new treatment options are urgently needed. However, preclinical radiotherapy testing is often performed in animal models, which has several drawbacks, including species-specific differences and ethical concerns. To replace animal models, this study used a micro-extrusion bioprinting approach to generate a three-dimensional (3D) human lung cancer model consisting of lung tumor cells embedded in human primary lung fibroblasts for radiotherapy research. The models were placed in a mouse phantom, i.e., a 3D-printed mouse model made of materials that mimic the X-ray radiation attenuation rates found in mice. In radiotherapy experiments, the model demonstrated a selective cytotoxic effect of X-rays on tumor cells, consistent with findings in 2D cells. Furthermore, the analysis of metabolic activity, cell death, apoptosis, and DNA damage-induced γH2AX foci formation revealed different results in the 3D model inside the phantom compared to those observed in irradiated models without phantom and 2D cells. The proposed setup of the bioprinted 3D lung model inside the mouse phantom provides a physiologically relevant model system to study radiation effects. Full article

The combination of high and low LET radionuclides has been tested in several patient studies to improve treatment response. Radionuclide mixtures can also be released in nuclear power plant accidents or nuclear bomb deployment. This study investigated the DNA damage response and DNA double-strand break (DSB) repair in peripheral blood mononuclear cells (PBMCs) after internal exposure of blood samples of 10 healthy volunteers to either no radiation (baseline) or different radionuclide mixtures of the α- and β-emitters [²²³Ra]RaCl₂ and [¹⁷⁷Lu]LuCl₃, i.e., 25 mGy/75 mGy, 50 mGy/50 mGy and 75 mGy/25 mGy, respectively. DSB foci and γ-H2AX α-track enumeration directly after 1 h of exposure or after 4 h or 24 h of repair revealed that radiation-induced foci (RIF) and α-track induction in 100 cells was similar for mixed α/β and pure internal α- or β-irradiation, as were the repair rates for all radiation qualities. In contrast, the fraction of unrepaired RIF (Q_β) in PBMCs after mixed α/β-irradiation (50% ²²³Ra & 50% ¹⁷⁷Lu: Q_β = 0.23 ± 0.10) was significantly elevated relative to pure β-irradiation (50 mGy: Q_{β, pure} = 0.06 ± 0.02), with a similar trend being noted for all mixtures. This α-dose-dependent increase in persistent foci likely relates to the formation of complex DNA damage that remains difficult to repair. Full article

Background: Cellular senescence in response to ionizing radiation (IR) limits the replication of damaged cells by causing permanent cell cycle arrest. However, IR can induce pro-survival signaling pathways that reduce the extent of radiation-induced cytotoxicity and promote the development of radioresistance. The differential incorporation of histone variant H2A.J has profound effects on higher-order chromatin organization and on establishing the epigenetic state of radiation-induced senescence. However, the precise epigenetic mechanism and function of H2A.J overexpression in response to IR exposure still needs to be elucidated. Methods: Primary (no target, NT) and genetically modified fibroblasts overexpressing H2A.J (H2A.J-OE) were exposed to 20 Gy and analyzed 2 weeks post-IR for radiation-induced senescence by immunohistochemistry and immunofluorescence microscopy. Transcriptome signatures were analyzed in (non-)irradiated NT and H2A.J-OE fibroblasts by RNA sequencing. Since H2A.J plays an important role in the epidermal homeostasis of human skin, the oncogenic potential of H2A.J was investigated in cutaneous squamous cell carcinoma (cSCC). The tissue microarrays of cSCC were analyzed for H2A.J protein expression pattern by automated image analysis. Results: In response to radiation-induced DNA damage, the overexpression of H2A.J impairs the formation of senescence-associated heterochromatin foci (SAHF), thereby inhibiting the SAHF-mediated silencing of proliferation-promoting genes. The dysregulated activation of cyclins and cyclin-dependent kinases disturbs cell cycle arrest in irradiated H2A.J-OE fibroblasts, thereby overcoming radiation-induced senescence. Comparative transcriptome analysis revealed significantly increased WNT16 signaling in H2A.J OE fibroblasts after IR exposure, promoting the fundamental mechanisms of tumor development and progression, including the activation of the epithelial–mesenchymal transition. The quantitative analysis of cSCCs revealed that undifferentiated tumors are associated with high nuclear H2A.J expression, related with greater oncogenic potential. Conclusion: H2A.J overexpression induces radioresistance and promotes oncogenic transformation through the activation of WNT16 signaling pathway functions. H2A.J-associated signatures may improve risk stratification by identifying patients with more aggressive cSCC who may require radiotherapy with increased doses. Full article

Recurrent computed tomography (CT) examination has become a common diagnostic procedure for several diseases and injuries. Though each singular CT scan exposes individuals at low doses of low linear energy transfer (LET) radiation, the cumulative dose received from recurrent CT scans poses an increasing concern for potential health risks. Here, we evaluated the biological effects of recurrent CT scans on the DNA damage response (DDR) in human fibroblasts and retinal pigment epithelial cells maintained in culture for five months and subjected to four CT scans, one every four weeks. DDR kinetics and eventual accumulation of persistent-radiation-induced foci (P-RIF) were assessed by combined immunofluorescence for γH2AX and 53BP1, i.e., γH2AX/53BP1 foci. We found that CT scan repetitions significantly increased both the number and size of γH2AX/53BP1 foci. In particular, after the third CT scan, we observed the appearance of giant foci that might result from the overlapping of individual small foci and that do not associate with irreversible growth arrest, as shown by DNA replication in the foci-carrying cells. Whether these giant foci represent coalescence of unrepaired DNA damage as reported following single exposition to high doses of high LET radiation is still unclear. However, morphologically, these giant foci resemble the recently described compartmentalization of damaged DNA that should facilitate the repair of DNA double-strand breaks but also increase the risk of chromosomal translocations. Overall, these results indicate that for a correct evaluation of the damage following recurrent CT examinations, it is necessary to consider the size and composition of the foci in addition to their number. Full article

Immunofluorescence with antibodies against phosphorylated forms of H2AX (γH2AX) is revolutionizing our understanding of repair and signaling of DNA double-strand breaks (DSBs). Unfortunately, the pattern of γH2AX foci depends upon a number of parameters (nature of stress, number of foci, radiation dose, repair time, cell cycle phase, gene mutations, etc…) whose one of the common points is chromatin condensation/decondensation. Here, we endeavored to demonstrate how chromatin conformation affects γH2AX foci pattern and influences immunofluorescence signal. DSBs induced in non-transformed human fibroblasts were analyzed by γH2AX immunofluorescence with sodium butyrate treatment of chromatin applied after the irradiation that decondenses chromatin but does not induce DNA breaks. Our data showed that the pattern of γH2AX foci may drastically change with the experimental protocols in terms of size and brightness. Notably, some γH2AX minifoci resulting from the dispersion of the main signal due to chromatin decondensation may bias the quantification of the number of DSBs. We proposed a model called “Christmas light models” to tentatively explain this diversity of γH2AX foci pattern that may also be considered for any DNA damage marker that relocalizes as nuclear foci. Full article

This work reports on a model that describes patient-specific absorbed dose-dependent DNA damage response in peripheral blood mononuclear cells of thyroid cancer patients during radioiodine therapy and compares the results with the ex vivo DNA damage response in these patients. Blood samples of 18 patients (nine time points up to 168 h post-administration) were analyzed for radiation-induced γ-H2AX + 53BP1 DNA double-strand break foci (RIF). A linear one-compartment model described the absorbed dose-dependent time course of RIF (Parameters: c characterizes DSB damage induction; k₁ and k₂ are rate constants describing fast and slow repair). The rate constants were compared to ex vivo repair rates. A total of 14 patient datasets could be analyzed; c ranged from 0.012 to 0.109 mGy⁻¹, k₂ from 0 to 0.04 h⁻¹. On average, 96% of the damage is repaired quickly with k₁ (range: 0.19–3.03 h⁻¹). Two patient subgroups were distinguished by k₁-values (n = 6, k₁ > 1.1 h⁻¹; n = 8, k₁ < 0.6 h⁻¹). A weak correlation with patient age was observed. While induction of RIF was similar among ex vivo and in vivo, the respective repair rates failed to correlate. The lack of correlation between in vivo and ex vivo repair rates and the applicability of the model to other therapies will be addressed in further studies. Full article

Esophageal squamous cell carcinoma (ESCC) is a deadly consequence of radiation exposure to the esophagus. ESCC arises from esophageal epithelial cells that undergo malignant transformation and features a perturbed squamous cell differentiation program. Understanding the dose- and radiation quality-dependence of the esophageal epithelium response to radiation may provide insights into the ability of radiation to promote ESCC. We have explored factors that may play a role in esophageal epithelial radiosensitivity and their potential relationship to ESCC risk. We have utilized a murine three-dimensional (3D) organoid model that recapitulates the morphology and functions of the stratified squamous epithelium of the esophagus to study persistent dose- and radiation quality-dependent changes. Interestingly, although high-linear energy transfer (LET) Fe ion exposure induced a more intense and persistent alteration of squamous differentiation and 53BP1 DNA damage foci levels as compared to Cs, the MAPK/SAPK stress pathway signaling showed similar altered levels for most phospho-proteins with both radiation qualities. In addition, the lower dose of high-LET exposure also revealed nearly the same degree of morphological changes, even though only ~36% of the cells were predicted to be hit at the lower 0.1 Gy dose, suggesting that a bystander effect may be induced. Although p38 and ERK/MAPK revealed the highest levels following high-LET exposure, the findings reveal that even a low dose (0.1 Gy) of both radiation qualities can elicit a persistent stress signaling response that may critically impact the differentiation gradient of the esophageal epithelium, providing novel insights into the pathogenesis of radiation-induced esophageal injury and early stage esophageal carcinogenesis. Full article

DNA damage is induced by both endogenous and exogenous factors. Repair of DNA double-strand break (DSB), a serious damage that threatens genome stability, decreases with senescence. However, the molecular mechanisms underlying the decline in DNA repair capacity during senescence remain unclear. We performed immunofluorescence staining for phosphorylated histone H2AX (γ-H2AX) in normal human fetal lung fibroblasts and human skin fibroblasts of different ages after chronic irradiation (total dose, 1 Gy; dose rate, 1 Gy/day) to investigate the effect of cellular senescence and organismal aging on DSB repair. Accumulation of DSBs was observed with cellular senescence and organismal aging, probably caused by delayed DSB repair. Importantly, the formation of γ-H2AX foci, an early event in DSB repair, is delayed with cellular senescence and organismal aging. These results suggest that the delay in γ-H2AX focus formation might delay the overall DSB repair. Interestingly, immediate γ-H2AX foci formation was suppressed in cells with senescence-associated heterochromatin foci (SAHF). To investigate the relationship between the γ-H2AX focus formation and SAHF, we used LiCl to relax the SAHFs, followed by irradiation. We demonstrated that LiCl rescued the delayed γ-H2AX foci formation associated with cellular senescence. This indicates that SAHF interferes with γ-H2AX focus formation and inhibits DSB repair in radiation-induced DSB. Our results suggest that therapeutic targeting of SAHFs have potential to resolve DSB repair dysfunction associated with cellular senescence. Full article

In patients with esophageal cancer undergoing neoadjuvant chemoradiotherapy (nCRT), subsequent restaging with F-18-fluorodeoxyglucose (18F-FDG) positron emission tomography–computed tomography (PET-CT) can reveal the presence of interval metastases, such as liver metastases, in approximately 10% of cases. Nevertheless, it is not uncommon in clinical practice to observe focal FDG uptake in the liver that is not associated with liver metastases but rather with radiation-induced liver injury (RILI), which can result in the overstaging of the disease. Liver radiation damage is also a concern during distal esophageal cancer radiotherapy due to its proximity to the left liver lobe, typically included in the radiation field. Post-CRT, if FDG activity appears in the left or caudate liver lobes, a thorough investigation is needed to confirm or rule out distant metastases. The increased FDG uptake in liver lobes post-CRT often presents a diagnostic dilemma. Distinguishing between radiation-induced liver disease and metastasis is vital for appropriate patient management, necessitating a combination of imaging techniques and an understanding of the factors influencing the radiation response. Diagnosis involves identifying new foci of hepatic FDG avidity on PET/CT scans. Geographic regions of hypoattenuation on CT and well-demarcated regions with specific enhancement patterns on contrast-enhanced CT scans and MRI are characteristic of radiation-induced liver disease (RILD). Lack of mass effect on all three modalities (CT, MRI, PET) indicates RILD. Resolution of abnormalities on subsequent examinations also helps in diagnosing RILD. Moreover, it can also help to rule out occult metastases, thereby excluding those patients from further surgery who will not benefit from esophagectomy with curative intent. Full article

Ionizing radiation-induced damage in cancer and normal cells leads to apoptosis and cell death, through the intracellular oxidative stress, DNA damage and disorders of their metabolism. Irradiation doses that do not lead to the death of tumor cells can result in the emergence of radioresistant clones of these cells due to the rearrangement of metabolism and the emergence of new mutations, including those in the genes responsible for DNA repair. The search for the substances capable of modulating the functioning of the tumor cell repair system is an urgent task. Here we analyzed the effect of cerium(III) fluoride nanoparticles (CeF₃ NPs) on normal (human mesenchymal stem cells–hMSC) and cancer (MCF-7 line) human cells after X-ray radiation. CeF₃ NPs effectively prevent the formation of hydrogen peroxide and hydroxyl radicals in an irradiated aqueous solution, showing pronounced antioxidant properties. CeF₃ NPs are able to protect hMSC from radiation-induced proliferation arrest, increasing their viability and mitochondrial membrane potential, and, conversely, inducing the cell death of MCF-7 cancer cells, causing radiation-induced mitochondrial hyperpolarization. CeF₃ NPs provided a significant decrease in the number of double-strand breaks (DSBs) in hMSC, while in MCF-7 cells the number of γ-H2AX foci dramatically increased in the presence of CeF₃ 4 h after irradiation. In the presence of CeF₃ NPs, there was a tendency to modulate the expression of most analyzed genes associated with the development of intracellular oxidative stress, cell redox status and the DNA-repair system after X-ray irradiation. Cerium-containing nanoparticles are capable of providing selective protection of hMSC from radiation-induced injuries and are considered as a platform for the development of promising clinical radioprotectors. Full article