Irradiated Blood Lymphocytes Research Articles

Can SARS-CoV-2 change individual radiation sensitivity of the patients recovered from COVID-19? (experimental and theoretical background).

R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology of the National Academy of Science of Ukraine has been studying the mechanisms and specificities of individual radiation sensitivity (IRS) formation in professionals who work in the field of ionizing radiation, cancer patients and representatives of other population groups. Our data based on the use of G2-test in in vitro irradiated blood lymphocytes in late G2-period of cell cycle indicated an increased carcinogenic risk in professionals with high IRS. We suggest that the COVID-19pandemic could make significant adjustments in the formation of IRS in professionals who have survived the disease and continue to work with ionizing radiation (IR). Increased systemic inflammatory activity, which persists for a long time in COVID-19patients, in combination with low-dose range irradiation (professionals who continue to work with IR) and with local irradiation in the high-dose range (radiation therapy for cancer patients) may affect IRS. Repeated determination of IRS in professionals who have had COVID-19infection, using chromosomal G2-radiation sensitivity assay will answer the question: can SARS-CoV-2coronavirus affect the IRS? The proposed hypothesis of the radiosensitivity evolution needs further experimental validation using a set of radiobiological indices to clarify the mechanism of IRS formation following COVID-19infection. The detected changes (increase) of human IRS after COVID-19must be taken into account for personalized planning of radiotherapy of COVID-19cancer patients.

Towards Establishing Capacity for Biological Dosimetry at Ghana Atomic Energy Commission.

The aim of this study was not only to obtain basic technical prerequisites for the establishment of capacity of biological dosimetry at the Ghana Atomic Energy Commission (GAEC) but also to stimulate interest in biological dosimetry research in Ghana and Sub-Saharan Africa. Peripheral blood from four healthy donors was exposed to different doses (0–6 Gy) of gamma rays from a radiotherapy machine and lymphocytes were subsequently stimulated, cultured, and processed according to standard protocols for 48–50 h. Processed cells were analyzed for the frequencies of dicentric and centric ring chromosomes. Radiation dose delivered to the experimental model was verified using GafChromic® EBT films in parallel experiments. Basic technical prerequisites for the establishment of capacity of biological dosimetry in the GAEC have been realized and expertise in the dicentric chromosome assay consolidated. We successfully obtained preliminary cytogenetic data for a dose-response relationship of the irradiated blood lymphocytes. The data strongly indicate the existence of significant linear (α) and quadratic (β) components and are consistent with those published for the production of chromosome aberrations in comparable absorbed dose ranges.

DNA-Damage Foci to Detect and Characterize DNA Repair Alterations in Children Treated for Pediatric Malignancies

PurposeIn children diagnosed with cancer, we evaluated the DNA damage foci approach to identify patients with double-strand break (DSB) repair deficiencies, who may overreact to DNA-damaging radio- and chemotherapy. In one patient with Fanconi anemia (FA) suffering relapsing squamous cell carcinomas of the oral cavity we also characterized the repair defect in biopsies of skin, mucosa and tumor.Methods and MaterialsIn children with histologically confirmed tumors or leukemias and healthy control-children DSB repair was investigated by counting γH2AX-, 53BP1- and pATM-foci in blood lymphocytes at defined time points after ex-vivo irradiation. This DSB repair capacity was correlated with treatment-related normal-tissue responses. For the FA patient the defective repair was also characterized in tissue biopsies by analyzing DNA damage response proteins by light and electron microscopy.ResultsBetween tumor-children and healthy control-children we observed significant differences in mean DSB repair capacity, suggesting that childhood cancer is based on genetic alterations affecting DNA repair. Only 1 out of 4 patients with grade-4 normal-tissue toxicities revealed an impaired DSB repair capacity. The defective DNA repair in FA patient was verified in irradiated blood lymphocytes as well as in non-irradiated mucosa and skin biopsies leading to an excessive accumulation of heterochromatin-associated DSBs in rapidly cycling cells.ConclusionsAnalyzing human tissues we show that DSB repair alterations predispose to cancer formation at younger ages and affect the susceptibility to normal-tissue toxicities. DNA damage foci analysis of blood and tissue samples allows one to detect and characterize DSB repair deficiencies and enables identification of patients at risk for high-grade toxicities. However, not all treatment-associated normal-tissue toxicities can be explained by DSB repair deficiencies.

DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy

This study aimed to test whether induction of apoptosis following ex vivo X-irradiation of unstimulated blood lymphocytes correlated with clinical radiosensitivity and DNA double-strand break (DSB) repair in breast radiotherapy patients and healthy volunteers. Using small molecule inhibitors, the relationship between DSB repair and radiation-induced apoptosis was examined. Sixteen breast cancer patients with minimal (controls, n = 8) or extremely marked late radiation-induced change (cases, n = 8) and eight healthy volunteers were selected. DSBs were quantified by γH2AX/53BP1 immunofluorescence, and apoptosis was measured using a fluorogenic inhibitor of caspases assay. Mean γH2AX/53BP1 focus levels 24 h after exposure to 4 Gy were higher in cases (12.7 foci per cell) than in controls (10.3 foci per cell, p = 0.002). In contrast, the mean apoptotic fraction 48 h after 8 Gy was comparable, 37.2 % in cases and 34.7 % in controls (p = 0.442). Residual focus and apoptosis levels were not correlated within individuals (Spearman's R = -0.0059, p = 0.785). However, cells treated with DNA-PK inhibitor Nu7441 had higher focus and apoptosis levels 48 h after 1 Gy compared to mock-treated cells, suggesting that apoptosis induction following irradiation is modulated by DSB repair. This effect required functional ATM since cells treated simultaneously with Nu7441 and the ATM inhibitor Ku55933 were resistant to apoptosis despite high levels of residual foci. One clinical case displayed an impaired DNA-PK-dependent end-joining cellular phenotype. In summary, clinical radiosensitivity may be associated with impaired DSB repair in some patients. Although pharmaceutical inhibition of ATM and DNA-PK affected apoptosis induction and DSB repair, no association was observed between apoptosis and residual focus levels in patients and volunteers.

Residual DNA and chromosomal damage in ex vivo irradiated blood lymphocytes correlated with late normal tissue response to breast radiotherapy

PurposeTo test the association of DNA double-strand break (DSB) repair and chromosomal radiosensitivity in ex vivo irradiated blood lymphocytes with late-onset normal tissue responses following breast radiotherapy. MethodsBreast cancer patients with minimal (controls) or marked late radiotherapy changes (cases) were retrospectively selected. DSB were quantified by γH2AX/53BP1 immunofluorescence microscopy 0.5 and 24h after exposure of unstimulated blood lymphocytes to 0.5 and 4Gy X-rays, respectively. Chromosomal aberrations were scored in blood lymphocyte metaphases after 6Gy X-rays. ResultsDespite similar foci levels at 0.5h in cases (n=7) and controls (n=7), foci levels 24h after 4Gy irradiation differed significantly between them (foci per cell were 12.8 in cases versus 10.2 in controls, p=0.004). Increased chromosomal radiosensitivity was also observed in cases (aberrations per cell were 5.84 in cases versus 3.79 in controls, p=0.001) with exchange and deletion type aberrations contributing equally to the difference between cases and controls. Residual foci correlated with formation of deletions (Spearman’s R=0.589, p=0.027) but not exchanges (R=0.367, p=0.197) in blood lymphocytes from the same patients. ConclusionsHigher levels of exchange type aberrations observed among radiosensitive breast cancer patients suggest a role for DSB misrepair, in addition to residual damage, as determinants of late normal tissue damage. Correlation of residual foci levels with deletion type aberration yields in the same cohort confirms their mechanistic linkage.

Heritable Susceptibility Factors for the Development of Cancer

High frequencies of inherited DNA sequence variations (polymorphisms) are found in the human population. The involvement of polymorphic genes (especially for chemical metabolism and DNA repair) in the development of cancer is under intensive investigation. In our studies, we have irradiated blood lymphocytes from normal non-smokers with gamma-rays or UV-light to investigate genotypes and DNA repair functions. We found that XRCC1 399Gln and XRCC3 241Met were deficient in the repair of gamma-ray-but not UV-light-induced DNA damage that led to the expression of chromosome aberrations; therefore the variant genotypes are defective in base excision repair. The reverse was found with XPD 312Asn and XPD 751Gln; therefore they are defective in nucleotide excision repair. XRCC1 194Trp, OGG1 326Cys and APE1 148Glu had no DNA repair deficiency based on our experimental conditions. In another study, we investigated the role of some of these genes on the development of lung cancer. We found a significant increase of chromosome aberrations in patients and controls that had the XPD 751Gln and GSTM1 null genotypes, indicating a mechanistic causation of the disease. Therefore, inheritance of susceptibility genes can have significant impact on disease burden in the population. On the other hand, there are many questions that need to be addressed in order to evaluate the impact of susceptibility on cancer. These questions include the understanding of combinations of different polymorphic genes for susceptibility and of specific disease susceptibility for different ethnic populations.

Functional characterization of polymorphisms in DNA repair genes using cytogenetic challenge assays.

A major barrier to understanding the role of polymorphic DNA repair genes for environmental cancer is that the functions of variant genotypes are largely unknown. Using our cytogenetic challenge assays, we conducted an investigation to address the deficiency. Using X-rays or ultraviolet (UV) light, we irradiated blood lymphocytes from 80 nonsmoking donors to challenge the cells to repair the induced DNA damage, and we analyzed expression of chromosome aberrations (CA) specific to the inducing agents. We have genotyped polymorphic DNA repair genes preferentially involved with base excision repair (BER) and nucleotide excision repair (NER) activities (XRCC1, XRCC3, APE1, XPD) corresponding to the repair of X-ray- and UV light-induced DNA damage, respectively. We expected that defects in specific DNA repair pathways due to polymorphisms would cause corresponding increases of specific CA. From our data, XRCC1 399Gln and XRCC3 241Met were associated with significant increases in chromosome deletions compared with the corresponding homozygous wild types (18.27 1.1 vs 14.79 1.2 and 18.22 0.99 vs 14.20 1.39, respectively); XPD 312Asn and XPD 751Gln were associated with significant increases in chromatid breaks compared with wild types (16.09 1.36 vs 11.41 0.98 and 16.87 1.27 vs 10.54 0.87, respectively), p < 0.05. The data indicate that XRCC1 399Gln and XRCC3 241Met are significantly defective in BER, and the XPD 312Asn and XPD 751Gln are significantly defective in NER. In addition, the variant genotypes interact significantly, with limited overlap of the two different repair pathways.

Expansion of human lymphocyte populations expressing specific immune reactivities. III. Specific colonies, either cytotoxic or proliferative, obtained from a population of responder cells primed in vitro. Preliminary immunogenetic analysis

Human alloreactive cell lines were maintained in culture over prolonged period of some using conditioned medium. Primed lymphocyte typing reactivity was observed in for only 1 mo, but these T cell lines have remained for more than 7 mo cytotoxic. Using as growth promoter an irradiated autologous feeder consisting of irradiated blood lymphocytes and the lectin leucoagglutinin, we have derived by limiting in vitro primed allogeneic combinations, primary colonies for primary immune reactivities either cytotoxic (the rarest observed) or PLT the colonies). Furthermore, each monofunctional primary colony when tested for PLT reactivity on a panel of unrelated PBL, always showed a restricted specificity when the original primed population. The PLT reactivity of each of the primary lasting in contrast to their growth potential. The CML reactivity of the primary the T cell lines, was long lasting as was their growth potential.