Radiosensitivity Of Lymphocytes Research Articles

Clinical Factors Influencing the Radiation Dose of Circulating Immune Cells during Radiotherapy for Small Cell Lung Cancer.

Small cell lung cancer (SCLC) has garnered significant attention due to its high malignancy, propensity for distant metastasis, and poor prognosis. Radiotherapy remains the cornerstone of treatment for limited-stage small cell lung cancer (LS-SCLC). However, outcomes with radiotherapy alone or in combination with chemotherapy remain suboptimal. Radiotherapy can induce lymphopenia by directly irradiating hematopoietic organs or destroying mature circulating lymphocytes, leading to immunosuppression and consequently diminishing therapeutic efficacy. The estimated dose of radiation to immune cells (EDRIC) model integrates factors such as hemodynamics, lymphocyte radiosensitivity, and proliferation capacity. This study employs the EDRIC model with enhancements to calculate the circulating immune cell radiation dose. By utilizing the EDRIC methodology, the study explores the correlation between EDRIC and tumor target size, average lung dose, average heart dose, clinical features, and peripheral blood lymphocytopenia during radiotherapy for LS-SCLC, aiming to inform personalized patient treatment strategies. This study analyzed data from 64 LS-SCLC patients who met the inclusion criteria at the General Hospital of Ningxia Medical University from January 2023 to January 2024, all of whom received radical thoracic conventional fractionated radiotherapy. Lymphocyte counts were recorded at the following points: before radiotherapy, at the lowest observed value during radiotherapy, at the end of radiotherapy, and one-month post-radiotherapy. Dosimetric data, including average lung, heart, and body doses, were extracted from the treatment planning system, and the circulating EDRIC was calculated using this model. The relationship between EDRIC values and therapeutic outcomes was analyzed. In LS-SCLC, the EDRIC model effectively predicts lymphocyte count reduction, correlating with planning target volume (PTV; cm3), TNM stage, and the percentage of target lesion shrinkage. Post-radiotherapy, there was a significant decrease in peripheral blood lymphocyte counts, with greater EDRIC values indicating more pronounced lymphocyte reduction.

Increased dicentric chromosome in peripheral lymphocytes is related to acute skin toxicity induced by radiotherapy in cancer patients

ObjectiveTo investigate the impacts of radiotherapy (RT) on dicentric chromosomes in peripheral blood lymphocytes of cancer patients, in order to explore the relationship between dicentric chromosomes and RT-induced adverse reactions. MethodsA total of 33 cancer patients after postoperative RT in a tertiary hospital from October 2021 to May 2022 were enrolled in this study. These patients were grouped according to the grade of acute skin and marrow toxicities determined based on the scoring criteria for acute morbidity developed by the Radiation Therapy Oncology Group (RTOG). Peripheral blood samples were collected from each patient before and after RT, followed by whole-blood lymphocyte culture and chromosome analysis. Dicentric chromosomes were searched automatically using a high-throughput chromosome analysis system and were then confirmed manually. Finally, the relationships of the frequency of dicentric chromosomes (also referred to as the dic frequency) with acute skin and marrow toxicities were assessed. ResultsAfter RT, the mean counts of white blood cells (WBCs), lymphocytes, and platelets significantly decreased, while the red blood cells (RBCs) and hemoglobin notably increased (P ​< ​0.001), while the dic frequency was elevated remarkably, significantly higher in patients with higher-grade (>1) acute skin toxicities compared to those with lower-grade (=1) acute skin toxicities (Z ​= ​−1.985, P ​= ​0.047). However, no significant relationship was observed between the dic frequency and acute marrow toxicity after RT (P ​> ​0.05). Logistic regression showed that radiosensitivity denoted by the post-RT dic frequency in peripheral blood lymphocytes produced insignificant impacts on the severity of RT-induced acute skin toxicities (P ​= ​0.060). ConclusionThe elevated dic frequency in peripheral blood lymphocytes of cancer patients with higher-grade acute skin toxicities suggests enhanced radiosensitivity of peripheral blood lymphocytes, which is associated with the occurrence of RT-induced adverse reactions.

Lymphocyte radiosensitivity: An extension to the linear-quadratic model?

Background and purposeThe linear-quadratic (LQ) model has been pivotal for evaluating the effects of radiation on cells, but it is primarily characterized by linear responses, which has exhibited limitations when applied to lymphocyte data. The present research aims to address these limitations and to explore an alternative model extended from the conventional LQ model. Materials and methodsLiterature providing lymphocyte counts from assays investigating apoptosis and survival after in vitro irradiation was selected. To address the nonlinearity in lymphocyte responses to radiation, we developed a saturation model characterized by a negative exponential relationship between radiation dose and cellular response. We compared the performance of this saturation model against that of conventional models, including the LQ model and its variants (linear model LM and linear-quadratic-cubic model LQC), as well as the repair-misrepair (RMR) model. The models were evaluated based on prediction-residual plots, residual standard errors, and the Akaike information criterion (AIC). We applied the saturation model to two additional datasets: (1) a dataset from the existing literature that assessed stimulated and unstimulated human lymphocytes exposed to gamma irradiation in vitro and (2) a novel dataset involving T lymphocytes from rodent spleens after exposure to various radiation types (X-rays and protons). ResultsThe literature (n = 15 out of 2342) showed that lymphocyte apoptosis varies with dose, time and experimental conditions. The saturation model had a lower AIC of 718 compared to the LM, LQ, LQC and RMR models (AIC of 728, 720, 720 and 734, respectively). The saturation model had a lower residual error and more consistent error distribution. Integrating time as a covariate, the saturation model also had a better AIC for demonstrating time-dependent variations in lymphocyte responses after irradiation. For datasets involving unstimulated lymphocytes before irradiation, the saturation model provided a more accurate fit than did the LM, LQ, and RMR models. In these cases, the fit of the saturation model was comparable to that of the LQC model but offered an advantage when extrapolating to higher doses, where the LQC model might underestimate survival. For stimulated lymphocytes, which are radioresistant, all the models approximated the LM. Both the LQ and saturation models indicated greater radiosensitivity to protons in vitro. ConclusionThe new “saturation model” performed better than the LQ model in quantifying lymphocyte apoptosis and survival, estimating time dependency and assessing the role of radiation modalities or lymphocyte stimulation. Further experiments are warranted to experimentally explore the validity of the saturation model as a promising alternative in the clinical setting.

A review on lymphocyte radiosensitivity and its impact on radiotherapy.

It is well known that radiation therapy causes lymphopenia in patients and that this is correlated with a negative outcome. The mechanism is not well understood because radiation can have both immunostimulatory and immunosuppressive effects. How tumor dose conformation, dose fractionation, and selective lymph node irradiation in radiation therapy does affect lymphopenia and immune response is an active area of research. In addition, understanding the impact of radiation on the immune system is important for the design and interpretation of clinical trials combining radiation with immune checkpoint inhibitors, both in terms of radiation dose and treatment schedules. Although only a few percent of the total lymphocyte population are circulating, it has been speculated that their increased radiosensitivity may contribute to, or even be the primary cause of, lymphopenia. This review summarizes published data on lymphocyte radiosensitivity based on human, small animal, and in vitro studies. The data indicate differences in radiosensitivity among lymphocyte subpopulations that affect their relative contribution and thus the dynamics of the immune response. In general, B cells appear to be more radiosensitive than T cells and NK cells appear to be the most resistant. However, the reported dose-response data suggest that in the context of lymphopenia in patients, aspects other than cell death must also be considered. Not only absolute lymphocyte counts, but also lymphocyte diversity and activity are likely to be affected by radiation. Taken together, the reviewed data suggest that it is unlikely that radiation-induced cell death in lymphocytes is the sole factor in radiation-induced lymphopenia.

Increased Radiation Sensitivity in Patients with Phelan-McDermid Syndrome.

Phelan-McDermid syndrome is an inherited global developmental disorder commonly associated with autism spectrum disorder. Due to a significantly increased radiosensitivity, measured before the start of radiotherapy of a rhabdoid tumor in a child with Phelan-McDermid syndrome, the question arose whether other patients with this syndrome also have increased radiosensitivity. For this purpose, the radiation sensitivity of blood lymphocytes after irradiation with 2Gray was examined using the G0 three-color fluorescence in situ hybridization assay in a cohort of 20 patients with Phelan-McDermid syndrome from blood samples. The results were compared to healthy volunteers, breast cancer patients and rectal cancer patients. Independent of age and gender, all but two patients with Phelan-McDermid syndrome showed significantly increased radiosensitivity, with an average of 0.653 breaks per metaphase. These results correlated neither with the individual genetic findings nor with the individual clinical course, nor with the respective clinical severity of the disease. In our pilot study, we saw a significantly increased radiosensitivity in lymphocytes from patients with Phelan-McDermid syndrome, so pronounced that a dose reduction would be recommended if radiotherapy had to be performed. Ultimately, the question arises as to the interpretation of these data. There does not appear to be an increased risk of tumors in these patients, since tumors are rare overall. The question, therefore, arose as to whether our results could possibly be the basis for processes, such as aging/preaging, or, in this context, neurodegeneration. There are no data on this so far, but this issue should be pursued in further fundamentally based studies in order to better understand the pathophysiology of the syndrome.

Chromosomal radiosensitivity of human breast carcinoma cells and blood lymphocytes following photon and proton exposures

Breast carcinomas (BC) are among the most frequent cancers in women. Studies on radiosensitivity and ionizing radiation response of BC cells are scarce and mainly focused on intrinsic molecular mechanisms but do not include clinically relevant features as chromosomal rearrangements important for radiotherapy. The main purpose of this study was to compare the ionizing radiation response and efficiency of repair mechanisms of human breast carcinoma cells (Cal 51) and peripheral blood lymphocytes (PBL) for different doses and radiation qualities (60Co γ-rays, 150 MeV and spread-out Bragg peak (SOBP) proton beams). The radiation response functions obtained using the conventional metaphase assay and premature chromosome condensation (PCC) technique enabled us to determine the number of chromosomal breaks at different time after irradiation. Both cytogenetic assays used confirmed the higher biological radiosensitivity for proton beams in tumor cells compared to PBL, corresponding to higher values of the linear LQ parameter α. additionally, the ratio of the LQ parameters β/α describing efficiency of the repair mechanisms, obtained for chromosome aberrations, showed higher numbers for PBL than for Cal 51 for all exposures. Similar results were observed for the ratio of PCC breaks determined directly after irradiation to that obtained 12 h later. This parameter (t0/t12) showed faster decrease of the repair efficiency with increasing LET value for Cal 51 cells. This finding supports the use of the proton therapy for breast cancer patients.

High Dose Rate and Fractionation to Reduce Radiation-Induced Lymphopenia: In Vivo Derivation of Lymphocyte Radiosensitivity Using Patient-Specific Blood Flow Simulations

<h3>Purpose/Objective(s)</h3> Radiation induced lymphopenia (RIL) has recently gained attention due to its correlation with outcome/survival in a range of indications, particularly when combining radiotherapy (RT) with immunotherapy. The purpose of this study is to use a dynamic blood circulation model combined with observed lymphocyte depletion in patients to derive the in vivo lymphocyte radiosensitivity and study the effect of fast delivery techniques. <h3>Materials/Methods</h3> We evaluated weekly Absolute Lymphocyte Counts (ALC) during RT and follow-up (median 7 measurements per patient) in 17 patients with hepatocellular carcinoma (HCC) treated with RT alone in 15 fractions (fx) using conventional dose rates. We utilized HEDOS, a time-dependent, whole-body, blood flow computational framework, in combination with explicit liver blood flow modeling, to calculate the dose volume histogram for circulating lymphocytes. We utilized linear-quadratic cell survival and an exponential recovery model optimized for lymphocyte radiation sensitivity, α (and β using α/β=2), and the daily recovery source term. We investigated the impact of using a 5-fx treatment regimen (currently investigated in a randomized trial – NCT03186898) and increasing the dose rate to delivery times <<1s (FLASH). The primary endpoints of interest were relative ALC depletion measured at nadir and time to recovery of 80% of baseline ALC. <h3>Results</h3> The <i>in-vivo</i> derived patient-specific lymphocyte radiation sensitivity has a mean of 0.7 <i>Gy⁻¹</i> (range 0.28 – 1.23) after optimal fitting using conventional fractionation and dose rate. Simulating a 5-fx treatment regimen at the conventional dose rate reduces ALC depletion by 8% on average, with an interquartile range (IQR) from 3% to 16% and mean reduction in number of days until recovery by 26% (IQR 21 – 31%) both caused by the varying patient-specific lymphocyte radiosensitivity. Simulating the 15-fx regimen with FLASH dose rates leads to a 13% reduction (IQR 3 – 23%) in ALC depletion and a mean reduction in number of days until recovery by 9% (IQR 2 – 116%). Combining the shorter, 5-fx, treatment regimen with FLASH dose rates leads to a mean reduction in ALC depletion by 45% (IQR 41 – 56%) and mean reduction in time to ALC recovery by 67% (IQR 54 – 80%). <h3>Conclusion</h3> We developed a patient-specific computational framework to simulate lymphocyte depletion in patients receiving RT depending on fractionation and dose rate. We observed that increasing dose rate at the same fractionation reduced ALC depletion more significantly than reducing the number of fractions. High dose rates led to an increased sparing of lymphocytes when shortening the fractionation regimen, particularly for patients with radiosensitive lymphocytes at elevated risk.

A comparative study of genotoxicity endpoints for women exposed to different levels of indoor radon concentrations

Background and purpose Radon and its radioactive progenies are the most important source of ionizing radiation of natural origin, being classified as a Group 1 carcinogen. The aim of this study is to investigate the genotoxic effects of a wide range of indoor radon concentrations, as well as the kinetics of the process of repairing DNA-induced lesions by a challenging dose of gamma irradiation. Material and methods Female subjects residing in the Băiţa-Ştei radon priority area were selected as the exposed group. The reference group was comprised of women from the same county (Bihor), but located in an area with an average indoor radon concentration typical of the county from which they were taken. Radon concentration values of 300 Bq/m3 and 148 Bq/m3, respectively, were chosen as a threshold in order to capture the impact of radon exposure between the groups. The alkaline comet assay was used in order to measure the DNA damage, as well as the repair kinetics at 2 and 24 h after 2 Gy challenging doses of gamma irradiation using peripheral blood lymphocytes. From the serum of the subjects, the oxidative damage by 8-hydroxydeoxyguanosine as well as the PARP induction was evaluated. The chromosomal aberrations were evaluated using the Cytokinesis Block MicroNucleus Assay. Results A statistically significant increase was observed in terms of DNA-induced lesions assessed by comet assay for the exposed group compared to the reference group. A positive correlation was obtained between DNA damage and the annual effective dose, respectively with the radon progenies concentrations. A statistically significant difference was also observed for the frequency of the micronuclei between the exposed – reference groups. Significantly faster repair kinetics of DNA-induced lesions was recorded for the first 2 h after gamma irradiation in the reference group compared to the exposed group. Using the threshold of 300 Bq/m3 for radon concentration, faster kinetics of DNA damage repair for people exposed to low radon concentrations, compared to those exposed to higher concentrations for the second phase of DNA repair kinetics was observed. Conclusion An increased radiosensitivity of lymphocytes, as well as slower repair kinetics, may be associated with exposure to higher indoor radon concentrations.

Prognostic value of the micronucleus assay for clinical endpoints in neoadjuvant radiochemotherapy for rectal cancer

BackgroundThe question whether lymphocyte radiosensitivity is representative of patients’ response to radiotherapy (RT) remains unsolved. We analyzed lymphocyte cytogenetic damage in patients who were homogeneously treated with preoperative radiochemotherapy (RCT) for rectal cancer within clinical trials. We tested for interindividual variation and consistent radiosensitivity after in-vivo and in-vitro irradiation, analyzed the effect of patients’ and RCT characteristics on cytogenetic damage, and tested for correlations with patients’ outcome in terms of tumor response, survival and treatment-related toxicity.MethodsThe cytokinesis-block micronucleus cytome (CBMNcyt) assay was performed on the peripheral blood lymphocytes (PBLCs) of 134 patients obtained before, during, at the end of RCT, and during the 2-year follow-up. A subset of PBLCs obtained before RCT was irradiated in-vitro with 3 Gy. RCT included 50.4 Gy of pelvic RT with 5-fluorouracil (5-FU) alone (n = 78) or 5-FU plus oxaliplatin (n = 56). The analyzed variables included patients’ age, gender, RT characteristics (planning target volume size [PTV size], RT technique), and chemotherapy characteristics (5-FU plasma levels, addition of oxaliplatin). Outcome was analyzed as tumor regression, patient survival, and acute and late toxicity.ResultsCytogenetic damage increased significantly with the radiation dose and varied substantially between individuals. Women were more sensitive than men; no significant age-dependent differences were observed. There was a significant correlation between the cytogenetic damage after in-vitro irradiation and in-vivo RCT. We found a significant effect of the PTV size on the yields of cytogenetic damage after RCT, while the RT technique had no effect. Neither the addition of oxaliplatin nor the 5-FU levels influenced cytogenetic damage. We found no correlation between patient outcome and the cytogenetic damage.ConclusionsWe found consistent cytogenetic damage in lymphocytes after in-vivo RCT and in-vitro irradiation. Gender was confirmed as a well-known, and the PTV size was identified as a less well-known influencing variable on lymphocyte cytogenetic damage after partial-body irradiation. A consistent level of cytogenetic damage after in-vivo and in-vitro irradiation may indicate the importance of genetic factors for individual radiosensitivity. However, we found no evidence that in-vivo or in-vitro irradiation-induced cytogenetic damage is an adequate biomarker for the response to RCT in rectal cancer patients.

ВПЛИВ ІОНІЗУЮЧОГО ВИПРОМІНЮВАННЯ IN VITRO НА ГЕНОМ ЛІМФОЦИТІВ ПЕРІФЕРИЧНОЇ КРОВІ БЕЗСИМПТОМНИХ НОСІЇВ МУТАЦІЇ 5382insC У ГЕНІ BRCA1

One of the hereditary factors affecting the development of breast and ovarian cancer is the 5382insC mutation in BRCA1 gene. But, nearly 15 % of carriers of this mutation do not manifest cancer during their lifetime. At present, the features of the development of spontaneous and induced genomic instability in asymptomatic carriers of BRCA1 mutations are studied insufficiently. The aim of the work was to evaluate the effect of the 5382insC BRCA1 mutation on the radiosensitivity of lymphocytes of individuals without an established oncopathology. The cultivation of blood lymphocytes obtained from 9 women (3 individuals with the 5382insC BRCA1 mutation without established oncopathology, and 6 conditionally healthy volunteers) was carried out. Some of the cultures were irradiated with γ-quanta (IBL-237C emitter, power 2.34 Gy/min) at a dose of 1.0 Gy before cultivation. For evaluation of the relative level of DNA damage the method of Сomet assay was applied. It was found that spontaneous level of DNA damage in cultures of lymphocytes of carriers of the BRCA1 5382insC mutation was statistically significantly (p &lt; 0.01) higher than in the control group. After exposure to ionizing radiation for lymphocyte cultures of individuals with BRCA1 5382insC mutation, a decrease (p &lt; 0.01) in the level of cells with a high degree of DNA damage was observed while the apoptotic activity was found to be increased (p &lt; 0.01). It has been suggested that an increase in the elimination of damaged cells due to apoptotic activity in response to the action of genome-damaging factors is one of the effective mechanisms that can significantly reduce the likelihood of cancer in asymptomatic carriers of the BRCA1 gene mutations.

A framework for modeling radiation induced lymphopenia in radiotherapy

IntroductionAssociations between radiation-induced lymphopenia (RIL) and survival have been extensively reported. However, the immune system is not considered as an organ-at-risk (OAR) in radiotherapy. This study aimed to develop the framework of an immune OAR model that may be utilized to predict and minimize RIL. MethodsA dynamic model was first developed for lymphocyte trafficking among 5 compartments of the immune system. Radiation dose to the circulating lymphocytes in each compartment was calculated based on the doses to fixed structures of each immune compartment and blood flow patterns. A RIL model was developed based on lymphocyte dynamics, lymphocyte radiosensitivity and reproductivity, and the dose to the lymphocytes. The model was tested in 51 patients by fitting it to weekly-measured absolute lymphocyte counts (ALC) for each patient, considering lymphocyte radiosensitivity and reproductivity as patient-dependent fitting parameters. ResultsThe fitting was almost perfect for 20 patients, with sum of square of errors (SSE) between measured and predicted ALCs < 0.5. It was acceptable for another 27 patients, with SSE = 0.5~4.0. Only 4 patients had SSE > 4.0. The fitting also provided a method of in vivo estimation of radiosensitivity (α) for each patient. The median α was 0.40 Gy−1 for the 51 patients, consistent with in vitro measured data of 0.41 Gy−1 in the literature. ConclusionWe have presented a framework of developing an immune OAR model that has the potential to predict and minimize RIL in radiotherapy.

Chromosomal radiosensitivity of triple negative breast cancer patients

Purpose: Based on clinical and molecular data, breast cancer is a heterogeneous disease. Breast cancers that have no expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) are defined as triple negative breast cancers (TNBCs); luminal cancers have different expressions of ER, PR and/or HER2. TNBCs are frequently linked with advanced disease, poor prognosis and occurrence in young African women, and about 15% of the cases are associated with germline BRCA1/2 mutations. Since radiotherapy is utilized as a principle treatment in the management of TNBC, we aimed to investigate the chromosomal instability and radiosensitivity of lymphocytes in TNBC patients compared to luminal breast cancer patients and healthy controls using the micronucleus (MN) assay. The effect of mutations in breast cancer susceptibility genes on chromosomal radiosensitivity was also evaluated.Methods: Chromosomal radiosensitivity was evaluated in the G0 (83 patients and 90 controls) and S/G2 (34 patients and 17 controls) phase of the cell cycle by exposing blood samples from all patients and controls to 2 and 4 Gy ionizing radiation (IR).Results: In the G0 MN assay, the combined cohort of all breast cancer, TNBC and luminal patients’ exhibit significantly elevated spontaneous MN values compared to controls indicating chromosomal instability. Chromosomal radiosensitivity is also significantly elevated in the combined cohort of all breast cancer patients compared to controls. The TNBC patients, however, do not exhibit enhanced chromosomal radiosensitivity. Similarly, in the S/G2 phase, 76% of TNBC patients do not show enhanced chromosomal radiosensitivity compared to the controls. In both the G0 and S/G2 phase, luminal breast cancer patients demonstrate a shift toward chromosomal radiosensitivity compared to TNBC patients and controls.Conclusions: The observations of the MN assay suggest increased chromosomal instability and chromosomal radiosensitivity in South African breast cancer patients. However, in TNBC patients, the irradiated MN values are not elevated. Our results suggest that the healthy lymphocytes in TNBC patients could handle higher doses of IR.

Granulocyte radiolabeling using Leukokit® with introduction of a density gradient medium as ancillary material.

Radiolabeled white blood cells (WBCs) prepared in radiopharmacies are used to detect infectious or inflammatory sites with scintigraphy. Radiolabeling can be performed by using a disposable closed device, Leukokit®. Nevertheless, owing to the high radiosensitivity of lymphocytes, the question of eliminating lymphocytes before granulocyte radiolabeling is still a controversial step. The aim of this study was to assess a new modified Leukokit® with a protocol that allows granulocyte radiolabeling only. Seventy patients (male/female: 40/30, mean age: 61 years) with suspected infectious diseases underwent labeled leukocyte scintigraphy by radiolabeling with a density gradient medium in addition to Leukokit®. Compliance and quality of radiolabeling were checked according to the following criteria: visual inspection, labeling efficiency, cell viability (Trypan blue exclusion test), cell subset recovery test, lymphocyte elimination rate (granulocyte/WBC rate) and sterility test using media fills. Visual inspection showed that all cell preparations were free of residual cell clumps or fibrin clots. Mean labeling efficiency was 70.4±9.4% compliant with EANM Guidelines for leukocyte labeling. The mean cell viability was 97.7±1.4% (>96%). The mean number of leucocytes injected was 116x106 ±62x106 (>50x106). The mean erythrocyte/WBC ratio was 2.1 ±0.9 (<3) and the removed lymphocyte rate was 97.4±1.6% (>90%). Finally, the three sterility tests were negative and therefore successful. Purification of granulocytes with Leukokit® can safely, easily and effectively be performed using a density gradient medium. Moreover, clarification regarding the status of density gradient medium could provide support for its clinical use even if further studies are needed. Since all technical obstacles have been removed, the precautionary principle should apply and lead users to eliminate lymphocytes that are highly radiosensitive cells and whose in vivo fate is uncertain.

Comparing Lymphocyte Radiosensitivity of Prostate Cancer Patients with Healthy Donors Using Micronuclei and Chemical Premature Chromosome Condensation Tests.

Background: Cytogenetic tests are usually used for diagnosing predisposed individuals to cancer by determining their lymphocyte radiosensitivity.Objective: To determine the potential role of radiosensitivity in predisposition of prostate cancer by comparing lymphocyte radiosensitivity of prostate cancer patients with healthy donors.Materials and Methods: In this experimental study, the blood samples of 10 prostate cancer patients and 10 healthy donors were irradiated to 0.25, 0.5, 1, 2, 4 and 6 Gy ionizing radiation produced by a 6MV Linac. One sample of each group receiving no radiation was regarded as the background. The micronuclei (MN) and chemical premature chromosome condensation (PCC) cytogenetic tests were performed on all samples and the numbers of MN and PCC rings were scored. Dose-response curves were plotted for both healthy and cancerous groups with two tests.Results: There was a significant difference between the numbers of MN within each group due to different levels of radiation doses. There was also a significant difference between the two groups in all identical doses, with the exception of 6 Gy. The chemical PCC test indicated a significant difference between the scored PCC rings in each group at doses higher than 0.25 Gy. However, no differences were noted between the healthy donors and prostate cancer patients receiving the same level of doses. Conclusion: MN test can be considered as a reliable indicator of predisposition of prostate cancer. On the other hand, the chemical PCC test could not differentiate between healthy donors and prostate cancer patients at the dose range examined in this study.

In vitro radiosensitivity of lymphocytes from high-background radiation ar-ea inhabitants in Indonesia: a pilot study using the G0 micronucleus assay

In vitro radiosensitivity of lymphocytes from high-background radiation ar-ea inhabitants in Indonesia: a pilot study using the G0 micronucleus assay

Micronucleus Assay-based Evaluation of Radiosensitivity of Lymphocytes among Inhabitants Living in High Background Radiation Area of Mamuju, West Sulawesi, Indonesia.

Naturally occurring radiation can be found all around us and account for most of the radiation received by human beings each year. Indonesia has a region with high-dose natural radiation located in the suburb of West Sulawesi province with a dose rate up to 2800 nSv/h; however, its impact was not fully understood. The aim of this study was to evaluate the radiosensitivity of 12 peripheral blood lymphocytes of inhabitant from high background radiation area (HBRA) and 10 from normal background radiation area (NBRA) based on cytokinesis-block micronucleus (CBMN) assay after challenged with 1.5 Gy of gamma ray. The analysis of CBMN was done according to standard procedure as per IAEA guidelines, and frequency of binucleate (mitotic) cells with micronuclei (MN) was scored in around 2000 binucleate lymphocytes cells per culture in microscopic analysis. Mean MN frequency for HBRA was lower than that of NBRA (0.121 vs. 0.189) after irradiation, indicating an adaptive response in HBRA group that resulted in less radiosensitivity; however, there was no statistically significant different (P > 0.05) between these two groups. The MN number was higher in women compared to men for both HBRA (0.15 vs. 0.09) and NBRA (0.216 vs. 0.147) groups. Besides, there was no statistically significant difference (P > 0.05) in Nuclear Division Index (NDI), as measured in 500 metaphase cells with published formula, between HBRA and NBRA samples (1.24 vs. 1.21). The lower MN frequency prompts us to conclude that there is an adaptive response in the lymphocytes of inhabitants as an indicator of lower radiosensitivity to the high natural radiation exposure. Further studies using large number of samples are required to obtain more comprehensive conclusion along with the assessment of other types of radiosensitivity-related biomarkers.

Idelalisib may have the potential to increase radiotherapy side effects

IntroductionIdelalisib is approved for the treatment of relapsed chronic lymphocytic leukemia together with Rituximab and for monotherapy of follicular B-cell non-Hodgkin’s lymphoma and small lymphocytic lymphoma. It is a potent and selective phosphatidylinositol 3-kinase-δ (PI3K-δ) inhibitor. PI3K-δ primarily is expressed in B-cells and prevents effectively proliferation in malignant B-cells.MethodsWe provide a detailed report on treatment history and photo documentation of acute adverse effects of radiation therapy with simultaneous Idelalisib medication in one case of B-CLL. Radiosensitivity tests were performed for the index patient under Idelalisib and after the addition of Idelalisib to healthy individuals’ blood. Radiosensitivity in human lymphocytes was analyzed with a three color in situ hybridization assay. Primary skin fibroblasts were studied after a treatment with Idelalisib for apoptosis, necrosis and cell cycle using flow cytometry. DNA double-strand break repair was analyzed by γH2AX immunostaining.ResultsThe index patient presented a strong grade 2 radiodermatitis and grade 3 mucositis after irradiation with 20 Gy and a simultaneous intake of Idelalisib. Irradiations without Idelalisib medication were well tolerated and resulted in not more than grade 1 radiodermatitis. The index patient under Idelalisib had a radiosensitivity of 0.62 B/M which is in the range of clearly radiosensitive patients. A combined treatment of lymphocytes with 2 Gy and 10 nmol/l Idelalisib showed a tendency to an increased radiosensitivity. We found a clear increase of apoptosis as a result of the combined treatment in the Idelalisib dose range of 1 to 100 nmol/l compared to solely irradiated cells or solely Idelalisib treated cells (p = 0.05).ConclusionA combined Idelalisib radiotherapy treatment has an increased risk of side effects. However, combined therapy seems to be feasible when patients are monitored closely.

Assessment of Correlation between Chromosomal Radiosensitivity of Peripheral Blood Lymphocytes after In vitro Irradiation and Normal Tissue Side Effects for Cancer Patients Undergoing Radiotherapy.

Patients receiving identical radiation treatments experience different effects, from undetectable to severe, on normal tissues. A crucial factor of radiotherapy related side effects is individual radiosensitivity. It is difficult to spare surrounding normal tissues delivering radiation to cancer cells during radiotherapy. Therefore, it may be useful to develop a simple routine cytogenetic assay which would allow the screening of a large number of individuals for radiosensitivity optimizing tumor control rates and minimizing severe radiotherapy effects with possibility to predict risk level for developing more severe early normal tissue adverse events after irradiation. This study was conducted to assess the correlation between in vitro radiosensitivity of peripheral blood lymphocytes from cancer patients who are undergoing radiotherapy using the cytokinesis-block micronucleus (CBMN), G2 chromosomal radiosensitivity assays, and normal tissue acute side effects. The CBMN and G2 chromosomal radiosensitivity assays were performed on blood samples taken from cancer patients before radiotherapy, after first fractionation, and after radiotherapy. Acute normal tissue reactions were graded according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer. This study suggests that there is a correlation between higher frequency of micronuclei after in vitro irradiation of blood samples and higher degree of normal tissue reactions. In addition, higher number of chromatid breaks was observed in patients with more severe normal tissue reactions. This pilot study included only 5 cancer patients, and therefore, further studies with a bigger cohort are required to identify radiosensitive patients.

Comparing Lymphocyte Radiosensitivity of Prostate Cancer Patients with Healthy Donors using Micronuclei and Chemical Premature Chromosome Condensation Tests

Background: Cytogenetic tests are usually used for diagnosing predisposed individuals to cancer by determining their lymphocyte radiosensitivity. Objective: To determine the potential role of radiosensitivity in predisposition of prostate cancer by comparing lymphocyte radiosensitivity of prostate cancer patients with healthy donors. Materials and Methods: The blood samples of 10 prostate cancer patients and 10 healthy donors were irradiated to 0.25, 0.5, 1, 2, 4 and 6 Gy ionizing radiation produced by a 6MV Linac. One sample of each group receiving no radiation was regarded as the background. The micronuclei (MN) and chemical premature chromosome condensation (PCC) cytogenetic tests were performed on all samples and the numbers of MN and PCC rings were scored. Dose-response curves were plotted for both healthy and cancerous groups with two tests. Results: There was a significant difference between the numbers of MN within each group due to different levels of radiation doses. There was also a significant difference between the two groups in all identical doses, with the exception of 6 Gy. The chemical PCC test indicated a significant difference between the scored PCC rings in each group at doses higher than 0.25 Gy. However, no differences were noted between the healthy donors and prostate cancer patients receiving the same level of doses. Conclusion: MN test can be considered as a reliable indicator of predisposition of prostate cancer. On the other hand, the chemical PCC test could not differentiate between healthy donors and prostate cancer patients at the dose range examined in this study.

TNFSF10/TRAIL regulates human T4 effector memory lymphocyte radiosensitivity and predicts radiation-induced acute and subacute dermatitis.

Sensitivity of T4 effector-memory (T4EM) lymphocytes to radiation-induced apoptosis shows heritability compatible with a Mendelian mode of transmission. Using gene expression studies and flow cytometry, we show a higher TNF-Related Apoptosis Inducing Ligand (TRAIL/TNFSF10) mRNA level and a higher level of membrane bound TRAIL (mTRAIL) on radiosensitive compared to radioresistant T4EM lymphocytes. Functionally, we show that mTRAIL mediates a pro-apoptotic autocrine signaling after irradiation of T4EM lymphocytes linking mTRAIL expression to T4EM radiosensitivity. Using single marker and multimarker Family-Based Association Testing, we identified 3 SNPs in the TRAIL gene that are significantly associated with T4EM lymphocytes radiosensitivity. Among these 3 SNPs, two are also associated with acute and subacute dermatitis after radiotherapy in breast cancer indicating that T4EM lymphocytes radiosensitivity may be used to predict response to radiotherapy. Altogether, these results show that mTRAIL level regulates the response of T4EM lymphocytes to ionizing radiation and suggest that TRAIL/TNFSF10 genetic variants hold promise as markers of individual radiosensitivity.