Chromosomal radiosensitivity in breast cancer patients with a known or putative genetic predisposition

The chromosomal radiosensitivity of breast cancer patients with a known or putative genetic predisposition was investigated and compared to a group of healthy women. The chromosomal radiosensitivity was assessed with the G2 and the G0-micronucleus assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy (60)Co gamma-rays after 71 h incubation, and chromatid breaks were scored in 50 metaphases. For the micronucleus assay lymphocytes were exposed in vitro to 3.5 Gy (60)Co gamma-rays at a high dose rate or low dose rate. 70 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients with a known or putative genetic predisposition was on the average more radiosensitive than a population of healthy women, and this with the G2 as well as with the high dose rate and low dose rate micronucleus assay. With the G2 assay 43% of the patients were found to be radiosensitive. A higher proportion of the patients were radiosensitive with the micronucleus assay (45% with high dose rate and 61% with low dose rate). No correlation was found between the G2 and the G0-micronucleus chromosomal radiosensitivity. Out of the different subgroups considered, the group of the young breast cancer patients without family history showed the highest percentage of radiosensitive cases in the G2 (50%) as well as in the micronucleus assay (75-78%).     

Relationship between in vitro chromosomal radiosensitivity of peripheral blood lymphocytes and the expression of normal tissue damage following radiotherapy for breast cancer.

BACKGROUND AND PURPOSE: There is a need for rapid and reliable tests for the prediction of normal tissue responses to radiotherapy, as this could lead to individualization of patient radiotherapy schedules and thus improvements in the therapeutic ratio. Because the use of cultured fibroblasts is too slow to be practicable in a clinical setting, we evaluated the predictive role of assays of lymphocyte chromosomal radiosensitivity in patients having radiotherapy for breast cancer. MATERIALS AND METHODS: Radiosensitivity was assessed using a micronucleus (MN) assay at high dose rate (HDR) and low dose rate (LDR) on lymphocytes irradiated in the G(0) phase of the cell cycle (Scott D, Barber JB, Levine EL, Burril W, Roberts SA. Radiation-induced micronucleus induction in lymphocytes identifies a frequency of radiosensitive cases among breast cancer patients: a test for predispostion? Br. J. Cancer 1998;77;614-620) and an assay of G(2) phase chromatid radiosensitivity ('G(2) assay') (Scott D, Spreadborough A, Levine E, Roberts SA. Genetic predisposition in breast cancer. Lancet 1994; 344: 1444). In a study of acute reactions, blood samples were taken from breast cancer patients before the start of radiotherapy, and the skin reaction documented. 116 patients were tested with the HDR MN assay, 73 with the LDR MN assay and 123 with the G(2) assay. In a study of late reactions, samples were taken from a series of breast cancer patients 8-14 years after radiotherapy and the patients assessed for the severity of late effects according to the'LENT SOMA' scales. 47 were tested with the HDR assay, 26 with the LDR assay and 19 with the G(2) assay. For each clinical endpoint, patients were classified as being normal reactors or 'highly radiosensitive patients' (HR patients (Burnet NG. Johansen J, Turesson I, Nyman J. Describing patients' normal tissue reactions: Concerning the possiblity of individualising radiotherapy dose presciptions based on potential predictive assays of normal tissue radiosensitivity. Int. J. Cancer 1998;79:606-613)). RESULTS: The HR patients could be identified in some of the assays. For example, for acute skin reactions, 9/123 patients were judged as HR; they had significantly higher G(2) scores than normal reactors (P=0.004). For the late reactions, the mean HDR MN scores were higher for the 4/47 patients who had severe telangiectasia (P=0.042) and the 8/47 patients had severe fibrosis (P=0.055). However, there were no trends towards increased chromosomal radiosensitivity with the micronucleus scores at HDR or LDR, or with G(2) chromosomal radiosensitivity. CONCLUSIONS: While these results support the concept of using lymphocytes to detect elevated sensitivity to radiotherapy (as an alternative to fibroblasts), these assays are unlikely to be of assistance for the prediction of normal tissue effects in the clinic in their present form.     

Radiosensitivity in breast cancer assessed by the Comet and micronucleus assays

Spontaneous and radiation-induced genetic instability of peripheral blood mononuclear cells derived from unselected breast cancer (BC) patients (n=50) was examined using the single-cell gel electrophoresis (Comet) assay and a modified G2 micronucleus (MN) test. Cells from apparently healthy donors (n=16) and from cancer patients (n=9) with an adverse early skin reaction to radiotherapy (RT) served as references. Nonirradiated cells from the three tested groups exhibited similar baseline levels of DNA fragmentation assessed by the Comet assay. Likewise, the Comet analysis of in vitro irradiated (5 Gy) cells did not reveal any significant differences among the three groups with respect to the initial and residual DNA fragmentation, as well as the DNA repair kinetics. The G2 MN test showed that cells from cancer patients with an adverse skin reaction to RT displayed increased frequencies of both spontaneous and radiation-induced MN compared to healthy control or the group of unselected BC patients. Two patients from the latter group developed an increased early skin reaction to RT, which was associated with an increased initial DNA fragmentation in vitro only in one of them. Cells from the other BC patient exhibited a striking slope in the dose-response curve detected by the G2 MN test. We also found that previous RT strongly increased both spontaneous and in vitro radiation-induced MN levels, and to a lesser extent, the radiation-induced DNA damage assessed by the Comet assay. These data suggest that clinical radiation may provoke genetic instability and/or induce persistent DNA damage in normal cells of cancer patients, thus leading to increased levels of MN induction and DNA fragmentation after irradiation in vitro. Therefore, care has to be taken when blood samples collected postradiotherapeutically are used to assess the radiosensitivity of cancer patients.     

Individual radiosensitivity measured with lymphocytes may be used to predict the risk of fibrosis after radiotherapy for breast cancer.

BACKGROUND AND PURPOSE: To analyse the relationship of individual cellular radiosensitivity and fibrosis after breast conserving therapy. A new model was used describing the percentage of patients developing fibrosis per year and per patient at risk. PATIENTS AND METHODS: In a retrospective study, 86 patients were included, who had undergone breast conserving surgery and irradiation of the breast with a median dose of 55 Gy (54-55 Gy) given at 2.5 Gy/fraction (n=57) or 2 Gy/fraction (n=29). Median age was 62 years (range 44-86) and median follow-up was 7.5 years (range 5-17). Patients were examined for fibrosis according to the LENT/SOMA score. For analysis, fibrosis was classified as grade 0 and grade 1 (G0-1) or present grade 2 and grade 3 (G2-3). The time to complete development of fibrosis was determined by analysis of yearly mammograms. Individual cellular radiosensitivity was determined by scoring lethal chromosomal aberrations in in vitro irradiated (6 Gy) lymphocytes using metaphase technique. Patients with low/intermediate cellular radiosensitivity were compared with patients with high cellular radiosensitivity using actuarial methods. RESULTS: Ten patients developed fibrosis at 1-8 years after radiotherapy. Individual cellular radiosensitivity was described by normal distribution of lethal chromosomal aberrations, the average was 5.47 lethal aberrations per cell (standard deviation (SD) 0.71). Cellular radiosensitivity was defined as low/intermediate (< or =6.18 lethal aberrations) in 73 patients and high (>6.18 lethal aberrations; mean+SD) in 13 patients. In both groups, the actuarial rate of fibrosis-free patients decreased exponentially with time after radiotherapy. Patients with high cellular radiosensitivity showed a 2.3-fold higher annual rate for fibrosis than patients with intermediate and low radiosensitivity (3.6 versus 1.6% per year). CONCLUSIONS: In breast cancer patients, high individual cellular radiosensitivity as determined by the number of lethal chromosome aberrations in in vitro irradiated lymphocytes might be associated with an enhanced annual rate of fibrosis.     

Radiation-induced micronucleus induction in lymphocytes identifies a high frequency of radiosensitive cases among breast cancer patients: a test for predisposition?

Enhanced sensitivity to the chromosome-damaging effects of ionizing radiation is a feature of many cancer-predisposing conditions. We previously showed that 42% of an unselected series of breast cancer patients and 9% of healthy control subjects showed elevated chromosomal radiosensitivity of lymphocytes irradiated in the G2 phase of the cell cycle. We suggested that, in addition to the highly penetrant genes BRCA1 and BRCA2, which confer a very high risk of breast cancer and are carried by about 5% of all breast cancer patients, there are also low-penetrance predisposing genes carried by a much higher proportion of breast cancer patients, a view supported by recent epidemiological studies. Ideally, testing for the presence of these putative genes should involve the use of simpler methods than the G2 assay, which requires metaphase analysis of chromosome damage. Here we report on the use of a simple, rapid micronucleus assay in G0 lymphocytes exposed to high dose rate (HDR) or low dose rate gamma-irradiation, with delayed mitogenic stimulation. Good assay reproducibility was obtained, particularly with the HDR protocol, which identified 31% (12 out of 39) of breast cancer patients compared with 5% (2 out of 42) of healthy controls as having elevated radiation sensitivity. In the long term, such cytogenetic assays may have the potential for selecting women for intensive screening for breast cancer.     

Effects of ionizing radiation on cells from Fanconi's anemia patients

The lymphocytes from some Fanconi's anemia patients appeared to be more radiosensitive than normal as measured by the number of X-ray-(or bleomycin-) induced chromosome aberrations seen following G2 treatment. Fibroblasts from the same patients, however, all showed the same degree of colony survival as normals following exposure to gamma-rays [Do, 1.13 +/- 0.072 (S.E.) Gy and 1.14 +/- 0.077 Gy for Fanconi's anemia and normal fibroblasts, respectively]. The lack of increased radiosensitivity in Fanconi's fibroblasts was also observed by the same degree of inhibition of DNA synthesis as seen in normals following gamma-irradiation. The results show clearly that there is no increase in radiosensitivity common to all cell types from Fanconi's patients, although an apparent increase in chromosomal radiosensitivity may be seen in the lymphocytes from an occasional patient.     

Enhanced chromosomal radiosensitivity in peripheral blood lymphocytes of larynx cancer patients

PURPOSE: The chromosomal radiosensitivity in peripheral blood lymphocytes of cancer patients was reported to be higher than that of healthy donors. This effect is especially prominent when aberrations induced in the G2 phase of the cell cycle are analyzed. The aim of our study was to investigate if the G2 aberration frequencies in lymphocytes of patients with larynx cancer are higher than in the case of control individuals. Also, we tested if the frequencies of G2 aberrations correlate with side effects of radiotherapy. METHODS AND MATERIALS: Peripheral blood of 38 patients was collected before the onset of radiotherapy, cultured for 72 h, and irradiated with 2 Gy after 67 h. Lymphocytes of 40 healthy donors were treated in the same way. RESULTS: The spontaneous and radiation-induced aberration frequencies in lymphocytes of patients were on average higher than in those of healthy donors. No statistically significant correlation was observed between aberration frequencies in lymphocytes and the degree of both early and late normal tissue reactions. CONCLUSIONS: The chromosomal radiosensitivity of lymphocytes of patients with larynx cancer may be a marker of cancer predisposition; however, it does not appear to have a predictive value for the risk of developing side effects to radiotherapy.     

Individual radiosensitivity measured with lymphocytes may predict the risk of acute reaction after radiotherapy

PURPOSE: We tested whether the chromosomal radiosensitivity of in vitro irradiated lymphocytes could be used to predict the risk of acute reactions after radiotherapy. METHODS AND MATERIALS: Two prospective studies were performed: study A with 51 patients included different tumor sites and study B included 87 breast cancer patients. Acute reaction was assessed using the Radiation Therapy Oncology Group score. In both studies, patients were treated with curative radiotherapy, and the mean tumor dose applied was 55 Gy (40-65) +/- boost with 11 Gy (6-31) in study A and 50.4 Gy +/- boost with 10 Gy in study B. Individual radiosensitivity was determined with lymphocytes irradiated in vitro with X-ray doses of either 3 or 6 Gy and scoring the number of chromosomal deletions. RESULTS: Acute reactions displayed a typical spectrum with 57% in study A and 53% in study B showing an acute reaction of Grade 2-3. Individual radiosensitivity in both studies was characterized by a substantial variation and the fraction of patients with Grade 2-3 reaction was found to increase with increasing individual radiosensitivity measured at 6 Gy (study A, p = 0.238; study B, p = 0.023). For study B, this fraction increased with breast volume, and the impact of individual radiosensitivity on acute reaction was especially pronounced (p = 0.00025) for lower breast volume. No such clear association with acute reaction was observed when individual radiosensitivity was assessed at 3 Gy. CONCLUSION: Individual radiosensitivity determined at 6 Gy seems to be a good predictor for risk of acute effects after curative radiotherapy.     

Chromosomal radiosensitivity in G2-phase lymphocytes identifies breast cancer patients with distinctive tumour characteristics.

A substantial proportion of women with breast cancer exhibit an abnormally high radiosensitivity as measured by the frequency of chromatid breaks induced in G2-phase, PHA stimulated lymphocytes. Chromatid break frequencies were compared for a cohort of previously untreated sporadic breast cancer patients and hospital outpatient controls. In the breast cancer group 46% showed high radiosensitivity compared to 14% of controls (P< 0.001). Comparison of those breast cancer patients with a high G2 radiosensitivity (G2RS) versus those with a low G2RS showed no difference in menopausal status or age but the high G2RS group had on average a lower score on the Nottingham Prognostic Index. Predicted survival in the high G2RS group at 15 years was 55% compared to 36% for the low G2RS group. Furthermore, 81% of tumours from the high G2RS were oestrogen receptor positive compared to 45% from the low G2RS group. Thus high G2RS identifies a sub-population of patients with distinctive tumour characteristics and with a predicted improved prognosis as compared with those in the low G2RS group. Our findings imply that besides influencing risk of breast cancer the genetic factors determining G2 radiosensitivity also influence the tumour characteristics and prognosis in these patients.     

The use of chromosome aberrations in predicting breast cancer risk

In order to assess the usefulness of chromosome aberrations in predicting breast cancer risk, 10 patients with breast cancer diagnosis and appropriately matching 10 healthy controls were chosen. Spontaneous and radiation induced unstable chromosome aberrations in peripheral blood lymphocytes were compared in the two groups. When the spontaneous aberration frequencies were compared, acentric chromosome frequency, scored in the group of patients was significantly higher than that found in the control group (p<0.01). Absolute aberration frequencies as a determinant of radiosensitivity were calculated by subtracting spontaneous aberration frequencies from the frequencies that were obtained following 2 Gy of Co-60 gamma irradiation. Absolute dicentric chromosome frequency significantly increased in the patients1 group (p<0.01) as compared to that observed in the control group. Increases in either spontaneous acentric chromosome frequency or dicentric chromosome frequency as a determinant of an enhanced radiosensitivity in the group of patients may be valuable in predicting breast cancer risk. The studies involving unstable chromosome aberrations can be easily performed and can facilitate cancer diagnosis with minor effort and low cost.     

Chromosomal radiosensitivity in head and neck cancer patients: evidence for genetic predisposition?

The association between chromosomal radiosensitivity and genetic predisposition to head and neck cancer was investigated in this study. In all, 101 head and neck cancer patients and 75 healthy control individuals were included in the study. The G(2) assay was used to measure chromosomal radiosensitivity. The results demonstrated that head and neck cancer patients had a statistically higher number of radiation-induced chromatid breaks than controls, with mean values of 1.23 and 1.10 breaks per cell, respectively (P<0.001). Using the 90th percentile of the G(2) scores of the healthy individuals as a cutoff value for chromosomal radiosensitivity, 26% of the cancer patients were radiosensitive compared with 9% of the healthy controls (P=0.008). The mean number of radiation-induced chromatid breaks and the proportion of radiosensitive individuals were highest for oral cavity cancer patients (1.26 breaks per cell, 38%) and pharynx cancer patients (1.27 breaks per cell, 35%). The difference between patients and controls was most pronounced in the lower age group (相似文献   

Lymphocyte radiosensitivity correlated with pelvic radiotherapy morbidity

PURPOSE: To test the hypothesis that, before treatment, prostate cancer patients who demonstrate a high yield of ex vivo radiation-induced micronucleus (MN) in G(0) lymphocytes represent a patient population with a greater-than-average risk of developing radiotherapy (RT)-related morbidity. METHODS AND MATERIALS: We prospectively conducted the cytokinesis-block MN assay of peripheral blood lymphocytes (PBLs) in 38 prostate cancer patients. Before the initiation of RT, PBLs from each patient were irradiated (1-4 Gy). The mean patient age +/- SEM was 68.7 +/- 1.0 years. The clinical stage was T1 in 17, T2 in 15, and T3 in 6. The preoperative prostate-specific antigen level was < or =4 ng/mL in 5, 4-10 ng/mL in 18, and >10 ng/mL in 15. All patients underwent standardized pelvic external beam radiotherapy (range 41.4-50.4 Gy) and boost (range 16-26 Gy). The mean follow-up +/- SEM was 32.8 +/- 4.6 months. At the end of follow-up, a radiation oncologist scored the GI or GU morbidity according to the Radiation Therapy Oncology Group criteria without knowledge of the MN data. RESULTS: We found that between the average reactors (n = 25; i.e., patients who had Grade 1 or less RT-related morbidity) and over reactors (n = 13; i.e., patients who developed Grade 2 or greater RT-related morbidity), the differences in the ex vivo radiation dose-response relationship of MN yield in PBLs were highly significant, especially at doses of > or =2 Gy. Also, the development of RT-related morbidity correlated with the radiation dose-response relationship of MN yield in PBLs before treatment, but did not correlate with any of the patients' clinical variables. CONCLUSION: Our findings suggest that the pre-RT ex vivo radiation dose-response relationship of MN yield in PBLs may be a significant predictive factor for the development of GI or GU morbidity in prostate cancer patients after pelvic RT.     

Individualization of radiotherapy in breast cancer patients: possible usefulness of a DNA damage assay to measure normal cell radiosensitivity.

PURPOSE: The purpose of this study was to determine whether the distribution of sensitivities in breast cancer patients, measured using a DNA damage assay on lymphocytes, is likely to provide sufficient discrimination to enable the reliable identification of patients with abnormal sensitivities.MATERIAL AND METHODS: Radiosensitivity (x) was assessed in 226 samples of lymphocytes from unselected women with breast cancer and was quantified as the initial number of DNA double-strand breaks (dsb) induced per Gy and per DNA unit (200 Mbp).RESULTS: The existence of an inter-individual variation in the parameter (x) is described through the range (0.40-4.72 dsb/Gy/DNA unit) of values found, which have been fitted to the mathematical model defined by the log-normal distribution (mu = 0.42+/-0.03; sigma = 0.52+/-0.03; R(2)=0.9475). A total of 189 patients received radiotherapy after surgical treatment. Among them, we have detected 15 patients who developed severe skin reactions and we have compared their radiosensitivity values with the rest of patients treated.CONCLUSIONS: Our results suggest that DNA initial damage measured on lymphocytes offers an approach to predict the acute response of human normal tissues prior to radiotherapy. Values of x higher than 3.20 dsb/Gy/DNA unit theoretically should correspond to the highly radio-sensitive patients. Using the experimental results, we have calculated the strength of the test by means of the area under the receiver operator characteristic curves (A(Z)) to determine whether the radiosensitivity assay can discriminate between patients according to their radiation response. The value found (A(Z)=0.675+/-0.072) is indicative of a fair-poor discriminating capacity of the test to identify the patients with higher risk of developing a severe acute reaction during the radiotherapy treatment.     

Peripheral Blood Lymphocytes as In Vitro Model to Evaluate Genomic Instability Caused by Low Dose Radiation

Diagnostic and therapeutic radiation fields are planned so as to reduce side-effects while maximising the dose to site but effects on healthy tissues are inevitable. Radiation causes strand breaks in DNA of exposed cells which can lead to chromosomal aberrations and cause malfunction and cell death. Several researchers have highlighted the damaging effects of high dose radiation but still there is a lacuna in identifying damage due to low dose radiation used for diagnostic purposes. Blood is an easy resource to study genotoxicity and to estimate the effects of radiation. The micronucleus assay and chromosomal aberration can indicate genetic damage and our present aim was to establish these with lymphocytes in an in vitro model to predict the immediate effects low dose radiation. Blood was collected from healthy individuals and divided into 6 groups with increasing radiation dose i.e., 0Gy, 0.10Gy, 0.25Gy, 0.50Gy, 1Gy and 2Gy. The samples were irradiated in duplicates using a LINAC in the radiation oncology department. Standard protocols were applied for chromosomal aberration and micronucleus assays. Metaphases were stained in Giemsa and 200 were scored per sample for the detection of dicentric or acentric forms. For micronuclei detection, 200 metaphases. Giemsa stained binucleate cells per sample were analysed for any abnormality. The micronuclei (MN) frequency was increased in cells exposed to the entire range of doses (0.1- 2Gy) delivered. Controls showed minimal MN formation (2.0%0.05) with triple MN (5.6%2.0) frequency at the lowest dose. MN formation increased exponentially with the radiation dose thereafter with a maximum at 2Gy. Significantly elevated numbers of dicentric chromosomes were also observed, even at doses of 0.1- 0.5Gy, compared to controls, and acentric chromosomes were apparent at 2Gy. In conclusion we can state that lymphocytes can be effectively used to study direct effect of low dose radiation.     

CoCl2诱导缺氧对Eca109细胞细胞周期及放射敏感性的影响

Objective:To investigate the change of the cell cycle,apoptosis and radiosensitivity effect by CoCl2 induced hypoxia in esophageal cancer line Eca109 cells in vitro.Methods:The hypoxia culture model induced by 150 microM CoCl2 was established.The cell cycle and apoptosis were measured with flow cytometry (FCM).The radiosensitivity was analysized with clonogenic assay after irradiation alone or combined with hypoxia in Eca109 cells in vitro.Results:Eca109 cells were treated with 150 microM CoCl2 for 24 h,cell cycle arrest in G0/G1 phase increase and decreasing arrest in S phase with longer of hypoxiac time (0-24 h),the other rate of cell cycle and apoptosis did not change obviously.The G2/M phase block was arrested obviously in radiation alone comparing with the hypoxia plus irradiated group,apoptosis did not occur in Eca109 cell line following irradiation.The DO value and cell surviving fraction of Eca109 cell was 2.48 Gy,2.44 Gy and 97.33%,96.33% in hypoxia and control group,respectively;the Dq value of Eca109 cell was 2.89 Gy,0.52 Gy,the cell surviving fraction after radiation with 4 Gy was 48.3%,21.7% in hypoxia and control group,respectively.The hypoxia decreased the radiosensitivity in esophageal cancer Eca109 cells with clonogenic assay.Conclusion:Hypoxia induced by CoCl2 influences radiosensitivity of Eca109 cell through regulating cellular proliferation rates.     

Chromosomal instability and radiosensitivity in myelodysplastic syndrome cells.

Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoietic stem cells. To investigate whether chromosomal instability and/or DNA repair defects are involved in the development of MDS, we measured the micronucleus (MN) frequency in peripheral blood lymphocytes exposed to various doses of X-rays, using a cytokinesis-block micronucleus assay. The spontaneous MN frequencies in RAEB and RAEB-T patients were significantly higher than those in normal individuals (P = 0.0224, P = 0.008, respectively). Also, the X-ray-induced MN frequencies in RA/RARS, RAEB, and RAEB-T patients were significantly higher than those in normal individuals (P = 0.007, P = 0.003, P = 0.003, respectively, at 2 Gy). In order to elucidate the cause of unusual radiosensitivity, we measured the expression levels of nucleotide excision repair (NER) genes in peripheral blood mononuclear cells using a RT-PCR method. Reduction of NER gene expression was found in only one of 10 patients with low risk MDS, but in four of 11 patients with high risk MDS. Our data suggest that chromosomal instability and DNA repair defects may be involved in the pathophysiology of disease progression of MDS.     

Chromosomal radiosensitivity as a marker of predisposition to common cancers?

We previously found that 40% of breast cancer patients showed enhanced sensitivity to X-ray induced chromosome damage in G(2)lymphocytes and suggested that this might indicate a low penetrance predisposition to breast cancer, for which there is good epidemiological evidence. We have now tested the hypothesis that elevated G(2)radiosensitivity is a marker of such predisposition to other common cancers. We tested patients with colorectal cancer, for which there is also good epidemiological evidence of inherited risk in a substantial proportion of cases, and patients with cancers having a strong environmental aetiology (lung and cervix). We also repeated our study of breast cancer cases and tested patients with chronic diseases other than cancer. The results support our hypothesis, in that 30% (12/37) of colorectal cases showed enhanced sensitivity compared with 9% (6/66) of normal healthy controls (P = 0.01), whereas the proportions of sensitive cervix (11%, 3/27, P = 0.72) and lung cancer cases (23%, 8/35, P = 0.07) were not significantly above normals. We confirmed the enhanced sensitivity of 40% (12/31, P = 0.001) of breast cancer patients and found that patients with non-malignant disease had a normal response in the assay (12%, 4/34, P = 0.73). We suggest that enhanced G(2)chromosomal radiosensitivity is a consequence of inherited defects in the ability of cells to process DNA damage from endogenous or exogenous sources, of a type that is mimicked by ionizing radiation, and that such defects predispose to breast and colorectal cancer.     

The increment of micronucleus frequency in cervical carcinoma during irradiation in vivo and its prognostic value for tumour radiocurability.

A potential usefulness of micronucleus assay for prediction of tumour radiosensitivity has been tested in 64 patients with advanced stage (II B-IV B) cervical carcinoma treated by radiotherapy. The study of cellular radiosensitivity in vitro was conducted in parallel with the study of cellular damage after tumour irradiation in vivo. Radiosensitivity of in vitro cultured primary cells isolated from tumour biopsies taken before radiotherapy was evaluated using cytokinesis-block micronucleus assay. Frequency of micronuclei per binucleated cell (MN/BNC) at 2 Gy was used as a measure of radiosensitivity. Radiation sensitivity in vivo was expressed as per cent increment of micronucleus frequency in cells isolated from biopsy taken after 20 Gy (external irradiation, 10 x 2 Gy) over the pre-treatment spontaneous micronucleus level and was called MN20. Very low correlation (r = 0.324) was observed between micronucleus frequency in vitro and in vivo. Although micronucleus frequency at 2 Gy differed widely between tumours evaluated (mean MN/BNC was 0.224; range 0.08-0.416), no significant correlation was observed between this parameter and clinical outcome. The average increment of micronucleus frequency after 20 Gy amounted to 193% of spontaneous level (range 60-610%) and was independent of spontaneous micronucleation before radiotherapy. In contrast to in vitro results, these from in vivo assay seem to have a predictive value for radiotherapy of cervix cancer. The micronucleus increment in vivo that reached at least 117.5% of pretreatment value (first quartile for MN20 data set) correlated significantly with better tumour local control (P < 0.008) and overall survival (P < 0.045). Our results suggest that evaluation of increment of micronucleus frequency during radiotherapy (after fixed tested dose of 20 Gy) offers a potentially valuable approach to predicting individual radioresponsiveness and may be helpful for individualization of treatment strategy in advanced stage cervical cancer.     

Downregulation of TMPRSS4 Enhances Triple-Negative Breast Cancer Cell Radiosensitivity Through Cell Cycle and Cell Apoptosis Process Impairment

Background: Radioresistance remains a challenge for cancer radiotherapy. The present study aims to investigate the role of TMPRSS4 in triple negative breast cancer (TNBC) cell radiosensitivity. Materials and Methods: After transfection of MDA-MD-468 triple negative breast cancer cells line by using the lentivirus vector, the effect of TMPRSS4 down-regulation on TNBC radiosensitivity was evaluated by using cloning assay and CCK-8 assay. The CCK-8 assay was also used for performing cell proliferation analysis. Western blot was carried out to detect the expression of certain proteins related to cell cycle pathways (cyclin D1), cell apoptosis pathways (Bax, Bcl2, and Caspase3), DNA damage and DNA damage repair (TRF2, Ku80 , ˠH2AX) . The cell cycle and cell apoptosis were also investigated using flow cytometer analysis. Results: TMPRSS4 expression was down-regulated in MDA-MB-468 cells which enhanced MDA-MB-468 cells radiosensitivity. TMPRSS4 silencing also improved IR induced cell proliferation ability reduction and promoted cell arrested at G2/M phase mediated by 6 Gy IR associated with cyclin D1 expression inhibition. Moreover, TMPRSS4 inhibition enhanced TNBC apoptosis induced by 6 Gy IR following by over-expression of (Bax, Caspase3) and down-regulation of Bcl2 as the pro-apoptotic and anti-apoptotic proteins, respectively. Otherwise, TMPRSS4 down-regulation increases  DNA damage induced by 6 Gy IR and delays DNA damage repair respectively illustrated by downregulation of TRF2 and permanent increase of Ku80 and ˠH2AX expression at 1 h and 10 h post-IR. Conclusion: Down-regulation of TMPRSS4 increases triple negative breast cancer cell radiosensitivity and the use of TMPRSS4 inhibitor can be encouraged for improving radiotherapy effectiveness in TNBC radioresistant patients.     

G(2) chromosomal radiosensitivity in Danish survivors of childhood and adolescent cancer and their offspring

In order to investigate the relationship between chromosomal radiosensitivity and early-onset cancer, the G(2) chromosomal radiosensitivity assay was undertaken on a group of 23 Danish survivors of childhood and adolescent cancer, a control group comprising their partners and a group of 38 of their offspring. In addition, the previously reported in-house control group from Westlakes Research Institute (WRI) was extended to 27 individuals. When using the 90th percentile cutoff for the WRI control group, the proportion of individuals with elevated radiosensitivity was 11, 35, 52 and 53% for the WRI control, partner control, cancer survivor and the offspring groups, respectively, with significant differences between the WRI control group and the cancer survivor group (P=0.002) and the offspring group (P<0.001). However, while the comparisons with the WRI control group support an association of chromosomal radiosensitivity with cancer predisposition, when the partner control group was used to define the radiosensitivity cutoff point, no significant differences in radiosensitivity profiles were found between the partner control group and either the cancer survivor group or the offspring group. The failure to distinguish between the G(2) aberration profiles of the apparently normal group of partners and the cancer survivor group suggests that any association with cancer should be viewed with caution, but also raises questions as to the suitability of the partners of cancer survivors to act as an appropriate control group. Heritability of the radiosensitive phenotype was examined by segregation analysis of the Danish families and suggested that 67.3% of the phenotypic variance of G(2) chromosomal radiosensitivity is attributable to a putative major gene locus with dominant effect.