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Fanconi Anaemia (FA) is an autosomal recessive disorder characterised by defects in DNA repair, associated with chromosomal instability and cellular hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC). The FA repair pathway involves complex DNA repair mechanisms crucial for genomic stability. Deficiencies in DNA repair genes give rise to chromosomal radiosensitivity. FA patients have shown increased clinical radiosensitivity by exhibiting adverse normal tissue side-effects. The study aimed to investigate chromosomal radiosensitivity of homozygous and heterozygous carriers of FA mutations using three micronucleus (MN) assays. The G0 and S/G2 MN assays are cytogenetic assays to evaluate DNA damage induced by ionising radiation in different phases of the cell cycle. The MMC MN assay detects DNA damage induced by a crosslinking agent in the G0 phase. Patients with a clinical diagnosis of FA and their parents were screened for the complete coding region of 20 FA genes. Blood samples of all FA patients and parents were exposed to ionising radiation of 2 and 4 Gy. Chromosomal radiosensitivity was evaluated in the G0 and S/G2 phase. Most of our patients were homozygous for the founder mutation FANCG c.637_643delTACCGCC; p.(Tyr213Lysfs*6) while one patient was compound heterozygous for FANCG c.637_643delTACCGCC and FANCG c.1379G > A, p.(Gly460Asp), a novel missense mutation. Another patient was compound heterozygous for two deleterious FANCA mutations. In FA patients, the G0- and S/G2-MN assays show significantly increased chromosomal radiosensitivity and genomic instability. Moreover, chromosomal damage was significantly elevated in MMC treated FA cells. We also observed an increase in chromosomal radiosensitivity and genomic instability in the parents using 3 assays. The effect was significant using the MMC MN assay. The MMC MN assay is advantageous as it is less labour intense, time effective and has potential as a reliable alternative method for detecting FA patients from parents and controls. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Comparing the chromosomal radiosensitivity of prostate cancer patients with that of healthy donors. Materials and methods: The study was performed on 81 prostate cancer patients characterised by a clinical stage of predominantly pT2c or pT3a and a median age of 67years. As healthy donors 60 male monozygotic twin pairs were recruited with a median age of 28years. Chromosomal radiosensitivity was measured using both G0- and G2-assay. Results: No difference between healthy donors and prostate cancer patients was detected concerning G0-radiosensitivity, since medians were similar (Hodges–Lehmann estimate: −0.05, 95% CI: −0.18–0.08, p =0.4167). However, a pronounced difference was determined for G2-radiosensitivity with prostate cancer patients showing a significantly higher sensitivity compared to healthy donors (Hodges–Lehmann estimate: −0.41, 95% CI: −0.53 to −0.30, p =1.75−9). Using the 90% quantile of G2-radiosensitivity in healthy donors as a threshold for discrimination the fraction of prostate cancer patients with elevated radiosensitivity increased to 49%. Conclusion: G2-, but not G0-radiosensitivity is a promising marker for predisposition of prostate cancer. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Purpose: To examine the association of polymorphisms in XRCC1 (194Arg/Trp, 280Arg/His, 399Arg/Gln, 632Gln/Gln), XRCC3 (5′ UTR 4.541A>G, IVS5-14 17.893A>G, 241Thr/Met), and OGG1 (326Ser/Cys) with the development of late radiotherapy (RT) reactions and to assess the correlation between in vitro chromosomal radiosensitivity and clinical radiosensitivity. Methods and Materials: Sixty-two women with cervical or endometrial cancer treated with RT were included in the study. According to the Common Terminology Criteria for Adverse Events, version 3.0, scale, 22 patients showed late adverse RT reactions. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays were performed to examine polymorphic sites, the G2 assay was used to measure chromosomal radiosensitivity, and patient groups were compared using actuarial methods. Results: The XRCC3 IVS5-14 polymorphic allele was significantly associated with the risk of developing late RT reactions (odds ratio 3.98, p = 0.025), and the XRCC1 codon 194 variant showed a significant protective effect (p = 0.028). Patients with three or more risk alleles in XRCC1 and XRCC3 had a significantly increased risk of developing normal tissue reactions (odds ratio 10.10, p = 0.001). The mean number of chromatid breaks per cell was significantly greater in patients with normal tissue reactions than in patients with no reactions (1.16 and 1.34, respectively; p = 0.002). Patients with high chromosomal radiosensitivity showed a 9.2-fold greater annual risk of complications than patients with intermediate chromosomal radiosensitivity. Combining the G2 analysis with the risk allele model allowed us to identify 23% of the patients with late normal tissue reactions, without false-positive results. Conclusion: The results of the present study showed that clinical radiosensitivity is associated with an enhanced G2 chromosomal radiosensitivity and is significantly associated with a combination of different polymorphisms in DNA repair genes. [Copyright &y& Elsevier]

The frequency, distribution pattern and localisation of gamma radiation-induced break points on the chromosomes of patients with various inherited metabolic disorders were studied to detect: (i) whether the break point distribution following irradiation is random and proportional to the length or the DNA content of the chromosome, or non-proportionally distributed on their length and at times clustering to form hot spots on certain region of the chromosomes; and (ii) to find whether there exists a syndrome-related chromosome-specific pattern of radiation-induced break points. Lymphocyte cultures from patients of haemophilia, ichthyosis, Duchenne muscular dystrophy, retinitis pigmentosa and α-thalassemia, whose defective gene loci were located by DNA probe method, were subjected to 3 Gy of gamma radiation at G0. The chromosomal break point analysis was carried out on all the 23 types of chromosomes (excluding Y chromosome) using G banding and FISH painting. The exact location of the break points on G-banded chromosomes was identified using a semi-automated microscope densitometer system (Leitz MPV2). In normal individuals in all the chromosomes except the chromosome 1, a random distribution of break points proportional to their length based on their DNA content was observed. However, in all the syndromes studied a mixture of hypersensitive chromosomes with a non-random distribution pattern of chromosomal break points invariably clustering to form hot spots, and chromosomes with random distribution of break points proportional to their length were observed. The hypersensitive chromosomes and their hot spots were syndrome-specific. [Copyright &y& Elsevier]