Increased radiosensitivity as an indicator of genes conferring breast cancer susceptibility.

PURPOSE: This paper briefly summarizes the research on increased radiosensitivity in breast cancer patients measured by the micronucleus test (MNT) and its association to genetic variants in DNA repair genes. More preliminary data are presented on the distribution of chromosomes and chromosome fragments in micronuclei (MN) in order to gain more information on clastogenic and aneugenic effects and better understand the phenotype of increased radiosensitivity. MATERIAL AND METHODS: Reports of relevant studies obtained from a search of PubMed and studies referenced in those reports were reviewed. In four patients with high MN frequency (three cancer patients, one control) and four probands with low MN frequency, the presence of chromosome fragments or whole chromosomes in MN was determined by fluorescence in situ hybridization analysis for chromosomes 1, 7, and 17. RESULTS: An increased MN frequency in breast cancer patients compared to controls has consistently been reported with high significance. Higher MN frequencies were observed in 20-50% of breast cancer patients. Chromosomal fragments of chromosome 17, but not of chromosomes 1 and 7 were more frequent in the probands with high MN frequency than in those with low frequency (p = 0.045). CONCLUSION: The MNT detects a cellular phenotype common to a portion of sporadic breast cancer patients. This phenotype is very likely to be genetically determined. For the genetic dissection of breast cancer susceptibility this phenotype may turn out to be more efficient than breast cancer itself. Additional parameters which can be measured simultaneously with the MN frequency may be able to further enhance its usefulness.

Early reduction in the aneuploidy at chromosomes 7 and 8 are significantly correlated with clinical effect in high-dose rate brachytherapy with external beam radiotherapy in localized prostate cancer.

Although reduction in the serum prostate specific antigen (PSA) correlates with clinical outcome for high dose rate Iridium-192 (HDR Ir-192) brachytherapy, it takes a long latency period. We investigated numerical chromosome changes of prostatic cancer during the pre- and post-treatment periods of HDR Ir-192 brachytherapy (and external beam radiotherapy), using fluorescence in situ hybridization (FISH) to clear the effect of treatment in early phase. Transitional changes in the frequency of aneuploidy for chromosomes 7, 8, 10, 12, 16, X, and Y in prostate cancer during the pre- and post-treatment periods were observed. Gains of chromosomes 7, 8 and 12 were noted in the pre-treatment samples (4 out of 12 cases in chromosomes 7 and 8; 1 out of 12 cases in chromosome 12), while a notable reduction in the number of cells with extra copies of these chromosomes was observed in post-treatment specimens. This change appears earlier than the reduction in the value of prostate specific antigen (PSA) and strongly reflects the effect of HDR brachytherapy with external beam radiotherapy in localized prostate cancer. Decrease in the number of cells with high ploidies of chromosomes 7, 8 and 12 at 12 weeks after treatment may predict clinical effects of radiation therapy, which may explain the radiation dependency of localized prostate cancer cells.

Detection of chromosome 2 and chromosome 7 within X-ray- or colchicine-induced micronuclei by fluorescence in situ hybridization.

The occurrence of chromosome 2 and chromosome 7 within micronuclei of binucleated lymphocytes induced by X-rays or colchicine was scored using the whole chromosome painting technique. The observed frequency of involvement in micronucleus formation was compared with the yield that would be expected theoretically, when the random participation of each chromosome is assumed. No difference was observed between the expected and observed inclusion of chromosome 2 or chromosome 7 into micronuclei after X-ray exposure (2.5 Gy). This was also the case for chromosome 2, but not for chromosome 7 after colchicine treatment (0.04/0.06 microgram/ml); chromosome 7 was detected approximately 1.5 times more frequently in micronucleus formation than would be expected from the assumption of a random distribution.

Therapy-related chromosomal changes and cytogenetic heterogeneity in human gliomas.

The karyotypes of 18 primary 'untreated' gliomas, 6 recurrent gliomas treated with radiotherapy and/or chemotherapy and 2 gliomas before and after treatment are described, based on observations using standard cytogenetic techniques. In comparison to the untreated gliomas there were relatively consistent chromosome differences in the treated gliomas, including (1) deletions of the long arm of chromosome 7 with breakpoint at q22, possibly induced by alkylating agents, and (2) numerous single cell abnormalities or unrelated clones of structural abnormalities, presumably induced by radiotherapy.

Noninvolvement of the X chromosome in radiation-induced chromosome translocations in the human lymphoblastoid cell line TK6.

Fluorescence in situ hybridization procedures were used to examine the influence of chromosome locus on the frequency and type of chromosome aberrations induced by 60Co gamma rays in the human lymphoblastoid cell line TK6. Aberrations involving the X chromosome were compared to those involving the similarly sized autosome chromosome 7. When corrected for DNA content, acentric fragments were induced with equal frequency in the X and 7 chromosomes. Dose-dependent increases in chromosomal interchanges involving chromosome 7 were noted and the frequencies of balanced translocations and dicentrics produced were approximately equal. Chromosome interchanges involving the X chromosome were rare and showed no apparent dose dependence. Thus, while chromosomes 7 and X are equally sensitive to the induction of chromosome breaks, the X chromosome is much less likely to interact with autosomes than chromosome 7. The noninvolvement of the X chromosome in translocations with autosomes may reflect a more peripheral and separate location for the X chromosome in the mammalian nucleus.

Rapid metaphase and interphase detection of radiation-induced chromosome aberrations in human lymphocytes by chromosomal suppression in situ hybridization.

Chromosomal in situ suppression (CISS)-hybridization of biotinylated phage DNA-library inserts from sorted human chromosomes was used to decorate chromosomes 1 and 7 specifically from pter to qter and to detect structural aberrations of these chromosomes in irradiated human peripheral lymphocytes. In addition, probe pUC1.77 was used to mark the 1q12 subregion in normal and aberrant chromosomes 1. Low LET radiation (60Co-gamma-rays; 1.17 and 1.33 MeV) of lymphocyte cultures was performed with various doses (D = 0, 2, 4, 8 Gy) 5 h after stimulation with phytohaemagglutinin. Irradiated cells were cultivated for an additional 67 h before Colcemid arrested metaphase spreads were obtained. Aberrations of the specifically stained chromosomes, such as deletions, dicentrics, and rings, were readily scored after in situ hybridization with either the 1q12 specific probe or DNA-library inserts. By the latter approach, translocations of the specifically stained chromosomes could also be reliably assessed. A linear increase of the percentage of specifically stained aberrant chromosomes was observed when plotted as a function of the square of the dose D. A particular advantage of this new approach is provided by the possibility to delineate numerical and structural chromosome aberrations directly in interphase nuclei. These results indicate that cytogenetic monitoring of ionizing radiation may be considerably facilitated by CISS-hybridization.