[Induced acute non-lymphoblastic leukemia and prognostic significance of cytogenetic abnormalities: trisomy in chromosome 8, inv(16)(p13q22), and t(8;21)(q22;q22)].

3 patients with secondary acute non-lymphoblastic leucosis have been observed. The cytogenetic analysis revealed pathologic karyotypes: 46, XY,+8, t(8;21), inv 16. Two patients have been found with typical markers of damaged chromosome of radiation origion. Insensibility of blastic cells to cytostatic therapy was typical for the patients.

The radiation sensitivity of human chromosomes 2, 8 and 14 in peripheral blood lymphocytes of seven donors.

PURPOSE: To investigate if deviations from DNA-proportional distribution of radiation-induced chromosomal aberrations are individually variable. MATERIALS AND METHODS: Peripheral blood lymphocytes were collected from seven healthy donors and exposed to different doses of gamma rays. Chromosomes 2, 8 and 14 were painted in different colors and aberrations scored with the help of an image-analysis system. RESULTS: Chromosome 2 was generally less sensitive than expected on the basis of DNA-proportional distribution and the extent of inter-donor variability was minimal. A higher than expected frequency of aberrations was found in chromosome 14 of five donors, while a higher than expected frequency of aberrations was found in chromosome 8 of two donors. CONCLUSIONS: Inter-donor variability may explain some of the controversies regarding the inter-chromosomal distribution of radiation-induced aberrations.

Ionizing radiation-induced instant pairing of heterochromatin of homologous chromosomes in human cells.

Using fluorescence in situ hybridization with human band-specific DNA probes we examined the effect of ionizing radiation on the intra-nuclear localization of the heterochromatic region 9q12-->q13 and the euchromatic region 8p11.2 of similar sized chromosomes 9 and 8 respectively in confluent (G1) primary human fibroblasts. Microscopic analysis of the interphase nuclei revealed colocalization of the homologous heterochromatic regions from chromosome 9 in a proportion of cells directly after exposure to 4 Gy X-rays. The percentage of cells with paired chromosomes 9 gradually decreased to control levels during a period of one hour. No significant changes in localization were observed for chromosome 8. Using 2-D image analysis, radial and inter-homologue distances were measured for both chromosome bands. In unexposed cells, a random distribution of the chromosomes over the interphase nucleus was found. Directly after irradiation, the average inter-homologue distance decreased for chromosome 9 without alterations in radial distribution. The percentage of cells with inter-homologue distance <3 micro m increased from 11% in control cells to 25% in irradiated cells. In contrast, irradiation did not result in significant changes in the inter-homologue distance for chromosome 8. Colocalization of the heterochromatic regions of homologous chromosomes 9 was not observed in cells irradiated on ice. This observation, together with the time dependency of the colocalization, suggests an underlying active cellular process. The biological relevance of the observed homologous pairing remains unclear. It might be related to a homology dependent repair process of ionizing radiation induced DNA damage that is specific for heterochromatin. However, also other more general cellular responses to radiation-induced stress or change in chromatin organization might be responsible for the observed pairing of heterochromatic regions.

[Comparison of cytogenetic response of human lymphocytes to in vivo and in vitro exposure to low-dose gamma rays. Translocations and dicentrics detected by the FISH technique]. / Sravnenie tsitogeneticheskoi reaktsii limfotsitov cheloveka na obluchenie v malykh dozakh gamma-izlucheniia in vivo i in vitro. Translokatsii i ditsentriki, opredeliaemye FISH-metodom.

On peripheral lymphocytes of 5 cancer patients undergone wholebody therapeutic irradiation (at daily dose of 10 cGy up to total dose 50 cGy of 60Co gamma-rays) the dose response of unstable and stable chromosomal exchanges detected by FISH was compared with the dose response of the some aberrations in lymphocytes irradiated in vitro. The dose response fitted well to linear function. For dicentrics the lower slope of dose-response curve was found for in vivo irradiated lymphocytes as compared to the dose-response curve obtained for in vitro irradiated lymphocytes of the same patients. No difference between in vivo and in vitro irradiation of lymphocytes was found for translocations. The frequency of translocations increased faster with the dose than the frequency of dicentrics only in lymphocytes irradiated in vivo.

Accurate detection of true incomplete exchanges in human lymphocytes exposed to neutron radiation using chromosome painting in combination with a telomeric PNA probe.

PURPOSE: To determine the frequency of true incomplete chromosome exchanges in human lymphocytes after exposure to high-LET neutrons using chromosome painting in combination with centromeric and telomeric probes in one FISH assay. MATERIALS AND METHODS: Human lymphocytes were exposed in vitro to 1 MeV neutrons at a dose of 1 Gy (dose-rate 0.1Gy x min(-1)). Chromosome aberrations were analysed in the first mitosis after irradiation using a FISH technique that combined whole chromosome-specific DNA probes (for chromosomes 4 and 8), human pan-centromeric DNA and telomeric PNA probes. RESULTS: The frequency of true incomplete exchanges induced by 1 MeV neutron irradiation was <5% in chromosomes 4 and 8. Comparison of the frequency of true incompleteness obtained in the present experiment with a previous study that used 4 Gy X-rays showed no striking differences between X-rays and neutrons in incomplete exchange patterns but differences in the spectrum of induced aberrations were detected. Simple exchanges were more frequent with X-rays, whereas complex types were significantly commoner following neutron irradiation (41 and 23% respectively). Differences were also found for complex rearrangements: both the number of these and their complexity increased after neutron-irradiation. CONCLUSION: The combination of chromosome painting and the detection of centromeres and telomeres enable unequivocal discrimination between incomplete and complete exchanges. The application of telomeric probes to analyse chromosome aberrations has demonstrated that true incompleteness is a rare event (approximately 5%) following exposure to high-(neutron) as well as to low-(X-rays) LET radiation.

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.

Translocation frequencies measured in patients one year after radioactive iodine therapy for thyrotoxicosis.

PURPOSE: To investigate the incidence of translocations induced by iodine-131 therapy in thyrotoxicosis patients 1 year after the administration of the radiolabelled compound. MATERIALS AND METHODS: Tricolour FISH with whole-chromosome-specific probes for chromosomes 2, 4 and 8 was used for scoring translocations. From the genomic translocation frequencies, derived using the Lucas formula, equivalent whole-body doses were calculated, based on the in vitro (60)Co gamma-ray dose-response curve. RESULTS: A total of 101 translocations were observed in 4864 metaphases, 63% being of the two-way type. In the control group used for obtaining dose-response data, nine translocations were observed in 5278 metaphases, 55% being two-way translocations. No correlation was found between the observed frequency of translocations and administered radioactivity. Using the in vitro dose-response, an estimated average dose for the group of nine patients of 0.79 +/- 0.22Gy was obtained. Compared with frequencies following the assumption that the involvement of a particular chromosome in a two-break exchange-type aberration is proportional to its DNA content, chromosome 4 was more frequently involved and chromosomes 2 and 8 less frequently involved in chromosomal rearrangements. CONCLUSION: This study shows that (131)I therapy for thyrotoxicosis patients induced translocations, especially in chromosome 4, which could be detected 1 year after the administration of the radiolabelled compound.

Localization of tumor suppressor gene candidates by cytogenetic and short tandem repeat analyses in tumorigenic human bronchial epithelial cells.

Radon exposure is associated with increased risk for bronchogenic carcinoma. Mutagenesis analyses have revealed that radon induces mostly multi-locus chromosome deletions. Based on these findings, it was hypothesized that deletion analysis of multiple radon-induced malignant transformants would reveal common mutations in chromosomal regions containing tumor suppressor genes responsible for malignant transformation. This hypothesis was supported by a previous study in which tumorigenic derivatives of the human papillomavirus 18-immortalized human bronchial epithelial cell line BEP2D were established following irradiation with 30 cGy of high linear energy transfer radon-simulated alpha-particles. Herein, we describe the analyses of 10 additional tumorigenic derivative cell lines resulting from the irradiation of five additional independent BEP2D populations. The new transformants have common cytogenetic changes, including the loss of chromosome (ch)Y, one of three copies of ch8, one of two copies of ch11p15-pter and one of three copies of ch14. These changes are the same as those reported previously. Analysis of PCR-amplified short tandem repeats of informative loci confirmed the loss of heterozygosity (LOH) at 12 loci spanning the length of ch8 in cell lines from four of the total of eight irradiation treatments to date and the loss of chY in all cell lines (8 of 8). LOH analysis with a total of 17 informative loci confirmed loss on ch14 in transformants from seven of eight irradiation treatments and indicated a 0.5-1.7 cM region of common involvement centered around locus D14S306. No LOH was detected at any of the informative loci on ch11. The overall results support our stated hypothesis. Further studies are currently in progress to determine whether the ch8 and ch14 regions contain genes with tumor suppressor function in bronchial epithelial cells.

A cell line selected for resistance to ionizing radiation exhibits cross resistance to other genotoxic agents and a mutator phenotype for loss of heterozygosity events.

An ionizing radiation resistant derivative was obtained from the mouse P19H22 (aprt hemizygote) embryonal carcinoma cell line by repeated exposure to 137Cs gamma radiation. Ionizing radiation resistance in the 6Gy-R cell line was not correlated with a failure to undergo cell cycle arrest or a loss of the p53 response after exposure to 137Cs gamma radiation. Moreover, the cells did not display increased resistance to bleomycin, a double strand break inducing agent. However, the cells did display increased resistance to ultraviolet radiation, ethyl methanesulfonate, and 95% oxygen. A mutational analysis demonstrated a > 700 fold-fold increase in the frequency of aprt mutants for the 6Gy-R cells, but no change in the frequency of hprt or dhfr mutants. A molecular analysis suggested that the aprt mutations in the 6Gy-R cells arose by recombinational events. A possible association between radiation resistance, DNA repair, and a mutator phenotype for large-scale mutational events is discussed.

A panel of radiation hybrids for human chromosome 8.

We have developed a panel of radiation hybrids containing fragments of chromosome 8 as the only human material. The human chromosome content of each cell line was determined relative to an ordered map of sequence tagged sites (STSs) specific to chromosome 8. Between one and four fragments of chromosome 8 were identified in each cell line, with an average of 25% of the STSs retained in each line. Subclones of one radiation hybrid were examined to determine whether all cells within a line are homogeneous with respect to chromosome 8 sequence content. There was considerable variability between subclones, with retention rates for individual STSs ranging from 5 to 100% in different clones. Furthermore, a gradient of retention of sequences along the length of one large chromosome fragment was found, suggesting that sequence loss involved deletions from one end of the fragment at early stages in the establishment of the cell line. We have also made use of the radiation hybrids to develop novel sequence tagged sites for the pericentromeric region of chromosome 8.

Radiation-induced damage, repair and exchange formation in different chromosomes of human fibroblasts determined by fluorescence in situ hybridization.

We have used fluorescence in situ hybridization with whole-chromosome probes for human chromosomes 1, 4, 8 and 13 to investigate the extent to which the induction of damage and its repair after exposure to ionizing radiation is distributed randomly among these chromosomes. All the studies were performed with AG1522 human fibroblasts irradiated with 6 Gy and maintained in a nondividing state for at least 6 h after irradiation except for the measurements of initial damage. The extent of initial damage was determined by fusion of the cells immediately after irradiation with metaphase HeLa cells to obtain premature chromosome condensation (PCC). Breaks and exchanges were also scored by PCC 24 h after irradiation and in metaphase spreads at the first division after irradiation. The data obtained were consistent with random breakage and repair in these chromosomes. Comparing PCC 24 h after irradiation with first metaphase, there was a deficit in aberrations at metaphase, particularly in unrejoined breaks, implying loss or slowing of cells containing aberrations prior to the first division. An analysis of dicentrics and translocations in chromosome 4 at first and in subsequent divisions showed that there was an equal number of dicentrics and translocations at first metaphase with loss of dicentrics, but no loss of translocations in subsequent divisions. These data are supportive of the hypothesis tht the total number of chromosome aberrations in cells can be estimated from a single chromosome pair.