Skin fibroblast cell lines derived from non-Hodgkin's-lymphoma (NHL) patients show increased sensitivity to chronic gamma irradiation

A SAS macro for the analysis of cell survival curves

This paper describes a SAS macro for the statistical analyses of cell survival data obtained after radiation treatment using the methods of R.E. Tarone et al. (Mutation Research 111 (1983) 79-96). These analyses are usually required on a routine basis by all biomedical research laboratories involved in cell survival assays generating dose-response curves aimed at characterizing radiosensitive mutant cell strains or individuals whose body cells exhibit enhanced sensitivity to radiation and other genotoxic agents. Statistical methods of linear regression are applied to data from repeated experiments with a cell line/strain and weighted estimates of a common slope and its variance are obtained. The methods are currently implemented in two APL programs. These programs are not easily accessible to most biomedical statisticians and researchers because APL is not a common software tool for statistical analysis. Implementation of these methods in SAS, a widely used commercial software for statistical analysis, is expected to help resolve this issue. We illustrate the application of the macro using an example data set obtained in our laboratory, and hope that other investigators may find it useful in analyzing their data.

Cellular radiosensitivity of patients with papillary thyroid cancer

Cultured skin fibroblasts from patients with papillary (differentiated) thyroid carcinomas were compared to those from healthy subjects, ataxia telangiectasia (AT) homozygotes and AT heterozygotes for colony-forming ability after low dose-rate irradiation, and post-irradiation DNA synthesis as indicated by uptake of [3H]-thymidine. The cells from the cancer patients exhibited enhanced radiosensitivity (intermediate between normal and AT) and less than normal level of radioinduced inhibition of DNA synthesis.

Relationship between DNA damage, rejoining and cell killing by radiation in mammalian cells

The prevailing hypothesis on the mechanism of radiation-induced cell killing identifies the genetic material deoxyribonucleic acid (DNA) as the most important subcellular target at biologically relevant doses. In this review we present new data and summarize the role of the DNA double-strand breaks (dsb) induced by ionizing radiation and DNA dsb rejoining as determinants of cellular radiosensitivity. When cells were irradiated at high dose-rate, two molecular end-points were identified which often correlated with radiosensitivity: (1) the apparent number of DNA dsb induced per Gy per DNA unit and (2) the half-time of the fast component of the DNA dsb rejoining kinetics. These two molecular determinants, not mutually exclusive, may be linked through a common factor such as the conformation of DNA.

Post-irradiation DNA synthesis inhibition and G2 phase delay in radiosensitive body cells from non-Hodgkin's lymphoma patients: an indication of cell cycle defects

In the present study, both post-irradiation DNA synthesis and G2 phase accumulation were analyzed in lymphoblastoid cell lines (LCLs) and fibroblast cell strains derived from (Saudi) patients with non-Hodgkin's lymphoma (NHL), ataxia telangiectasia (AT), AT heterozygotes and normal subjects. A comparison of the percent DNA synthesis inhibition (assayed by 3H-thymidine uptake 30 min after irradiation), and a 24 h post-irradiation G2 phase accumulation determined by flow cytometry placed the AT heterozygotes and the NHL patients in an intermediate position between the normal subjects (with maximum DNA synthesis inhibition and minimum G2 phase accumulation) and the AT homozygotes (with minimum DNA synthesis inhibition and maximum G2 accumulation). The similarity between AT heterozygotes and the NHL patients with respect to the two parameters studied after irradiation was statistically significant. The data indicating a moderate abnormality in the control of cell cycle progression after irradiation in the LCLs and fibroblasts from NHL patients may explain the enhanced cellular and chromosomal radiosensitivity in these patients reported by us earlier. In addition to demonstrating a link between cell cycle abnormality and radiosensitivity as a possible basis for cancer susceptibility, particularly in the NHL patients, the present studies emphasized the usefulness of the assay for 24 h post-irradiation G2 phase accumulation developed by Lavin et al. (1992) in characterizing AT heterozygote-like cell cycle anomaly in cancer patients irrespective of whether they carried the AT gene or any other affecting the cell cycle.

Increased radiosensitivity and radioresistant DNA synthesis in cultured fibroblasts from patients with coronary atherosclerosis

Cultured skin fibroblasts from five patients with atherosclerosis who underwent coronary artery bypass graft surgery were compared with those from one ataxia telangiectasia (AT) homozygote, three AT heterozygotes, and five healthy subjects to determine their sensitivity to gamma radiation as determined by a colony survival assay. Fibroblasts from four of these patients were also compared with those from two AT homozygotes, two AT heterozygotes, and three healthy subjects to determine postirradiation [3H]thymidine incorporation, indicating the levels of radioresistant DNA synthesis (RDS). On the basis of colony survival assay, after long-term irradiation (at low dose rate, ie, 0.007 Gy/min), fibroblasts from all five patients with atherosclerosis exhibited radiosensitivity that was intermediate between that of the healthy subjects and that of patients with the known radiosensitive syndrome AT. However, there was a considerable interstrain difference in the radiosensitivity of fibroblasts from patients with atherosclerosis, with their mean D10 values (radiation dose resulting in 10% cell survival) varying between 2.3 and 6.2 Gy, whereas the mean D10 values for the cells from the AT homozygote, AT heterozygotes, and healthy subjects were 2.0, 3.8, and 9.0 Gy, respectively. One of the patients with atherosclerosis showed cellular radiosensitivity quite similar to that of the AT homozygote, up to 2% to 10% of survival levels after short- (at a dose rate of 8 Gy/min) and long-term irradiation, respectively. The results of [3H]thymidine incorporation showed an AT heterozygote-like RDS in fibroblasts from patients with atherosclerosis that appeared to be intermediate between that of AT homozygotes and that of healthy subjects, suggesting a partial deregulation of cell cycle in the patients with atherosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular radiosensitivity of patients with different types of neurofibromatosis

Skin fibroblast cell strains were developed from nine Saudi patients with different types of neurofibromatosis (NF) and nine healthy subjects (controls), and their radiosensitivity was compared following chronic exposure to gamma-radiation at a dose rate of 0.0076 Gy/min (1 Gy = 100 rads). Cells from both normal appearing skin and café-au-lait spots of the different NF patients (7 out of 9) clearly showed increased radiosensitivity, with D10 (dose resulting in 10% survival) values of 2.0-4.4 Gy for the former and 3.0-4.8 Gy for the latter, compared to the normal controls (with D10 values of 6.1-10.6 Gy). These data provide further evidence of an association of enhanced cellular sensitivity to chronic irradiation with NF regardless of the classes they belong to. Hypersensitivity to specific carcinogens may, thus, be a factor responsible for the increased propensity to cancer in these patients.

Chronic gamma-irradiation results in increased cell killing and chromosomal aberration with specific breakpoints in fibroblast cell strains derived from non-Hodgkin's lymphoma patients

Cultured skin fibroblast cells from 6 patients with non-Hodgkin's lymphoma (NHL) and 2 clinically normal subjects were compared for cell survival and chromosomal aberration after chronic gamma-irradiation. Fibroblasts from an ataxia telangiectasia (AT) homozygote and an AT heterozygote were used as positive controls. Following irradiation, fibroblasts from all 6 NHL patients showed an increase in both cell death and chromosomal aberration (breaks and rearrangements) compared to the normal subjects. The difference in the frequency of chromosomal aberration between the normals and the NHL patients remained virtually unchanged over a period of 24-72 h post irradiation incubation of the cells. Cell cycle analysis by flow cytometry carried out in 1 normal and 1 NHL fibroblast cell strain showed that more cells representing the NHL patient were in G2/M phase compared to the normal at various times of cytogenetic analysis. While the AT homozygote appeared to be the most radiosensitive, the AT heterozygote showed a slightly higher incidence of cell death and chromosomal aberration than the normals. The cellular and chromosomal radiosensitivity of fibroblast cell lines from the NHL patients differed slightly from that of the AT heterozygote but clearly occupied an intermediate position between the AT homozygote and the normal subjects. Cells from 3 of the NHL patients showed radiation-induced specific chromosomal breaks involving chromosomes 1, 2, 6, 8, 10 and 11 which correspond to known fragile sites. Such breakpoints associated with increased radiosensitivity may be indicative of predisposition to malignancy in the patients studied.

Increased radiosensitivity of cell lines derived from a Down's syndrome patient with ocular telangiectasia

Studies on radiosensitivity of cells from Down's syndrome (DS) patients were stimulated by the observation of their increased susceptibility to leukemia. While lymphocytes from DS patients were found to consistently show increased chromosomal aberrations after exposure to ionizing radiation, conflicting reports have been published on the radiosensitivity of fibroblasts and lymphoblastoid cell lines (LCL) derived from these patients. In the present study, cultured skin fibroblast lines developed from a DS patient with ocular telangiectasia and five normal subjects were compared for both cell killing and chromosomal aberrations (breaks, translocations, inversions, dicentrics, and rings) after low dose-rate gamma-irradiation. The LCLs developed from the patient and two normal persons were also compared for chromosomal radiosensitivity using the same irradiation protocol. A comparison of the D10 (radiation dose resulting in 10% survival) values estimated from the survival curves and the frequencies of induced chromosome aberrations in different cell lines showed that the DS cells were more radiosensitive than the respective controls. The increased cellular radiosensitivity of the DS patient reported here could be due to a combination of genetic factors (DS plus a gene for hypersensitivity to radiation) and, thus, may not be representative of all DS patients. Alternatively, the use of low dose-rate irradiation could be a factor in revealing the radiosensitivity of DS fibroblasts in general.

DNA double strand breaks in fibroblast cell lines, from non-Hodgkin's lymphoma patients, showing increased sensitivity to chronic gamma irradiation

Cultured skin fibroblast cell lines from two non-Hodgkin's lymphoma patients (NHL) and a normal subject were studied for cell killing, chromosomal aberrations (breaks, translocations, dicentrics and rings) and DNA double strand breaks (dsbs) following chronic gamma irradiation. Compared to the cell line from the normal donor, the NHL patients' fibroblasts showed enhanced radiosensitivity for both cell survival and chromosomal aberrations. While spontaneous breaks were observed in both normal and patients' cells, spontaneous translocations and radiation-induced dicentrics and rings were found only in the latter. Radiation-induced DNA double-strand breaks (dsb) were determined by CHEF electrophoresis. After chronic irradiation with gamma rays the fraction of residual dsb was significantly increased from 1.4% in controls to 1.9% in the NHL cell lines. These data, thus, suggest that the cellular and chromosomal sensitivity to chronic irradiation observed in NHL patients may be due to a deficiency in the repair of a small fraction of DNA double strand breaks.