Features of the radiosensitivity of cells from ataxia-telangiectasia patients]

Cell survival, single and double DNA strand breaks formation and removal, spontaneous and induced chromosome aberrations and sister chromatid exchange (SCE) levels in gamma-irradiated cells of patients with ataxia-telangiectasia (AT) were studied. Except SCE all of the above indexes of AT cells sensitivity, were higher, than in normal human cells, but lower, than it is commonly characteristic of AT cells in literature. A conclusion is that the analysed AT cells belong to the AT-variant form. Possible mechanisms of high radiosensitivity of AT cells, accompanied by radioresistance of DNA replication, are discussed. The authors suppose that the DNA repair defect in AT cells is not primary.     

Noonan phenotype in the basal cell nevus syndrome.

In this report we present a three-generation family in which five members present the basal cell nevus syndrome. In three of them a Noonan phenotype was present. The basal cell nervus syndrome is another example of a neural crest dysplasia associated with a Noonan-like phenotype. This observation supports the theory that the autosomal dominant mutation causing the neural crest dysplasia may lead to a Noonan-like phenotype.     

Gorlin's syndrome,or nevoid basal cell carcinoma syndrome.

Gorlin''s syndrome is a condition inherited in an autosomal dominant fashion. It involves many organs, but principally affects the skin, skeleton, and endocrine and nervous systems. The most common features are multiple nervi and basal cell carcinomas of the skin, benign jaw cysts, dyskeratotic pits in the palms and soles, rib and vertebral abnormalities, brachymetacarpalism, and calcification of the falx cerebri. In 14 patients, 4 of whom belonged to one family, the age at the time of diagnosis ranged from 11 to 63 years. Ten patients are alive, but five are severely disfigured by carcinomas. Two patients died of complications resulting from uncontrolled tumours, and two died of other cancers. New skin tumours constantly develop; small ones can be excised, but large ones require extensive surgery with or without radiotherapy.     

Increased radiosensitivity in cells of two human cell lines treated with bystander medium from irradiated repair-deficient cells

Radiation-induced bystander factors have been shown to be more toxic if they are from medium harvested from irradiated repair-deficient cells. The aim of this study was to test the hypothesis that the radiosensitivity of repair-proficient cells can be increased by exposing them to medium-borne factors harvested from sensitive cells and vice versa. Cells from a mismatch repair (MMR)-deficient cell line (Raji 10) with a sensitive response to radiation or the wild-type parent cell line were irradiated to 0.5 Gy gamma rays and then monitored for growth rate in their own medium or in the alternative conditioned medium. In other experiments, cells or conditioned medium were added to reporter cells (HPV-G, which are relatively sensitive keratinocytes, or highly radioresistant HT29 cells). The subsequent responses of the two cell lines to a 0.5-Gy dose of (60)Co gamma rays were measured. The results show that prior exposure of resistant cells to medium from irradiated sensitive cells reduced the clonogenic survival of the subsequently irradiated resistant cells. The reverse is also true. Measurement of the apoptosis index and BCL2 expression confirmed that the harvested medium was capable of modulating apoptosis after irradiation. This may have important applications in tumor therapy and also in the understanding of mechanisms involved in induction of adaptive responses.     

The radiosensitivity of the chromosomes of the cells of human squamous cell carcinoma cell lines.

Measurement of the radiation sensitivity of chromosomes was used to address the influence of cell cycle distribution and of DNA content and ploidy on radiation responses in seven human squamous cell carcinoma cell lines. The cell lines varied about twofold in DNA content and chromosome number, and the X-ray sensitivities (D0) of the lines ranged from 1.1 to 2.7 Gy. The more resistant cell lines (D0 greater than 1.8 Gy) had faster growth rates and larger proportions of cells in S phase in asynchronous cultures. Aberration frequencies were measured in cells irradiated in G1 and G2 phase. The more resistant lines had fewer induced aberrations in both phases than did sensitive lines, implying that they were more resistant to radiation in both of these cell cycle phases. Therefore, while the larger S-phase population seen in the resistant cell lines probably contributes to the resistant phenotype, it cannot explain all of the intrinsic differences in radiation sensitivity. There was no relationship between DNA content and radiation sensitivity as measured by the cell survival assay or the induction of chromosome aberrations, although cells with larger DNA contents tended to have more chromosome damage per cell at equitoxic doses.     

Localization of the gene for the nevoid basal cell carcinoma syndrome.

The nevoid basal cell carcinoma syndrome (NBCC) is an autosomal dominant multisystem disorder characterized by multiple basal cell carcinomas, jaw cysts, pits of the palms and/or soles, ectopic calcification, and skeletal malformations. The NBCC gene has recently been mapped to chromosome 9q22.3-9q31. In order to further define the region containing the NBCC gene, we have analyzed 137 individuals from eight families for linkage, using 11 markers from the region. Eight markers showed statistically significant evidence for linkage to NBCC. Three markers (D9S180, ALDOB, and D9S173) showed no definite recombination with the disease locus. All families showed some evidence for linkage to markers in this region. On the basis of the inspection of individual recombinants and previously published information about map location, we suggest the following order for the markers: D9S119-D9S12-D9S197-D9S196-(NBCC,D9S180 -D9S173,ALDOB)-D9S109- D9S127-(D9S53,D9S29). We are currently developing YAC contigs for the most closely linked markers, to further refine the location of the NBCC gene.     

The influence of cell cycle kinetics on the radiosensitivity of Down's syndrome lymphocytes

In agreement with previous work, [60Co]gamma-irradiation shortly after phytohemagglutinin (PHA) stimulation, induces higher frequencies of chromosomal aberrations in trisomy 21 lymphocytes compared to normal controls. However, equal frequencies of chromatid aberrations are induced in fully-stimulated trisomy 21 and normal lymphocytes by irradiation during G2. We have observed that trisomic lymphocytes respond more rapidly to PHA stimulation than normal lymphocytes. Furthermore, we have observed that chromosomal radiosensitivity increases as a function of time after PHA stimulation in normal lymphocytes. When normal lymphocytes are irradiated 8 h after PHA stimulation, the frequencies of chromosomal aberrations induced are comparable to those induced in trisomy 21 lymphocytes irradiated 30 min after PHA stimulation.     

Studies on the radiosensitivity of the function of the Golgi complex.

The uptake of 3H-glucosamine into primary human-embryo fibroblasts and into the Golgi-rich fraction isolated from liver of mice labelled in vivo was studied, after various doses of X-radiation, by autoradiography and biochemical methods. A dose of 90 rad resulted in an increased precursor uptake in interphase cells at 24 hours and in mitotic cells at 48 hours after irradiation; 226 rad had virtually no effect on the grain counts of interphase cells, but reduced the labelling of mitotic forms. The characteristic intracellular localization of the grains were not influenced by these doses. Although no immediate radiation-induced reaction could be observed in liver cells either, significant stimulation of the 3H-glucosamine incorporation was measured in isolated Golgi-rich fractions 24 hours after whole-body irradiation with 90, 450, or 905 rad. This phenomenon is discussed as a part of the somatic regeneration of membrane structures.     

Study on the variation in X-ray sensitivity of human diploid skin fibroblasts. Normal radiosensitivity of cells derived from patients with Huntington's disease

9 cell strains derived from patients with Huntington's disease and 9 from age- and sex-matched controls were investigated for X-ray sensitivity. No differences in radiosensitivity were observed for the two groups. The two groups taken together reveal a dependence of radiosensitivity on intrinsic cloning efficiency which in turn correlates with donor age. A difference in radiosensitivity between males and females is also indicated although at the borderline of significance. As a parameter for radiosensitivity the dose needed to obtain 0.1% survival appears superior to the Do.     

Isolation of mouse mammary epithelial progenitor cells with basal characteristics from the Comma-Dbeta cell line

A mouse mammary epithelial cell line with morphogenetic properties in vivo, Comma-Dbeta, was used to isolate and to characterize mammary progenitor cells. We found that a homogeneous cell population expressing high surface levels of stem cell antigen 1 (Sca-1) was able to give rise in vivo to ductal and alveolar structures comprising luminal secretory and basal myoepithelial cells. Unlike the Sca-1(high), the Sca-1(neg/low) cell population displayed a reduced morphogenetic potential. The Sca-1(high) cells presented moderate CD24, high CD44 and alpha6 integrin surface levels, expressed basal cell markers p63, keratins 5 and 14, but no luminal and myoepithelial lineage markers. In culture, the Sca-1(high) cells generated identical daughter cells that retained their in vivo developmental potential, indicating that these cells were maintained by self-renewal. Plated at clonogenic density in Matrigel, Sca-1(high) cells formed spheroids that included luminal and myoepithelial cells. Thus, the isolated Sca-1(high) basal cells possess several features of stem/progenitor cells, including specific markers, self-renewal capacity, and the ability to generate the two major mammary lineages, luminal and myoepithelial. These data provide evidence for the existence of basal-type mouse mammary progenitors able to participate in the morphogenetic processes characteristic of mammary gland development.     

Analysis of mutation in exon 17 of PTCH in patients with nevoid basal cell carcinoma syndrome

Abnormalities in sonic hedgehog (SHH) signaling pathway components are major contributing factors in the development of nevoid basal cell carcinoma syndromes (NBCCS) that include SHH, PTCH, SMO and GLI. The novel patched homologue (PTCH) mutation and clinical manifestations with NBCCS links PTCH haplosufficiency and aberrant activation of the sonic hedgehog/Patched/smoothened pathway. To investigate further the molecular genetics of NBCCS, we performed mutation analysis of PTCH gene in a family case with five affected members. These clinical manifestations might be associated with a novel constitutional mutation of the PTCH gene, 3146A → T (1049N → I), in exon 17. The analyzed results of tumor tissue show a high expression of GLI. Our findings suggested that the mutation of 3146A → T may be the cause of high expression of GLI and permit SMO to transmit signal to the nucleus through SHH/PTCH/SMO pathway.