Impaired DNA repair capacity in skin fibroblasts from various hereditary cancer-prone syndromes.

Host-cell reactivation (HCR) of UV-C-irradiated herpes simplex virus type 1 (HSV-1) has been determined in skin fibroblasts from the following hereditary cancer-prone syndromes: aniridia (AN), dysplastic nevus syndrome (DNS), Von Hippel-Lindau syndrome (VHL), Li-Fraumeni syndrome (LFS) and a family with high incidence of breast and ovarian cancer. Cells from AN, DNS or VHL patients were found to exhibit heterogeneity in HCR. Cells from individuals belonging to an LFS family show reduced HCR in all cases where the cells were derived from persons carrying one mutated p53 allele, whereas cells derived from members with two wild-type alleles show normal HCR. LFS cells with reduced HCR also reveal reduced genome overall repair, and a slower gene-specific repair of the active adenosine deaminase (ADA) gene, but little if any repair of the inactive 754 gene. In the breast/ovarian cancer family, reduced HCR is observed in skin fibroblasts derived from both afflicted and unaffected individuals. In addition, these cells display lower survival after exposure to UV-C and exhibit higher levels of SCEs than those in normal cells. These observations indicate that various hereditary cancer-prone syndromes, carrying mutations in different tumor-suppressor genes, exhibit an unexplained impairment of the capacity to repair UV-damaged DNA.

Detection of aneugenic and clastogenic potential of X-rays, directly and indirectly acting chemicals in human hepatoma (Hep G2) and peripheral blood lymphocytes, using the micronucleus assay and fluorescent in situ hybridization with a DNA centromeric probe.

In human hepatoma (Hep G2) cells and peripheral blood lymphocytes (HPBL) the cytokinesis-blocked micronuclei (MN) and fluorescent in situ hybridization (FISH) assays were applied to study aneugenic and clastogenic potentials of X-rays, directly and indirectly acting chemicals. Induction of MN was studied in vitro following treatment with X-rays, directly acting chemicals, such as methylmeth-anesulphonate (MMS), colchicine (COL), vincristine sulphate (VCS) and vinblastine sulphate (VBS), and indirectly acting agents, such as cyclophosphamide (CP), hexamethylphosphoramide (HMPA), 2-acetylaminofluorene (2-AAF) and 4-acetylaminofluorene (4-AAF). Depending on the presence of the fluorescent signal in the MN following FISH with a human DNA centromeric probe, MN in the binucleated Hep G2 cells and lymphocytes were scored as centromere-positive or centromere-negative, representing an aneugenic and clastogenic event respectively. In the controls approximately 50% of spontaneously occurring MN were centromere-positive. Treatment of human hepatoma cells and HPBL (in vitro) with potent aneugens such as COL, VCS and VBS increased the number of MN in a dose-dependent manner; of these 75-93% were centromere-positive. X-irradiation induced MN in a dose-related manner in binucleated Hep G2 cells and HPBL, of which 33-40% were centromere-positive, which demonstrates the significant aneugenic potentials of X-rays. Strong clastogenic activity was observed with MMS and frequency of centromere-positive MN was low: approximately 20 and 30% for HPBL and Hep G2 cells respectively. In Hep G2 cells significant aneugenic activity was found with indirectly acting promutagens/procarcinogens such as HMPA and 2-AAF, in contrast to CP, which came out as a potent clastogen. The non-carcinogen 4-AAF was not able to induce an increase in the frequency of MN in Hep G2 cells. All indirectly acting chemicals tested came out negative when HPBL were used as targets for DNA damage. The results presented correlate positively with data from in vivo assays and indicate that the Hep G2 cell system is a suitable bioactivation system (in vitro) for evaluating the clastogenic and aneugenic potentials of chemicals which require exogenous metabolic activations in order to exert their mutagenic potential.