Silvana Andrea Mourón

DNA damage by cadmium and arsenic salts assessed by the single cell gel electrophoresis assay

Human exposure to metals is frequent due to their ubiquity, wide use in industry, and environmental persistence. Direct and indirect genotoxic effects of cadmium (Cd) and arsenic (As) were reported. However, the mechanisms of induction of genetic damage are not well known. The aim of the present work was to evaluate the degree of damage induced by Cd and As salts in a human lung fibroblasts cell line using the single cell gel electrophoresis assay (SCGE). MRC-5 cells were treated with cadmium chloride (CdCl(2)), cadmium sulfate (CdSO(4)), sodium arsenite (NaAsO(2)) and cacodylic acid (C(2)H(7)AsO(2)). A significant dose-dependent increment in the extent of DNA migration as well as in the percentage of cells with tails was observed (P<0.001) after treatment with CdSO(4) and NaAsO(2). Treatment with CdCl(2) induced a relatively low level of DNA strand breaks in comparison with that induced by CdSO(4). The increase migration observed with the three compounds could be originated either by the direct induction of DNA lesions or by the inhibition of excision repair mechanisms. On the other hand, cells treated with C(2)H(7)AsO(2) showed a decrease in the migration length with the three doses employed (P<0.001). The decrease in the rate of DNA migration could be a consequence of the induction of DNA cross-links by organic arsenicals.Cd and As salts induced DNA damage in fibroblast cells, detected as DNA migration in the single cell gel (SCG) assay. The distribution of DNA migration among cells as a function of dose revealed that the majority of exposed cells showed more DNA damage than cells obtained from control cultures. The potential for human exposure to both metals has been increased over the years due to the increment in their use. For this reason, elucidation of carcinogenic mechanisms is very important.

Detection of c-erbB-2 Gene Amplification in Cervical Scrapes Positive for Human Papillomavirus (HPV)

c-erbB-2 gene amplification has been described in a variety of human cancers, but it has been poorly studied in noncancerous cytological samples from genital specimens positive for human papillomavirus (HPV). Furthermore, the relationship between this genetic event and the presence of high-risk and low-risk HPV types is poorly studied. Eighty-four noncancerous cytological samples from exocervical specimens that were positive for HPV types 6, 16, and 18 were analyzed for c-erbB-2 gene amplification using the genomic differential polymerase chain reaction with the single copy reference gene. An association between c-erbB-2 gene amplification and the group corresponding to HPV type 6 was found. Within the low-risk HPV group, c-erbB-2 amplification was associated to cervical intraepithelial neoplasia of grade I (CIN I). Because in the samples analyzed, most of the CIN I stage was characterized by a koilocytotic pattern, c-erbB-2 amplification could be related to this kind of cellular alteration. It would be important to study c-erbB-2 gene amplification and also gene expression in different CIN stages in order to determine its role and significance in cervical cancer.

Genotoxic Effects of Benzo[a]pyrene and Dibenzo[a,l]pyrene in a Human Lung Cell Line

Several studies have shown that polycyclic aromatic hydrocarbons (PAHs) produce genotoxic effects in assays performed in vivo and in vitro. This study was undertaken to investigate the ability of benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) to induce DNA damage in a human lung fibroblast cell line (MRC-5), using sister-chromatid exchanges test (SCEs), the comet assay, and evaluating point mutations in codon 12 of the K-ras protooncogene by polymerase chain reaction–single-strand conformation polymorphisms (PCR-SSCPs) and restriction fragment length polymorphisms (RFLP)-enriched PCR methods. Sister-chromatid exchanges frequencies were significantly increased in cells exposed to benzo[a]pyrene and dibenzo[a,l]pyrene in relation to controls (p < .001). Using the standard alkaline comet assay, significant differences between groups were found for the variable comet moment (CM) when cells were exposed to BP (p < .001) and DBP (p < .001). Nevertheless, PCR-SSCP and RFLP-enriched PCR methods did not show any association between treatments with BP and DBP and K-ras point mutations. The data presented in this study indicated that BP and DBP induced both DNA strand breaks and sister-chromatid exchanges but not significant point mutations at codon 12 of K-ras gene in the MRC-5 cell line.