Monitoring of DNA and cytogenetic damage in lymphocytes from persons with skin cancer diseases

There is a lot of interest in the studies that would help to understand whether there is a casual association between cancer and various types of molecular or cytogenetic damage detected in human cells. One major oncogenesis process is activation of proto-oncogenes by point mutations or chromosomal translocation. There are substantial evidence that indicates that the loss of heterozygosity of certain chromosomes is involved in human cancerogenesis. Our study aimed to elicit the possible association between cancer and DNA and cytogenetic abnormalities induced in lymphocytes of people bearing various categories of skin cancer cells. Fresh blood was collected by venipuncture from 25 individuals (including nine prior to cancer treatment). All patients were nonsmoking males, however 42.3 % of them were former smokers. Blood samples were divided into two parts and in the first part of samples cytogenetic studies were performed immediately, while from the second part lymphocytes were isolated and stored at -70oC for further studies in vitro. In the later one a single cell gel electrophoresis assay (SCGE) known as a Comet assay was performed to study individual susceptibility to the induction of DNA damage by UV or radiation and to estimate variability in cellular repair capabilities. An average of 220 per sample of good metaphase spreads in the first mitotic division, and 100 per sample in the second division, were accepted for analysis of cytogenetic damage. Chromosome and chromatid type aberrations were scored in the cells in the first mitosis and expressed as total aberration frequency including gaps and excluding gaps. Sister chromatid exchanges, high frequency cells and proliferative rate index were screened and evaluated in the second mitosis. Each of the patient revealed exceeding in at least one of the cytogenetic biomarkers level from the biomarker's level detected in a reference group. In order to estimate susceptibility of people to environmentally induced damage, the isolated lymphocytes were irradiated with 2 Gy dose of X-rays or 6 J/m2 of UV radiation and the single cell gel electrophoresis (SCGE assay) was performed. To compare various individual capabilities to repair damages induced, an incubation of cells in the presence or absence of cellular processes starting agent was done prior to DNA damage analysis. A statistically significant higher response to UV and a lower capability to repair UV induced damage in skin cancer patients were observed. On average no difference between control and skin cancer patients in the induction of DNA damage by X-rays was observed, though correlations between highest cytogenetic damages detected in lymphocytes of skin cancer patients and the lowest capability to repair DNA damage were noticed. (author)