Study of ABCB1 polymorphism frequency in breast cancer patients from Poland.

BACKGROUND: The accumulation of mutagenic substances in the human body may result in DNA metabolism disruption followed by carcinogenesis. As a consequence of mutations in the genes coding for transmembrane protein pumps, the intracellular concentration of xenobiotics may significantly increase. This, in turn, may provoke altered risk for cancer development. The gene known to be the most relevant in the transport of numerous compounds is ABCB1 (also known as MDR1). Numerous mutations and polymorphisms that affect the encoded protein's (PgP) function were identified in this gene. The aim of the study was to define the frequency of 2677G>A,T and 3435C>T polymorphisms in a population of Polish breast cancer patients and to estimate their contribution to cancer development. METHODS: The polymorphism frequency analysis (209 patients vs. 202 control subjects) was performed either by allele-specific amplification (2677G>A,T) or by restriction fragment length polymorphism (RFLP) using the SAU3AI restriction enzyme (3435C>T) followed by verification with hybridization probe assays in a Real-Time system and sequencing. RESULTS: In the control group the frequency of individual 2677 genotypes was: wild homozygous GG = 34%, heterozygous G/T or G/A = 52.5% and variant homozygous AA or TT = 13.5%, while the genotype frequency in the group of studied patients was 43.5, 44.5 and 12%, respectively. In the control group, the frequency of individual 3435 genotypes was: CC = 25.4%, CT = 50.2%, TT = 24.4%, while the genotype frequency in the group of studied patients was 23, 46 and 31%, respectively. CONCLUSION: Thus, no significant differences in the studied polymorphism frequencies were observed. It is then suggested that the studied polymorphisms, although probably good candidates in other tissue cancer types, might not be good predictive factors in breast cancer risk or development in Caucasians.

Expression of 8-oxoguanine DNA glycosylase 1 (OGG1) and the level of p53 and TNF-αlpha proteins in peripheral lymphocytes of patients with Alzheimer's disease.

The aim of the study was to determine the extent of oxidative DNA damage (levels of 8-oxo2dG) and expression of OGG1 and p53 and TNF-α proteins in lymphocytes of Alzheimer's disease (AD) patients and a control group. The studies were conducted on 41 patients with AD, including 25 women and 16 men aged 34-84 years. The control group included 51 individuals, 20 women and 31 men aged 22-83 years. The level of 8-oxo2dG was determined using HPLC/EC/UV, and the level of OGG1 and p53 and TNF-α proteins was determined with the Western blot method. The results showed that both proteins participating in DNA repair (OGG1, p53) and the inflammatory protein TNF-α are involved in pathogenesis of neurodegenerative diseases. It also seems that a specific system for DNA repair (OGG1) may contribute to downregulation of the inflammatory factor (TNF-α) level, especially in the early stages of dementia. Moreover, the results showed that p53 protein can fulfil its function in DNA damage repair only in early stages of dementia. It is possible that OGG1 and p53 and TNF-α proteins together or separately may be involved in pathogenesis of AD by repair of oxidative DNA damage and/or apoptosis.

Phytosterols in physiological concentrations target multidrug resistant cancer cells.

Phytosterols have been proposed to act as potent anticancer agents. However the mechanism of their action has not been elucidated yet. Thus, the aim of our study was to determine whether plant sterols and their thermal processing products (in physiological concentration range) could influence the viability of cancer cells and thus could be considered as positive diet complements. Additionally we decided to study potential specificity of those natural compounds against cells showing high multidrug resistance. In this study we show that the cytotoxic effect of ß-sitosterol was observed in both, estrogen-dependent and estrogen-independent cells. It was also shown that the ß-sitosterol was significantly more cytotoxic in cells with basal ABCB1 expression (MCF7) than in multidrug resistant NCI/ADR-RES. Surprisingly, 5a,6a-epoxysitosterol did not decrease the viability of any investigated cells but on the contrary, it provoked their increased proliferation. It was shown that oxyphytosterols blocked the cell cycle of MCF7 cells in G0/G1 phase while did not affect NCI/ADR-RES cell cycle in physiological concentration range. We also show that PgP activity (responsible for Multidrug Resistance phenomena) is inhibited by ß-sitosterol. Thus, the phytosterols are supposed to act at various mechanisms but, what is most interesting, can target cells showing high multidrug resistance potential.

[siRNA targeting telomerase--effective tool in anti-cancer therapy?]. / SiRNA skierowane przeciwko telomerazie--skuteczne narzedzie w leczeniu nowotworów?

Telomeres are guanine-rich repeated sequences located at the ends of chromosomes. The loss of telomeric repeats after each cell division may function as a biological clock limiting the cell proliferation ability. Telomerase is a RNA-dependent DNA polymerase that synthesisezes telomeric DNA and thus enables cancer cells an unlimited proliferative potential. Human telomerase is a ribonucleoprotein complex composed of reverse transcriptase-hTERT, RNA component-hTR (functioning as a template for the telomeric DNA addition) and associated proteins. Telomerase activity is present in most malignant cells but undetectable in most normal cells. The enzyme and its altered activity distinguishing cancer cells, is an attractive molecular target for anti-cancer therapy. One of the most promising methods for modulation of the telomerase activity is RNA interference. Many investigators showed that targeting different subunits of telomerase (mainly hTERT) with siRNA had inhibitory effects on expression and activity of the enzyme and cells proliferation. siRNA targeting telomerase has the possibility to became effective anti-cancer agent especially in an adjuvant therapy.