Nijmegen Breakage Syndrome (NBS) is a rare autosomal, recessive disease caused by homozygous mutations in the NBS1 gene. The most common deletion of 5 bp (657del5) in exon 6, which affects mostly the population of Central Europe is observed. Among the typical features of this disorder is that NBS patients experience a high incidence of lymphoid malignancies as well. An increased risk of solid tumors development for 657del5 carriers was the reason to investigate the role of NBS1 gene as a susceptible one for the breast cancer. The purpose of this work is to identify mutations in all 16 exons of the NBS1 gene in the group of the patients with diagnosed breast cancer and the control group of healthy individuals. In the group of 270 women with breast cancer, seven cases of mutated NBS1 gene were revealed. In the subgroup presenting mutated NBS1 gene, the mutation I171V in 5th exon occurred in five cases. It is the first such a discovery concerning breast cancer patients because this mutation had been previously observed only in the course of lymphoid or hematological malignancies. The rate of I171V mutation in the group of breast cancer patients was significantly higher than in the controls (OR: 9.42; 95% CI: 1.09-81.05; P = 0.02). The conclusion is that heterozygous germline mutation I171V in NBS1 gene is a significant risk factor for breast cancer development. It concerns especially the women whose first degree relatives had a previously diagnosed breast cancer (OR: 6.00; 95% CI: 0.98-38.07; P = 0.04). The histopathological and clinical features of breast cancer with I171V mutation suggest accumulation of the negative prognostic factors. The treatment's results however were unexpectedly satisfactory, that is why further investigations are necessary to assess the role of I171V mutation in NBS1 gene as a prognostic and predictive factor for breast cancer.

It can be concluded that all the cancer cells tested have higher telomerase expression and activity than normal cells. Therefore, telomerase can be a good cancer marker, provided that quantitative analysis is carried out.

Reactivation of telomerase plays an important role in carcinogenesis. Malignant cells almost always possess high activity and expression of telomerase. The aim of this study was to see whether there is any relationship between telomerase activity and expression and hTERT and hTERC gene amplification in acute lymphoblastic leukemia (ALL) and non-lymphoblastic leukemia (ANLL) cells. In addition telomere length was tested in leukemic cells at the time of diagnosis and during remission. Expression of the three components of telomerase (hTERT, hTERC and TP1) as well as telomerase activity was found both in ALL and ANLL cells. Telomerase activity was diminished in patients in remission. The leukemic cells showed considerable heterogeneity of terminal restriction fragments, that is telomere length. ALL cells showed a variable pattern of telomere length in contrast to ANLL cells which produced a predominantly short telomere pattern. Telomere length in the lymphocytes of leukemia patients was shorter in remission as compared to the time of diagnosis. FISH analysis revealed amplification of hTERT and hTERC genes in ALL and ANLL cells. Quantitative analysis showed that leukemic cells possess higher number of hTERT and hTERC copies than the normal PBL. Our results suggest that the activation of telomerase in leukemic cells is connected with amplification of hTERT and hTERC genes. The high expression and activity of telomerase found in leukemic cells may be partially explained by amplified hTERT and hTERC genes. Amplification of the telomerase genes seems to be a common event in carcinogenesis and may play a role in telomerase reactivation leading to cell immortalization.

In the etiopathogenesis of multiple sclerosis (MS), both genetic and environmental factors play an important role. Among environmental factors, viral infections are most likely connected with the etiology of MS. There are many evidence suggesting possible involvement of retroviruses in the development of autoimmune diseases including MS. Multiple sclerosis-associated retrovirus (MSRV) seems to be the important candidate for viral etiology of MS. The aim of the study was to analyze MSRV pol sequences in patients with MS. As control, groups of myasthenia gravis, Parkinson's disease, and migraine patients, and healthy individuals have been studied. The MSRV pol sequences have been analyzed in RNA isolated from the serum and in DNA and RNA of peripheral blood lymphocytes from untreated MS patients and control groups. The MSRV pol sequences have been detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and PCR technique, using specific oligonucleotide primers. In the serum RNA (cDNA), MSRV pol sequences have been identified in 31/32 MS patients. MSRV pol sequences were detected in serum cDNA of 9/17 myasthenia gravis patients, 7/16 Parkinson's disease patients, 10/21 migraine patients, and 13/27 healthy individuals. MSRV pol sequences were observed also in RNA from lymphocytes of all MS patients, 12/17 myasthenia gravis patients, 9/16 Parkinson's disease patients, 14/21 migraine patients, and 18/27 healthy donors. In the DNA from peripheral blood lymphocytes of all studied patients and healthy individuals, MSRV pol sequences have been found. The observed pattern of fiber-fluorescence in situ hybridization (FISH) signals suggests the presence of multiple copies of MSRV pol sequences, most likely tandemly dispersed in the genome. It can be concluded that MSRV pol sequences are endogenous, widespread in lymphocytes DNA, and transcribed into RNA of MS patients as well as of other studied patients and healthy individuals. However, more frequent expression of MSRV sequences detected in lymphocytes RNA (cDNA), as well as their presence in higher frequency in the serum of MS patients, may suggest the involvement of MSRV in the etiopathogenesis on MS.