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Breakage Syndrome (breakage + syndrome)
Kinds of Breakage Syndrome Selected AbstractsCell cycle checkpoints and their impact on anticancer therapeutic strategiesJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2004Alan Eastman Abstract Cells contain numerous pathways designed to protect them from the genomic instability or toxicity that can result when their DNA is damaged. The p53 tumor suppressor is particularly important for regulating passage through G1 phase of the cell cycle, while other checkpoint regulators are important for arrest in S and G2 phase. Tumor cells often exhibit defects in these checkpoint proteins, which can lead to hypersensitivity; proteins in this class include ataxia,telangiectasia mutatated (ATM), Meiotic recanbination 11 (Mre11), Nijmegen breakage syndrome 1 (Nbs 1), breast cancer susceptibility genes 1 and 2 (BRCA1), and (BRCA2). Consequently, tumors should be assessed for these specific defects, and specific therapy prescribed that has high probability of inducing response. Tumors defective in p53 are frequently considered resistant to apoptosis, yet this defect also provides an opportunity for targeted therapy. When their DNA is damaged, p53-defective tumor cells preferentially arrest in S or G2 phase where they are susceptible to checkpoint inhibitors such as caffeine and UCN-01. These inhibitors preferentially abrogate cell cycle arrest in p53-defective cells, driving them through a lethal mitosis. Wild type p53 can prevent abrogation of arrest by elevating levels of p21waf1 and decreasing levels of cyclins A and B. During tumorigenesis, tumor cells frequently loose checkpoint controls and this facilitates the development of the tumor. However, these defects also represent an Achilles heel that can be targeted to improve current therapeutic strategies. © 2003 Wiley-Liss, Inc. [source] Telomerase upregulation is a postcrisis event during senescence bypass and immortalization of two Nijmegen breakage syndrome T cell culturesAGING CELL, Issue 2 2010Sofie Degerman Summary Our knowledge on immortalization and telomere biology is mainly based on genetically manipulated cells analyzed before and many population doublings post growth crisis. The general view is that growth crisis is telomere length (TL) dependent and that escape from crisis is coupled to increased expression of the telomerase reverse transcriptase (hTERT) gene, telomerase activity upregulation and TL stabilization. Here we have analyzed the process of spontaneous immortalization of human T cells, regarding pathways involved in senescence and telomerase regulation. Two Nijmegen breakage syndrome (NBS) T cell cultures (S3R and S4) showed gradual telomere attrition until a period of growth crisis followed by the outgrowth of immortalized cells. Whole genome expression analysis indicated differences between pre-, early post- and late postcrisis cells. Early postcrisis cells demonstrated a logarithmic growth curve, very short telomeres and, notably, no increase in hTERT or telomerase activity despite downregulation of several negative hTERT regulators (e.g. FOS, JUN D, SMAD3, RUNX2, TNF-, and TGF,-R2). Thereafter, cMYC mRNA increased in parallel with increased hTERT expression, telomerase activity and elongation of short telomeres, indicating a step-wise activation of hTERT transcription involving reduction of negative regulators followed by activation of positive regulator(s). Gene expression analysis indicated that cells escaped growth crisis by deregulated DNA damage response and senescence controlling genes, including downregulation of ATM, CDKN1B (p27), CDKN2D (p19) and ASF1A and upregulation of CDK4, TWIST1, TP73L (p63) and SYK. Telomerase upregulation was thus found to be uncoupled to escape of growth crisis but rather a later event in the immortalization process of NBS T cell cultures. [source] Impaired removal of DNA interstrand cross-link in Nijmegen breakage syndrome and Fanconi anemia, but not in BRCA-defective groupCANCER SCIENCE, Issue 11 2008Ken Tsuchida Human diseases characterized by a high sensitivity to DNA interstrand cross-links (ICL) and predisposition to malignance include Nijmegen breakage syndrome (NBS) and Fanconi anemia (FA), which is further classified to three groups: (1) FA core-complex group; (2) FA-ID complex group; and (3) breast cancer (BRCA)-defective group. The relationships between these four groups and the basic defect in ICL repair remain unclear. To study the details of ICL repair in NBS and FA, a highly sensitive PPB (psoralen,polyethylene oxide,biotin) dot blot assay was developed to provide sensitive quantitative measurements of ICL during the removal process. Studies utilizing this assay demonstrated a decreased rate of ICL removal in cells belonging to the FA core-complex group (e.g. groups A and G) and FA-ID complex group (group D2), while ICL removal was restored to normal levels after these cells were complemented with wt-FANCA, wt-FANCG and wt-FANCD2. Conversely, FA-D1 cells with a defective BRCA2 protein displayed normal ICL removal, although they were compromised with respect to recombination. This normal ICL removal rate in recombination-deficient cells was confirmed by using XRCC3-defective Chinese hamster cells, which are similarly compromised with respect to recombination and are sensitive to mitomycin C. The present study also showed that cells from patients with Nijmegen breakage syndrome were defective in ICL removal, while they were impaired in the recombination. These results indicate an obvious defect of FA and NBS in the ICL repair process, except in the BRCA-defective group, and a separate step of recombination-mediated repair pathway between the BRCA group and NBS. (Cancer Sci 2008; 99: 2238,2243) [source] G2 -phase radiation response in lymphoblastoid cell lines from Nijmegen breakage syndromeCELL PROLIFERATION, Issue 2 2002A. Antoccia The relationship between G2 -phase checkpoint activation, cytoplasmic cyclin-B1 accumulation and nuclear phosphorylation of p34CDC2 was studied in Nijmegen breakage syndrome cells treated with DNA damaging agents. Experiments were performed on lymphoblastoid cell lines from four Nijmegen breakage syndrome patients with different mutations, as well as on cells from an ataxia telangiectasia patient. Lymphoblastoid cell lines were irradiated with 0.50,2 Gy X-rays and the percentage of G2 -phase accumulated cells was evaluated by means of flow cytometry in samples that were harvested 24 h later. The G2 -checkpoint activation was analysed by scoring the mitotic index at 2 and 4 h after treatment with 0.5 and 1 Gy X-rays and treatment with the DNA double-strand break inducer calicheamicin-,1. Cytoplasmic accumulation of cyclin-B1 was evaluated by means of fluorescence immunostaining or Western blotting, in cells harvested shortly after irradiation with 1 and 2 Gy. The extent of tyrosine 15-phosphorylated p34CDC2 was assessed in the nuclear fractions. Nijmegen breakage syndrome cells showed suboptimal G2 -phase checkpoint activation respect to normal cells and were greatly different from ataxia telangiectasia cells. Increased cytoplasmic cyclin-B1 accumulation was detected by both immunofluorescence and immunoblot in normal as well as in Nijmegen breakage syndrome cells. Furthermore, nuclear p34CDC2. phosphorylation was detected at a higher level in Nijmegen breakage syndrome than in ataxia telangiectasia cells. In conclusion, our data do not suggest that failure to activate checkpoints plays a major role in the radiosensitivity of Nijmegen breakage syndrome cells. [source] Lessons learned from DNA repair defective syndromesEXPERIMENTAL DERMATOLOGY, Issue 6 2007Kai-Martin Thoms Abstract:, Genomic instability is the driving force behind cancer development. Human syndromes with DNA repair deficiencies comprise unique opportunities to study the clinical consequences of faulty genome maintenance leading to premature aging and premature cancer development. These syndromes include chromosomal breakage syndromes with defects in DNA damage signal transduction and double-strand break repair, mismatch repair defective syndromes as well as nucleotide excision repair defective syndromes. The same genes that are severely affected in these model diseases may harbour more subtle variations in the ,healthy' normal population leading to genomic instability, cancer development, and accelerated aging at later stages of life. Thus, studying those syndromes and the molecular mechanisms behind can significantly contribute to our understanding of (skin) cancerogenesis as well as to the development of novel individualized preventive and therapeutic anticancer strategies. The establishment of centers of excellence for studying rare genetic model diseases may be helpful in this direction. [source] | |||||||||||||