Spontaneously immortalised T cell lines from Nijmegen Breakage Syndrome (NBS) patients demonstrate abnormal G1/S arrest and gains of 2p and 8q

J.K.Siwicki PhDa , S. Degerman MScb, M. Berglund MScc, C. Larsson MD, PhDc, J. Rygier MSc d, K. Chrzanowska MD, PhDe, G. Roos MD, PhDb

a Department of Immunology, Maria Sklodowska Memorial Cancer Center and Institute of Oncology, PL-02 781 Warsaw, Poland, b Department of Medical Biosciences, Pathology, Umea University, SE-90185 Umea, Sweden, c Department of Molecular Medicine, Karolinska Hospital, SE-171 76 Stockholm, Sweden, d Cytogenetic Laboratory, Maria Sklodowska Memorial Cancer Center and Institute of Oncology, PL-02 781 Warsaw, Poland, e Department of Medical Genetics, Children Memorial Health Institute, PL-04736, Warsaw, Poland.

Aim. Nijmegen Breakage Syndrome (NBS) is a rare autosomal recessive disease associated with microcephaly, growth retardation, radiosensitivity, chromosomal instability and high incidence of lymphoreticular neoplasms. In order to better understand molecular changes involved in immortalization of human lymphoid cells we characterized spontaneously immortalized T cell lines derived from NBS patients. We analyzed the expression of selected cell-cycle regulators, cell-cycle progression following gamma-irradiation and chromosome abnormalities. Methods. T cell lines (lines S4, S7 and S9) were derived from three NBS patients. Peripheral blood T lymphocytes were activated with wheat germ agglutinin (WGA) and propagated in the presence of recombinant human IL2. The expression of cell-cycle regulatory molecules was investigated using Western blotting. Cell-cycle progression following 4 Gy irradiation was determined by flow cytometry of propidium iodide-stained cells. Cytogenetic characterization was performed using G-banding and comparative genomic hybridization (CGH). Results. Wild-type expression patterns for pRb and p53 in all three immortalized NBS T cell lines coincided with increased level of p16 protein in line S7 and with apparently lower expression of p27 in line S4. The lines showed a decreased G1/S arrest and a functional G2/M checkpoint in response to gamma-irradiation. The poor G1/S response was not explained by a defect in the p53/p21 pathway which seemed normal in all lines, as well as the expression of pRb. Cytogenetic analysis showed multiple nonrandom chromosomal abnormalities including gains of 2p and 8q in all three lines and the development of hypotetraploidy in the S4 and S7 lines. Conclusions. Our data indicate that T cells from NBS patients are prone to spontaneous immortalization associated with abnormal G1/S arrest and gains in 2p and 8q. The results might relate to mechanisms of lymphoma development in patients with NBS.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Familial and Hereditary Cancer.