Clonal chromosomal aberrations accompanied by strong telomerase activity in immortalization of human B-lymphoblastoid cell lines transformed by Epstein-Barr virus

Human B-lymphoblastoid cell lines transformed by Epstein-Barr (EBV-LCLs) ar e considered to be immortalized, although most of them show a normal diploi d karyotype. Recently, we and others have shown that only part of EBV-LCLs is immortalized by developing strong telomerase activity that stabilizes th e telomeres. In this study, we investigated the change in karyotypes during immortalization. All the eight immortalized cell lines developed clonal ch romosomal aberrations accompanied by the development of strong telomerase a ctivity. Interestingly, abnormal chromosomes were not shared among the immo rtalized cell lines. These results strongly suggest that chromosomal rearra ngements and induction of strong telomerase activity are two events that ta ke place in parallel in the process of immortalization of EBV-LCLs, and ind icate that EBV-LCLs are clearly divided into two distinct groups, pre-immor tal cell lines mostly with a normal diploid karyotype and post-immortal cel l lines with a clonally abnormal karyotype. (C) 2001 Elsevier Science Inc. All rights reserved.