[Show abstract][Hide abstract] ABSTRACT: B-lymphoblastoid cell lines (LCLs) transformed by Epstein-Barr virus have a phenotype corresponding to activated B-lymphoblasts. Although they are widely used as models in various biological and medical studies, their innate morphological differentiation and apoptosis has been little studied. We report here that a large proportion of LCL cells spontaneously differentiate into smaller lymphoid cells which ultimately undergo apoptosis during conventional cell culture. Two distinct types of apoptosis with some intermediate types exist: type 1 apoptosis in small and medium-size cells with shrunken nuclei having heavily condensed chromatin in the whole nucleus region accompanied by relatively large internucleosomally fragmented DNA (above 2 kbp); type 2 apoptosis in large lymphoblasts with extremely lobulated nuclei having chromatin condensation beneath the nuclear membrane alone accompanied by smaller internucleosomally fragmented DNA (below 2 kbp). Type 1 apoptotic cells were far more numerous than type 2 apoptotic cells. The incidence of type 1 apoptosis was suppressed by cellular immortalization and was extremely stimulated at the end of the lifespan (crisis). These results provide essential information for us to use LCLs for various biological and medical studies including cellular immortalization, tumorigenesis and senescence.
Full-text · Article · Mar 2003 · Cell Structure and Function
[Show abstract][Hide abstract] ABSTRACT: Human B-lymphoblastoid cell lines transformed by Epstein-Barr (EBV-LCLs) are considered to be immortalized, although most of them show a normal diploid karyotype. Recently, we and others have shown that only part of EBV-LCLs is immortalized by developing strong telomerase activity that stabilizes the telomeres. In this study, we investigated the change in karyotypes during immortalization. All the eight immortalized cell lines developed clonal chromosomal aberrations accompanied by the development of strong telomerase activity. Interestingly, abnormal chromosomes were not shared among the immortalized cell lines. These results strongly suggest that chromosomal rearrangements and induction of strong telomerase activity are two events that take place in parallel in the process of immortalization of EBV-LCLs, and indicate that EBV-LCLs are clearly divided into two distinct groups, pre-immortal cell lines mostly with a normal diploid karyotype and post-immortal cell lines with a clonally abnormal karyotype.
Full-text · Article · Sep 2001 · Cancer Genetics and Cytogenetics