Immortalized Human Lymphoblastoid Cells-EBV (KMS-15)

Long-term Culture of EBV-induced Human Lymphoblastoid Cell Lines Reveals Chromosomal Instability

Lymphoblastoid cell lines (LCLs) are essential for genetic research, yet their genomic stability during prolonged culture is poorly defined. Volleth et al. performed serial cytogenetic analyses at 8-week intervals for up to three years across 10 LCLs derived from individuals with normal, marker-bearing, or aberrant baseline karyotypes.

All LCLs maintained their original karyotype only during the initial months of culture. Subsequently, every cell line acquired clonal chromosomal aberrations, with the proportion of cytogenetically normal cells declining continuously over time. Notably, karyotype evolution varied even between lines from the same donor. The most prevalent abnormality was trisomy 12, emerging as a clonal event in all cell lines between 21–49 weeks post-infection (median: 27 weeks). This clone expanded rapidly, achieving >50% prevalence within 27–62 weeks (median: 39.5 weeks) and requiring a median of only 20.5 weeks to progress from undetectable to dominant (>50% of metaphases). By the end of the observation period, seven lines harbored trisomy 12 in >90% of cells (Fig. 1). One line progressed to hypertetraploidy (50 chromosomes; +5, +10, +12, +12) before dying, while another acquired structural rearrangements alongside trisomy 12. The results for cell lines N1 and N2 are shown in Figs. 2 and 3, respectively. Unexpectedly, one line reverted to its baseline karyotype despite prior trisomy 12 dominance. Three lines ceased proliferating during monitoring; all had acquired clonal aberrations beforehand, demonstrating that chromosomal instability does not preclude crisis or guarantee immortalization. These findings establish trisomy 12 as a near-universal, early, and dominant event in LCL evolution, underscoring the necessity of cryopreserving early-passage aliquots to preserve the donor's primary genetic architecture.