Bleomycin induces short-term telomere fragility in Epstein-Barr virus-transformed human lymphoblastoid cells

The induction of telomere dysfunction-related chromosomal aberrations by the radiomimetic antibiotic bleomycin (BLM) was studied in human lymphoblastoid cells immortalized with the Epstein-Barr virus (EBV). To this end, an EBV-induced lymphoblastoid cell line (T-37) was exposed to increased concentrations of BLM (10-100 µg/mL) for 2 h at 37ºC, and telomere aberrations were analyzed 24 h (first mitosis) after treatment using PNA-FISH with pan-telomeric plus pan-centromeric probes. Telomere signal duplications (TSD) increased significantly in BLM-exposed cells (p < 0.01), although the concentration-response relationship was non-linear. Most of the induced TSD (95-99 %) were of chromatid-type. No induction of telomere signal loss, telomere fusions or telomere associations by BLM was observed in T-37 cells. These findings show that BLM induces short-term telomere dysfunction in EBV-transformed human lymphoblastoid cells in the form of TSD (which implies telomere fragility) and suggest that these effects mainly occur during the G2 stage of the cell cycle. The persistence of this type of aberrations in the long-term in EBV-induced lymphoblastoid cells and other human cells exposed to BLM may be of medical relevance. Telomere fragility induced by BLM could promote genomic instability, which might contribute to the development of secondary tumors in patients undergoing chemotherapy based on this compound. Consequently, our study raises concerns about the potential long-term genomic effects of BLM in treated patients and suggests that the analysis of TSD could be a useful biomarker for detecting BLM-induced telomere dysfunction in human cells.