Epstein–Barr virus promotes genomic instability in Burkitt's lymphoma

Abstract

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of human malignancies but the mechanisms of oncogenesis remain largely unknown. Genomic instability and chromosomal aberrations are hallmarks of malignant transformation. We report that EBV carriage promotes genomic instability in Burkitt's lymphoma (BL). Cytogenetic analysis of EBVÀ and EBV þ BL lines and their sublines derived by EBV conversion or spontaneous loss of the viral genome revealed a significant increase in dicentric chromosomes, chromosome fragments and chromatid gaps in EBV-carrying cells. Expression of EBV latency I was sufficient for this effect, whereas a stronger effect was observed in cells expressing latency III. Telomere analysis by fluorescent in situ hybridization revealed an overall increase of telomere size and prevalence of telomere fusion and double strand-break fusion in dicentric chromosomes from EBV þ cells. Phosphorylated H2AX, a reporter of DNA damage and ongoing repair, was increased in virus-carrying cells in the absence of exogenous stimuli, whereas efficient activation of DNA repair was observed in both EBV þ and EBVÀ cells following treatment with etoposide. These findings point to induction of telomere dysfunction and DNA damage as important mechanisms for EBV oncogenesis.

Chromosomal rearrangements after ex vivo Epstein–Barr virus (EBV) infection of human B cells

“…Thus, genomic instability in LCLs is not just a tissue culture event or a result of critically shortened telomeres (Counter et al, 1994), but seems to be inherently associated with EBV infection. Similar associations between the presence of EBV and the level of genomic instability had already been made in BL cell lines (Kamranvar et al, 2007;Gruhne et al, 2009). How the virus triggers telomere dysfunction needs to be investigated further.…”

“…Epstein-Barr virus carriage in different BL cell lines has been associated with a higher spontaneous level of double-strand breaks (DSBs) and with an increase in nontransmissible structural aberrations such as dicentric chromosomes, chromosome fragments and chromatid gaps (Kamranvar et al, 2007). These structural aberrations have been specifically associated with EBNA1, and seem to be caused by an increase in reactive oxygen species (Gruhne et al, 2009).…”

Three Epstein–Barr virus latency proteins independently promote genomic instability by inducing DNA damage, inhibiting DNA repair and inactivating cell cycle checkpoints

“…We have earlier shown that EBV carriage is associated with a significant increase in nonclonal chromosomal aberrations that are caused by inadequate DNA repair (Kamranvar et al, 2007). Dicentric chromosomes, chromosome fragments and gaps were shown to occur with different frequencies in cells expressing various combinations of EBV latency genes, suggesting that more than one viral protein may promote this phenotype.…”

“…Furthermore, using a panel of EBV-positive and EBV-negative BL lines, we have shown that EBV carriage is associated with a significant increase in nonclonal chromosomal aberrations, mainly dicentric chromosome, chromosome fragments and gaps. This was accompanied by ongoing DNA damage and activation of the DNA damage response (DDR), as indicated by phosphorylation of histone H2AX (Kamranvar et al, 2007). Interestingly, these markers of genomic instability were present in cell lines expressing EBNA-1 alone but were significantly augmented in cells expressing broader forms of latency, suggesting that more than one viral protein may contribute to this phenotype.…”

Tumor Cell Development: A Role for Viruses and Telomerase Activity?

“…Indeed, in spite of most viral infections influence tumor development (regarding telomere biology) through telomere shortening, others were evidenced to increase telomere length. 22 For example, Epstein-Barr virus (EBV)-positive Burkitt's lymphoma cell lines were described as having longer telomeres than EBV-negative cell lines, although telomerase activity levels were similar, 23 thus suggesting that EBV infection may have telomerase-independent effects on telomere dynamics. In this regard, there is an induction of telomere abnormalities in cells expressing EBV nuclear antigen 1 (EBNA1), including loss or gain of telomere signals, telomere fusion, and heterogeneous telomere length.…”