Environmental factors may play a role in
colon cancer. In this view, several studies investigated
tumor samples for the presence of various
viral DNA with conflicting results.
FINDINGS: We undertook a systematic
DNA analysis of 44 consecutive, prospectively collected primary
tumor samples by real time and qualitative PCR for viruses of known or potential oncogenic role in humans, including polyomavirus (JCV, BKV, Merkel cell polyomavirus), HPV, HTLV, HHV-8 and EBV. Negative controls consisted of surgical
resection margins. No evidence of genomic
DNA fragments from tested virus were detected, except for EBV, which was found in a significant portion of
tumors (23/44, 52%). Real-time PCR showed that EBV
DNA was present at a highly variable content (median 258 copies in 10(5) cells, range 15-4837). Presence of EBV
DNA had a trend to be associated with high lymphocyte infiltration (p = 0.06, χ2 test), and in situ hybridization with EBER1-2 probes revealed latency in a fraction of these lymphoid cells, with just a few scattered plasma cells positive for BZLF-1, an immediate early
protein expressed during lytic replication. LMP-1 expression was undetectable by immunohistochemistry.
CONCLUSIONS: