Fig. 4

Electrophoresis of DNA fragments in stage IV CRC samples. A Viral regulatory region was amplified by nested PCR, using JC-BK-specific primers. B Beta-actin gene was amplified by specific primers. The product was analyzed by electrophoresis in 2.5% agarose gel. Following electrophoresis, the gel was stained with ethidium bromide and photographed under UV light. JCPyV and BKPyV genomic DNA were cloned into a plasmid and used as a positive control. M marker, Lane numbers represent the number of the tissue sample involved. N negative control (without DNA). T: a tested sample was run aligned with the CRC tissues