Effect of HPV-16 E5 expression on the sensitivity of melanoma cells to the tyrosine related antiblastic agents. M14 control cells (grey bars) or HPV-16 E5 expressing cells (black bars) were incubated with DHBA (up) or BSO (down) at a 30 μM concentration. After 48 h incubation, the cell number was determined using the CV assay as described in the methods section. The E5 expression is associated with a marked sensitivity of melanoma cells to the named anti-tumour agents. Similar results were obtained with FRM cells (data not shown). Reported values are expressed as A540 and are the mean ± SD. of eight independent replicas of a representative experiment in a set of four. Statistical comparison was made using the non parametric Mann – Whitney test * p < 0.05; ** p < 0.005.