An earlier study shows that transfection of FLSs with a plasmid expressing PUMA resulted in rapid apoptosis of the transfected cells in vitro 8, 9. In the present study, a HAdV5-based vector carrying the PUMA gene under the control of the cytomegalovirus (CMV) immediate-early promoter (HAdV5-PUMA) was tested in vitro in human and rat FLSs and evaluated for the cytological effects due to PUMA expression and a HAdV5-GFP vector is used as control.