MC-38 mouse colon cancer and 4T1 mouse mammary tumor cell lines were purchased from the American Type Culture Collection (ATCC, USA). Cells were cultured at 37 °C and 5 % CO2 in Dulbecco's modified eagle medium (DMEM, Lonza, Switzerland) supplemented with 10% fetal bovine serum (FBS, Gibco Laboratories, USA), 1 % of 100 u/mL penicillin/streptomycin (Gibco Laboratories) and 1% L-glutamine (Gibco Laboratories). Oncolytic adenovirus Ad5D24 has been characterized by performing titration (VP/ml) and molecular analyses (PCR, restriction enzyme assay) to check virus genome stability and integrity as described elsewhere 22, expanded in human lung cancer cell line A549 and purified on cesium chloride gradients 23. The viral particle concentration was determined by OD260-reading and standard TCID50 (tissue culture infectious dose 50) assay was performed to determine infectious particle titer.