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.