It should be noted that apoptosis induction, accumulation of the cells in the S-phase, increased protein levels of the tumor suppressor proteins p53 and pRb, and decreased cell viability were evidenced following exposure of tumor cells to CDV for 4 to 5 days [19,20], indicating that cells need to accumulate sufficient drug-induced stress before apoptosis takes place. This evidence concerns the gene RB1 and neoplasm.