In the present study, we examined for the first time the effect of VPA in combination with fluoropyrimidines and RT on human CRC cell lines. Since p53 signaling is frequently dysregulated in CRC and the loss of a complete functional p53 is often associated with resistance to current therapies and poor prognosis, we also investigated the role of p53 in the combination setting, taking advantage of four cellular models: the HCT116 p53-wild type (wt) and its p53-null subline HCT-116 p53−/−, and the HT29 and SW620 p53-mutant (mut) cell lines. Here, TP53 is linked to colorectal carcinoma.