In Vitro: P53R3 (10 μg/ml; 24 hours; in the absence or presence of the unlabelled p53 consensus oligonucleotide) restores p53-specific DNA binding activity to p53R273H (a DNA contact mutant) and p53R175H (a structural mutant) in WiDr colon tumour cells harbouring p53R273H and KLE cells with p53R175H.P53R3 (1-33 μg/ml; 24 hours) inhibits the proliferation of the LN-308 sublines expressing mutant p53 plasmids in a p53-dependent manner. The p53R175H-dependent effects are strong over a broad range of concentrations, but p53R273H-dependent effects are weaker and requires high concentrations of P53R3.P53R3 induces p53R248W reactivation is more pronounced proliferation inhibition than observed with p53R273H. P53R3 does not exhibit cytotoxic effects even at concentrations close to its solubility limit (33 μg/ml).P53R3 (33 μg/ml; 18 hours) induces a strong decrease in S phase cells and a G0/G1 cell cycle arrest in LN-308 p53R175H and LN-308 p53R273H cells. But it does not affect cell cycle distribution of LN-308 p53R248W cells.