This invention relates, e.g., to an inhibitory peptide or CPP inhibitor which specifically binds to p53 having an aberrant conformation (e.g., is aggregated or misfolded) and inhibits p53 amyloidogenic aggregation or restores proper folding of the misfolded protein. Methods of using the inhibitory peptide or CPP inhibitor (e.g. to treat subjects having tumors that comprise aggregated p53) are described.