PLAC1 and cancer: QD-P was able to selectively internalize into PLAC-1+ HT-29 and HCT-116 while avoiding PLAC-1- due to the quantitative and spatially selective internalization and this demonstrated both the specificity of the peptide as a targeting moiety and anti-cancer capacity of the peptide through downregulation of PLAC-1 expression and invasiveness and potential to metastasize.