Proline at the second position of the N-terminus of biologically active peptides involved in cell growth regulation is an evolutionarily conserved motif protecting them against cleavage by non-specific proteases. Just a small number of proline-specific hydrolases including dipeptidyl peptidase IV (DPP-IV) and related molecules is capable of cleaving such post-prolyl bond. DPP-IV, originally described on the basis of its enzymatic activity, is a ubiquitous, multifunctional homodimeric plasma membrane glycoprotein of type II. Subsequently, several other molecules related to DPP-IV by their enzymatic activity and/or sequence were discovered and classified as "dipeptidyl peptidase IV activity and/or structure homologues" (DASH). Along with canonical DPP-IV this group comprises DPP-IVbeta, DPP-II, DPP6, DPP8, DPP9, DPP10 and fibroblast activation protein alpha (FAP-alpha). Recent observations of deregulated expression of several DASH molecules in multiple human cancers led to the assumptions of their pathogenetic relevance in cancerogenesis. Here we review recent information about selected DASH molecules in human malignancies.