The present invention provides an oligopeptidic compound comprising a PCNA interacting motif, or a nucleic acid molecule comprising a sequence encoding said oligopeptidic compound, for use in therapy, wherein the PCNA interacting motif is X1X2X3X3′X1′- (SEQ ID NO: 1), wherein X1 and X1′- are independently selected from the group of basic amino acids, X2 is a lipophilic amino acid and X3 and X3′ are independently selected from the group of uncharged amino acids； and wherein the oligopeptidic compound is further characterized by at least one of the following: (i) the oligopeptidic compound comprises at least one signal sequence； (ii) the PCNA interacting motif is [K/R]-F-[L/I/V]-[L/I/V]-[K/R] (SEQ ID NO: 27). Particularly the therapy may be the treatment of a disorder or condition where it is desirable to inhibit the growth of cells, for example a hyperproliferative disorder, or a treatment which involves cytostatic therapy e.g., myeloablation. In certain aspects the compounds of the invention may be used as cytostatic agents in their own right. In other aspects of the invention oligopeptidic compounds comprising such a motif may be used in conjunction with cytostatic agents or with radiotherapy.
