The present invention relates to an isolated peptide for use in the treatment of cancer consisting of 12 to 50 amino acid residues comprising: at least two beta-strands, or at least two alpha-helices, or at least one beta-strand and at least one alpha-helix； wherein said beta-strands and/or alpha-helices are preferably separated from each other by at least one turn, wherein the peptide has a net positive charge of +7 or more； wherein said peptide comprises at least one peptide moiety having amino acid sequence (X1)M-X2-(X3)P-X4-(X5)Q-X6-(X7)S or the reverse sequence thereof, wherein X1 is a hydrophobic amino acid, preferably selected from the group consisting of phenylalanine (Phe), alanine (Ala), leucine (Leu) and valine (Val), X2 is a hydrophobic amino acid, preferably tryptophan (Trp), X3 is selected from the group consisting of alanine (Ala), arginine (Arg), glutamine (Gln), asparagine (Asn), proline (Pro), isoleucine (Ile), leucine (Leu) and valine (Val), X4 is selected from the group consisting of isoleucine (Ile), phenylalanine (Phe), tryptophan (Trp) and tyrosine (Tyr), X5 is selected from the group consisting of arginine (Arg), lysine (Lys), tyrosine (Tyr) and phenylalanine (Phe), X6 is a hydrophobic amino acid, preferably selected from the group consisting of isoleucine (Ile), tryptophan (Trp), valine (Val) and leucine (Leu), and X7 is selected from the group consisting of arginine (Arg), lysine (Lys), isoleucine (Ile) and serine (Ser), and wherein M is 1 or 2, Q is 1 or 2, P is 2 or 3, and S is 1, 2, 3 or 4 under the proviso that if (X5)Q is Arg-Arg S is 1； and wherein said peptide is devoid of intramolecular disulfide bonds.
