title: Transformation of the naturally occurring frog skin peptide, alyteserin-2a into a potent, non-toxic anti-cancer agent.
abstract: Alyteserin-2a (ILGKLLSTAAGLLSNL.NH(2)) is a cationic, amphipathic α-helical cell-penetrating peptide, first isolated from skin secretions of the midwife toad Alytes obstetricans. Structure-activity relationships were investigated by synthesizing analogs of alyteserin-2a in which amino acids on the hydrophobic face of the helix were replaced by L-tryptophan and amino acids on the hydrophilic face were replaced by one or more L-lysine or D-lysine residues. The Trp-containing peptides display increased cytotoxic activity against non-small cell lung adenocarcinoma A549 cells (up to 11-fold), but hemolytic activity against human erythrocytes increases in parallel. The potency of the N15K analog against A549 cells (LC(50) = 13 μM) increases sixfold relative to alyteserin-2a and the therapeutic index (ratio of LC(50) for erythrocytes and tumor cells) increases twofold. Incorporation of a D-Lys(11) residue into the N15K analog generates a peptide that retains potency against A549 cells (LC(50) = 15 μM) but whose therapeutic index is 13-fold elevated relative to the native peptide. [G11k, N15K] alyteserin-2a is also active against human hepatocarcinoma HepG2 cells (LC(50) = 26 μM), breast adenocarcinoma MDA-MB-231 cells (LC(50) = 20 μM), and colorectal adenocarcinoma HT-29 cells (LC(50) = 28 μM). [G11k, N15K] alyteserin-2a, in concentrations as low as 1 μg/mL, significantly (P < 0.05) inhibits the release of the immune-suppressive cytokines IL-10 and TGF-β from unstimulated and concanavalin A-stimulated peripheral blood mononuclear cells. The data suggest a strategy of increasing the cationicity while reducing the helicity of naturally occurring amphipathic α-helical peptides to generate analogs with improved cytotoxicity against tumor cells but decreased activity against non-neoplastic cells.
authors.affiliation: Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
authors.forename: Milena
authors.initials: M
authors.lastname: Mechkarska
authors.forename: Manju
authors.initials: M
authors.lastname: Prajeep
authors.forename: Kholoud
authors.initials: K
authors.lastname: Arafat
authors.forename: Milan
authors.initials: M
authors.lastname: Zaric
authors.forename: Miodrag L
authors.initials: ML
authors.lastname: Lukic
authors.forename: Samir
authors.initials: S
authors.lastname: Attoub
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001001:Anura / Q000378:metabolism*; D045744:Cell Line, Tumor; D019073:HT29 Cells; D006801:Humans; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000188:drug therapy*; D012867:Skin / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D023181:Antimicrobial Cationic Peptides; D000970:Antineoplastic Agents; C573618:alyteserin-2a peptide, Alytes obstetricans