Gomesin is a potent antimicrobial peptide (AMP) isolated from hemocytes of the spider Acanthoscurria gomesiana. The present study aimed at determining whether gomesin exerted antitumor activity in vitro and in vivo. Topical treatment of subcutaneous murine melanoma with gomesin incorporated in a cream base significantly delayed tumor growth. A direct cytotoxicity of gomesin in murine melanoma B16F10-Nex2 cells and several human tumor cell lineages was observed in vitro, with IC(50) values below 5 microM. The beta-hairpin structure of gomesin with disulfide bridges seemed essential for optimal activity. d-Gomesin was equally active. A membrane-permeabilizing activity was suggested, as gomesin bound to the cell membrane and cytoplasmic lactate dehydrogenase was detected extracellularly. At doses causing partial growth of tumor cells, gomesin allowed internalization of macromolecules (immunoglobulins), which increased the cytotoxic effect. The in vivo antitumor effect of gomesin might also involve a cytotoxic effect on endothelial cells because cultured human endothelial cells were killed in vitro at a similar concentration range. This effect represents a novel and potential use for gomesin as a topical agent against unsuccessfully treated intradermal and epithelial skin cancers. To our knowledge, this is the first report on the successful topical use of AMPs in cancer treatment.

BackgroundComplementarity-determining regions (CDRs) are immunoglobulin (Ig) hypervariable domains that determine specific antibody (Ab) binding. We have shown that synthetic CDR-related peptides and many decapeptides spanning the variable region of a recombinant yeast killer toxin-like antiidiotypic Ab are candidacidal in vitro. An alanine-substituted decapeptide from the variable region of this Ab displayed increased cytotoxicity in vitro and/or therapeutic effects in vivo against various bacteria, fungi, protozoa and viruses. The possibility that isolated CDRs, represented by short synthetic peptides, may display antimicrobial, antiviral and antitumor activities irrespective of Ab specificity for a given antigen is addressed here.Methodology/Principal FindingsCDR-based synthetic peptides of murine and human monoclonal Abs directed to: a) a protein epitope of Candida albicans cell wall stress mannoprotein; b) a synthetic peptide containing well-characterized B-cell and T-cell epitopes; c) a carbohydrate blood group A substance, showed differential inhibitory activities in vitro, ex vivo and/or in vivo against C. albicans, HIV-1 and B16F10-Nex2 melanoma cells, conceivably involving different mechanisms of action. Antitumor activities involved peptide-induced caspase-dependent apoptosis. Engineered peptides, obtained by alanine substitution of Ig CDR sequences, and used as surrogates of natural point mutations, showed further differential increased/unaltered/decreased antimicrobial, antiviral and/or antitumor activities. The inhibitory effects observed were largely independent of the specificity of the native Ab and involved chiefly germline encoded CDR1 and CDR2 of light and heavy chains.Conclusions/SignificanceThe high frequency of bioactive peptides based on CDRs suggests that Ig molecules are sources of an unlimited number of sequences potentially active against infectious agents and tumor cells. The easy production and low cost of small sized synthetic peptides representing Ig CDRs and the possibility of peptide engineering and chemical optimization associated to new delivery mechanisms are expected to give rise to a new generation of therapeutic agents.

Palladacycle compounds obtained from N, N-dimethyl-1-phenethylamine (dmpa), phenyl-2-pyridinyl-acetylene and 1-phenyl-3-N, N-dimethylamine-propine, respectively, were complexed to 1, 2 ethanebis (diphenylphosphine) (dppe) ligand to synthesize antitumor cyclopalladated complexes that were tested in vitro and in vivo against syngeneic B16F10-Nex2 murine melanoma cells of low immunogenicity implanted subcutaneously in mice. Complexes were not toxic to mice injected 3 times i.p. with as much as 60 M/animal/ week. Of 3 cyclopalladated complexes that were inhibitory in vitro at low concentrations (<1.25 M), complex 7a was the most active in vivo, delaying tumor growth and prolonging animal survival. In vitro, binucleate complex 7a caused a collapse of respiratory activity with an abrupt decrease of extracellular acidification on short incubation (up to 100 min), followed by DNA degradation after 24 hr. The apoptosis-like reaction to this Pd-complex was not accompanied by increased levels of caspases 1 and 3. Complex 7a bound to a bacterial plasmid DNA, causing late conformational changes after 24 hr. Two other complexes with different C, N-cycles were also apoptotic and 2 binucleated ones were inactive. These results introduce the palladacycle-dppe complexes as promising antitumor drugs with exquisite structural specificities and for action in vivo and in vitro.

This work reports on the results of double immunodiffusion (ID), counterimmunoelectrophoresis (CIE), complement fixation (CF) and indirect immunofluorescence (IIF) techniques in the serodiagnosis of paracoccidioidomycosis. The study was undertaken on four groups of individuals: 46 patients with untreated paracoccidioidomycosis, 22 patients with other deep mycoses, 30 with other infectious diseases (tuberculosis and cutaneous leishmaniasis) and 47 blood donors as negative controls. Data were obtained using Paracoccidioides brasiliensis antigens, i.e.,a yeast culture filtrate for ID, CIE and CF, and a yeast cell suspension for IIF. The sensitivity, specificity and efficiency values were measured according to GALEN & GAMBINO8.The gel precipitation tests (ID and CIE) showed the greatest sensitivity (91.3 and 95.6%, respectively), maximum specificity (100%) and the highest efficiency values when compared to the CF and IIF tests.

Background:Immunoglobulin complementarity-determining region (CDR) peptides frequently display antitumor activities. Results: Monoclonal antibody C7 CDR-H2 binds to ␤-actin and induces polymerization, F-actin stabilization, and tumor cell death. Conclusion: Alterations of actin dynamics trigger reactive oxygen species and tumor cell apoptosis. Significance: The in vitro apoptotic effect and in vivo antimetastatic activity of peptide C7H2 makes it a candidate to be developed as an anticancer drug.