RESUMO
Synthesis and preliminary biological evaluation of a 35-member library of bistramide A stereoisomers are reported. All eight stereoisomers of the C1-C13 tetrahydropyran fragment of the molecule were prepared utilizing crotylsilane reagents 9 and 10 in our [4+2]-annulation methodology. In addition, the four isomers of the C14-C18 gamma-amino acid unit were accessed via a Lewis acid mediated crotylation reaction with use of both enantiomers of organosilane 11. The spiroketal subunit of bistramide A was modified at the C39-alcohol to give another point of stereochemical diversification. The fragments were coupled by using a standard peptide coupling protocol to provide 35 stereoisomers of the natural product. These stereochemical analogues were screened for their effects on cellular actin and cytotoxicity against cancer cell lines (UO-31 renal and SF-295 CNS). The results of these assays identified one analogue, 1.21, with enhanced potency relative to the natural product, bistramide A.
Assuntos
Acetamidas/síntese química , Acetamidas/farmacologia , Actinas/antagonistas & inibidores , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Piranos/síntese química , Piranos/farmacologia , Acetamidas/química , Actinas/química , Antineoplásicos/química , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Modelos Moleculares , Conformação Molecular , Piranos/química , Compostos de Espiro/síntese química , Compostos de Espiro/química , Compostos de Espiro/farmacologia , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Development of modulators of constitutively active, kinase domain mutants of c-Kit has proved to be very difficult. Therefore, a high-throughput differential cytotoxicity assay was developed to screen for compounds that preferentially kill cells expressing constitutively active c-Kit. The cells used in the assay, murine IC2 mast cells, express either the D814Y activating mutation (functionally equivalent to human D816Y) or wild type protein. This assay is robust and highly reproducible. When applied to libraries of natural product extracts (followed by assay-guided fractionation), two differentially active compounds were identified. To assess possible mechanisms of action, the active compounds were tested for inhibitory activity against a panel of signaling enzymes (including wild type and mutant c-Kit). Neither of the compounds significantly affected any of the 73 enzymes tested. The effects of commercially available modulators of known signaling components were also assessed using the screening assay. None of these inhibitors reproduced the differential activity seen with the natural products. Finally, both compounds were found to affect mitochondrial potential in cells expressing c-Kit(D814Y). These results suggest that the newly identified natural products may provide new avenues for intervention in aberrant c-Kit signaling pathways.
Assuntos
Produtos Biológicos/farmacologia , Proteínas Proto-Oncogênicas c-kit/metabolismo , Transdução de Sinais , Animais , Linhagem Celular , Potenciais da Membrana/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Proteínas Quinases/metabolismo , Reprodutibilidade dos TestesRESUMO
A detailed analysis of four different collections of the sponge genus Zyzzya yielded nine pyrroloiminoquinones of the makaluvamine, batzelline, and isobatzelline/damirone classes. Dereplication analyses of additional Zyzzya extracts did not disclose more potent or additional new compounds. Comparative testing of these compounds in the National Cancer Institute's 60 cell line human tumor screen revealed varying levels of potency and differential cytotoxicity, apparently related to the unsaturation levels in and substitution patterns on the core ring system. Further studies on the topoisomerase II-mediated DNA cleavage were conducted. Reductive activation of the pyrroloiminoquinones led to DNA damage in vitro, which correlated with half wave potentials and reversibility parameters. DNA damage could be abrogated by ascorbate. Fluorescence displacement was used to measure intercalation with DNA; intercalation efficiency did not correlate with DNA-damaging proficiency. Makaluvamine H (5) emerged as the most potent and differential of our isolates, roughly comparable to makaluvamines C (in vitro) and I (in vivo). 3,7-Dimethyl guanine was isolated from one of the Zyzzya collections and from the sponge Latrunculia purpurea.