G-quadruplex ligands for cancer therapy

• Autor(a) principal: Silva, João Medeiros
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/15840
• topic: DNA; G-quadruplex; Oligoheteroaryle compounds; Molecular recognition; Anti-cancer drugs; Ligand-receptor interaction; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

DNA may fold into a diversity of structures and topologies such as duplexes and triplexes. Some specific guanine-rich DNA sequences may even fold into a higher order structures denominated guanine G-quadruplexes (G4). These G-quadruplex forming sequences have shown biological interest since were found in telomeres and in promoter region of oncogenes. Thus, these G4 forming sequences have been explored as therapeutic targets for cancer therapy, since G4 formation was demonstrated to inhibit RNA-polymerase and telomerase activity. However, the G4 structures are transient and are only formed under specific conditions. Hence the main objective of this work is to develop new G4-specific ligands which may potentially find applications in the therapeutic area. Several potential G4-binding ligands were synthesized and characterized. The synthesis of these compounds consisted on a procedure based on van Leusen chemistry and a cross-coupling reaction through C-H activation, affording phenanthroline compounds (Phen-1, 50%; Phen-2, 20%), phenyl (Iso-1, 61%; Iso-2, 21%; Ter-1, 85%; Ter-2, 35%), and quinolyl (Quin-1, 85%; Quin-2, 45%) compounds. Screening assays for selecting the potential G4 compounds were performed by FRET-melting, G4-FID, CD-melting and DSF. Qualitative biophysical studies were performed by fluorescence and CD spectroscopy. Two high-specific G-quadruplex ligands, Phen-1 and Phen-2, were found to effectively bind telomeric and c-myc G4 structures. Phen-1 was found to stabilize parallel telomeric 22AG and c-myc sequence by 4.1 and 4.3 ˚C, respectively. Phen-2 also displayed high affinity towards 22AG (=9.56×109 −1) and to c-myc (=3.55×106 −1), increasing their thermal stability by 15.0 (in K+) and 31.0 ˚C, respectively. The compounds were evaluated concerning their anti-proliferative effects on three cancer cell lines (MCF-7, LNCaP and U87) and normal cell line (NHDF), by MTT assay. Phen-2 and Quin-2 displayed strong anti-proliferative effects on LNCaP (IC50 = 0.40 and 39.14 μM, respectively) and MCF-7 (IC50 = 0.64 and 4.17 μM, respectively) cancer cell lines. Furthermore Quin-2 did not display cytotoxic effects on U87 and normal NHDF cells. Overall, this work explored new possibilities for finding new G4 ligands for cancer therapy.