Synthesis and bioevaluation of N-(arylalkyl)-homospermidine conjugates

Study on the synthesis, biological activity and spectroscopy of naphthalimide-diamine conjugates

Eleven novel naphthalimide-diamine conjugates were synthesized and their structures were confirmed by elemental analysis, 1H-NMR, 13C-NMR and MS. Their in vitro antitumor activities were assessed using MTT assays on two cancerous cell lines K562, HCT116, and one normal hepatoma cell line QSG 7701. Compound 7f exhibited potent antitumor activity on HCT116 cells and favorable cell selectivity toward QSG 7701 compared with the positive control, amonafide. Moreover, 7f could block HeG2 cells in the G2/M phase and induce HeG2 cells apoptosis. The interaction of compound 7f with herring sperm DNA was studied by UV/vis absorption and fluorescence spectroscopy under physiological conditions (pH = 7.4). The observed spectral quenching of compound 7f by DNA and the displacement of EB from DNA-EB complex by compound 7f indicated that compound 7f could intercalate into DNA base pairs, which was also corroborated by the effect of KI on compound-DNA interaction. Further caloric fluorescent tests revealed that the quenching mechanism was a static type. Meanwhile, the binding constants, thermodynamic parameters and the effect of NaCl on compound-DNA interaction showed that the type of interaction force was mainly hydrogen bonds and the binding process was driven by hydrogen and van der Waals bonding.

A putrescine-anthracene conjugate: a paradigm for selective drug delivery

Increased polyamine concentrations play an important role in the development of cancer at all stages, from initiation through to maintenance of the transformed phenotype. One way cancer cells accumulate increased concentrations of polyamines is by increased uptake of preformed polyamines via their PTS (polyamine transport system). The PTS is promiscuous and will transport a range of polyamine-based molecules. Therefore it may be that cytotoxic drugs could be attached to polyamine vectors and targeted selectively to cancer cells by utilizing the PTS. The aim of the present study was to investigate the potential of Ant 4, a putrescine-anthracene conjugate, to target cytotoxic agents to human cancer cells as a paradigm for a novel method of selective drug delivery. Ant 4 induced cytotoxicity after only 24 h exposure. Apoptosis was the predominant type of cell death, with mechanistic studies revealing that oxidative stress and DNA damage may have a part to play. For the first time, uptake of Ant 4 via the PTS was demonstrated both directly and indirectly in human cell lines. In addition, Ant 4 significantly reduced putrescine uptake, demonstrating that this conjugate not only used the PTS, but also could successfully compete with its native polyamine for uptake. However, the most interesting finding was the intracellular depletion of the polyamine pools, providing an additional mode of toxicity for Ant 4 and the possibility that this molecule may act as a 'double-edged sword': preventing cell growth by delivery of the toxic moiety and by depletion of intracellular polyamine content.

Conjugation of substituted naphthalimides to polyamines as cytotoxic agents targeting the Akt/mTOR signal pathway

Though several naphthalimide derivatives have exhibited antitumor activity in clinical trials, some issues such as toxicity prompted further structural modifications on the naphthalimide backbone. A series of naphthalimides conjugated with polyamines were synthesized to harness the polyamine transporter (PAT) for drug delivery, which was beneficial for the tumor cell selectivity. Bioevaluation in human hepatoma HepG2 cells treated with alpha-difluoromethylornithine (DFMO) or spermidine (Spd), human hepatoma Bel-7402 and normal QSG-7701 hepatocyte confirmed the PAT recognition and cell selectivity. In addition, the novel naphthalimide polyamine conjugate kills cells via apoptosis, and the Akt/mTOR signal pathway was first identified as the upstream cellular target through the apoptotic mechanism research. The presence of DFMO or Spd only either elevated or attenuated the cell apoptosis, but did not change the signal pathway. Collectively, the proper polyamine recognition element (i.e., homospermidine) mediated effective drug delivery via the PAT, and helped the proper cytotoxic goods (i.e., diverse naphthalimides) exert antitumor properties.