Effect of Spermine Conjugation on the Cytotoxicity and Cellular Transport of Acridine

Abstract

Polyamines are believed to be potent vectors for the selective delivery of chemotherapeutic agents into cancer cells. In this paper, we report the effect of spermine conjugation on the cytotoxic and transport properties of acridine. Six derivatives, composed of a spermine chain attached at its N(1) position to an acridine via an aliphatic chain, were synthesized. The aliphatic linker, comprised of 3-5 methylene units, was connected to the position-9 of the heterocycle through either an amide (amidoacridines 8-10) or an amine (aminoacridines 11-13) linkage. Independently of their architecture, all ligands showed a high affinity for DNA binding but a limited DNA sequence selectivity. In a whole cell assay with L1210 and Chinese hamster ovary (CHO) cells, the aminoacridines (IC(50) values around 2 microM) were more potent than the amidoacridines (IC(50) values between 20 and 40 microM). This was related to a less efficient transport for the latter. As determined from competitive uptake studies with [(14)C]spermidine, all conjugates had a high affinity for the polyamine transport system (PTS). However, on the basis of competitive studies with an excess of spermidine and on the differential effect on cell growth and accumulation in CHO and in the mutant PTS deficient CHO-MG cells, the accumulation of the conjugates through the PTS was found to be poor but still more efficient for the aminoacridines. alpha-Difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, which induces an up-regulation of the activity of the PTS, enhanced accumulation of all acridine conjugates through the PTS and had a synergistic effect on the potency of the acridine conjugates to inhibit cell growth. Despite their high affinity for the PTS, the low amount of derivatives transiting through the PTS is likely to be related to their ability to repress rapidly and efficiently the activity of the PTS and, consequently, to inhibit their own uptake via this system.

F14512, a Potent Antitumor Agent Targeting Topoisomerase II Vectored into Cancer Cells via the Polyamine Transport System

“…This property has already been used to strengthen the activity of several DNA-damaging agents, including topoisomerase II poisons (20,48). In this context, one can expect to increase the stability of epipodophyllotoxin/DNA/topoisomerase II ternary complexes by a stronger interaction of DNA with the positively charged polyamine chain.…”

“…The antiproliferative effects of F14512 and etoposide have been evaluated according to a procedure described previously (20). Briefly, murine leukemia L1210 cells were cultivated in 96-well plates in the presence of F14512 or etoposide at appropriate concentrations and 500 Amol/L putrescine, 100 Amol/L spermidine, 50 Amol/L spermine, or physiologic saline as control in a medium containing 2 mmol/L aminoguanidine.…”

“…Based on this, polyamine vectorization was proposed as a valuable strategy to increase the selectivity of anticancer agents. The literature reports several examples of polyamine conjugates with cytotoxic drugs, such as chlorambucil (17), nitroimidazoles (18), aziridines (19), acridines (20), enediyenes (21), anthracenes (16), naphtoquinones (22), camptothecin (23), and protoberberine (24). All these conjugated drugs are DNA-interacting agents used to develop a general strategy by exploiting both the transport mechanism and the high affinity of polyammonium cations for DNA.…”

Antitumoral activity of new polyamine-naphthoquinone conjugates

“…Thus, tagging spermidine analogues to a chemotherapeutic agent may enhance their activity either by facilitating uptake (via polyamine uptake systems) or by competition with polyamines for 'critical binding sites' in the cells. Indeed, it was demonstrated that linkage of polyamines to cytotoxic compounds facilitates their entry into tumor cells possessing a polyamine uptake system and increases their selectivity to DNA (8). Thus, the ability of the bifunctional alkylating agent chlorambucil, to form interstrand crosslinks with double stranded DNA, increased 10 4 -fold after conjugation with spermidine (9).…”

Biological Properties of IDN5174, a New Synthetic Camptothecin with the Open Lactone Ring

“…The polyammonium cations have proved to favor the interaction with the negatively charged phosphates of the DNA backbone maintaining a high degree of translational freedom along the polyanion backbone, thus conferring a high DNA affinity without modifying the capability of the drug to locate appropriate sites of DNA (11). Conjugation of a cytotoxic drug to polyamines gave successful conjugates with chlorambucil (12)(13)(14), nitroimidazole (15,16), aziridines (17)(18)(19), acridine (20), and enediynes (21), with enhanced cytotoxicity and/or increased drug selectivity for tumor cells.…”