title: Synergism through direct covalent bonding between agents: a strategy for rational design of chemotherapeutic combinations.
abstract: Self-assembling chemotherapeutic agents are mixtures of relatively nontoxic precursors that can combine chemically under physiological conditions to form products with greater cytotoxic and/or antimicrobial activity than either of the precursors. Combinations that form products more rapidly in or near the target (tumor, pathogen, virally infected cell) than in normal tissues will exhibit target-selective synergism, thus exhibiting an antitarget selectivity that is greater than the selectivities of the product (e.g., a hydrazone) and of either precursor (e.g., a hydrazine derivative or ketone) used singly. This paper describes the target-selective cytotoxic synergism of a cationic aldehyde (A) and a cationic acylhydrazine (B) containing a triarylalkylphosphonium moiety against Ehrlich ascites carcinoma cells (ELA) in culture, in addition to reviewing previous work on self-assembling cytotoxins. The synergism between A and B is carcinoma selective when the ELA cells (the target) are compared to CV-1, an untransformed African green monkey kidney epithelial line. Like tetraphenylphosphonium and rhodamine 123, which are selectively concentrated in ELA cells relative to CV-1, A, B and the hydrazone C resulting from their reaction are lipophilic delocalized cations that selectively inhibit ELA growth relative to CV-1 growth. The hydrazone C is more growth inhibitory than either A or B for both cell lines. A combination of A with an unreactive analogue of B and a combination of B with an unreactive analogue of A did not synergistically inhibit ELA proliferation. The degree of synergism is greater against the ELA cells than against the CV-1 cells. These data, together with hydrazone formation kinetics, suggest that A and B are both concentrated together selectively inside the ELA due to the transmembrane potentials, reacting inside the ELA cells at a higher velocity than inside the CV-1 cells to form the more growth-inhibitory hydrazone C.
authors.affiliation: Research Institute of Scripps Clinic, La Jolla, California 92037.
authors.forename: D
authors.initials: D
authors.lastname: Rideout
authors.forename: T
authors.initials: T
authors.lastname: Calogeropoulou
authors.forename: J
authors.initials: J
authors.lastname: Jaworski
authors.forename: M
authors.initials: M
authors.lastname: McCarthy
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D015195:Drug Design; D004357:Drug Synergism; D008564:Membrane Potentials; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents