One of the most challenging problems in the use of drugs for the treatment of diseases is of specificity. While clinically active agents used in the treatment of cancer often rely on inhibition of nucleic acid metabolism, the action is non-selective and produces side effects of varying severity. Certain N-mustards has been shown to exhibit enhanced reactivity with GC rich regions in DNA fragments which could explain their effectiveness against a number of cancers. The above findings point to the possibility of design of alkylating agents to optimize the selectivity of reaction with critical GC rich regions. Recent advances in the investigator's understanding of molecular recognition of oligopeptides, such as netropsin and distamcyin, together with the advent of new DNA sequencing and footprinting technology, high field NMR, molecular modeling, permit the design of sequence selective agents. Therefore, the main focus of this project is to develop minor groove DNA binding-alkylating agents to specific base sequences and thereby produce new drugs that might be more effective clinically in cancer treatment. These DNA sequence specific ligands can also be employed as gene control agents to modulate gene expression, including that of oncogenes. The AT sequence and minor groove specific binding oligopeptides, distamycin A and netropsin, are used as models for the development of new ligands that would recognize and bind to GC and mixed AT/GC sequences of up to 7-8 base pairs. These agents will, then, be used as vectors for DNA interactive functionalities such as N-mustards. The investigators group has recently synthesized imidazole containing analogs of distamycin which contain a bischloroethylaminobenzoyl group on the N-terminus. They were shown to have significant in vitro activity against K562 human myelogenous leukemia. CEM, and L1210 cells, and in vivo studies against L1210 and M5076 reticular sarcoma are in progress. The proposed research involves the rational design and synthesis of analogs of distamycin that can bind to long (greater than 8 bp) GC rich sequences. The strategy includes the preparation of polyimidazole analogs of distamycin, and analogs wherein the imidazole-containing fragments are linked with a flexible polymethylene chain (N-to-N termini, C-to C termini and N-to-C termini). Optimized DNA sequence specific binding ligands will be conjugated with a number of alkylating agents including N-mustards. Synthetic efforts will guided by the principles of drug design and results of parallel DNA binding experiments including MPE footprinting, H-NMR, CD, UV-vis, fluorescence, molecular modeling studies and anticancer screening (both in vitro and in vivo). DNA alkylation will be studied by gel electrophoresis, CD and dialysis experiments. The long-term goal of this work is to develop fully sequence specific minor groove alkylators to sensitive GC rich cellular targets including oncogenes and key control regions for superior anticancer activity.
| Lee, M; Preti, C S; Vinson, E et al. (1994) GC sequence specific recognition by an N-formamido, C-terminus-modified and imidazole-containing analogue of netropsin. J Med Chem 37:4073-5 |
