Development of pseudosubstrate-based peptide and peptidomimetic inhibitors of p60ᶜ⁻ˢʳᶜ protein tyrosine kinase using combinatorial chemistry technology

Abstract

Several protein tyrosine kinases and the signaling pathways in which they participate have emerged as attractive targets for drug design. Specific and potent PTK inhibitors not only represent a new class of anticancer agents but may also be used as a powerful research tool to study the role of PTK-dependent cellular pathways in normal or tumor cell growth and to dissect the redundancy in signal transduction pathways. Dr. Lam's laboratory has previously reported identification of efficient and specific peptide substrates for p60ᶜ⁻ˢʳᶜ PTK using one-bead one-peptide combinatorial library method (Lam et al., 1995; Lou et al., 1996a and b). Based on the structure of these peptide substrates, I have identified and characterized potent and selective peptide inhibitors of p60ᶜ⁻ˢʳᶜ PTK. Some of the identified peptide inhibitors were used as a research tool in this dissertation to investigate the active site of the enzyme p60ᶜ⁻ˢʳᶜ PTK. In addition to potency and selectivity, a major criterion for a successful src inhibitor is its cell permeability as src is located inside the cell. Peptides are generally impermeable to cell membrane. A major accomplishment of this dissertation is development of cell permeable peptidomimetic inhibitors of p60ᶜ⁻ˢʳᶜ PTK based on the identified dipeptide motif --Ile-Tyr- (-I-Y-). This dissertation describes identification of tetrameric and trimeric peptidomimetic inhibitors using a combination of two combinatorial methods, the 'one-bead one-compound' combinatorial method and the 'iterative' combinatorial method. Some of the identified inhibitors seem to selectively affect transformed cells versus normal cells at lower concentrations. A lot of still needs to be done to optimize these inhibitors. However, the accomplished work in this dissertation proves the feasibility of the pseudosubstrate peptide-based approach for the development of cell permeable peptidomimetic inhibitors as anti-cancer therapeutic agents.