Cancer is the second leading cause of death in the United States. Nearly half of all men and a little over one third of all women in the United States will develop cancer during their lifetimes. The a5?1 integrin and its ligand fibronectin have been implicated in suppressing tumor recurrence and metastasis in different tumor cells, including colon cancer (the third most common cancer in this country). In recent years there is a considerable effort to designing fibronectin-mimetic peptides that will target the integrin with increased therapeutic potentials. The PI has synthesized a novel peptide-amphiphile that contains both GRGDSP (the primary recognition site for a5?1), and PHSRN (the synergy site for a5?1) in a single peptide formulation that shows increased cell adhesion compared to other GRGDSP surfaces, and fibronectin. The objective of this proposal is to engineer a5?1-targeted stealth liposomes that will be stable, and will function as a platform for interactions with the a5?1 integrin. The central hypothesis of this application is that stealth liposomes functionalized with the novel peptide will show more efficient and specific binding to a5?1 integrin compared to stealth liposomes decorated with GRGDSP, or with no peptide. The efficacy of the design will be tested with in vitro studies with colon carcinoma cells that express high levels of the integrin. To test this hypothesis, and accomplish the objective of this proposal, the following two aims have been set.
Specific Aim 1 : Engineering of pH-sensitive a5?1-targeted stealth liposomes. These formulations will specifically bind to a5?1, get endocytoced, and release the load (toxic anticancer drugs, chemotherapy agents, or DNA) in an acidic pH environment. Studies will be carried out by flow cytometry, plate assays, and confocal microscopy using different fluorescent probes.
Specific Aim 2 : Engineering of phospholipase A2 (PLA2)-sensitive a5?1-targeted stealth liposomes. The objective here is to specifically target the integrin, and deliver the encapsulated load (a5?1 antagonists that inhibit tumor angiogenesis, tumor growth and metastasis) as a result of liposomal hydrolysis due to the PLA2 presence at the cancerous site. Different formulations will be evaluated via flow cytometry, and fluorescent studies with different fluorophores. Our novel peptide-amphiphile, will allow for the development of new pharmacological strategies for the prevention and treatment of a variety of other diseases where a5?1 is up-regulated. ? ? ? ?
