The goal of this project is to develop targeted therapeutic carriers for the treatment of solid tumors. Targeted drug delivery increases the specificity and efficacy of cancer therapy and thus reduces damage to normal tissues that is associated with conventional chemotherapy. The proposed carrier is a genetically-engineered, thermally responsive polypeptide that inhibits the proliferation and growth of cancer cells. The amino acid sequence of the polypeptide carrier is based on elastin-like biopolymers that are soluble below 37 degree celsius, but aggregate at temperatures above 41 degree celsius. This characteristic can be exploited to thermally target the drug carrier to the solid tumor site. In addition to the elastin-like polypeptide carrier, the drug delivery vehicle is genetically engineered to contain a short peptide, Bactenecin, that facilitates cell entry, and a peptide derived from the cyclin-dependent kinase inhibitor p21, which inhibits the cell cycle and cell growth.
By applying local heat to solid tumors, these polypeptides can be targeted to and accumulate at the tumor site, inhibiting cancer cell growth. To address this hypothesis, the following specific aims will be addressed: 1) measure the plasma kinetics and in vivo distribution of the drug in normal and cancerous tissue and 2) evaluate the therapeutic efficacy of this drug in the treatment of ovarian tumors in mice through repeated administration of the agent when the tumor is heated and unheated. This research will provide the in vivo data necessary to move this therapy towards the translational stage of human therapeutics.
In order to fulfill these scientific aims, a highly structured program will be created to recruit undergraduate students, especially minorities and members of underrepresented groups, to this collaborative research endeavor. The state of Mississippi has the largest percentage population of African American citizens of any state in the United States, yet remains well below national and southern state averages in enrollment of African American students into and graduation from doctoral programs within the state. Active research experience is one of the most effective ways to attract talented undergraduates to and retain them in careers in research and medicine. Therefore talented undergraduate students will be recruited from Tougaloo College and will participate directly in the creation of this drug delivery vehicle and in the implementation of the specific aims of this project.
Intellectual Merit: Tumor tissue is known to differ from normal tissue in many features. Tumor blood vessels have larger intercellular pores than normal blood vessels, as well as impaired lymphatic drainage, which together result in an impaired elimination of macromolecules from tumors and longer retention in tumor interstitial space. This phenomenon, referred to as the enhanced permeability and retention (EPR) e?ect, is the basic foundation for the passive targeting of many macromolecular drug delivery systems. These macromolecular systems exploit the EPR effect to increase active drug concentration in tumors while limiting damage to normal tissue. Our approach is to deliver therapeutics to tumor sites using Elastin-like polypeptides (ELP). ELPs are thermally responsive polypeptide carriers that are soluble in aqueous solutions at physiological temperature (37° C). However, when a temperature is raised above the ELP’s transition temperature (Tt, 41° C), these polypeptide carriers aggregate. We have shown that our polypeptide carriers can inhibit tumor growth when targeted to a tumor site through applications of local hyperthermia that result in such aggregation. As molecular size is a key determinant of trans-vascular transport for tumor therapeutic agents, we designed and evaluated, for the present study, three ELP macromolecules of varying molecular weights (36, 63, and 122 kDa) with the goal of optimizing our ELP drug delivery system. The N-terminus of the ELP macromolecules was modified with a cell penetrating peptide, Bac, to enhance intratumoral and intracellular uptake. In distribution studies using pancreatic tumor bearing mice, all three macromolecular carriers exhibited increased tumor uptake after applications of local heat; however, elimination patterns from tumors differed among them. Local hyperthermia was found to produce prolonged retention of all ELP conjugates in tumors except 36 kD ELP. In addition, pharmacokinetic analysis showed that polypeptides with MW 63 and 122 kDa have an increased area under the plasma concentration time curve in comparison with the polypeptide with MW 36 kDa. These results suggest that the larger ELP conjugates (63 and 122 kDa) have advantages over the smaller 36 kD ELP polypeptides in terms of their enhanced permeability and retention effects. These studies suggest that molecular weight must be carefully considered to fully exploit the tumor targeting properties of ELPs and that ELPs larger than 36 kDa appear to be optimal for enhanced accumulation in tumor tissue in combination with local hyperthermia. Broader Impacts: Mississippi remains well below national and southern state averages in African American enrollment into and graduation from state doctoral programs, despite having the largest percentage population of African American citizens in the United States. Three key factors contribute to this continuing problem: A lack of information at secondary levels about opportunities in science and medicine that further stress preparation for their educational and career paths, few structured programs in biomedical research and, concomitantly few collaborative mentorship opportunities targeted to underrepresented minority groups. Active engagement with a research laboratory is the single, most effective way to attract and retain talented undergraduates with an interest in research and medical careers. Such engagement adds to hands-on training the mentoring, monitoring of progress, and provision of timely and supportive feedback that can motivate and encourage student retention. Toward this end, our laboratory has established a highly structured and collaborative research program that provides mentoring, monitoring, and feedback for underrepresented minority students, as well as those who are women. Undergraduates recruited through the Research Experience Opportunity (REO) program of the Mississippi Functional Genomic Network (MFGN) and the Summer Undergraduate Research Experience (SURE), established by the School of Graduate Studies in the Health Sciences at the University of Mississippi Medical Center, first engage their project’s specific aims through direct mentorship by the project director and senior lab members. Their structured research training includes basic molecular biology, cell biology and basic animal experimental technique, in line with their particular project contributions. Experimental design and data analysis are discussed in weekly meetings designed to review each student’s research, foster peer evaluation skills, and provide exposure to the range of research activities underway at our institution that might provide opportunities for future career investigations.
