Pilot Project B: Synthesis and Preclinical Evaluation of Targeted, Iron-Based MRI Contrast Agents to Enhance Ovarian Cancer Detection and Treatment Scheduling
Co-Investigators
Jim Klostergaard, Ph.D., Professor, Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
Raphael Raptis, Ph.D., Professor, Department of Chemistry, University of Puerto Rico Comprehensive Cancer Center, Rio Piedras, Puerto Rico
More effective methods are needed for ovarian cancer detection and treatment management than are currently available, and we propose that with improved use of targeted contrast agents (CAs), magnetic resonance (MR) imaging could play a valuable role in monitoring (e.g., patients’ treatment response or initial relapse). In this proposal, we will synthesize and evaluate a novel series of Fe-based MR CAs to attempt to enhance detection of ovarian tumors disseminated to the peritoneum. The focus will be on human ovarian carcinoma/nude mouse xenograft models, using intraperitoneal (i.p.) implantation. These tumor models reflect numerous relevant aspects of the human disease, and they are high expressors of the cell-surface proteoglycan, CD44, which is over-expressed on as many as 90% of human ovarian carcinoma specimens. Hyaluronic acid (HA), a component of the peritoneal mesothelium, is a ligand of CD44, and as the lead formulation, HA will be formulated with a CA to create a targeted CA (HA-Fe8) to specifically bind to CD44+ tumors.
Specific Aims
- To evaluate the ability of non-targeted formulations of our proprietary lead Fe8-compound and its water-soluble conjugates to enhance MR imaging of i.p. human ovarian carcinoma xenograft models; these will include a) the directly water-soluble Fe8-CAs, b) a formulation of hydrophobic Fe8-CAs rendered water-soluble by use of a cyclodextrin excipient, and c) synthesis of new conjugates of the lead CA with carbohydrates, glucosamine and glucosyl bromide, to facilitate aqueous solubility. Further, to synthesize a novel HA-conjugate of a derivative of the lead CA; [to carry out preliminary, dose-finding toxicity assays on these CAs;] to determine whether this conjugate improves the MR imaging sensitivity of i.p. CD44+ ovarian carcinoma xenografts by comparison to the non-targeted complexes; to optimize formulation parameters such as stoichiometry, HA chain length, substitution of Fe8-compounds, to enhance MR imaging
- To develop/select thioaptamers with high affinity for CD44 family members, parental and/or splice variants. The aptamer(s) will have CD44 binding characterized and validated in vitro against the same human ovarian carcinoma cell line as will be employed in the xenograft model(s)
- To synthesize appropriate chemically functionalized derivatives of the lead Fe8-cluster, which will allow the attachment of new targeting groups. Guided by the results in Aim 1, to synthesize conjugates of the lead Fe8-compound coupled to high-affinity, anti-CD44 aptamers;[to carry out preliminary, dose-finding toxicity assays on these CAs;] to determine whether the CD44 aptamer-Fe8-cluster conjugate improves the MR imaging sensitivity of i.p. CD44+ ovarian carcinoma xenografts, by comparison to the HA-Fe8 CA, as well as to non-targeted CAs