Molecularly Targeted Probes for Photodynamic Therapy and Imaging of Breast Cancer

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Summary: Molecularly Targeted Probes for Photodynamic Therapy and Imaging of Breast Cancer The goal of this proposal is to test the hypothesis that small, peptide-based molecularly targeted probes containing a near infrared (NIR) dye and a photosensitizer (PS) dye will be effective for fluorescence imaging and photodynamic therapy (PDT) of breast cancer (BrCa). This novel treatment method will give patients access to an unprecedented therapy option, without the burden of side effects from traditional BrCa therapy. In particular, the application to fluorescence-guided lumpectomy combined with PDT in the same operation is envisioned as a remedy for the current epidemic of re-operation as it will provide a means of effectively treating residual BrCa cells in the margins. The strategy relies on a targeting deca-peptide, 18-4, reported to be an effective targeting agent for the keratin receptor, KRT1, a biomarker that is independent of hormone expression in BrCa cells. Students in our labs have developed a synthesis of 18-4 by a solid phase peptide synthesis (SPPS) and have merged that with a modular method we developed for the synthesis of BrCa-targeted molecular imaging agents (TMIAs). This method will provide analogous molecularly targeted photosensitizer (MTPS) probes for PDT and dual TMIA-MTPS probes for guiding surgery and PDT. Students at RIT will use confocal fluorescence microscopy (CFM) to evaluate the affinity of the 18-4-based TMIAs and dual TMIA-MTPS probes to two triple negative BrCa cell lines, MDA-MB-231 and EMT6, utilizing non-cancerous MCF10A as a control. The in vitro efficacy of PDT in the same cell lines will next be investigated using a single MTPS probe. To ensure that single MTPS and dual TMIA-MTPS probes are equally effective, PDT will be investigated in vitro in the MDA-MB-231 and EMT6 cells lines, using a laser supplied by our collaborator at the U of R. The mechanism of cell death will be studied using CFM and apoptosis assays. The strategy includes testing the binding affinity of the single and dual probes to EMT6 tumors in mice by in vivo NIR imaging, then testing efficacy in PDT experiments after systemic injection of the targeted dual TMIA-MTPS probe. Therapy will be monitored by tumor dimensions and stereo-fluorescence microscopy to verify efficacy of targeted and untargeted probes, with and without PDT. The combined in vitro and in vivo experiments will provide an effective strategy to develop single and dual probes for the PDT of BrCa. A key aspect of this proposal is the participation of three undergraduates from RIT in each year, one of whom will participate in the in vivo testing at the U of R, one in synthesis and one in the in vitro analysis at RIT. The collaboration highlights expertise in synthesis, cell biology, and confocal microscopy at RIT, and in cancer imaging and photodynamic therapy at the U of R. These combine to provide a vibrant learning environment in cancer research for undergraduates, with the achievable goal of revolutionizing treatment of BrCa by developing small, peptide-based TMIA, MTPS, and dual TMIA-MTPS probes to transform BrCa therapy by the use of molecularly targeted fluorescence-guided PDT and provide a breakthrough in the treatment and cure for BrCa patients.