Abstract 4937: Fluorescence imaging using Clostridium Perfringens Enterotoxin carboxi-terminal fragment (c-CPE) to target metastatic chemotherapy-resistant human ovarian cancer in xenograft mice

Abstract

Abstract Epithelial ovarian cancer is the most lethal gynecologic malignancy. It is treated through up front surgery followed by chemotherapy or with neoadjuvant chemotherapy before surgical debulking. Achieving complete or optimal cytoreduction improves both progression free and overall survival. In the operating room, no matter the care taken, there is the potential for areas of macroscopic, microscopic and occult metastases to remain unvisualized. The development of a sensitive and specific intraoperative system for the visualization and removal or destruction of metastatic disease may improve patient outcome. Fresh ovarian cancer samples were recently analyzed by our group with genetic fingerprinting. This analysis revealed high expression of claudin-3 and -4, the epithelial receptors for Clostridium Perfringens Enterotoxin (CPE). Although the administration of the full length CPE in mice is toxic, the injection of the only carboxi-terminal fragment (c-CPE) avoids toxicity while preserving the binding to the receptors. Our previous data showed specific binding of FITC conjugated c-CPE (FITC-c-CPE) to primary ovarian cancer cell lines in vitro as well as preferential accumulation of the labeled peptide into ovarian cancer xenografts in vivo. This study evaluates the in vivo distribution of FITC-c-CPE after intraperitoneal (IP) injection of the peptide as well as the kinetics and tumor binding capacity of c-CPE conjugated to the NearInfraRed Dye CW800 (CW800-c-CPE), focusing on the ability of CW800-c-CPE to identify metastases of chemotherapy-resistant ovarian cancer overexpressing claudin-3 and -4 in vivo. We found that fluorescence uptake by the tumor starts 30 minutes after FITC-c-CPE injection with negligible staining of healthy organs. When the abdominal cavity of FITC-c-CPE injected mice was visualized using a fluorescence microscope, strong signal was detected in near microscopic metastatic nodules and in malignant tumor spheroids isolated from the ascites. Similarly, CW800-c-CPE also accumulated in tumors in vivo following IP or systemic (IV) injection. Ex vivo distribution analysis demonstrated a significantly higher mean fluorescence intensity (MFI) in tumor compared to healthy organs (MFI: mean ± STDV: 156.55 ± 23.73, 95.72 ± 18.19, 30.68 ± 5.88, 23.33 ± 4.05, 34.71 ± 12.71, 28.16 ± 6.1413.46 ± 1.35, 19.78 ± 5.43 in the tumor, kidney, liver, spleen, bowel, lungs and brain, respectively; p<0.01). The accumulation of CW800-c-CPE was also noted in small size tumor implants in the abdomen. These data suggest that c-CPE has tremendous specificity for targeting metastatic chemotherapy-resistant ovarian cancer in vivo. Furthermore, the c-CPE peptide has the potential to be implemented into the operative setting to allow for improved detection of residual tumor during staging and cytoreductive surgery for ovarian cancer patients. Citation Format: Emiliano Cocco, Sara Gasparrini, Erik M. Shapiro, Carlton Schwab, Stefania Bellone, Ileana Bortolomai, Salvatore Lopez, Natalia J. Sumi, Elena Bonazzoli, Roberta Nicoletti, Yang Deng, William M. Saltzman, Caroline J. Zeiss, Dan-Arin Silasi, Thomas J. Rutherford, Peter E. Schwartz, Alessandro D. Santin. Fluorescence imaging using Clostridium Perfringens Enterotoxin carboxi-terminal fragment (c-CPE) to target metastatic chemotherapy-resistant human ovarian cancer in xenograft mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4937. doi:10.1158/1538-7445.AM2014-4937