Targeting Tumor-Associated Neovasculature For Delivery Of Optical Enhancers Detects Ovarian Cancer Micrometastasis

Background: Patients with epithelial ovarian cancer have the best overall survival when maximal surgical effort is accomplished. While identification and removal of large metastases do not pose a challenge, micrometastases are impossible to distinguish intra-operatively and contribute to the high mortality. Our objective is to develop specific tumor-targeting optical enhancers that can aid surgeons in the performance of microscopic tumor debulking with the goal of minimizing microscopic residual disease. We hypothesize that we can utilize overexpressed αVβ3 integrins in the tumor-associated neovasculature. Specific targeting is achieved by encapsulating fluorescent probes in FDA-approved PLGA-based nanoparticle (NP) coated with the peptide sequence arginine-glycine-aspartate (RGD), which binds with high affinity to these integrins. Materials and methods: Ovarian cancer xenograft is established intra- peritoneally (i.p.) in nude mice using cancer cells that stably express mCherry fluorescent protein. The following formulations were tested: soluble deep infrared dye (DIR), DIR encapsulated in naked NP (DIR-NP), and DIR encapsulated in RGD-coated NP (DIR-RGD-NP). Formulations were delivered i.p. and colocalization of fluorescent signals were determined ex vivo. Staining of micrometastasis was visualized using fluorescent dissection microscope. Results: The best colocalization was observed in mice administered DIR-RGD-NP. We observed 75% colocalization in this group compared to 26% and 0% in DIR-NP and DIR groups, respectively. Ex vivo analysis of DIR intensity in tumors less than 2 mm showed mean fluorescent intensity (MFI) of 1209 in DIR-RGD-NP group versus 155 MFI DIR-NP group. Based on DIR staining, we can locate 81% of mCherry+ micrometastasis in animals administered DIR-RGD-NP. In these animals, tumors less than 1 mm were detected due to a halo of DIR staining around each micrometastatic lesion. In these foci, DIR signal was observed to stain the vasculature surrounding the small tumor implants especially those in the mesentery and diaphragm. In contrast, we were able to detect only 18% of the mCherry+ micrometastasis in animals administered DIR-NP. Conclusion: We demonstrate that we can utilize the specific phenotype of tumor-associated neovasculature to target optical enhancers to locate and delineate micrometastasis. RGD-coated nanoparticles are able to carry probes to the tumor microenvironment leading to optimal staining of micrometastasis. Our results highlight the use of this nanotechnology platform in microscopic surgical debulking to assure maximal surgical effort, minimize residual disease, and improve patient survival. Citation Format: Ayesha B. Alvero, Eydis Lima, Dongin Kim, Sean Orton, Natalia Sumi, Mary Pitruzzello, Yang Yang-Hartwich, Dan-Arin Silasi, Tarek Fahmy, Gil Mor. Targeting tumor-associated neovasculature for delivery of optical enhancers detects ovarian cancer micrometastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4201.