Abstract LB-022: Real-time intraoperative tumor imaging in a breast cancer PDX model
Authors: Goto Masahide , Ryoo Ingeun , Naffouje Samer , Christov Konstantin , Wang Jing , Green Albert , Shilkaitis Anne , Gupta Tapas K. Das , Yamada Tohru 
Published: September 2020

Breast cancer is one of the most common types of cancer diagnosis in women of all ages. The primary treatment of breast cancer is surgical excision of the tumor with the margin of normal breast tissue surrounding the tumor. However, current clinical goals include complete resection of the tumor at the initial surgery, there is often a need for further surgery and removal of more tissue due to the difficulties inherent in getting negative margins. Therefore, there is a clinical need to optimize the excision by precisely identifying tumor margins significantly benefitting patients with breast cancer. Image-guided surgery with fluorescent agents provides surgeons numerous advantages such as real-time detection with a high-resolution image and relatively flexible instrument. We have developed a unique tumor-targeting fluorescence imaging agent. We identified a cell-penetrating peptide (CPP) p28, a fragment of azurin isolated from opportunistic pathogen Pseudomonas pathogen. p28 was chemically conjugated with Indocyanine green (ICG), a near-infrared red (NIR) fluorescent agent. ICG has been approved by the FDA for clinical applications with an excellent safety record. When p28 was conjugated to ICG, there was no significant alternation of fluorescence quantum yield (ΦF) of ICG-p28 compared to ICG alone. Triple-negative (ER, PR, HER2) human breast cancer PDX mouse model in NSG mice was used to evaluate the image-guided surgical procedure with ICG-p28. After 24h of ICG-p28 injection i.v. opportunistic 0.5 mg/kg b.w., NIR-fluorescence positive mammary tumors with a 2-mm safe margin were resected under real-time guidance of the PDE imaging unit (Mitaka USA, Hamamatsu Photonics). NIR-fluorescence negative surrounding tissues of at least two different sites (superior and inferior) were also collected separately. To validate the accuracy of tumor margin identification by the image guidance, Alu-based real-time PCR analysis was used for the quantitative detection of human cancer cells. Five ng of genomic DNA obtained from tumors and surrounding tissues were subjected to RT-PCR. Ct values were normalized by the housekeeping gene, mouse GAPDH. Our results showed that preclinical intraoperative imaging with our imaging agent, ICG-p28 at 0.5 mg/kg, significantly reduced positive margin as compared to control groups (e.g. ICG alone, p&lt;0.01). In conclusion, nontoxic p28 is a potentially ideal CPP that can serve as a tumor-targeting carrier for an intraoperative imaging agent. Results suggest that our imaging approach will potentially provide a significant impact on resection procedure benefitting patients with breast cancer.

Citation Format: Masahide Goto, Ingeun Ryoo, Samer Naffouje, Konstantin Christov, Jing Wang, Albert Green, Anne Shilkaitis, Tapas K. Das Gupta, Tohru Yamada. Real-time intraoperative tumor imaging in a breast cancer PDX model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-022.