Abstract 1399: Ex-vivo targeting of urothelial carcinomas by fluorescent pHLIP imaging agents

Abstract Introduction: The detection of urothelial carcinomas of the bladder and upper tract is not satisfactory. Incomplete findings by contemporary imaging modalities provide a challenge in patient care, so there is a definitive need to improve diagnosis and treatment methods for urothelial carcinomas. Experimental procedures: ICG (indocyanine green) near infrared fluorescent (NIRF) dyes were conjugated with a pH-Low Insertion Peptide (pHLIP®), which senses and targets the acidity at the surfaces of cancer cells. In a few cases IR800 pHLIP® was used. Urinary neoplasm (kidney, ureter and bladder) specimens obtained through radical surgery were irrigated and incubated ex-vivo with ICG pHLIP® followed by fluorescence imaging. Pathology findings were correlated with the ICG pHLIP® NIRF imaging. Results: In the upper urothelial tract, nine of ten patients with nephroureterectomy had urothelial carcinomas (UTUC). Eighteen (100%) malignant lesions were found in NIRF imaging. Only thirteen (72%) of malignant lesions were found under white light macroscopic examination. ICG pHLIP® NIRF imaging gave a 28% increase in diagnosis of UTUC in ex-vivo specimens. There was no non-specific uptake in the non-tumoral tissue. The ICG pHLIP® imaging agent identified malignant upper tract urothelial lesions with 100% specificity and sensitivity. In the lower urinary tract, thirty-eight radical cystectomy specimens were incubated with pHLIP® conjugated with one of the NIRF dyes (ICG or IR800). In the thirty-eight bladders, eighty-one lesions were identified using fluorescent pHLIP®(specificity (97%) and sensitivity (100%)). White light cystoscopy did not detect 20.5% of lesions identified under NIRF cystoscopy (p<.001). Normal tissue did not show any uptake by the construct; however, entrapment of the dye in the necrotic tumor bed was noted. All regions showing the NIRF signal of pHLIP® were confirmed by standard pathological analysis. Conclusions: The ICG pHLIP® NIRF revealed additional lesions not seen with white light ex-vivo cystoscopy or preoperative ureteroscopy. pHLIP® based agents promise to improve diagnostic accuracy for urothelial carcinomas and may enable targeted treatment. Citation Format: Borivoj Golijanin, Anna Moshnikova, Donald M. Engelman, Oleg A. Andreev, Yana K. Reshetnyak, Ali Amin, Dragan Golijanin. Ex-vivo targeting of urothelial carcinomas by fluorescent pHLIP imaging agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1399.