Abstract 5431: FGF7 peptide (FGF7p) mimetic mitigates urothelial injury from cyclophosphamide or radiation
Authors: Narla Sridhar , Rice Lori P. , Ostrov David , Swarts Steven G. , Siemann Dietmar W. , Bates Carlton M. 
Published: June 2022

Background: Hemorrhagic cystitis from chemical or radiation bladder injury can cause life-threatening bleeding and/or urothelial cancer. Fibroblast growth factor 7 (FGF7) blocks urothelial apoptosis induced by cyclophosphamide (CPP) or radiation, but there are limitations to its use in patients, including an inability to apply it by direct bladder infusion and the high cost due to the large size of the protein (18.8 kDa).

Purpose: We previously identified a small peptide that equaled or exceeded the mitigation effect of full length FGF2 on acute radiation syndrome. Benefits of developing a similar FGF7 biomimetic peptide include lower likelihood of inflammation, longer shelf life, higher purity, and lower cost than the full-length protein.

Methods: Based on the 3-dimensional structure of FGF2 peptide, a corresponding FGF7 peptide (FGF7p) consisting of 19 amino acids was identified and synthesized. FGF7p or vehicle was given subcutaneously (SQ) to female mice subjected to sham injury, intraperitoneal (IP) CPP or external beam radiation over the bladder. One day after injury, bladders were harvested. Slides with paraffin embedded tissues underwent H&E staining, TUNEL and immunofluorescence (IF) assays.

Results: In uninjured control mice, a 20 mg/kg threshold dose of FGF7p induced expression of phosphorylated (activated) FRS2a (pFRS2a) and pAKT in urothelium (consistent with cytoprotective effects of FGF7, albeit at a 4x higher dose than full length FGF7). Unexpectedly, FGF7p activation of urothelial FRS2a and AKT was delayed 24 hours compared to FGF7. FGF7p (20 mg/kg) or vehicle was given at 72 and 48 hours prior to CPP (150 mg/kg). One day after CPP, TUNEL staining revealed an increase in apoptotic and sloughing urothelial cells in vehicle-treated mice compared to in FGF7p-treated mice. IF for pAKT and its targets, pS6K and pBAD, revealed minimal staining in vehicle-treated mice, but strong urothelial staining for all protective markers in FGF7p-treated mice. Using the same dosing strategy, we subjected anesthetized mice to 10 Gy radiation over the bladder. One day after injury, TUNEL staining revealed many more apoptotic urothelial nuclei in control mice, than in FGF7p-treated mice.

Conclusions: FGF7p appears to block bladder urothelial apoptosis via AKT and its targets, in a similar manner to FGF7. FGF7p is 200x less expensive to make vs. FGF7 and is likely to work via direct bladder infusion (avoiding systemic side effects) due to its small size. Our future studies will clarify long term benefits of FGF7p and assess effectiveness of direct bladder infusion.

Citation Format: Sridhar Narla, Lori P. Rice, David Ostrov, Steven G. Swarts, Dietmar W. Siemann, Carlton M. Bates. FGF7 peptide (FGF7p) mimetic mitigates urothelial injury from cyclophosphamide or radiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5431.