# Preparation and Characterization of an Engineered FGF1 Conjugated to 161Tb for Targeting of FGFRs

## TL;DR

This paper describes a new cancer therapy approach using an engineered FGF1 protein linked to a radioactive isotope to target cancer cells overexpressing FGFRs.

## Contribution

The novel contribution is the development of an engineered FGF1 conjugated with 161Tb for targeted FGFR-based cancer therapy.

## Key findings

- eFGF1-DOTA-Tb[161Tb] showed high labeling efficiency and targeted FGFR-overexpressing cancer cells effectively.
- The radioligand caused enhanced cytotoxicity in FGFR-overexpressing cell lines compared to low FGFR-expressing cells.
- eFGF1 can also deliver doxorubicin into cancer cells, suggesting dual therapeutic potential.

## Abstract

The fibroblast growth factor receptor family members,
FGFR1-4,
are frequently overexpressed in various solid tumors, including breast
cancer and sarcomas. This overexpression highlights the potential
of the family of FGFRs as promising targets for cancer therapy. However,
conventional FGFR kinase inhibitors often encounter challenges such
as limited efficacy or drug resistance. In this study, we pursue an
alternative strategy by designing a conjugate of the FGFR ligand FGF1
with the radioisotope 161Tb, for targeted therapy in FGFR-overexpressing
cancer cells. FGF1 was engineered (eFGF1) to incorporate a single
cysteine at the C terminus for site-specific labeling with a DOTA
chelator. eFGF1-DOTA was mixed with the radioisotope 161Tb under mild conditions, resulting in a labeling efficiency above
90%. The nonradioactive ligands were characterized by mass spectrometry,
while radioligands were characterized by thin-layer chromatography.
The targeting function of the radioligands was assessed through confocal
microscopy, flow cytometry, and Western blot analysis, focusing on
binding to cancer cells and the activation of downstream signaling
pathways related to FGFR. When compared to MCF-7 and RD cell lines
with low FGFR expression, eFGF1-DOTA-Tb[161Tb] radioligands
demonstrated significantly higher accumulation in FGFR-overexpressing
cell lines (MCF-7 FGFR1 and RMS559), leading to enhanced cytotoxicity.
Besides radionuclides, eFGF1 can also deliver doxorubicin (DOX) into
cancer cells. Considering these characteristics, eFGF1-DOTA-Tb[161Tb] and eFGF1-DOX emerge as promising candidates for FGFR-targeted
cancer therapy, and further evaluation in vivo is warranted.