Related Experiment Video
Updated: Sep 23, 2025
In Vitro Imaging and Quantification of the Drug Targeting Efficiency of Fluorescently Labeled GnRH Analogues
Published on: March 21, 2017
Development and Biochemical Characterization of Self-Immolative Linker Containing GnRH-III-Drug Conjugates
Sabine Schuster1,2, Éva Juhász3, Gábor Halmos4
1Faculty of Science, Institute of Chemistry, Eötvös Loránd University, 1117 Budapest, Hungary.
Abstract:
The human gonadotropin releasing hormone (GnRH-I) and its sea lamprey analogue GnRH-III specifically bind to GnRH receptors on cancer cells and can be used as targeting moieties for targeted tumor therapy. Considering that the selective release of drugs in cancer cells is of high relevance, we were encouraged to develop cleavable, self-immolative GnRH-III-drug conjugates which consist of a p-aminobenzyloxycarbonlyl (PABC) spacer between a cathepsin B-cleavable dipeptide (Val-Ala, Val-Cit) and the classical anticancer drugs daunorubicin (Dau) and paclitaxel (PTX). Alongside these compounds, non-cleavable GnRH-III-drug conjugates were also synthesized, and all compounds were analyzed for their antiproliferative activity. The cleavable GnRH-III bioconjugates revealed a growth inhibitory effect on GnRH receptor-expressing A2780 ovarian cancer cells, while their activity was reduced on Panc-1 pancreatic cancer cells exhibiting a lower GnRH receptor level. Moreover, the antiproliferative activity of the non-cleavable counterparts was strongly reduced. Additionally, the efficient cleavage of the Val-Ala linker and the subsequent release of the drugs could be verified by lysosomal degradation studies, while radioligand binding studies ensured that the GnRH-III-drug conjugates bound to the GnRH receptor with high affinity. Our results underline the high value of GnRH-III-based homing devices and the application of cathepsin B-cleavable linker systems for the development of small molecule drug conjugates (SMDCs).
Insights
New GnRH-III drug conjugates show promise for targeted cancer therapy. Cleavable linkers enable selective drug release in cancer cells, enhancing efficacy for ovarian cancer treatment.
Area of Science:
- Bioconjugate Chemistry
- Oncology
- Pharmacology
Background:
- Human gonadotropin-releasing hormone (GnRH-I) and GnRH-III target GnRH receptors on cancer cells for therapy.
- Selective drug release within cancer cells is crucial for effective targeted tumor therapy.
Purpose of the Study:
- To develop and evaluate cleavable, self-immolative GnRH-III-drug conjugates for targeted cancer therapy.
- To assess the antiproliferative activity and drug release mechanisms of novel GnRH-III bioconjugates.
Main Methods:
- Synthesis of cleavable and non-cleavable GnRH-III-drug conjugates using PABC spacers and cathepsin B-cleavable dipeptides.
- Antiproliferative activity assays on A2780 ovarian and Panc-1 pancreatic cancer cell lines.
- Lysosomal degradation studies to confirm drug release and radioligand binding assays to assess GnRH receptor affinity.
Main Results:
- Cleavable GnRH-III bioconjugates demonstrated significant growth inhibition in GnRH receptor-positive A2780 ovarian cancer cells.
- Reduced activity was observed in Panc-1 cells with lower GnRH receptor expression, and non-cleavable conjugates showed diminished antiproliferative effects.
- Efficient cleavage of the linker and drug release were confirmed, with conjugates maintaining high affinity for GnRH receptors.
Conclusions:
- GnRH-III serves as an effective homing device for targeted drug delivery.
- Cathepsin B-cleavable linkers are valuable for developing small molecule drug conjugates (SMDCs) with enhanced therapeutic potential.
