Title:Synthesis and Antitumor Evaluation of Glutathione Responsive Self-Immolative
Disulphide Linked Camptothecin-Biotin Conjugate
Volume: 22
Issue: 18
Author(s): Amardeep Kaur, Shikha Dhiman, Hong Boon Lee and Manu Sharma*
Affiliation:
- Department of Pharmacy, M.M. College of Pharmacy, M.M. Deemed to be University, Mullana-133207 Haryana India
Keywords:
Camptothecin, biotin, disulphide linker, glutathione, antitumor, biotinylation.
Abstract:
Background: Camptothecin is a naturally occurring alkaloid obtained from the stem wood of the Chinese
tree, Camptotheca acuminata. It exerts pharmacological effects due to its ability to selectively inhibit the type-I topoisomerase
DNA nuclear enzyme. Several semisynthetic analogs of camptothecin have been synthesized to date possessing
antitumor activity.
Objective: Camptothecin (CPT) is one of the most promising anticancer drugs but it produces various side effects
because of its non-selectivity towards cancer cells. To overcome these adverse effects, we synthesized biotin conjugate
of camptothecin, which was linked via a self-immolative disulfide linker (CPT-SS-Biotin).
Methods: Biotin conjugated camptothecin linked through a disulfide bond was synthesized following schemes, and the
structural characterization was carried out. The stability and drug release studies were performed in the presence of
glutathione (GSH) while in vitro studies were performed on 4T1 tumor cell lines. In vivo pharmacological investigation
was done using an antitumor Wistar rat model.
Results: The stability and drug release studies were performed in the presence of glutathione (GSH), and CPT-SSBiotin
was found to be physiologically stable moiety and can only be cleaved in the presence of GSH to release free
CPT. The CPT-SS-Biotin showed higher toxicity in the biotin-overexpressing 4T1 tumor cell line with a lower IC50
value (8.44 μM) compared to camptothecin alone (IC50 > 30 μM). CPT-SS-Biotin also showed 10.6% higher cellular
uptake by cells in comparison to free camptothecin. The CPT-SS-Biotin was delivered to cells by binding to the biotin
receptors on the cell surface, followed by energy-dependent endocytosis and internalization to cause cellular toxicity.
Conclusion: In-vivo tumor suppression studies and in vitro cell line studies along with serological parameters and
histopathological studies showed that conjugate produced a high therapeutic effect and remarkably reduced toxic effects
in comparison to free CPT. The results suggested that biotinylation of camptothecin via disulfide linker can be a
safe and efficacious method in cancer therapeutics.