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Chemical synthesis and biological activity of a novel fluorescent etoposide derivative
1Department of Pharmacology, University of Pittsburgh, PA 15261, USA. lazo@pop.pitt.edu or yalowich+@pitt.edu
Abstract:
The antineoplastic activity of etoposide resides in its ability to poison the nuclear enzyme DNA topoisomerase II (topo II). The factors that control the cellular entry and subcellular distribution of etoposide remain poorly understood. Therefore, we have synthesized a novel fluorescence-labeled etoposide (Bodipyetoposide) by coupling 4,4-difluoro-5,7-dimethyl-4-bora-3a, 4a-diaza-s-indacene-3-propionylethylenediamine (Bodipy) to 4'-benzyloxycarbonyl-4'-demethylepipodophyllotoxin beta-D-glucopyranoside, a precursor of etoposide. Bodipy-etoposide retained the ability to stabilize topo II-DNA covalent complexes in isolated nuclei, although it was significantly less potent and efficacious than etoposide. The growth inhibitory activity of Bodipy-etoposide was also approximately 200-fold less than that of etoposide in human leukemia K562 and DU-145 prostatic carcinoma cells. Nonetheless, etoposide-resistant K/VP.5 and K/VP.5-1 leukemia cells were cross-resistant to Bodipy-etoposide compared with parental K562 cells. Analysis by flow cytometry revealed a concentration-dependent Bodipy-etoposide cell association with no significant difference in drug association in the etoposide-resistant cell lines relative to the parental K562 cells. Using confocal laser scanning microscopy, we found significant cytoplasmic perinuclear localization of Bodipy-etoposide. Thus, Bodipy-etoposide displays promise as a tool to probe the factors controlling entry and subcellular distribution of etoposide-like compounds in live cells.
Insights
Researchers developed a fluorescent etoposide (Bodipy-etoposide) to study drug entry and distribution. While less potent, it showed similar resistance patterns and cellular uptake in resistant cells, aiding research into etoposide-like compounds.
Area of Science:
- Pharmacology and Molecular Biology
- Cancer Therapeutics
- Drug Delivery and Cellular Uptake
Background:
- Etoposide is an antineoplastic drug that functions by inhibiting DNA topoisomerase II (topo II).
- The mechanisms governing etoposide's cellular entry and subcellular localization are not fully understood.
- Understanding these factors is crucial for optimizing etoposide's therapeutic efficacy and overcoming resistance.
Purpose of the Study:
- To synthesize a novel fluorescently labeled etoposide analog, Bodipy-etoposide, for studying drug disposition.
- To investigate the cellular uptake, subcellular distribution, and activity of Bodipy-etoposide in cancer cells.
- To assess the utility of Bodipy-etoposide as a tool for probing etoposide-like compound behavior in live cells.
Main Methods:
- Synthesis of Bodipy-etoposide by conjugating a Bodipy fluorophore to an etoposide precursor.
- Assessment of Bodipy-etoposide's ability to stabilize topo II-DNA complexes in isolated nuclei.
- Evaluation of growth inhibitory activity in human leukemia (K562) and prostate carcinoma (DU-145) cells.
- Analysis of cellular association and subcellular localization using flow cytometry and confocal laser scanning microscopy.
- Comparison of Bodipy-etoposide activity and uptake in etoposide-sensitive and etoposide-resistant cell lines.
Main Results:
- Bodipy-etoposide retained the ability to stabilize topo II-DNA complexes but was less potent and efficacious than etoposide.
- Growth inhibition by Bodipy-etoposide was approximately 200-fold less than etoposide in tested cell lines.
- Etoposide-resistant leukemia cells exhibited cross-resistance to Bodipy-etoposide.
- Flow cytometry showed concentration-dependent Bodipy-etoposide cell association, with no significant difference between resistant and sensitive cells.
- Confocal microscopy revealed significant cytoplasmic perinuclear localization of Bodipy-etoposide.
Conclusions:
- Bodipy-etoposide serves as a valuable fluorescent probe for investigating the cellular entry and subcellular distribution of etoposide.
- The drug exhibits reduced potency but maintains cross-resistance patterns observed with etoposide.
- The findings suggest that Bodipy-etoposide can be used to study the disposition of etoposide-like compounds in live cellular models.