Doxorubicin is an effective drug in the treatment of solid tumors as well as leukemia. However, the use of the drug results in toxic side effects such as cumulative cardiotoxicity. In order to increase the efficacy of this drug treatment or reduce toxic side effects, it is necessary to understand the fate of the drug after it enters into a cell. The current goals are to develop techniques to analyze the drug metabolism on a subcellular level and to examine different aspects, which might modify the drugs efficacy such as drug formulation (liposomal formulation and prodrugs) or the presence of p-glycoprotein.

Fluorescence microscopy is used to visualize doxorubicin within the cell and correlate its location with that of p-glycoprotein. This protein is believed to be responsible for some cells’ resistance to doxorubicin. The presence of p-glycoprotein is being correlated with the IC50 values for various cell lines in order to substantiate this claim.

Fluorescence microscopy would be an ideal technique in determining the subcellular distribution of doxorubicin. However, the quantum yield and spectral profile of doxorubicin is highly dependant on its surrounding environment. Therefore, a single calibration is not adequate for the determination of doxorubicin content within subcellular fractions or even the entire cell. Work is being conducted to collect spectra from doxorubicin in micro-environments.

The common method of analysis of doxorubicin metabolism has been capillary electrophoresis with laser induced fluorescence (CE-LIF) in this lab. This technique has been used to analyze the metabolism of doxorubicin, a liposomal formulation of doxorubicin and will be used to examine prodrugs (an oligopeptide attached to the drug to increase specificity to cancerous cells) of doxorubicin. These analyses will then be compared to determine differences in the metabolism of different drug formulations.

While CE-LIF provides a timely separation with a very low limit of detection, it cannot aid in the identification of unknown and commercially unavailable metabolic products. High performance liquid chromatography is being used for separation and identification purposes due to its ability to be more easily coupled with a mass spectrometer. Using these and other developed techniques it is hoped that more understanding of doxorubicin and other anti-tumor agents will arise.

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Doxorubicin Content in Acidic Organelles