Micellar electrokinetic capillary chromatography reveals differences in intracellular metabolism between liposomal and free doxorubicin treatment of human leukemia cells

Quantitative subcellular study of transferrin receptor-targeted doxorubicin and its metabolite in human breast cancer cells

The extended use of doxorubicin (DOX) could be limited due to the emergence of drug resistance and cardiotoxicity associated with its treatment. Conjugates of DOX with transferrin (DOX-TRF) can effectively alleviate these side effects, thereby leading to a better treatment. The effectiveness of DOX-TRF could result from the enhancement of transferrin receptor (TfR)-mediated transportation. However, detailed TfR-mediated DOX delivery has not been fully elucidated thus far, which may rely on the quantitative subcellular study of DOX distribution and metabolism. In this study, an immunoisolation assay was developed to isolate the organelles with high purity, yield and integrity. Using this immunoisolation assay together with liquid chromatography-tandem mass spectrometry (LC/MS/MS), the subcellular distribution profiles of DOX and its main metabolite doxorubicinol (DOXol) in human breast cancer cells MCF-7/WT and MCF-7/ADR were determined and compared after the treatment of DOX and DOX-TRF. As expected, DOX-TRF treated cells have a higher drug accumulation compared to DOX treated cells. DOX-TRF was predominantly cytoplasmic. In addition, TfR-mediated transportation had a significant impact on the transformation of DOX to DOXol in the cells. This study provided the evidence that immunoisolation together with LC/MS/MS is an effective technique in subcellular investigations.

Direct sampling from human liver tissue cross sections for electrophoretic analysis of doxorubicin

After chemoembolization of the liver with doxorubicin (Dox), this drug and its metabolites are not homogeneously distributed in this organ. The distribution cannot be easily measured making it difficult to assess how the drug performs in different tissue regions. Here we report a technique for sampling tissue cross sections that can analyze the contents of micrometer size regions. The tissue cross sections were from the explanted liver of a hepatocellular carcinoma patient. Samples were directly aspirated from a 5 microm thick tissue cross section into a 50 microm i.d. capillary where the tissue was solubilized with a separation buffer containing sodium dodecyl sulfate. Upon sample dissolution, Dox and natively fluorescent compounds were separated and detected by micellar electrokinetic chromatography with laser-induced fluorescence detection. Sampling reproducibility and recovery were assessed using 10% (w/v) gelatin as tissue mimic. Sampling from gelatin slices containing Dox revealed a relative standard deviation of 13%, which was comparable to that of sampling from solution. Dox recovery was 82% +/- 16% (n = 5). When sampling tumor and nontumor tissue regions, samples could be taken from the same region 100 microm apart. Atomic force microscopy was used to determine that each sample was 8.4 +/- 1.0 pL in volume which made it possible to determine Dox concentrations in the ranges of 0.4-1.3 and 0.3-0.5 microM for the samples taken from tumor and nontumor regions, respectively. The results demonstrated the feasibility of sampling, detection, and quantification of Dox in micrometer size regions, which could be a useful resource for analyzing the Dox concentration and distribution in highly heterogeneous tissues.

Monitoring incorporation, transformation and subcellular distribution of N-l-leucyl-doxorubicin in uterine sarcoma cells using capillary electrophoretic techniques

Previous reports have demonstrated that N-l-leucyl-doxorubicin (LeuDox) is less toxic than its parent drug, Dox, but the underlying causes of this reduced toxicity have yet to be fully elucidated. In this study, the incorporation of LeuDox into (i) the MES-SA human uterine sarcoma cell line and (ii) its Dox resistant counterpart, MES-SA/Dx5 cell line and the subsequent transformation of LeuDox into Dox and its subcellular distribution, were investigated by micellar electrokinetic chromatography with laser-induced fluorescence detection (MEKC-LIF). In both cell lines the cellular uptakes of Dox and LeuDox were similar at equimolar doses, while the percent transformation of LeuDox into Dox in MES-SA/Dx5 cells was about twice as great as its transformation in MES-SA cells, which is beneficial for reaching Dox cytotoxic levels in this resistant cell line. When both cells lines were treated with IC(35) concentrations of either Dox and LeuDox, the intracellular Dox amounts were 6-fold higher in the resistant cell line than in the sensitive cell line, suggesting that other cellular processes play a role in the cytotoxicity of Dox in the resistant cell line. The amounts and ratios of Dox and LeuDox in four subcellular fractions of LeuDox-treated MES-SA/Dx5 cells were also investigated. The highest Dox/LeuDox ratio (i.e. 2.92) was found in the nuclear fraction, followed by the ratio in the low density organelle fraction (i.e. 1.92) that contains lysosomes, organelles in which lysosomal hydrolytic enzymes, capthesins, transform LeuDox into Dox.

Separation of doxorubicin and doxorubicinol by cyclodextrin-modified micellar electrokinetic capillary chromatography

Doxorubicinol (DOXol) is a human metabolite of the chemotherapy agent doxorubicin (DOX), and is associated with dose-dependent cardiotoxicity and decreased drug efficacy. Due to the structural similarities and equal molecular charges of DOXol and DOX, their electrophoretic separation is commonly ineffective. A method for separating and detecting DOX and DOXol, as well as two DOXol enantiomers, was established using cyclodextrin-modified micellar electrokinetic capillary chromatography with laser-induced fluorescence detection. Differential DOXol production was detected in a DOX-sensitive and resistant pair of cell lines, with a 0.08 +/- 0.01 fmol limit of detection.